KR20220126232A - Video Coding Method And Apparatus Using Arbitrary Block Partitioning - Google Patents

Abstract

A video coding method and apparatus using arbitrary block partitioning are disclosed. In the present embodiment, a video coding method and apparatus are provided. The method includes: performing transform and inverse transform on a residual signal of an arbitrarily partitioned block when predicting a current block using arbitrary block partitioning; or performing transform and inverse transform on a residual signal corresponding to some pixels adjacent to a partitioning boundary according to an arbitrary partitioning of the current block.

Description

Video Coding Method And Apparatus Using Arbitrary Block Partitioning

The present disclosure relates to a video coding method and apparatus using arbitrary block division.

The content described below merely provides background information related to the present embodiment and does not constitute the prior art.

Since video data has a large amount of data compared to audio data or still image data, it requires a lot of hardware resources including memory to store or transmit itself without compression processing.

Accordingly, in general, when storing or transmitting video data, an encoder is used to compress and store or transmit the video data, and a decoder receives, decompresses, and reproduces the compressed video data. As such a video compression technique, there are H.264/AVC, High Efficiency Video Coding (HEVC), and the like, and Versatile Video Coding (VVC), which improves encoding efficiency by about 30% or more compared to HEVC.

However, as the size, resolution, and frame rate of an image are gradually increasing, and the amount of data to be encoded is increasing accordingly, a new compression technique with higher encoding efficiency and higher image quality improvement than existing compression techniques is required.

In a video encoding and decoding method and apparatus, dividing one block into two or more sub-blocks is defined as block division. In general, in a conventional video codec, when one block is divided into sub-blocks, it is divided into square or rectangular blocks. In this regard, one block may be divided into sub-blocks of any type, which is referred to as arbitrary block division. Depending on the boundary characteristics of objects in a frame constituting a video, arbitrary block division may be more suitable than conventional square or rectangular block division. Therefore, in order to improve encoding efficiency, arbitrary block division needs to be considered.

According to the present disclosure, when predicting a current block using arbitrary block division, transform and inverse transform are performed on residual signals of the randomly divided block, or some pixels adjacent to a division boundary according to arbitrary division of the current block An object of the present invention is to provide a video coding method and apparatus for performing transform and inverse transform on a residual signal corresponding to .

According to an embodiment of the present disclosure, in a method of inverse transforming arbitrary partitioned blocks of a current block performed by a computing device, inverse transforming decoded transform coefficients to generate a restored residual block to do; obtaining random partition information of the current block, wherein the random partition information is information indicating a form in which the current block is divided into the arbitrary partition blocks; determining a relocation area for relocating residual signals of the reconstructed residual block within the current block by using the randomization information; and relocating the residual signal to the rearrangement region.

According to another embodiment of the present disclosure, in an apparatus for inverse block transform for inversely transforming arbitrary partitioned blocks of a current block, an inverse transform unit for generating a reconstructed residual block by inverse transforming decoded transform coefficients ; a division information obtaining unit for obtaining arbitrary division information of the current block, wherein the arbitrary division information is information indicating a form in which the current block is divided into the arbitrary division blocks; a relocation area determining unit for determining a relocation area for relocating residual signals of the reconstructed residual block within the current block by using the randomization information; and a rearrangement unit that rearranges the residual signal in the rearrangement region.

According to another embodiment of the present disclosure, in a method of converting arbitrary partitioned blocks of a current block performed by a computing device, the method comprising: obtaining arbitrary partitioning information of the current block, wherein the arbitrary the division information is information indicating a form in which the current block is divided into the arbitrary divided blocks; determining a transform area to be transformed from the arbitrary division blocks by using the arbitrary division information; generating a residual block by obtaining residual signals of pixels included in the transform region and performing two-dimensional vectorization; and transforming the residual block to generate transformed coefficients of the current block.

As described above, according to the present embodiment, when predicting the current block using arbitrary block division, transform and inverse transform are performed on the residual signal of the randomly divided block, or adjacent to the division boundary according to the arbitrary division of the current block. By providing a video coding method and apparatus for performing transform and inverse transform on a residual signal corresponding to some pixels, there is an effect that it becomes possible to improve coding efficiency to be suitable for frame characteristics constituting a video.

