KR102286856B1 - A method and an apparatus for encoding/decoding a scalable video signal - Google Patents

Abstract

A scalable video signal decoding method according to the present invention obtains a filter coefficient of an upsampling filter applied to a reference picture of a reference layer, and applies the obtained filter coefficient to the reference picture to generate an inter-layer reference picture, It is characterized in that inter prediction is performed on the current block of the current layer based on the generated inter-layer reference picture.

Description

A method and apparatus for encoding/decoding a scalable video signal

The present invention relates to a method and apparatus for encoding/decoding a scalable video signal.

Recently, demand for high-resolution and high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images is increasing in various application fields. As the image data becomes higher resolution and higher quality, the amount of data relatively increases compared to the existing image data. storage costs will increase. High-efficiency image compression techniques can be used to solve these problems that occur as image data becomes high-resolution and high-quality.

Inter-screen prediction technology that predicts pixel values included in the current picture from pictures before or after the current picture with image compression technology, intra-picture prediction technology that predicts pixel values included in the current picture using pixel information in the current picture, Various techniques exist, such as entropy encoding technology in which a short code is assigned to a value with a high frequency of occurrence and a long code is assigned to a value with a low frequency of occurrence.

Meanwhile, as the demand for high-resolution images increases, the demand for stereoscopic image content as a new image service is also increasing. A video compression technique for effectively providing high-resolution and ultra-high-resolution stereoscopic image content is being discussed.

An object of the present invention is to provide a method and apparatus for upsampling a reference picture of a reference layer in encoding/decoding a scalable video signal.

An object of the present invention is to provide a method and apparatus for constructing a reference picture list using an inter-layer reference picture in encoding/decoding a scalable video signal.

An object of the present invention is to provide a method and apparatus for effectively deriving texture information of a current layer through inter-layer prediction in encoding/decoding a scalable video signal.

A scalable video signal decoding method and apparatus according to the present invention is characterized in that a reference picture of a reference layer is upsampled by selectively using a fixed upsampling filter and an adaptive upsampling filter.

A scalable video signal decoding method and apparatus according to the present invention is characterized by selectively using a fixed upsampling filter and an adaptive upsampling filter for each of a luminance component and a chrominance component.

A scalable video signal decoding method and apparatus according to the present invention is characterized by selectively using a fixed upsampling filter and an adaptive upsampling filter for each of a luminance component and a chrominance component Cb and Cr.

A scalable video signal decoding method and apparatus according to the present invention is characterized in that filter coefficients of an adaptive upsampling filter are adaptively obtained for each phase of a reference sample.

A scalable video signal encoding method and apparatus according to the present invention is characterized in that a reference picture of a reference layer is upsampled by selectively using a fixed upsampling filter and an adaptive upsampling filter.

A scalable video signal encoding method and apparatus according to the present invention is characterized by selectively using a fixed upsampling filter and an adaptive upsampling filter for each of a luminance component and a chrominance component.

A scalable video signal encoding method and apparatus according to the present invention is characterized by selectively using a fixed upsampling filter and an adaptive upsampling filter for each of a luminance component and a chrominance component Cb and Cr.

A scalable video signal encoding method and apparatus according to the present invention is characterized in that filter coefficients of an adaptive upsampling filter are adaptively obtained for each phase of a reference sample.

According to the present invention, the reference picture of the reference layer can be effectively upsampled by selectively using the adaptive upsampling filter reflecting the characteristics of the image.

In addition, according to the present invention, it is possible to effectively construct a reference picture list using an inter-layer reference picture.

Also, according to the present invention, texture information of the current layer can be effectively derived through inter-layer prediction.

1 is a block diagram schematically illustrating an encoding apparatus according to an embodiment of the present invention.
2 is a block diagram schematically illustrating a decoding apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating a process of performing inter-layer prediction of a current layer using a reference picture of a reference layer as an embodiment to which the present invention is applied.
4 illustrates a method of selectively using an adaptive upsampling filter for a reference picture as an embodiment to which the present invention is applied.
5 illustrates a method of selectively using an adaptive upsampling filter for each of a luminance component and a chrominance component as an embodiment to which the present invention is applied.
6 illustrates a method of selectively using an adaptive upsampling filter for each of a luminance component and two color difference components (Cb and Cr) according to an embodiment to which the present invention is applied.
7 illustrates a method of obtaining filter coefficients of an adaptive upsampling filter based on a first adaptive component flag as an embodiment to which the present invention is applied.
8 illustrates a method of obtaining filter coefficients of an adaptive upsampling filter based on a second adaptive component flag as an embodiment to which the present invention is applied.
9 illustrates a method of adaptively obtaining filter coefficients for each phase of a reference sample as an embodiment to which the present invention is applied.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the configuration shown in the embodiments and drawings described in the present specification is only the most preferred embodiment of the present invention and does not represent all of the technical spirit of the present invention, so at the time of the present application, various It should be understood that there may be equivalents and variations.

When a component is referred to as being “connected” or “connected” to another component in the present specification, it may mean that it is directly connected or connected to the other component, or another component in the middle. It can also mean that the element is present. In addition, the description of "including" a specific configuration in the present specification does not exclude configurations other than the corresponding configuration, and means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Terms such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first configuration may be called a second configuration, and similarly, a second configuration may also be called a first configuration.

In addition, the components shown in the embodiment of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is formed of separate hardware or a single software component. That is, each component is included in a list for convenience of description, and at least two components among each component may constitute one component, or one component may be divided into a plurality of components to perform a function. Integrated embodiments and separate embodiments of each component are also included in the scope of the present invention without departing from the essence of the present invention.

In addition, some of the components are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

Coding and decoding of a video supporting a plurality of layers in a bitstream is referred to as scalable video coding. Since a strong correlation exists between a plurality of layers, if prediction is performed using the correlation, duplicate elements of data may be removed and image encoding performance may be improved. Prediction of the current layer using information of another layer is hereinafter referred to as inter-layer prediction or inter-layer prediction.

The plurality of layers may have different resolutions, and the resolution may mean at least one of spatial resolution, temporal resolution, and image quality. In order to adjust the resolution in inter-layer prediction, resampling such as up-sampling or down-sampling of a layer may be performed.

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

The encoding apparatus 100 according to the present invention includes an encoder 100a for an upper layer and an encoder 100b for a lower layer.

The upper layer may be expressed as a current layer or an enhancement layer, and the lower layer may be expressed as an enhancement layer, a base layer, or a reference layer having a lower resolution than the upper layer. . At least one of a spatial resolution, a temporal resolution according to a frame rate, and an image quality according to a color format or a quantization size of the upper layer and the lower layer may be different from each other. When a resolution change is required to perform inter-layer prediction, layer upsampling or downsampling may be performed.

The encoding unit 100a of the upper layer includes a division unit 110 , a prediction unit 120 , a transform unit 130 , a quantization unit 140 , a reordering unit 150 , an entropy encoding unit 160 , and an inverse quantization unit ( 170 ), an inverse transform unit 180 , a filter unit 190 , and a memory 195 .

The encoding unit 100b of the lower layer includes a division unit 111 , a prediction unit 125 , a transform unit 131 , a quantization unit 141 , a reordering unit 151 , an entropy encoding unit 161 , and an inverse quantization unit ( 171 ), an inverse transform unit 181 , a filter unit 191 , and a memory 196 .

