WO2018143670A1

WO2018143670A1 - Method and device for encoding/decoding image

Info

Publication number: WO2018143670A1
Application number: PCT/KR2018/001341
Authority: WO
Inventors: 문주희; 하재민; 원동재; 임성원
Original assignee: 세종대학교 산학협력단
Priority date: 2017-01-31
Filing date: 2018-01-31
Publication date: 2018-08-09

Abstract

The present invention relates to a method and device for encoding/decoding an image, and a method or device for encoding an image according to an embodiment of the present invention can encode the position of a reference coefficient in a current conversion block to be encoded, and encode skip region information about a skip region selected on the basis of the position of the reference coefficient. The skip region information can indicate whether coefficients in the skip region have the same coefficient value.

Description

Method and apparatus for encoding / decoding video

The present invention relates to a method and apparatus for encoding / decoding video signals, and more particularly, to entropy encoding and decoding.

Recently, the demand for multimedia data such as moving pictures is rapidly increasing on the Internet. However, the speed at which the bandwidth of a channel develops is difficult to keep up with the rapidly increasing amount of multimedia data. Given this situation, the International Standardization Organization's Video Coding Expert Group (VCEG) and ISO / IEC's Moving Picture Expert Group (MPEG) launched the video compression standard HEVC (High Efficiency Video Coding) in February 2014. Version 1 was enacted.

HEVC has a variety of technologies such as intra picture prediction, inter picture prediction, transform, quantization, entropy coding, and in-loop filters. Information that is input of entropy encoding is generated using various methods. As the size of an input image or a unit block to be encoded or decoded is increased, data to be entropy-encoded may rapidly increase.

In order to solve the above problems, the present invention has a main object to provide a more efficient entropy encoding and decoding technique.

In addition, the present invention has a main object to reduce the amount of data to be encoded by entropy encoding or decoding using a skip region.

In addition, the present invention has a main object to improve arithmetic coding and arithmetic decoding performance by effectively selecting probability information applied to encoding or decoding each symbol during context-adaptive arithmetic coding and decoding.

An image encoding method or encoding apparatus according to an embodiment of the present invention encodes a position of a reference coefficient in a current transform block to be encoded and encodes skip region information on a skipped region selected based on the position of the reference coefficient. Can be.

The skip region information may indicate whether the coefficients in the skip region have the same coefficient value.

A video encoding method or encoding apparatus according to another embodiment of the present invention obtains binarized information by binarizing a value of a transform coefficient, and encodes the binarized information according to a position of the transform coefficient in a transform block. Probability information to be applied can be determined.

The probability information to be applied to the encoding of the binarized information may be determined according to which region the transform coefficient is located in a transform block divided into a plurality of regions.

An image encoding method or encoding apparatus according to another embodiment of the present invention encodes a position of a reference coefficient in a current transform block to be encoded and encodes skip region information on a skipped region selected based on the position of the reference coefficient. In addition, binarized information may be obtained by binarizing a value of a transform coefficient not included in the skip region, and a probability information table to be applied to encoding the binarized information may be selected from a plurality of probability information tables.

The probability information table to be applied to the encoding of the binarized information may be selected according to whether the skip region is used to encode the current transform block.

An image decoding method or apparatus according to an embodiment of the present invention may decode positions of reference coefficients in a current transform block to be decoded, and decode skip region information on skip regions selected based on the positions of the reference coefficients. Can be.

An image decoding method or decoding apparatus according to another embodiment of the present invention obtains a value of an arithmetic-coded transform coefficient from a bitstream, and according to a position of the transform coefficient in a transform block, Probability information to be applied to the decoding can be determined.

Probability information to be applied to the decoding of the arithmetic coded transform coefficients may be determined according to which region the transform coefficient is located in a transform block divided into a plurality of regions.

An image decoding method or decoding apparatus according to another embodiment of the present invention decodes a position of a reference coefficient in a current transform block to be decoded, and decodes skip region information on a skipped region selected based on the position of the reference coefficient. In addition, an arithmetic encoded value of a transform coefficient not included in the skip region may be obtained, and a probability information table may be selected from among a plurality of probability information tables to be applied to decoding an arithmetic encoded value of the transform coefficient.

As the probability information table to be applied to the decoding of the arithmetic coded value of the transform coefficient, one of the plurality of probability information tables may be selected depending on whether the skip region is used to decode the current transform block.

According to an aspect of the present invention, a method of decoding an image includes decoding a position of a reference coefficient in a current transform block, deriving probability information of a coding parameter based on the position of the reference coefficient, and determining the derived probability information. And decoding the coding parameter by using the same.

In the decoding method of the image, the reference coefficient may be a first non-zero coefficient in an inverse scan order of coefficients in the current transform block.

In the decoding method of the image, the current transform block is divided into a first region and a second region, and the probability information of the coding parameter may be determined based on which region the reference coefficient exists.

According to an aspect of the present invention, there is provided a method of decoding an image, the method comprising: decoding partial information of a DC coefficient of a current transform block, deriving probability information of a coding parameter based on the partial information of the DC coefficient, and the derived probability And decoding the coding parameter using the information.

In the decoding method of the image, the DC coefficient may be a coefficient located at the upper left of the current transform block.

In the decoding method of the image, the partial information of the DC coefficient may be at least one piece of information for decoding the DC coefficient.

The decoding method of the image, the method further comprising: decoding a position of a reference coefficient in the current transform block, wherein the probability information of the coding parameter includes distance information between the DC coefficient and the reference coefficient and partial information of the DC coefficient. Can be derived based on.

According to an aspect of the present invention, there is provided a method of encoding an image, the method comprising: encoding positions of reference coefficients in a current transform block, deriving probability information of coding parameters based on positions of the reference coefficients, and using the derived probability information And encoding the coding parameter.

In the encoding method of the image, the reference coefficient may be a first non-zero coefficient in an inverse scan order of coefficients in the current transform block.

In the encoding method of the image, the current transform block is divided into a first region and a second region, and the probability information of the coding parameter may be determined based on which region the reference coefficient exists.

In the encoding method of the image, Encoding partial information of the DC coefficient of the current transform block, Deriving the probability information of the coding parameter based on the partial information of the DC coefficient and Using the derived probability information Encoding the coding parameter.

In the encoding method of the image, the DC coefficient may be a coefficient located at the upper left of the current transform block.

In the encoding method of the image, the partial information of the DC coefficient may be at least one piece of information for encoding the DC coefficient.

The coding method of the image, the method further comprising: encoding a position of a reference coefficient in the current transform block, wherein the probability information of the coding parameter includes distance information between the DC coefficient and the reference coefficient and partial information of the DC coefficient. Can be derived based on.

According to the present invention, the amount of encoded information generated as a result of encoding a video can be reduced, thereby improving the encoding efficiency.

In addition, arithmetic coding and arithmetic decoding performance can be improved by effectively selecting probability information applied to encoding or decoding each symbol during context-adaptive arithmetic coding and decoding.

The effects obtainable in the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

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

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

3 is a flowchart illustrating a method of encoding a transform block, according to an embodiment of the present invention.

4A to 4D are diagrams illustrating a diagonal reverse scan, a vertical reverse scan, and a horizontal reverse scan in sub-block units.

5 is a flowchart illustrating a method of decoding a transform block according to an embodiment of the present invention.

6 is a flowchart illustrating a video encoding method using a skip region according to an embodiment of the present invention.

7 is a diagram illustrating a skip region according to an embodiment of the present invention.

8 is a diagram illustrating a skip region according to another embodiment of the present invention.

9 is a diagram illustrating an additional skip area according to an embodiment of the present invention.

10 is a flowchart illustrating a method of encoding a transform block including a skip region or an additional skip region according to an embodiment of the present invention.

11 is a flowchart illustrating a method of decoding an image using a skip region according to an embodiment of the present invention.

12 is a flowchart illustrating a method of decoding a transform block including a skip region or an additional skip region according to an embodiment of the present invention.

13 is a flowchart illustrating a context-adaptive binarization arithmetic coding method according to an embodiment of the present invention.

14 is a flowchart illustrating a context-adaptive binarization arithmetic decoding method according to an embodiment of the present invention.

15A to 15C are diagrams illustrating an example in which probability information is differently applied according to information of neighboring coefficients.

16A to 16C illustrate various embodiments of dividing a transform block of a frequency domain into a plurality of regions.

17 is a flowchart illustrating an arithmetic coding method according to an embodiment of the present invention.

18 is a flowchart illustrating an arithmetic decoding method according to an embodiment of the present invention.

19A to 19C are diagrams for describing arithmetic encoding and arithmetic decoding according to another embodiment of the present invention.

20 is a flowchart illustrating an arithmetic coding method or a decoding method according to another embodiment of the present invention.

21 is a flowchart illustrating a context-adaptive binarization arithmetic coding method according to an embodiment of the present invention.

22 is a flowchart illustrating a context-adaptive binarization arithmetic decoding method according to an embodiment of the present invention.

23A and 24B illustrate an example in which probability information is differently applied according to information of neighboring coefficients.

24 is a flowchart illustrating a method of deriving probability information based on a reference coefficient according to an embodiment of the present invention.