1 is an exemplary block diagram of an image encoding apparatus that can implement techniques of the present disclosure.
2 is a diagram for explaining a method of dividing a block using a QTBTTT structure.
3A and 3B are diagrams illustrating a plurality of intra prediction modes including wide-angle intra prediction modes.
4 is an exemplary diagram of a neighboring block of a current block.
5 is an exemplary block diagram of an image decoding apparatus capable of implementing the techniques of the present disclosure.
6 is an exemplary diagram illustrating arbitrary block division using line segments according to an embodiment of the present disclosure.
7 is an exemplary diagram illustrating mask-based arbitrary block division according to an embodiment of the present disclosure.
8 is a block diagram illustrating a block transformation apparatus for transforming randomly divided blocks according to an embodiment of the present disclosure.
9A to 9D are exemplary views illustrating selection of some pixels of an arbitrary division boundary according to an embodiment of the present disclosure.
10 is an exemplary diagram illustrating acquisition and transformation of some pixels of an arbitrary division boundary according to an embodiment of the present disclosure.
11 is a block diagram illustrating an apparatus for inverse block transform for inversely transforming randomly divided blocks according to an embodiment of the present disclosure.
12 is an exemplary diagram illustrating inverse transformation and rearrangement of some pixels of an arbitrary division boundary according to an embodiment of the present disclosure.
13 is an exemplary diagram illustrating different transformations according to pixel positions of a boundary of an arbitrary division according to another embodiment of the present disclosure.
14 is an exemplary diagram illustrating different inverse transforms according to pixel positions of a boundary of an arbitrary division according to another embodiment of the present disclosure.
15 is a flowchart illustrating a block transform method for transforming randomly divided blocks according to an embodiment of the present disclosure.
16 is a flowchart illustrating a block inverse transform method for inversely transforming randomly divided blocks according to an embodiment of the present disclosure.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in the description of the present embodiments, if it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present embodiments, the detailed description thereof will be omitted.

1 is an exemplary block diagram of an image encoding apparatus that can implement techniques of the present disclosure. Hereinafter, an image encoding apparatus and sub-components of the apparatus will be described with reference to FIG. 1 .

The image encoding apparatus includes a picture division unit 110 , a prediction unit 120 , a subtractor 130 , a transform unit 140 , a quantization unit 145 , a reordering unit 150 , an entropy encoding unit 155 , and an inverse quantization unit. 160 , an inverse transform unit 165 , an adder 170 , a loop filter unit 180 , and a memory 190 may be included.

Each component of the image encoding apparatus may be implemented as hardware or software, or a combination of hardware and software. In addition, the function of each component may be implemented as software and the microprocessor may be implemented to execute the function of software corresponding to each component.

One image (video) is composed of one or more sequences including a plurality of pictures. Each picture is divided into a plurality of regions, and encoding is performed for each region. For example, one picture is divided into one or more tiles and/or slices. Here, one or more tiles may be defined as a tile group. Each tile or/slice is divided into one or more Coding Tree Units (CTUs). And each CTU is divided into one or more CUs (Coding Units) by a tree structure. Information applied to each CU is encoded as a syntax of the CU, and information commonly applied to CUs included in one CTU is encoded as a syntax of the CTU. In addition, information commonly applied to all blocks in one slice is encoded as a syntax of a slice header, and information applied to all blocks constituting one or more pictures is a picture parameter set (PPS) or a picture. encoded in the header. Furthermore, information commonly referenced by a plurality of pictures is encoded in a sequence parameter set (SPS). In addition, information commonly referred to by one or more SPSs is encoded in a video parameter set (VPS). Also, information commonly applied to one tile or tile group may be encoded as a syntax of a tile or tile group header. Syntaxes included in the SPS, PPS, slice header, tile, or tile group header may be referred to as high-level syntax.

The picture divider 110 determines the size of a coding tree unit (CTU). Information on the size of the CTU (CTU size) is encoded as a syntax of the SPS or PPS and transmitted to the video decoding apparatus.

