WO2018026148A1

WO2018026148A1 - Image encoding/decoding method and device, and recording medium storing bitstream

Info

Publication number: WO2018026148A1
Application number: PCT/KR2017/008221
Authority: WO
Inventors: 고현석; 강정원; 이진호; 이하현; 임성창; 전동산; 조승현; 김휘용; 최진수
Original assignee: 한국전자통신연구원
Priority date: 2016-08-01
Filing date: 2017-07-31
Publication date: 2018-02-08
Also published as: KR102435675B1; CN109792515B; KR20180014674A; CN117201808A; CN109792515A; CN117201809A; CN117201807A

Abstract

The present invention relates to an image encoding/decoding method and device. An image decoding method for performing an intra-frame prediction for a current block, according to the present invention, may comprise the steps of: decoding first information indicating whether a residual signal prediction for predicting a residual block of the current block is performed; and performing the residual signal prediction when the first information indicates a first value.

Description

Image encoding / decoding method, apparatus and recording medium storing bitstream

The present invention relates to a method and apparatus for image encoding / decoding. Specifically, the present invention relates to a video encoding / decoding method and apparatus using intra picture prediction, and a recording medium storing a bitstream generated by the video encoding method / apparatus of the present invention.

Recently, the demand for high resolution and high quality images such as high definition (HD) and ultra high definition (UHD) images is increasing in various applications. As the video data becomes higher resolution and higher quality, the amount of data increases relative to the existing video data. Therefore, when the video data is transmitted or stored using a medium such as a conventional wired / wireless broadband line, The storage cost will increase. In order to solve these problems caused by high resolution and high quality image data, a high efficiency image encoding / decoding technique for an image having a higher resolution and image quality is required.

An inter-screen prediction technique for predicting pixel values included in the current picture from a picture before or after the current picture using an image compression technology, an intra-picture prediction technology for predicting pixel values included in the current picture using pixel information in the current picture, There are various techniques such as transformation and quantization techniques for compressing the energy of the residual signal, entropy coding technique for assigning short codes to high-frequency values and long codes for low-frequency values. Image data can be effectively compressed and transmitted or stored.

An object of the present invention is to provide a video encoding / decoding method and apparatus having improved compression efficiency, and a recording medium storing a bitstream generated by the video encoding method / apparatus of the present invention.

Another object of the present invention is to provide a video encoding / decoding method and apparatus using intra picture prediction with improved compression efficiency, and a recording medium storing a bitstream generated by the video encoding method and apparatus of the present invention.

In addition, an object of the present invention is to provide a video image encoding / decoding method, apparatus for performing intra prediction using residual signal prediction, and a recording medium storing a bitstream generated by the video encoding method / apparatus of the present invention. do.

An image decoding method for performing intra prediction on a current block according to the present invention includes: decoding first information indicating whether residual signal prediction for predicting a residual block of the current block is performed; If the first information indicates a first value, the method may include performing the residual signal prediction.

In the image decoding method of the present invention, the residual signal prediction may be performed based on a decoded reconstruction block.

The image decoding method of the present invention further includes decoding an IDV (Inta Displacement Vector), and the decoded reconstruction block may be specified by the decoded IDV.

The image decoding method of the present invention may further include decoding an intra prediction mode used for the residual signal prediction, and generating a prediction block of the reconstructed block based on the decoded intra prediction mode. Can be.

The image decoding method of the present invention further includes generating a residual block of the reconstructed block based on the reconstructed block and the prediction block of the reconstructed block, wherein the residual block of the reconstructed block is a residual block of the current block. It may be a prediction block of.

The image decoding method of the present invention may further include decoding a secondary residual block of the current block, and generating a residual block of the current block based on the prediction block and the secondary residual block of the residual block of the current block. It may further comprise a step.

In the video decoding method of the present invention, when the information on the IDV is not included in the bitstream, the decoding of the IDV may be performed by using a predetermined search method, among a plurality of IDVs included in the predetermined search range. This can be done by selecting one.

In the video decoding method of the present invention, the predetermined search method may be the same search method used in the video encoding method.

An image decoding apparatus including an intra picture prediction unit that performs an intra picture prediction on a current block according to the present invention, decodes first information indicating whether residual signal prediction for predicting a residual block of the current block is performed. When the first information indicates the first value, the first information may include an intra prediction unit configured to perform the residual signal prediction.

An image encoding method for performing intra prediction on a current block according to the present invention may include performing residual signal prediction for predicting a residual block of the current block, and indicating whether the residual signal prediction is performed. 1 may include encoding the information.

In the image encoding method of the present invention, the residual signal prediction may be performed based on a decoded reconstruction block.

The image encoding method of the present invention may further include encoding an IDV (Inta Displacement Vector) that specifies the decoded reconstruction block.

The image encoding method of the present invention may include determining an intra prediction mode used for the residual signal prediction, generating a prediction block of the reconstructed block based on the determined intra prediction mode, and determining the intra intra prediction mode. The method may further include encoding the prediction mode.

In the image encoding method of the present invention, the predetermined search method may include comparing a cost function value of a residual block of the current block with a cost function value of a secondary residual block of the current block.

An image encoding apparatus including an intra picture prediction unit that performs an intra picture prediction on a current block according to the present invention, performs a residual signal prediction for predicting a residual block of the current block, and determines whether the residual signal prediction is performed. It may include an intra prediction unit for encoding the first information indicating the.

A recording medium storing a bitstream generated by an image encoding method for performing intra prediction on a current block according to the present invention, the method comprising: performing a residual signal prediction for predicting a residual block of the current block; and A bitstream generated by an image encoding method may include storing first information indicating whether residual signal prediction is performed.

According to the present invention, there can be provided a video encoding / decoding method and apparatus having improved compression efficiency, and a recording medium storing a bitstream generated by the video encoding method / device of the present invention.

According to the present invention, there can be provided a video encoding / decoding method and apparatus using intra picture prediction with improved compression efficiency, and a recording medium storing a bitstream generated by the video encoding method / device of the present invention.

Further, according to the present invention, there can be provided a video image encoding / decoding method, apparatus for performing intra prediction using residual signal prediction, and a recording medium storing a bitstream generated by the video encoding method / device of the present invention. have.

1 is a block diagram illustrating a configuration of an encoding apparatus according to an embodiment of the present invention.

2 is a block diagram illustrating a configuration of a decoding apparatus according to an embodiment of the present invention.

3 is a diagram schematically illustrating a division structure of an image when encoding and decoding an image.

FIG. 4 is a diagram illustrating a form of a prediction unit PU that may be included in the coding unit CU.

FIG. 5 is a diagram illustrating a form of a transform unit (TU) that a coding unit CU may include.

6 is a diagram for explaining an embodiment of an intra prediction process.

7 is a diagram for explaining an embodiment of an inter prediction process.

8 is a diagram for describing a transform set according to an intra prediction mode.

9 is a view for explaining the process of the conversion.

10 is a diagram for describing scanning of quantized transform coefficients.

11 is a diagram for explaining block division.

12 is a diagram for describing a method of performing intra prediction on a current block according to an embodiment of the present invention.

FIG. 13 is a diagram for describing a method of deriving an intra prediction mode of a current block from a neighboring block.

14 is an exemplary diagram for describing a current block, an upper block, and an adjacent block.

15 is an exemplary diagram illustrating a luminance block and a color difference block when the ratio between color components is 4: 2: 0.

FIG. 16 is a diagram for describing an embodiment in which a current block is divided into one or more subblocks to derive an intra prediction mode of each subblock.

FIG. 17 is a diagram illustrating an embodiment in which a current block is divided into sub blocks.

18 illustrates another embodiment in which a current block is divided into sub blocks.

19 illustrates another embodiment in which a current block is divided into subblocks.

20 is a diagram illustrating another embodiment in which a current block is divided into sub blocks.

FIG. 21 is a diagram illustrating an example of deriving an intra prediction mode of a current block by using an intra prediction mode.

FIG. 22 is a diagram illustrating an embodiment of constructing a SPIPM list including two SPIPMs.

FIG. 23 is a diagram illustrating an embodiment of configuring a SPIPM list including three SPIPMs.

FIG. 24 is a diagram illustrating an embodiment of constructing a SPIPM list including four SPIPMs.

FIG. 25 is a diagram exemplarily illustrating a size of a sub block when the size of a current block is 16 × 16.

FIG. 26 illustrates an example of allocating an intra prediction mode using the determined IPDF.

27 is a diagram exemplarily illustrating adjacent reconstructed blocks of a current block.

FIG. 28 is a diagram for describing an embodiment of deriving an intra prediction mode using adjacent reconstruction blocks.

FIG. 29 is a diagram for describing an embodiment of deriving an intra prediction mode on a sub-block basis.

FIG. 30 is a diagram for describing another embodiment of deriving an intra prediction mode on a sub-block basis.

31 is a diagram illustrating a syntax structure including information about an intra prediction mode.

32 is a diagram illustrating surrounding reconstructed sample lines that may be used for in-picture prediction of a current block.

33 is a diagram for describing an embodiment of configuring a reference sample for a subblock included in a current block.

FIG. 34 is a diagram for describing a method of replacing an unavailable restoration sample by using an available restoration sample.

35 is a diagram illustrating a threshold for each block size for determining whether to filter.

36 is a diagram exemplarily illustrating whether filtering is performed according to a block size and / or an intra prediction mode.

37 is an exemplary diagram for describing intra prediction according to a shape of a current block.

FIG. 38 is a diagram for describing filtering during intra prediction in a DC mode. FIG.

39 is a diagram for describing intra prediction in a planar mode.

40 is a view for explaining one embodiment of generating a one-dimensional array (1-D reference sample array, p 1, ref) of the reference sample from P _ref.

FIG. 41 is a view for explaining an embodiment using reference samples of different angles according to sample positions in a prediction block.

42 is a diagram illustrating a prediction from the upper right to the lower left by applying cuv = 0.1, cw ₀ = 1.0, cw ₁ = 1.2, cw ₂ = 1.4, and cw ₃ = 1.6 for a current block having a size of 4x4. It is a figure for demonstrating an example.

FIG. 43 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 42.

44 shows the prediction from the upper left to the lower right direction (type-1) by applying cuv = 0.1, cw ₀ = 1.0, cw ₁ = 1.2, cw ₂ = 1.4, and cw ₃ = 1.6 for the current block having a size of 4x4. A diagram for describing an embodiment of performing the present invention.

FIG. 45 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 44.

FIG. 46 illustrates an embodiment of performing prediction from the lower left to the upper right by applying cuv = 0.1, cw0 = 1.0, cw1 = 1.2, cw2 = 1.4, and cw3 = 1.6 for a current block having a size of 4x4. It is for the drawing.

FIG. 47 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 46.

FIG. 48 illustrates the prediction from the upper left to the lower right (type-2) directions by applying cuv = 0.1, cw0 = 1.0, cw1 = 1.2, cw2 = 1.4, and cw3 = 1.6 for a 4 × 4 current block. It is a figure for demonstrating an Example.

FIG. 49 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 48.

FIG. 50 illustrates an embodiment of performing prediction from the top to the bottom left by applying cuv = 0.6, cw0 = 1.0, cw1 = 1.4, cw2 = 1.8, and cw3 = 2.2 for a 4 × 4 current block. It is for the drawing.

FIG. 51 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 50.

52 is a diagram for describing an embodiment of performing prediction from the top to the bottom right by applying cuv = 0.6, cw0 = 1.0, cw1 = 1.4, cw2 = 1.8, and cw3 = 2.2 for a current block having a size of 4x4. It is for the drawing.

FIG. 53 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 52.

FIG. 54 is a diagram for explaining an embodiment of performing prediction from the left to the upper right direction by applying cuv = 0.6 cw0 = 1.0, cw1 = 1.4, cw2 = 1.8, and cw3 = 2.2 to a 4 × 4 current block. to be.

FIG. 55 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 54.

56 illustrates an embodiment of performing prediction from left to right bottom by applying cuv = 0.6, cw0 = 1.0, cw1 = 1.4, cw2 = 1.8, and cw3 = 2.2 for a 4 × 4 current block. It is for the drawing.

FIG. 57 is a diagram illustrating an embodiment of a position of a reference pixel used by a prediction pixel in a current block as a result of applying cuv and cw _i of FIG. 56.

FIG. 58 illustrates another embodiment using different directional modes in units of samples in a target block.

59 is a view for explaining an embodiment of predicting a residual signal.

60 is a diagram for explaining prediction of a residual signal using a secondary residual signal block.

61 is a diagram to describe an embodiment of a residual signal prediction.

62 is a diagram for explaining an embodiment of performing a residual signal prediction in an encoder.

63 is a diagram for explaining an embodiment of performing residual signal prediction in a decoder.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects. Shape and size of the elements in the drawings may be exaggerated for clarity. DETAILED DESCRIPTION For the following detailed description of exemplary embodiments, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that the various embodiments are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiments. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the exemplary embodiments, if properly described, is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

In the present invention, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When any component of the invention is said to be “connected” or “connected” to another component, it may be directly connected to or connected to that other component, but other components may be present in between. It should be understood that it may. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that each component is made of separate hardware or one software component unit. In other words, each component is included in each component for convenience of description, and at least two of the components may be combined into one component, or one component may be divided into a plurality of components to perform a function. Integrated and separate embodiments of the components are also included within the scope of the present invention without departing from the spirit of the invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present invention, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof. In other words, the description "include" a specific configuration in the present invention does not exclude a configuration other than the configuration, it means that additional configuration may be included in the scope of the technical spirit of the present invention or the present invention.

Some components of the present invention are not essential components for performing essential functions in the present invention but may be optional components for improving performance. The present invention can be implemented including only the components essential for implementing the essentials of the present invention except for the components used for improving performance, and the structure including only the essential components except for the optional components used for improving performance. Also included in the scope of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to drawings. In describing the embodiments of the present specification, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the detailed description is omitted and the same reference numerals are used for the same elements in the drawings. Duplicate descriptions of the same components are omitted.

Also, hereinafter, an image may mean one picture constituting a video and may represent a video itself. For example, "encoding and / or decoding of an image" may mean "encoding and / or decoding of a video" and may mean "encoding and / or decoding of one of images constituting the video." It may be. Here, the picture may have the same meaning as the image.

Term description

Encoder: This may mean an apparatus for performing encoding.

Decoder: Refers to an apparatus for performing decoding.

Parsing: This may mean determining a value of a syntax element by entropy decoding or may refer to entropy decoding itself.

Block: An MxN array of samples, where M and N are positive integer values, and a block can often mean a two-dimensional sample array.

Sample: This is a basic unit that constitutes a block and can represent values from 0 to 2 ^Bd -1 depending on the bit depth (B _d ). In the present invention, the pixel and the pixel may be used as the sample.

Unit: may mean a unit of image encoding and decoding. In encoding and decoding of an image, a unit may be an area generated by division of one image. In addition, a unit may mean a divided unit when a single image is divided into subdivided units to be encoded or decoded. In encoding and decoding of an image, a predetermined process may be performed for each unit. One unit may be further divided into subunits having a smaller size than the unit. Depending on the function, the unit may be a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding block, a prediction. It may mean a unit, a prediction block, a transform unit, a transform block, or the like. In addition, the unit may refer to a luma component block, a chroma component block corresponding thereto, and a syntax element for each block in order to refer to the block separately. The unit may have various sizes and shapes, and in particular, the shape of the unit may include a geometric figure that can be expressed in two dimensions such as a square, a trapezoid, a triangle, a pentagon, as well as a rectangle. In addition, the unit information may include at least one of a type of a unit indicating a coding unit, a prediction unit, a transformation unit, and the like, a size of a unit, a depth of a unit, an encoding and decoding order of the unit, and the like.

Reconstructed Neighbor Unit: A reconstructed neighbor unit may refer to a unit that has already been encoded or decoded in a spatial / temporal manner around the encoding / decoding target unit. In this case, the restored peripheral unit may mean a restored peripheral block.

Neighbor block: A neighbor block may mean a block adjacent to an encoding / decoding target block. The block adjacent to the encoding / decoding object block may mean a block in which a boundary of the encoding / decoding object block abuts. The neighboring block may mean a block located at an adjacent vertex of the encoding / decoding target block. The neighboring block may mean a restored neighboring block.

Unit Depth: It means the degree of unit division. In the tree structure, the root node has the smallest depth, and the leaf node has the deepest depth.

Symbol: This may mean a encoding / decoding target unit syntax element, a coding parameter, a value of a transform coefficient, or the like.

Parameter set: may correspond to header information among structures in the bitstream, and includes a video parameter set, a sequence parameter set, a picture parameter set, and an adaptive parameter set. At least one or more of the adaptation parameter set may be included in the parameter set. In addition, the parameter set may have a meaning including slice header and tile header information.

Bitstream: A bitstream may mean a string of bits including encoded image information.

Prediction Unit: This is a basic unit when performing inter prediction or intra prediction and compensation thereof, and one prediction unit may be divided into a plurality of partitions having a small size. In this case, each of the plurality of partitions becomes a basic unit at the time of performing the prediction and compensation, and the partition in which the prediction unit is divided may also be called a prediction unit. The prediction unit may have various sizes and shapes, and in particular, the shape of the prediction unit may include a geometric figure that can be expressed in two dimensions such as a square, a trapezoid, a triangle, a pentagon, as well as a rectangle.

Prediction Unit Partition: This may mean a form in which a prediction unit is divided.

Reference Picture List: Refers to a list including one or more reference pictures used for inter prediction or motion compensation. The types of reference picture lists may be LC (List Combined), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3), and the like. Lists can be used.

Inter Prediction Indicator: It may mean the inter prediction direction (unidirectional prediction, bi-directional prediction, etc.) of the block to be encoded / decoded during inter prediction, and the block to be encoded / decoded will generate the prediction block. This may mean the number of reference pictures used, and may mean the number of prediction blocks used when the encoding / decoding target block performs inter prediction or motion compensation.

Reference Picture Index: A reference picture index may mean an index of a specific reference picture in the reference picture list. Here, the index may mean an index.

Reference Picture: Refers to an image referred to by a specific unit for inter prediction or motion compensation. The reference picture may also be referred to as a reference picture.

Motion Vector: A two-dimensional vector used for inter prediction or motion compensation, and may mean an offset between an encoding / decoding target image and a reference image. For example, (mvX, mvY) may represent a motion vector, mvX may represent a horizontal component, and mvY may represent a vertical component.

Motion Vector Candidate: When a motion vector is predicted, it may mean a unit which is a prediction candidate or a motion vector of the unit.

Motion Vector Candidate List: A motion vector candidate list may mean a list constructed using motion vector candidates.

Motion Vector Candidate Index: An indicator indicating a motion vector candidate in a motion vector candidate list, and may be referred to as an index of a motion vector predictor.

Motion Information: Information including at least one of a motion vector, a reference picture index, an inter prediction indicator, as well as reference picture list information, a reference picture, a motion vector candidate, and a motion vector candidate index. It may mean.

Merge Candidate List: A merge candidate list may mean a list constructed using merge candidates.

Merge Candidate: may include a spatial merge candidate, a temporal merge candidate, a combined merge candidate, a combined two-prediction merge candidate, a zero merge candidate, and the like. The merge candidate may include prediction type information and each list. It may include motion information such as a reference picture index and a motion vector.

Merge Index: Refers to information indicating a merge candidate in the merge candidate list. In addition, the merge index may indicate a block in which a merge candidate is derived among blocks reconstructed adjacent to the current block in a spatial / temporal manner. In addition, the merge index may indicate at least one or more of the motion information that the merge candidate has.

Transform Unit: A transform unit may refer to a basic unit when performing residual signal encoding / decoding such as transform, inverse transform, quantization, inverse quantization, and transform coefficient encoding / decoding. It may be divided into a plurality of transform units having a small size. The transform unit may have various sizes and shapes, and in particular, the shape of the transform unit may include a geometric figure that can be expressed in two dimensions such as a square, a trapezoid, a triangle, a pentagon, as well as a rectangle.

Scaling: This may mean a process of multiplying a transform coefficient level by a factor and generating a transform coefficient as a result. Scaling can also be called dequantization.

Quantization Parameter: A quantization parameter may mean a value used when scaling transform coefficient levels in quantization and inverse quantization. In this case, the quantization parameter may be a value mapped to a quantization step size.

Residual Quantization Parameter: A quantization parameter may mean a differential value between the predicted quantization parameter and the quantization parameter of the encoding / decoding target unit.

Scan: Refers to a method of arranging the order of coefficients in a block or matrix. For example, aligning a two-dimensional array into a one-dimensional array is called a scan, and a one-dimensional array into a two-dimensional array. Sorting can also be called scan or inverse scan.

Transform Coefficient: A coefficient value generated after performing a transform, and in the present invention, a quantized transform coefficient level in which quantization is applied to the transform coefficient may also be included in the meaning of the transform coefficient.

Non-zero Transform Coefficient: A non-zero transform coefficient may mean a transform coefficient whose magnitude is not zero or a transform coefficient level whose magnitude is not zero.

Quantization Matrix: A matrix used in a quantization or inverse quantization process to improve the subjective or objective image quality of an image. The quantization matrix may also be called a scaling list.

Quantization Matrix Coefficient: It may mean each element in the quantization matrix. Quantization matrix coefficients may also be referred to as matrix coefficients.

Default Matrix: A predetermined matrix may mean a predetermined quantization matrix defined in the encoder and the decoder.

Non-default Matrix: A non-default matrix, which is not defined in the encoder and the decoder, may be a quantization matrix signaled by a user.

Coding Tree Unit: A coding component may be composed of two color difference component (Cb, Cr) coding tree blocks associated with one luminance component (Y) coding tree block. Each coding tree unit may be split using one or more partitioning methods such as a quad tree and a binary tree to form sub-units such as a coding unit, a prediction unit, and a transform unit. It may be used as a term for a pixel block that becomes a processing unit in a decoding / encoding process of an image, such as splitting an input image.

Coding Tree Block: A term used to refer to any one of a Y coded tree block, a Cb coded tree block, and a Cr coded tree block.

The encoding apparatus 100 may be a video encoding apparatus or an image encoding apparatus. The video may include one or more images. The encoding apparatus 100 may sequentially encode one or more images of the video over time.

Referring to FIG. 1, the encoding apparatus 100 may include a motion predictor 111, a motion compensator 112, an intra predictor 120, a switch 115, a subtractor 125, a transformer 130, and quantization. The unit 140 may include an entropy encoder 150, an inverse quantizer 160, an inverse transform unit 170, an adder 175, a filter unit 180, and a reference picture buffer 190.

The encoding apparatus 100 may encode the input image in an intra mode and / or an inter mode. In addition, the encoding apparatus 100 may generate a bitstream through encoding of an input image, and may output the generated bitstream. When the intra mode is used as the prediction mode, the switch 115 may be switched to intra, and when the inter mode is used as the prediction mode, the switch 115 may be switched to inter. In this case, the intra mode may mean an intra prediction mode, and the inter mode may mean an inter prediction mode. The encoding apparatus 100 may generate a prediction block for the input block of the input image. In addition, after the prediction block is generated, the encoding apparatus 100 may encode a residual between the input block and the prediction block. The input image may be referred to as a current image that is a target of current encoding. The input block may be referred to as a current block or an encoding target block that is a target of the current encoding.

When the prediction mode is the intra mode, the intra prediction unit 120 may use the pixel value of a block that is already encoded around the current block as a reference pixel. The intra predictor 120 may perform spatial prediction using the reference pixel, and generate prediction samples for the input block through spatial prediction. Intra prediction may refer to intra prediction.

When the prediction mode is the inter mode, the motion predictor 111 may search an area that best matches the input block from the reference image in the motion prediction process, and derive a motion vector using the searched area. . The reference picture may be stored in the reference picture buffer 190.

The motion compensator 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional vector used for inter prediction. In addition, the motion vector may indicate an offset between the current picture and the reference picture. Here, inter prediction may mean inter prediction.

The motion predictor 111 and the motion compensator 112 may generate a prediction block by applying an interpolation filter to a part of a reference image when the motion vector does not have an integer value. . In order to perform inter prediction or motion compensation, a motion prediction and motion compensation method of a prediction unit included in a coding unit based on a coding unit may be skip mode, merge mode, or AMVP mode. ), It may be determined which method is the current picture reference mode, and inter prediction or motion compensation may be performed according to each mode. Here, the current picture reference mode may mean a prediction mode using a pre-restored region in the current picture to which the encoding target block belongs. A motion vector for the current picture reference mode may be defined to specify the pre-restored region. Whether the encoding target block is encoded in the current picture reference mode may be encoded using the reference image index of the encoding target block.

The subtractor 125 may generate a residual block using the difference between the input block and the prediction block. The residual block may be referred to as the residual signal.

The transform unit 130 may generate a transform coefficient by performing transform on the residual block, and output a transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing transform on the residual block. When the transform skip mode is applied, the transform unit 130 may omit the transform on the residual block.

Quantized transform coefficient levels may be generated by applying quantization to the transform coefficients. In the following embodiments, the quantized transform coefficient level may also be referred to as transform coefficient.

The quantization unit 140 may generate a quantized transform coefficient level by quantizing the transform coefficient according to the quantization parameter, and output the quantized transform coefficient level. In this case, the quantization unit 140 may quantize the transform coefficients using the quantization matrix.

The entropy encoder 150 may generate a bitstream by performing entropy encoding according to probability distribution on values calculated by the quantizer 140 or coding parameter values calculated in the encoding process. And output a bitstream. The entropy encoder 150 may perform entropy encoding on information for decoding an image in addition to information on pixels of an image. For example, the information for decoding the image may include a syntax element.

When entropy encoding is applied, a small number of bits are assigned to a symbol having a high probability of occurrence and a large number of bits are assigned to a symbol having a low probability of occurrence, thereby representing bits for encoding symbols. The size of the heat can be reduced. Therefore, compression efficiency of image encoding may be increased through entropy encoding. The entropy encoder 150 may use an encoding method such as exponential Golomb, context-adaptive variable length coding (CAVLC), or context-adaptive binary arithmetic coding (CABAC) for entropy encoding. For example, the entropy encoder 150 may perform entropy coding using a variable length coding (VLC) table. Also, the entropy encoder 150 derives a binarization method of a target symbol and a probability model of a target symbol / bin, and then performs arithmetic coding using the derived binarization method or a probability model. You may.

The entropy encoder 150 may change a two-dimensional block shape coefficient into a one-dimensional vector form through a transform coefficient scanning method to encode a transform coefficient level. For example, upright scanning can be used to scan the coefficients of a block to change it into a one-dimensional vector. Depending on the size of the transform unit and the intra prediction mode, a vertical scan that scans two-dimensional block shape coefficients in a column direction instead of an upright scan and a horizontal scan that scans two-dimensional block shape coefficients in a row direction may be used. That is, according to the size of the conversion unit and the intra prediction mode, it is possible to determine which scan method among upright scan, vertical scan and horizontal scan is used.

A coding parameter may include information derived from an encoding or decoding process as well as information encoded by an encoder and signaled to a decoder, such as a syntax element, and may mean information required when encoding or decoding an image. have. For example, block size, block depth, block splitting information, unit size, unit depth, unit splitting information, quadtree split flag, binary tree split flag, binary tree split direction, intra prediction mode, Intra prediction direction, reference sample filtering method, prediction block boundary filtering method, filter tab, filter coefficient, inter prediction mode, motion information, motion vector, reference image index, inter prediction direction, inter prediction indicator, reference image list , Motion vector predictor, motion vector candidate list, motion merge mode, motion merge candidate, motion merge candidate list, skip mode, interpolation filter type, motion vector size, motion vector representation accuracy , Transform type, transform size, additional (secondary) transform availability information, residual signal presence information, coded block pattern, Coded Block Flag, Quantization Parameter, Quantization Matrix, In-loop Filter Information, In-loop Filter Applicability Information, In-loop Filter Coefficient, Binarization / Debinarization Method, Context Model, Context Bean, Bypass Bean, Transform Coefficient, transform coefficient level, transform coefficient level scanning method, image display / output order, slice identification information, slice type, slice partition information, tile identification information, tile type, tile partition information, picture type, bit depth, luminance signal or color difference At least one or more values or a combined form of the information about the signal may be included in the encoding parameter.

The residual signal may mean a difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by transforming a difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by transforming and quantizing the difference between the original signal and the prediction signal. The residual block may be a residual signal in block units.

When the encoding apparatus 100 performs encoding through inter prediction, the encoded current image may be used as a reference image with respect to other image (s) to be processed later. Therefore, the encoding apparatus 100 may decode the encoded current image again and store the decoded image as a reference image. Inverse quantization and inverse transform on the encoded current image may be processed for decoding.

The quantized coefficients may be dequantized in inverse quantization unit 160. The inverse transform unit 170 may perform an inverse transform. The inverse quantized and inverse transformed coefficients may be summed with the prediction block via the adder 175. A reconstructed block may be generated by adding the inverse quantized and inverse transformed coefficients and the prediction block.

The recovery block may pass through the filter unit 180. The filter unit 180 may apply at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed block or the reconstructed image. Can be. The filter unit 180 may be referred to as an in-loop filter.

The deblocking filter may remove block distortion generated at boundaries between blocks. In order to determine whether to perform the deblocking filter, it may be determined whether to apply the deblocking filter to the current block based on the pixels included in the several columns or rows included in the block. When the deblocking filter is applied to the block, a strong filter or a weak filter may be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, horizontal filtering and vertical filtering may be performed in parallel when vertical filtering and horizontal filtering are performed.

The sample adaptive offset may add an appropriate offset value to the pixel value to compensate for the encoding error. The sample adaptive offset may correct the offset with the original image on a pixel basis for the deblocked image. In order to perform offset correction on a specific picture, the pixels included in the image are divided into a predetermined number of areas, and then, the area to be offset is determined and the offset is applied to the corresponding area or the offset considering the edge information of each pixel. You can use this method.