The encoding unit may be implemented by the image encoding method described in the following embodiments of the present invention, but operations in some components may not be performed in order to reduce the complexity of the encoding apparatus or for fast real-time encoding. For example, when the prediction unit performs intra prediction, in order to perform encoding in real time, a method of selecting an optimal intra prediction method using all intra prediction mode methods is not used, but a limited number of A method of selecting one intra prediction mode from among the intra prediction modes as the final intra prediction mode by using the intra prediction mode of may be used. As another example, it is possible to restrict the use of the form of a prediction block used in performing intra prediction or inter prediction.

A unit of a block processed by the encoding apparatus may be a coding unit for performing encoding, a prediction unit for performing prediction, and a transformation unit for performing transformation. A coding unit may be expressed as a coding unit (CU), a prediction unit may be expressed as a prediction unit (PU), and a transformation unit may be expressed by terms of a transform unit (TU).

The division units 110 and 111 divide the layer image into a combination of a plurality of coding blocks, prediction blocks, and transform blocks, and use one of the coding blocks, prediction blocks, and transform blocks according to a predetermined criterion (eg, a cost function). You can split the layer by selecting a combination of . For example, a recursive tree structure such as a quadTree structure may be used to split a coding unit in a layer image. Hereinafter, in an embodiment of the present invention, the meaning of a coding block may be used not only as a block for encoding but also as a block for performing decoding.

A prediction block may be a unit for performing prediction such as intra prediction or inter prediction. A block for performing intra prediction may be a square-shaped block such as 2Nx2N or NxN. As a block for performing inter prediction, there is a prediction block partitioning method using Asymmetric Motion Partitioning (AMP), which is a square shape such as 2Nx2N or NxN, a rectangular shape such as 2NxN or Nx2N, or an asymmetric shape. According to the shape of the prediction block, the method of performing the transformation in the transform unit 115 may vary.

The prediction units 120 and 125 of the encoders 100a and 100b are the intra prediction units 121 and 126 that perform intra prediction and the inter prediction units that perform inter prediction. (122, 127). The prediction unit 120 of the higher layer encoder 100a may further include an inter-layer prediction unit 123 that performs prediction on the upper layer by using the information of the lower layer.

The prediction units 120 and 125 may determine whether to use inter prediction or to perform intra prediction for the prediction block. In performing intra prediction, the process of determining the intra prediction mode in units of prediction blocks and performing intra prediction based on the determined intra prediction mode may be performed in units of transform blocks. A residual value (residual block) between the generated prediction block and the original block may be input to the transform units 130 and 131 . Also, prediction mode information, motion information, etc. used for prediction may be encoded by the entropy encoder 130 together with the residual value and transmitted to the decoding apparatus.

When the PCM (Pulse Coded Modulation) encoding mode is used, the original block may be encoded and transmitted to the decoder without performing prediction through the predictors 120 and 125 .

The intra prediction units 121 and 126 may generate an intra prediction block based on reference pixels existing around the current block (block to be predicted). In the intra prediction method, the intra prediction mode may have a directional prediction mode in which a reference pixel is used according to a prediction direction and a non-directional mode in which the prediction direction is not considered. A mode for predicting luma information and a mode for predicting color difference information may be different. In order to predict the color difference information, an in-screen prediction mode in which the luma information is predicted or the predicted luma information may be utilized. If the reference pixel is not available, a prediction block may be generated by replacing the unavailable reference pixel with another pixel.

The prediction block may include a plurality of transform blocks, and when the size of the prediction block and the size of the transform block are the same when intra prediction is performed, a pixel present at the left side of the prediction block, a pixel present at the upper left corner, and an upper side of the prediction block Intra-prediction of the prediction block may be performed based on pixels existing in . However, when a plurality of transform blocks are included in the prediction block because the size of the prediction block is different from the size of the transform block when intra prediction is performed, intra prediction is performed using neighboring pixels adjacent to the transform block as reference pixels. can be done Here, the neighboring pixels adjacent to the transform block may include at least one of the neighboring pixels adjacent to the prediction block and pixels already decoded in the prediction block.

The intra prediction method may generate a prediction block after applying a Mode Dependent Intra Smoothing (MDIS) filter to a reference pixel according to an intra prediction mode. The type of MDIS filter applied to the reference pixel may be different. The MDIS filter is an additional filter applied to an intra-predicted block in which intra-prediction is performed, and may be used to reduce a residual existing in a reference pixel and an intra-predicted block generated after performing prediction. In performing MDIS filtering, different filtering may be performed depending on the direction of the intra prediction mode for the reference pixel and some columns included in the intra prediction block.

The inter prediction units 122 and 127 may perform prediction with reference to information on a block included in at least one of a picture before or after the current picture. The inter prediction units 122 and 127 may include a reference picture interpolator, a motion prediction unit, and a motion compensator.

The reference picture interpolator may receive reference picture information from the memories 195 and 196 and generate pixel information of integer pixels or less in the reference picture. In the case of luma pixels, a DCT-based 8-tap interpolation filter in which filter coefficients are different may be used to generate pixel information of integer pixels or less in units of 1/4 pixels. In the case of the color difference signal, a DCT-based 4-tap interpolation filter in which filter coefficients are different to generate pixel information of integer pixels or less in units of 1/8 pixels may be used.

The inter prediction units 122 and 127 may perform motion prediction based on the reference picture interpolated by the reference picture interpolator. As a method for calculating the 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 unit based on the interpolated pixel. The inter prediction units 122 and 127 may predict the current block by applying one inter prediction method among various inter prediction methods.

Various methods such as a skip method, a merge method, and a method using a motion vector predictor (MVP) may be used as the inter prediction method.

In inter prediction, motion information, that is, information such as a reference index, a motion vector, and a residual signal, is entropy-encoded and transmitted to a decoder. Since a residual signal is not generated when the skip mode is applied, a process of transforming and quantizing the residual signal may be omitted.

The inter-layer prediction unit 123 performs inter-layer prediction for predicting an upper layer using information of a lower layer. The inter-layer prediction unit 123 may perform inter-layer prediction using texture information and motion information of a lower layer.

In the inter-layer prediction, the current block of the higher layer may be predicted by using the picture of the lower layer as a reference picture and motion information on the picture of the lower layer (reference layer). A picture of a reference layer used as a reference picture in inter-layer prediction may be a picture sampled to match the resolution of the current layer. Also, the motion information may include a motion vector and a reference index. In this case, the value of the motion vector for the picture of the reference layer may be set to (0, 0).

As an example of inter-layer prediction, a prediction method using a picture of a lower layer as a reference picture has been described, but the present invention is not limited thereto. The inter-layer prediction unit 123 may perform inter-layer texture prediction, inter-layer motion prediction, inter-layer syntax prediction, and inter-layer differential prediction.

Inter-layer texture prediction can derive the texture of the current layer based on the texture of the reference layer. The texture of the reference layer may be sampled according to the resolution of the current layer, and the inter-layer prediction unit 123 may predict the texture of the current layer based on the sampled texture of the reference layer.

