KR20200096385A - A method and an apparatus for processing a video signal using intra mode unification between coding block and transform block - Google Patents

Abstract

The present invention relates to a processing method of a video signal and to a device thereof. More specifically, provided are a video signal processing method encoding or decoding a video signal and a device thereof. According to one embodiment of the present invention, an image decoding method includes a step of determining a prediction mode in the screen of a coding block and a conversion block.

Description

Video signal processing method and device that integrates intra prediction mode between coding block and transform block {A METHOD AND AN APPARATUS FOR PROCESSING A VIDEO SIGNAL USING INTRA MODE UNIFICATION BETWEEN CODING BLOCK AND TRANSFORM BLOCK}

The present invention relates to a video signal processing method and apparatus, and more particularly, to a video signal processing method and apparatus for encoding or decoding a video signal.

Compression coding refers to a series of signal processing techniques for transmitting digitized information through a communication line or storing it in a format suitable for a storage medium. Targets for compression encoding include audio, video, and text, and in particular, a technique for performing compression encoding on an image is referred to as video compression. Compression coding of a video signal is performed by removing redundant information in consideration of spatial correlation, temporal correlation, and probability correlation. However, due to the recent development of various media and data transmission media, a more efficient video signal processing method and apparatus is required.

The present invention has an object to increase the coding efficiency of a video signal.

In order to solve the above problems, an image decoding method according to an embodiment of the present invention includes determining an intra prediction mode of a coding block and a transform block.

According to an embodiment of the present invention, the coding efficiency of a video signal can be improved.

1 is a schematic block diagram of a video signal encoding apparatus according to an embodiment of the present invention.
2 is a schematic block diagram of a video signal decoding apparatus according to an embodiment of the present invention.
3 shows an embodiment in which a coding tree unit is divided into coding units within a picture.
4 shows an embodiment of a method for signaling division of a quad tree and a multi-type tree.
5 illustrates an embodiment of reference samples used for prediction of a current block in an intra prediction mode.
6 shows an embodiment of prediction modes used for intra prediction.
7 is a diagram illustrating a method of applying an intra prediction mode when a coding block is divided into a plurality of transform blocks.
8 shows a method of applying an intra prediction mode in an example in which a coding block is divided into a plurality of transform blocks.
9 shows a method of applying an intra prediction mode in a case where a vertical rectangular coding block is divided into two transform blocks.
10 shows a method of applying an intra prediction mode when a horizontal rectangular coding block is divided into two transform blocks.

The terms used in the present specification have been selected as currently widely used general terms as possible while taking functions of the present invention into consideration, but this may vary according to the intention, custom, or the emergence of new technologies of the skilled person in the art. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meaning will be described in the description of the corresponding invention. Therefore, it is to be noted that terms used in the present specification should be interpreted based on the actual meaning of the term and the entire contents of the present specification, not a simple name of the term.

In the present specification, some terms may be interpreted as follows. Coding can be interpreted as encoding or decoding in some cases. In this specification, an apparatus for generating a video signal bitstream by encoding (encoding) a video signal is referred to as an encoding apparatus or an encoder, and an apparatus for reconstructing a video signal by performing decoding (decoding) of a video signal bitstream is decoding It is referred to as a device or decoder. In addition, in this specification, a video signal processing apparatus is used as a term for a concept including both an encoder and a decoder. Information is a term that includes all values, parameters, coefficients, elements, etc., and the meaning may be interpreted differently in some cases, so the present invention is not limited thereto. The'unit' is used to refer to a basic unit of image processing or a specific position of a picture, and refers to an image area including both a luma component and a chroma component. In addition,'block' refers to an image area including a specific component among luma components and chroma components (ie, Cb and Cr). However, depending on the embodiment, terms such as'unit','block','partition', and'area' may be used interchangeably. In addition, in the present specification, a unit may be used as a concept including all of a coding unit, a prediction unit, and a transform unit. A picture refers to a field or a frame, and the terms may be used interchangeably according to embodiments.

1 is a schematic block diagram of an apparatus for encoding a video signal according to an embodiment of the present invention. Referring to FIG. 1, the encoding apparatus 100 of the present invention includes a transform unit 110, a quantization unit 115, an inverse quantization unit 120, an inverse transform unit 125, a filtering unit 130, and a prediction unit 150. ) And an entropy coding unit 160.

The transform unit 110 converts a residual signal that is a difference between the input video signal and the prediction signal generated by the prediction unit 150 to obtain a transform coefficient value. For example, a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), or a Wavelet Transform may be used. Discrete cosine transform and discrete sine transform are transformed by dividing the input picture signal into a block form. In transformation, coding efficiency may vary depending on the distribution and characteristics of values in the transformation region. The quantization unit 115 quantizes a transform coefficient value output from the transform unit 110.

In order to increase coding efficiency, the picture signal is not coded as it is, but a picture is predicted by using a region already coded through the prediction unit 150, and a residual value between the original picture and the predicted picture is added to the predicted picture to be a reconstructed picture. The method of obtaining is used. In order to prevent mismatches from occurring in the encoder and decoder, information available in the decoder should be used when performing prediction in the encoder. To this end, the encoder performs a process of reconstructing the encoded current block again. The inverse quantization unit 120 inverse quantizes the transform coefficient value, and the inverse transform unit 125 restores the residual value by using the inverse quantization transform coefficient value. Meanwhile, the filtering unit 130 performs a filtering operation to improve the quality and encoding efficiency of the reconstructed picture. For example, a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter may be included. The filtered picture is output or stored in a decoded picture buffer (DPB) 156 to be used as a reference picture.