The adaptive loop filter may perform filtering based on a comparison value between the reconstructed image and the original image. After dividing the pixels included in the image into a predetermined group, one filter to be applied to the group may be determined and filtering may be performed for each group. For information related to whether to apply the adaptive loop filter, the luminance signal may be signaled for each coding unit (CU), and the shape and filter coefficient of the adaptive loop filter to be applied according to each block may vary. In addition, an adaptive loop filter of the same type (fixed form) may be applied regardless of the characteristics of the block to be applied.

The reconstructed block that has passed through the filter unit 180 may be stored in the reference picture buffer 190.

The decoding apparatus 200 may be a video decoding apparatus or an image decoding apparatus.

Referring to FIG. 2, the decoding apparatus 200 may include an entropy decoder 210, an inverse quantizer 220, an inverse transform unit 230, an intra predictor 240, a motion compensator 250, and an adder 255. The filter unit 260 may include a reference picture buffer 270.

The decoding apparatus 200 may receive a bitstream output from the encoding apparatus 100. The decoding apparatus 200 may decode the bitstream in an intra mode or an inter mode. In addition, the decoding apparatus 200 may generate a reconstructed image through decoding and output the reconstructed image.

When the prediction mode used for decoding is an intra mode, the switch may be switched to intra. When the prediction mode used for decoding is an inter mode, the switch may be switched to inter.

The decoding apparatus 200 may obtain a reconstructed residual block from the input bitstream, and generate a prediction block. When the reconstructed residual block and the prediction block are obtained, the decoding apparatus 200 may generate a reconstruction block that is a decoding target block by adding the reconstructed residual block and the prediction block. The decoding target block may be referred to as a current block.

The entropy decoder 210 may generate symbols by performing entropy decoding according to a probability distribution of the bitstream. The generated symbols may include symbols in the form of quantized transform coefficient levels. Here, the entropy decoding method may be similar to the entropy encoding method described above. For example, the entropy decoding method may be an inverse process of the above-described entropy encoding method.

In order to decode the transform coefficient level, the entropy decoder 210 may change the one-dimensional vector form coefficient into a two-dimensional block form through a transform coefficient scanning method. For example, upright scanning can be used to scan the coefficients of a block to change it into a two-dimensional block shape. Depending on the size of the conversion unit and the intra prediction mode, vertical scan or horizontal scan may be used instead of upright scan. That is, according to the size of the conversion unit and the intra prediction mode, it is possible to determine which scan method among upright scan, vertical scan and horizontal scan is used.

The quantized transform coefficient level may be inversely quantized by the inverse quantizer 220 and inversely transformed by the inverse transformer 230. As a result of the inverse quantization and inverse transformation of the quantized transform coefficient level, a reconstructed residual block may be generated. In this case, the inverse quantization unit 220 may apply a quantization matrix to the quantized transform coefficient level.

When the intra mode is used, the intra predictor 240 may generate a prediction block by performing spatial prediction using pixel values of blocks that are already decoded around the decoding target block.

When the inter mode is used, the motion compensator 250 may generate a predictive block by performing motion compensation using a reference vector stored in the motion vector and the reference picture buffer 270. When the value of the motion vector does not have an integer value, the motion compensator 250 may generate a prediction block by applying an interpolation filter to a portion of the reference image. In order to perform motion compensation, a motion compensation method of a prediction unit included in a coding unit is selected from among skip mode, merge mode, AMVP mode, and current picture reference mode. It may be determined whether or not it is a method, and motion compensation may be performed according to each mode. Here, the current picture reference mode may mean a prediction mode using a pre-restored region in the current picture to which the decoding target block belongs. A motion vector for the current picture reference mode may be used to specify the pre-restored region. A flag or index indicating whether the decoding object block is a block encoded in the current picture reference mode may be signaled or inferred through a reference picture index of the decoding object block. In the current picture reference mode, the current picture may exist at a fixed position (eg, the position at which the reference image index is 0 or the last position) in the reference image list for the decoding object block. Alternatively, the reference picture index may be variably positioned in the reference picture list, and a separate reference picture index indicating the location of the current picture may be signaled for this purpose. Here, signaling a flag or index may mean that the encoder entropy encodes the flag or index and includes the flag or index in the bitstream, and the decoder entropy decodes the corresponding flag or index from the bitstream. Entropy Decoding).

The reconstructed residual block and the prediction block may be added through the adder 255. As the reconstructed residual block and the prediction block are added, the generated block may pass through the filter unit 260. The filter unit 260 may apply at least one or more of a deblocking filter, a sample adaptive offset, and an adaptive loop filter to the reconstructed block or the reconstructed image. The filter unit 260 may output the reconstructed image. The reconstructed picture may be stored in the reference picture buffer 270 and used for inter prediction.

3 is a diagram schematically illustrating a division structure of an image when encoding and decoding an image. 3 schematically shows an embodiment in which one unit is divided into a plurality of sub-units.

In order to efficiently divide an image, a coding unit (CU) may be used in encoding and decoding. Here, the coding unit may mean a coding unit. A unit may be a term that collectively refers to a block including 1) a syntax element and 2) image samples. For example, "division of a unit" may mean "division of a block corresponding to a unit". The block division information may include information about a depth of a unit. The depth information may indicate the number and / or degree of division of the unit.

Referring to FIG. 3, the image 300 is sequentially divided into units of a largest coding unit (LCU), and a split structure is determined by units of an LCU. Here, the LCU may be used as the same meaning as a coding tree unit (CTU). One unit may be hierarchically divided with depth information based on a tree structure. Each divided subunit may have depth information. Since the depth information indicates the number and / or degree of division of the unit, the depth information may include information about the size of the sub-unit.

The partition structure may mean a distribution of a coding unit (CU) in the LCU 310. The CU may be a unit for efficiently encoding / decoding an image. This distribution may be determined according to whether to divide one CU into a plurality of CUs (two or more positive integers including 2, 4, 8, 16, etc.). The horizontal and vertical sizes of the CUs created by splitting are either half of the horizontal and vertical sizes of the CU before splitting, or smaller than the horizontal and vertical sizes of the CU before splitting, depending on the number of splits. Can have The partitioned CU may be recursively divided into a plurality of CUs having reduced horizontal and vertical sizes in the same manner.

At this time, partitioning of the CU may be performed recursively up to a predetermined depth. The depth information may be information indicating the size of a CU and may be stored for each CU. For example, the depth of the LCU may be 0, and the depth of the smallest coding unit (SCU) may be a predefined maximum depth. Here, the LCU may be a coding unit having a maximum coding unit size as described above, and the SCU may be a coding unit having a minimum coding unit size.

The division starts from the LCU 310, and the depth of the CU increases by one each time the division reduces the horizontal and vertical sizes of the CU. For each depth, the CU that is not divided may have a size of 2N × 2N. In the case of a partitioned CU, a 2N × 2N sized CU may be divided into a plurality of CUs having an N × N size. The magnitude of N decreases in half for every 1 increase in depth.

For example, when one coding unit is divided into four coding units, the horizontal and vertical sizes of the divided four coding units may each have a size of half compared to the horizontal and vertical sizes of the coding unit before being split. have. For example, when a 32x32 sized coding unit is divided into four coding units, the four divided coding units may each have a size of 16x16. When one coding unit is divided into four coding units, it may be said that the coding unit is divided into quad-tree shapes.

For example, when one coding unit is divided into two coding units, the horizontal or vertical size of the divided two coding units may have a half size compared to the horizontal or vertical size of the coding unit before splitting. . As an example, when a 32x32 coding unit is vertically divided into two coding units, the two split coding units may have a size of 16x32. For example, when a 32x32 size coding unit is horizontally divided into two coding units, the two divided coding units may each have a size of 32x16. When one coding unit is divided into two coding units, it may be said that the coding unit is divided into a binary-tree.

Referring to FIG. 3, an LCU having a depth of 0 may be 64 × 64 pixels. 0 may be the minimum depth. An SCU of depth 3 may be 8x8 pixels. 3 may be the maximum depth. In this case, a CU of 64x64 pixels, which is an LCU, may be represented by a depth of zero. A CU of 32x32 pixels may be represented by depth one. A CU of 16 × 16 pixels may be represented by depth two. A CU of 8x8 pixels, which is an SCU, may be represented by depth 3.

In addition, information on whether the CU is split may be expressed through split information of the CU. The split information may be 1 bit of information. All CUs except the SCU may include partition information. For example, if the value of the partition information is 0, the CU may not be split. If the value of the partition information is 1, the CU may be split.

A CU that is no longer split among CUs partitioned from the LCU may be divided into one or more prediction units (PUs). This process may also be called division.

The PU may be a basic unit for prediction. The PU may be encoded and decoded in any one of a skip mode, an inter screen mode, and an intra screen mode. The PU may be divided into various forms according to modes.

Also, the coding unit may not be divided into prediction units, and the coding unit and the prediction unit may have the same size.

As shown in FIG. 4, in the skip mode, there may be no partition in the CU. In the skip mode, the 2N × 2N mode 410 having the same size as the CU without splitting may be supported.

In the inter-screen mode, eight divided forms in the CU can be supported. For example, in the inter-screen mode, 2Nx2N mode 410, 2NxN mode 415, Nx2N mode 420, NxN mode 425, 2NxnU mode 430, 2NxnD mode 435, nLx2N mode 440, and nRx2N mode 445 may be supported. In the in-screen mode, 2Nx2N mode 410 and NxN mode 425 may be supported.

One coding unit may be split into one or more prediction units, and one prediction unit may also be split into one or more prediction units.

For example, when one prediction unit is divided into four prediction units, the horizontal and vertical sizes of the divided four prediction units may each have a size of half compared to the horizontal and vertical sizes of the prediction unit before splitting. have. For example, when a 32x32 size prediction unit is split into four prediction units, the four divided prediction units may each have a size of 16x16. When one prediction unit is divided into four prediction units, it may be said that the prediction unit is divided into quad-trees.

For example, when one prediction unit is divided into two prediction units, the horizontal or vertical size of the divided two prediction units may have a half size compared to the horizontal or vertical size of the prediction unit before splitting. . For example, when a 32x32 size prediction unit is vertically divided into two prediction units, the two divided prediction units may each have a size of 16x32. For example, when a 32x32 size prediction unit is horizontally divided into two prediction units, the two divided prediction units may each have a size of 32x16. When one prediction unit is divided into two prediction units, it may be said that the prediction unit is divided into a binary-tree.

A transform unit (TU) may be a basic unit used for a process of transform, quantization, inverse transform, and inverse quantization in a CU. The TU may have a shape such as a square shape or a rectangle. The TU may be determined dependent on the size and / or shape of the CU.

Of the CUs partitioned from the LCU, a CU that is no longer split into CUs may be split into one or more TUs. In this case, the partition structure of the TU may be a quad-tree structure. For example, as shown in FIG. 5, one CU 510 may be divided one or more times according to the quadtree structure. If a CU is split more than once, it can be said to be split recursively. Through division, one CU 510 may be configured with TUs of various sizes. Or, it may be divided into one or more TUs based on the number of vertical lines and / or horizontal lines dividing the CU. The CU may be divided into symmetrical TUs and may be divided into asymmetrical TUs. Information about the size / shape of the TU may be signaled for division into an asymmetric TU and may be derived from information about the size / shape of the CU.

Also, the coding unit may not be divided into a transform unit, and the coding unit and the transform unit may have the same size.

One coding unit may be split into one or more transform units, and one transform unit may also be split into one or more transform units.

For example, when one transform unit is divided into four transform units, the horizontal and vertical sizes of the divided four transform units may each have a size of half compared to the horizontal and vertical sizes of the transform unit before splitting. have. For example, when a 32x32 transform unit is divided into four transform units, the divided four transform units may have a size of 16x16. When one transform unit is divided into four transform units, it may be said that the transform unit is divided into quad-trees.

For example, when one transform unit is divided into two transform units, the horizontal or vertical size of the divided two transform units may be half the size of the transform unit before the split. . For example, when a 32x32 transform unit is vertically divided into two transform units, the two divided transform units may have a size of 16x32. For example, when a 32x32 transform unit is horizontally divided into two transform units, the divided two transform units may each have a size of 32x16. When one transform unit is divided into two transform units, the transform unit may be said to be divided into a binary-tree.

When performing the transformation, the residual block may be transformed using at least one of a plurality of pre-defined transformation methods. For example, Discrete Cosine Transform (DCT), Discrete Sine Transform (DST), or KLT may be used as a plurality of pre-defined transformation methods. Which transformation method is applied to transform the residual block may be determined using at least one of inter prediction mode information of the prediction unit, intra prediction mode information, and size / shape of the transform block, and in some cases, indicates a transformation method. The information may be signaled.

6 is a diagram for explaining an embodiment of an intra prediction process.

The intra prediction mode may be a non-directional mode or a directional mode. The non-directional mode may be a DC mode or a planar mode, and the directional mode may be a prediction mode having a specific direction or angle, and the number may be one or more M. The directional mode may be expressed by at least one of a mode number, a mode value, a mode number, and a mode angle.

The number of intra prediction modes may be one or more N including the non-directional and directional modes.

The number of intra prediction modes may vary depending on the size of the block. For example, the size of a block may be 67 pieces in case of 4x4 or 8x8, 35 pieces in case of 16x16, 19 pieces in case of 32x32, and 7 pieces in case of 64x64.

The number of intra prediction modes may be fixed to N regardless of the size of the block. For example, it may be fixed to at least one of 35 or 67 regardless of the size of the block.

The number of intra prediction modes may vary depending on the type of color component. For example, the number of prediction modes may vary depending on whether the color component is a luma signal or a chroma signal.

Intra picture encoding and / or decoding may be performed using sample values or encoding parameters included in neighboring reconstructed blocks.

In order to encode / decode the current block by intra prediction, a step of checking whether samples included in neighboring reconstructed blocks are available as reference samples of the encoding / decoding target block may be performed. If there are samples that are not available as reference samples of the block to be encoded / decoded, at least one or more of the samples included in the neighboring reconstructed blocks are used to copy and / or sample values to samples that are not available as reference samples. Interpolation may be used as a reference sample of a block to be encoded / decoded.

During intra prediction, a filter may be applied to at least one of a reference sample or a prediction sample based on at least one of an intra prediction mode and a size of an encoding / decoding target block. In this case, the encoding / decoding target block may mean a current block and may mean at least one of a coding block, a prediction block, and a transform block. The type of filter applied to the reference sample or the prediction sample may be different according to at least one or more of an intra prediction mode or a size / shape of the current block. The type of filter may vary depending on at least one of the number of filter taps, a filter coefficient value, or a filter strength.

In the intra prediction mode, the non-directional planar mode generates a predicted block of a target encoding / decoding block. The upper right reference sample of the current block may be generated as a weighted sum of the lower left reference samples of the current block.

Among the intra prediction modes, the non-directional DC mode may be generated as an average value of upper reference samples of the current block and left reference samples of the current block when generating the prediction block of the target coding / decoding block. In addition, one or more upper rows and one or more left columns adjacent to the reference sample in the encoding / decoding block may be filtered using reference sample values.

In the directional modes of the intra prediction modes, the prediction block may be generated by using the upper right and / or lower left reference samples, and the directional modes may have different directions. Real interpolation may be performed to generate predictive sample values.

In order to perform the intra prediction method, the intra prediction mode of the current prediction block may be predicted from the intra prediction mode of the prediction block existing around the current prediction block. In case of predicting the intra prediction mode of the current prediction block by using the mode information predicted from the intra prediction mode, if the intra prediction modes of the current prediction block and the neighboring prediction block are the same, the current prediction is performed by using predetermined flag information. Information on the intra prediction modes of the block and the neighboring prediction block may be signaled. If the intra prediction modes of the current prediction block and the neighboring prediction block are different, entropy encoding may be performed to perform intra prediction of the encoding / decoding target block. Mode information can be encoded.

7 is a diagram for explaining an embodiment of an inter prediction process.

The rectangle illustrated in FIG. 7 may represent an image (or a picture). In addition, arrows in FIG. 7 may indicate prediction directions. That is, the image may be encoded and / or decoded according to the prediction direction. Each picture may be classified into an I picture (Intra Picture), a P picture (U-predictive Picture), a B picture (Bi-predictive Picture), and the like. Each picture may be encoded and decoded according to an encoding type of each picture.

When the image to be encoded is an I picture, the image may be encoded in the picture with respect to the image itself without inter prediction. When the image to be encoded is a P picture, the image may be encoded through inter prediction or motion compensation using the reference image only in the forward direction. If the image to be encoded is a B picture, it may be encoded through inter prediction or motion compensation using reference pictures in both forward and reverse directions, and inter prediction or motion using the reference picture in one of the forward and reverse directions. Can be coded through compensation. In this case, when the inter prediction mode is used, the encoder may perform inter prediction or motion compensation, and the decoder may perform motion compensation corresponding thereto. The pictures of the P picture and the B picture that are encoded and / or decoded using the reference picture may be regarded as a picture using inter prediction.

Hereinafter, inter prediction according to an embodiment will be described in detail.

Inter prediction or motion compensation may be performed using a reference picture and motion information. In addition, inter prediction may use the skip mode described above.

The reference picture may be at least one of a previous picture of the current picture or a subsequent picture of the current picture. In this case, the inter prediction may perform prediction on a block of the current picture based on the reference picture. Here, the reference picture may mean an image used for prediction of the block. In this case, an area in the reference picture may be specified by using a reference picture index (refIdx) indicating a reference picture, a motion vector to be described later, and the like.

The inter prediction may select a reference picture corresponding to the current block within the reference picture and the reference picture, and generate a prediction block for the current block using the selected reference block. The current block may be a block targeted for current encoding or decoding among blocks of the current picture.

The motion information may be derived during inter prediction by each of the encoding apparatus 100 and the decoding apparatus 200. In addition, the derived motion information may be used to perform inter prediction. In this case, the encoding apparatus 100 and the decoding apparatus 200 use encoding information and / or decoding efficiency by using motion information of a reconstructed neighboring block and / or motion information of a collocated block (col block). Can improve. The call block may be a block corresponding to a spatial position of a block to be encoded / decoded in a collocated picture (col picture). The reconstructed neighboring block may be a block within the current picture and may be a block that is already reconstructed through encoding and / or decoding. The reconstruction block may be a neighboring block adjacent to the encoding / decoding object block and / or a block located at an outer corner of the encoding / decoding object block. Here, the block located at the outer corner of the encoding / decoding target block is a block vertically adjacent to a neighboring block horizontally adjacent to the encoding / decoding target block or a block horizontally adjacent to a neighboring block vertically adjacent to the encoding / decoding target block. Can be.

Each of the encoding apparatus 100 and the decoding apparatus 200 may determine a block existing at a position corresponding to a block to be encoded / decoded spatially within a call picture, and determines a predetermined relative position based on the determined block. Can be. The predefined relative position may be a position inside and / or outside of a block existing at a position corresponding to a block to be encoded / decoded spatially. In addition, each of the encoding apparatus 100 and the decoding apparatus 200 may derive a call block based on the determined predetermined relative position. Here, the call picture may be one picture among at least one reference picture included in the reference picture list.

The method of deriving the motion information may vary according to the prediction mode of the encoding / decoding target block. For example, as a prediction mode applied for inter prediction, there may be an advanced motion vector prediction (AMVP) and a merge mode. The merge mode may be referred to as a motion merge mode.

For example, when AMVP is applied as the prediction mode, each of the encoding apparatus 100 and the decoding apparatus 200 uses a motion vector of the reconstructed neighboring block and / or a motion vector of the call block. create a motion vector candidate list. The motion vector of the reconstructed neighboring block and / or the motion vector of the call block may be used as a motion vector candidate. Here, the motion vector of the call block may be referred to as a temporal motion vector candidate, and the motion vector of the reconstructed neighboring block may be referred to as a spatial motion vector candidate.

The bitstream generated by the encoding apparatus 100 may include a motion vector candidate index. That is, the encoding apparatus 100 may generate a bitstream by entropy encoding a motion vector candidate index. The motion vector candidate index may indicate an optimal motion vector candidate selected from the motion vector candidates included in the motion vector candidate list. The motion vector candidate index may be signaled from the encoding apparatus 100 to the decoding apparatus 200 through the bitstream.

The decoding apparatus 200 may entropy decode the motion vector candidate index from the bitstream, and select the motion vector candidate of the decoding target block from the motion vector candidates included in the motion vector candidate list using the entropy decoded motion vector candidate index. .

The encoding apparatus 100 may calculate a motion vector difference (MVD) between the motion vector of the encoding target block and the motion vector candidate, and may entropy encode the MVD. The bitstream may include entropy coded MVD. The MVD may be signaled from the encoding apparatus 100 to the decoding apparatus 200 through the bitstream. At this time, the decoding apparatus 200 may entropy decode the received MVD from the bitstream. The decoding apparatus 200 may derive the motion vector of the decoding object block through the sum of the decoded MVD and the motion vector candidate.

The bitstream may include a reference picture index and the like indicating a reference picture. The reference image index may be entropy encoded and signaled from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 may predict the motion vector of the decoding object block using the motion information of the neighboring block, and may derive the motion vector of the decoding object block using the predicted motion vector and the motion vector difference. The decoding apparatus 200 may generate a prediction block for the decoding target block based on the derived motion vector and the reference image index information.

Another example of a method of deriving motion information is a merge mode. The merge mode may mean merging of motions for a plurality of blocks. The merge mode may mean applying motion information of one block to other blocks. When the merge mode is applied, each of the encoding apparatus 100 and the decoding apparatus 200 may generate a merge candidate list using the motion information of the reconstructed neighboring block and / or the motion information of the call block. Can be. The motion information may include at least one of 1) a motion vector, 2) a reference picture index, and 3) an inter prediction prediction indicator. The prediction indicator may be unidirectional (L0 prediction, L1 prediction) or bidirectional.

In this case, the merge mode may be applied in a CU unit or a PU unit. When the merge mode is performed in a CU unit or a PU unit, the encoding apparatus 100 may entropy-code predetermined information to generate a bitstream and then signal the decoding apparatus 200. The bitstream may include predefined information. The predefined information includes: 1) a merge flag, which is information indicating whether to perform a merge mode for each block partition, and 2) which one of neighboring blocks adjacent to an encoding target block is merged with. It may include a merge index that is information about the merge. For example, the neighboring blocks of the encoding object block may include a left neighboring block of the encoding object block, an upper neighboring block of the encoding object block, and a temporal neighboring block of the encoding object block.

The merge candidate list may represent a list in which motion information is stored. In addition, the merge candidate list may be generated before the merge mode is performed. The motion information stored in the merge candidate list includes motion information of neighboring blocks adjacent to the encoding / decoding target block, motion information of a block corresponding to the encoding / decoding target block in the reference image, and motion already existing in the merge candidate list. At least one or more of the new motion information and the zero merge candidate generated by the combination of the information. Here, the motion information of the neighboring block adjacent to the encoding / decoding target block is a spatial merge candidate and the motion information of the block corresponding to the encoding / decoding target block in the reference image is a temporal merge candidate. It may be referred to as).

The skip mode may be a mode in which motion information of a neighboring block is applied to an encoding / decoding target block as it is. The skip mode may be one of modes used for inter prediction. When the skip mode is used, the encoding apparatus 100 may entropy-code information about which block motion information to use as the motion information of the block to be encoded and may signal the decoding apparatus 200 through the bitstream. The encoding apparatus 100 may not signal other information to the decoding apparatus 200. For example, the other information may be syntax element information. The syntax element information may include at least one of motion vector difference information, a coding block flag, and a transform coefficient level.

The residual signal generated after intra-picture or inter-screen prediction may be converted into a frequency domain through a conversion process as part of a quantization process. In addition to the DCT type 2 (DCT-II), the first transform may be performed using various DCT and DST kernels, and these transform kernels may perform 1D transform on horizontal and / or vertical directions for the residual signal. The transformation may be performed by a separate transform, each performed, or the transformation may be performed by a 2D non-separable transform.

For example, the DCT and DST types used for the conversion may be adaptively used for 1D conversion of DCT-V, DCT-VIII, DST-I, and DST-VII in addition to DCT-II as shown in the following table. As in the examples of Tables 1 to 2, a transform set may be configured to derive the DCT or DST type used for the transform.

변환세트Conversion set	변환 conversion
00	DST_VII, DCT-VIIIDST_VII, DCT-VIII
1One	DST-VII, DST-IDST-VII, DST-I
22	DST-VII, DCT-VDST-VII, DCT-V

변환세트Conversion set	변환 conversion
00	DST_VII, DCT-VIII, DST-IDST_VII, DCT-VIII, DST-I
1One	DST-VII, DST-I, DCT-VIIIDST-VII, DST-I, DCT-VIII
22	DST-VII, DCT-V, DST-IDST-VII, DCT-V, DST-I

For example, after defining different transform sets for the horizontal or vertical direction according to the intra prediction mode as shown in FIG. 8, the intra prediction mode of the current encoding / decoding target block in the encoder / decoder and the same Transforms and / or inverse transforms may be performed using the transforms included in the corresponding transform set. In this case, the transform set may not be entropy encoded / decoded but may be defined according to the same rules in the encoder / decoder. In this case, entropy encoding / decoding indicating which transform is used among transforms belonging to the corresponding transform set may be performed. For example, if the size of the block is 64x64 or less, three sets of transforms are constructed as shown in the example of Table 2 according to the intra prediction mode, and each of the three transforms is used as a horizontal transform and a vertical transform. After combining a total of nine multi-transformation methods, encoding efficiency can be improved by encoding / decoding a residual signal using an optimal transform method. In this case, truncated Unary binarization may be used to entropy encode / decode information on which of three transforms belonging to one transform set. In this case, information indicating which transform among transforms belonging to a transform set is used for at least one of a vertical transform and a horizontal transform may be entropy encoded / decoded.

After the above-described first transform is completed, the encoder may perform a secondary transform in order to increase energy concentration of transformed coefficients as shown in the example of FIG. 9. Secondary transforms may also perform split transforms that perform one-dimensional transforms respectively in the horizontal and / or vertical directions, or perform two-dimensional non-separated transforms, and used transform information is signaled or is present and surrounding. It may be implicitly derived from the encoder / decoder according to the encoding information. For example, a transform set for a secondary transform may be defined, such as a primary transform, and the transform set may be defined according to the same rules in the encoder / decoder rather than entropy encoding / decoding. In this case, information indicating which transform is used among the transforms belonging to the corresponding transform set may be signaled and applied to at least one or more of the residual signals through intra-screen or inter-screen prediction.

At least one of the number or type of transform candidates is different for each transform set, and at least one of the number or type of transform candidates is the position, size, partition type, prediction mode of a block (CU, PU, TU, etc.). may be variably determined in consideration of at least one of intra / inter mode or directionality / non-direction of the intra prediction mode.

In the decoder, the second inverse transform may be performed according to whether the second inverse transform is performed, and the first inverse transform may be performed according to whether the first inverse transform is performed on the result of the second inverse transform.

The above-described first-order transform and second-order transform may be applied to at least one or more signal components of luminance / chromatic components or according to an arbitrary coding block size / shape, and may be used or used in any coding block. An index indicating a / second order transform may be entropy encoded / decoded, or may be implicitly derived from the encoder / decoder according to at least one of current and peripheral encoding information.

After the first and / or second-order transform is completed, the residual signal generated after intra-picture or inter-screen prediction undergoes a quantization process, and then the quantized transform coefficients undergo an entropy encoding process. Likewise, the image may be scanned in a diagonal, vertical, or horizontal direction based on at least one of an intra prediction mode or a minimum block size / shape.

In addition, the entropy decoded quantized transform coefficients may be inverse scanned and arranged in a block form, and at least one of inverse quantization or inverse transform may be performed on the block. In this case, at least one of a diagonal scan, a horizontal scan, and a vertical scan may be performed as a reverse scanning method.

For example, when the size of the current coding block is 8x8, the residual signal for the 8x8 block is three scanning order methods shown in FIG. 10 for four 4x4 subblocks after the first, second order transform and quantization. Entropy encoding may be performed while scanning the quantized transform coefficients according to at least one of the following. It is also possible to entropy decode while inversely scanning the quantized transform coefficients. The inverse scanned quantized transform coefficients become transform coefficients after inverse quantization, and at least one of a second order inverse transform or a first order inverse transform may be performed to generate a reconstructed residual signal.

In the video encoding process, one block may be split as shown in FIG. 11 and an indicator corresponding to the split information may be signaled. In this case, the split information may be at least one of a split flag (split_flag), a quad / binary tree flag (QB_flag), a quadtree split flag (quadtree_flag), a binary tree split flag (binarytree_flag), and a binary tree split type flag (Btype_flag). have. Here, split_flag is a flag indicating whether a block is divided, QB_flag is a flag indicating whether a block is divided into quadtrees or binary trees, quadtree_flag is a flag indicating whether a block is divided into quadtrees, binarytree_flag may be a flag indicating whether a block is divided into a binary tree form, and Btype_flag may be a flag indicating a vertical or horizontal division when the block is divided into a binary tree form.

If the division flag is 1, the division flag may be 0, indicating that the partition is not divided. In the case of the quad / binary tree flag, 0 may indicate quadtree division, and 1, binary tree division. This may indicate quadtree splitting. In the case of the binary tree partition type flag, 0 indicates horizontal division, 1 indicates vertical division, and 0 indicates vertical division, and 1 indicates horizontal division.

For example, the split information of FIG. 11 may be derived by signaling at least one of quadtree_flag, binarytree_flag, and Btype_flag as shown in Table 3 below.


quadtree_flagquadtree_flag	1One	00					1One	00					00		00		00		00								00
binarytree_flagbinarytree_flag			1One		00	00			1One		00	00		00		00		00		1One		1One		00	00	00		00
Btype_flagBtype_flag				1One						00											00		1One

For example, the split information of FIG. 11 may be derived by signaling at least one of split_flag, QB_flag, and Btype_flag as shown in Table 4 below.


split_flagsplit_flag	1One		1One			00	00	1One		1One			00	00	00	00	00	1One			1One		00	00	00	00
QB_flag QB_flag		00		1One					00		1One								1One
Btype_flagBtype_flag					1One							00								00		1One

The splitting method may be split only into quadtrees or split only into binary trees depending on the size / shape of the block. In this case, the split_flag may mean a flag indicating whether quadtree or binary tree is split. The size / shape of the block may be derived according to the depth information of the block, and the depth information may be signaled.