25 is a diagram illustrating a reference counting position according to an embodiment of the present invention.

26A and 26B illustrate an example in which probability information is differently applied according to information of neighboring coefficients.

27 is a decoding flowchart illustrating a method of deriving probability information based on a reference coefficient according to an embodiment of the present invention.

28 is a flowchart illustrating a method of deriving probability information based on partial information of DC according to an embodiment of the present invention.

29 is a flowchart illustrating a method of encoding transform block coefficients using partial information of DC coefficients.

30 is a decoding flowchart illustrating a method of deriving probability information based on partial information of a DC according to an embodiment of the present invention.

31 is a flowchart illustrating a method of decoding transform block coefficients using partial information of DC coefficients.

32 is a flowchart illustrating a method of deriving probability information based on a distance between a DC coefficient and a reference coefficient and partial information of the DC coefficient.

33 is a diagram illustrating an example in which probability information is differently applied according to information of peripheral coefficients.

34 is a decoding flowchart illustrating a method of deriving probability information based on a distance between a DC coefficient and a reference coefficient and partial information of the DC coefficient.

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. In describing the drawings, similar reference numerals are used for similar elements.

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 a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. 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 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 this application, 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.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

Referring to FIG. 1, the image encoding apparatus 100 may include an image splitter 101, an intra picture predictor 102, an inter picture predictor 103, a subtractor 104, a transformer 105, and a quantizer. 106, an entropy encoding unit 107, an inverse quantization unit 108, an inverse transform unit 109, an increase unit 110, a filter unit 111, and a memory 112.

Each of the components shown in FIG. 1 is independently illustrated to represent different characteristic functions in the image encoding apparatus, and does not mean that each of the components 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.

In addition, some of the components may not be 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.

The image divider 100 may divide the input image into at least one block. In this case, the input image may have various shapes and sizes, such as a picture, a slice, a tile, and a segment. A block may mean a coding unit (CU), a prediction unit (PU), or a transformation unit (TU). The partitioning may be performed based on at least one of a quadtree or a binary tree. Quad tree is a method of dividing an upper block into lower blocks having a width and a height of half of the upper block. The binary tree divides the upper block into lower blocks, which are half of the upper block in either width or height. Through the above-described binary tree-based partitioning, a block may have a square as well as a non-square shape.

The

predictors

102 and 103 may include an inter prediction unit 103 that performs inter prediction and an intra prediction unit 102 that performs intra prediction. Whether to use inter prediction or intra prediction on the prediction unit may be determined, and specific information (eg, an intra prediction mode, a motion vector, a reference picture, etc.) according to each prediction method may be determined. In this case, the processing unit in which the prediction is performed may differ from the processing unit in which the prediction method and the details are determined. For example, the method of prediction and the prediction mode may be determined in the prediction unit, and the prediction may be performed in the transform unit.

The residual value (residual block) between the generated prediction block and the original block may be input to the transformer 105. In addition, prediction mode information and motion vector information used for prediction may be encoded by the entropy encoder 107 together with the residual value and transmitted to the decoder. When a specific encoding mode is used, the original block may be encoded as it is and transmitted to the decoder without generating the prediction block through the

prediction units

102 and 103.

The intra prediction unit 102 may generate a prediction block based on reference pixel information around the current block, which is pixel information in the current picture. When the prediction mode of the neighboring block of the current block on which intra prediction is to be performed is inter prediction, a reference pixel included in the neighboring block to which inter prediction is applied may be replaced with a reference pixel in another block around to which intra prediction is applied. That is, when the reference pixel is not available, the unavailable reference pixel information may be replaced with at least one reference pixel among the available reference pixels.

In intra prediction, a prediction mode may have a directional prediction mode using reference pixel information according to a prediction direction, and a non-directional mode using no directional information when performing prediction. The mode for predicting the luminance information and the mode for predicting the color difference information may be different, and the intra prediction mode information or the predicted luminance signal information used for predicting the luminance information may be utilized to predict the color difference information.

The intra prediction unit 102 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a filter that filters the reference pixels of the current block and may adaptively determine whether to apply the filter according to the prediction mode of the current prediction unit. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

The reference pixel interpolation unit of the intra prediction unit 102 interpolates the reference pixel when the intra prediction mode of the prediction unit performs the intra prediction based on the pixel value interpolated with the reference pixel. Can be generated. If the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate the prediction block through filtering when the prediction mode of the current block is the DC mode.

The inter prediction unit 103 generates a prediction block by using the reconstructed reference image and motion information stored in the memory 112. The motion information may include, for example, a motion vector, a reference picture index, a list 1 prediction flag, a list 0 prediction flag, and the like.

A residual block including residual information, which is a difference between the prediction unit generated by the

prediction units

102 and 103 and the original block of the prediction unit, may be generated. The generated residual block may be input to the converter 130 and converted.

The inter prediction unit 103 may induce a prediction block based on information of at least one of a previous picture or a subsequent picture of the current picture. In addition, a prediction block of the current block may be derived based on information of a partial region in which encoding in the current picture is completed. The inter prediction unit 103 according to an embodiment of the present invention may include a reference picture interpolator, a motion predictor, and a motion compensator.

The reference picture interpolation unit may receive reference picture information from the memory 112 and generate pixel information of less than an integer pixel in the reference picture. In the case of luminance pixels, a DCT based 8-tap interpolation filter having different filter coefficients may be used to generate pixel information of integer pixels or less in units of 1/4 pixels. In the case of a chrominance signal, a DCT-based interpolation filter having different filter coefficients may be used to generate pixel information of an integer pixel or less in units of 1/8 pixels.

The motion predictor may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating a motion vector, various methods such as full search-based block matching algorithm (FBMA), three step search (TSS), and new three-step search algorithm (NTS) may be used. The motion vector may have a motion vector value of 1/2 or 1/4 pixel units based on the interpolated pixels. The motion prediction unit may predict the prediction block of the current block by using a different motion prediction method. As the motion prediction method, various methods such as a skip method, a merge method, and an advanced motion vector prediction (AMVP) method may be used.

The subtraction unit 104 generates a residual block of the current block by subtracting the block to be currently encoded from the prediction block generated by the intra prediction unit 102 or the inter prediction unit 103.

The transform unit 105 may transform the residual block including the residual data by using a transformation method such as DCT, DST, or Karhunen Loeve Transform (KLT). In this case, the transformation method may be determined based on the intra prediction mode of the prediction unit used to generate the residual block. For example, depending on the intra prediction mode, DCT may be used in the horizontal direction and DST may be used in the vertical direction.

The quantization unit 106 may quantize the values converted in the frequency domain by the transformer 105. The quantization coefficient may change depending on the block or the importance of the image. The value calculated by the quantization unit 106 may be provided to the inverse quantization unit 108 and the entropy encoding unit 107.

The transform unit 105 and / or the quantization unit 106 may be selectively included in the image encoding apparatus 100. That is, the image encoding apparatus 100 may encode the residual block by performing at least one of transform or quantization on the residual data of the residual block, or skipping both transform and quantization. Even if neither the transformation nor the quantization is performed or neither the transformation nor the quantization is performed in the image encoding apparatus 100, a block entering the input of the entropy encoder 107 is generally referred to as a transform block. The entropy encoder 107 entropy encodes the input data. Entropy encoding may use various encoding methods such as, for example, Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC).

The entropy encoder 107 may be configured to perform various operations such as coefficient information, block type information, prediction mode information, split unit information, prediction unit information, transmission unit information, motion vector information, reference frame information, interpolation information of a transform block, filtering information, and the like. Information can be encoded. The coefficients of the transform block may be encoded in units of sub blocks within the transform block.

Last_sig, a syntax element that indicates the position of the first non-zero coefficient in reverse scan order, for encoding the coefficients of the transform block, Coded_sub_blk_flag, which is a flag indicating whether there is at least one non-zero coefficient in the subblock, Sig_coeff_flag, a flag that indicates whether the coefficient is non-zero, Abs_greater1_flag, which indicates whether the absolute value of the coefficient is greater than 1, Abs_greater2_flag, which indicates whether the absolute value of the coefficient is greater than 2, Sign_flag, which indicates the sign of the coefficient, etc. Syntax elements may be encoded. Residual values of coefficients not encoded with only the syntax elements may be encoded through the syntax element remaining_coeff.

The inverse quantization unit 108 and the inverse transformer 109 inverse quantize the quantized values in the quantization unit 106 and inverse transform the transformed values in the transformer 105. The residual values generated by the inverse quantizer 108 and the inverse transformer 109 are predicted by the motion estimator, the motion compensator, and the intra prediction unit 102 included in the

predictors

102 and 103. It may be combined with the prediction unit to generate a reconstructed block. The transcriptor 110 generates a reconstructed block by multiplying the prediction blocks generated by the

predictors

102 and 103 and the residual blocks generated by the inverse transform unit 109.

The filter unit 111 may include at least one of a deblocking filter, an offset correction unit, and an adaptive loop filter (ALF).