The inter-layer motion prediction may derive the motion vector of the current layer based on the motion vector of the reference layer. In this case, the motion vector of the reference layer may be scaled to fit the resolution of the current layer. In the inter-layer syntax prediction, the syntax of the current layer may be predicted based on the syntax of the reference layer. For example, the inter-layer prediction unit 123 may use the syntax of the reference layer as the syntax of the current layer. Also, in the inter-layer differential prediction, the picture of the current layer may be reconstructed by using a difference between the reconstructed image of the reference layer and the reconstructed image of the current layer.

A residual block including residual information that is a difference value between the prediction block generated by the prediction units 120 and 125 and the reconstructed block of the prediction block is generated, and the residual block is input to the transform units 130 and 131 .

The transform units 130 and 131 may transform the residual block using a transform method such as DCT (Discrete Cosine Transform) or DST (Discrete Sine Transform). Whether DCT or DST is applied to transform the residual block may be determined based on intra prediction mode information of the prediction block used to generate the residual block and size information of the prediction block. That is, the transform units 130 and 131 may apply a different transform method according to the size of the prediction block and the prediction method.

The quantizers 140 and 141 may quantize the values transformed into the frequency domain by the transforms 130 and 131 . The quantization coefficient may change according to blocks or the importance of an image. The values calculated by the quantizers 140 and 141 may be provided to the inverse quantizers 170 and 17 and the reordering units 150 and 151 .

The reordering units 150 and 151 may rearrange coefficient values on the quantized residual values. The reordering units 150 and 151 may change the two-dimensional block form coefficient into a one-dimensional vector form through a coefficient scanning method. For example, the rearranging units 150 and 151 may scan from DC coefficients to coefficients in a high frequency region using a zig-zag scan method and may change them into a one-dimensional vector form. Depending on the size of the transform block and the intra prediction mode, there are a vertical scan method that scans two-dimensional block shape coefficients in the column direction, not a zig-zag scan method, and a horizontal scan method that scans two-dimensional block shape coefficients in the row direction. can be used That is, according to the size of the transform block and the intra prediction mode, it is possible to determine which scan method among the zig-zag scan, the vertical scan, and the horizontal scan is to be used.

The entropy encoding units 160 and 161 may perform entropy encoding based on the values calculated by the reordering units 150 and 151 . For entropy encoding, various encoding methods such as Exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) may be used.

The entropy encoders 160 and 161 receive the residual value coefficient information and block type information of the coding block from the reordering units 150 and 151 and the prediction units 120 and 125, the prediction mode information, the division unit information, the prediction block information, and transmission. Entropy encoding may be performed based on a predetermined encoding method by receiving various information such as unit information, motion information, reference frame information, interpolation information of a block, and filtering information. Also, the entropy encoders 160 and 161 may entropy-encode the coefficient values of the coding units input from the reordering units 150 and 151 .

The entropy encoders 160 and 161 may encode the intra prediction mode information of the current block by performing binarization on the intra prediction mode information. The entropy encoders 160 and 161 may include a codeword mapping unit for performing such a binarization operation, and may perform binarization differently according to the size of a prediction block performing intra prediction. In the codeword mapping unit, the codeword mapping table may be adaptively generated through a binarization operation or stored in advance. In another embodiment, the prediction mode information in the current picture may be expressed using the codenum mapping unit performing codenum mapping and the codeword mapping unit performing codeword mapping in the entropy encoders 160 and 161 . The codenum mapping unit and the codeword mapping unit may generate or store a codenum mapping table and a codeword mapping table.

The inverse quantizers 170 and 171 and the inverse transform units 180 and 181 inverse quantize the values quantized by the quantizers 140 and 141 and inversely transform the values transformed by the transform units 130 and 131 . The residual values generated by the inverse quantizers 170 and 171 and the inverse transform units 180 and 181 are predicted through the motion estimation unit, the motion compensation unit, and the intra prediction unit included in the prediction units 120 and 125 . It may be combined with the prediction block to generate a reconstructed block.

The filter units 190 and 191 may include at least one of a deblocking filter and an offset correcting unit.

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

The offset correcting unit may correct an offset from the original image in units of pixels with respect to the image on which the deblocking has been performed. In order to perform offset correction on a specific picture, a method of dividing pixels included in an image into a certain region, determining the region to be offset and applying the offset to the region, or applying the offset by considering the edge information of each pixel method can be used.

The filter units 190 and 191 may apply only the deblocking filter without applying both the deblocking filter and the offset correction, or may apply both the deblocking filter and the offset correction.

The memories 195 and 196 may store the reconstructed blocks or pictures calculated through the filter units 190 and 191, and the stored reconstructed blocks or pictures may be provided to the predictors 120 and 125 when inter prediction is performed. there is.

Information output from the entropy encoder 100b of the lower layer and information output from the entropy encoder 100a of the upper layer may be multiplexed by the MUX 197 and output as a bitstream.

The MUX 197 may be included in the encoder 100a of the upper layer or the encoder 100b of the lower layer, or may be implemented as an independent device or module separate from the encoder 100 .

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

As shown in FIG. 2 , the decoding apparatus 200 includes a decoding unit 200a of an upper layer and a decoding unit 200b of a lower layer.

The decoding unit 200a of the upper layer includes an entropy decoding unit 210 , a reordering unit 220 , an inverse quantization unit 230 , an inverse transform unit 240 , a prediction unit 250 , a filter unit 260 , and a memory 270 . ) may be included.

The decoding unit 200b of the lower layer includes an entropy decoding unit 211 , a reordering unit 221 , an inverse quantization unit 231 , an inverse transform unit 241 , a prediction unit 251 , a filter unit 261 , and a memory 271 . ) may be included.

When a bitstream including a plurality of layers is transmitted from the encoding apparatus, the DEMUX 280 may demultiplex information for each layer and transmit it to the decoders 200a and 200b for each layer. The input bitstream may be decoded by a procedure opposite to that of the encoding apparatus.

The entropy decoding units 210 and 211 may perform entropy decoding in a procedure opposite to that performed by the entropy encoding unit of the encoding apparatus. Among the information decoded by the entropy decoding units 210 and 211 , information for generating a prediction block is provided to the prediction units 250 and 251 , and the residual value obtained by performing entropy decoding by the entropy decoding units 210 and 211 is a reordering unit. (220, 221) may be input.

The entropy decoders 210 and 211 may use at least one of CABAC and CAVLC like the entropy encoders 160 and 161 .

The entropy decoders 210 and 211 may decode information related to intra prediction and inter prediction performed by the encoding apparatus. The entropy decoders 210 and 211 may include a codeword mapping unit and a codeword mapping table for generating a received codeword as an intra prediction mode number. The codeword mapping table may be stored in advance or may be adaptively generated. When the codenum mapping table is used, a codenum mapping unit for performing codenum mapping may be additionally provided.

The reordering units 220 and 221 may perform rearrangement based on a method in which the encoder rearranges the entropy-decoded bitstream by the entropy decoders 210 and 211 . Coefficients expressed in the form of a one-dimensional vector may be restored and rearranged as coefficients in the form of a two-dimensional block. The reordering units 220 and 221 may receive information related to the coefficient scanning performed by the encoder and perform the reordering through a method of reverse scanning based on the scanning order performed by the corresponding encoder.

The inverse quantizers 230 and 231 may perform inverse quantization based on the quantization parameter provided by the encoding apparatus and the reordered block coefficient values.