When the size of the block falls within a predetermined range, the block may be divided into quadtrees only. Here, the predetermined range may be defined as at least one of the maximum block size or the minimum block size that can be divided only by the quadtree. Information indicating the size of the maximum / minimum block for which the quadtree type division is allowed may be signaled through a bitstream, and the corresponding information may be signaled in units of at least one of a sequence, a picture parameter, or a slice (segment). have. Alternatively, the size of the maximum / minimum block may be a fixed size preset in the encoder / decoder. For example, when the size of the block corresponds to 256x256 to 64x64, the block may be divided into quadtrees only. In this case, the split_flag may be a flag indicating whether the quadtree is split.

When the size of the block falls within a predetermined range, it may be possible to divide only into a binary tree. Here, the predetermined range may be defined as at least one of the maximum block size or the minimum block size that can be divided only by the binary tree. The information indicating the size of the maximum / minimum block that allows the division of the binary tree type may be signaled through a bitstream, and the corresponding information may be signaled in units of at least one of a sequence, a picture parameter, or a slice (segment). have. Alternatively, the size of the maximum / minimum block may be a fixed size preset in the encoder / decoder. For example, when the size of the block corresponds to 16x16 to 8x8, it may be possible to divide only into a binary tree. In this case, the split_flag may be a flag indicating whether a binary tree is split.

After the one block is partitioned into a binary tree, when the partitioned block is further partitioned, it may be partitioned only into a binary tree.

When the horizontal or vertical size of the divided block is a size that can no longer be divided, the one or more indicators may not be signaled.

In addition to the binary tree splitting under the quadtree, after the binary tree splitting, the quadtree based splitting may be possible.

As illustrated in FIG. 12, the intra prediction may include an intra prediction mode derivation step S1210, a reference sample configuration step S1220, and / or an intra prediction prediction step S1230.

In the in-picture prediction mode derivation step (S1210), the intra prediction mode of the neighboring block is used, the intra prediction mode of the current block is decoded (eg, entropy decoding) from the bitstream, or the intra prediction mode of the color component is determined. Or an intra prediction mode using a transform model may be used to derive an intra prediction mode of the current block. Alternatively, in the in-picture prediction mode derivation step (S1210), a combination of the intra prediction mode of the neighboring block, the combination of one or more intra prediction modes of the neighboring block, and / or the current block using the intra prediction mode derived using the MPM. In-screen prediction mode can be derived.

The reference sample configuring step S1220 may configure the reference sample by performing the reference sample selection step and / or the reference sample filtering step.

In the intra prediction operation step (S1230), the intra prediction of the current block may be performed using non-directional prediction, directional prediction, location information based prediction, inter-color prediction, and / or residual signal prediction. The intra prediction operation step S1230 may additionally perform filtering on the prediction sample. When directional prediction is performed, different directional predictions may be performed according to one or more sample units. For example, one or more sample units may be a single sample, sample group, line, and / or subblock.

Hereinafter, the intra prediction mode derivation step S1210 will be described in more detail.

As described above, in order to derive an intra prediction mode for a current block, a method of using an intra prediction mode of one or more neighboring blocks, a method of decoding an intra prediction mode of a current block from a bitstream, and encoding a neighboring block At least one of a method using a parameter and a method using an intra prediction mode between color components may be used. In this case, the neighboring block may be one or more blocks reconstructed before encoding / decoding of the current block.

When the neighboring block is located outside the boundary of at least one predetermined unit among a picture, a slice, a tile, and a coding tree unit (CTU), or when the PCM mode or the inter prediction is applied, the neighboring block may not be determined to be available. have. The intra prediction mode corresponding to the unavailable neighboring block may be replaced with a DC mode, a planar mode, or a predetermined intra prediction mode.

The size of the current block may be W x H. W and H are each a positive integer and can be the same or different. W and / or H may be, for example, at least one of 2, 4, 8, 16, 32, 64, 128, 256, 512.

In FIG. 13, a to k displayed in the neighboring block may mean an intra prediction mode or a mode number of the neighboring block. The position of the neighboring block used to derive the intra prediction mode of the current block may be a predefined fixed position. Alternatively, information about the position of the neighboring block may be derived through encoding / decoding. In this specification, encoding / decoding may be used to mean entropy encoding and decoding.

When the intra prediction mode of the neighboring block is used, the predetermined mode of the neighboring block may be derived into the intra prediction mode of the current block. For example, the intra prediction mode i of the neighboring block to which the (-1, 0) sample adjacent to the left of the (0, 0) sample of the current block belongs may be derived to the intra prediction mode of the current block. Alternatively, f, the intra prediction mode of the neighboring block to which the (0, -1) sample adjacent to the (0, 0) sample of the current block belongs, may be derived as the intra prediction mode of the current block. Alternatively, b, the intra prediction mode of the neighboring block to which the (-1, -1) sample adjacent to the upper left of the (0, 0) sample of the current block belongs, may be derived as the intra prediction mode of the current block. Alternatively, g, an intra prediction mode of the neighboring block to which the (W-1, -1) sample adjacent to the (W-1, 0) sample of the current block belongs, may be derived as the intra prediction mode of the current block. . Alternatively, k, the intra prediction mode of the neighboring block to which the [W, -1] sample adjacent to the upper right end of the (W-1, 0) sample of the current block belongs, may be derived as the intra prediction mode of the current block. Alternatively, j, the intra prediction mode of the neighboring block to which the (1, H-1) sample adjacent to the left of the (0, H-1) sample of the current block belongs, may be derived as the intra prediction mode of the current block. Alternatively, l, the intra prediction mode of the neighboring block to which the (-1, H) sample adjacent to the lower left end of the (0, H-1) sample of the current block belongs, may be derived as the intra prediction mode of the current block. Alternatively, the intra prediction mode of the neighboring block at a predetermined position among the neighboring blocks may be derived into the intra prediction mode of the current block. For example, the predetermined position may be encoded / decoded from the bitstream or derived based on encoding parameters. For example, the predetermined position may be a block in which an intra prediction mode is e.

Alternatively, one or more neighboring blocks of neighboring blocks of the current block may be selected. The selection may be performed based on information explicitly signaled via the bitstream. Alternatively, the selection may be performed according to preset criteria in the encoder and the decoder. The intra prediction mode of the current block may be derived from the intra prediction modes of the selected one or more neighboring blocks. For example, the intra prediction mode of the current block may be derived using statistical values of the intra prediction modes of the selected neighboring blocks. For example, the statistical value may include a minimum value, a maximum value, an average value, a weighted average value, a mode value, and / or a median value.

For example, i or f, which is an intra prediction mode of the neighboring blocks to which the samples adjacent to the left and top of the (0, 0) sample of the current block belong, is derived from the mode with the smaller or larger mode number as the intra prediction mode of the current block. can do. For example, when the intra prediction modes of the selected neighboring blocks are b, f, g, i, and j, the mode having the smallest number may be derived as the intra prediction mode of the current block. For example, when the intra prediction modes of the selected neighboring blocks are i, b, and f, a mode having a number corresponding to the middle may be derived as the intra prediction mode of the current block. For example, the most frequently occurring mode of the intra prediction modes of the adjacent neighboring blocks of the current block may be derived as the intra prediction mode of the current block.

Alternatively, the intra prediction mode of the current block may be derived by combining the intra prediction modes of one or more neighboring blocks. The intra prediction mode may be expressed by at least one of a mode number, a mode value, and a mode angle. For example, an average of one or more intra prediction modes of neighboring blocks may be derived to the intra prediction modes of the current block. The average of the two prediction modes in the screen may mean at least one of an intermediate number of two mode numbers, an intermediate value of two mode values, and an intermediate angle of two mode angles.

For example, the mode corresponding to the average of the mode values of i and f, the intra prediction modes of the neighboring blocks to which the adjacent and upper samples of (0, 0) samples of the current block belong, is defined as the intra prediction mode of the current block. Can be induced. For example, the intra prediction mode Pred_mode of the current block may be derived by at least one method of (1) to (3) below.

Alternatively, when the intra prediction mode i of the neighboring block is the non-directional mode, the intra prediction mode of the current block may be derived to i. Alternatively, when the intra prediction mode f of the neighboring block is the directional mode, the intra prediction mode of the current block may be derived to f.

Alternatively, the intra prediction mode of the current block may be derived as a mode corresponding to an average of at least one or more of the mode values of b, f, g, i and j which are intra prediction modes of neighboring blocks. For example, the intra prediction mode Pred_mode of the current block may be derived by at least one method of (1) to (4) below.

Alternatively, a mode corresponding to an average of available intra prediction modes of adjacent neighboring blocks may be derived as the intra prediction mode of the current block. For example, if the left neighboring block of the current block is located outside the boundaries of the picture, tile, slice, and / or CTU, or is not available because it corresponds to at least one of the PCM mode or the inter-screen mode, the upper neighboring blocks are in the screen. A mode corresponding to the statistical values of the prediction modes (eg, f and g) may be derived as an intra prediction mode of the current block.

For example, a weighted average or weighted sum may be used as a statistical value of intra prediction modes of neighboring blocks. In this case, the weight may be given based on the direction of the intra prediction mode of the neighboring block. For example, relatively large weighted modes may be predefined or signaled. For example, the relatively weighted modes may be at least one of a vertical direction mode, a horizontal direction mode, and a non-directional mode. These modes may be given the same weight or different weights. For example, the intra prediction mode Pred_mode of the current block may be derived as a weighted sum of the modes i and f using Equation 3 below. In Equation 3 below, the mode f may be a mode in which a relatively large weight is assigned (eg, a vertical direction mode).

Alternatively, the weight to be used for the weighted sum may be determined based on the size of the neighboring block. For example, when the size of the block adjacent to the top of the current block is larger than the size of the block adjacent to the left, a larger weight may be given to the intra prediction mode of the block adjacent to the top. Alternatively, a larger weight may be given to an intra prediction mode of a small neighboring block.

Alternatively, when the at least one intra prediction mode of the neighboring block is the non-directional mode, the non-directional mode may be derived to the intra prediction mode of the current block. Alternatively, the intra prediction mode of the current block may be derived using the intra prediction mode of the neighboring blocks except for the non-directional mode. When the intra prediction modes of the neighboring blocks are all non-directional modes, the intra prediction modes of the current block may be derived to at least one of the DC mode and the planar mode.

Alternatively, the intra prediction mode of the current block may be derived using a Most Probable Mode (MPM) based on the intra prediction mode of the neighboring block. When using the MPM, one or more information about the intra prediction mode of the current block may be encoded / decoded.

When using the MPM, an MPM list may be constructed. The MPM list may include an intra prediction mode derived based on the intra prediction mode of the neighboring block. The MPM list may include N candidate modes. N is a positive integer and may vary depending on the size and / or shape of the current block. Alternatively, information about N may be signaled through the bitstream.

For example, the intra prediction mode of the current block derived using the intra prediction mode of the one or more neighboring blocks may be a candidate mode included in the MPM list.

In the example shown in FIG. 13, (-1, H-1), (W-1, -1), (W, -1), (-1, H), (-1, -1, adjacent to the current block Intra prediction modes of the neighboring block of the sample position may be used. For example, the MPM list may be configured in the order of j, g, planar, DC, l, k, and b. Alternatively, the MPM list may be configured in the order of i, f, Planar, DC, l, k, and b. In this case, the overlapping mode may be included only once in the MPM list. If there are overlapping modes and the MPM list is not all filled, additional candidate modes may be included in the list based on the modes included in the list. For example, a mode corresponding to + N or -N (N is a positive integer, for example, 1) of the modes included in the list may be added to the list. Alternatively, at least one mode not included in the list among the horizontal mode, the vertical mode, the 45 degree mode, the 135 degree mode, and the 225 degree mode may be added to the list. Alternatively, the MPM list may be constructed using a combination of one or more intra prediction modes and / or statistical values of neighboring blocks.

There may be a plurality of MPM lists, and the method of configuring each MPM list may be different. For example, three MPM lists (MPM list 1, MPM list 2 and MPM list 3) may be constructed. In this case, the intra prediction modes included in each MPM list may not overlap.

An indicator (eg, prev_intra_luma_pred_flag) indicating whether the same mode as the intra prediction mode of the current block exists in the derived MPM list may be encoded in the bitstream or decoded from the bitstream.

When the indicator indicates that the same mode as the intra prediction mode of the current block exists in the MPM list, index information (eg, mpm_idx) indicating which mode among the modes included in the MPM list is encoded in the bitstream or the bitstream. Can be decrypted from. An intra prediction mode of the current block may be derived based on the decoded index information.

When the indicator indicates that the same mode as the intra prediction mode of the current block does not exist in the MPM list, information about the intra prediction mode of the current block may be encoded in the bitstream or decoded from the bitstream. The intra prediction mode of the current block may be derived based on the information about the intra prediction mode of the decoded current block. In this case, intra prediction modes not included in the MPM list may be arranged in at least one of ascending and descending order. Alternatively, one or more groups may be configured by selecting one or more of intra prediction modes not included in the MPM list. For example, one group may be configured using a mode corresponding to + N or -N (N is a positive integer, for example, 1, 2, or 3) of the intra prediction mode included in the MPM list. . In this case, the group may be configured as an on-screen mode corresponding to a predetermined number (eg, 8 and 16), and the mode included in the group may be a mode not included in the MPM list.

Alternatively, as described above, when there are a plurality of MPM lists, the indicator (eg, prev_intra_luma_pred_flag) may indicate whether the same mode as the intra prediction mode of the current block exists in MPM list 1. When the indicator indicates that the same mode does not exist in the MPM list 1, it may be determined whether the same mode exists in the MPM list 2. When the same mode exists in the MPM list 2, the mode may be derived as an intra prediction mode of the current block. When the same mode does not exist in the MPM list 2, the determination on the MPM list 3 may be performed. In this way, the determination of the plurality of MPM lists may be performed sequentially.

Alternatively, separate information indicating one of the plurality of MPM lists may be transmitted. In this case, the intra prediction mode of the block can be derived by using the MPM list indicated by the separate information and the indicator (for example, prev_intra_luma_pred_flag).

Alternatively, a predetermined candidate of the derived MPM list may be derived to an intra prediction mode of the current block. For example, the intra prediction mode of the current block may be derived to a mode corresponding to list 0 which is the first of the MPM list. Alternatively, the index corresponding to the predetermined mode in the list may be encoded / decoded to derive the corresponding mode into the intra prediction mode of the current block.

In constructing the MPM list, one MPM list may be configured for a block having a predetermined size. When the predetermined size block is divided into a plurality of sub blocks, each of the plurality of sub blocks may use the configured MPM list.

For example, when the current block corresponds to the block having the predetermined size, an MPM list for the current block may be configured. When the current block is divided into one or more sub blocks, each of the sub blocks may derive an intra prediction mode for each of the sub blocks using the configured MPM list. For example, if the current block is 8x8 and the subblocks are 4x44, after constructing the MPM list for the current block, each subblock may use the constructed MPM list.

In constructing the MPM list, MPM lists for sub-blocks generated by dividing blocks of a predetermined size may be configured based on the blocks of the predetermined size, respectively.

For example, when the current block corresponds to the block having the predetermined size, the MPM list for each subblock in the current block may be configured using the intra prediction mode of the neighboring block of the current block. For example, when the current block is 8x8 and the four subblocks are 4x4, the MPM list for each of the four subblocks may be configured using the intra prediction mode of the neighboring blocks of the current block. Therefore, the MPM lists for the four sub blocks can be configured at the same time.

Alternatively, the intra prediction mode of the current block may be derived using at least one of the intra prediction mode of the current block derived from the MPM and the intra prediction mode of the neighboring block.

For example, when the intra prediction mode of the current block derived using the MPM is Pred_mpm, the intra prediction mode of the current block is changed by changing the Pred_mpm to a predetermined mode using one or more intra prediction modes of a neighboring block. Can be derived.

For example, Pred_mpm may be increased or decreased by N by comparing the size with the intra prediction mode of the neighboring block. In this case, N may be a predetermined integer such as +1, +2, +3, 0, -1, -2, -3, and the like. For example, if Pred_mpm is smaller than a statistical value of the intra prediction mode of the neighboring block and / or the intra prediction modes of the one or more neighboring blocks, Pred_mpm may be increased. Alternatively, if Pred_mpm is larger than the intra prediction mode of the neighboring block, Pred_mpm may be reduced. Or it may be derived based on the value compared to Pred_mpm and / or Pred_mpm.

In the example shown in FIG. 13, when Pred_mpm is smaller than the mode value of f, Pred_mpm + 1 may be derived to the intra prediction mode of the current block. Alternatively, when the Pred_mpm is smaller than the mode value of g, Pred_mpm + 1 may be derived to the intra prediction mode of the current block. Alternatively, when Pred_mpm is smaller than the mode value of f, Pred_mpm + 2 may be derived to the intra prediction mode of the current block. Alternatively, when the Pred_mpm is larger than the mode value of f, Pred_mpm-1 may be derived to the intra prediction mode of the current block. Alternatively, when the Pred_mpm is smaller than the mode value of i, Pred_mpm + 1 may be derived to the intra prediction mode of the current block. Alternatively, when Pred_mpm is smaller than the average of f and i, Pred_mpm + 1 may be derived to the intra prediction mode of the current block. Alternatively, when the Pred_mpm is smaller than the average value of f and i, half of the difference between the Pred_mpm and the average value may be increased. For example, Pred_mpm + {((f + i + 1) >> 1-Pred_mpm + 1) >> 1} can be derived into the intra prediction mode of the current block.

Alternatively, when one of the modes of the Pred_mpm and the neighboring block is the non-directional mode and the other is the directional mode, the non-directional mode is induced to the intra prediction mode of the current block or the directional mode is the intra prediction mode of the current block. Can be induced.

In the case of deriving the intra prediction mode of the current block using a Most Probable Mode (MPM) list, for example, at least one or more of the following MPM lists may be used. Alternatively, the intra prediction mode of the current block may be entropy encoded / decoded.

MPM list of current block

At least one of the MPM lists of higher blocks for the current block

At least one of the MPM lists of neighboring blocks for the current block

In this case, information necessary for configuring an MPM list, such as whether the MPM list of the current block is used, whether at least one or more MPM lists of upper blocks for the current block are used, and whether or not at least one or more MPM lists of adjacent blocks for the current block are used. Is a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, a tile header, a CTU unit, a CU unit, a PU unit, Entropy may be encoded / decoded through at least one of the TU units.

The upper block may be a block having a depth value smaller than the depth value of the current block. In addition, the upper block may mean at least one or more of the blocks including the current block among the blocks having the small depth value. Here, the depth value may mean a value that increases by 1 whenever the block is divided. For example, a depth value of an unsegmented coding tree unit (CTU) may be zero.

In addition, the upper block may mean a combination of at least one of the following embodiments or the following embodiments. When the first block is an upper block and the second block is a current block, the first block may include the second block. In this case, the first block may mean a block that is shallower than the second block. In this case, a shallow block may have the same meaning as a block having a small depth value. Alternatively, the first block may mean a block larger in size than the second block. In this case, the large block may be a shallow block.

Information representing at least one of the size or depth of the first block may be signaled from an encoder. The information may be signaled at at least one of a VPS, an SPS, a picture, a slice, a tile, and a block level.

At least one of the size or depth of the first block may be derived based on at least one of the size or depth of the second block. For example, at least one of the size or depth of the first block may be derived based on a value added or subtracted from a size (or depth) value of the second block (current block). Alternatively, at least one of the size or depth of the first block may have a fixed value pre-committed in the encoder / decoder.

The neighboring block may be at least one of blocks spatially and / or temporally adjacent to the current block. The neighboring blocks may be blocks that are already encoded / decoded. In addition, the adjacent block may have a depth (or size) value equal to or different from that of the current block. The adjacent block may mean a block at a predetermined position with respect to the current block. The predetermined position may be at least one of an upper left end, an upper end, an upper right end, a left side, and a lower left end based on the current block.

Alternatively, the predetermined position may be a position in a picture different from the picture to which the current block belongs. The block in the predetermined position may mean at least one of a block located at the same position as the current block and / or a block adjacent to the same position in the other picture. Alternatively, the block at the predetermined position may be a block having the same prediction mode as the current block in a specific region in the other picture corresponding to the current block.

In addition, the adjacent block may mean a combination of at least one of the following embodiments or the following embodiments. When the first block is an adjacent block and the second block is a current block, the first block may be an encoded / decoded block adjacent to the second block. The first block may be a block having the same depth as that of the second block. The first block may be a block having the same size as that of the second block.

The first block and the second block may belong to the same coding block (CTU, CU, etc.) or may belong to different coding blocks. The depth and / or size of the first block may be different from the depth and / or size of the second block.

Here, the MPM list of the upper block or the neighboring block may mean an MPM list configured based on the upper block or the neighboring block. In this case, the intra prediction mode of the encoded / decoded block adjacent to the upper block or the neighboring block may be added to the MPM list of the upper block or the neighboring block.

For example, in FIG. 14, the block U (thick solid line block) may be an upper block of the blocks F, G, H, I, and J. In this case, at least one of the blocks F, G, H, I, and J may be the current block.

For example, in FIG. 14, the block V (bold dotted block) may be an upper block of the blocks G, H, I, and J. In this case, at least one of the blocks G, H, I, and J may be a current block.

For example, in FIG. 14, the block W (dot pattern block) may be an upper block of the blocks G, H, and I. In this case, at least one of the blocks G, H, and I may be a current block.

For example, in FIG. 14, block X (a diamond pattern block) may be an upper block of blocks H and I. In this case, at least one of the blocks H and I may be a current block.

For example, in FIG. 14, an adjacent block of the current block D may be at least one of B, C, and K.

For example, in FIG. 14, an adjacent block of the current block L may be at least one of C, D, E, H, and K.

For example, in FIG. 14, an adjacent block of the current block P may be at least one of E, H, I, J, L, N, and O.

For example, the neighboring block of the current block S in FIG. 14 may be at least one of I, J, P, Q, and R.

The N MPM lists may be used to derive the intra prediction mode of the current block or entropy encode / decode the intra prediction mode of the current block. In this case, N may mean 0 or a positive integer. That is, the intra prediction mode of the current block may be derived using the plurality of MPM lists, or the entropy encoding / decoding of the intra prediction mode of the current block may be performed. In addition, the plurality of MPM lists may mean multiple MPM lists or multiple lists. In this case, the N MPM lists for the current block may include at least one of the MPM list of the current block, the MPM list of the upper block, and the MPM list of the neighboring block.

In addition, the N MPM lists may be generated using at least one of encoding parameters of the current block.

In addition, at least one of the sub blocks in a specific block may be the current block, and in this case, an upper block of the sub block may be the specific block. Here, the sub block may be included in the specific block. In addition, the sub block may be a block divided from the specific block. In addition, at least one or more of the sub blocks that do not correspond to the current block among the sub blocks divided from the specific block may be adjacent blocks of the current block. Here, the sub block may mean a lower block in a meaning opposite to that of the upper block.

For example, when the current block is referred to as H in FIG. 14, the plurality of MPM lists for the current block may be configured by at least one of the methods described below. Here, the plurality of MPM lists may include at least one of an MPM list configured based on the current block and an MPM list configured based on the upper block of the current block.

For example, in FIG. 14, an MPM list configured based on the upper block X may be used for the current block H.

For example, in FIG. 14, an MPM list configured based on the upper block W may be used for the current block H.

For example, in FIG. 14, an MPM list configured based on the upper block V may be used for the current block H.

For example, in FIG. 14, an MPM list configured based on the upper block U may be used for the current block H.

For example, in FIG. 14, at least one or more of the MPM lists configured based on at least one or more of upper blocks X, W, V, and U may be used to derive an intra prediction mode of the current block H.

For example, in FIG. 14, when the current block is H, the current block may be configured by at least one of the following methods for describing a plurality of MPM lists. Here, the plurality of MPM lists may include at least one of an MPM list configured based on the current block and an MPM list configured based on the adjacent block of the current block.

For example, in FIG. 14, an MPM list configured based on the neighboring block E may be used for the current block H.

For example, in FIG. 14, an MPM list constructed based on the neighboring block G may be used for the current block H.

For example, in FIG. 14, at least one or more of the MPM lists configured based on at least one or more of the adjacent blocks E and G may be used for the current block H.

The intra prediction mode of the current block may be derived using the constructed MPM list or may be entropy encoded / decoded.

Using the MPM list of the higher block or the neighboring block for the current block H means that the MPM of the higher block or the neighboring block is used for deriving the intra prediction mode of the current block or encoding / decoding the intra prediction mode of the current block. This may mean that lists are used.

The plurality of MPM lists for the current block may include MPM lists for N upper blocks. In this case, N may be 0 or a positive integer.

In this case, information such as the number N of the upper blocks included, the depth value, the range of the depth value, and / or the difference between the depth value of the current block and the upper block may be necessary to form the MPM list of the upper block. Information necessary for constructing the MPM list of the upper block includes: video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), slice header, tile Entropy encoding / decoding may be performed in at least one of a header, a CTU unit, a CU unit, a PU unit, and a TU unit.

For example, when the depth value of the current block is D, the MPM list of the upper block may be configured using at least one or more of the methods described below. As described above, the configured MPM list of the upper block may be used for deriving the intra prediction mode of the current block or entropy encoding / decoding of the intra prediction mode of the current block. Here, D may be 0 or a positive integer.

For example, the MPM list of the upper block having a depth value of D-1 may be used for the current block.

For example, the MPM list of the upper block having a depth value of D-2 may be used for the current block.

For example, an MPM list of higher blocks having a depth value of D-K may be used for the current block. Here, K may be a positive integer less than or equal to D.

For example, an MPM list of upper blocks having depth values from D-1 to D-2 may be used for the current block.

For example, an MPM list of upper blocks having depth values from D-1 to D-3 may be used for the current block.

For example, an MPM list of upper blocks having depth values from D-1 to D-K may be used for the current block. Here, K may be a positive integer less than or equal to D.

For example, an MPM list of higher blocks having a depth value from D-K to D-l may be used for the current block. Here, K and l may be a positive integer less than or equal to D. K may also be less than l.

For example, when using one upper block, an MPM list of upper blocks having a depth value of D-1 or 0 may be used for the current block.

For example, when using two upper blocks, an MPM list of at least two upper blocks among upper blocks having a depth-returned value of 0, 1, D-1 or D-2 may be used for the current block.

For example, when using K upper blocks, an MPM list of at least K upper blocks among upper blocks having a depth value of D-1 to DK and a depth value of 0 to K-1 may be used for the current block. have. Here, K may be a positive integer less than or equal to D.

For example, when using K upper blocks, an MPM list of K upper blocks may be used based on the current block. Here, K may be a positive integer less than or equal to D.

When the MPM list of the upper blocks is included in the plurality of MPM lists for the current block, the number and / or depth value of the upper block used may be derived using the size and / or depth information of the current block.

For example, when the current block is a WxH block having a depth value of D, the size of the current block may be represented by the number of WxH pixels. When the number of pixels of the current block is greater than or equal to a predetermined threshold, an MPM list of at least one or more upper blocks among upper blocks having a depth value from D-1 to D-K may be used for the current block. Here, K may be a positive integer less than D.

Also, for example, when the number of pixels of the current block is smaller than a predetermined threshold, an MPM list of at least one or more higher blocks among upper blocks having depth values from D-1 to DL may be used for the current block. . Here, L may be a positive integer greater than K.

For example, when the depth value of the current block is D, and D is less than or equal to the predetermined depth value T, the MPM list of at least one or more higher blocks among upper blocks having a depth value from D-1 to DK is obtained. Available for the current block. Here, K may be a positive integer less than D.

Also, for example, when the depth value D of the current block is greater than T, an MPM list of at least one or more upper blocks among upper blocks having depth values from D-1 to D-L may be used for the current block. Here, L may be a positive integer greater than K.

The plurality of MPM lists for the current block may include MPM lists for N adjacent blocks. The N adjacent blocks may include adjacent blocks of a predetermined position. N may be zero or a positive integer.

Information such as the number N, depth value, size, and / or location of the neighboring blocks included in the neighboring block may be necessary to construct the MPM list of the neighboring block. Information necessary for constructing the MPM list of the adjacent block includes: video parameter set (VPS), sequence parameter set (SPS), picture parameter set (PPS), adaptation parameter set (APS), slice header, tile Entropy encoding / decoding may be performed in at least one of a header, a CTU unit, a CU unit, a PU unit, and a TU unit. The number and / or location of adjacent blocks may be variably determined according to the size, shape and / or location of the current block. The MPM list of the neighboring blocks may be constructed when the depth value of the neighboring block is a preset value or falls within a predetermined range. In this case, the predetermined range may be defined as at least one of a minimum value and a maximum value. Information regarding at least one of the minimum value and the maximum value may be entropy encoded / decoded in the above-described predetermined unit.

For example, in FIG. 14, when the current block is P and the depth value is D, the plurality of MPM lists for the current block may be configured by at least one of the methods described below. Here, the plurality of MPM lists may include at least one of an MPM list configured based on the current block and an MPM list configured based on the adjacent block of the current block.

For example, an MPM list configured based on the left neighboring block L or N of the current block may be used for the current block P.

For example, an MPM list configured based on the upper left neighboring block E of the current block may be used for the current block P. FIG.

For example, the MPM list configured based on the lower left adjacent block O of the current block may be used for the current block P.

For example, an MPM list configured based on the upper neighboring block H or I of the current block may be used for the current block P.

For example, an MPM list configured based on the upper right neighboring block J of the current block may be used for the current block P.

For example, at least two MPM lists of the upper left, upper, upper right, left, and lower left adjacent blocks of the current block may be used for the current block P.

For example, at least three MPM lists among the upper left, upper, upper right, left, and lower left adjacent blocks of the current block may be used for the current block P.

For example, at least four MPM lists of the upper left, upper, upper right, left, and lower left adjacent blocks of the current block may be used for the current block P.