The deblocking filter may remove block distortion caused by boundaries between blocks in the reconstructed picture. In order to determine whether to perform deblocking, it may be determined whether to apply a deblocking filter to the current block based on the pixels included in 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 offset correction unit may correct the offset with respect to the original image on a pixel-by-pixel basis for the deblocking image. In order to perform offset correction for a specific picture, the pixels included in the image are divided into a predetermined number of areas, and then, an area to be offset is determined, an offset is applied to the corresponding area, or offset considering the edge information of each pixel. You can use this method.

Adaptive Loop Filtering (ALF) may be performed based on a value obtained by comparing the filtered reconstructed image with 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 ALF, a luminance signal may be transmitted for each coding unit (CU), and the shape and filter coefficient of an ALF filter to be applied may vary according to each block. In addition, regardless of the characteristics of the block to be applied, the same type (fixed form) of the ALF filter may be applied.

The memory 112 may store a reconstructed block or picture calculated by the filter unit 111, and the stored reconstructed block or picture may be provided to the

predictors

102 and 103 when performing inter prediction.

Next, an image decoding apparatus according to an embodiment of the present invention will be described with reference to the drawings. 2 is a block diagram illustrating an image decoding apparatus 200 according to an embodiment of the present invention.

Referring to FIG. 2, the image decoding apparatus 200 may include an entropy decoder 201, an inverse quantizer 202, an inverse transform unit 203, an increase unit 204, a filter unit 205, a memory 206, and the like. The

prediction unit

207 and 208 may be included.

When the image bitstream generated by the image encoding apparatus 100 is input to the image decoding apparatus 200, the input bitstream may be decoded according to a process opposite to that performed by the image encoding apparatus 100. .

The entropy decoding unit 201 may perform entropy decoding in a procedure opposite to that of the entropy encoding unit 107 of the image encoding apparatus 100. For example, various methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be applied to the method performed by the image encoder. The entropy decoding unit 201 may decode the syntax elements described above, that is, Last_sig, Coded_sub_blk_flag, Sig_coeff_flag, Abs_greater1_flag, Abs_greater2_flag, Sign_flag, and remaining_coeff. Also, the entropy decoder 201 may decode information related to intra prediction and inter prediction performed by the image encoding apparatus 100.

The inverse quantizer 202 generates a transform block by performing inverse quantization on the quantized transform block. It operates substantially the same as the inverse quantizer 108 of FIG.

The inverse transform unit 203 performs an inverse transform on the transform block to generate a residual block. In this case, the transformation method may be determined based on information on a prediction method (inter or intra prediction), a size and / or shape of a block, an intra prediction mode, and the like. It operates substantially the same as the inverse transform unit 109 of FIG.

The increaser 204 generates a reconstructed block by multiplying the prediction block generated by the intra prediction unit 207 or the inter prediction unit 208 and the residual block generated by the inverse transform unit 203. It operates substantially the same as the transpiration section 110 of FIG.

The filter unit 205 reduces various kinds of noise generated in the restored blocks.

The filter unit 205 may include a deblocking filter, an offset corrector, and an ALF.

When the deblocking filter is applied and information about whether the deblocking filter is applied to the corresponding block or picture, the image encoding apparatus 100 may receive information about whether a strong filter or a weak filter is applied. In the deblocking filter of the image decoding apparatus 200, the deblocking filter related information provided by the image encoding apparatus 100 may be provided, and the image decoding apparatus 200 may perform deblocking filtering on the corresponding block.

The offset correction unit may perform offset correction on the reconstructed image based on the type of offset correction and offset value information applied to the image during encoding.

The ALF may be applied to a coding unit based on ALF application information, ALF coefficient information, and the like provided from the image encoding apparatus 100. Such ALF information may be provided included in a specific parameter set. The filter unit 205 operates substantially the same as the filter unit 111 of FIG. 1.

The memory 206 stores the reconstruction block generated by the multiplier 204. It operates substantially the same as the memory 112 of FIG.

The

prediction units

207 and 208 may generate the prediction blocks based on the prediction block generation related information provided by the entropy decoding unit 201 and previously decoded blocks or picture information provided by the memory 206.

The

prediction units

207 and 208 may include an intra prediction unit 207 and an inter prediction unit 208. Although not separately illustrated, the

prediction units

207 and 208 may further include a prediction unit determination unit. The prediction unit determination unit receives various information such as prediction unit information input from the entropy decoder 201, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, and distinguishes the prediction unit from the current coding unit, and predicts It may be determined whether the unit performs inter prediction or intra prediction. The inter prediction unit 208 may include information included in at least one of a previous picture or a subsequent picture of the current picture including the current prediction unit by using information necessary for inter prediction of the current prediction unit provided by the image encoding apparatus 100. Based on the prediction, the inter prediction may be performed on the current prediction unit. Alternatively, inter-screen prediction may be performed based on information of a pre-restored partial region in the current picture including the current prediction unit.

Whether the motion prediction method of the prediction unit included in the coding unit based on the coding unit to perform inter prediction is skip mode, merge mode, or AMVP mode. Can be determined.

The intra prediction unit 207 generates a prediction block using pixels that are located around the block to be currently encoded and are reconstructed.

The intra prediction unit 207 may include an adaptive intra smoothing (AIS) filter, a reference pixel interpolator, and a DC filter. The AIS filter is a filter that filters the reference pixels of the current block and may adaptively determine whether to apply the filter according to the prediction mode of the current prediction unit. The AIS filtering may be performed on the reference pixel of the current block by using the prediction mode of the prediction unit and the AIS filter information provided by the image encoding apparatus 100. If the prediction mode of the current block is a mode that does not perform AIS filtering, the AIS filter may not be applied.

The reference pixel interpolation unit of the intra prediction unit 207 interpolates a reference pixel at a fractional position by interpolating the reference pixel when the prediction mode of the prediction unit is a prediction unit that performs intra prediction based on a pixel value interpolating the reference pixel. Can be generated. The generated reference pixel at the fractional unit location may be used as the prediction pixel of the pixel in the current block. If the prediction mode of the current prediction unit is a prediction mode for generating a prediction block without interpolating the reference pixel, the reference pixel may not be interpolated. The DC filter may generate the prediction block through filtering when the prediction mode of the current block is the DC mode.

The intra prediction unit 207 operates substantially the same as the intra prediction unit 102 of FIG. 1.

The inter prediction unit 208 generates an inter prediction block using the reference picture and the motion information stored in the memory 206. The inter prediction unit 208 operates substantially the same as the inter prediction unit 103 of FIG. 1.

Hereinafter, various embodiments of the present invention will be described in more detail with reference to the drawings.

(First embodiment)

3 is a flowchart illustrating a method of encoding a transform block, according to an embodiment of the present invention. The encoding method of the transform block of FIG. 3 may be performed by the entropy encoder 107 of the image encoding apparatus 100.

As shown in FIG. 4A, one transform block may be encoded in sub-block units. Referring to FIG. 4A, when the current transform block 400 to be encoded or decoded is an 8 × 8 block, the current transform block 400 may be divided into four subblocks 1 401 to 4 block 404 having a size of 4 × 4. As a scan method for determining an encoding order of transform coefficients in a transform block, an inverse scan method in a vertical, horizontal, or diagonal direction may be used according to a prediction mode of the current block or the current transform block. Here, the prediction mode may be inter prediction or intra prediction.

4B, 4C and 4D show a diagonal reverse scan, a vertical reverse scan and a horizontal reverse scan, respectively. Here, for convenience of explanation, a diagonal reverse scan is described as an example, but both a vertical reverse scan or a horizontal reverse scan may be applied.

Referring to FIG. 3, first, non-zero coefficients are determined as reference coefficients when scanning transform coefficients according to an inverse scan order, and the position information Last_sig is encoded (S301).

The sub block including the reference coefficient is selected (S302) and the corresponding sub block information is encoded (S303). Coded_sub_blk_flag, which is sub block information, is a flag indicating whether there is at least one non-zero coefficient in the current sub block. Thereafter, non-zero coefficient information is encoded (S304). Here, Sig_coeff_flag, which is nonzero coefficient information, indicates whether or not the value of each coefficient existing in the subblock is zero.

Then, N excess coefficient information is encoded (S305). Here, the N excess coefficient information indicates whether the absolute value of each coefficient exceeds a value from 1 to N for all coefficients existing in the subblock. N uses arbitrary preset values for encoding and decoding, but may encode the value of N to use the same value for encoding and decoding. The number of N excess coefficient information may use any predetermined value or may be used differently according to the position of the reference coefficient. For example, when N is set to 3, for all coefficients determined to be non-zero in the subblock, whether or not the absolute value of each coefficient is greater than 1 is encoded. To this end, Abs_greater1_flag, a flag indicating whether the absolute value of the coefficient is greater than one, is used. Thereafter, only the coefficients judged to be larger than 1 are encoded. For this purpose, Abs_greater2_flag, which is a flag indicating whether the absolute value of the coefficient is greater than 2, is used. Finally, only the coefficients judged to be greater than 2 are encoded. To this end, Abs_greater3_flag, a flag indicating whether the absolute value of the coefficient is greater than 3, may be used.

Thereafter, code information indicating whether the coefficient is negative or positive is encoded for each coefficient judged not to be zero (S306). Sign_flag may be used as the sign information. Only remaining coefficients obtained by subtracting N are defined as residual coefficient information only for coefficients determined to be larger than N, and residual value information remaining_coeff of the coefficients is encoded (S307).