The picture divider 110 divides each picture constituting an image into a plurality of coding tree units (CTUs) having a predetermined size, and then repeatedly divides the CTUs using a tree structure. (recursively) divide. A leaf node in the tree structure becomes a coding unit (CU), which is a basic unit of encoding.

As a tree structure, a quadtree (QT) in which a parent node (or parent node) is divided into four child nodes (or child nodes) of the same size, or a binary tree (BinaryTree) in which a parent node is divided into two child nodes , BT), or a ternary tree (TT) in which a parent node is divided into three child nodes in a 1:2:1 ratio, or a structure in which two or more of these QT structures, BT structures, and TT structures are mixed have. For example, a QuadTree plus BinaryTree (QTBT) structure may be used, or a QuadTree plus BinaryTree TernaryTree (QTBTTT) structure may be used. Here, BTTT may be collectively referred to as a Multiple-Type Tree (MTT).

2 is a diagram for explaining a method of dividing a block using a QTBTTT structure.

As shown in FIG. 2 , the CTU may be first divided into a QT structure. The quadtree splitting may be repeated until the size of a splitting block reaches the minimum block size (MinQTSize) of a leaf node allowed in QT. A first flag (QT_split_flag) indicating whether each node of the QT structure is split into four nodes of a lower layer is encoded by the entropy encoder 155 and signaled to the image decoding apparatus. If the leaf node of the QT is not larger than the maximum block size (MaxBTSize) of the root node allowed in the BT, it may be further divided into any one or more of the BT structure or the TT structure. A plurality of division directions may exist in the BT structure and/or the TT structure. For example, there may be two directions in which the block of the corresponding node is divided horizontally and vertically. As shown in FIG. 2 , when MTT splitting starts, a second flag (mtt_split_flag) indicating whether or not nodes are split, and a flag indicating additional splitting direction (vertical or horizontal) if split and/or split type (Binary) or Ternary) is encoded by the entropy encoder 155 and signaled to the video decoding apparatus.

Alternatively, before encoding the first flag (QT_split_flag) indicating whether each node is split into four nodes of a lower layer, a CU split flag (split_cu_flag) indicating whether the node is split is encoded it might be When the CU split flag (split_cu_flag) value indicates that it is not split, the block of the corresponding node becomes a leaf node in the split tree structure and becomes a coding unit (CU), which is a basic unit of coding. When the CU split flag (split_cu_flag) value indicates to be split, the image encoding apparatus starts encoding from the first flag in the above-described manner.

When QTBT is used as another example of the tree structure, there are two types of splitting the block of the corresponding node into two blocks of the same size horizontally (i.e., symmetric horizontal splitting) and vertically splitting (i.e., symmetric vertical splitting). branches may exist. A split flag (split_flag) indicating whether each node of the BT structure is split into blocks of a lower layer and split type information indicating a split type are encoded by the entropy encoder 155 and transmitted to the image decoding apparatus. On the other hand, there may be additionally a type in which the block of the corresponding node is divided into two blocks having an asymmetric shape. The asymmetric form may include a form in which the block of the corresponding node is divided into two rectangular blocks having a size ratio of 1:3, or a form in which the block of the corresponding node is divided in a diagonal direction.

A CU may have various sizes depending on the QTBT or QTBTTT split from the CTU. Hereinafter, a block corresponding to a CU to be encoded or decoded (ie, a leaf node of QTBTTT) is referred to as a 'current block'. According to the adoption of QTBTTT partitioning, the shape of the current block may be not only a square but also a rectangle.

The prediction unit 120 generates a prediction block by predicting the current block. The prediction unit 120 includes an intra prediction unit 122 and an inter prediction unit 124 .

In general, each of the current blocks in a picture may be predictively coded. In general, the prediction of the current block is performed using an intra prediction technique (using data from the picture containing the current block) or inter prediction technique (using data from a picture coded before the picture containing the current block). can be performed. Inter prediction includes both uni-prediction and bi-prediction.

The intra prediction unit 122 predicts pixels in the current block by using pixels (reference pixels) located around the current block in the current picture including the current block. A plurality of intra prediction modes exist according to a prediction direction. For example, as shown in FIG. 3A , the plurality of intra prediction modes may include two non-directional modes including a planar mode and a DC mode and 65 directional modes. According to each prediction mode, the neighboring pixels to be used and the calculation expression are defined differently.