For example, at least five MPM lists among the upper left, upper, upper right, left, and lower left adjacent blocks of the current block may be used for the current block P.

In addition, the intra prediction mode derived based on at least one of the current block, the upper block, and the adjacent block may be included in one MPM list for the current block. That is, when the current block does not use a plurality of MPM lists and uses one MPM list, at least one of intra prediction modes derived based on at least one of the current block, the higher block, and the adjacent block is used. MPM list can be constructed.

When the N MPM list for the current block includes the MPM list of at least one or more of the upper blocks and the adjacent blocks, the order of configuring the N MPM lists may be determined. In this case, N may be 0 or a positive integer.

The order of constructing the MPM list may be a predetermined order in the encoder and the decoder. Alternatively, the order of constructing the MPM list may be determined based on encoding parameters of respective corresponding blocks. Alternatively, the order of constructing the MPM list may be determined based on an encoding parameter of the current block. Alternatively, the information about the order of configuring the MPM list may be entropy encoded / decoded.

For example, in FIG. 14, the current block is H and the MPM list of the current block may be referred to as MPM_LIST_CUR.

In addition, MPM lists of X, W, V, and U configured based on upper blocks of the current block may be referred to as MPM_LIST_X, MPM_LIST_W, MPM_LIST_V, and MPM_LIST_U, respectively.

In addition, MPM lists of L, E, and G configured based on adjacent blocks of the current block may be referred to as MPM_LIST_L, MPM_LIST_E, and MPM_LIST_G, respectively.

The order of constructing the N MPM lists for the current block may be determined by at least one or more of the methods described below. The number of upper blocks and / or adjacent blocks used in the method described below is just an example, and other numbers of blocks may be used.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_CUR-> MPM_LIST_X-> MPM_LIST_W-> MPM_LIST_V-> MPM_LIST_U.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_U-> MPM_LIST_V-> MPM_LIST_W-> MPM_LIST_X-> MPM_LIST_CUR.

For example, a plurality of MPM lists for the current block H can be constructed by using MPM_LIST_CUR as the first MPM list, and using the MPM list of at least K higher blocks sorted in ascending or descending order based on the depth value. have. Here, K may be zero or a positive integer.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_CUR-> MPM_LIST_L-> MPM_LIST_G-> MPM_LIST_E.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_L-> MPM_LIST_G-> MPM_LIST_E-> MPM_LIST_CUR.

For example, a plurality of MPM lists for the current block H are used by using MPM_LIST_CUR as the first MPM list, and using MPM lists of at least one adjacent block among at least one of upper left, left, lower left, upper, and upper right in a predetermined order. Can be configured.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_CUR-> MPM_LIST_X-> MPM_LIST_L.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_CUR-> MPM_LIST_L-> MPM_LIST_X.

For example, a plurality of MPM lists for the current block H may be configured in the order of MPM_LIST_CUR-> higher block K MPM lists in a predetermined order-> adjacent block L MPM lists in a predetermined order. In this case, K and L may be 0 or a positive integer.

For example, a plurality of MPM lists for the current block H may be configured in order of MPM_LIST_CUR-> neighboring block L MPM lists in a predetermined order-> higher block K MPM lists in a predetermined order. In this case, K and L may be 0 or a positive integer.

For example, a plurality of MPM lists for the current block H may be configured in order of at least K MPM lists among upper blocks and adjacent blocks according to MPM_LIST_CUR-> predetermined order. In this case, K may be a positive integer.

For example, a plurality of MPM lists for the current block H may be configured with MPM_LIST_CUR and at least K MPM lists among upper blocks and adjacent blocks in a predetermined order. In this case, K may be a positive integer.

In this case, the late order MPM list may not include the intra prediction mode included in the fast order MPM list.

Also, a variable length code of an indicator for the faster order MPM list may be shorter than a variable length code of the indicator for the late order MPM list.

Also, the faster MPM list may include fewer candidates than the late MPM list.

In addition, an indicator for the MPM list may be allocated according to the order of the configured MPM list.

According to at least one method of constructing the MPM list, the N MPM lists for the current block may include at least one MPM list of upper blocks and adjacent blocks. In this case, the plurality of MPM lists may be configured not to include intra prediction modes overlapping each other. In this case, N may be 0 or a positive integer.

The N MPM lists used for the current block may be expressed as MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_N. At least one of the MPM_LIST_CUR, MPM_LIST_X, MPM_LIST_W, MPM_LIST_V, MPM_LIST_U, MPM_LIST_L, MPM_LIST_E, and MPM_LIST_G may correspond to at least one of MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_N.

Here, the number of intra prediction modes that each MPM list may include may be represented by C1, C2, ... CN. Here, N, C1, C2, ..., CN may be zero or a positive integer. Some or all of the C1 to CN may be the same value or different values. In addition, at least one of C1, C2, ... CN may be a predetermined value in the encoder and the decoder. In addition, at least one of C1, C2, ... CN may be determined based on an encoding parameter of each corresponding block. In addition, at least one of C1, C2, ... CN may be entropy encoded / decoded.

Also, for example, intra prediction modes included in the MPM_LIST_1 list may be expressed as MPM_LIST_1_MODE_1, MPM_LIST_1_MODE_2, ..., MPM_LIST_1_MODE_C1.

In order to not include overlapping intra prediction modes between MPM lists, the intra prediction mode included in the late order MPM list can be used to confirm the redundancy with the intra prediction modes included in the fast order MPM list. have. If there are overlapping intra prediction modes after checking redundancy, the intra prediction modes may be excluded from the MPM list. In addition, after the overlapping modes are excluded, a predetermined intra prediction mode may be added to the corresponding MPM list.

The redundancy check for the modes included in the MPM lists may be performed in constructing a plurality of MPM lists. Alternatively, the redundancy check may be performed after configuring all the plurality of MPM lists used. Alternatively, the redundancy check may be performed whenever the intra prediction mode is included in the MPM list.

For example, when the MPM_LIST_1 of the current block has C1 intra prediction modes, the intra prediction modes of the MPM_LIST_1 may be MPM_LIST_1_MODE_1, MPM_LIST_1_MODE_2, ..., MPM_LIST_1_MODE_C1 which do not overlap each other.

For example, when the MPM_LIST_2 includes C2 intra prediction modes that do not overlap each other, it may be checked whether the intra prediction modes included in the MPM_LIST_2 overlap with at least one of the intra prediction modes included in the MPM_LIST_1.

When the intra prediction mode MPM_LIST_2_MODE_X included in the MPM_LIST_2 overlaps with the mode included in the MPM_LIST_1, the overlapping intra prediction mode MPM_LIST_2_MODE_X may be excluded from the MPM_LIST_2. Here, MPM_LIST_2_MODE_X may be at least one of MPM_LIST_2_MODE_1, MPM_LIST_2_MODE_2, ..., MPM_LIST_2_MODE_C2.

For example, when at least one intra prediction mode is excluded from the MPM_LIST_2, at least one of predetermined intra prediction modes may be included in the MPM_LIST_2. In this case, at least one of the predetermined intra prediction modes included in MPM_LIST_2 may not overlap with at least one of the intra prediction modes included in MPM_LIST_1. Alternatively, at least one of the predetermined intra prediction modes included in MPM_LIST_2 may not overlap with all of the intra prediction modes included in MPM_LIST_1.

Predetermined intra prediction modes added to supplement the overlapping intra prediction modes are, for example, INTRA_PLANAR, INTRA_DC, horizontal mode, vertical mode, 45 degree mode, 135 degree mode, 225 degree mode MPM_LIST_2_MODE_X ± delta, INTRA_DM, It may include at least one or more of intra prediction modes including INTRA_LM. Here, INTRA_DM may mean an intra prediction mode that determines the intra prediction mode of the chrominance screen to be identical to the intra prediction mode. In addition, INTRA_LM may refer to an intra prediction mode that generates at least one of the chrominance prediction / residual / recovery blocks based on at least one of the luminance prediction / residual / recovery blocks. Also, delta may be a positive integer.

For example, the predetermined intra prediction mode MPM_LIST_2_MODE_X ± delta may be included in the MPM_LIST_2 while continuously increasing the delta value from 1 to 1 until the number of intra prediction modes included in the MPM_LIST_2 is C2. Alternatively, the predetermined intra prediction modes are arranged in a predetermined order, and at least one or more of the intra intra prediction modes are assigned to the MPM_LIST_2 in this order until the number of intra prediction modes included in the MPM_LIST_2 is C2. Can be included.

For example, when the MPM_LIST_3 of the current block includes C3 intra picture prediction modes that do not overlap each other, each intra picture prediction mode included in the MPM_LIST_3 overlaps with at least one of the intra picture prediction modes included in the MPM_LIST_1 and the MPM_LIST_2. You can check if

When the intra prediction mode MPM_LIST_3_MODE_X included in the MPM_LIST_3 overlaps with the mode included in the MPM_LIST_1 or the MPM_LIST_2, the overlapping intra prediction mode MPM_LIST_3_MODE_X may be excluded from the MPM_LIST_3. Here, MPM_LIST_3_MODE_X may be at least one of MPM_LIST_3_MODE_1, MPM_LIST_3_MODE_2, ..., MPM_LIST_3_MODE_C3.

For example, when at least one intra prediction mode is excluded from the MPM_LIST_3, at least one of predetermined intra prediction modes may be included in the MPM_LIST_3. In this case, at least one of the predetermined intra prediction modes included in the MPM_LIST_3 may not overlap with at least one of the intra prediction modes included in the MPM_LIST_1 and the MPM_LIST_2. Alternatively, at least one of the predetermined intra prediction modes included in MPM_LIST_3 may not overlap with all of the intra prediction modes included in MPM_LIST_1 and MPM_LIST_2.

For example, the predetermined intra prediction mode MPM_LIST_3_MODE_X ± delta may be included in the MPM_LIST_3 while the delta value is continuously increased from 1 to 1 until the number of intra prediction modes included in the MPM_LIST_3 is C3. Alternatively, the predetermined intra prediction modes are arranged in a predetermined order, and at least one or more of the intra prediction modes in the order are assigned to the MPM_LIST_3 until the number of intra prediction modes included in the MPM_LIST_3 is C3. Can be included.

For example, when the MPM_LIST_K of the current block includes CK intra-picture prediction modes that do not overlap each other, the intra-prediction modes included in the MPM_LIST_K are in-screen of MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_ (K-1). It may be checked whether the data overlaps with at least one of the prediction modes. Here, K may be a positive integer less than or equal to N, the maximum number of MPM lists that the current block may have.

If the on-screen prediction mode MPM_LIST_K_MODE_X included in MPM_LIST_K overlaps with the mode included in at least one of MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_ (K-1), the corresponding in-picture prediction mode MPM_LIST_K_MODE_X is excluded from MPM_LIST_K. Can be. Here, MPM_LIST_K_MODE_X may be at least one of MPM_LIST_K_MODE_1, MPM_LIST_K_MODE_2, ..., MPM_LIST_K_MODE_CK.

For example, when at least one intra prediction mode is excluded from the MPM_LIST_K, at least one of predetermined intra prediction modes may be included in the MPM_LIST_K. In this case, at least one of the predetermined intra prediction modes included in MPM_LIST_K may not overlap with at least one of the intra prediction modes included in MPM_LIST_1, MPM_LIST_2, ..., and MPM_LIST_ (K-1). have. Alternatively, at least one of the predetermined intra prediction modes included in MPM_LIST_K may not overlap with all intra prediction modes included in MPM_LIST_1, MPM_LIST_2, ..., and MPM_LIST_ (K-1).

For example, to supplement the intra prediction mode excluded from MPM_LIST_K, the intra prediction included in MPM_LIST_1, MPM_LIST_2, ..., and MPM_LIST_ (K-1) for at least one or more of the predetermined intra prediction modes. If there is a predetermined intra prediction mode that does not overlap at least one or all of the modes, the predetermined intra prediction mode may be added as the intra prediction mode of MPM_LIST_K.

For example, the predetermined intra prediction mode MPM_LIST_K_MODE_X ± delta may be included in the MPM_LIST_K, while the delta value is continuously increased from 1 to 1 until the number of intra prediction modes included in the MPM_LIST_K becomes CK. Alternatively, the predetermined intra prediction modes are arranged in a predetermined order, and at least one or more of the intra prediction modes in the order are assigned to the MPM_LIST_K until the number of intra prediction modes included in the MPM_LIST_K becomes CK. Can be included.

Among the intra prediction modes included in each of the N MPM lists, the N MPM list is used to derive the intra prediction mode of the current block or entropy encode / decode the intra prediction mode of the current block. An indicator (MPM flag) indicating whether the same intra prediction mode as the intra prediction mode of the current block exists may be entropy encoded / decoded for each of the N MPM lists.

For example, when N MPM lists are used, up to N indicators may be encoded / decoded, such as MPM_FLAG_1, MPM_FLAG_2, ... MPM_FLAG_N, for each MPM list. Alternatively, at most (N-1) indicators may be encoded / decoded, in which case, the indicator for one MPM list in which the indicator is not encoded / decoded may be the value of some or all of the (N-1) indicators. Can be derived based on. For example, the indicator may not be encoded / decoded for any of the N MPM lists (eg, the last MPM list in a predetermined order). When the same mode as the intra prediction mode of the current block among the intra prediction modes in the specific MPM list exists, the indicator for the specific MPM list may have a first value, and the second mode when the same mode does not exist. It can have a value. In this case, the first value may be 1 and the second value may be 0. That is, the indicator may be flag information.

In addition, when the indicator for a specific MPM list of the N indicators has a first value, all of the indicators for the other MPM lists except for the indicator for the specific MPM list may have a second value.

In addition, when the indicator for the K-th MPM list among the N indicators has a first value, the indicators for the K + 1-th MPM list to the N-th MPM list may not be entropy encoded / decoded. In this case, K may be a positive integer greater than or equal to 1 and less than or equal to N.

If there is an intra prediction mode identical to the intra prediction mode of the current block among the intra prediction modes included in the specific MPM list among the N MPM lists, the position or order of the intra prediction mode in the specific MPM list Entropy encoding may be applied to index information (MPM index) for. In addition, the index information may be entropy decoded to identify an intra prediction mode that is identical to an intra prediction mode of the current block among intra prediction modes included in a specific MPM list. The index information may be entropy encoded / decoded by a fixed length code or a variable length code. In addition, the index information may be used to derive an intra prediction mode of the current block.

If there is no intra prediction mode identical to the intra prediction mode of the current block among the intra prediction modes included in the N MPM lists, the encoder determines the remaining intra prediction mode of the current block. Entropy can be coded. In this case, the residual intra prediction mode may be used to identify the intra prediction mode of the current block that is not included in at least one of the MPM lists. Alternatively, the residual intra prediction mode may be used to identify the intra prediction mode of the current block that is not included in all candidate intra prediction modes of the MPM lists.

In this case, when the total number of intra prediction modes is Y, and the sum of the number of all intra prediction modes included in the N MPM lists for the current block is X, Y X intra predictions minus X is obtained. Among the modes, entropy encoding may be performed on the remaining intra prediction mode indicating the same intra prediction mode as the intra prediction mode of the current block. In this case, the total X intra prediction modes included in the N MPM lists may be arranged based on at least one or more of the size, angle, order, and identification number of the intra prediction modes. The sorting can be ascending sorting or descending sorting. The aligned X intra prediction modes may be compared with the intra prediction modes of the current block. As a result of the comparison, when the intra prediction mode of the current block is larger, a specific value may be subtracted from the intra prediction mode value of the current block. The specific value may be 1.

Or, for example, the mode having the largest reference value of the sorted X intra prediction modes (eg, at least one of the size, angle, order, and identification number of the intra prediction mode) and the intra prediction of the current block. The modes can be compared. As a result of the comparison, when the intra prediction mode value of the current block is larger, a specific value may be subtracted from the intra prediction mode value of the current block.

In addition, the mode having the second largest reference value among the sorted X intra prediction modes may be compared with the intra prediction mode of the current block subtracted by the specific value. As a result of the comparison, when the intra prediction mode of the subtracted current block is larger, the specific value may be further subtracted from the sub intra prediction mode value of the current block.

Subtraction based on the comparison may be repeated until the mode having the smallest reference value among the sorted X intra prediction modes. Finally, the intra prediction mode value of the subtracted current block may be entropy encoded into the residual intra prediction mode.

The intra intra prediction mode of the current block may be entropy decoded and used to identify the intra intra prediction mode that is the same as the intra prediction mode of the current block among intra prediction modes not included in the N MPM lists. In this case, when the total number of intra prediction modes is Y and the sum of the total intra prediction modes of the N MPM lists for the current block is X, the number of intra prediction modes is excluded from Y by X. It is possible to entropy decode a residual intra prediction mode indicating the same intra prediction mode as the intra prediction mode of the current block among the YX intra prediction modes.

After entropy decoding the residual intra prediction mode, the X intra prediction modes may be aligned based on at least one or more of the size, angle, order, and identification number of the intra prediction mode. The sorting can be ascending sorting or descending sorting. The entropy decoded residual intra prediction mode may be compared with the X intra prediction modes. As a result of the comparison, when the entropy decoded residual picture prediction mode value is greater than or equal to, the entropy decoded residual picture prediction mode value may be increased to a specific value. The specific value may be 1.

Or, for example, the mode having the smallest reference value of the sorted X intra prediction modes (eg, at least one of the size, angle, order, and identification number of the intra prediction mode) and the decoded residual intra prediction The modes can be compared. As a result of the comparison, when a value of the prediction mode in the residual picture is greater than or equal to a value, a specific value may be added to the prediction mode value in the remaining picture.

In addition, the mode having the second smallest reference value among the sorted X intra prediction modes may be compared with the residual intra prediction mode added to the specific value. As a result of the comparison, when the prediction mode within the added residual picture is larger than or equal to the prediction mode, the specific value may be additionally added from the added residual prediction mode value.

The addition based on the comparison may be repeated until the mode having the largest reference value among the sorted X intra prediction modes. Finally, the added residual intra prediction mode value may be entropy decoded into the intra prediction mode of the current block.

A method of entropy encoding / decoding an intra prediction mode of a current block using the N MPM lists may be performed as described below.

First, an embodiment in the case where one MPM list is used for the current block will be described.

If the encoder has the same intra prediction mode as the intra prediction mode of the current block among the intra prediction modes included in the MPM_LIST_1, the encoder determines whether the same intra prediction mode as the intra prediction mode of the current block exists in the MPM_LIST_1. Entropy encoding may be performed using the indicator MPM_FLAG_1 indicating whether the first value is the first value. When MPM_FLAG_1 is the first value, the index information MPM_IDX_1 may be additionally entropy encoded.

If the encoder does not have an intra prediction mode that is identical to the intra prediction mode of the current block among the intra prediction modes included in the MPM_LIST_1, the encoder is configured to have the same intra prediction mode as the intra prediction mode of the current block in the MPM_LIST_1. An indicator MPM_FLAG_1 indicating whether there is an entropy may be encoded with a second value. When MPM_FLAG_1 is the second value, the remaining intra prediction mode REM_MODE may be additionally entropy encoded.

The decoder may entropy decode the indicator MPM_FLAG_1 indicating whether the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_1. When MPM_FLAG_1 is the first value, the index information MPM_IDX_1 may be additionally entropy decoded to derive an intra prediction mode of the current block.

When MPM_FLAG_1 is the second value, the remaining intra prediction mode REM_MODE may be additionally entropy decoded to derive the intra prediction mode of the current block.

Hereinafter, an embodiment of using two MPM lists for the current block will be described.

If the encoder has the same intra prediction mode as the intra prediction mode of the current block among the intra prediction modes included in the MPM_LIST_1 and the MPM_LIST_2, the same intra prediction mode as the intra prediction mode of the current block is one of the MPM_LIST_1 and the MPM_LIST_2. It is possible to entropy encode the indicators MPM_FLAG_1 and MPM_FLAG_2 indicating which MPM lists exist. When the intra prediction mode of the current block exists in MPM_LIST_1, MPM_FLAG_1 may be a first value and MPM_FLAG_2 may be a second value. In this case, MPM_IDX_1, which is index information of the MPM_LIST_1, may be additionally entropy encoded. Alternatively, when the intra prediction mode of the current block exists in MPM_LIST_2, MPM_FLAG_1 may be the second value and MPM_FLAG_2 may be the first value. In this case, MPM_IDX_2, which is index information of the MPM_LIST_2, may be additionally entropy encoded.

When the encoder does not have the same intra prediction mode as the intra prediction mode of the current block among the intra prediction modes included in the MPM_LIST_1 and the MPM_LIST_2, the encoder may have the same intra prediction modes as the MPM_LIST_1 and the intra prediction modes of the current block. Entropy encoding may be performed using the indicators MPM_FLAG_1 and MPM_FLAG_2 indicating whether any MPM list in the MPM_LIST_2 is present as a second value. When MPM_FLAG_1 and MPM_FLAG_2 are the second values, REM_MODE, which is the prediction mode in the residual picture, may be additionally entropy encoded.

The decoder may entropy decode the indicators MPM_FLAG_1 and MPM_FLAG_2 indicating whether the same intra prediction mode as the intra prediction mode of the current block exists in the MPM list of the MPM_LIST_1 and the MPM_LIST_2. If MPM_FLAG_1 is the first value and MPM_FLAG_2 is the second value, the intra prediction mode of the current block is present in MPM_LIST_1, and the decoder additionally entropy decodes MPM_IDX_1, which is index information for the MPM_LIST_1, to determine the intra prediction mode of the current block. Can be induced. Alternatively, when MPM_FLAG_1 is the second value and MPM_FLAG_2 is the first value, the intra prediction mode of the current block is present in the MPM_LIST_2, and the decoder additionally entropy decodes the MPM_IDX_2, which is index information for the MPM_LIST_2, to predict the intra prediction of the current block. Induce mode. Alternatively, when MPM_FLAG_1 and MPM_FLAG_2 are the second values, the decoder may additionally entropy decode the REM_MODE, which is the residual intra prediction mode, to derive the intra prediction mode of the current block. At this time, the case where both MPM_FLAG_1 and MPM_FLAG_2 are the first value may not occur.

Hereinafter, another embodiment of using two MPM lists for the current block will be described.

As shown in the example of Table 5, the encoder according to at least one method of configuring the plurality of MPM lists, in-screen prediction of the current block of the intra prediction modes included in each MPM list from MPM_LIST_1 to MPM_LIST_2 By sequentially checking whether the same intra prediction mode as the mode exists, the intra prediction mode of the current block may be entropy encoded.

For example, when the same intra prediction mode as the intra prediction mode of the current block exists in the MPM_LIST_1, the MPM_FLAG_1 may be entropy encoded with the first value. In this case, MPM_IDX_1, which is index information of the MPM_LIST_1, may be additionally entropy encoded.

For example, when the same intra prediction mode as the intra prediction mode of the current block does not exist in the MPM_LIST_1, the MPM_FLAG_1 may be entropy encoded with the second value. In this case, when the same intra prediction mode as the intra prediction mode of the current block exists in the MPM_LIST_2 (where MPM_FLAG_1 is the second value), the MPM_FLAG_2 may be entropy encoded with the first value. In this case, MPM_IDX_2, which is index information of the MPM_LIST_2, may be additionally entropy encoded.

For example, if the same intra prediction mode as the intra prediction mode of the current block does not exist in the MPM_LIST_1 and the MPM_LIST_2, the MPM_FLAG_1 and the MPM_FLAG_2 may be entropy encoded with the second value. At this time (when MPM_FLAG_1 and MPM_FLAG_2 are the second values), REM_MODE, which is the prediction mode of the residual picture, may be additionally entropy encoded.

As shown in the example of Table 5, the decoder uses the MPM_FLAG_1 and / or MPM_FLAG_2 indicators indicating whether the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_1 and MPM_LIST_2. Entropy decoding may be performed sequentially according to at least one method of constituting sequences.

For example, when MPM_FLAG_1 is entropy decoded to a first value, the intra prediction mode of the current block is present in MPM_LIST_1, and MPM_IDX_1, which is index information for the MPM_LIST_1, is additionally entropy decoded to determine the intra prediction mode of the current block. Can be induced.

For example, when MPM_FLAG_1 is entropy decoded to a second value, MPM_FLAG_2 may be entropy decoded. When the decoded MPM_FLAG_2 is the first value, the intra prediction mode of the current block is present in the MPM_LIST_2, and MPM_IDX_2, which is index information of the MPM_LIST_2, is additionally entropy decoded to derive the intra prediction mode of the current block.

For example, when MPM_FLAG_1 and MPM_FLAG_2 are entropy decoded to a second value, REM_MODE, which is the residual intra prediction mode, may be additionally entropy decoded to derive the intra prediction mode of the current block. At this time, the step of checking whether the MPM_FLAG_1 and the MPM_FLAG_2 is the first value or the second value may be sequentially performed.

Hereinafter, an embodiment of using N MPM lists for the current block will be described.

The encoder includes MPM_LIST_1, MPM_LIST_2,... If there are intra prediction modes that are identical to the intra prediction modes of the current block among the intra prediction modes included in, and MPM_LIST_N, the intra prediction modes that are identical to the intra prediction modes of the current block are MPM_LIST_1, MPM_LIST_2,... The indicators MPM_FLAG_1, MPM_FLAG_2,... Indicating which MPM list is among. , And MPM_FLAG_N may be entropy encoded. If the intra prediction mode of the current block exists in MPM_LIST_1, MPM_FLAG_1 is the first value and MPM_FLAG_2,... Except for MPM_FLAG_1. , And MPM_FLAG_N may be the second value. In this case, MPM_IDX_1, which is index information of the MPM_LIST_1, may be additionally entropy encoded.

Or, if the intra prediction mode of the current block exists in MPM_LIST_2, MPM_FLAG_2 is the first value and MPM_FLAG_1,... Except for MPM_FLAG_2. , And MPM_FLAG_N may be the second value. In this case, MPM_IDX_2, which is index information of the MPM_LIST_2, may be additionally entropy encoded.

Or, if the intra prediction mode of the current block exists in MPM_LIST_N, MPM_FLAG_N is the first value and MPM_FLAG_1, except MPM_FLAG_N,... , And MPM_FLAG_ (N-1) may be the second value. In this case, MPM_IDX_N, which is index information of the MPM_LIST_N, may be additionally entropy encoded.

The encoder includes MPM_LIST_1, MPM_LIST_2,... If the intra prediction modes identical to the intra prediction modes of the current block do not exist among the intra prediction modes included in, and MPM_LIST_N, the intra prediction modes that are identical to the intra prediction modes of the current block are MPM_LIST_1, MPM_LIST_2,... The indicators MPM_FLAG_1, MPM_FLAG_2,... Indicating which MPM list is among. , And MPM_FLAG_N may be entropy encoded with a second value. MPM_FLAG_1, MPM_FLAG_2,... And, when MPM_FLAG_N is the second value, REM_MODE, which is the prediction mode in the residual picture, may be additionally entropy encoded.

The decoder has the same intra prediction modes as MPM_LIST_1, MPM_LIST_2,... The indicators MPM_FLAG_1, MPM_FLAG_2,... Indicating which MPM list is among. , And MPM_FLAG_N can be entropy decoded. MPM_FLAG_1 is the first value, except for MPM_FLAG_1, MPM_FLAG_2,... If, and MPM_FLAG_N are the second values, the intra prediction mode of the current block may exist in MPM_LIST_1. In this case, MPM_IDX_1, which is index information of the MPM_LIST_1, may be additionally entropy decoded to derive an intra prediction mode of the current block.

Alternatively, MPM_FLAG_2 is the first value and MPM_FLAG_1, except MPM_FLAG_2,... If, and MPM_FLAG_N are the second values, the intra prediction mode of the current block may be present in MPM_LIST_2. In this case, MPM_IDX_2, which is index information of the MPM_LIST_2, may be additionally entropy decoded to derive an intra prediction mode of the current block.

Or MPM_FLAG_1, where MPM_FLAG_N is the first value and excludes MPM_FLAG_N,... , And MPM_FLAG_ (N-1) are the second values, the intra prediction mode of the current block may be present in MPM_LIST_N. In this case, MPM_IDX_N, which is index information of the MPM_LIST_N, may be additionally entropy decoded to derive an intra prediction mode of the current block.

Or MPM_FLAG_1, MPM_FLAG_2,... If, and MPM_FLAG_N is the second value, REM_MODE, which is the residual intra prediction mode, may be additionally entropy decoded to derive the intra prediction mode of the current block. At this time, MPM_FLAG_1, MPM_FLAG_2,... It may not occur when,, and MPM_FLAG_N are both first values.

Hereinafter, another embodiment of using N MPM lists for the current block will be described.

As shown in the example of Table 6, the coder may use the following methods: MPM_LIST_1, MPM_LIST_2,... The intra prediction mode of the current block may be entropy encoded by sequentially checking whether the intra prediction modes identical to the intra prediction modes of the current block are present among the intra prediction modes included in each of the MPM_LIST_N.

For example, the same intra prediction modes as the intra prediction modes of the current block are set to MPM_LIST_1, MPM_LIST_2,... , MPM_FLAG_1, MPM_FLAG_2, ... if not present in MPM_LIST_ (N-1). , MPM_FLAG_ (N-1) may be entropy encoded with a second value. In this case, when the same intra prediction mode as the intra prediction mode of the current block exists in the MPM_LIST_N (MPM_FLAG_1, MPM_FLAG_2, ..., MPM_FLAG_ (N-1) is the second value), the MPM_FLAG_N is entropy coded to the first value. Can be. In this case, MPM_IDX_N, which is index information of the MPM_LIST_N, may be additionally entropy encoded.

For example, the same intra prediction modes as the intra prediction modes of the current block are set to MPM_LIST_1, MPM_LIST_2,... , MPM_FLAG_1, MPM_FLAG_2,… if not present in MPM_LIST_N. , MPM_FLAG_N may be entropy encoded with a second value. In this case, REM_MODE, which is the prediction mode in the remaining picture, may be additionally entropy encoded.