After that, it is checked whether the next subblock exists (S309), and if so, it moves to the next subblock (S310) and the subblock information is encoded (S303). The subblock information Coded_sub_blk_flag is checked (S308). If it is determined that the value of Coded_sub_blk_flag is true, Sig_coeff_flag, which is non-zero coefficient information, is encoded. If the value of the corresponding subblock information Coded_sub_blk_flag is false, it means that there is no coefficient to be encoded in the corresponding subblock. Therefore, the existence of the next subblock is checked. Alternatively, after moving to the next subblock, if the subblock is a subblock located at the lowest frequency side, it is set to the same value at the time of encoding and decoding as true without encoding and decoding subblock information under the assumption that there is a non-zero coefficient. It is also possible.

5 is a flowchart illustrating a method of decoding a transform block according to an embodiment of the present invention. The decoding method of the transform block of FIG. 5 corresponds to the encoding method of the transform block of FIG. 3. The decoding method of the transform block of FIG. 5 may be performed by the entropy decoding unit 201 of the image decoding apparatus 200.

The positional information Last_sig of the reference coefficient, which is a non-zero transform coefficient, is first decoded according to the inverse scan order (S501).

The sub block including the reference coefficient is selected (S502) and the sub block information Coded_sub_blk_flag is decoded (S503). Thereafter, non-zero coefficient information Sig_coeff_flag is decoded (S504). The N excess coefficient information is then decoded (S505). Here, the N excess coefficient information may include Abs_greater1_flag, Abs_greater2_flag, Abs_greater3_flag, and the like as described above.

Thereafter, the sign information Sign_flag of the coefficient is decoded for each coefficient determined to be non-zero (S506). Residual coefficient information remaing_coeff corresponding to the remaining value after subtracting N is only decoded for the coefficient determined to be greater than N (S507). After that, it is checked whether the next subblock exists (S509), and if so, it moves to the next subblock (S510), and the subblock information Coded_sub_blk_flag is decoded (S503). If the subblock information Coded_sub_blk_flag is checked (S508), and it is determined to be true, the non-zero coefficient information Sig_coeff_flag is decoded. do.

6 is a flowchart illustrating a video encoding method using a skip region according to an embodiment of the present invention. The image encoding method of FIG. 6 may be performed by the entropy encoding unit 107 of the image encoding apparatus 100.

Referring to FIG. 6, first, the entropy encoder 107 encodes a position of a reference coefficient in a current transform block to be encoded (S601). As mentioned above, the reference coefficient refers to the first non-zero coefficient when scanning the coefficients in reverse scan order. Thereafter, skip region information on the selected skip region is encoded based on the position of the reference coefficient (S602).

Here, the skip region is an area in the current transform block, which can be determined based on the position of the reference coefficient. The skip region information indicates whether all coefficients in the skip region have the same value. Here, the same value of the coefficients in the skipped region may be zero. If the same value of the coefficients in the skipped region is not 0, information indicating which value is not 0 may be further encoded. It is also possible to use any non-zero predetermined value as the same value of the coefficients in the skip region. In this case, it is possible to encode information of a predetermined value through an upper header rather than a transform block unit.

In the meantime, the skip region may be determined in the encoding / decoding process according to a predetermined rule, and the encoding apparatus 100 or the decoding apparatus 200 may further encode a coordinate indicating the range of the skip region in the transform block. The same location may be used.

7 is a diagram illustrating a skip region according to an embodiment of the present invention. Assume that a diagonal inverse scan is used for coefficient coding of the current transform block 700.

Referring to FIG. 7, after generating the reference line 702 in the lower left 45 degree direction based on the position of the reference coefficient 701, the coefficients positioned on the reference line 702 and the reference line 702 are present below the reference line 702. An area containing the coefficients to be specified is designated as a skip area. In FIG. 7, the skipped region is shaded, and all coefficients in the skipped region have the same value of zero. In addition, all the coefficients in the skipped region are located later in the coding order than the reference coefficients.

As another embodiment of setting the skip region, if the number of coefficients present in the skip region is small because the reference coefficient is located in any arbitrary region in the transform block, the reverse scan order is not determined based on the reference coefficient. The skip region may be set using one of non-zero coefficients after the phase reference coefficient or a coefficient adjacent to the reference coefficient. Here, the arbitrary area in the transform block in which the reference coefficient is located can be set by comparing the number of sub-blocks calculated in the reverse scan order with a preset threshold. Alternatively, the reference coefficient may be set to determine how far from any arbitrary position of the transform block to compare with a preset threshold. For example, this arbitrary position may be a center point that is halfway between the transverse and vertical sides of the transform block. Alternatively, it is also possible to divide the width and length of the transform block by m and n, respectively, and determine one of these divided regions as an arbitrary region. In this case, the values of m and n may be encoded through block units or higher headers, and the same preset values may be used for encoding and decoding.

8 is a diagram illustrating a skip region according to another embodiment of the present invention. The coefficient located on the reference line 803 after generating the reference line 803 from the position of the reference coefficient 801 in the transform block 800 to the position of the coefficient 802 present in the lower left corner in the transform block 800. And a coefficient including the coefficients existing at the bottom of the reference line 803 are designated as a skip region. Here, the coefficients belonging to the skipped region are located later in the coding order than the reference coefficients. In FIG. 8, the skip region is indicated by the shade.

Although not shown in FIG. 6, a skip region may be additionally set in addition to the skip region set by steps S601 and S603. The skip region additionally set may be encoded using additional skip region information.

9 is a diagram illustrating an additional skip area according to an embodiment of the present invention. An additional skip region is set in FIG. 9 in addition to the skip region illustrated in FIG. 7. An area above the skip area of FIG. 7 is set as an additional skip area, and additional skip area information indicating whether coefficients in the additional skip area are all the same value may be encoded. Here, the same value of the coefficients in the skipped region may be zero. If the same value of the coefficients in the skipped region is not 0, information indicating which value is not 0 may be further encoded. It is also possible to use any preset value other than zero as the same value of the coefficients in the skip region. In this case, it is possible to encode information of a predetermined value through an upper header rather than a transform block unit.

Meanwhile, the location of the additional skip region may be determined in the encoding and decoding process according to a predetermined rule, or the same position may be used in the encoding apparatus 100 and the decoding apparatus 200 by further encoding the coordinates in the transform block. have. In this case, the newly generated additional skip region may be separated by a distance p from the previous skip region.

Referring to FIG. 9, a skip region is set by generating a reference line 702 based on the reference coefficient 701, and an example in which an upper portion of the reference line 702 is additionally set as a skip region. When the distance p between the additional skip area and the skip area is 0, an area including coefficients on the reference line 703 may be an additional skip area. If the distance p is 1, the additional skip region includes an area that includes the coefficients on the baseline 703 and an area that includes the coefficients on the baseline 704.

In this embodiment, the distance p between the additional skip region and the skip region is 0 or 1, but other values may be used. Here, p may use the same preset value in the encoding / decoding process. Alternatively, the value of p may be encoded in a block unit or may be encoded through an upper header.

In addition, the additional skip region may be added by a preset method. For example, it is also possible to continue adding additional skip regions or to encode a predetermined number q until the additional skip region information is false. Here, it is possible to set a different p for each additional skip region added.

10 is a flowchart illustrating a method of encoding a transform block including a skip region or an additional skip region according to an embodiment of the present invention. The method shown in FIG. 10 may be performed after the method shown in FIG. 6. The encoding method of FIG. 10 may be performed by the entropy encoding unit 107 of the image encoding apparatus 100.

If a reference coefficient is included in a subblock in a current transform block to be encoded, it means that a coefficient to be encoded is included and thus coded_sub_blk_flag, which is subblock information, is not encoded. It is checked whether the skip region information or the additional skip region information is true, and at the same time, whether the subblock to be currently encoded includes the skip region or the additional skip region (S1001). If the above two conditions are true, coefficients located in the current subblock and located outside the skip region in the encoding order are selected (S1002). If not, all coefficients to be coded are selected regardless of the skip region (S1003). Thereafter, the coefficients are encoded in the order of nonzero coefficient information encoding (S1004), N excess coefficient information encoding (S1005), code information encoding (S1006), and residual coefficient information encoding (S1007).

Thereafter, when the next subblock exists (S1008), the control moves to the next subblock (S1009). It is checked whether the skip region information or the additional skip region information is true, and at the same time, whether the subblock to be currently encoded includes the skip region or the additional skip region (S1010). Go to. However, this case can be used only when the values of the coefficients in the skipped region are zero. If the values of the coefficients in the skipped region are not 0, the corresponding subblock information should be encoded.

If the subblock does not include the skip region or the additional skip region, or if the skip region information is false (S1011), if the sub block information is true (S1012), the process moves to step S1001, and if it is false, Move to S1008. If it is determined after the move to step S1008 that the next subblock does not exist, the algorithm of FIG. 10 ends.

Hereinafter, the algorithm shown in FIGS. 6 and 10 will be further described using the example of FIG. 7. In the current transform block, the scan method assumes a diagonal reverse scan order, and sets the first nonzero coefficient as a reference coefficient. After setting the coefficients in the lower left direction and the coefficients below the reference region to the skip region based on the reference coefficients, the values of the skip regions are all checked. Since the coefficients of the skipped region all have the same value as 0, the skipped region information is encoded as true. After dividing by the sub-block unit, the sub block including the reference coefficient is encoded.