For efficient directional prediction of a rectangular-shaped current block, directional modes (Nos. 67 to 80 and No. -1 to No. -14 intra prediction modes) shown by dotted arrows in FIG. 3B may be additionally used. These may be referred to as “wide angle intra-prediction modes”. Arrows in FIG. 3B indicate corresponding reference samples used for prediction, not prediction directions. The prediction direction is opposite to the direction indicated by the arrow. The wide-angle intra prediction modes are modes in which a specific directional mode is predicted in the opposite direction without additional bit transmission when the current block is rectangular. In this case, among the wide-angle intra prediction modes, some wide-angle intra prediction modes available for the current block may be determined by the ratio of the width to the height of the rectangular current block. For example, the wide-angle intra prediction modes having an angle smaller than 45 degrees (intra prediction modes 67 to 80) are available when the current block has a rectangular shape with a height smaller than the width, and a wide angle having an angle greater than -135 degrees. The intra prediction modes (intra prediction modes -1 to -14) are available when the current block has a rectangular shape with a width greater than a height.

The intra prediction unit 122 may determine an intra prediction mode to be used for encoding the current block. In some examples, the intra prediction unit 122 may encode the current block using several intra prediction modes and select an appropriate intra prediction mode to use from the tested modes. For example, the intra prediction unit 122 calculates bit rate distortion values using rate-distortion analysis for several tested intra prediction modes, and has the best bit rate distortion characteristics among the tested modes. An intra prediction mode may be selected.

The intra prediction unit 122 selects one intra prediction mode from among a plurality of intra prediction modes, and predicts the current block by using a neighboring pixel (reference pixel) determined according to the selected intra prediction mode and an arithmetic expression. Information on the selected intra prediction mode is encoded by the entropy encoder 155 and transmitted to the image decoding apparatus.

The inter prediction unit 124 generates a prediction block for the current block by using a motion compensation process. The inter prediction unit 124 searches for a block most similar to the current block in the coded and decoded reference picture before the current picture, and generates a prediction block for the current block using the searched block. Then, a motion vector (MV) corresponding to displacement between the current block in the current picture and the prediction block in the reference picture is generated. In general, motion estimation is performed for a luma component, and a motion vector calculated based on the luma component is used for both the luma component and the chroma component. Motion information including information on a reference picture and information on a motion vector used to predict the current block is encoded by the entropy encoder 155 and transmitted to the image decoding apparatus.

The inter prediction unit 124 may perform interpolation on a reference picture or reference block in order to increase prediction accuracy. That is, subsamples between two consecutive integer samples are interpolated by applying filter coefficients to a plurality of consecutive integer samples including the two integer samples. When the process of searching for a block most similar to the current block is performed with respect to the interpolated reference picture, the motion vector may be expressed up to the precision of the decimal unit rather than the precision of the integer sample unit. The precision or resolution of the motion vector may be set differently for each unit of a target region to be encoded, for example, a slice, a tile, a CTU, or a CU. When such adaptive motion vector resolution (AMVR) is applied, information on the motion vector resolution to be applied to each target region should be signaled for each target region. For example, when the target region is a CU, information on motion vector resolution applied to each CU is signaled. The information on the motion vector resolution may be information indicating the precision of a differential motion vector, which will be described later.

Meanwhile, the inter prediction unit 124 may perform inter prediction using bi-prediction. In the case of bidirectional prediction, two reference pictures and two motion vectors indicating the position of a block most similar to the current block in each reference picture are used. The inter prediction unit 124 selects a first reference picture and a second reference picture from the reference picture list 0 (RefPicList0) and the reference picture list 1 (RefPicList1), respectively, and searches for a block similar to the current block in each reference picture. A first reference block and a second reference block are generated. Then, the prediction block for the current block is generated by averaging or weighting the first reference block and the second reference block. In addition, motion information including information on two reference pictures and information on two motion vectors used to predict the current block is transmitted to the encoder 150 . Here, the reference picture list 0 is composed of pictures before the current picture in display order among the restored pictures, and the reference picture list 1 is composed of pictures after the current picture in the display order among the restored pictures. have. However, the present invention is not limited thereto, and in display order, the restored pictures after the current picture may be further included in the reference picture list 0, and conversely, the restored pictures before the current picture are additionally added to the reference picture list 1. may be included.