The inverse transform units 240 and 241 may perform inverse DCT or inverse DST on the DCT or DST performed by the transforming units 130 and 131 on the quantization result performed by the encoding apparatus. Inverse transform may be performed based on a transmission unit determined by the encoding apparatus. In the transform unit of the encoding apparatus, DCT and DST may be selectively performed according to a plurality of pieces of information, such as a prediction method, the size of the current block, and the prediction direction. Inverse transformation may be performed based on the performed transformation information. When performing the transformation, the transformation may be performed based on the coding block instead of the transformation block.

The prediction units 250 and 251 may generate a prediction block based on the prediction block generation related information provided from the entropy decoders 210 and 211 and previously decoded block or picture information provided from the memories 270 and 271. .

The prediction units 250 and 251 may include a prediction unit determiner, an inter prediction unit, and an intra prediction unit.

The prediction unit determining unit receives various information such as prediction unit information input from the entropy decoder, prediction mode information of the intra prediction method, and motion prediction related information of the inter prediction method, and divides the prediction block from the current coding block, and the prediction block It can be determined whether this inter prediction is performed or whether intra prediction is performed.

The inter prediction unit uses information required for inter prediction of the current prediction block provided by the encoding device to the current prediction block based on information included in at least one of the pictures before or after the current picture including the current prediction block. Inter-screen prediction can be performed for In order to perform inter prediction, a motion prediction method of a prediction block included in a corresponding coding block based on a coding block is a mode (AMVP) using a skip mode, a merge mode, and a motion vector predictor (MVP). Mode), it is possible to determine which method is used.

The intra prediction unit may generate a prediction block based on reconstructed pixel information in the current picture. When the prediction block is a prediction block on which intra prediction is performed, intra prediction may be performed based on intra prediction mode information of the prediction block provided by the encoding apparatus. The in-screen prediction unit is an MDIS filter that filters the reference pixels of the current block, a reference pixel interpolator that interpolates the reference pixels to generate a pixel unit reference pixel with an integer value or less, and filters when the prediction mode of the current block is DC mode. It may include a DC filter that generates a prediction block through .

The prediction unit 250 of the higher layer decoder 200a may further include an inter-layer prediction unit that performs inter-layer prediction for predicting a higher layer using information of a lower layer.

The inter-layer prediction unit may perform inter-layer prediction using intra prediction mode information, motion information, and the like.

Inter-layer prediction may perform prediction of a current block of a higher layer by using a picture of a lower layer as a reference picture and using motion information on a lower layer (reference layer) picture.

A picture of a reference layer used as a reference picture in inter-layer prediction may be a picture sampled to match the resolution of the current layer. Also, the motion information may include a motion vector and a reference index. In this case, the value of the motion vector for the picture of the reference layer may be set to (0, 0).

As an example of inter-layer prediction, a prediction method using a picture of a lower layer as a reference picture has been described, but the present invention is not limited thereto. The inter-layer prediction unit 123 may additionally perform inter-layer texture prediction, inter-layer motion prediction, inter-layer syntax prediction, and inter-layer differential prediction.

Inter-layer texture prediction can derive the texture of the current layer based on the texture of the reference layer. The texture of the reference layer may be sampled according to the resolution of the current layer, and the inter-layer prediction unit may predict the texture of the current layer based on the sampled texture. The inter-layer motion prediction may derive the motion vector of the current layer based on the motion vector of the reference layer. In this case, the motion vector of the reference layer may be scaled to fit the resolution of the current layer. In the inter-layer syntax prediction, the syntax of the current layer may be predicted based on the syntax of the reference layer. For example, the inter-layer prediction unit 123 may use the syntax of the reference layer as the syntax of the current layer. Also, in the inter-layer differential prediction, the picture of the current layer may be reconstructed by using a difference between the reconstructed image of the reference layer and the reconstructed image of the current layer.

The reconstructed block or picture may be provided to the filter units 260 and 261 . The filter units 260 and 261 may include a deblocking filter and an offset correcting unit.

Information on whether a deblocking filter is applied to a corresponding block or picture and information on whether a strong filter or a weak filter is applied when the deblocking filter is applied may be provided from the encoding apparatus. The deblocking filter of the decoding apparatus may receive deblocking filter-related information provided from the encoding apparatus, and the decoding apparatus 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 applied to the image during encoding, offset value information, and the like.

The memories 270 and 271 may store the reconstructed picture or block to be used as a reference picture or reference block, and may also output the reconstructed picture.

The encoding apparatus and the decoding apparatus may perform encoding on three or more layers instead of two layers. In this case, a plurality of encoders for higher layers and decoders for higher layers may be provided corresponding to the number of higher layers. can

In Scalable Video Coding (SVC) that supports a multi-layer structure, there is an association between layers. If prediction is performed using this association, redundant elements of data can be removed and image encoding performance can be improved.

Therefore, when predicting a picture (image) of a current layer (enhancement layer) to be encoded/decoded, inter-prediction or intra-prediction using information of the current layer, as well as inter-layer prediction using information of another layer can be performed. .

When inter-layer prediction is performed, the current layer may generate a prediction sample of the current layer by using a decoded picture of a reference layer used for inter-layer prediction as a reference picture.

At this time, since the current layer and the reference layer may have different at least one of spatial resolution, temporal resolution, and image quality (that is, due to a scalability difference between layers), the decoded reference layer picture is adjusted to match the scalability of the current layer. After resampling is performed, it may be used as a reference picture for inter-layer prediction of the current layer. Resampling refers to up-sampling or down sampling of samples of a reference layer picture to match the picture size of the current layer.

In this specification, the current layer refers to a layer on which encoding or decoding is currently performed, and may be an enhancement layer or an upper layer. The reference layer refers to a layer that the current layer refers to for inter-layer prediction, and may be a base layer or a lower layer. A picture of a reference layer (ie, a reference picture) used for inter-layer prediction of the current layer may be referred to as an inter-layer reference picture or an inter-layer reference picture.

3 is a flowchart illustrating a process of performing inter-layer prediction of a current layer using a reference picture of a reference layer as an embodiment to which the present invention is applied.

Referring to FIG. 3 , filter coefficients of an upsampling filter applied to a reference picture of a reference layer may be obtained ( S300 ).

Here, the reference picture of the reference layer may mean a picture corresponding to the current picture of the current layer for which inter-layer prediction is performed.

Specifically, the reference layer may refer to a base layer or another enhancement layer having a lower resolution than the current layer. The reference picture may mean a picture located in the same time zone as the current picture of the current layer. For example, the corresponding picture may be a picture having the same picture order count (POC) information as the current picture of the current layer.

In addition, the filter coefficients of the upsampling filter may be obtained in consideration of the phase of the reference sample in the reference picture corresponding to the current sample of the current layer. Here, as the upsampling filter, any one of a fixed upsampling filter and an adaptive upsampling filter may be used.