For example, the current transform block is 8x8 and the subblock is 4x4. Firstly, skip region information of a subblock to be encoded is true, and there are coefficients to be encoded in the subblock. Since only coefficients outside the skipped region are encoded, in the example shown in FIG. 7, only the reference coefficient and 1, 0, 0, -2 existing thereon need to be encoded. In this case, the nonzero coefficient information becomes true, false, false, and true, respectively. Assuming that N is 2, only one information is encoded in only coefficients determined to be non-zero. More than one information of the coefficient values 1 and -2 is set to false and true, respectively. More than 2 information is encoded only if the more than 1 information is true, and more than 2 information of the coefficient value -2 is encoded as false. Thereafter, + and-which are signs of coefficient values 1 and -2 are encoded, respectively. Thereafter, since the next subblock exists, it moves to the next subblock.

For the second subblock to be encoded, the skip region information is true, and since the coefficient to be encoded exists in the corresponding subblock, the subblock information is true. Therefore, only

coefficients

0, 0, and 1 outside the skipped region are encoded. The non-zero coefficient information of the

coefficients

0, 0, and 1 is false, false, and true, respectively, and then only one piece of information of coefficient 1 is falsely encoded. The sign information of the coefficient 1 is encoded by + and moves to the next subblock.

In the third subblock to be encoded, the subblock information is true because the skip region information is true and there are coefficients to be encoded in the corresponding subblock. Sorting the coefficients outside the skip region by reverse scan results in 0, 0, 0, 0, 0, 1, 1, 1, 1, -2, -2, 1, -3, 3, 10. These coefficients are encoded using steps S1004 to S1007.

11 is a flowchart illustrating a method of decoding an image using a skip region according to an embodiment of the present invention. The decoding method of FIG. 11 may be performed by the entropy encoder 201 of the image decoding apparatus 100.

Referring to FIG. 11, first, the entropy decoding unit 201 decodes a position of a reference coefficient in a current transform block to be decoded (S1101). Thereafter, the skip region information for the selected skip region is decoded based on the position of the reference coefficient (S1103). As described above, the position of the reference coefficient can be derived by decoding Last_sig. Since the skip region and the skip region information are the same as described above, a detailed description thereof will be omitted. In addition, although not separately illustrated in FIG. 11, if there is an additional skip region additionally set in addition to the skip region, the additional skip region may be decoded using additional skip region information.

12 is a flowchart illustrating a method of decoding a transform block including a skip region or an additional skip region according to an embodiment of the present invention. The method shown in FIG. 12 may be performed after the method shown in FIG. The decoding method of FIG. 12 may be performed by the entropy decoding unit 201 of the image decoding apparatus 200.

Since the method shown in FIG. 12 is substantially the same as the method shown in FIG. 10, a detailed description thereof will be omitted. In FIG. 10, skip region information, additional skip region information, sub block information Coded_sub_blk_flag, nonzero coefficient information, N excess coefficient information, code information, residual coefficient information, and the like are encoded, but in FIG. 12, these information are decoded. There is a difference in points.

The algorithms shown in FIGS. 11 and 12 are further described using the example of FIG. 7. After decoding the position information Last_sig of the reference coefficient in the current transform block, the reference coefficient is set. The skip area is set based on the position of the reference coefficient, and the skip area information is decoded. In this example, the skip region information is true. After dividing the transform block into subblock units, the first block is decoded from the subblock including the reference coefficient.

For example, the current transform block is 8x8 and the subblock is 4x4. For the first subblock to be decoded, the skip region information is true, and there are coefficients to be decoded in the corresponding subblock. Since only coefficients outside the skipped region are decoded, only the reference coefficient and 1, 0, 0, and -2 present in the case illustrated in FIG. 7 need to be decoded. In this case, the decoded values of the nonzero coefficient information become true, false, false, and true, respectively. Assuming that N is 2, only one piece of information is decoded only in coefficients determined to be non-zero. More than one information of the coefficient values 1 and -2 is decoded as false and true, respectively. More than 2 information is decoded only if the more than 1 information is true, and more than 2 information of the coefficient value -2 is decoded false. Thereafter, + and-which are the signs of the coefficient values 1 and -2 are respectively decoded. Thereafter, since the next subblock exists, it moves to the next subblock.

In the second subblock to be decoded, the skip region information is true, and since the coefficient to be decoded exists in the corresponding subblock, the subblock information is true. Therefore, only 0, 0, and 1 coefficients outside the skip region are decoded. The non-zero coefficient information of the

coefficients

0, 0, and 1 is decoded false, false, and true, respectively, and then only one time information of coefficient 1 is decoded false. The sign information of the coefficient 1 is decoded to + and moved to the next subblock.

Thirdly, in case of a subblock to be decoded, since the skip area information is true and a coefficient to be decoded exists in the corresponding subblock, the subblock information is true. Sorting the coefficients outside the skip region by reverse scan results in 0, 0, 0, 0, 0, 1, 1, 1, 1, -2, -2, 1, -3, 3, 10. These coefficients are decoded using steps S1204 to S1207.

(2nd Example)

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

The encoded information is subjected to context-adaptive binarization arithmetic through a binarization process. Context-adaptive binarization arithmetic refers to a process of symbolizing encoded information in a block and applying and encoding the occurrence probability of symbols differently using probability information according to a situation. In the present embodiment, only 0 and 1 symbols are used for convenience of description, but N symbols (N is a natural number of 2 or more) may be used.

Probability information refers to the probability of occurrence of 0 and 1 in the binarized information. The occurrence probability of the two pieces of information may be the same or different depending on the previously restored information. It may have N probability information according to the information.

13 is a flowchart illustrating a context-adaptive binarization arithmetic coding method according to an embodiment of the present invention. First, probability initialization is performed (S1301). Probability initialization is a process of dividing the probability section by the probability set in the probability information. However, as to what kind of probability information is to be used, the same condition may be used by a predetermined rule in the encoding apparatus or the decoding apparatus, or the probability information may be separately encoded. The initial probability interval may be determined in the same manner in the encoding / decoding process according to a preset rule. Alternatively, the initial probability interval may be newly encoded.

When the binary information of the current coding parameter to be encoded is determined (S1302), the binarized information of the current coding parameter is encoded using the probability interval state up to the step before the step S1302 and the previous probability information of the same coding parameter (S1303). After the probability information and the probability interval are updated (S1304) for the binary information to be encoded later (S1305), if the coding parameter information to be encoded next (S1305) moves to the next coding parameter information (S1306), the above-described process is performed. Repeat. If there is no coding parameter information to be encoded next, the flowchart ends.

14 is a flowchart illustrating a context-adaptive binarization arithmetic decoding method according to an embodiment of the present invention. Unlike the encoding apparatus, the decoding apparatus decodes binary information of a coding parameter using probability information and an interval (S1402), and then determines binary information of a current coding parameter (S1403). In addition, since the decoding method of FIG. 14 corresponds to the encoding method of FIG. 13, detailed description thereof will be omitted.

In steps S1303 and S1402 of FIGS. 13 and 14 described above, encoding or decoding may be performed by selectively using optimal probability information among N pieces of probability information preset by using information reconstructed around each coding parameter. . For example, the probability information of the information belonging to the quantized transform block may use probability information having a high probability of generating information according to the size of the transform block.

Alternatively, the probability information may be differently applied according to the information of the neighboring coefficients of the coefficient to be currently encoded or decoded, and the probability information of the information currently encoded or decoded may be selected using the probability information of the previously encoded or decoded information. .

15A to 15C are diagrams illustrating an example in which probability information is differently applied according to information of neighboring coefficients. 15B is an example of a probability information table used for encoding or decoding a Sig_coeff_flag information value of a current coefficient. Referring to FIG. 15B, when the number of coefficients having the same information value as the Sig_coeff_flag information value 1 of the current coefficient 1501 among the coefficients 1501 adjacent to the current encoding or decoding information is 1, an index is included in the current coefficient 1501. 8 is allocated. At this time, the probability of symbol 1, which is the Sig_coeff_flag binary information of the current coefficient 1501, is 61%, and the probability of symbol 0 is 39%. If the number of neighboring coefficients having the same information value as the Sig_coeff_flag information value of the current coefficient 1501 is two, the index is assigned to the current coefficient 1501, and the symbol that is the Sig_coeff_flag binary information of the current coefficient 1501 at this time. The probability of 1 is 71% and the probability of symbol 0 is 29%. If the number of neighboring coefficients having the same information value as the Sig_coeff_flag information value of the current coefficient 1501 is three, the index is assigned to the current coefficient 1501 and the probability of symbol 1, which is the Sig_coeff_flag binary information of the current coefficient 1501, is 87. The probability of% and symbol 0 is 13%. After the current coefficient 1501 is encoded or decoded using the probability information table illustrated in FIG. 15B, the probability information may be updated as shown in FIG. 15C.