The prediction unit 150 includes an intra prediction unit 152 and an inter prediction unit 154. The intra prediction unit 152 performs intra prediction within the current picture, and the inter prediction unit 154 predicts the current picture using a reference picture stored in the decoded picture buffer 156. Perform. The intra prediction unit 152 performs intra prediction from reconstructed samples in the current picture, and transmits intra-encoding information to the entropy coding unit 160. The intra encoding information may include at least one of an intra prediction mode, a Most Probable Mode (MPM) flag, and an MPM index. The inter prediction unit 154 may include a motion estimation unit 154a and a motion compensation unit 154b. The motion estimation unit 154a obtains a motion vector value of the current region by referring to a specific region of the reconstructed reference picture. The motion estimation unit 154a transfers motion information (reference picture index, motion vector information, etc.) for the reference region to the entropy coding unit 160. The motion compensation unit 154b performs motion compensation using the motion vector value transmitted from the motion estimation unit 154a. The inter prediction unit 154 transmits inter encoding information including motion information on the reference region to the entropy coding unit 160.

When the above picture prediction is performed, the transform unit 110 obtains a transform coefficient value by transforming a residual value between the original picture and the predicted picture. In this case, the transformation may be performed in units of a specific block within the picture, and the size of the specific block may vary within a preset range. The quantization unit 115 quantizes the transform coefficient values generated by the transform unit 110 and transmits the quantization to the entropy coding unit 160.

The entropy coding unit 160 entropy-codes quantized transform coefficients, intra-encoding information, and inter-encoding information to generate a video signal bitstream. In the entropy coding unit 160, a variable length coding (VLC) method and an arithmetic coding method may be used. The variable length coding (VLC) method converts input symbols into consecutive codewords, and the length of the codeword may be variable. For example, frequently occurring symbols are represented by a short codeword, and infrequently occurring symbols are represented by a long codeword. As a variable length coding scheme, a context-based adaptive variable length coding (CAVLC) scheme may be used. Arithmetic coding converts consecutive data symbols into a single prime number, and arithmetic coding can obtain an optimal decimal bit necessary to represent each symbol. Context-based Adaptive Binary Arithmetic Code (CABAC) may be used as arithmetic coding.

The generated bitstream is encapsulated in a basic unit of a Network Abstraction Layer (NAL) unit. The NAL unit includes a coded integer number of coding tree units. In order to decode a bitstream in a video decoder, the bitstream must first be separated into NAL units, and then each separated NAL unit must be decoded. Meanwhile, information necessary for decoding a video signal bitstream is a high-level set such as a picture parameter set (PPS), a sequence parameter set (SPS), and a video parameter set (VPS). It may be transmitted through RBSP (Raw Byte Sequence Payload).

Meanwhile, the block diagram of FIG. 1 shows the encoding apparatus 100 according to an embodiment of the present invention, and separately displayed blocks show elements of the encoding apparatus 100 by logically distinguishing them. Accordingly, the elements of the encoding apparatus 100 described above may be mounted as one chip or as a plurality of chips according to the design of the device. According to an embodiment, the operation of each element of the encoding apparatus 100 described above may be performed by a processor (not shown).

2 is a schematic block diagram of a video signal decoding apparatus 200 according to an embodiment of the present invention. Referring to FIG. 2, the decoding apparatus 200 of the present invention includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 225, a filtering unit 230, and a prediction unit 250.

The entropy decoding unit 210 entropy-decodes the video signal bitstream, and extracts transform coefficients, intra-encoding information, and inter-encoding information for each region. The inverse quantization unit 220 inverse quantizes the entropy-decoded transform coefficient, and the inverse transform unit 225 restores a residual value using the inverse quantization transform coefficient. The video signal processing apparatus 200 restores the original pixel value by summing the residual value obtained by the inverse transform unit 225 with the predicted value obtained by the prediction unit 250.

Meanwhile, the filtering unit 230 improves image quality by performing filtering on a picture. This may include a deblocking filter for reducing block distortion and/or an adaptive loop filter for removing distortion of an entire picture. The filtered picture is output or stored in the decoded picture buffer (DPB) 256 to be used as a reference picture for the next picture.

The prediction unit 250 includes an intra prediction unit 252 and an inter prediction unit 254. The prediction unit 250 generates a prediction picture by using an encoding type decoded by the entropy decoding unit 210 described above, a transform coefficient for each region, and intra/inter encoding information. In order to reconstruct a current block on which decoding is performed, a current picture including the current block or a decoded area of other pictures may be used. An intra picture or an I picture (or tile/slice) using only the current picture for reconstruction, that is, performing only intra prediction, or a picture capable of performing both intra prediction and inter prediction (or, Tile/slice) is called an inter picture (or tile/slice). In order to predict the sample values of each block among inter-pictures (or tiles/slices), a picture (or tile/slice) using at most one motion vector and a reference picture index is a predictive picture or a P picture (or , Tile/slice), and a picture (or tile/slice) using up to two motion vectors and a reference picture index is referred to as a bi-predictive picture or a B picture (or tile/slice). In other words, a P picture (or tile/slice) uses at most one set of motion information to predict each block, and a B picture (or tile/slice) uses at most two motion information to predict each block. Use a set. Here, the motion information set includes one or more motion vectors and one reference picture index.