As shown in the example of Table 6, the decoder has the same intra prediction modes as MPM_LIST_1, MPM_LIST_2,... , The indicators indicating which MPM list among the MPM_LIST_Ns is present in the MPM_FLAG_1, MPM_FLAG_2,... At least one or more of MPM_FLAG_N may be sequentially entropy decoded according to at least one method of orderings of the plurality of MPM lists.

For example, when MPM_FLAG_1 is entropy decoded to the first value, the intra prediction mode of the current block is present in MPM_LIST_1 and MPM_IDX_1, which is index information for the MPM_LIST_1, is additionally entropy decoded to derive the intra prediction mode of the current block. can do.

For example, MPM_FLAG_1, MPM_FLAG_2,... When MPM_FLAG_ (N-1) is entropy decoded to a second value, MPM_FLAG_N may be entropy decoded. When the decoded MPM_FLAG_N is the first value, the intra prediction mode of the current block is present in the MPM_LIST_N, and MPM_IDX_N, which is index information of the MPM_LIST_N, is additionally entropy decoded to derive the intra prediction mode of the current block.

For example, MPM_FLAG_1, MPM_FLAG_2,... When MPM_FLAG_N is entropy decoded to a second value, REM_MODE, which is the residual intra prediction mode, may be additionally entropy decoded to derive the intra prediction mode of the current block. At this time, MPM_FLAG_1, MPM_FLAG_2,... The step of checking whether the MPM_FLAG_N is the first value or the second value may be sequentially performed.

The MPM list may be specified in the form of a flag as in the above-described MPM_FLAG_N, or may be encoded / decoded in the form of an index for specifying one of the plurality of MPM lists. Information on whether to use the MPM-based intra prediction mode derivation method in the current block (or the current slice, the current picture, the current sequence, etc.) may be encoded / decoded. The index may be encoded / decoded when an MPM-based intra prediction mode derivation method is used according to the information. At least one of the number or types of MPM lists belonging to the plurality of MPM lists may be fixed pre-defined to the encoder / decoder, and may be variable based on parameters related to the size, depth, shape, position, etc. of the current block / peripheral block. It may be determined as. For example, the number of MPM lists pre-defined in the encoder / decoder may be one, two, three or more values. The maximum number of intra prediction modes belonging to each MPM list may be forced to be the same. In this case, the maximum number may be fixed pre-committed to the encoder / decoder, or may be signaled in a predetermined unit (eg, sequence, picture, slice, block, etc.). If the number of intra prediction modes belonging to a specific MPM list is smaller than the maximum number, a predetermined mode may be added. In this case, the added mode may be a pre-appointed default mode or an intra prediction mode belonging to another MPM list. However, a mode that is not the same as the intra prediction mode included in the specific MPM list may be added. The redundancy check may be omitted between each MPM list. Any one of the MPM lists may share at least one same intra prediction mode with another MPM list.

The encoder may configure a plurality of MPM lists from MPM_LIST_1 to MPM_LIST_N in accordance with at least one method of order of configuring the plurality of MPM lists. The number of prediction modes in the total candidate screen of the N MPM lists may be K. Where N and K may be positive integers.

For example, MPM_LIST_combined may be configured to include prediction modes in the candidate screen that are less than or equal to K among the prediction modes in the candidate pictures of the N MPM lists.

For example, if an intra prediction mode identical to the intra prediction mode of the current block exists in MPM_LIST_combined, the indicator MPM_FLAG_combined indicating whether the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_combined is the first parameter. It can be entropy coded as a value. In this case, MPM_IDX_combined, which is index information of the MPM_LIST_combined, may be additionally entropy encoded.

If the same intra prediction mode as the intra prediction mode of the current block does not exist in the MPM_LIST_combined, the MPM_FLAG_combined may be entropy encoded with the second value. When MPM_FLAG_combined is the second value, REM_MODE, which is the prediction mode in the residual picture, may be additionally entropy encoded.

The decoder may entropy decode the indicator MPM_FLAG_combined indicating whether the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_combined. When MPM_FLAG_combined is the first value, the index information MPM_IDX_combined may be additionally entropy decoded to derive an intra prediction mode of the current block. When MPM_FLAG_combined is the second value, REM_MODE, which is the residual intra prediction mode, may be additionally entropy decoded to derive the intra prediction mode of the current block.

According to the present invention, the intra prediction mode of the current block may be derived by encoding / decoding. In this case, the intra prediction mode of the current block may be entropy encoded / decoded without using the intra prediction mode of the neighboring block. have.

According to the present invention, in order to derive an intra prediction mode of a current block, an intra prediction mode of another color component may be used. For example, when the current block is a chrominance block, an intra prediction mode of one or more luminance corresponding blocks corresponding to the chrominance target block may be used to derive an intra prediction mode for the chrominance block. In this case, the luminance corresponding block may be determined based on at least one of a size, a shape, or an encoding parameter of the chrominance block. Alternatively, the luminance corresponding block may be determined based on at least one of a size, a shape, or an encoding parameter of the luminance block.

In the example illustrated in FIG. 15, the luminance corresponding block corresponding to the color difference block may be at least one of A, B, C, and D.

For example, the intra prediction mode of the luminance block A corresponding to the (0, 0) sample position of the chrominance block may be derived into the intra prediction mode of the chrominance block.

For example, the intra prediction mode of the luminance block D corresponding to the (nS / 2, nS / 2) sample position corresponding to the center of the chrominance block may be derived as the intra prediction mode of the chrominance block.

For example, an intra prediction mode of the chrominance block may be derived by using a combination of one or more intra prediction modes in the luminance block corresponding to the size of the chrominance block. For example, a mode corresponding to an average of intra prediction modes of luminance blocks A and D corresponding to the (0, 0) sample position of the chrominance block and the (nS-1, nS-1) sample positions is defined in the screen of the chrominance block. Can lead to prediction mode. Alternatively, a mode corresponding to an average of intra prediction modes of blocks A, B, C, and D in the luminance block corresponding to the size of the chrominance block may be derived as the intra prediction mode of the chrominance block. Instead of the mean, one or more of various statistical values may be used, including maximum, minimum, mode, median and weighted average.

For example, an intra prediction mode of the color difference block may be derived based on at least one of the size, shape, or depth information of the luminance block. For example, an intra prediction mode of a relatively large D is obtained by comparing the magnitudes of luminance blocks A and D corresponding to (0, 0) sample positions of the chrominance block and (nS / 2, nS / 2) sample positions. Can be derived into the on-screen prediction mode. Alternatively, when the size of the luminance block corresponding to the predetermined position of the chrominance block is greater than or equal to the size of the chrominance block, the intra prediction mode of the chrominance block may be derived by using the intra prediction mode of the corresponding luminance block. .

For example, an intra prediction mode of the color difference block may be derived based on at least one of the size, shape, or depth information of the color difference block. For example, when the size of the chrominance block falls within a predetermined range, the intra prediction mode of the luminance block corresponding to the (0, 0) sample position of the chrominance block may be derived into the intra prediction mode of the chrominance block. Alternatively, when the size of the chrominance block falls within a predetermined range, a large luminance block is compared by comparing the sizes of the luminance blocks corresponding to the (0, 0) sample positions of the chrominance block and the (nS / 2, nS / 2) sample positions. Intra-prediction mode of may be derived to the intra-prediction mode of the color difference block. Alternatively, when the shape of the chrominance block is rectangular, the intra prediction mode of the luminance block corresponding to the position corresponding to the center of the chrominance block may be derived as the intra prediction mode of the chrominance block.

For example, when the current block is divided into lower or sub blocks, the intra prediction mode for each of the divided sub blocks may be obtained by using at least one or more methods of deriving an intra prediction mode for the current block. Can be induced.

The size of the current block and the size of the sub block may be M × N. M and N may be the same or different positive integers. For example, the current block or subblock is CTU, CU, SU (signalling unit), QTMax, QTMin, BTMax, BTMin, 4x4, 8x8, 16x16, 32x32, 64x64, 128x128, 256x256, 4x8, 8x16, 16x8, 32x64, 32x8 , 4x32 and the like. In this case, QTMax and QTMin may represent the maximum and minimum sizes that can be split into a quart tree, respectively, and BTMax and BTMin may represent the maximum and minimum sizes that can be split into a binary tree. Hereinafter, the size of the sub block may mean a partition structure of the sub block.

The size of the sub block may vary depending on the size of the current block. For example, the size corresponding to N equal to the horizontal and vertical sizes of the current block may be the size of the sub block. In this case, N may be a positive integer and may be at least one of 2, 4, 8, 16, 32, and 64. For example, when the size of the current block is 32x32 and the equal N for each of the horizontal and the vertical is 4, the size of the subblock may be 8x8.

Alternatively, the size of the sub block may be a predetermined fixed size regardless of the size of the current block. For example, the size of the sub block may be the minimum size regardless of the size of the current block, for example, 4x4.

Alternatively, the size of the sub block may be determined based on the partition structure of the neighboring block of the current block. For example, when adjacent neighboring blocks are divided, the size of the sub block may be determined by dividing the current block.

The size of the sub block may be determined based on an intra prediction mode of a neighboring block of the current block. For example, the size of the sub block may be determined by dividing the sub block based on a boundary where the intra prediction mode of the neighboring block is different.

The size of the sub block may be determined based on encoding parameters of neighboring blocks. For example, the sub-block may be divided and determined based on whether the neighboring block is an intra coded block or an inter coded block.

At least one or more of the size of the current block, the size of the sub block, and an N equal value for the current block may be fixed to a predetermined size.

For example, when the fixed predetermined size of the current block is 16x16, if the size of the current block is 16x16, the current block may be divided into sub-blocks and induce an intra prediction mode for each sub-block.

For example, when the fixed predetermined size of the current block is CTU and the N equal value is 4, if the size of the current block is CTU, the intra prediction mode is performed in units of sub-blocks divided into 4 equal parts by the width and length of the CTU. Can be induced.

The one or more sub blocks may be divided into blocks of smaller size. For example, when the size of the current block is 32x32 and the size of the subblock is 16x16, one or more subblocks may be divided into smaller blocks such as 8x8, 4x4, 16x8, 4x16, and the like.

At least one or more of the size of the current block, the size of the sub block, and an N equal value for the current block may be encoded / decoded.

The partition structure of the sub block with respect to the current block may be encoded / decoded. In this case, the divided subblocks may have various sizes and / or shapes. In addition, an intra prediction mode may be derived for each sub block.

An indicator (eg, a flag) indicating that the intra prediction mode of the current block is derived using the intra prediction mode of the neighboring block may be encoded / decoded. For example, the indicator may be Neighboring mode dependent intra prediction (NDIP_flag). The indicator may be encoded / decoded for at least one unit of the current block or subblock. The indicator may be encoded / decoded only when the size of the current block or sub block corresponds to a predetermined size or a predetermined size range. The predetermined size may be 64x64 or BTMax, for example. As described above, the current block may be divided into a plurality of sub blocks. The partition structure of the subblock may be predefined or determined by encoding / decoding.

When NDIP_flag for the current block is 1, the intra prediction mode for the current block or each sub block within the current block may be derived using the intra prediction mode of the neighboring block. In this case, at least one or more of prev_intra_luma_pred_flag, mpm_idx, rem_intra_luma_pred_mode, intra_chroma_pred_mode, split_flag, QB_flag, quadtree_flag, binarytree_flag, and Btype_flag of the current block and / or subblock may not be encoded or decoded.

For example, when the NDIP_flag of the current block is 1, after decoding the intra prediction mode for the current block, the decoded intra prediction mode and the intra prediction mode of the neighboring block are used for each sub block. Intra prediction mode can be derived. In this case, at least one or more of prev_intra_luma_pred_flag, mpm_idx, rem_intra_luma_pred_mode, intra_chroma_pred_mode, split_flag, QB_flag, quadtree_flag, binarytree_flag, and Btype_flag of the subblock may not be encoded / decoded.

When the NDIP_flag of the current block is 0, information related to at least one or more of the intra prediction mode of the current block or the sub-block and the split information of the sub-block may be encoded / decoded.

The intra prediction mode for the first sub block among the sub blocks in the current block may be derived in a manner different from the remaining sub blocks. The first sub block may be one of a plurality of sub blocks in the current block. For example, the first sub block may be the first sub block in the Z scan order.

The intra prediction mode of the first subblock may mean an initial mode. For example, when the intra prediction mode for the sub block is derived as an average of the intra prediction modes of the left and upper blocks of each sub block, the initial mode may be derived in another way. Another method for deriving the initial mode may be at least one of a method of deriving an intra prediction mode according to the present invention.

For example, a mode existing in the Nth (eg, first) of the MPM list may be derived as the initial mode. Alternatively, a mode that most frequently occurs among intra prediction modes of one or more blocks existing around the current block may be derived as the initial mode. Alternatively, the intra prediction mode encoded / decoded with respect to the current block may be derived as the initial mode. Alternatively, the intra prediction mode encoded / decoded with respect to the first subblock may be derived as the initial mode.

In deriving an intra prediction mode for a sub block in a current block, an intra prediction mode of one or more sub blocks may be derived in any order. In this case, the random order may be a scanning order and may correspond to at least one of raster scan, upright scan, vertical scan, horizontal scan, diagonal scan, and zigzag scan. The number of subblocks for inducing the intra prediction mode according to the scanning order may be one or more. The random order may be adaptively determined according to the intra prediction mode of the neighboring block.

First, it may be determined whether the size of the current block corresponds to a predetermined size (S1610). The predetermined size may be determined by the width or length of the current block. For example, the determination of step S1610 may be performed according to whether the length of the current block is the length that can be divided into sub-blocks.

For example, in the case where the horizontal length and the vertical length of the current block are equal to each other, the size of the current block is greater than or equal to the predetermined length when N equal lengths of each of the horizontal and vertical lengths are greater than or equal to a predetermined length. It may correspond to the size of. For example, when N is 4 and the arbitrary length is 4, if the current block is at least one of 256x256, 128x128, 64x64, 32x32, and 16x16, the size of the current block may correspond to the predetermined size. .

For example, in the case of a rectangle having different lengths and widths of the current block, the smaller length of M equal to the larger length of the width and length and the N equal to the smaller length is greater than the arbitrary length. In the same case, the size of the current block may correspond to the predetermined size. For example, if M is 4, N is 2, and any length is 4, the current block is 128x64, 64x128, 128x32, 32x128, 128x16, 16x128, 128x8, 8x128, 64x32, 32x64, 64x16, 16x64, 64x8 If at least one of 8x64, 32x16, 16x32, 32x8, 8x32, 16x8, and 8x16, the size of the current block may correspond to the predetermined size.

For example, when the current block is no longer divided, the size of the current block may correspond to the predetermined size. For example, if the partition information for the current block, quadtree and / or binary tree partitioning information is 0, indicating that the current block is not divided, and the horizontal or vertical length of the current block is greater than the minimum length, the current block. The size of may correspond to a predetermined size. In this case, the minimum length may be four.

When the size of the current block does not correspond to a predetermined size (No in S1610), the split information about the current block and the intra prediction mode may be decoded (S1660). If the current block is not divided, the intra prediction mode for the current block may be decoded. When the current block is split, the intra prediction mode for each split subblock may be decoded.

If the size of the current block corresponds to a predetermined size (Yes in S1610), NDIP_flag may be decoded (S1620). In a next step, the decoded NDIP_flag value may be checked (S1630).

When NDIP_flag is 0 (No in S1630), as described above, at least one or more of split information about the current block, intra prediction mode of the current block, and intra prediction mode of the subblock may be decoded (S1660).

If NDIP_flag is 1 (Yes in S1630), the current block may be divided into subblocks (S1640). In this case, the sub block may be divided into a predetermined size and / or shape. Or it may be divided based on the decoded partition information.

In a next step, an intra prediction mode of a sub block generated by dividing a current block may be derived (S1650). The intra prediction mode of the block may be derived based on the intra prediction mode of the neighboring block. Alternatively, the intra prediction mode of the current block may be decoded and used.

Intra-prediction may be performed on the current block or sub-block using the derived intra-prediction mode (S1670).

The order of deriving an intra prediction mode of the plurality of sub-blocks in the current block may be a raster scan order based on the current block. Or, it may be a raster scan order based on a predetermined block size. For example, C1, C2, C3,... , An intra prediction mode of the sub blocks may be derived in a C16 order. Or C1, C2, C5, C6, C3, C4,... , C12, C15, C16 may be derived in the order. Alternatively, the intra prediction mode of each subblock may be derived in parallel. The intra prediction mode for each of the sub-blocks may be derived by at least one or more methods of deriving the intra prediction mode of the current block.

For example, when the current block is divided into subblocks to derive an intra prediction mode for each sub block, an intra prediction mode of neighboring blocks may be used.

For example, the statistical value of the intra prediction mode of the block located at the left and the top of the (0, 0) position sample of each sub block may be derived to the intra prediction mode of each sub block. For example, when the statistical value is an average value, the intra prediction mode of each sub block illustrated in FIG. 17 may be derived using Equation 4 below.

Alternatively, the intra prediction mode of the large block may be derived into the intra prediction mode of the sub block by comparing the sizes of the blocks located at the left and the top of the (0, 0) position sample of each sub block. In this case, when the sizes of the two blocks are the same, an average value of the intra prediction modes of the left and the upper blocks may be derived into the intra prediction mode of each sub block.

Alternatively, the mode having the smaller value may be derived as the intra prediction mode of the sub-block by comparing the magnitudes of the intra prediction modes of the block located on the left and the top of the (0, 0) position sample of each sub block. . When the values of the two modes are the same, one of the two modes may be derived as the intra prediction mode of the subblock.

Alternatively, the intra prediction mode of each subblock may be derived using the intra prediction mode around the current block. In this case, an intra prediction mode of at least one neighboring block of the current block located at the left and / or the top of the (0, 0) sample position of each sub block may be used. For example, the intra prediction mode of each sub block illustrated in FIG. 17 may be derived using Equation 5 below.

Alternatively, when the intra prediction modes of the neighboring blocks of the current block are all non-directional modes, the intra prediction modes of the sub-blocks may be derived into at least one of the non-directional modes (eg, the DC mode and the planar mode).

As shown in FIG. 18, the sub blocks in the current block may have various sizes and / or shapes. The partition structure and / or size of the current block and / or sub-block may be determined by encoding / decoding. In this case, the intra prediction mode for each sub block may be derived by at least one or more of the above-described methods of deriving the intra prediction mode of the current block or sub blocks.

For example, the statistical value of the intra prediction mode of the block located on the left and the top of the (0, 0) position sample of each sub block may be derived to the intra prediction mode of each sub block. For example, when the statistical value is an average value, the intra prediction mode of the sub block illustrated in FIG. 18 may be derived using Equation 6 below.

Alternatively, the statistical value of the intra prediction mode of at least one neighboring block adjacent to each sub block may be derived to the intra prediction mode of each sub block. For example, when the statistical value is an average value, the intra prediction mode of each sub block illustrated in FIG. 18 may be derived using Equation 7 below.

Alternatively, when the intra prediction modes of the neighboring blocks of the current block are all non-directional modes, the intra prediction modes of the sub-blocks may be derived into at least one of non-directional modes (eg, DC mode and planar mode).

When the current block is divided into sub-blocks to derive an intra prediction mode for each sub block, the MPM is used to derive an intra prediction mode for the current block, and then the derived mode and the screen of the neighboring block. The intra prediction mode of each subblock may be derived using the intra prediction mode. In this case, by using at least one of the intra prediction mode of the current block derived from the MPM and the intra prediction mode of the neighboring block, the sub mode is derived by at least one of the methods of deriving the intra prediction mode of the current block. Intra prediction mode of a block can be derived. For example, when the intra prediction mode of the current block derived using the MPM is Pred_mpm, the intra prediction mode of the sub block may be derived as follows.

For example, if the average value is greater than Pred_mpm by comparing the average value of the intra prediction mode of the block located on the left and top of the (0, 0) position samples of each sub-block, the Pred_mpm + 1, If less than Pred_mpm, Pred_mpm-1 may be derived to the intra prediction mode of the subblock. Alternatively, the intra prediction mode and the average value of the Pred_mpm of the blocks located at the left and the top of the (0, 0) position samples of each sub block may be derived to the intra prediction mode. Alternatively, the intra prediction mode may be derived by adjusting the Pred_mpm by comparing the intra prediction mode of the block located at the left or top of the (0, 0) position sample of each sub block with the size of the Pred_mpm. In this case, at least one of the aforementioned statistical values may be used instead of the average value.

In FIG. 19, the number in each block means the number of intra prediction modes of the block. In addition, Cx (x is 1 .. 16) means the x-th sub-block in the current block. In addition, an arrow means an intra prediction direction or an angle of the block.

For example, the statistical value of the intra prediction mode of the block located on the left and top of the (0, 0) position samples of each sub block may be derived to the intra prediction mode of each sub block. The statistical value may be, for example, an average value. Alternatively, when at least one of the intra prediction modes of the neighboring block is the non-directional mode, the intra prediction mode of the subblock may be derived from the intra prediction mode among the intra prediction modes of the neighboring block. The non-directional mode may include, for example, a planar mode (mode number 0) and a DC mode (mode number 1). For example, the intra prediction mode of each sub block illustrated in FIG. 19 may be derived using Equation 8 below.

In FIG. 20, the number in each block means the number of intra prediction modes of the block. In addition, Cx (x is 1 .. 14) means the x-th sub-block in the current block. In addition, an arrow means an intra prediction direction or an angle of the block.

In an embodiment described with reference to FIG. 20, first, at least one of an intra prediction mode for a current block and split information of a sub block may be derived through decoding. The intra prediction mode for each sub block in the current block is an average value of the intra prediction mode of the derived current block and the intra prediction mode of the block located at the left and top of the (0, 0) position sample of each sub block. It can be derived using. For example, when the intra prediction mode of the derived current block is larger than the average value, 1/2 of the average value may be subtracted from the derived intra prediction mode, and may be added when the value is smaller than or equal to the average value. have. In this case, at least one of the aforementioned statistical values may be used instead of the average value.

Alternatively, when at least one of the intra prediction modes of the neighboring block is the non-directional mode, the intra prediction mode of the subblock may be derived from the intra prediction mode among the intra prediction modes of the neighboring block. The non-directional mode may include, for example, a planar mode (mode number 0) and a DC mode (mode number 1). For example, assuming that the intra prediction mode of the derived current block is 52, the intra prediction mode of each sub block illustrated in FIG. 20 may be derived using Equation 9 below.

In deriving the intra prediction mode, after dividing the current block into a plurality of sub blocks smaller than the size of the current block, the intra prediction mode of each sub block may be derived. In this case, the intra prediction mode may mean an intra prediction direction. In this case, the intra prediction mode may be included in a set of intra prediction modes predefined by the encoder and the decoder.

For example, in-screen prediction of the current block using at least one of the intra prediction mode of the current block and the intra prediction modes of blocks encoded / decoded using the intra prediction of the reconstructed blocks adjacent to the current block. A prediction direction field (IPDF) may be generated. When generating the intra prediction direction field, a specific transform model may be used. After generating the IPDF, it may be used to determine the intra prediction mode of each sub block in the current block.

Also, similarly to the above example, when the current block is divided from a block having a larger size or a shallower depth than the current block, the current block may be a sub block of a block having a larger size or a shallower depth than the current block. In this case, an intra-picture of the current block using at least one of intra-prediction modes of blocks encoded / decoded by intra prediction among reconstructed blocks adjacent to a block larger in size or shallower than the current block. The prediction mode can be derived. In this case, the intra prediction mode for the current block may be derived by generating the intra prediction direction field.

The specific transformation model may include at least one of a rigid transform, a similarity transform, an affine transform, a homography transform, a 3D transform, and other transforms. More than one can be used. In this case, the homography transformation may be a projection transformation.

In this case, the intra prediction mode of each sub-block divided from the current block may include the intra prediction mode of the current block and the intra prediction modes of the blocks encoded / decoded using the intra prediction of the reconstructed blocks adjacent to the current block. Since it can be derived using at least one or more, bits necessary for entropy encoding / decoding of the intra prediction mode of each subblock can be reduced.

The granularity of the sub block may be smaller than or equal to the size of the current block. For example, when the size of the current block is M × N (M, N is a positive integer), the size of the sub block may be M / K × N / L. In this case, K may be a divisor of M and L may be a divisor of N. In addition, M / K or N / L may be a positive integer.

In addition, as many as P subblocks may exist in the current block based on the current block. Here, P may mean a positive integer including 0. For example, one, two, four, sixteen, or the like may exist in the current block.

In addition, when the current block is divided into the sub-blocks, information about whether the current block is divided into sub-blocks may not be separately entropy encoded / decoded. It may be determined whether the current block is divided into sub-blocks based on information indicating whether the intra prediction mode of the current block is derived on a sub-block basis.

The intra prediction mode of the sub-block may use at least one of intra prediction modes of the current block and intra prediction modes of blocks encoded / decoded using intra prediction among reconstructed blocks adjacent to the current block. In this case, the intra prediction mode of the subblock may not be entropy coded / decoded. However, the intra prediction mode of the current block may be entropy encoded / decoded. However, when the current block is composed of one sub-block, the intra prediction mode of the current block is not entropy encoded / decoded, but is a screen of blocks encoded / decoded using intra prediction from the reconstructed blocks adjacent to the current block. It may be derived using at least one or more of my prediction modes.

Among the reconstructed blocks adjacent to the current block used for generating the IPDF, blocks encoded / decoded using intra prediction may be referred to as seed blocks. The location of the seed block may be referred to as a seed point. An intra prediction mode of a seed block including a seed point may be referred to as a seed point intra prediction mode (SPIPM).

In the example shown in FIG. 21, the size of the current block may be 16 × 16, and the size of each sub block may be (16/4) × (16/4). In this case, the seed block may be at least one of a plurality of adjacent blocks encoded / decoded using intra prediction. In this case, the seed block or seed position may be a fixed position based on the current block. In addition, at least one of the top, left, top left, bottom left, and top right blocks or positions may be determined as the seed block or the seed position based on the current block.

For example, the intra prediction mode of at least one or more adjacent blocks among the adjacent blocks c, d, e, f, and g of the current block may be used as the SPIPM.

Alternatively, the intra prediction mode of the adjacent block h at the upper right end of the current block may be used as the SPIPM.

Alternatively, the intra prediction mode of at least one or more adjacent blocks among the adjacent blocks a and b in the upper left of the current block may be used as the SPIPM.

Alternatively, at least one intra prediction mode among the adjacent blocks i, j, k, and l on the left side of the current block may be used as the SPIPM.

Alternatively, the intra prediction mode of the adjacent block m at the lower left of the current block may be used as the SPIPM.

For example, the intra prediction mode of the current block may also be used as the SPIPM.

IPDFs may be generated using SPIPMs of one or more seed points.

For example, the coordinates of a plurality of seed positions for parameter determination of a specific transformation model are (x_sp, y_sp) (sp = 1, 2, 3, ...), and the SPIPM of the seed block including the seed positions. When this mode_sp (sp = 1, 2, 3, ...), the coordinates (x_sp ', y_sp') of each seed position after conversion using a specific transformation model are (x_sp ', y_sp') = (x_sp + dx, y_sp + dy). In this case, dx may mean displacement in the x-axis direction and dy may mean displacement in the y-axis direction. In addition, it may be determined by dx = D_sub * cosθ and dy = D_sub * sinθ.

In this case, θ may be determined according to the SPIPM. For example, when the intra prediction mode is a directional mode as shown in FIG. 6, each SPIPM has a unique direction and a positive angle of the x-axis reference may be determined as θ.

For example, θ = 270 ° in the vertical prediction mode.

For example, in the horizontal prediction mode, θ may be 0 °.

For example, in the intra prediction mode in the lower left diagonal direction, θ may be 225 °.

For example, in the intra prediction mode in the upper right diagonal direction, θ may be 45 °.

For example, in the intra prediction mode in the lower right diagonal direction, θ may be 135 °.

In this case, the intra prediction mode having no orientation, such as DC or planar mode, may determine θ as a specific value. The specific value may be, for example, an angle of 0, 90, 180, 270, or the like.

SPIPM means directionality at the seed position, and D_sub may mean the size of the vector having the corresponding direction. The size of D_sub may be determined according to the size and / or shape of the seed block to which the seed location belongs. In addition, D_sub may have a fixed value P in all intra prediction modes. Here, P may be an integer including 0. For example, if the current block is an MxN (M, N is a positive integer) block, D_cur = S (S is a positive integer), the D_sub (of the seed block is KxL (K, L is a positive integer). sub = 1,2,3, ...) may be determined as D_sub = S * (KxL) / (MxN). For example, in FIG. 21, when the size of the current block is 16 × 16, D_cur = S and D_sub of the seed block may be determined by one or more of the methods described below.

For example, D_sub = S * (4x8) / (16x16) = S / 8 of the seed block d or e may be determined.

For example, it may be determined that D_sub = S * (8x8) / (16x16) = S / 4 of the seed block g or j.

For example, it may be determined that D_sub = S * (8x4) / (16x16) = S / 8 of the seed block k or l.

For example, D_sub = S * (16 × 16) / (16 × 16) = S of the seed block m or h may be determined.

For example, D_sub of all seed blocks may be determined as S.

A list of SPIPMs can be constructed to form a candidate for generating an IPDF of the current block. The SPIPM list may be generated using an intra prediction mode of at least one of neighboring blocks neighboring the current block. For example, the SPIPM may be configured with a set of one or more candidates among the upper left end (SPIPM_TL), the upper right end (SPIPM_TR), the lower left end (SPIPM_BL), and the lower right end (SPIPM_BR) of the current block. In this case, the SPIPM_TL may have at least one of the intra prediction modes of the neighboring blocks located at the upper and upper left and the left of the (0,0) position of the current block for the current block of the WxH size. The SPIPM_TR may have at least one of the intra prediction modes of the neighboring blocks located at the top and the top right of the (W-1, 0) position of the current block as a candidate. The SPIPM_BL may have at least one of the intra prediction modes of the adjacent blocks located at the left and the lower left of the (0, H-1) position of the current block as a candidate. SPIPM_BR may indicate an intra prediction mode of a neighboring block neighboring the current block. Alternatively, SPIPM_BR may be used to indicate an intra prediction mode of the current block.