On the other hand, in the case of non-zero coefficient information Sig_coeff_flag, probability information having a higher probability of generating non-zero coefficient information may be used closer to the low frequency region. For the probability information of the N excess coefficient information, the probability information of the current N excess coefficient information is set by using the probability information of the N excess coefficient information previously encoded / decoded, or the N excess coefficient information first encoded / decoded in units of sub blocks. Can be used as is. The subblock information may use neighboring coded / decoded M subblock probability information or use probability information of the immediately encoded / decoded subblock.

16A to 16C illustrate various embodiments of dividing a transform block of a frequency domain into a plurality of regions. Referring to FIGS. 16A through 16C, a transform block may be divided into three regions, a

frequency A region

1601, 1604, and 1607, a

frequency B region

1602, 1605, and 1608, and a

frequency C region

1603, 1606, and 1609. have. Each region may be adaptively determined according to the scan direction of the transform block. FIG. 16A illustrates a diagonal direction, FIG. 16B illustrates a scan direction in a horizontal direction, and FIG. 16C illustrates a scan direction in a vertical direction. This is an example of a frequency domain classification method when. The

frequency A regions

1601, 1604, and 1607 are low frequency regions with the highest probability of generating coefficient coefficient information other than zero, and the

frequency B regions

1602, 1605, and 1608 have zero values than the

A regions

1601, 1604, and 1607. Less non-coefficient information occurs, and the

frequency C regions

1603, 1606, and 1609 are high frequency regions, and the non-zero coefficient information is less than that of the

A regions

1601, 1604, and 1607, and the

B regions

1602, 1605, and 1608. Probability information may be set differently for each region by using the generated region. The

frequency A regions

1601, 1604, 1607, the

frequency B regions

1602, 1605, and 1608 and the

frequency C regions

1603, 1606, and 1609 are divided according to the distance from the DC coefficient located in the upper left corner of the transform block. You can see.

Referring again to the probability information table of FIG. 15B, when the current coefficient to be encoded or decoded belongs to the area A (1601, 1604, 1607), the current coefficient is assigned an index 8, the probability of symbol 1 is 61%, and the symbol 0 is The probability is 39%. If the current coefficient belongs to the

B regions

1602, 1605, and 1608, an index 5 is assigned to the current coefficient, the probability of symbol 1 is 71%, and the probability of symbol 0 is 29%. If the current coefficient belongs to the

C regions

1603, 1606, and 1609, index 2 is assigned to the current coefficient, the probability of symbol 1 is 87%, and the probability of symbol 0 is 13%. After the current coefficient is encoded or decoded using the probability information table illustrated in FIG. 15B, the probability information may be updated as shown in FIG. 15C.

Probability information of non-zero coefficient information, N excess coefficient information, and sub-block information may use probability information having a higher probability of occurrence as the region A (1601, 1604, 1607) becomes closer. Probability information can be selected by referring to non-zero coefficient information. The frequency domain segmentation may be split under the same condition in the encoding / decoding apparatus, or may be transmitted by encoding separate segmentation information to the decoding apparatus.

17 is a flowchart illustrating an arithmetic coding method according to an embodiment of the present invention. Referring to FIG. 17, binarized information is derived by binarizing a value of a transform coefficient to be encoded (S1701). Probability information to be applied to the encoding of the binarized information is determined according to the position of the transform coefficient in the transform block (S1703). Referring to the example illustrated in FIG. 16A, probability information to be applied is determined according to which region of the frequency A region 1601, the frequency B region 1602, or the frequency C region 1603 is included. Here, the frequency A region 1601, the frequency B region 1602, and the frequency C region 1603 may be classified according to distances from the DC coefficients located at the upper left corner of the transform block.

18 is a flowchart illustrating an arithmetic decoding method according to an embodiment of the present invention. Referring to FIG. 18, arithmetic encoded transform coefficient values are extracted from the bitstream (S1801). Probability information to be applied to decoding the arithmetic-coded transform coefficient is determined according to the position of the transform coefficient in the transform block (S1803). As described above, referring to the example illustrated in FIG. 16A, the probability information to be applied depends on which of the frequency A region 1601, the frequency B region 1602, or the frequency C region 1603 is included in the decoding. Can be determined. Here, the frequency A region 1601, the frequency B region 1602, and the frequency C region 1603 may be classified according to distances from the DC coefficients located at the upper left corner of the transform block.

Arithmetic encoding and arithmetic decoding according to another embodiment of the present invention will be described with reference to FIGS. 19A to 19C and 20.

In the present embodiment, when the method of encoding the quantized transform coefficients using the skip regions shown in FIGS. 7 to 9 is used, the current information is encoded or decoded according to whether the skip region is used or not. When different probability information is used.

It is assumed that the probability information table shown in FIG. 19B or 19C is used for encoding or decoding the coefficient current coefficient 1901 shown in FIG. 19A. The probability information table shown in FIG. 19B is a probability information table to be applied when a skip region is not used, and the probability information table shown in FIG. 19C is a probability information table applied when a skip region is used.

Referring to FIG. 19A, since a skip region exists in a transform block or subblock to which the current coefficient 1901 belongs, the probability information table illustrated in FIG. 19C is applied to encode or decode the current coefficient 1901. Thus, for example, index 5 is assigned to the current coefficient 1901. In this case, the probability of symbol 1 is 71% and the probability of symbol 0 is 29%.

Alternatively, probability information may be applied differently according to the number of N excess coefficients in the peripheral coefficients. Non-zero coefficient information and N excess coefficient information may use probability information having a high probability of occurrence according to the number of encoded / decoded information and the position of the frequency domain, and the coefficients located in the frequency C region and the skip region. , Probability information having a low probability of generating non-zero coefficient information, N excess coefficient information, and subblock information may be applied.

20 is a flowchart illustrating an arithmetic encoding or decoding method according to another embodiment of the present invention. As described above with reference to FIGS. 19A to 19C, different probability information is used when encoding or decoding current information according to a case where a skip region is used and a case where the skip region is not used.

Referring to FIG. 20, first, a position of a reference coefficient in a current transform block to be encoded or decoded is encoded or decoded (S2001). Thereafter, skip region information for the skip region selected based on the position of the reference coefficient is encoded or decoded (S2003). When binarized information is obtained by binarizing a value of a transform coefficient not included in the skip region, a probability information table to be applied to encoding the binarized information is selected from a plurality of probability information tables (S2005). Here, the plurality of probability information tables includes at least two tables for a case where a skip region is used and a table for a case where the skip region is not used.

The encoded information is subjected to context-adaptive binarization arithmetic through a binarization process. Context-adaptive binarization arithmetic refers to a process of symbolizing encoded information in a block and applying and encoding the occurrence probability of symbols differently using probability information according to a situation. In this example, only 0 and 1 symbols are used for convenience of description, but N symbols (N is a natural number of 2 or more) may be used.

21 is a flowchart illustrating a context-adaptive binarization arithmetic coding method. First, probability initialization is performed (S2101). Probability initialization is a process of dividing the probability section by the probability set in the probability information. However, as to what kind of probability information is to be used, the same condition may be used by a predetermined rule in the encoding apparatus or the decoding apparatus, or the probability information may be separately encoded. The initial probability interval may be determined in the same manner in the encoding / decoding process according to a preset rule. Alternatively, the initial probability interval may be newly encoded.

When the binary information of the current coding parameter to be encoded is determined (S2102), the binarized information of the current coding parameter is encoded using the probability interval state up to the previous step of step S2102 of FIG. 21 and previous probability information of the same coding parameter. (S2103). Probability information and a probability section may be updated (S2104) for binary information to be encoded later. When the coding parameter information to be encoded next exists (S2105), the process moves to the next coding parameter information (S2106), and the above-described process is repeated. If there is no coding parameter information to be encoded next, the flowchart ends.

22 is a flowchart illustrating a context-adaptive binarization arithmetic decoding method. Unlike the encoding apparatus, the decoding apparatus decodes binary information of a coding parameter using probability information and an interval (S2202), and then determines binary information of the current coding parameter (S2203). In addition, since the decoding method of FIG. 22 corresponds to the encoding method of FIG. 21, detailed description thereof will be omitted.

In steps S2103 and S2202 of FIGS. 21 and 22 described above, among the N pieces of probability information preset by using information (or coding parameters) already reconstructed around each coding parameter, encoding or using optimal probability information is selectively used. Decoding may proceed.

For example, the probability information of the information (or coding parameter) belonging to the quantized transform block may use probability information having a high probability of generating information according to the size of the transform block.

23A and 23B illustrate an example in which probability information is differently applied according to information of neighboring coefficients.

23A is an example of a probability information table used for encoding or decoding a Sig_coeff_flag information value of a current coefficient. If the number of coefficients having the same information value as the Sig_coeff_flag information value of the current coefficient among the coefficients adjacent to the coefficient to be encoded or decoded is one, the index 8 is assigned to the current coefficient. In this case, the probability of symbol 1, which is Sig_coeff_flag binary information of the current coefficient, is 61%, and the probability of symbol 0 is 39%. If the number of neighboring coefficients having the same information value as the Sig_coeff_flag information value of the current coefficient is two, index 5 is assigned to the current coefficient, and the probability of symbol 1, which is Sig_coeff_flag binary information of the current coefficient, is 71% and symbol 0 The probability of is 29%. If there are three neighboring coefficients with the same information value as the Sig_coeff_flag information value of the current coefficient, index 2 is assigned to the current coefficient, and the probability of symbol 1, which is Sig_coeff_flag binary information of the current coefficient, is 87%, and symbol 0 is 13%. Becomes

After the current coefficient is encoded or decoded using the probability information table illustrated in FIG. 23A, the probability information may be updated as shown in FIG. 23B.