The intra prediction unit 252 generates a prediction block using intra encoding information and reconstructed samples in the current picture. As described above, the intra encoding information may include at least one of an intra prediction mode, a Most Probable Mode (MPM) flag, and an MPM index. The intra prediction unit 252 predicts pixel values of the current block by using reconstructed pixels located on the left and/or above of the current block as reference pixels. According to an embodiment, the reference pixels may be pixels adjacent to the left boundary of the current block and/or pixels adjacent to the upper boundary. According to another embodiment, the reference pixels may be adjacent pixels within a predetermined distance from the left boundary of the current block among pixels of the neighboring block of the current block and/or pixels adjacent within a predetermined distance from the upper boundary of the current block. At this time, the neighboring block of the current block is a left (L) block, an upper (A) block, a lower left (BL) block, an upper right (AR) block, or an upper left (Above Left) block. AL) may include at least one of the blocks.

The inter prediction unit 254 generates a prediction block using a reference picture and inter encoding information stored in the decoded picture buffer 256. The inter encoding information may include motion information (reference picture index, motion vector information, etc.) of the current block for the reference block. Inter prediction may include L0 prediction, L1 prediction, and Bi-prediction. L0 prediction means prediction using one reference picture included in the L0 picture list, and L1 prediction means prediction using one reference picture included in the L1 picture list. For this, one set of motion information (eg, a motion vector and a reference picture index) may be required. In the bi-prediction scheme, up to two reference regions may be used, and the two reference regions may exist in the same reference picture or may exist in different pictures. That is, in the bi-prediction method, up to two sets of motion information (for example, a motion vector and a reference picture index) may be used, and two motion vectors may correspond to the same reference picture index or to different reference picture indexes. May correspond. In this case, reference pictures may be displayed (or output) temporally before or after the current picture.

The inter prediction unit 254 may obtain a reference block of the current block using a motion vector and a reference picture index. The reference block exists in a reference picture corresponding to a reference picture index. Also, a pixel value of a block specified by a motion vector or an interpolated value thereof may be used as a predictor of the current block. For motion prediction with pixel accuracy in sub-pel units, for example, an 8-tap interpolation filter for a luma signal and a 4-tap interpolation filter for a chroma signal may be used. However, the interpolation filter for motion prediction in units of subpels is not limited thereto. In this way, the inter prediction unit 254 performs motion compensation for predicting a texture of a current unit from a previously restored picture using motion information.

A reconstructed video picture is generated by adding a prediction value output from the intra prediction unit 252 or the inter prediction unit 254 and a residual value output from the inverse transform unit 225. That is, the video signal decoding apparatus 200 reconstructs the current block by using the prediction block generated by the prediction unit 250 and the residual obtained from the inverse transform unit 225.

Meanwhile, the block diagram of FIG. 2 shows the decoding apparatus 200 according to an embodiment of the present invention, and separately displayed blocks are shown by logically distinguishing elements of the decoding apparatus 200. Therefore, the elements of the decoding apparatus 200 described above may be mounted as one chip or as a plurality of chips according to the design of the device. According to an embodiment, the operation of each element of the decoding apparatus 200 described above may be performed by a processor (not shown).

3 shows an embodiment in which a coding tree unit (CTU) is divided into coding units (CUs) in a picture. In the process of coding a video signal, a picture may be divided into a sequence of coding tree units (CTUs). The coding tree unit is composed of an NXN block of luma samples and two blocks of chroma samples corresponding thereto. The coding tree unit may be divided into a plurality of coding units. The coding unit refers to a basic unit for processing a picture in the above-described video signal processing, that is, intra/inter prediction, transformation, quantization, and/or entropy coding. The size and shape of a coding unit in one picture may not be constant. The coding unit may have a square or rectangular shape. The rectangular coding unit (or rectangular block) includes a vertical coding unit (or vertical block) and a horizontal coding unit (or horizontal block). In this specification, a vertical block is a block having a height greater than a width, and a horizontal block is a block having a width greater than the height. In addition, in the present specification, a non-square block may refer to a rectangular block, but the present invention is not limited thereto.

Referring to FIG. 3, a coding tree unit is first divided into a quad tree (QT) structure. That is, in a quad tree structure, one node having a size of 2NX2N may be divided into four nodes having a size of NXN. In this specification, the quad tree may also be referred to as a quaternary tree. Quad tree partitioning can be performed recursively, and not all nodes need to be partitioned to the same depth.

Meanwhile, a leaf node of the quad tree described above may be further divided into a multi-type tree (MTT) structure. According to an embodiment of the present invention, in a multi-type tree structure, one node may be divided into a horizontal or vertically divided binary (binary) or ternary (ternary) tree structure. That is, in the multi-type tree structure, there are four divisional structures: vertical binary division, horizontal binary division, vertical ternary division, and horizontal ternary division. According to an embodiment of the present invention, both widths and heights of nodes in each tree structure may have a power of 2. For example, in a binary tree (Binary Tree, BT) structure, a node having a size of 2NX2N may be divided into two NX2N nodes by vertical binary division, and divided into two 2NXN nodes by horizontal binary division. In addition, in a ternary tree (TT) structure, a node of 2NX2N size is divided into nodes of (N/2)X2N, NX2N and (N/2)X2N by vertical ternary division, and horizontal binary division 2NX(N/2), 2NXN, and 2NX(N/2) nodes by. This multi-type tree division can be performed recursively.