In the example illustrated in FIG. 21, the SPIPM_TL may have at least one of intra prediction modes of adjacent blocks d, b, and j. In addition, SPIPM_TR may have at least one of intra prediction modes of adjacent blocks g and h. In addition, SPIPM_BL may have at least one of intra prediction modes of adjacent blocks i and m. In addition, SPIPM_BR may have at least one of intra prediction modes of the current block.

In addition, the seed block or seed positions may be searched in a certain order. For example, a list of SPIPMs may be constructed using an intra prediction mode that is searched in the order of left, top, bottom left, top right, and top and exists at a corresponding seed block or seed position.

In order to construct a list of SPIPM, at least one of each candidate of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR may be configured to exclude a mode having a different direction from that of other modes based on the similarity between prediction modes in the picture. have. In this case, IPMD (Intra Prediction Mode Difference) between intra prediction modes may be used as a measure of similarity. Non-directional modes (eg DC_MODE and PLANAR_MODE) can be excluded from the SPIPM list configuration.

For example, for each of the three candidate modes (SPIPM_TL_mode) of SPIPM_TL, IPMD = abs (SPIPM_TL_mode-SPIPM_neighbor)> Th1 (Th1 is a positive integer) compared to the candidate modes of SPIPM_neighbor (neighbor = TR or BL or BR). In this case, the corresponding mode may be excluded from the candidate set for SPIPM_TL.

For example, for each of the two candidate modes (SPIPM_TR_mode) of SPIPM_TR, IPMD = abs (SPIPM_TR_mode-SPIPM_neighbor)> Th2 (Th2 is a positive integer) compared to the candidate modes of SPIPM_neighbor (neighbor = TL or BL or BR). In this case, the mode may be excluded from the candidate set for SPIPM_TR.

For example, for each of the two candidate modes (SPIPM_BL_mode) of SPIPM_BL, IPMD = abs (SPIPM_BL_mode-SPIPM_neighbor)> Th3 (Th3 is a positive integer) compared to the candidate modes of SPIPM_neighbor (neighbor = TL or TR or BR). In this case, the mode may be excluded from the candidate set for SPIPM_BL.

For example, for each of the candidate modes (SPIPM_BR_mode) of SPIPM_BR, IPMD = abs (SPIPM_BR_mode-SPIPM_neighbor)> Th4 (Th4 is a positive integer) compared to the candidate modes of SPIPM_neighbor (neighbor = TL or TR or BL). In this case, the mode can be excluded from the candidate set for SPIPM_BR.

For example, when at least one of the candidates of the SPIPM_TL, the SPIPM_TR, the SPIPM_BL, and the SPIPM_BR is an intra prediction mode without directivity, such as DC or planar mode, the candidate may be excluded from the candidate set.

After excluding candidates having similarities among the candidate modes for constructing the SPIPM list, the number of SPIPMs required for generating an IPDF may be determined according to a specific 2D transformation model used. For example, the 2D transformation model may include a rigid transformation, similar transformation, affine transformation, homography transformation, and the like. Also, for example, the number of SPIPMs may be variably determined, such as one, two, three, four, or N (N is a positive integer) according to the 2D transformation model.

For example, when using a rigid transform as a transformation model for generation of IPDF, at least two SPIPMs may be needed.

In the case of a rigid body transformation, it may have 3-DoF (degree of freedom) as shown in Equation 10 below. In this case, (x, y) may be a coordinate before transformation of the seed position, and (x ', y') may be a coordinate after transformation. θ, tx, ty are model parameters to be determined, and may be rotation angle, x-axis displacement, and y-axis displacement, respectively.

(X, y)-(x ', y') pairs can be obtained using θ determined from one SPIPM, and two equations relating to θ, tx, ty can be determined by substituting Equation (10). In addition, four equations for θ, tx, and ty may be determined from two SPIPMs, and three of them may be used to determine a rigid body transformation model.

Two SPIPMs may be determined by selecting at least two of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR. The selected SPIPM may be added to the SPIPM list.

As shown in FIG. 22, the sum of the IPMD values of the two SPIPM candidate modes may be sequentially filled in the SPIPM list.

For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_TR may be used as two SPIPMs.

For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_BL may be used as two SPIPMs.

For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_BR may be used as two SPIPMs.

For example, one of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BL may be used as two SPIPMs.

For example, one of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BR may be used as two SPIPMs.

For example, one of the candidate modes of SPIPM_BL and one of the candidate modes of SPIPM_BR may be used as two SPIPMs.

If two SPIPMs are not filled, the SPIPM list can be populated using the available SPIPMs. For example, SPIPM ± delta can be used to populate the SPIPM list. In this case, delta may be any positive integer, for example, 1, 2, 3,... It can have a value such as.

When two SPIPMs (SPIPM1 and SPIPM2) are determined, four equations for θ, tx, and ty can be generated using Equation 10, and three of them can be used to determine parameters of the rigid body transformation model. . The determined model can be used for generating IPDF.

For example, the rigid body transformation may be determined using at least one of two equations calculated with SPIPM1 and two equations calculated with SPIPM2.

For example, at least two SPIPMs may be required when using a similarity transform as a transformation model for generating an IPDF.

The similarity transformation may have 4-DoF (degree of freedom) as shown in Equation 11 below. In this case, (x, y) may be a coordinate before transformation of the seed position, and (x ', y') may be a coordinate after transformation. a, b, c, and d may be model parameters to be determined.

(X, y)-(x ', y') pairs can be obtained using θ determined from one SPIPM, and two equations for a, b, c, and d can be determined by substituting Equation (11). In addition, four equations for a, b, c, and d may be determined from the two SPIPMs, and the similarity transformation model may be determined using the equations.

Two SPIPMs may be determined by selecting at least two of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR. The selected SPIPM may be added to the SPIPM list. In this case, as shown in FIG. 22, the SPIPM list may be sequentially filled in order of the sum of the IPMD values of the two SPIPM candidate modes being small.

If two SPIPMs are not filled, the SPIPM list can be populated using the available SPIPMs. For example, SPIPM ± delta can be used to populate the SPIPM list. In this case, delta may be any positive integer and 1, 2, 3,... It can have a value such as.

When two SPIPMs (SPIPM1 and SPIPM2) are determined, four equations for a, b, c, and d may be generated through Equation 11 to determine parameters of the similarity conversion model. The determined model can be used for generating IPDF.

For example, at least three SPIPMs may be required when using affine transform as a transformation model for generating an IPDF.

In the case of affine transformation, it may have 6-DoF (degree of freedom) as shown in Equation 12 below. In this case, (x, y) may be a coordinate before transformation of the seed position, and (x ', y') may be a coordinate after transformation. a, b, c, d, e, and f may be model parameters to be determined.

By using θ determined from one SPIPM, (x, y)-(x ', y') pairs can be obtained, and two equations for a, b, c, d, e, and f can be substituted into equation (12). Can be determined. In addition, six equations for a, b, c, d, e, and f may be determined from three SPIPMs, and the affine transformation model may be determined using the equations.

The three SPIPMs may be determined by selecting at least three of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR. The selected SPIPM may be added to the SPIPM list.

As shown in FIG. 23, the sum of the IPMD values of the three SPIPM candidate modes may sequentially fill the SPIPM list.

For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BL may be used as three SPIPMs.

For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as three SPIPMs.

For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR may be used as three SPIPMs.

For example, one of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR may be used as three SPIPMs.

If three SPIPMs are not filled, the SPIPM list can be populated using the available SPIPMs. For example, SPIPM ± delta can be used to populate the SPIPM list. In this case, delta may be any positive integer and 1, 2, 3,... It can have a value such as.

When three SPIPMs (SPIPM1, SPIPM2, and SPIPM3) are determined, Equation 12 may generate six equations for a, b, c, d, e, and f to determine the parameters of the affine transformation model. The determined model can be used for generating IPDF.

For example, at least four SPIPMs may be required when using a homography transform or perspective transform as a transformation model for generating an IPDF.

In the case of the homography transformation, it may have 8-DoF (degree of freedom) as shown in Equation 13 below. In this case, (x, y) may be a coordinate before transformation of the seed position, and (x ', y') may be a coordinate after transformation. h1, h2, h3, h4, h5, h6, h7, h8 may be model parameters to be determined.

(X, y)-(x ', y') pairs can be obtained using θ determined from one SPIPM and substituted into equation (13) to h1, h2, h3, h4, h5, h6, h7, h8. Two equations can be determined. In addition, eight equations for h1, h2, h3, h4, h5, h6, h7, h8 can be determined from the four SPIPMs, which can be used to determine homography transformation models.

Four SPIPMs may be determined by selecting at least four of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR. The selected SPIPM may be added to the SPIPM list.

At this time, as shown in FIG. 24, the SPIPM list may be sequentially filled in order of the sum of the IPMD values of the four SPIPM candidate modes being small.

For example, two of the candidate modes of SPIPM_TL and two of the candidate modes of SPIPM_TR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TL and two of the candidate modes of SPIPM_BL may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TL and two of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BL and two of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of the SPIPM_TR, one of the candidate modes of the SPIPM_TL, and one of the candidate modes of the SPIPM_BL may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BL and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BL, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_TR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BL, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_TR may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs.

For example, two of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs.

For example, one of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

If four SPIPMs are not filled, the SPIPM list can be populated using the available SPIPMs. For example, SPIPM ± delta can be used to populate the SPIPM list. In this case, delta may be any positive integer and 1, 2, 3,... It can have a value such as.

When four SPIPMs (SPIPM1, SPIPM2, SPIPM3, SPIPM4) are determined, Equation 13 generates eight equations for h1, h2, h3, h4, h5, h6, h7, h8, and the parameters of the homography conversion model. Can decide. The determined model can be used for generating IPDF.

After generating an IPDF using a specific transformation model, an intra prediction mode of sub blocks KxL in the current block WxH may be allocated using the generated IPDF. In this case, the granularity KxL (positive integer of K <= M, positive integer of L <= H) may be a fixed size smaller than or equal to the current block size. Alternatively, the size of the sub block may be adaptively determined using the size of the current block and / or IPMD. Alternatively, the size of the sub block may be the same as the size of the current block.

As shown in (a) of FIG. 25, the size of the sub block may be a fixed size of 8 × 8. Alternatively, as shown in FIG. 25B, the size of the sub block may be a fixed size of 4 × 4. Alternatively, as shown in FIG. 25C, the size of the sub block may be a fixed size of 2 × 2. Alternatively, as shown in FIG. 25C, the size of the sub block may be a fixed size of 1 × 1. In this case, the fixed size of 1 × 1 may be a sample unit.

For example, the size of the sub block may be determined based on the size of the current block.

For example, the size of the sub block may be determined based on at least one of four IPMDs of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR of the current block.

For example, the size of the sub block may be determined based on the size of the current block and at least one of four IPMDs of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR.

The granularity of the sub-blocks may be entropy encoded / decoded in the bitstream. In this case, the information may include a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, a tile header, a CTU unit, and a CU unit. , Entropy encoding / decoding may be performed in at least one of a PU unit, a TU unit, a block unit, and a sub block unit.

Information about the granularity of the sub-block may not be transmitted and may be adaptively derived from the encoder / decoder according to the size of the current block and / or IPMD.

In addition, the size of the sub block may be determined based on at least one of encoding parameters of the current block and encoding parameters of neighboring blocks of the current block.

The determined IPDF may be used to allocate an intra prediction mode of sub blocks. In this case, the coordinates of a specific position in each subblock may be substituted into the determined IPDF model to obtain the intra prediction mode at the corresponding position as a vector value. In this case, the specific position may be determined as a position of an arbitrary pixel in the sub block or a position that contacts a boundary of the sub block. For example, at least one of the upper left, upper right, lower left, lower right, and intermediate positions of the sub block may be determined as a specific position. When the coordinate of a specific position in the subblock is called (x, y) and the transformed coordinate calculated through IPDF at that position is (x ', y'), the direction θ _SB of the vector is θ _SB = atan [(y'-y) / (x'-x)]].

As shown in FIG. 26, θ _SB May be mapped to the intra prediction mode in the direction most similar to the directional mode. θ _SB The mapping to the intra prediction mode may use a look-up table (LUT).

In addition, when the intra prediction mode of the subblocks is allocated using the IPDF, the intra prediction mode of the subblocks may be allocated to the IPDF based on a neighbor neighbor method.

In addition, when the intra prediction mode of the sub blocks is allocated using the IPDF, the intra prediction mode of the sub blocks may be allocated by quantizing the IPDF in an integer form.

When the intra prediction mode of the sub blocks is allocated using the IPDF, the intra prediction mode of the sub blocks may be allocated by rounding the IPDF to an integer.

The information to be additionally entropy coded / decoded in the bitstream for intra-picture prediction using a transform model may include at least one of the following.

Information indicating whether intra-unit prediction within the sub-block unit using the transform model is performed for the current block: TBIP_flag

In this case, the TBIP_flag is a picture of a sub-block unit using at least one of an intra prediction mode of a current block and intra prediction modes of blocks encoded / decoded using intra prediction among reconstructed blocks adjacent to the current block. Information about whether to derive my prediction mode.

Index indicating the SPIPM set used: SPIPM_idx

Hereinafter, another embodiment of deriving an intra prediction mode on a sub-block basis using a transform model will be described. For example, if there is an encoded / decoded block by performing intra prediction on a sub-block basis using a transform model among adjacent reconstructed blocks, instead of generating an IPDF of the current block directly, the sub-block is used by using the IPDF model of the adjacent block. Intra prediction mode of a unit can be derived.

In order to determine whether there is an encoded / decoded block by performing intra prediction on a sub-block basis using a transform model among neighboring reconstructed blocks of the current block, a predefined scanning order may be followed. In this case, the scanning order may be at least one of the following.

For example, scanning may be performed in the order of A-> B-> C-> D-> E in FIG. Alternatively, scanning may be performed in the order of A-> B-> D-> C-> E. Alternatively, scanning may be performed in the order of B-> A-> D-> C-> E. Alternatively, scanning may be performed in the order of E-> A-> B-> C-> D. Alternatively, scanning may be performed in an order other than the above.

Alternatively, some of the A, B, C, D, and C blocks may be excluded from scanning. Alternatively, blocks other than the A, B, C, D, and C blocks may be scanned. The adjacent reconstruction blocks that are the target of the scanning may be determined based on at least one of a size, a shape of at least one of the adjacent reconstruction blocks and the current block, and encoding parameters mentioned herein.

In the example shown in FIG. 28, when the A block is encoded / decoded by intra-block prediction in sub-block units using a transform model, at least one of SPIPM_A_TL, SPIPM_A_TR, SPIPM_A_BL, and SPIPM_A_BR of the A block is selected. Can be used to generate an IPDF of the A block.

The IPDF of the generated A block may be used to derive at least one of SPIPM_Cur_TL, SPIPM_Cur_TR, SPIPM_Cur_BL, and SPIPM_Cur_BR of the current block, and generate an IPDF of the current block, thereby performing intra prediction on a sub-block basis. have.

If at least one of the neighbor reconstruction blocks of the current block is a block encoded / decoded using IPDF, the IPDF of the current block may be derived using the IPDF of the corresponding neighbor reconstruction block. In addition, TBIP_flag information may be entropy encoded / decoded.

Hereinafter, another embodiment of deriving an intra prediction mode in sub-block units using an equal-space model will be described.

At least two SPIPMs may be required when using equidistant models. For example, as shown in (a) of FIG. 29, one of the candidate modes of the SPIPM_TL, one of the candidate modes of the SPIPM_TR, one of the candidate modes of the SPIPM_BL, and one of the candidate modes of the SPIPM_BR are selected and a total of four are selected. You can choose a dog. The four selected SPIPM candidate modes may populate the SPIPM list in order of decreasing sum of IPMD values, as shown in FIG. 24.

Intra-prediction modes of sub-blocks located at the outermost side of the current block may be preferentially determined using SPIPM_TL, SPIPM_TR, SPIPM_BL and / or SPIPM_BR. In this case, determining the intra prediction mode at equal intervals may mean that the intra prediction modes are divided into equal intervals and allocated to sub blocks using at least two intra prediction modes.

For example, in the example shown in (a) of FIG. 29, when SPIPM_TL is 24 and SPIPM_TR is 21, the intra prediction modes of sub-blocks A, B, C, and D use the values of SPIPM_TL and SPIPM_TR, and the like. Can be determined at intervals. For example, as shown in FIG. 29B, it may be determined that subblocks A = 24, B = 23, C = 22, and D = 21.

For example, in the example shown in (a) of FIG. 29, when SPIPM_TL is 25 and SPIPM_BL is 38, the intra prediction modes of sub-blocks A, E, I, and M are performed using the values of SPIPM_TL and SPIPM_BL, and so on. Can be determined at intervals. For example, as shown in FIG. 29B, it may be determined that subblocks A = 24, E = 29, I = 34, and M = 38.

For example, in the example shown in (a) of FIG. 29, when SPIPM_BL is 38 and SPIPM_BR is 35, the intra prediction modes of the sub-blocks M, N, O, and P are obtained by using the values of SPIPM_BL and SPIPM_BR, and the like. Can be determined at intervals. For example, as shown in (b) of FIG. 29, it may be determined as subblocks M = 38, N = 37, O = 36, and P = 35.

For example, in the example shown in (a) of FIG. 29, when SPIPM_TR is 21 and SPIPM_BR is 35, the intra prediction modes of sub-blocks D, H, I, and P are performed using the values of SPIPM_TR and SPIPM_BR, and the like. Can be determined at intervals. For example, as shown in FIG. 29B, D = 21, H = 26, I = 31, and P = 35.

After all the intra prediction modes of the sub blocks positioned at the outermost side of the current block are determined, the intra prediction modes of the second outer sub blocks may be determined. In the example shown in FIG. 29, the second outer sub blocks may be sub blocks F, G, J, and K. At this time, SPIPM_TL may be reset to the mode (mode of subblock A in FIG. 29A) of the upper left position of the upper left subblock (subblock F in FIG. 29A) of the second outer subblock. have. Also, SPIPM_TR may be reset to a mode (mode of subblock D in FIG. 29A) of the upper right position of the upper right subblock (subblock G in FIG. 29A) of the second outer subblock. . Further, SPIPM_BL may be reset to the mode (mode of subblock M in FIG. 29A) in the lower left position of the lower left subblock (subblock J in FIG. 29A) of the second outer subblock. Can be. In addition, SPIPM_BR is reset to the mode (mode of subblock P in FIG. 29A) of the lower right position of the lower right subblock (subblock K in FIG. 29A) of the second outer subblock. Can be. This process may be repeated recursively until the mode of all subblocks in the current block is determined.

For example, in the example shown in (b) of FIG. 29, when SPIPM_TL is 24 and SPIPM_TR is 21, the intra prediction modes of sub-blocks F and G may be determined at equal intervals using the values of SPIPM_TL and SPIPM_TR. have. For example, as shown in (c) of FIG. 29, it may be determined as subblocks F = 24 and G = 21.

For example, in the example shown in (b) of FIG. 29, when SPIPM_BL is 38 and SPIPM_BR is 35, the intra prediction modes of sub-blocks J and K may be determined at equal intervals using the values of SPIPM_TL and SPIPM_TR. have. For example, as shown in (c) of FIG. 29, it may be determined as subblocks J = 38 and K = 35.

Information to be additionally entropy encoded / decoded for intra prediction on a sub-block basis using an equal interval model may be at least one of the following.

Information indicating whether derivation of the intra prediction mode in sub-block units using the equal interval model is performed on the current block: ES_flag

Index indicating SPIPM set used: SPIPM_idx

Hereinafter, another embodiment of deriving an intra prediction mode in sub-block units using a bilinear filter model will be described.

At least two SPIPMs may be needed to determine the intra prediction mode in sub-block units using the bilinear filter model. For example, as shown in (a) of FIG. 30, one of the candidate modes of the SPIPM_TL, one of the candidate modes of the SPIPM_TR, one of the candidate modes of the SPIPM_BL, and one of the candidate modes of the SPIPM_BR are selected and a total of four are selected. You can choose a dog. The four selected SPIPM candidate modes may populate the SPIPM list in order of decreasing sum of IPMD values, as shown in FIG. 24.

The mode of the upper left subblock in the current block (subblock A in FIG. 30A) may be determined by the SPIPM_TL value. In addition, the mode of the upper right subblock (subblock D in FIG. 30A) may be determined by the SPIPM_TR value. In addition, the mode of the lower left subblock (subblock M in FIG. 30A) may be determined by the SPIPM_BL value. In addition, the mode of the lower right subblock (subblock P in FIG. 30A) may be determined by the SPIPM_BR value. As shown in (b) of FIG. 30, the intra prediction modes of the upper left, upper right, lower left and lower right sub-blocks in the current block may be determined by SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR values, respectively. However, the present invention is not limited thereto, and at least one of intra prediction modes of the upper left, upper right, lower left and lower right sub-blocks in the current block may be determined by at least one of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR.

The intra prediction mode of the other subblocks may be determined using a bilinear filter technique. For example, Equation 14 below may be used. In Equation 14, function () may be at least one of floor (), ceil (), or round (). In the example shown in FIG. 30, function () may be round (). Also, in Equation 14, # of SubBlk in wdt may mean the number of sub blocks in a horizontal direction of the current block. Similarly, # of SubBlk in hgt may mean the number of sub blocks in the vertical direction of the current block.

For example, as illustrated in (c) of FIG. 30, the intra prediction mode of the remaining subblocks may be determined using Equation 14 above.

Information to be additionally entropy encoded / decoded for intra prediction in sub-block units using a bilinear filter model may be at least one or more of the following.

Information indicating whether derivation of intra prediction mode in sub-block units using a bilinear filter model is performed on the current block: BF_flag

Index indicating SPIPM set used: SPIPM_idx

An intra prediction mode is derived for each sub-block by using at least one of the intra prediction mode of the current block and the intra prediction modes of blocks encoded / decoded using intra prediction among reconstructed blocks adjacent to the current block. Intra-prediction may be performed on a sub-block basis using the derived intra-prediction mode. In this case, a sample included in a subblock previously encoded / decoded in subblock units may be used as a reference sample for intra prediction in subblock units.

The encoder may generate transform coefficients by performing at least one of a first-order transform, a second-order transform, and quantization on the residual block generated after performing intra prediction on a sub-block basis. The generated transform coefficients may be entropy coded. Primary transform, secondary transform, and quantization may be performed on the current block or may be performed on a sub-block basis. For example, at least one of the first transform, the second transform, and the quantization may be performed for the entire current block, or at least one of the first transform, the second transform, and the quantization may be performed for each subblock. At this time, none of the first-order transform, second-order transform, and quantization may be performed on the current block or subblock.

In the decoder, the transform coefficients may be entropy decoded. The reconstructed residual block may be generated by performing at least one of inverse quantization, first order inverse transform, and second order inverse transform on the entropy decoded transform coefficient. Primary transform, secondary transform, and quantization may be performed on the current block or may be performed on a sub-block basis. For example, at least one of the first transform, the second transform, and the quantization may be performed for the entire current block, or at least one of the first transform, the second transform, and the quantization may be performed for each subblock. At this time, none of the first-order transform, second-order transform, and quantization may be performed on the current block or subblock.

Information about intra prediction may be entropy encoded / decoded from the bitstream. 31 is a diagram illustrating a syntax structure including information about an intra prediction mode. As illustrated in FIG. 31, the information about the intra prediction may include at least one or more of the following information. In this case, the information about the intra prediction may be selected from among a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header. It may be signaled through at least one.

Flag indicating whether or not Most Probable Mode (MPM) is matched, eg prev_intra_luma_pred_flag

Index specifying position in MPM list: ex) mpm_idx

Prediction mode information in luminance component screen: ex) rem_intra_luma_pred_mode

Prediction mode information in chrominance component screen: ex) intra_chroma_pred_mode

Curvature parameter of prediction mode in curved screen: ex) cuv

Weight parameter of prediction mode in curved screen: ex) cw1, cw2,... , cwNs-1

Look-up-table (LUT) for curved intra prediction

A flag indicating that the intra prediction mode of the current block and the sub block is derived using the intra prediction mode of the neighboring block: ex) NDIP_flag

Flag indicating whether to perform residual signal prediction: ex) SRP_flag

Intra prediction mode included in each MPM list for each of the N MPM lists when deriving the intra prediction mode of the current block using the N MPM lists or entropy encoding / decoding the intra prediction mode of the current block. Among them, an indicator (MPM flag) indicating whether or not the same intra prediction mode as the intra prediction mode of the current block exists (eg, MPM_FLAG_1, MPM_FLAG_2,... , MPM_FLAG_N

If there are intra prediction modes that are identical to the intra prediction modes of the current block among the intra prediction modes included in the specific MPM list among the N MPM lists, the position or order in which the intra prediction modes exist in the specific MPM list Index information for: eg MPM_IDX_1, MPM_IDX_2,… , MPM_IDX_N

Index indicating the SPIPM set used and information indicating whether intra-picture prediction has been performed on a sub-block basis using the transform model for the current block: ex) TBIP_flag, SPIPM_idx

Information indicating whether the derivation of the intra prediction mode in the sub-block unit using the equal interval model is performed for the current block and the index indicating the SPIPM set used: ES_flag, SPIPM_idx

Information indicating whether derivation of the intra prediction mode in sub-block units using the bilinear filter model is performed on the current block, and an index indicating the SPIPM set used: BF_flag and SPIPM_idx

The MPM (Most Probable Mode) If the flag is 1, the intra prediction mode of the luminance component is derived from the candidate modes, including my mode MPM index (mpm _ idx) the use of the screen of the already encoded / decoded adjacent units Can be.

If the MPM of (Most Probable Mode) flag is 0, the intra-prediction mode of the luminance component may be encoded / decoded using the intra prediction mode information (rem_ intra luma _ _ pred _mode) for the luminance component.

The intra prediction mode of the chrominance component may be encoded / decoded using the intra prediction mode information ( intra_chroma_pred_mode) for the chrominance component and / or the intra prediction mode for the corresponding luminance component block.

The prediction mode in the curved screen may derive the pixel prediction value using reference pixels of different angles according to the position (x, y) of the pixel in the prediction block. The pixels in the prediction block may be grouped into a plurality of groups, and the first group may use an intra prediction mode having an angle different from that of the second group. Each group may include one or more pixels. Each group can have triangles, squares, and other geometric shapes.

The curvature parameter cuv of the prediction mode within the curved screen may mean a curvature applied to the prediction mode within the curved screen. Curved intra prediction may be performed using one or more cuv for the current block. The curvature parameter may be derived from the curvature parameter (s) of at least one of the curvature parameters of the neighboring blocks.

One or more weight parameters cw of the prediction mode in the curved screen may be applied to the current block. When a plurality of weighting parameters are applied, different weighting parameters may be applied in predetermined units such as pixels, rows, columns, or sub-blocks of the current block. The weight parameter may be derived from at least one weight parameter (s) of the weight parameters of the neighboring blocks.

The neighboring block for deriving the curvature parameter and / or the weight parameter may be already encoded / decoded blocks adjacent to the top, left and / or right side of the current block.

Various forms of curved intra prediction may be performed using at least one of cuv and cw.

In case of using N cuv and M cw, at least NxMx4 or more prediction blocks may be generated to perform intra prediction of the current block.

For example, when one cuv and one cw are used, at least four prediction blocks may be generated to perform intra prediction of the current block.

For example, by using two cuv and one cw, at least eight prediction blocks may be generated to perform intra prediction of the current block.

For example, when one cuv and two cws are used, at least eight prediction blocks may be generated to perform intra prediction of the current block.

For example, by using two cuv and two cw, at least 16 prediction blocks may be generated to perform intra prediction of the current block.

Two or more cuv and / or cw information may be encoded / decoded using a default value and a delta value. In this case, Default may mean one cuv value and / or one cw value, and delta may be a constant value.

For example, when using two cuv in the current block, two curvature parameters may be default_cuv, default_cuv + delta_cuv.

For example, when using N cuv in the current block, the N curvature parameters are default_cuv, default_cuv + delta_cuv, default_cuv + 2 * delta_cuv,... , default_cuv + (N-1) * delta_cuv. (Where N is a positive integer of 2 or greater)

For example, when using 2N + 1 cuv in the current block, the 2N + 1 curvature parameters are default_cuv, default_cuv + delta_cuv, default_cuv-delta_cuv, default_cuv + 2 * delta_cuv, default_cuv-2 * delta_cuv,... , default_cuv + N * delta_cuv and default_cuv-N * delta_cuv. (Where N is a positive integer of 1 or more)

For example, when using two cws in the current block, the two weighting parameters may be default_cw, default_cw + delta_cw. (Default_cw + delta_cw is the addition of element units of the vector)

For example, when using M cw in the current block, the M weight parameters are default_cw, default_cw + delta_cw, default_cw + 2 * delta_cw,... , default_cw + (M-1) * delta_cw. (Where default_cw + delta_cw is the addition of the unit of elements of the vector, and M is a positive integer of 2 or more)

For example, if 2M + 1 cw is used in the current block, the 2M + 1 curvature parameters are default_cw, default_cw + delta_cw, default_cw-delta_cw, default_cw + 2 * delta_cw, default_cw-2 * delta_cw,... , default_cw + M * delta_cw, default_cw-M * delta_cw. (Where M is a positive integer of 1 or greater)

The above-described cuv and / or cw information may be encoded or decoded into a bitstream. Alternatively, the encoder and the decoder may share and store information about the number and / or value of cuv and / or cw in the form of a lookup table, for example.

When the SRP_flag is 1, prediction of the residual signal may be performed using an intra picture mode determined for the current block or sub block.

The information about the intra prediction may be entropy encoded / decoded from the bitstream based on at least one or more of coding parameters. For example, NDIP_flag may be encoded / decoded based on information related to partition information of a block.

For example, when at least one of split_flag, quadtree_flag, and binarytree_flag is '0' and no longer split, the NDIP_flag may be encoded / decoded.