1. Fixed upsampling filter

The fixed upsampling filter may refer to an upsampling filter having predetermined filter coefficients without considering image characteristics. A tap filter may be used as the fixed upsampling filter, and may be defined for a luminance component and a chrominance component, respectively. Hereinafter, a fixed upsampling filter having an accuracy of 1/16 sample unit will be described with reference to Tables 1 and 2.

phase p
Interpolation filter coefficients f[p, 0] f[p, 1] f[p, 2] f[p, 3] f[p, 4] f[p, 5] f[p, 6] f[p, 7] 0 0 0 0 64 0 0 0 0 One 0 One -3 63 4 -2 One 0 2 -One 2 -5 62 8 -3 One 0 3 -One 3 -8 60 13 -4 One 0 4 -One 4 -10 58 17 -5 One 0 5 -One 4 -11 52 26 -8 3 -One 6 -One 3 -3 47 31 -10 4 -One 7 -One 4 -11 45 34 -10 4 -One 8 -One 4 -11 40 40 -11 4 -One 9 -One 4 -10 34 45 -11 4 -One 10 -One 4 -10 31 47 -9 3 -One 11 -One 3 -8 26 52 -11 4 -One 12 0 One -5 17 58 -10 4 -One 13 0 One -4 13 60 -8 3 -One 14 0 One -3 8 62 -5 2 -One 15 0 One -2 4 63 -3 One 0

Table 1 is a table defining filter coefficients of a fixed upsampling filter for a luminance component.

As shown in Table 1 above, in the case of upsampling of the luminance component, an 8-tap filter is applied. That is, interpolation may be performed using the reference sample of the reference layer corresponding to the current sample of the current layer and the neighboring sample adjacent to the reference sample. Here, the neighboring sample may be specified according to a direction in which interpolation is performed. For example, when interpolation is performed in the horizontal direction, the neighboring samples may include three consecutive samples to the left and four consecutive samples to the right with respect to the reference sample. Alternatively, when interpolation is performed in the vertical direction, the neighboring samples may include three consecutive samples at the top and four consecutive samples at the bottom with respect to the reference sample.

And, since interpolation is performed with an accuracy of 1/16 samples, there are a total of 16 phases. This is to support resolutions of various magnifications, such as 2x and 1.5x.

Also, the fixed upsampling filter may use different filter coefficients for each phase p. Except for the case where the phase p is 0, the magnitude of each filter coefficient may be defined to be in the range of 0 to 63. This means that filtering is performed with a precision of 6 bits. Here, when the phase p is 0, in the case of interpolation in units of 1/n samples, it means the position of an integer sample of n multiples.

phase p
Interpolation filter coefficients f[p, 0] f[p, 1] f[p, 2] f[p, 3] 0 0 64 0 0 One -2 62 4 0 2 -2 58 10 -2 3 -4 56 14 -2 4 -4 54 16 -2 5 -6 52 20 -2 6 -6 46 28 -4 7 -4 42 30 -4 8 -4 36 36 -4 9 -4 30 42 -4 10 -4 28 46 -6 11 -2 20 52 -6 12 -2 16 54 -4 13 -2 14 56 -4 14 -2 10 58 -2 15 0 4 62 -2

Table 2 is a table defining filter coefficients of a fixed upsampling filter for a color difference component.

As shown in Table 2, in the case of upsampling for the chrominance component, a 4-tap filter may be applied unlike the luminance component. That is, interpolation may be performed using the reference sample of the reference layer corresponding to the current sample of the current layer and the neighboring sample adjacent to the reference sample. Here, the neighboring sample may be specified according to a direction in which interpolation is performed. For example, when interpolation is performed in the horizontal direction, the neighboring sample may include one continuous sample to the left and two consecutive samples to the right with respect to the reference sample. Alternatively, when interpolation is performed in the vertical direction, the neighboring sample may include one continuous sample at the top and two consecutive samples at the bottom with respect to the reference sample.

Meanwhile, as with the luminance component, since interpolation is performed with an accuracy of 1/16 sample unit, a total of 16 phases exist, and different filter coefficients can be used for each phase p. In addition, the magnitude of each filter coefficient may be defined to be in the range of 0 to 62, except when the phase p is 0. This also means that filtering is performed with a precision of 6 bits.

A case in which an 8-tap filter is applied to a luminance component and a 4-tap filter is applied to a chrominance component has been described above as an example, but the present invention is not limited thereto, and the order of the tap filter can be variably determined in consideration of coding efficiency. of course there is

2. Adaptive upsampling filter

Instead of using fixed filter coefficients, the encoder may determine the optimal filter coefficients in consideration of image characteristics, signal them, and transmit them to the decoder. As described above, using the filter coefficients adaptively determined by the encoder is an adaptive upsampling filter. Since image characteristics are different for each picture, coding efficiency can be improved by using an adaptive upsampling filter that can express image characteristics better than using a fixed upsampling filter in all cases.

(1) Filter coefficient coding method

The encoder may determine the filter coefficients of the adaptive upsampling filter and code them as it is. In this case, the decoder may obtain the filter coefficients from the bitstream through entropy decoding, and apply them to the reference picture to generate the inter-layer reference picture.

Instead of coding the determined filter coefficients as they are, the number of bits required for filter coefficient coding may be reduced through differential coding.

For example, the encoder may determine an optimal filter coefficient for the adaptive upsampling filter for each phase p. The filter coefficient for the i-th phase (p) may be coded as a difference coefficient from the filter coefficient for the (i-1)-th phase (p). Here, when interpolation is performed in units of 1/n samples, since n phases exist, i means a natural number greater than or equal to 1 and less than or equal to (n-1).

Thus, the i-th phase (p _i) if the coded difference between the filter coefficients for the (i-1) th phase (p _(i-1)) the filter coefficients for the decoder is the i-th phase from the bit stream Obtain the differential filter coefficients for (p _i ) and add them to the filter coefficients for the (i-1)-th phase (p _(i-1) ) to derive the filter coefficients for the i-th phase (p _{i )} there is.

Alternatively, the encoder may determine filter coefficients and encoding the difference to the coefficient of the filter coefficients for the i th phase of the up-sampling filter fixing them (p _i) for the i-th phase (p _i).

In this case, the decoder i th phase (p _i) i th phase obtaining the difference filter coefficients, and in addition the filter coefficients for the i th phase of the up-sampling filter fixing them (p _i) for from a bitstream (p _i ) can also be derived for filter coefficients.

However, as described above, when the filter coefficients are coded through the differential coding method, the size of the differential filter coefficients may be limited not to exceed 7. This is to prevent overflow of the temporary buffer from occurring by coding the differential filter coefficients within 3 bits. Meanwhile, the differential filter coefficients may be entropy-coded using a fixed length code or a truncated unary code method.

(2) Transmission unit of filter coefficients

When a separate syntax for the adaptive upsampling filter is defined, it may be obtained from the corresponding syntax (eg, an adaptive parameter set). Alternatively, the encoder may determine filter coefficients commonly applicable to all pictures belonging to an image sequence and transmit them. In this case, the decoder may obtain the filter coefficients of the adaptive upsampling filter in the syntax (eg, sequence parameter set) of the sequence level. Alternatively, the encoder determines the filter coefficients applied in units of pictures or slices, You can also send it. In this case, the decoder may obtain the filter coefficients from the syntax of the picture level or the syntax of the slice level (eg, picture parameter set, slice header, slice segment header). Hereinafter, a method of obtaining filter coefficients of an adaptive upsampling filter in a decoder will be described in detail with reference to FIGS. 4 to 9 .

Referring to FIG. 3 , an interlayer reference picture may be generated by applying the filter coefficients obtained in step S300 to the reference picture ( S310 ).

Specifically, the reference picture may be upsampled by performing interpolation using the obtained filter coefficients. Here, interpolation may be primarily performed in a horizontal direction, and secondarily performed in a vertical direction on a sample generated after interpolation in the horizontal direction.