Leaf nodes of a multi-type tree can be coding units. If the coding unit is not too large for the maximum transform length, the corresponding coding unit is used as a unit of prediction and transformation without further division. Meanwhile, in the aforementioned quad tree and multi-type tree, at least one of the following parameters may be defined in advance or transmitted through RBSP of a higher level set such as PPS, SPS, and VPS. 1) CTU size: the size of the root node of the quad tree, 2) the minimum QT size (MinQtSize): the minimum QT leaf node size allowed, 3) the maximum BT size (MaxBtSize): the maximum BT root node size allowed, 4) Maximum TT size (MaxTtSize): Maximum allowed TT root node size, 5) Maximum MTT depth (MaxMttDepth): Maximum allowed depth of MTT segmentation from leaf nodes of QT, 6) Minimum BT size (MinBtSize): allowed Minimum BT leaf node size, 7) Minimum TT size (MinTtSize): Minimum allowed TT leaf node size.

4 shows an embodiment of a method for signaling division of a quad tree and a multi-type tree. Preset flags may be used to signal the division of the quad tree and multi-type tree described above. 4, a flag'qt_split_flag' indicating whether to divide a quad tree node, a flag'mtt_split_flag' indicating whether to divide a multi-type tree node, and a flag'mtt_split_vertical_flag' indicating a splitting direction of a multi-type tree node. 'Or at least one of a flag'mtt_split_binary_flag' indicating the split shape of the multi-type tree node may be used.

According to an embodiment of the present invention, the coding tree unit is a root node of a quad tree, and may be first divided into a quad tree structure. In the quad tree structure,'qt_split_flag' is signaled for each node'QT_node'. When the value of'qt_split_flag' is 1, the node is divided into 4 square nodes, and when the value of'qt_split_flag' is 0, the node becomes'QT_leaf_node', a leaf node of the quad tree.

Each quad tree leaf node'QT_leaf_node' may be further divided into a multi-type tree structure. In the multi-type tree structure,'mtt_split_flag' is signaled for each node'MTT_node'. When the value of'mtt_split_flag' is 1, the corresponding node is divided into a plurality of rectangular nodes, and when the value of'mtt_split_flag' is 0, the corresponding node becomes'MTT_leaf_node' of the multi-type tree. When the multi-type tree node'MTT_node' is divided into a plurality of rectangular nodes (that is, when the value of'mtt_split_flag' is 1),'mtt_split_vertical_flag' and'mtt_split_binary_flag' for the node'MTT_node' will be additionally signaled I can. When the value of'mtt_split_vertical_flag' is 1, vertical division of the node'MTT_node' is indicated, and when the value of'mtt_split_vertical_flag' is 0, horizontal division of the node'MTT_node' is indicated. In addition, when the value of'mtt_split_binary_flag' is 1, the node'MTT_node' is divided into two rectangular nodes, and when the value of'mtt_split_binary_flag' is 0, the node'MTT_node' is divided into three rectangular nodes.

5 and 6 more specifically illustrate an intra prediction method according to an embodiment of the present invention. As described above, the intra prediction unit predicts pixel values of the current block by using reconstructed pixels located on the left and/or above of the current block as reference pixels.

First, FIG. 5 shows an embodiment of reference samples used for prediction of a current block in an intra prediction mode. According to an embodiment, the reference pixels may be pixels adjacent to the left boundary of the current block and/or pixels adjacent to the upper boundary. As shown in FIG. 5, when the size of the current block is WXH and pixels of a single reference line adjacent to the current block are used for intra prediction, a maximum of 2W+2H+1 located on the left and/or above of the current block Reference pixels can be set using n adjacent pixels. Meanwhile, according to an additional embodiment of the present invention, pixels of multiple reference lines may be used for intra prediction of a current block. The multiple reference line may consist of n lines located within a preset range from the current block. According to an embodiment, when pixels of multiple reference lines are used for intra prediction, separate index information indicating lines to be set as reference pixels may be signaled. When at least some adjacent pixels to be used as reference pixels have not yet been reconstructed, the intra predictor may obtain a reference pixel by performing a reference sample padding process according to a preset rule. Also, the intra prediction unit may perform a reference sample filtering process to reduce an error in intra prediction. That is, reference pixels may be obtained by filtering adjacent pixels and/or pixels obtained by the reference sample padding process. The intra prediction unit predicts the pixels of the current block by using the obtained reference pixels.

Next, FIG. 6 shows an embodiment of prediction modes used for intra prediction. For intra prediction, intra prediction mode information indicating an intra prediction direction may be signaled. The intra prediction mode information indicates any one of a plurality of intra prediction modes constituting the intra prediction mode set. When the current block is an intra prediction block, the decoder receives intra prediction mode information of the current block from the bitstream. The intra prediction unit of the decoder performs intra prediction on the current block based on the extracted intra prediction mode information.

According to an embodiment of the present invention, the intra prediction mode set may include all intra prediction modes (eg, a total of 67 intra prediction modes) used for intra prediction. More specifically, the intra prediction mode set may include a planar mode, a DC mode, and a plurality (eg, 65) angular modes (ie, directional modes). Each intra prediction mode may be indicated through a preset index (ie, an intra prediction mode index). For example, as shown in FIG. 6, intra prediction mode index 0 indicates a planar mode, and intra prediction mode index 1 indicates a DC mode. In addition, intra prediction mode indexes 2 to 66 may indicate different angular modes, respectively. The angle modes indicate different angles within a preset angle range, respectively. For example, the angle mode may indicate an angle within an angle range (ie, a first angle range) between 45 degrees and -135 degrees clockwise. The angular mode may be defined based on the 12 o'clock direction. At this time, the intra prediction mode index 2 indicates a horizontal diagonal (HDIA) mode, the intra prediction mode index 18 indicates a horizontal (HOR) mode, and the intra prediction mode index 34 indicates a diagonal (Diagonal, DIA) mode. A mode is indicated, an intra prediction mode index 50 indicates a vertical (VER) mode, and an intra prediction mode index 66 indicates a vertical diagonal (VDIA) mode.