On the other hand, in the case of non-zero coefficient information Sig_coeff_flag, probability information having a higher probability of generating non-zero coefficient information Sig_coeff_flag may be used as it is closer to the low frequency region.

For the probability information of the N excess coefficient information, the probability information of the current N excess coefficient information is set using the probability information of the N excess coefficient information encoded / decoded immediately before, or the N excess that is first encoded / decoded in units of subblocks. Probability information of coefficient information may be used as it is. As described above, the N excess coefficient information may include Abs_greater1_flag, Abs_greater2_flag, Abs_greater3_flag, and the like.

The sub block information Coded_sub_blk_flag may use probability information of neighboring coded / decoded M subblocks or use probability information of a previously encoded / decoded subblock.

(Third Embodiment)

24 is a flowchart illustrating a method of determining probability information of each coding parameter according to a reference coefficient position and encoding the information of each coding parameter using the same according to an embodiment of the present invention. The flowchart of FIG. 24 may be performed by the entropy encoder 107 of the image encoding apparatus 100.

Referring to FIG. 24, first, the entropy encoder 107 encodes a position of a reference coefficient in a current transform block to be encoded (S2401). Here, the reference coefficient position may be encoded by reference coefficient position information Last_sig.

As described above, the reference coefficient may mean the first non-zero coefficient when scanning coefficients in an inverse scan order, but the reference coefficient may be applied to other conditions that are equally set in the image encoding apparatus 100 and the image decoding apparatus 200. It can also be determined by.

Thereafter, probability information of each coding parameter is derived based on the position of the reference coefficient, and the corresponding coding parameter is encoded (S2402).

Here, the method of setting the probability table according to the position of the reference coefficient refers to the drawing example of FIG. 25.

Referring to FIG. 25, the A region 2500 refers to an arbitrary region close to the DC coefficient in the transform block, and the B region 2501 refers to a region other than the A region 2500 in the transform block. It is also possible to divide the transform block into N or more regions. In this case, arbitrary region information indicating the region A may be transmitted from an upper header, or may be determined under the same condition according to the transform block type in the image encoding apparatus 100 and the image decoding apparatus 200.

In FIG. 25, the probability information of the coding parameters may be differently derived and the probability information of the coding parameters may be updated in a single probability table according to whether the location of the reference coefficient exists in the A region 2500 or the B region 2501. have.

Alternatively, the probability information of the coding parameters may be updated by using two or more different initial probability tables or the same initial probability table independently according to whether the position of the reference coefficient exists in the A region or the B region.

In the following, detailed examples of the above-described method will be described.

In the case of encoding by using two identical initial probability tables independently to derive probability information of Sig_coeff_flag information indicating whether each coefficient in the transform block is 0 or not, the reference coefficient of the transform block exists in the region A 2500. In the case of using the (2600) table of FIG. 26A and in the B region 2501, the probability information of the Sig_coeff_flag information may be independently updated using the (2601) table of FIG. 26A.

The probability table 2260 of FIG. 26B is a result of updating the probability information by determining probability table index information according to the reference coefficient position as 5 in the initial probability table 2260 of FIG. 26A, and the probability table of 2260 of FIG. 26B. The probability table index information according to the reference coefficient position is determined as 8 in the initial probability table (2601) of FIG. 26A, and the probability information is updated.

In the same principle as the above example, the probability information of the Abs_greater1_flag information indicating whether the absolute value of the coefficient in the transform block is greater than 1 is selected as the probability information having the high probability that the Abs_greater1_flag information is 1 when the reference coefficient is in the A region. When the reference coefficient is in the B region, the probability information having a high probability that Abs_greater1_flag information is 0 may be selected and encoded.

Meanwhile, in the method of determining index information indicating which probability to use in the probability table, the index information may be determined according to the detailed coordinates of the reference coefficient.

For example, when the detailed coordinates of the reference coefficient in the transform block are located at the top left of the region A (2502 of FIG. 25), index information of the probability table according to the reference coefficient position in the initial probability table of 2600 of FIG. 26A. May be determined as 5. And, like the probability table 2260 of FIG. 26B, the probability information of the index information 5 may be updated.

When the detailed coordinates of the reference coefficients in the transform block are located at the center of the region B (2503 of FIG. 25), the index information of the probability table according to the reference coefficient position is 8 in the initial probability table of 2601 of FIG. 26A. Can be determined. The probability information of the index information 8 may be updated as in the probability table of FIG. 26B. 27 is a flowchart illustrating a method of determining probability information of each coding parameter according to a reference coefficient position and decoding the information of each coding parameter using the same according to an embodiment of the present invention. The decoding method of FIG. 27 may be performed by the entropy decoding unit 201 of the image decoding apparatus 200.

Referring to FIG. 27, first, the entropy decoding unit 201 decodes the position of the reference coefficient in the current transform block to be decoded (S2701). As mentioned above, the reference coefficient refers to the first non-zero coefficient when scanning the coefficients in reverse scan order. Thereafter, probability information of each coding parameter is derived based on the position of the reference coefficient and the corresponding parameter information is decoded (S2702).

(Fourth embodiment)

28 is a flowchart illustrating a method of deriving and encoding probability information of each coding parameter according to partial information of a DC coefficient according to an embodiment of the present invention. The encoding method of FIG. 28 may be performed by the entropy encoder 107 of the image encoding apparatus 100.

Referring to FIG. 28, partial information of a DC coefficient may be encoded (S2801), and probability information of each coding parameter may be derived based on the partial information of DC, and corresponding parameter information may be encoded (S2802).

Here, the DC coefficient may be a coefficient located at the top left of the transform block or may be a non-zero coefficient (non-zero coefficient) that comes last in an inverse scan order.

In addition, here, the partial information of the DC coefficient means some partial information necessary for encoding and decoding the DC coefficient. For example, the partial information of the DC coefficient may mean at least one of Sig_coeff_flag information and Abs_greater1_flag information of the DC coefficient.

Based on the partial information of the DC coefficients, the probability information of the coding parameters except for the partial information of the DC coefficients may be differently derived in the single probability table, and the probability information of the coding parameters may be updated.

Alternatively, the probability information of the coding parameters may be updated using two or more different initial probability tables or the same initial probability table independently based on the partial information of the DC coefficients.

In order to derive probability information of Sig_coeff_flag information indicating whether each coefficient in the transform block is 0, two independent initial probability tables are independently encoded and only partial information of DC coefficients may use Sig_coeff_flag information. When the partial information of the DC coefficient is 0, the (2600) table of FIG. 26A is used, and when the DC information is 1, the probability information of the Sig_coeff_flag information is independently updated by using the (2601) table of FIG. 26A. Can be.

In the same principle as in the above example, the probability information of the Abs_greater1_flag information indicating whether the absolute value of the coefficient in the transform block is greater than 1 is the probability information that the Abs_greater1_flag information has a high probability of 1 when Sig_coeff_flag, which is a partial information of the DC coefficient, is 1; When Sig_coeff_flag which is partial information of the DC coefficient is 0, probability information having a high probability that Abs_greater1_flag information is 0 may be selected and encoded.

In the method of determining index information indicating which probability to use in the probability table, the index information may be determined according to the partial information of the DC coefficient.

For example, when Sig_coeff_flag information of the current encoding coefficient is 1, index information of the initial probability table of 2600 of FIG. 26A may be determined as 5. Probability information of index information 5 may be updated as in the probability table 2260 of FIG. 26B.

When the Sig_coeff_flag information of the current encoding coefficient is 0, index information of the initial probability table of 2601 of FIG. 26A may be determined as 8. Probability information of index information 8 may be updated as in the probability table of FIG. 26B.

After encoding the reference coefficient information (S2901), partial information of the DC coefficient is encoded (S2902). In this case, when the position of the DC coefficient is preset in the encoding / decoding apparatus, the position encoding process of the DC coefficient may be omitted. If not, the position of the DC coefficient is encoded (S2903). If reference coefficients are included in the subblocks in the transform block, it means that the coefficients to be encoded are included, so coded_sub_blk_flag, which is subblock information, is not encoded. Thereafter, the coefficients are encoded in the order of nonzero coefficient information encoding (S2906), N excess coefficient information encoding (S2907), code information encoding (S2908), and residual coefficient information encoding (S2909). However, since the partial information of the DC coefficient has already been encoded, the steps used for the DC coefficient partial information during the DC coefficient encoding in steps S2906 to S2909 may be omitted.

Thereafter, when the next subblock exists (S2911), the process moves to the next subblock (S2912), and information is encoded in order from (S2906) to (S2909), and when the next subblock does not exist, the algorithm ends. do.