Inter prediction of the current block may be performed based on the inter-layer reference picture generated in step S310 (S320).

For inter prediction, a reference picture list including inter-layer reference pictures may be generated.

For example, a reference picture list may be constructed using a reference picture belonging to the same layer as the current block, that is, a temporal reference picture, and interlayer reference pictures may be arranged after the temporal reference picture.

Alternatively, an inter-layer reference picture may be added between temporal reference pictures. For example, the interlayer reference picture may be arranged after the first temporal reference picture in a reference picture list composed of temporal reference pictures. The first temporal reference picture in the reference picture list may mean a reference picture having reference index 0. In this case, reference index 1 may be assigned to the inter-layer reference picture arranged after the first temporal reference picture.

Furthermore, a reference picture may be specified in the generated reference picture list by using the reference index of the current block, and a reference block in the reference picture may be specified using a motion vector of the current block. Accordingly, the current block may perform inter prediction using the specified reference block. However, when the current block uses the inter-layer reference picture as the reference picture, the current block may perform inter-layer prediction using a block at the same position in the inter-layer reference picture. To this end, when the reference index of the current block specifies the inter-layer reference picture in the reference picture list, the motion vector of the current block may be set to (0,0).

4 illustrates a method of selectively using an adaptive upsampling filter for a reference picture as an embodiment to which the present invention is applied.

In FIG. 4 , the adaptive upsampling flag adaptive_upsampling_flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter. Although FIG. 4 shows a process of obtaining the filter coefficients at the slice level, it goes without saying that they may be obtained in the same manner at the sequence level and the picture level as shown in FIG. 3 .

Referring to FIG. 4 , an adaptive upsampling flag for a current slice may be obtained ( S400 ).

When the adaptive upsampling flag obtained in step S400 specifies that the adaptive upsampling filter is used, filter coefficients of the adaptive upsampling filter may be obtained ( S410 ).

Specifically, filter coefficients of the adaptive upsampling filter may be obtained for a luminance component and a chrominance component, respectively. Also, filter coefficients may be obtained _{for each phase p i .} For each phase p _i , the filter coefficients of the n-tap filter for the luminance component and the filter coefficients of the m-tap filter for the chrominance component may be obtained, respectively. Here, n and m mean natural numbers greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is an 8-tap filter for a luminance component and a 4-tap filter for a chrominance component, as shown in FIG. 4, the filter coefficients of the 8-tap filter for the luminance component Filter coefficients of the 4-tap filter may be respectively obtained for the gamut and chrominance components.

On the other hand, when the adaptive upsampling flag obtained in step S400 specifies that the fixed upsampling filter is used, the filter coefficients of the adaptive upsampling filter are not obtained from the bitstream, and the predefined table shown in FIG. 3 . Filter coefficients can be obtained from

As such, by using the adaptive upsampling flag, it is possible to selectively use an upsampling filter for the reference picture.

5 illustrates a method of selectively using an adaptive upsampling filter for each of a luminance component and a chrominance component as an embodiment to which the present invention is applied.

First, an adaptive upsampling luma flag (adaptive_upsampling_luma_flag) may be acquired (S500).

The adaptive upsampling luma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a luminance component of a reference picture.

When the adaptive upsampling luma flag obtained in step S500 specifies that the adaptive upsampling filter is used, filter coefficients applied to the luminance component may be obtained ( S510 ).

Here, the filter coefficients may be obtained _{for each phase p i .} A filter coefficient of an n-tap filter may be obtained for a luminance component for each phase p _{i .} Here, n means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is an 8-tap filter for the luminance component, filter coefficients of the 8-tap filter for the luminance component may be obtained as shown in FIG. 5 .

Conversely, when the adaptive upsampling luma flag obtained in step S500 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

Meanwhile, an adaptive upsampling chroma flag (adaptive_upsampling_chroma_flag) may be obtained (S520).

The adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a color difference component of a reference picture.

When the adaptive upsampling chroma flag obtained in step S520 specifies that the adaptive upsampling filter is used, filter coefficients applied to the color difference component may be obtained (S530).

Here, the filter coefficients may be obtained _{for each phase p i .} A filter coefficient of the m-tap filter for the color difference component may be obtained for each phase p _{i .} Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for a color difference component, filter coefficients of the 4-tap filter may be respectively obtained for a color difference component as shown in FIG. 5 .

Conversely, when the adaptive upsampling chroma flag obtained in step S520 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

6 illustrates a method of selectively using an adaptive upsampling filter for each of a luminance component and two color difference components (Cb and Cr) according to an embodiment to which the present invention is applied.

First, an adaptive upsampling luma flag (adaptive_upsampling_luma_flag) may be acquired ( S600 ).

The adaptive upsampling luma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a luminance component of a reference picture.

When the adaptive upsampling luma flag obtained in step S600 specifies that the adaptive upsampling filter is used, filter coefficients applied to the luminance component may be obtained ( S610 ).

Here, the filter coefficients may be obtained _{for each phase p i .} A filter coefficient of an n-tap filter may be obtained for a luminance component for each phase p _{i .} Here, n means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is an 8-tap filter for the luminance component, filter coefficients of the 8-tap filter for the luminance component may be obtained as shown in FIG. 6 .

Conversely, when the adaptive upsampling luma flag obtained in step S600 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

Meanwhile, the color difference components Cb and Cr may also have different characteristics. Accordingly, instead of determining whether to use the adaptive upsampling filter for all color difference components, whether to use the adaptive upsampling filter for each of Cb and Cr may be determined in the encoding step and signaled.

Referring to FIG. 6 , a first adaptive upsampling chroma flag (adaptive_upsampling_Cb_flag) for the current slice may be obtained ( S620 ).

The first adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the color difference component Cb of a reference picture.

When the first adaptive upsampling chroma flag obtained in step S620 specifies that the adaptive upsampling filter is used, filter coefficients applied to the color difference component Cb may be obtained (S630).

Here, the filter coefficients may be obtained _{for each phase p i .} Filter coefficients of the m-tap filter with respect to the color difference component Cb for each phase p _{i may be obtained, respectively.} Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for a chrominance component, filter coefficients of the 4-tap filter may be respectively obtained for the chrominance component Cb as shown in FIG. 6 .

Conversely, when the first adaptive upsampling chroma flag obtained in step S620 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

Then, a second adaptive upsampling chroma flag (adaptive_upsampling_Cr_flag) for the current slice may be acquired (S640).

The second adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component Cr of the reference picture.

When the second adaptive upsampling chroma flag obtained in step S640 specifies that the adaptive upsampling filter is used, filter coefficients applied to the color difference component Cr may be obtained (S650).

Here, the filter coefficients may be obtained _{for each phase p i .} Filter coefficients of the m-tap filter for the chrominance component Cr for each phase p _{i may be obtained, respectively.} Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for the chrominance component Cr, filter coefficients of the 4-tap filter may be respectively obtained for the chrominance component Cr as shown in FIG. 6 .

Conversely, when the second adaptive upsampling chroma flag obtained in step S640 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

7 illustrates a method of obtaining filter coefficients of an adaptive upsampling filter based on a first adaptive component flag as an embodiment to which the present invention is applied.