Meanwhile, the preset angle range may be set differently according to the shape of the current block. For example, when the current block is a rectangular block, a wide-angle mode indicating an angle exceeding 45 degrees or less than -135 degrees clockwise may be additionally used. When the current block is a horizontal block, the angle mode may indicate an angle within an angle range (ie, a second angle range) between (45+offset1) degrees and (-135+offset1) degrees in a clockwise direction. In this case, angle modes 67 to 76 outside the first angle range may be additionally used. In addition, when the current block is a vertical block, the angle mode may indicate an angle within an angle range (ie, a third angle range) between (45-offset2) degrees and (-135-offset2) degrees in a clockwise direction. . In this case, angle modes -10 to -1 out of the first angle range may be additionally used. According to an embodiment of the present invention, values of offset1 and offset2 may be determined differently according to a ratio between the width and height of the rectangular block. Further, offset1 and offset2 may be positive numbers.

According to a further embodiment of the present invention, a plurality of angular modes constituting the intra prediction mode set may include a basic angular mode and an extended angular mode. In this case, the extended angle mode may be determined based on the basic angle mode.

According to an embodiment, the default angle mode is a mode corresponding to an angle used in intra prediction of an existing High Efficiency Video Coding (HEVC) standard, and the extended angle mode corresponds to an angle newly added in intra prediction of the next generation video codec standard. It can be a mode to do. More specifically, the basic angular mode is an intra prediction mode {2, 4, 6, ... , 66}, and the extended angle mode is an intra prediction mode {3, 5, 7, ... , 65} may be an angular mode corresponding to any one of. That is, the extended angle mode may be an angle mode between basic angle modes within the first angle range. Accordingly, the angle indicated by the extended angle mode may be determined based on the angle indicated by the basic angle mode.

According to another embodiment, the basic angle mode is a mode corresponding to an angle within a preset first angle range, and the extended angle mode may be a wide angle mode outside the first angle range. That is, the basic angular mode is the intra prediction mode {2, 3, 4,… , 66}, and the extended angle mode is an intra prediction mode {-10, -9, ... , -1} and {67, 68,… , 76} may be an angular mode corresponding to any one of. The angle indicated by the extended angle mode may be determined as an angle opposite to the angle indicated by the corresponding basic angle mode. Accordingly, the angle indicated by the extended angle mode may be determined based on the angle indicated by the basic angle mode. Meanwhile, the number of expansion angle modes is not limited thereto, and additional expansion angles may be defined according to the size and/or shape of the current block. For example, the extended angle mode is the intra prediction mode {-14, -13,… , -1} and {67, 68,… , 80} may be defined as an angular mode corresponding to any one of. Meanwhile, the total number of intra prediction modes included in the intra prediction mode set may vary according to the configuration of the above-described basic angle mode and extended angle mode.

In the above embodiments, the spacing between the extended angle modes may be set based on the spacing between the corresponding basic angle modes. For example, extended angle modes {3, 5, 7,… , 65} the spacing between the corresponding basic angular modes {2, 4, 6,… , 66} can be determined based on the interval. Also, the extended angle modes {-10, -9,… , -1} the spacing between the corresponding opposite basic angular modes {56, 57,… , 65}, determined based on the spacing between the extended angle modes {67, 68, ... , 76} the spacing between the corresponding opposite basic angular modes {3, 4,… , 12} may be determined based on the interval. The angular interval between the extended angle modes may be set to be the same as the angular interval between the corresponding basic angular modes. Also, the number of extended angle modes in the intra prediction mode set may be set to be less than or equal to the number of basic angle modes.

According to an embodiment of the present invention, the extended angle mode may be signaled based on the basic angle mode. For example, the wide-angle mode (ie, the extended angle mode) may replace at least one angle mode (ie, the basic angle mode) within the first angle range. The replaced basic angle mode may be an angle mode corresponding to the opposite side of the wide angle mode. That is, the replaced basic angle mode is an angle mode that corresponds to an angle in a direction opposite to the angle indicated by the wide-angle mode or to an angle that differs by a preset offset index from the angle in the opposite direction. According to an embodiment of the present invention, the preset offset index is 1. The intra prediction mode index corresponding to the replaced basic angular mode may be remapped to the wide-angle mode to signal the corresponding wide-angle mode. For example, wide-angle mode {-10, -9,… , -1} is the intra prediction mode index {57, 58, ... , 66}, each can be signaled by the wide-angle mode {67, 68, ... , 76} is an intra prediction mode index {2, 3, ... , 11}, respectively. In this way, since the intra prediction mode index for the basic angular mode signals the extended angular mode, the intra prediction mode indices of the same set are applied to the signaling of the intra prediction mode even if the configurations of the angular modes used for intra prediction of each block are different. Can be used. Accordingly, signaling overhead due to a change in the intra prediction mode configuration can be minimized.

Meanwhile, whether to use the extended angle mode may be determined based on at least one of the shape and size of the current block. According to an embodiment, when the size of the current block is larger than a preset size, the extended angle mode is used for intra prediction of the current block, otherwise, only the basic angle mode may be used for intra prediction of the current block. According to another embodiment, when the current block is a non-square block, the extended angle mode is used for intra prediction of the current block, and when the current block is a square block, only the basic angle mode may be used for intra prediction of the current block.