30 is a flowchart illustrating a method of deriving and decoding probability information of each coding parameter according to partial information of a DC coefficient according to an embodiment of the present invention. The decoding method of FIG. 30 may be performed by the entropy decoding unit 201 of the image decoding apparatus 200.

Referring to FIG. 30, first, the entropy decoding unit 201 decodes partial information of a DC coefficient (S3001), and then derives probability information of each coding parameter based on the partial information of the DC coefficient and decodes corresponding parameter information. (S3002).

After decoding the reference coefficient information (S3101), the partial information of the DC coefficient is decoded (S3102). In this case, when the position of the DC coefficient is preset in the encoding / decoding apparatus, the position decoding process of the DC coefficient may be omitted. If not, the position of the DC coefficient is decoded (S3103). If the reference coefficient is included in the subblock in the transform block, it means that the coefficient to be decoded is included. Therefore, Coded_sub_blk_flag, which is subblock information, is not decoded. Thereafter, non-zero coefficient information decoding (S3106), N excess coefficient information decoding (S3107), code information decoding (S3108), and residual coefficient information decoding (S3109) are performed in this order. However, since the partial information of the DC coefficient has already been decoded, the steps used for the DC coefficient partial information during the DC coefficient decoding in steps S3106 to S3109 may be omitted.

Thereafter, when the next subblock exists (S3111), the process moves to the next subblock (S3112), and the information is decoded in order from (S3106) to (S3109), and when the next subblock does not exist, the algorithm ends. do.

(Fifth Embodiment)

32 is a flowchart illustrating a method of deriving and encoding probability information of each coding parameter according to a distance between a DC coefficient and a reference coefficient and partial information of the DC coefficient according to an embodiment of the present invention. The encoding method of FIG. 32 may be performed by the entropy encoder 107 of the image encoding apparatus 100.

Referring to FIG. 32, the entropy encoder 107 encodes the position of the reference coefficient of the current transform block (S3201). As described above, the reference coefficient may mean the first non-zero coefficient when scanning coefficients in an inverse scan order, but the reference coefficient may be applied to other conditions that are equally set in the image encoding apparatus 100 and the image decoding apparatus 200. It can also be determined by. After encoding the partial information of the DC coefficient, the probability information of the coding parameters is derived based on the distance between the DC coefficient and the reference coefficient and the partial information of the DC coefficient, and the corresponding parameter information is encoded (S3202).

Here, the DC coefficient may be a coefficient coefficient located at the top left of the transform block or may be a non-zero coefficient (non-zero coefficient) that comes last in an inverse scan order.

Based on the distance between the DC coefficient and the reference coefficient and the partial information of the DC coefficient, the probability information of the coding parameters except the partial information of the DC coefficient may be differently derived in the single probability table, and the probability information of the coding parameters may be updated.

Alternatively, based on the distance between the DC coefficient and the reference coefficient and the partial information of the DC coefficient, two or more different initial probability tables or the same initial probability table may be independently used to update probability information of the coding parameters.

Here, in the method for determining the distance information between the DC coefficient and the reference coefficient, the distance information may be determined or the distance information may be encoded in the same manner according to a predetermined rule in the encoding / decoding apparatus.

In order to derive probability information of Sig_coeff_flag information indicating whether each coefficient in the transform block is 0 or not, three independent initial probability tables are independently encoded and only partial information of DC coefficients may use Sig_coeff_flag information. If the distance information of the DC coefficient and the reference coefficient is greater than a predetermined threshold value, the table 3300 of FIG. 33 is used. If the distance between the DC coefficient and the reference coefficient is smaller than the predetermined threshold value, FIG. 33. Use the (3301) or (3302) table of. The predetermined threshold may be a value preset in the encoding / decoding apparatus or a value based on information determined by the encoding apparatus and transmitted to the decoding apparatus. In this case, which probability table to use (3301) or (3302) may be determined based on the partial information of the DC coefficient. For example, if Sig_coeff_flag information, which is partial information of the DC coefficient, is 1, the probability information may be determined using the table 3301 of FIG. 33 and using the table 3302 of FIG.

Meanwhile, in the method of determining index information indicating which probability to use in the probability table, the index information is determined based on the distance information between the DC coefficient and the reference coefficient, and then the index information determined based on the partial information of the DC coefficient is corrected. Can be.

34 is a flowchart illustrating a method of deriving and decoding probability information of each coding parameter according to a distance between a DC coefficient and a reference coefficient and partial information of the DC coefficient according to an embodiment of the present invention. The decoding method of FIG. 34 may be performed by the entropy decoding unit 201 of the image decoding apparatus 200.

Referring to FIG. 34, the entropy decoding unit 201 decodes the position of the reference coefficient of the current transform block and the partial information of the DC coefficient (S3401). As described above, the reference coefficient may mean the first non-zero coefficient when scanning the coefficients in the reverse scanning order, but the reference coefficient may be applied to other conditions that are identically set in the image encoding apparatus 100 and the image decoding apparatus 200. It can also be determined by. Then, the probability information of the coding parameters is derived based on the distance between the DC coefficient and the reference coefficient and the partial information of the DC coefficient, and the corresponding parameter information is decoded (S3402).

The encoding / decoding algorithms of the image encoding apparatus 100 and the image decoding apparatus 200 may be the same as those of FIGS. 29 and 31.

Exemplary methods of the present disclosure are represented as a series of operations for clarity of description, but are not intended to limit the order in which the steps are performed, and each step may be performed simultaneously or in a different order as necessary. In order to implement the method according to the present disclosure, the illustrated step may further include other steps, may include other steps except some, or may include additional other steps except some.

The various embodiments of the present disclosure are not an exhaustive list of all possible combinations and are intended to describe representative aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more.

In addition, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. For hardware implementations, one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), General Purpose It may be implemented by a general processor, a controller, a microcontroller, a microprocessor, and the like.

It is intended that the scope of the disclosure include software or machine-executable instructions (eg, an operating system, an application, firmware, a program, etc.) to cause an operation in accordance with various embodiments of the method to be executed on an apparatus or a computer, and such software or Instructions, and the like, including non-transitory computer-readable media that are stored and executable on a device or computer.

The present invention can be used in an apparatus for encoding / decoding an image.

Claims

Decoding the position of the reference coefficient within the current transform block to be decoded; And

Decoding skip region information on the selected skip region based on the position of the reference coefficient;

The skip region information indicates whether coefficients in the skip region have the same coefficient value.
The method of claim 1,

And the reference coefficient is a first non-zero coefficient in an inverse scan order of coefficients in the current transform block.
The method of claim 1,

And decoding information indicating the same coefficient value when the same coefficient value of the coefficients in the skip region is not zero.
The method of claim 1,

Decoding the additional skip region information;

The additional skip region information indicates whether coefficients in a region other than the skip region have the same coefficient value.
The method of claim 1,

The skip area is an area including at least one of coefficients on the line or coefficients belonging to an area in one direction based on the line when a line is drawn in a predetermined direction at the position of the reference coefficient. A video decoding method.
The method of claim 1,

The skip region may include at least one of coefficients on the line or coefficients belonging to an area in one direction based on the line when the line is drawn from the position of the reference coefficient to the coefficient position of the lower left corner in the current transform block. And a region including coefficients.
The method of claim 4, wherein

And the additional skip region is an area adjacent to the skip region.
The method of claim 4, wherein

And the additional skip region is an area selected based on the line when a line is drawn in a predetermined direction at a position other than the reference coefficient other than the reference coefficient.
Obtaining a value of an arithmetic coded transform coefficient from the bitstream; And

And determining probability information to be applied to decoding the arithmetic-coded transform coefficient according to the position of the transform coefficient within the transform block.
The method of claim 9,

Determining the probability information,

And probability information to be applied to decoding the arithmetic-coded transform coefficient according to which region the transform coefficient is located in a transform block divided into a plurality of regions.
The method of claim 9,

And a plurality of regions in the transform block are divided based on the DC position of the transform block.
Decoding the position of the reference coefficient within the current transform block to be decoded;

Decoding skip region information on a skip region selected based on the position of the reference coefficient;

Obtaining an arithmetic coded value of a transform coefficient not included in the skip region; And

Selecting, from a plurality of probability information tables, a probability information table to be applied to decoding an arithmetic coded value of the transform coefficient;

Here, the step of selecting the probability information table,

And selecting one of the plurality of probability information tables according to whether the skip region is used to decode the current transform block.
Decoding the position of the reference coefficient in the current transform block;

Deriving probability information of a coding parameter based on the position of the reference coefficient; And

And decoding the coding parameter by using the derived probability information.
The method of claim 13,

The current transform block is divided into a first region and a second region,

The probability information of the coding parameter is determined based on which region the reference coefficient exists in.
Decoding partial information of the DC coefficient of the current transform block;

Deriving probability information of a coding parameter based on the partial information of the DC coefficient; And

And decoding the coding parameter by using the derived probability information.
The method of claim 15,

And the DC coefficient is a coefficient located at the upper left end of the current transform block.
The method of claim 15,

And the partial information of the DC coefficients is at least one of information for decoding the DC coefficients.
The method of claim 15,

Decoding a position of a reference coefficient in the current transform block;

The probability information of the coding parameter is derived based on distance information between the DC coefficient and the reference coefficient and partial information of the DC coefficient.