As shown in FIG. 5 , two flags, that is, an adaptive upsampling luma flag and an adaptive upsampling chroma flag, are used to specify whether the adaptive upsampling filter is used for each of the luminance component and the chrominance component of the reference picture. All have to be coded.

In order to reduce the coding burden, a first adaptive component flag (adaptive_component_flag) may be used. The first adaptive component flag may mean information specifying whether an adaptive upsampling filter is used for at least one of a luminance component and a chrominance component of a reference picture.

If the first adaptive component flag specifies that the adaptive upsampling filter is used for at least one of the luminance component and the chrominance component, the adaptive upsampling luma flag and the adaptive upsampling are performed for each of the luminance component and the chrominance component. You need to acquire the chroma flag.

However, when the first adaptive component flag specifies that the adaptive upsampling filter is not used for both the luminance component and the chrominance component, the adaptive upsampling luma flag and the adaptive upsampling for each of the luminance component and the chrominance component There is no need to acquire the chroma flag.

Referring to FIG. 7 , a first adaptive component flag adaptive_component_flag for the current slice may be acquired ( S700 ).

When the first adaptive component flag specifies that the adaptive upsampling filter is used for at least one of a luminance component and a chrominance component, an adaptive upsampling luma flag adaptive_upsampling_luma_flag may be obtained ( S710 ).

The adaptive upsampling luma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a luminance component of a reference picture.

When the adaptive upsampling luma flag obtained in step S710 specifies that the adaptive upsampling filter is used, filter coefficients applied to the luminance component may be obtained (S720).

Here, the filter coefficients may be obtained _{for each phase p i .} A filter coefficient of an n-tap filter may be obtained for a luminance component for each phase p _{i .} Here, n means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is an 8-tap filter for the luminance component, filter coefficients of the 8-tap filter for the luminance component may be obtained as shown in FIG. 7 .

Conversely, when the adaptive upsampling luma flag obtained in step S710 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

Meanwhile, when the first adaptive component flag specifies that the adaptive upsampling filter is used for at least one of a luminance component and a chrominance component, an adaptive upsampling chroma flag adaptive_upsampling_chroma_flag may be obtained ( S730 ).

The adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a color difference component of a reference picture.

When the adaptive upsampling chroma flag obtained in step S730 specifies that the adaptive upsampling filter is used, filter coefficients applied to the color difference component may be obtained (S740).

Here, the filter coefficients may be obtained _{for each phase p i .} Filter coefficients of the m-tap filter for the chrominance component for each phase p _{i may be obtained, respectively.} Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for a color difference component, filter coefficients of the 4-tap filter for a color difference component may be respectively obtained as shown in FIG. 7 . Also, although not shown in FIG. 7 , it goes without saying that filter coefficients for the color difference component may be obtained for each of the color difference components Cb and Cr.

Conversely, when the adaptive upsampling chroma flag obtained in step S730 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

8 illustrates a method of obtaining filter coefficients of an adaptive upsampling filter based on a second adaptive component flag as an embodiment to which the present invention is applied.

6 , in order to specify whether the adaptive upsampling filter is used for each of the luminance component and the chrominance component Cb and Cr of the reference picture, three flags, i.e., the adaptive upsampling luma flag, and the first adaptive Both the upsampling chroma flag and the second adaptive upsampling chroma flag must be coded.

In order to reduce the coding burden, a second adaptive component flag (adaptive_component_flag) may be used. The second adaptive component flag may mean information specifying whether an adaptive upsampling filter is used for at least one of a luminance component and a chrominance component Cb and Cr of a reference picture.

If the second adaptive component flag specifies that the adaptive upsampling filter is used for at least one of the luminance component and the chrominance component Cb and Cr, adaptive upsampling luma for each of the luminance component and the chrominance component Cb and Cr It is necessary to obtain a flag and an adaptive upsampling chroma flag.

However, when the second adaptive component flag specifies that the adaptive upsampling filter is not used for both the luminance component and the chrominance components Cb and Cr, the adaptive upsampling luma for each of the luminance component and the chrominance components Cb and Cr There is no need to obtain the flag, the first adaptive upsampling chroma flag and the second adaptive upsampling chroma flag.

Referring to FIG. 8 , a second adaptive component flag (adaptive_component_flag) for a current slice may be acquired ( S800 ).

When the second adaptive component flag specifies that the adaptive upsampling filter is used for at least one of the luminance component and the chrominance component Cb and Cr, an adaptive upsampling luma flag (adaptive_upsampling_luma_flag) may be obtained (S810) .

The adaptive upsampling luma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a luminance component of a reference picture.

When the adaptive upsampling luma flag obtained in step S810 specifies that the adaptive upsampling filter is used, filter coefficients applied to the luminance component may be obtained ( S820 ).

Here, the filter coefficients may be obtained _{for each phase p i .} A filter coefficient of an n-tap filter may be obtained for a luminance component for each phase p _{i .} Here, n means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is an 8-tap filter for the luminance component, filter coefficients of the 8-tap filter for the luminance component may be obtained as shown in FIG. 8 .

Conversely, when the adaptive upsampling luma flag obtained in step S810 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

On the other hand, when the second adaptive component flag specifies that the adaptive upsampling filter is used for at least one of the luminance component and the chrominance component Cb and Cr, the first adaptive upsampling chroma flag (adaptive_upsampling_Cb_flag) for the current slice is set. can be obtained (S830).

The first adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the color difference component Cb of a reference picture.

When the first adaptive upsampling chroma flag obtained in step S830 specifies that the adaptive upsampling filter is used, filter coefficients applied to the color difference component Cb may be obtained (S840).

Here, the filter coefficients may be obtained _{for each phase p i .} Filter coefficients of the m-tap filter with respect to the color difference component Cb for each phase p _{i may be obtained, respectively.} Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for the chrominance component Cb, filter coefficients of the 4-tap filter may be respectively obtained for the chrominance component Cb as shown in FIG. 8 .

Conversely, when the first adaptive upsampling chroma flag obtained in step S830 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

In addition, when the second adaptive component flag specifies that the adaptive upsampling filter is used for at least one of the luminance component and the chrominance component Cb and Cr, a second adaptive upsampling chroma flag (adaptive_upsampling_Cr_flag) for the current slice is set. can be obtained (S850).

The second adaptive upsampling chroma flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for the chrominance component Cr of the reference picture.

When the second adaptive upsampling chroma flag obtained in step S850 specifies that the adaptive upsampling filter is used, filter coefficients applied to the color difference component Cr may be obtained ( S860 ).

Here, the filter coefficients may be obtained _{for each phase p i .} Filter coefficients of the m-tap filter for the chrominance component Cr for each phase p _{i may be obtained, respectively.} Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for the chrominance component Cr, filter coefficients of the 4-tap filter may be respectively obtained for the chrominance component Cr as shown in FIG. 8 .

Conversely, when the second adaptive upsampling chroma flag obtained in step S850 specifies that a fixed upsampling filter is used, filter coefficients may be obtained from the predefined table shown in FIG. 3 .

9 illustrates a method of adaptively obtaining filter coefficients for each phase of a reference sample as an embodiment to which the present invention is applied.

Referring to FIG. 9 , an adaptive upsampling flag (adaptive_upsampling_flag) for the current slice may be acquired ( S900 ).

As described above, the adaptive upsampling flag may mean information specifying whether to use a fixed upsampling filter or an adaptive upsampling filter for a reference picture. However, the filter coefficients are not limited to being obtained at the slice level, and may be obtained at the sequence level and picture level.