The intra prediction unit determines reference pixels and/or interpolated reference pixels to be used for intra prediction of the current block, based on intra prediction mode information of the current block. When the intra prediction mode index indicates a specific angular mode, a reference pixel corresponding to the specific angle from the current pixel of the current block or an interpolated reference pixel is used for prediction of the current pixel. Accordingly, different sets of reference pixels and/or interpolated reference pixels may be used for intra prediction according to the intra prediction mode. After intra prediction of the current block is performed using reference pixels and intra prediction mode information, the decoder restores pixel values of the current block by adding the residual signal of the current block obtained from the inverse transform unit with the intra prediction value of the current block.

Variable Description cbWidth: Coding block Width, cbHeight: Coding block Height, tbWidth: Transform block width, tbHeight: Transform block Height

7 is a diagram illustrating a method of applying an intra prediction mode when a coding block is divided into a plurality of transform blocks.

The intra prediction mode may be determined in units of coding units/blocks (hereinafter referred to as blocks). The coding unit/block may be divided into a plurality of transform blocks. The interpretation of the intra prediction mode may vary depending on the type of the coding block. The following is a description of a method of reinterpreting the intra prediction mode in the case of a non-square block. nTbW may be the width of the transform block, and nTbH may be the height of the transform block. whRatio = Abs(Log2(nTbW/nTbH)). Hereinafter, the signaled intra prediction mode is referred to as a first prediction mode and the reinterpreted mode is referred to as a second prediction mode.

First condition: nTbW> nTbH,

Second condition: a mode in which the first intra prediction mode is equal to or greater than 2,

Third condition: If the first intra prediction mode is larger than whRatio >1, it should be smaller than (8+2*whRatio), and if whRatio <1, it should be smaller than 8.

If the above three conditions are satisfied, the variable wideAngle is set to 1 and the second in-screen prediction mode is set to (first in-screen prediction mode + 65).

Fourth condition: nTbH> nTbW,

Condition 5: The prediction mode in the first screen is equal to or less than 66,

Sixth condition: If whRatio> 1 is greater than (60-2*whRatio ), the first intra prediction mode must be greater than (60-2*whRatio ), and whRatio <1 if it is greater than 60.

When all the conditions 4, 5, and 6 are satisfied, the variable wideAngle is set to 1, and the second intra prediction mode is set to (first intra prediction mode-67).

The intra prediction mode can be divided into a basic angle mode and an extended angle mode. The basic angle mode may be angle modes within the range of +/-45 based on the vertical angle mode/horizontal angle mode, and the extended angle modality may be an angle mode exceeding +/-45 degrees based on the same standard. Accordingly, the signaled mode information may use a basic angular mode or an extended angular mode according to the type of the coding block. In the extended angular mode, the number of available modes is determined according to the horizontal-to-vertical/vertical-to-horizontal ratio based on the shape of the coding block. The ratio can be 2:1, 4:1, 8:1, 16:1, etc. For example, the coding block cbWidth x cbHeight determined as the intra prediction mode 2 as shown in FIG. 7-A may be divided into two transform blocks in the horizontal direction as shown in FIG. 7-B. A first transform block having a size of tbWidht_1 x tbHeight_1 has a vertical rectangular block shape because tbWidht_1 is larger than tbHeight_1. At this time, the signaled intra prediction mode 2 may be reinterpreted based on the shape of the first transform block to be changed to an extended angle mode, and becomes (2+65) according to the analysis method, so that the second intra prediction mode is 67 Can be This may prevent the intra prediction mode determined in units of coding blocks from being used equally in units of transform blocks. This can also lead to performance changes. In the method of determining wideAngle to apply the intra prediction mode determined to the coding block to the transform block in the same manner, nTbW and nTbH are set as cbWidth and cbHeight of the coding block.

7 illustrates that the transform block is divided into a vertical rectangular shape, but is not limited thereto. It can be divided into horizontal rectangular and square shapes, or a combination of various shapes.

8 shows a method of applying an intra prediction mode in an example in which a coding block is divided into a plurality of transform blocks. It shows the case where the coding block of Fig. 8-a is divided into the four transform blocks of Fig. 8-b, and if the height and the width of the coding block are the same, the height and width of each of the four transform blocks are the same. The width-to-height ratio of can be all 1. In this case, the first intra prediction mode determined in the coding block may be applied to the first intra prediction mode without a reinterpretation process in the transform block. In another case, if the height and the width of the coding block are different, the width and height of the four transform blocks may be different. In this case, the intra prediction mode determined in the coding block may be applied as it is by applying the reinterpretation method mentioned in FIG. 7.

9 shows a method of applying an intra prediction mode when a vertical rectangular coding block is divided into two transform blocks. In FIG. 9-a, when the coding block is cbWidth <cbHeight, the signaled mode is intra prediction mode 66, but applying the reinterpretation process mentioned in FIG. 7 (66-67), the intra prediction mode is -1 mode. Becomes. 9-B shows a case in which the coding block of FIG. 9-a is divided into two transform blocks. If the width and height of the transform blocks are the same, intra prediction mode 66 is used without reinterpreting the prediction mode. Conversely, when the transform blocks have different widths and sizes, the same intra prediction mode used for the coding block may be applied through a reinterpretation process as in the case of FIG. 9-A. Therefore, in order to apply the prediction mode of the coding block even in the transformed block, variables nTbW and nTbH required for the reinterpretation process are set as the width and height values of the coding block in the same manner as in the method applied in FIG. 7.