For example, when binarytree_flag is 1, NDIP_flag may not be encoded / decoded.

At least one or more of the information about the intra prediction may not be signaled based on at least one or more of the size and shape of the block.

For example, when the size of the current block corresponds to a predetermined size, at least one of the information about the intra prediction for the current block is not signaled, and the intra prediction corresponding to the higher block size previously encoded / decoded is not signaled. One or more information regarding may be used.

For example, when the shape of the current block is rectangular, one or more pieces of information about the intra prediction corresponding to the higher block size previously encoded / decoded without at least one of the information about the intra prediction for the current block is not signaled. Can be used.

When entropy encoding / decoding at least one or more pieces of information on the intra prediction, at least one or more of the following binarization methods may be used.

Truncated Rice Binarization Method

K-th order Exp_Golomb binarization

Limited K-th order Exp_Golomb binarization

Fixed-length binarization

Unary Binarization Method

Truncated Unary Binarization Method

Hereinafter, the reference sample construction step S1220 will be described in more detail.

In performing intra prediction on the current block or a sub block having a size and / or shape smaller than the current block based on the derived intra prediction mode, a reference sample used for prediction may be configured. Hereinafter, a description will be given based on the current block, and the current block may mean a sub block. The reference sample may be constructed using one or more reconstructed samples or sample combinations around the current block. In addition, filtering may be applied to construct the reference sample. In this case, each of the reconstructed samples on the plurality of reconstructed sample lines may be used as a reference sample. Alternatively, the reference sample may be configured after inter-sample filtering on the same reconstructed sample line. Alternatively, a reference sample may be configured after filtering between samples on different reconstructed sample lines. The configured reference sample may be represented by ref [m, n], a reconstructed sample around the sample, or a filtered sample thereof as rec [m, n]. In this case, m or n may be a predetermined integer value. If the size of the current block is W (horizontal) x H (vertical), when the top left sample position within the current block is (0, 0), the relative position of the closest top left reference sample relative to that sample position is determined. Can be set to (-1, -1).

As shown in FIG. 32, a reference sample may be constructed using one or more reconstructed sample lines adjacent to the current block.

For example, one line of the plurality of reconstructed sample lines illustrated in FIG. 32 may be selected, and a reference sample may be configured using the selected reconstructed sample line. The selected reconstructed sample line may be fixedly selected as a specific line among a plurality of reconstructed sample lines. Alternatively, the selected reconstructed sample line may be adaptively selected as a specific line among a plurality of reconstructed sample lines. In this case, an indicator for the selected reconstructed sample line may be signaled.

For example, a reference sample may be constructed using a combination of one or more reconstructed sample lines of the plurality of reconstructed sample lines shown in FIG. 32. As an example, the reference sample may consist of a weighted sum (or weighted average) of one or more reconstructed samples. The weight used for the weighted sum may be given based on the distance from the current block. In this case, the closer to the current block, the greater the weight may be given. For example, Equation 15 below may be used.

Alternatively, the reference sample may be configured using at least one of an average value, a maximum value, a minimum value, a median value, and a mode value of the plurality of reconstructed samples based on at least one of a distance from the current block or an intra prediction mode.

Alternatively, the reference sample may be configured based on a change (change amount) of values of a plurality of consecutive reconstructed samples. For example, the reference sample may be configured based on at least one or more of whether a value of two consecutive reconstructed samples differs by a threshold or more, and whether a value of a plurality of consecutive reconstructed samples changes continuously or discontinuously. For example, if rec [-1, -1] and rec [-2, -1] differ by more than a threshold value, ref [-1, -1] is determined as rec [-1, -1] or rec [- 1, -1] may be determined by applying a weighted average to which a predetermined weight is applied. For example, when a value of a plurality of consecutive reconstructed samples changes by n as the current block approaches, it may be determined that reference samples ref [-1, -1] = rec [-1, -1] -n.

At least one of the number, location, and configuration method of the reconstructed sample lines used in the reference sample configuration may include a boundary at the top or the left of the current block corresponding to at least one of a picture, slice, tile, and coded tree block (CTB). It may be determined differently in some cases.

For example, in constructing a reference sample using reconstructed

sample lines

1 and 2, when the upper boundary of the current block corresponds to the CTB boundary, the reconstructed sample line 1 is used for the upper side and the reconstructed sample line for the left side. 1 and 2 can be used.

For example, in constructing a reference sample using reconstructed sample lines 1 to 4, if the upper boundary of the current block corresponds to the CTB boundary, the reconstructed sample lines 1 to 2 are used for the upper side and the reconstructed sample for the left side. Lines 1 to 4 can be used.

For example, in constructing a reference sample using reconstructed sample line 2, when the upper boundary of the current block corresponds to the CTB boundary, the reconstructed sample line 1 is used for the upper side and the reconstructed sample line 2 for the left side. It is available.

The line of the reference sample configured through the above process may be one or more.

The method of configuring a reference sample on the upper side of the current block may be different from the method of configuring the reference sample on the left side.

Information indicating that a reference sample is configured by at least one or more of the above methods may be encoded / decoded. For example, information indicating whether a plurality of reconstructed sample lines are used may be encoded / decoded.

When the current block is divided into a plurality of sub blocks and each sub block has an independent intra prediction mode, a reference sample may be configured for each sub block.

As shown in FIG. 33, when the current block is 16x16 and 16 4x4 subblocks have independent intra prediction modes, the reference sample of each subblock is at least one of the following according to a scanning scheme for performing the prediction of the subblock. Can be configured in a manner.

For example, a reference sample of each subblock may be configured using N reconstructed sample lines adjacent to the current block. An example shown in FIG. 33 is the case where N is 1.

For example, when predicting a plurality of subblocks according to a raster scan order (1-> 2-> 3->… .15-> 16), in constructing a reference sample of the Kth subblock, A reference sample may be configured by using samples of at least one subblock among pre-encoded / decoded left, top, right top and bottom left ends.

For example, when predicting a plurality of subblocks according to the Z-scan order (1-> 2-> 5-> 6-> 3-> 4-> 7->… 12-> 15-> 16), K In configuring the reference sample of the first sub-block, a reference sample may be configured by using at least one sample of at least one sub-block among pre-encoded / decoded left, upper, upper right and lower left ends.

For example, a plurality of subblocks may be predicted in a zigzag-scan order (1-> 2-> 5-> 9-> 6-> 3-> 4->… 12-> 15-> 16). In the case of configuring the reference sample of the K-th subblock, the reference sample may be configured by using at least one subblock sample among the left, upper, upper right and lower left that are previously encoded / decoded.

For example, when predicting a plurality of subblocks according to a vertical scan order (1-> 5-> 9-> 13-> 2-> 6->… 8-> 12-> 16), In configuring a reference sample of the K-th subblock, a reference sample may be configured by using samples of at least one or more subblocks among the left, upper, upper right, and lower left that are previously encoded / decoded.

When predicting a plurality of subblocks according to a scan order other than the above scan order, reference is made by using samples of subblocks of the left, upper, upper right and lower left that are previously encoded / decoded in constructing a reference sample of the Kth subblock. Samples can be constructed.

In selecting the reference sample, an availability determination and / or padding of a block including the reference sample may be performed. For example, when a block including a reference sample is available, the corresponding reference sample may be used. On the other hand, if the block containing the reference sample is not available, one or more surrounding reference samples may be used to pad and replace the unused reference samples.

When the reference sample exists outside at least one of a picture, a tile, a slice, a coding tree block (CTB), and a predetermined boundary, it may be determined that the reference sample is not available.

When the current block is encoded by constrained intra prediction (CIP), if the block including the reference sample is encoded / decoded in the inter picture mode, it may be determined that the reference sample is not available.

If it is determined that the surrounding reconstructed samples are not available, the surrounding available reconstructed samples may be used to replace the unavailable samples. For example, as shown in FIG. 34, when there are available and unavailable samples, one or more available samples may be used to replace the unavailable samples.

The sample value of the insoluble sample may be replaced with the sample value of the available sample in a predetermined order. The soluble sample used to replace the insoluble sample may be a soluble sample adjacent to the insoluble sample. If there are no adjacent available samples, the first appearing or closest available sample may be used. The replacement order of the unavailable sample may be, for example, the order from the bottom left to the top right. Alternatively, the order may be from the upper right to the lower left. Or in the order of the upper left and / or lower left at the upper left corner. Or from the upper right corner and / or the lower left corner to the upper left corner.

As shown in FIG. 34, replacement of the unavailable sample may be performed in the order of the upper right sample starting from 0, which is the lower left sample position. In this case, the first four unavailable samples may be replaced with the value of the first appearing or nearest available sample a. The next thirteen unavailable samples can be replaced with the value of the last available sample b.

Alternatively, the insoluble sample can be replaced using a combination of available samples. For example, the average value of the available samples adjacent to both ends of the insoluble sample can be used to replace the insoluble sample. For example, in FIG. 34, the first four unavailable samples can be filled with the value of the available sample a, and the next thirteen unavailable samples can be filled with the average value of the available samples b and c. Alternatively, thirteen unavailable samples can be replaced with any value between the sample values of available samples b and c. In this case, the unavailable samples can be replaced with different values. For example, an insoluble sample may be replaced with a value closer to the value of a as it becomes closer to available sample a. Likewise, an unavailable sample can be replaced with a value closer to the value of b as it approaches the available sample b. That is, based on the distance from the insoluble sample to the available samples a and / or b, the value of the insoluble sample can be determined.

One or more of a plurality of methods including the above methods may optionally be applied for the replacement of an insoluble sample. The alternative method of the unavailable sample may be signaled by information included in the bitstream, or a method predetermined by the encoder and the decoder may be used. Alternatively, an alternative method of insoluble sample can be derived by a predetermined method. For example, an alternative method of insoluble samples can be selected based on the difference between the values of available samples a and b and / or the number of insoluble samples. For example, an alternative method may be selected based on the difference between the values of the two available samples and the threshold and / or the comparison of the number and threshold of the unavailable samples. For example, if the difference between the values of the two available samples is greater than the threshold and / or the number of unavailable samples is greater than the threshold, the unavailable samples may be replaced to have different values.

The filtering may be determined with respect to the configured one or more reference samples according to at least one of an intra prediction mode, a size and a shape of the block of the current block. When the filtering is applied, the filter type may vary according to at least one of an intra prediction mode, a size, and a shape of the current block.

For example, whether to apply filtering and / or type for each of the plurality of reference sample lines may be determined differently. For example, filtering may be applied to the first adjacent line and no filtering may be applied to the second line.

For example, the value to which the filtering is applied and the value to which the filtering is not applied may be used together for the reference sample.

For example, when the intra prediction mode (intraPredMode) of the decoded target block is the directional prediction mode, the difference value between the vertical directional mode (the mode corresponding to index = 26 when the directional mode is 33) and the horizontal directional mode ( In the case of 33 directional modes, a smaller value [minDistVerHor = Min (Abs (intraPredMode-26), abs (intraPredMode-10))] from the difference between the index and the mode corresponding to 10 may be obtained.

For example, the threshold for a 4x4 block is 10, the threshold for an 8x8 block is 7, the threshold for a 16x16 block is 1, the threshold for a 32x32 block is 0, and the threshold for a 64x64 block is 10. have.

If the minDistVerHor value is larger than the threshold value allocated to the corresponding block size (minDistVerHor> intraHorVerDistThresh), filtering may be performed. If the minDistVerHor value is smaller than or equal to, the filtering may not be performed.

36 is a diagram exemplarily illustrating whether filtering is performed according to a block size and / or an intra prediction mode. In FIG. 36, X may indicate that filtering is not performed and O may indicate that filtering is performed.

For example, as illustrated in FIG. 36, it may be determined whether filtering is performed on an encoding / decoding target block having 8 <= N _S <= 32 according to a block size and / or a directional prediction mode.

As another embodiment of applying filtering, bi-linear interpolation filtering may be performed on an encoding / decoding target block having a large block size. For example, a second derivative value in the vertical direction and the horizontal direction can be obtained for an encoding / decoding target block having a block size of N _S. When the second derivative is smaller than a certain threshold (eg, | p _ref (-1, -1)-2 xp _ref (N _S / 2, -1) + p _ref (N _S , -1) | < 2 ^Bd ^-C and / or p _ref (-1, -1)-2 xp _ref (-1, N _S / 2) + p _ref (-1, N _S ) | <2 ^Bd ^-C (B _d is a bit-depth, 1 <= C <= B _d positive integer), reference pixel p _ref (-1, y) = (N _s -1-y) / N _S xp _ref (-1, -1) + (y + 1) / N _S xp _ref (-1, N _S -1), for y = 0,... , N _S -1 or p _ref (x, -1) = (N _s -1-x) / N _S xp _ref (-1, -1) + (x + 1) / N _S xp _ref (N _S- 1, -1), for x = 0,... , N _S -1.

For example, at least one of a 3-tap filter, a 5-tap filter, a 7-tap filter, and an N-tap (N is positive integer) filter according to at least one of an intra prediction mode, a block size, and a shape of the current block. The above may be differently selected and applied to each of the plurality of reference sample lines.

Hereinafter, an intra prediction prediction step S1230 will be described in more detail.

An intra prediction may be performed on the current block or sub block based on the derived intra prediction mode and a reference sample. In the following detailed description, the current block may mean a sub block.

For example, non-directional intra prediction may be performed. The prediction mode in the non-directional view may be at least one of a DC mode and a planar mode.

The intra prediction of the DC mode may be performed using an average value of one or more reference samples among the configured reference samples. In this case, filtering may be applied to one or more prediction samples located at the boundary of the current block. The intra prediction of the DC mode may be adaptively performed based on at least one of the size and shape of the current block.

For example, as illustrated in (a) of FIG. 37, when the shape of the current block is square, prediction may be performed using an average value of reference samples on the top and left sides of the current block.

For example, as illustrated in (b) of FIG. 37, when the shape of the current block is a rectangle, the prediction may be performed using an average value of reference samples adjacent to the longer side among the horizontal and vertical lengths of the current block. .

For example, when the size of the current block falls within a predetermined range, predetermined samples are selected from reference samples on the top or left side of the current block, and prediction may be performed using an average value of the selected samples.

For example, the intra prediction of the DC mode may be performed using an average value of one or more reference samples among the configured reference samples. In this case, for example, Equation 16 below may be used.

In this case, filtering may be applied to one or more prediction samples located at the boundary of the current block. For example, filtering may be performed on the N plurality of columns and / or rows on the left and / or top of the current block. In this case, N may be a positive integer greater than one.

For example, when N = 1, as illustrated in FIG. 38, filtering may be performed on the top 1 row and / or the left 1 column of the target block. The filtering may be performed using Equation 17 below.

In-plane prediction in a planar mode may be performed by calculating a weighted sum considering a distance from the configured one or more reference samples according to the position of the prediction target sample in the screen of the current block.

For example, the prediction block may be obtained as a weighted sum of N reference samples depending on the position (x, y) of the sample to be predicted. N may be a positive integer, for example four.

39 is a diagram for describing intra prediction in a planar mode.

For example, as shown in FIG. 39, when the width and length of the encoding / decoding target block are 4 (N _S = 4), prediction at each pixel position (x, y) constituting the prediction block is performed. The pixel value may be derived by a weighted sum of the upper reference pixel (c), the left reference pixel (b), the upper right corner pixel (d) of the encoding / decoding target block, and the lower left corner pixel (a) of the encoding / decoding target block. have. For example, the derivation of the weighted sum may be performed using Equation 18 below.

For example, intra-directional prediction may be performed. The directional prediction mode may be at least one of a horizontal mode, a vertical mode, and a mode having a predetermined angle.

The intra prediction in the horizontal / vertical mode may be performed using one or more reference samples present on the horizontal / vertical line at the location of the intra prediction sample.

The intra prediction of the mode having the predetermined angle may be performed using one or more reference samples existing on and around the predetermined angle line at the position of the intra prediction sample. In this case, N reference samples may be used. N may be a positive integer such as 2, 3, 4, 5, 6. In addition, for example, prediction may be performed by applying an N-tap filter such as a 2-tap, 3-tap, 4-tap, 5-tap, 6-tap filter.

For example, intra prediction may be performed based on location information. In this case, the location information may be encoded / decoded, and the reconstructed sample block at the location may be derived into a prediction block in the screen of the current block. Alternatively, a block found by searching for a block similar to the current block in the decoder may be derived as a prediction block in the screen of the current block.

For example, intra prediction between color components may be performed. For example, an intra prediction of the color difference component may be performed using the reconstructed luminance component of the current block. Alternatively, an intra prediction may be performed on another color difference component Cr by using the restored one color difference component Cb of the current block.

Intra-prediction may be performed by combining one or more of the above-described various intra-prediction methods. For example, an intra prediction block for the current block may be configured through a weighted sum of blocks predicted using a predetermined non-directional prediction mode and blocks predicted using a predetermined directional prediction mode. have. In this case, the weight may be differently applied according to at least one or more of the prediction mode, the size, the shape of the block, and / or the location of the sample of the current block.

Alternatively, in combining the one or more intra prediction modes, the prediction block may be obtained through a weighted sum of a value predicted using the intra prediction mode for the current block and a value predicted using the predetermined mode in the MPM list. Can be configured.

Alternatively, intra prediction may be performed using one or more reference sample sets. For example, an intra prediction may be performed on the current block through a weighted sum of blocks predicted in the screen as reference samples without filtering to the configured reference samples and blocks predicted in the screen as reference samples to which filtering is applied. Can be.

In the process of performing the intra prediction, the filtering process using the reconstructed samples of the surroundings may be performed. In this case, the filtering process may or may not be performed according to at least one of the prediction mode, the size, the shape of the block, and / or the location of the sample of the current block. The filtering process may be included in a process of performing the intra prediction, and may be performed as one step. In performing the filtering process, at least one of a filter tap, a coefficient, an applied line number, and an applied sample number may be adaptively determined based on at least one of an intra prediction mode, a block size, and a shape of the current block.

The intra-prediction mode is performed by dividing the current block into sub-blocks and deriving the intra prediction mode for each sub block using the intra prediction mode of the neighboring block, and applying filtering to each sub block in the current block. can do. For example, a low-pass filter may be applied to the entire current block. Alternatively, a filter may be applied to samples located at the boundary of each subblock. Alternatively, a filter may be applied to the prediction block or the reconstructed block of each sub block, and one or more samples of the sub block to which the filter is applied may be used to perform intra prediction on a subsequent sub block.

When the current block is divided into subblocks and intra prediction is performed on each subblock, each subblock may mean at least one of a sub / decoding block, a prediction block, and a transform block. For example, when the size of the current block is 64x64 and the size of the subblock is 16x16, the intra prediction mode and / or the intra prediction may be performed for the prediction block which is each sub block. In this case, when the one or more subblocks are additionally divided into 8x8 or 4x4, each 8x8 or 4x4 block may mean a transform block and an intra prediction on the additionally divided block using the intra prediction mode of the 16x16 block. Can be performed.

In performing the intra-directional prediction, the current block may be encoded / decoded using at least one of N directional modes. In this case, N may be a positive integer including 33, 65, and the like. In this case, the prediction mode in each directional screen may have a predetermined angle value.

In the directional intra prediction, the current block may be encoded / decoded in M sample unit directional modes. M may be a positive integer. In this case, the directional mode in a sample unit may mean a mode for predicting by using the at least one prediction mode in the directional screen in units of one or more prediction targets in the current block.

In performing the intra-directional prediction, the configured reference sample may be reconstructed according to the directional prediction mode. For example, when the directional prediction mode is a mode that uses both reference samples existing on the left side and the upper side, one-dimensional array may be configured for the reference sample on the left side or the top side.

For example, as shown in FIG. 40, one or more of the reference samples present on the left side may be used to construct a one-dimensional array of the upper reference sample. In this case, the sample used to configure the upper reference sample among the left reference samples may vary according to the directional mode. The left reference sample may be moved to form an upper reference sample, or a weighted sum of one or more left reference samples may be used to construct an upper reference sample.

In performing the directional intra prediction, interpolated prediction of a real unit may be performed. For example, based on the angular parameter (intraPredAngle) corresponding to each directional prediction mode, the offset (iIdx) and / or weight (iFact) values for predictive sample interpolation according to the sample position in the current block are shown below. You can also decide together.

For example, in the case of assuming interpolation of 1/32 pel unit, the offset and the weight for the directional mode having the vertical direction may be determined as in Equation 19 below.

The prediction sample value may be determined differently according to the iFact value of Equation 19. For example, if iFact is nonzero, reference sample P _{1, ref} The location of the prediction in is a real unit rather than a full sample location. Accordingly, a prediction sample value at the target sample (x, y) position may be generated using a plurality of reference samples adjacent to the real position (eg, two reference samples adjacent to the left and right) as shown in Equation 20 below. In this case, the plurality of adjacent reference samples may be four or six adjacent to the left and right.

For example, when iFact is 0, a prediction sample value may be generated using Equation 21 below. Alternatively, the 3-tap [1/4: 2/4: 1/4] filter may be applied using the reference samples P _{1, ref} and the reference samples existing on the left and right.

In at least one of the horizontal and / or vertical modes of the directional prediction mode, filtering may not be performed on the reference sample. In addition, interpolation prediction for the reference sample may not be necessary. In addition, since the prediction may be performed using only the upper or left reference samples, a process of configuring a 1D array for the reference samples may not be necessary.

As shown in FIG. 41, in performing the prediction in the directional screen, a unit for applying the directional mode may be different. That is, prediction may be performed using one or more directional modes in units of at least one of samples, sample groups, and lines in the target block.

For example, prediction may be performed using a directional mode on a current block basis. Alternatively, prediction may be performed by using the directional mode in units of the prediction target sample lines in the current block. That is, prediction may be performed by using different directional modes for at least one of the horizontal and vertical lines in the current block. Alternatively, prediction may be performed by using a directional mode in units of a predetermined sample group in the current block. That is, prediction may be performed using different directional modes for groups including N samples in the current block. For example, prediction may be performed by using a directional mode in units of predicted samples in a current block. That is, prediction may be performed by using different directional modes for each prediction target sample in the current block.

When one directional prediction is performed on the basis of the current block, when the encoding target block includes a curve having many image characteristics, encoding efficiency may be deteriorated. To improve this, prediction may be performed using one or more directional modes in units of at least one of a sample, a sample group, and a line in the target block.

FIG. 41A illustrates a case where different directional modes are used for each sample unit in the target block. In the example shown in (a) of FIG. 41, a prediction value may be generated using reference samples located at angles of the respective directional modes on a sample basis.

FIG. 41B illustrates a case in which different directional modes are used in units of horizontal lines in the target block. In the example shown in (b) of FIG. 41, a prediction value may be generated using reference samples located at angles of the respective directional modes in units of horizontal lines.

FIG. 41C illustrates a case in which different directional modes are used in units of vertical lines in a target block. In the example illustrated in (c) of FIG. 41, a prediction value may be generated using reference samples positioned at angles of the respective directional modes in units of vertical lines.

FIG. 41D illustrates a case in which different directional modes are used in units of sample groups in a diagonal line direction in the target block. In the example illustrated in (d) of FIG. 41, a prediction value may be generated using reference samples located at angles of respective directional modes in units of sample groups in a diagonal line direction.

FIG. 41E illustrates a case where different directional modes are used in units of L-shape lines in the target block. In the example illustrated in (e) of FIG. 41, a prediction value may be generated using reference samples positioned at angles of the respective directional modes in units of right angle lines.

In addition to the example shown in FIG. 41, there may be a variety of methods for grouping one or more samples. For example, different directional modes may be applied in units of blocks generated by dividing the width and / or length by an arbitrary number.

In an embodiment using different directional modes in units of samples in the target block, the curvature parameter cuv and the weight parameter cw _i (i = 0, 1,…, N _S −1, N _S : block size) The position of the reference pixel for generating a prediction value of an arbitrary position (x, y) in the prediction block may be determined.

For example, in the case of the intra prediction from the upper right to the lower left, the position of the reference pixel for generating the prediction value of the arbitrary position (x, y) in the prediction block may be determined as shown in Equation 22 below. Can be.

In the intra prediction using Equation 22, the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move to the right. In addition, as the cuv value decreases, the curvature decreases, and the position of the reference pixels may move to the left (up to a position of x).

When the target block is NxM, cw _i may be a parameter including N weights that are the height of the block or the number of rows. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding row may be adjusted. For example cw _i As the value increases, the positions of the reference pixels used by the prediction pixels of the i ^th row may move to the right. Also, cw _i As the value decreases, the position of the reference pixels may move to the left (up to the position of x).

Therefore, various types of intra prediction may be performed by using a combination of the curvature parameter cuv and / or the weighted row parameter cw _i .

In order to generate a prediction pixel value, the above-described interpolated prediction in units of 1 / N pel may be performed. N may be a positive integer.

For example, when the position of the reference pixel of the prediction target pixel is an integer unit, the prediction target pixel predSamples [x] [y] may be derived to the reference pixel p (pos, -1). pos may refer to a position of a reference pixel.

For example, when the position of the reference pixel of the prediction target pixel is a real unit, predSamples [x] [y] is 1 for p (floor (pos), -1) and p (ceil (pos), -1). It can be derived as an interpolated predicted value in / N pel units. floor (pos) is an integer value less than or equal to pos and may mean a maximum value. ceil (pos) is an integer value greater than or equal to pos and may mean a minimum value.

As described above, p _ref may be converted into p _{1 and} _ref before generating the predictive sample value for convenience of calculation.

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (7, -1) in FIG. 42), the calculated positions of all reference pixels are in the maximum range of the available reference pixels. It can be used after it has been converted to normalized values.

For example, in the case of the intra prediction from the upper left to the lower right (type-1), the position of the reference pixel for generating a prediction value of an arbitrary position (x, y) in the prediction block is expressed in the following mathematical units. Equation 23 can be determined.

In the intra prediction using Equation 23, the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move to the left. In addition, as the cuv value decreases, the curvature decreases, and the position of the reference pixels may move to the right (up to the position of x).

When the target block is NxM, cw _i may be a parameter including N weights that are the height of the block or the number of rows. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding row may be adjusted. For example cw _i As the value increases, the positions of the reference pixels used by the prediction pixels of the i ^th row may move to the left. Also, cw _i As the value decreases, the positions of the reference pixels may move to the right (up to the position of x).

In order to generate the prediction pixel value, the above-described interpolated prediction in units of 1 / N pel may be performed. N may be a positive integer.

For example, when the position of the reference pixel of the prediction target pixel is an integer unit, the prediction target pixel predSamples [x] [y] may be derived to the reference pixel p (pos, -1).

For example, when the position of the reference pixel of the prediction target pixel is a real unit, predSamples [x] [y] is 1 for p (floor (pos), -1) and p (ceil (pos), -1). It can be derived as an interpolated predicted value in / N pel units.

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (-7, -1) in FIG. 44), the calculated positions of all reference pixels are the maximum range of the available reference pixels. It can be used after it has been converted to values normalized to.

For example, in the case of the intra prediction from the lower left to the upper right, the position of the reference pixel for generating the prediction value of the arbitrary position (x, y) in the prediction block may be determined as shown in Equation 24 below. Can be.

In the case of the intra prediction using Equation 24, the magnitude of the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move downward. Further, as the cuv value decreases, the curvature decreases, and the position of the reference pixels can move upward (up to the position of y).

If the target block is NxM, cw _i may be a parameter including M weights that are the width of the block or the number of columns. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding column may be adjusted. For example cw _i As the value increases, the positions of the reference pixels used by the prediction pixels in column i ^th may move downward. Also, cw _i As the value decreases, the position of the reference pixels may move upward (up to the position of y).

Various types of intra prediction may be performed by using a combination of the curvature parameter cuv and / or the weight column parameter cw _i .

For example, when the position of the reference pixel of the prediction target pixel is an integer unit, the prediction target pixel predSamples [x] [y] may be derived as the reference pixel p (-1, pos).

For example, if the position of the reference pixel of the prediction target pixel is a real unit, predSamples [x] [y] is 1 for p (-1, floor (pos)) and p (-1, ceil (pos)). It can be derived as an interpolated predicted value in / N pel units.

As described above, for convenience of calculation, p _ref may be converted into p _{1 and} ref before generating the predicted sample value.

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (-1, 7) in FIG. 46), the calculated positions of all reference pixels are in the maximum range of the available reference pixels. It can be used after it has been converted to fit-normalized values.

For example, in the case of the intra prediction from the upper left to the lower right (type-2), the position of the reference pixel for generating a prediction value of an arbitrary position (x, y) in the prediction block is expressed in the following mathematical unit: Equation 25 can be determined.

In the intra prediction using Equation 25, the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move upward. In addition, as the cuv value decreases, the curvature decreases, and the position of the reference pixels may move downward (up to the position of y).

If the target block is NxM, cw _i may be a parameter including M weights that are the width of the block or the number of columns. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding column may be adjusted. For example cw _i As the value increases, the positions of the reference pixels used by the prediction pixels of the column i ^th may move upward. Also, cw _i As the value decreases, the position of the reference pixels may move downward (up to the position of y).

Therefore, various types of intra prediction may be performed by using a combination of the curvature parameter cuv and / or the weight column parameter cw _i .

For example, when the position of the reference pixel of the prediction target pixel is a real unit, predSamples [x] [y] is 1 for p (-1, floor (pos)) and p (-1, ceil (pos)). It can be derived as an interpolated predicted value in / N pel units.

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (-1, -7) in FIG. 48), the calculated positions of all reference pixels are the maximum range of the available reference pixels. It can be used after it has been converted to values normalized to.

For example, in the case of the intra prediction from the top to the bottom left, the position of the reference pixel for generating the prediction value of the arbitrary position (x, y) in the prediction block may be determined as shown in Equation 26 below. Can be.

In the intra prediction using Equation 26, the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move to the right. Further, as the cuv value decreases, the curvature decreases, and the position of the reference pixels may move to the left (up to the position of x).