When the adaptive upsampling flag obtained in step S900 specifies that the adaptive upsampling filter is used, an adaptive luma phase flag (adaptive_luma_phase_flag) may be obtained (S910).

Here, the adaptive luma phase flag may mean information specifying whether a filter coefficient for the i-th phase applied to the luminance component exists. That is, the presence or absence of filter coefficients applied to the luminance component for each phase may be checked based on the adaptive luma phase flag.

When the adaptive luma phase flag obtained in step S910 specifies that there is a coded filter coefficient for the i-th phase, a filter coefficient applied to the luminance component may be obtained ( S920 ).

Specifically, filter coefficients of the n-tap filter for the corresponding i-th phase may be obtained. Here, n means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is an 8-tap filter for the luminance component, filter coefficients of the 8-tap filter for the luminance component may be obtained as shown in FIG. 9 .

Conversely, when the adaptive luma phase flag obtained in step S910 specifies that coded filter coefficients for the i-th phase do not exist, the filter coefficients for the corresponding i-th phase are not extracted.

Also, when the adaptive upsampling flag obtained in step S900 specifies that the adaptive upsampling filter is used, an adaptive chroma phase flag (adaptive_chroma_phase_flag) may be obtained (S930).

Here, the adaptive chroma phase flag may mean information specifying whether a filter coefficient for the i-th phase applied to the color difference component exists. That is, the presence or absence of filter coefficients applied to the color difference component for each phase may be checked based on the adaptive chroma phase flag.

When the adaptive chroma phase flag obtained in operation S930 specifies that there is a coded filter coefficient for the i-th phase, a filter coefficient applied to the color difference component may be obtained ( S940 ).

Specifically, filter coefficients of the m-tap filter for the corresponding i-th phase may be obtained. Here, m means a natural number greater than 1.

Also, for compatibility with the fixed upsampling filter, a tap filter of the same order as the fixed upsampling filter may be used. For example, when the fixed upsampling filter is a 4-tap filter for a color difference component, filter coefficients of the 4-tap filter may be respectively obtained for the color difference component as shown in FIG. 9 .

Also, filter coefficients may be obtained for each of the color difference components Cb and Cr. However, the present invention is not limited thereto, and filter coefficients equally applied to the color difference components Cb and Cr may be obtained.

On the other hand, when the adaptive chroma phase flag obtained in step S930 specifies that coded filter coefficients for the i-th phase do not exist, the filter coefficients for the i-th phase are not extracted.

Meanwhile, the aforementioned adaptive luma phase flag and adaptive chroma phase flag are not limited to the present embodiment, and may be used in the same manner in the embodiments of FIGS. 4 to 8 .

Claims (15)

obtaining filter coefficients of an upsampling filter applied to a reference picture of a reference layer;
generating an inter-layer reference picture by applying the obtained filter coefficients to the reference picture; and
Including; performing inter prediction on the current block of the current layer based on the generated inter-layer reference picture;
The upsampling filter is composed of a fixed upsampling filter,
The fixed upsampling filter obtains 8-tap filter coefficients for luminance components corresponding to 16 phases (p) in units of 1/16 samples and chrominance components corresponding to 16 phases (p) in units of 1/16 samples. A scalable video signal decoding method, characterized in that each consists of 4-tap filter coefficients for The method of claim 1, wherein the 8-tap filter coefficients for the luminance component are:
When the phase (p) is '0', it has {0, 0, 0, 64, 0, 0, 0, 0},
When the phase (p) is '1', it has {0, 1, -3, 63, 4, -2, 1, 0},
When the phase (p) is '2', it has {-1, 2, -5, 62, 8, -3, 1, 0},
A scalable video signal decoding method, characterized in that when the phase (p) is '3', it has {-1, 3, -8, 60, 13, -4, 1, 0}. The method of claim 1, wherein the 4-tap filter coefficients for the chrominance component are:
If phase (p) is '0', it has {0, 64, 0, 0},
When the phase (p) is '1', it has {-2, 62, 4, 0},
When the phase (p) is '2', it has {-2, 58, 10, -2},
A scalable video signal decoding method, characterized in that when the phase (p) is '3', it has {-4, 54, 16, -2}.
delete delete an entropy decoder for obtaining filter coefficients of an upsampling filter applied to a reference picture of a reference layer; and
A prediction unit that generates an inter-layer reference picture by applying the obtained filter coefficients to the reference picture, and performs inter prediction on the current block of the current layer based on the generated inter-layer reference picture,
The upsampling filter is composed of a fixed upsampling filter,
The fixed upsampling filter obtains 8-tap filter coefficients for luminance components corresponding to 16 phases (p) in units of 1/16 samples and chrominance components corresponding to 16 phases (p) in units of 1/16 samples. A scalable video signal decoding apparatus, characterized in that each of the 4-tap filter coefficients for 7. The method of claim 6,
The 8-tap filter coefficients for the luminance component are,
When the phase (p) is '0', it has {0, 0, 0, 64, 0, 0, 0, 0},
When the phase (p) is '1', it has {0, 1, -3, 63, 4, -2, 1, 0},
When the phase (p) is '2', it has {-1, 2, -5, 62, 8, -3, 1, 0},
A scalable video signal decoding apparatus, characterized in that when the phase (p) is '3', it has {-1, 3, -8, 60, 13, -4, 1, 0}. 7. The method of claim 6,
The 4-tap filter coefficients for the color difference component are,
If phase (p) is '0', it has {0, 64, 0, 0},
When the phase (p) is '1', it has {-2, 62, 4, 0},
If the phase (p) is '2', it has {-2, 58, 10, -2},
A scalable video signal decoding apparatus, characterized in that when the phase (p) is '3', it has {-4, 54, 16, -2}.
delete delete obtaining filter coefficients of an upsampling filter applied to a reference picture of a reference layer;
generating an inter-layer reference picture by applying the obtained filter coefficients to the reference picture; and
Including; performing inter prediction on the current block of the current layer based on the generated inter-layer reference picture;
The upsampling filter is composed of a fixed upsampling filter,
The fixed upsampling filter includes 8-tap filter coefficients for luminance components corresponding to 16 phases (p) in units of 1/16 samples and chrominance components corresponding to 16 phases (p) in units of 1/16 samples. A scalable video signal encoding method, characterized in that each consists of 4-tap filter coefficients for 12. The method of claim 11,
The 8-tap filter coefficients for the luminance component are,
When the phase (p) is '0', it has {0, 0, 0, 64, 0, 0, 0, 0},
When the phase (p) is '1', it has {0, 1, -3, 63, 4, -2, 1, 0},
When the phase (p) is '2', it has {-1, 2, -5, 62, 8, -3, 1, 0},
A scalable video signal encoding method, characterized in that when the phase (p) is '3', it has {-1, 3, -8, 60, 13, -4, 1, 0}. 13. The method of claim 12,
The 4-tap filter coefficients for the color difference component are,
If phase (p) is '0', it has {0, 64, 0, 0},
When the phase (p) is '1', it has {-2, 62, 4, 0},
When the phase (p) is '2', it has {-2, 58, 10, -2},
A scalable video signal encoding method, characterized in that when the phase (p) is '3', it has {-4, 54, 16, -2}.
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