10 shows a method of applying an intra prediction mode when a horizontal rectangular coding block is divided into two transform blocks. In FIG. 10-A, the mode signaled in the case of cbWidth> cbHeight for the coding block is the intra prediction mode 2, but applying the reinterpretation process mentioned in FIG. 7 (2 + 65), the second intra prediction mode is It becomes 67. FIG. 10-B shows a case where the coding block of FIG. 10-A is divided into two transform blocks. If the width and height of the transform block are the same, prediction mode 2 in the first screen is applied without reinterpretation. In order to apply the same prediction mode as the coding block, variables nTbW and nTbH required for the reinterpretation process are set as the width and height values of the coding block in the same manner as in the method applied in FIG. 7. In addition, if the ratio between the width and the height of the transform block is the same as the height and the width of the coding block, the same second intra prediction mode may be applied through a reinterpretation process.

Among the intra prediction methods, there is a method of predicting by applying an interpolation filter to a reference sample. As for the interpolation filter, a Cubic filter method and a Gaussian filter method using 4-tap coefficients can be applied. As a method of determining which of the two filter methods is used, there may be a determination method based on whether to use wideAngle and an intra prediction mode. Among them, when a coding block is divided into a plurality of transform blocks as in Figs. 7,8, 9, and 10 in the method of determining the filter type based on wideAngle, the horizontal-to-vertical/vertical-to-horizontal ratios of the coding block and the transform block are different. The variable wideAngle value can be reset from 1 to 0, or the opposite situation, 0 to 1. If the variable wideAngle value is 1, the variable filterFlag is set to 1, for example, a Gaussian filter is used, and if it is 0, a Cubic filter can be used. If the filterFlag value of the coding block and the filterFlag value of the transform block are applied differently, a performance change may be caused accordingly. Accordingly, the same method of setting the filterFlag of the coding block and the transform block can be applied in the same manner as the method of setting the variable wideAngle in the process of reinterpreting the extended angle mode in FIG. 7.

A coding block can be divided into a plurality of transform blocks if at least one of the height and width of the corresponding block is greater than the maximum transform size, and as a method to increase coding efficiency, it can be divided into a plurality of transform blocks regardless of the maximum change size. There is an Intra subpartition (ISP) method.

The first intra prediction mode applied in the above embodiments is not limited to 2 and 66. In addition, the horizontal-to-vertical/vertical-to-horizontal ratio of the coding block and the transform block is not limited to a specific ratio. Also, the number of transform blocks is not limited to two or four. In addition, the proposed method can be applied even when the horizontal to vertical/vertical to horizontal ratio of the coding block and the horizontal to vertical/vertical to horizontal ratio of the transform block are different.

The following is the contents of prediction methods from mode 2 to mode 66 among intra prediction methods.

1.1.1.1.1 Specification of INTRA_ANGULAR2..INTRA_ANGULAR66 intra prediction modes

Inputs to this process are:

the intra prediction mode predModeIntra,

- a variable refIdx specifying the intra prediction reference line index,

- a variable nTbW specifying the transform block width,

- a variable nTbH specifying the transform block height,

- a variable refW specifying the reference samples width,

- a variable refH specifying the reference samples height,

- a variable nCbW specifying the coding block width,

- a variable nCbH specifying the coding block height,

- a variable cIdx specifying the color component of the current block,

the neighboring samples p[　x　][　y　], with x　=　1　refIdx,　y　=　1　refIdx..refH　　1 and x　=　refIdx..refW　y　ref1,

Outputs of this process are the modified intra prediction mode predModeIntra and the predicted samples predSamples[　x　][　y　], with x　=　0..nTbW　　1, y　=　0..nTbH　　1.

The variables new-nTbW and new-nTbH are derived as follows: Can be applied without checking whether sub-partitions are applied in the screen and whether the color component is luma, and can be set as follows.

new-nTbW = nCbW;

new-nTbH = nCbH;

The variable nTbS　is set equal to (　Log2　(　nTbW　)　+　Log2　(　nTbH　)　)　 >> 　1.

The variable whRatio is set equal to Abs(　Log2(　new-nTbW　/　new-nTbH　)　).

The variable wideAngle is set equal to 0.

For non-square blocks (new-nTbW is not equal to new-nTbH), the intra prediction mode predModeIntra is modified as follows:

If all of the following conditions are true, wideAngle is set equal to 1 and predModeIntra is set equal to (　predModeIntra　+　65　).

new-nTbW is greater than new-nTbH

predModeIntra is greater than or equal to 2

predModeIntra is less than (whRatio　>　1 )　　? (　8　+　2　*　whRatio　)　　:　　8

- Otherwise, if all of the following conditions are true, wideAngle is set equal to 1 and predModeIntra is set equal to (　predModeIntra　　67　).

-new-nTbH is greater than new-nTbW

-predModeIntra is less than or equal to 66

predModeIntra is greater than (whRatio　>　1　)　　? (　60　　2　*　whRatio　)　　:　　60

The following is a description of a decoding process for an intra block.

1.1.1.2 General decoding process for intra blocks

Inputs to this process are:

- a sample location (　xTb0,　yTb0　) specifying the top-left sample of the current transform block relative to the top-left sample of the current picture,

- a variable nTbW specifying the width of the current transform block,

- a variable nTbH specifying the height of the current transform block,

- a variable predModeIntra specifying the intra prediction mode,

- a variable cIdx specifying the color component of the current block.

Output of this process is a modified reconstructed picture before in-loop filtering.