When the target block is NxM, cw _i may be a parameter including N weights that are the height of the block or the number of rows. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding row may be adjusted. For example, as the value of cw _i increases, the positions of reference pixels used by the prediction pixels of row i ^th may move to the right. Also, as the cw _i value decreases, the position of the reference pixels may move to the left (up to the position of x).

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (7, -1) in FIG. 50), the calculated positions of all reference pixels are in the maximum range of the available reference pixels. It can be used after it has been converted to fit-normalized values.

For example, in the case of an intra prediction from the top to the bottom right, the position of the reference pixel for generating a prediction value of an arbitrary position (x, y) in the prediction block may be determined as shown in Equation 27 below. have.

In the intra prediction using Equation 27, the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move to the left. In addition, as the cuv value decreases, the curvature decreases, and the position of the reference pixels may move to the right (up to the position of x).

When the target block is NxM, cw _i may be a parameter including N weights that are the height of the block or the number of rows. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding row may be adjusted. For example, as the value of cw _i increases, the positions of reference pixels used by the prediction pixels of row i ^th may move to the left. Also, as the cw _i value decreases, the position of the reference pixels may move to the right (up to the position of x).

For example, when the position of the reference pixel of the prediction target pixel is an integer unit, the prediction target pixel predSamples [x] [y] may be derived as p (pos, -1).

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (-7, -1) in FIG. 52), the calculated positions of all reference pixels are the maximum range of the available reference pixels. It can be used after it has been converted to values normalized to.

For example, in the case of the intra prediction from the left to the upper right, the position of the reference pixel for generating the prediction value of the arbitrary position (x, y) in the prediction block may be determined as shown in Equation 28 below. have.

In the intra prediction using Equation 28, the magnitude of the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the position of the reference pixels may move downward. Further, as the cuv value decreases, the curvature decreases, and the position of the reference pixels can move upward (up to the position of y).

If the target block is NxM, cw _i may be a parameter including M weights that are the width of the block or the number of columns. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding column may be adjusted. For example, as the value of cw _i increases, the positions of the reference pixels used by the prediction pixels of the column i ^th may move downward. Also, as the cw _i value decreases, the position of the reference pixels may move upward (up to the position of y).

Therefore, various types of intra prediction may be performed by combining the curvature parameter cuv and the weight column parameter cw _i .

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (-1, 7) in FIG. 54), the calculated positions of all reference pixels are in the maximum range of the available reference pixels. It can be used after it has been converted to fit-normalized values.

For example, in the case of the intra prediction from the left to the bottom right, the position of the reference pixel for generating a prediction value of an arbitrary position (x, y) in the prediction block may be determined as shown in Equation 29 below. Can be.

In the intra prediction using Equation 29, the curvature may be adjusted by adjusting the cuv. cuv can have a real number greater than or equal to zero. For example, as the cuv value increases, the curvature increases, and the positions of the reference pixels may move upward. Also, as the cuv value decreases, the curvature decreases, and the position of the reference pixels can move downward (up to the position of y).

If the target block is NxM, cw _i may be a parameter including M weights that are the width of the block or the number of columns. Each weight may have a real number greater than or equal to zero. By adjusting cw _i , the position of the reference pixel used by the prediction pixel included in the corresponding column may be adjusted. For example, as the value of cw _i increases, the positions of the reference pixels used by the prediction pixels of the column i ^th may move upward. In addition, as the value of cw _i decreases, the position of the reference pixels may move downward (up to the position of y).

If the position pos of the reference pixel exceeds the maximum range of available reference pixels (P (-1, -7) in FIG. 56), the calculated positions of all reference pixels are the maximum range of the available reference pixels. It can be used after it has been converted to values normalized to.

In the embodiment described with reference to FIGS. 42 to 57, one curvature parameter cuv is applied to the current block, and one weight parameter cw is applied to the row or column of the current block. However, it is not necessarily limited thereto. That is, one or more curvature parameters cuv _i and / or one or more weight parameters cw _i may be applied to the current block. For example, as described with reference to FIG. 41, different curvature parameters may be provided in pixel units, horizontal line units, vertical line units, diagonal line units, right angle line units, sub block units, and / or any pixel group units of the current block. cuv _i ) and / or weight parameter cw _i may be applied.

As illustrated in FIG. 58, intra-sample prediction may be performed based on the intra prediction mode selected on a block basis. In this case, the prediction in the sample unit screen may be additionally performed.

For example, when the selected intra prediction mode is a non-directional mode (PLANAR_MODE or DC_MODE), only prediction of a sample unit may not be performed.

In (a) of FIG. 58, when the intra prediction mode of the selected block is included in the range of A, at least one or more of predictions in a sample unit in the lower left-> upper right direction and the left-> upper right direction are performed. Can be.

Alternatively, in (a) of FIG. 58, when the intra prediction mode of the selected block is included in the range of B, among predictions in the sample unit in the upper left-> lower right (Type2) direction and the left-> lower right direction. At least one or more may be performed.

Alternatively, in (a) of FIG. 58, when the intra prediction mode of the selected block is included in the range of C, among predictions in the sample unit in the upper left-> lower right (Type1) direction and the upper-lower right direction; At least one or more may be performed.

Alternatively, in (a) of FIG. 58, when the intra prediction mode of the selected block is included in the range of D, at least one or more of predictions in a sample unit in the upper right-> lower left direction and the upper-> lower left direction. Can be performed.

Alternatively, in (b) of FIG. 58, when the intra prediction mode of the selected block is included in the range of A, at least one or more predictions of the sample units in the left-> right-bottom and left-> top-right directions are performed. can do.

Alternatively, in (b) of FIG. 58, when the intra prediction mode of the selected block is included in the range of B, at least one or more of predictions in a sample unit in the top-> bottom left and top-> bottom directions are performed. Can be done.

59 is a view for explaining an embodiment of predicting a residual signal.

The residual signal prediction may be additionally performed on the residual signal configured from the intra prediction.

In-picture prediction predicts the current block using samples of pre-coded / decoded neighboring blocks as reference samples. Therefore, as the distance between the sample of the current block and the reference sample increases, the residual signal tends to increase, which may result in a decrease in coding efficiency.

In order to further reduce the residual signal, prediction of the residual signal may be additionally performed in units of a current block or a sub block.

A search range may be set for neighboring blocks that are pre-coded / decoded and reconstructed before the current block. The search range may be set differently according to the size, shape, split depth, and / or intra prediction mode of the current block.

For example, all blocks restored before the current block may be set as a search range. If the search range includes blocks located to the left of the current block, blocks located at the top left, blocks located at the top, and / or blocks located at the top right, some areas of the reconstructed block may not be currently encoded or have not yet been encoded. It may include blocks after the current block. In this case, the corresponding sample value may be padded by using the available sample value in the reconstruction block, or the blocks may be excluded from the search range.

For example, N blocks among the blocks restored before the current block may be set as a search range. In this case, N may be a positive integer of 1 or more.

For example, as illustrated in FIG. 59, when the horizontal length of the current block CUR_BLK is W, the vertical length is H, and the position of the upper left pixel of the current block is defined as (0, 0), (-2 * W, -2 * H), (-W, -2 * H), (0, -2 * H), (W, -2 * H), (-2 * W, -H), (-W 10 reconstruction blocks containing pixels at positions (-H), (0, -H), (W, -H), (-2 * W, 0), (-W, 0) Can be.

For example, when the current block is a non-square block having different lengths W and H, the search range may be set depending on the W and / or H values. For example, for a non-square block of WxH, the search range may be set to (K * W) x (L * H) in the reconstructed adjacent blocks area. In this case, K and L may each be a positive integer of 1 or more.

The prediction block of the current block may be configured by using the intra prediction mode (predModeIntra) of the current block determined by performing the intra prediction among the aforementioned various intra prediction modes.

For example, in FIG. 59, a prediction block configured using predModeIntra may be represented as PRD_BLK_best.

In addition to the prediction block PRD_BLK_best configured through predModeIntra, one or more prediction blocks of the current block may be configured.

For example, at least one additional prediction block may be configured using at least one of prediction modes in all directional / non-directional pictures.

For example, an additional prediction block may be configured using N intra prediction modes adjacent to predModeIntra based on predModeIntra. In this case, N may be a positive integer of 1 or more. For example, as shown in FIG. 59, when N = 2, two additional prediction blocks PRD_BLK_plus_one and PRD_BLK_minus_one may be configured. For example, when predModeIntra is a directional mode, an additional prediction block (PRD_BLK_plus_one) may be configured using predModeIntra + 1, and another additional prediction block may be configured using predModeIntra-1. The number added to or subtracted from the predModeIntra may be a positive integer of 1 or more.

For example, an additional prediction block may be configured using N adjacent intra prediction modes based on an angle formed with predModeIntra. In this case, N may be a positive integer of 1 or more. In this case, when the angle is θ, the additional prediction block may be configured by using the intra prediction mode included in the θ angle range from the predModeIntra reference −θ to + θ.

For example, M additional prediction blocks may be configured by combining N additional prediction blocks configured using N intra picture modes. At this time, M and N may be a positive integer. For example, when predModeIntra is PLANAR_MODE, which is a non-directional mode, an additional prediction block PRD_BLK_plus_one may be configured using DC_MODE, and another additional prediction block PRD_BLK_minus_one may be configured by a weighted sum of PRD_BLK_best and PRD_BLK_plus_one. Alternatively, when predModeIntra is a non-directional mode DC_MODE, an additional prediction block PRD_BLK_plus_one may be configured using PLANAR_MODE, and another additional prediction block PRD_BLK_minus_one may be configured by a weighted sum of PRD_BLK_best and PRD_BLK_plus_one. Alternatively, when predModeIntra is ANGULAR_MODE, which is a directional mode, an additional prediction block PRD_BLK_plus_one may be configured using ANGULAR_MODE, and another additional prediction block PRD_BLK_minus_one may be configured by a weighted sum of PRD_BLK_best and PRD_BLK_plus_one.

A plurality of difference blocks may be obtained using at least one of the current block and the configured plurality of prediction blocks. For example, it is possible to construct differential blocks between the current block and the predicted blocks configured using all the directional / non-directional mode. For example, the differential blocks between the N + 1 prediction blocks and the current block configured by using N intra prediction modes adjacent to predModeIntra based on predModeIntra and an angle or intra prediction mode may be configured. In this case, N may be a positive integer of 1 or more. For example, as shown in FIG. 59, when N = 2, three difference blocks can be configured as follows.

For example, the difference block RES_BLK_best between the current block and PRD_BLK_best can be obtained. For example, the difference block RES_BLK_plusone between the current block and PRD_BLK_plus_one can be obtained. For example, the difference block RES_BLK_minusone between the current block and PRD_BLK_minus_one can be obtained.

For example, N additional prediction blocks are constructed using N intra-picture modes, and M additional prediction blocks are constructed from the combination of N predicted blocks (where M and N are positive integers). It is possible to configure difference blocks between the prediction blocks and the current block.

A process of obtaining an optimal intradisplacement vector (IDV) for all samples within the search range may be performed. At this time, IDV may be defined as a vector (x, y) from the upper left sample position of the current block to the sample position within the search range, as shown in FIG. 59.

For each IDV, the recovery block REC_BLK having the same size as the current block can be configured by setting the sample position indicated by the IDV to (0,0).

One or more residual signal blocks RES_BLK_IDV for the reconstructed block REC_BLK configured at the position indicated by the IDV may be configured using at least one of PRD_BLK_best and additionally configured prediction blocks.

For example, when using N additional prediction blocks, N + 1 residual signal blocks for a reconstructed block REC_BLK configured at a location indicated by IDV may be configured using Equation 30 below.

For example, when using two additional prediction blocks as shown in FIG. 59, three residual signal blocks may be configured using Equation 31 below for the reconstructed block REC_BLK configured at a location indicated by IDV.

Second order residual blocks may be configured by the number of prediction blocks applied to the reconstructed blocks in the search region at the location indicated by each IDV.

As illustrated in FIG. 60, the secondary residual signal block RES_BLK_SEC may be obtained through a difference between RES_BLK_'MODE 'and RES_BLK_IDV_'MODE'. In this case, 'MODE' may be a prediction mode within a specific screen.

For example, when N prediction blocks are applied to the reconstruction block, N secondary residual signal blocks for the reconstruction block RES_BLK may be configured using Equation 32 below.

For example, as shown in FIG. 60, when using the prediction mode generated using predModeIntra and two additional prediction blocks, three secondary residual signal blocks may be configured for the reconstructed block REC_BLK using Equation 33 below. Can be.

In the reconstruction block at the location indicated by each IDV in the search region, the residual signal block and the cost at RES_BLK_best of which the cost function according to rate-distortion optimization among the second residual signal blocks RES_BLK_SEC is minimum The function values may be compared to determine whether to perform residual signal prediction. Whether to perform the residual signal prediction may be indicated by using, for example, an indicator SRP_flag (Second order Residual Prediction). For example, when performing residual signal prediction, a first value may be allocated to SRP_flag, and when not performing, a second value may be allocated. In this case, the first value may be 1 and the second value may be 0.

For example, when the minimum cost function value of the secondary residual signal blocks is smaller than the cost function value generated in RES_BLK_best, the first value may be assigned to SRP_flag. In addition, at least one or more of the SRP_flag, IDV, and the intra prediction mode used for generating the secondary residual signal block having the minimum cost function value, and the secondary residual signal of the RES_BLK_SEC may be encoded or decoded in or from the bitstream. have.

For example, when the minimum cost function value of the secondary residual signal blocks is greater than or equal to the cost function value generated in RES_BLK_best, a second value may be assigned to SRP_flag. In addition, at least one or more of the residual signals of SRP_flag, predModeIntra, and RES_BLK_best may be encoded or decoded in or from the bitstream.

While repeating the above process for all IDVs pointing to all samples in the search region, all IDVs pointing to the secondary residual signal block having a cost function less than the cost function value of RES_BLK_best can be determined. Of all the determined IDVs, the IDV with the lowest cost function value may be finally selected.

61 is a diagram to describe an embodiment of a residual signal prediction.

CUR_BLK represents the current block to be encoded / decoded. RES_BLK may be a primary residual signal and represents a residual signal block between the prediction block for the current block and CUR_BLK. The prediction block may be any one of a plurality of prediction blocks configured in an encoder / decoder for the current block.

IDV_REC_BLK represents a recovery block constructed from IDV. RES_BLK_IDV represents a residual signal block between IDV_REC_BLK and the prediction block for the current block. The prediction block may be any one of a plurality of prediction blocks configured in an encoder / decoder for the current block.

RES_BLK_SEC represents a secondary residual signal block between RES_BLK and RES_BLK_IDV.

In FIG. 61, when the cost function value of RES_BLK_SEC is smaller than the cost function value of RES_BLK, a first value may be assigned to SRP_flag. In addition, at least one or more of the SRP_flag, IDV, and the intra prediction mode used for generating the secondary residual signal block having the minimum cost function value, and the secondary residual signal of the RES_BLK_SEC may be encoded or decoded in or from the bitstream. have. The first value may be 0 or 1.

In FIG. 61, when the cost function value of RES_BLK_SEC is greater than or equal to the cost function value of RES_BLK, a second value may be allocated to SRP_flag. In addition, at least one or more of the primary residual signal of SRP_flag, predModeIntra, and RES_BLK may be encoded or decoded in or from the bitstream. The second value may be 0 or 1.

The residual signal of the current block may be derived using at least one of the first residual signal and the second residual signal. The neighboring block IDV_REC_BLK may be a block indicated by the above-described IDV, or may be a block adjacent to the current block (eg, a previously reconstructed block of the current block such as a left side, a top side, and the like). The IDV may be encoded as it is, or may be encoded by differential coding with IDV of another block in the current picture. The RES_BLK_IDV may be derived by subtracting a predetermined prediction block from the reconstructed neighboring block. In this case, the intra prediction mode for generating the prediction block may be a neighboring block IDV_REC_BLK or an intra prediction mode of the current block, or may be a mode pre-committed to an encoder / decoder. Alternatively, the predetermined prediction block may be set to be the same as the prediction block for the current block. Alternatively, an upper block including the current block may be defined, and a residual signal shared by blocks belonging to the upper block may be defined as a second residual signal. The residual prediction technique based on the second residual signal described above may be selectively performed based on a predetermined flag SRP_flag. The flag may be signaled from at least one of a sequence, a picture, a slice, and a block unit. Alternatively, in certain cases, the flag may be derived with a fixed value pre-committed to the encoder / decoder according to the size, shape and / or depth of the current block.

An indicator (flag, flag) indicating whether residual signal prediction is performed in the current block may be encoded / decoded. For example, the indicator may be SRP_flag and may be encoded / decoded for at least one unit of the current block or subblock.

One or more of IDV, information required for the residual signal prediction, the intra prediction mode selected in the residual signal prediction of the current block (in FIG. 61, mode_x) and other encoding parameter information may be encoded or decoded in or from the bitstream. have.

The IDV information of the current block may be predicted / decoded using the IDV of the neighboring block. For example, the minimum, maximum, median, average, mode, or weighted sum of IDVs of adjacent blocks and the difference value of IDVs of the current block may be encoded / decoded.

Alternatively, when at least one of the IDVs of the neighboring blocks is the same as the IDV of the current block, the encoder may construct an IDV list using the IDVs of the neighboring blocks according to a predefined method. The encoder is IDV information of the current block and includes information (eg, a flag) indicating that at least one of the IDVs of adjacent blocks is the same as the IDV of the current block and / or information indicating the same IDV in the IDV list For example, the index may be encoded. When the flag information indicates that at least one of the IDVs of the neighboring blocks is the same as the IDV of the current block, the decoder may construct an IDV list according to the predefined method. The decoder may derive the IDV of the current block by using the configured IDV list and the index information.

Intra-prediction is performed on the current block in operation S6201, and an optimal intra-prediction mode predModeIntra may be determined in operation S6202. In operation S6202, a prediction block PRD_BLK_best using an optimal intra prediction mode may be generated. A residual block RES_BLK_bset between the prediction block PRD_BLK_best and the current block generated using predModeIntra may be obtained (S6203).

N additional intra prediction modes may be determined based on the predModeIntra determined in operation S6202 (S6204). In step S6205, N + 1 prediction blocks PRD_BLK_'mode 'may be generated from N + 1 intra prediction modes including predModeIntra and N additional intra prediction modes. In step S6206, N + 1 residual blocks RES_BLK_'mode 'may be obtained using the current block and N + 1 prediction blocks PRD_BLK_'mode'.

In operation S6207, the IDV may be moved by using a pixel-by-pixel search or a specific search method within the search range. The recovery block REC_BLK_IDV may be obtained at the determined IDV position (S6208). In step S6209, N + 1 IDV residual blocks RES_BLK_IDV_'mode 'may be obtained using REC_BLK_IDV and the N + 1 prediction blocks PRD_BLK_'mode'.

In step S6210, N + 1 secondary residual blocks RES_BLK_SEC_'mode 'may be obtained using RES_BLK_'mode' and the corresponding RES_BLK_IDV_'mode '.

In step S6211, each of the RES_BLK_SEC_'mode 'and the RD cost of the RES_BLK_best may be compared. When the RD cost of at least one RES_BLK_SEC_'mode 'is smaller than the RD cost of RES_BLK_best (YES in S6211), the process may move to step S6212. If not (No in S6211), the flow proceeds to step S6213.

In step S6212, the SRP_flag is assigned a first value (eg, 1), and an optimal cost may be determined as an RD cost of the at least one RES_BLK_SEC_'mode '.

In step S6213, it may be determined whether the current IDV is the last IDV in the search range. If the current IDV is not the last IDV (NO in S6213), the flow advances to step S6207, where the operation for the next IDV can be repeated. If the current IDV is the last IDV (YES in S6213), the flow proceeds to step S6214.

In operation S6214, it may be determined whether the SRP_flag is the first value (eg, 1). If SRP_flag is the first value (Yes in S6214), the process may proceed to step S6215, and if SRP_flag is not the first value (No in S6214), the process may proceed to step S6216.

In step S6215, of the secondary residual signals of the SRP_flag, IDV, and the second residual signal block of the in-prediction mode ('mode' used in PRED_BLK_'mode ') and RES_BLK_SEC_'mode' used for generating the secondary residual signal block having the minimum cost function value. At least one or more may be determined as an encoding target, and may be encoded in step S6217.

In operation S6216, at least one or more of the primary residual signals (eg, RES_BLK_best) of SRP_flag, predModeIntra, and RES_BLK may be determined to be encoded, and may be encoded in operation S6217.

If the IDV is not signaled, the decoder can derive the IDV by performing the same search process performed by the encoder.

In operation S6301, related information included in the bitstream may be decoded.

When SRP_flag is not the first value (eg, 1) (No in S6302), the process may be performed in step S6303.

In operation S6303, a prediction block PRD_BLK_best corresponding to predModeIntra may be generated. In addition, the residual block RES_BLK_best may be decoded.

In operation S6304, a reconstruction block may be generated using PRD_BLK_best and RES_BLK_best.

If SRP_flag is the first value (eg, 1) (Yes in S6302), steps S6305, S6306, and S6307 may be performed.

In operation S6305, the secondary residual block RES_BLK_SEC_'mode 'may be decoded.

In operation S6306, a reconstruction block REC_BLK_IDV corresponding to the decoded IDV may be generated.

In operation S6307, a prediction block PRD_BLK_'mode 'corresponding to the decoded' mode 'may be generated.

In step S6308, an IDV residual block RES_BLK_IDV_'mode 'may be generated using the generated REC_BLK_IDV and PRD_BLK_'mode'.

In operation S6309, the residual block RES_BLK may be generated using the generated RES_BLK_SEC_'mode 'and RES_BLK_IDV_'mode'.

In step S6310, a reconstruction block may be generated using the generated RES_BLK and PRD_BLK_'mode '.

As described above, when the IDV is not signaled, the decoder may perform the same search process performed by the encoder to derive the IDV.

The internal / decoding process of the screen may be performed on each of luminance and chrominance signals. For example, at least one method of deriving intra prediction mode, block division, reference sample configuration, and performing intra prediction may be differently applied to the luminance signal and the chrominance signal in the intra / decoding process.

The internal / decoding process for the luminance and color difference signals may be performed in the same manner. For example, at least one of deriving intra prediction mode, block division, reference sample configuration, and performing intra prediction may be equally applied to the color difference signal in the intra / decoding process applied to the luminance signal.

The above methods can be performed in the same way in the encoder and the decoder. For example, at least one or more methods of intra prediction mode derivation, block division, reference sample configuration, and intra prediction may be applied to the encoder and the decoder in the intra / decoding process. In addition, the order of applying the above methods may be different in the encoder and the decoder. For example, in performing the intra / decoding of the current block, the encoder configures a reference sample, and then encodes the intra prediction mode determined by performing one or more intra predictions.

The above embodiments of the present invention may be applied according to the size of at least one of a coding block, a prediction block, a block, and a unit. The size here may be defined as a minimum size and / or a maximum size for the above embodiments to be applied, or may be defined as a fixed size to which the above embodiments are applied. In addition, in the above embodiments, the first embodiment may be applied at the first size, and the second embodiment may be applied at the second size. That is, the embodiments may be applied in combination according to the size. In addition, the above embodiments of the present invention can be applied only when the minimum size or more and the maximum size or less. That is, the above embodiments can be applied only when the block size is included in a certain range.

For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 8x8 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 16x16 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 32x32 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 64x64 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 128x128 or more. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 4x4. For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 8x8 or less. For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 16x16 or less. For example, the above embodiments may be applied only when the size of an encoding / decoding target block is 8x8 or more and 16x16 or less. For example, the above embodiments may be applied only when the size of the encoding / decoding target block is 16x16 or more and 64x64 or less.

The above embodiments of the present invention can be applied according to a temporal layer. A separate identifier is signaled to identify the temporal layer to which the embodiments are applicable and the embodiments can be applied to the temporal layer specified by the identifier. The identifier here may be defined as a minimum layer and / or a maximum layer to which the embodiment is applicable, or may be defined as indicating a specific layer to which the embodiment is applied.

For example, the above embodiments may be applied only when the temporal layer of the current image is the lowest layer. For example, the above embodiments may be applied only when the temporal layer identifier of the current image is zero. For example, the above embodiments may be applied only when the temporal layer identifier of the current image is one or more. For example, the above embodiments may be applied only when the temporal layer of the current image is the highest layer.

The reference picture set used in the process of reference picture list construction and reference picture list modification as in the embodiment of the present invention is one of L0, L1, L2, and L3. At least one reference picture list may be used.

According to the embodiment of the present invention, when calculating the boundary strength in the deblocking filter, one or more motion vectors of the encoding / decoding target block may be used. Where N represents a positive integer of 1 or more, and may be 2, 3, 4, or the like.

When predicting motion vectors, the motion vectors are in 16-pel units, 8-pel units, 4-pixel units, integer-pel units, 1/2 -1 / 2-pel units, 1 / 4-pel units, 1 / 8-pixel units 1 / 8-pel, 1 / 16-pixel units The above embodiments of the present invention may also be applied when the device has at least one of 1), 1 / 32-pixel (1 / 32-pel) units, and 1 / 64-pixel (1 / 64-pel) units. In addition, when performing motion vector prediction, a motion vector may be selectively used for each pixel unit.

A slice type to which the above embodiments of the present invention are applied is defined, and the above embodiments of the present invention may be applied according to the corresponding slice type.

For example, when the slice type is Tri-predictive (T) -slice, a prediction block is generated using at least three or more motion vectors, and a weighted sum of at least three or more prediction blocks is calculated to calculate a block to be encoded / decoded. It can be used as the final prediction block of. For example, when the slice type is a Q-quad-slice, a prediction block is generated using at least four or more motion vectors, and a weighted sum of at least four or more prediction blocks is calculated to calculate a block to be encoded / decoded. It can be used as the final prediction block of.

The above embodiments of the present invention can be applied not only to inter prediction and motion compensation methods using motion vector prediction, but also to inter prediction and motion compensation methods using skip mode and merge mode.

The shape of the block to which the embodiments of the present invention are applied may have a square shape or a non-square shape.

In the above-described embodiments, the methods are described based on a flowchart as a series of steps or units, but the present invention is not limited to the order of steps, and certain steps may occur in a different order or simultaneously from other steps as described above. Can be. Also, one of ordinary skill in the art appreciates that the steps shown in the flowcharts are not exclusive, that other steps may be included, or that one or more steps in the flowcharts may be deleted without affecting the scope of the present invention. I can understand.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Embodiments according to the present invention described above may be implemented in the form of program instructions that may be executed by various computer components, and may be recorded in a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the computer-readable recording medium may be those specially designed and configured for the present invention, or may be known and available to those skilled in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs, DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the process according to the invention, and vice versa.

Although the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided to assist in a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations can be made from these descriptions.

Accordingly, the spirit of the present invention should not be limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the appended claims, fall within the scope of the spirit of the present invention. I will say.

The present invention can be used to encode / decode an image.

Claims

An image decoding method for performing intra prediction on a current block,

Decoding first information indicating whether a residual signal prediction for predicting a residual block of the current block is performed; And

And performing the residual signal prediction when the first information indicates a first value.
The method of claim 1,

The residual signal prediction is performed based on a decoded reconstruction block.
The method of claim 2,

Decoding an IDV (Inta Displacement Vector),

And the decoded reconstruction block is specified by the decoded IDV.
The method of claim 2,

Decoding the intra prediction mode used for the residual signal prediction; And

And generating a prediction block of the reconstructed block based on the decoded intra prediction mode.
The method of claim 4, wherein

Generating a residual block of the reconstruction block based on the reconstruction block and the prediction block of the reconstruction block,

The residual block of the reconstruction block is a prediction block of the residual block of the current block.
The method of claim 5,

Decoding a second order residual block of the current block; And

Generating a residual block of the current block based on the prediction block of the residual block of the current block and the secondary residual block.
The method of claim 3,

If the information about the IDV is not included in the bitstream,

Decoding the IDV,

An image decoding method performed by selecting one of a plurality of IDVs included in a predetermined search range by using a predetermined search method.
The method of claim 7, wherein

And the predetermined search method is the same search method used in the video encoding method.
An image decoding apparatus including an intra picture prediction unit that performs an intra picture prediction on a current block,

The intra prediction unit decodes first information indicating whether a residual signal prediction for predicting a residual block of the current block is performed, and predicting the residual signal when the first information indicates a first value. An image decoding apparatus for performing.
In the image encoding method for performing intra prediction on a current block,

Performing residual signal prediction to predict a residual block of the current block; And

And encoding first information indicating whether the residual signal prediction is performed.
The method of claim 10,

The residual signal prediction is performed based on a decoded reconstruction block.
The method of claim 11,

And encoding an IDV (Inta Displacement Vector) that specifies the decoded reconstruction block.
The method of claim 11,

Determining an intra prediction mode used for the residual signal prediction;

Generating a prediction block of the reconstruction block based on the determined intra prediction mode; And

And encoding the determined intra prediction mode.
The method of claim 13,

Generating a residual block of the reconstruction block based on the reconstruction block and the prediction block of the reconstruction block,

The residual block of the reconstruction block is a prediction block of the residual block of the current block.
The method of claim 14,

Generating a secondary residual block of the current block based on the prediction block of the residual block of the current block and the residual block of the current block; And

And encoding the second residual block of the current block.
The method of claim 12,

And the IDV is determined by selecting one of a plurality of IDVs included in a predetermined search range by using a predetermined search method.
The method of claim 16,

The search range is determined based on at least one of the size, shape, segmentation depth, and intra prediction mode of the current block.
The method of claim 16,

The predetermined search method is

And comparing the cost function value of the residual block of the current block with the cost function value of the secondary residual block of the current block.
An image encoding apparatus including an intra prediction unit for performing intra prediction on a current block,

And the intra prediction unit is configured to perform residual signal prediction for predicting a residual block of the current block and to encode first information indicating whether the residual signal prediction is performed.
A recording medium storing a bitstream generated by an image encoding method for performing intra prediction on a current block.

The video encoding method,

Performing residual signal prediction to predict a residual block of the current block; And

And encoding first information indicating whether the residual signal prediction is performed.