The maximum transform block size maxTbSize is derived as follows:

maxTbSize　=　(　cIdx　　=　=　　0　)　? MaxTbSizeY　:　MaxTbSizeY　/　2 (8-71)

The luma sample location is derived as follows:

(　XTbY,　yTbY　)　=　(　cIdx　　=　=　　0　)　? (　XTb0,　yTb0　)　:　(　xTb0　*　2,　yTb0　*　2　) (8-72)

Depending on maxTbSize, the following applies:

- If IntraSubPartSplitType is equal to NO_ISP_SPLIT and nTbW is greater than maxTbSize or nTbH is greater than maxTbSize, the following ordered steps apply.

One. The variables newTbW and newTbH are derived as follows:

newTbW　=　(　nTbW　　>　　maxTbSize　)　? (　NTbW　/　2　)　:　nTbW (8-73)

newTbH　=　(　nTbH　　 >　　maxTbSize　)　? (　NTbH　/　2　)　:　 nTbH (8-74)

2. The general decoding process for intra blocks as specified in this clause is invoked with the location (　xTb0,yTb0　), the transform block width nTbW set equal to newTbW and the height nTbH set equal to newTbH, the intra prediction mode predModeIntra, and the variable cIdx as inputs, and the output is a modified reconstructed picture before in-loop filtering.

3. If nTbW is greater than maxTbSize, the general decoding process for intra blocks as specified in this clause is invoked with the location (　xTb0,　yTb0　) set equal to (　xTb0　+　newTbW,　yTb0　), the transform block width nTbW and set equal to new the height nTbH set equal to newTbH, the intra prediction mode predModeIntra, and the variable cIdx as inputs, and the output is a modified reconstructed picture before in-loop filtering.

4. If nTbH is greater than maxTbSize, the general decoding process for intra blocks as specified in this clause is invoked with the location (　xTb0,　yTb0　) set equal to (　xTb0,　yTb0　+　newTbH　), the transform block width nTbW set equal to the height nTbH set equal to newTbH, the intra prediction mode predModeIntra, and the variable cIdx as inputs, and the output is a modified reconstructed picture before in-loop filtering.

5. If nTbW is greater than maxTbSize and nTbH is greater than maxTbSize, the general decoding process for intra blocks as specified in this clause is invoked with the location (　xTb0,　yTb0　) set equal to (　xTb0　+　newTbW,　yTb0　), the transform block width nTbW set equal to newTbW and the height nTbH set equal to newTbH, the intra prediction mode predModeIntra, and the variable cIdx as inputs, and the output is a modified reconstructed picture before in-loop filtering.

- Otherwise, the following ordered steps apply:

-The variables nTbH, nTbW are modifed as follows:

nW　=　IntraSubPartitionsSplitType =　= ISP_VER_SPLIT? nTbW　/　NumIntraSubPartitions: nTbW (8-74)

nH　=　IntraSubPartitionsSplitType =　= ISP_HOR_SPLIT? nTbH　/　NumIntraSubPartitions: nTbH (8-74)

numPartsX　=　IntraSubPartitionsSplitType =　= ISP_VER_SPLIT? NumIntraSubPartitions: 1 (8-74)

numPartsY　=　IntraSubPartitionsSplitType =　= ISP_HOR_SPLIT? NumIntraSubPartitions: 1 (8-74)

-For xPartIdx　=　0..numPartsX and yPartIdx　=　0..numPartsY, the following applies:

One. The general intra sample prediction process as specified in clause　8.3.4.2.1 is invoked with the location (　xTbCmp,　yTbCmp　) set equal to (　xTb0　+　nTbW　*　xPartIdx,　yTb0　 the intraprediction mode, the intraprediction 　n block width nTbW and height nTbH set equal to nW and nH, the coding block width nCbW and height nCbH set equal to nTbW and nTbH, and the variable cIdx as inputs, and the output is an (nTbW)x(nTbH) array predSamples.

2.The scaling and transformation process as specified in clause 8.5.2 is invoked with the luma location (xTbY + nTbW * xPartIdx, yTbY+nTbH*yPartIdx), the variable cIdx, (the transform width nTbW and the transform height nTbH) is changed to (the transform block with nTbW and height nTbH set equal to nW and nH, and/or the coding block width nCbW and height nCbH set equal to nTbW and nTbH) as inputs, and the output is an (nTbW)x(nTbH ) array resSamples.

3. The picture reconstruction process for a color component as specified in clause　8.5.5 is invoked with the transform block location (　xTbComp,yTbComp　) set equal to (　xTb0　+nTbW　*　xPartIdx,yTb0T, the transform block location 　yTb0T, the transform block location(　yTb0Tx+　) the transform block height nTbH can be set as follows instead of the transform block width nTbW and height nTbH set equal to nW and nH,and/or the coding block width nCbW and height nCbH set equal to nTbW and nTbH, the variable cIdx, the (nTbW)x(nTbH) array predSamples, and the (nTbW)x(nTbH) array resSamples as inputs, and the output is a modified reconstructed picture before in-loop filtering.

The above-described embodiments of the present invention can be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

In the case of hardware implementation, the method according to embodiments of the present invention includes one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). , Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, procedure, or function that performs the functions or operations described above. The software code can be stored in a memory and driven by a processor. The memory may be located inside or outside the processor, and data may be exchanged with the processor through various known means.

The above description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be interpreted that the embodiments described above are illustrative in all respects and are not limited. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

100: encoding device 200: decoding device

Claims (1)

Video signal processing apparatus and method.

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