Various methods may be used to minimize the amount of bits required to encode motion information.

For example, when the reference picture and motion vector of the current block are the same as the reference picture and motion vector of the neighboring block, the motion information of the current block may be transmitted to the image decoding apparatus by encoding information for identifying the neighboring block. This method is called 'merge mode'.

In the merge mode, the inter prediction unit 124 selects a predetermined number of merge candidate blocks (hereinafter, referred to as 'merge candidates') from neighboring blocks of the current block.

As the neighboring blocks for inducing the merge candidate, as shown in FIG. 4 , the left block (A0), the lower left block (A1), the upper block (B0), and the upper right block (B1) adjacent to the current block in the current picture. ), and all or part of the upper left block (A2) may be used. Also, a block located in a reference picture (which may be the same as or different from the reference picture used to predict the current block) other than the current picture in which the current block is located may be used as a merge candidate. For example, a block co-located with the current block in the reference picture or blocks adjacent to the co-located block may be further used as merge candidates. If the number of merge candidates selected by the above-described method is smaller than the preset number, a 0 vector is added to the merge candidates.

The inter prediction unit 124 constructs a merge list including a predetermined number of merge candidates by using these neighboring blocks. A merge candidate to be used as motion information of the current block is selected from among the merge candidates included in the merge list, and merge index information for identifying the selected candidate is generated. The generated merge index information is encoded by the encoder 150 and transmitted to the image decoding apparatus.

The merge skip mode is a special case of the merge mode. After performing quantization, when all transform coefficients for entropy encoding are close to zero, only neighboring block selection information is transmitted without transmission of a residual signal. By using the merge skip mode, it is possible to achieve relatively high encoding efficiency in an image with little motion, a still image, or a screen content image.

Hereinafter, the merge mode and the merge skip mode are collectively referred to as a merge/skip mode.

Another method for encoding motion information is AMVP (Advanced Motion Vector Prediction) mode.

In the AMVP mode, the inter prediction unit 124 derives motion vector prediction candidates for the motion vector of the current block using neighboring blocks of the current block. As neighboring blocks used to derive prediction motion vector candidates, the left block (A0), the lower left block (A1), the upper block (B0), and the upper right block (A0) adjacent to the current block in the current picture shown in FIG. B1), and all or part of the upper left block (A2) may be used. In addition, a block located in a reference picture (which may be the same as or different from the reference picture used to predict the current block) other than the current picture in which the current block is located is used as a neighboring block used to derive prediction motion vector candidates. may be For example, a block co-located with the current block in the reference picture or blocks adjacent to the co-located block may be used. If the number of motion vector candidates is smaller than the preset number by the method described above, 0 vectors are added to the motion vector candidates.

The inter prediction unit 124 derives prediction motion vector candidates by using the motion vectors of the neighboring blocks, and determines a predicted motion vector with respect to the motion vector of the current block by using the prediction motion vector candidates. Then, a differential motion vector is calculated by subtracting the predicted motion vector from the motion vector of the current block.

The prediction motion vector may be obtained by applying a predefined function (eg, a median value, an average value operation, etc.) to the prediction motion vector candidates. In this case, the image decoding apparatus also knows the predefined function. In addition, since the neighboring block used to derive the prediction motion vector candidate is a block that has already been encoded and decoded, the video decoding apparatus already knows the motion vector of the neighboring block. Therefore, the image encoding apparatus does not need to encode information for identifying the prediction motion vector candidate. Accordingly, in this case, information on a differential motion vector and information on a reference picture used to predict the current block are encoded.

Meanwhile, the prediction motion vector may be determined by selecting any one of the prediction motion vector candidates. In this case, information for identifying the selected prediction motion vector candidate is additionally encoded together with information on the differential motion vector and information on the reference picture used to predict the current block.

The subtractor 130 generates a residual block by subtracting the prediction block generated by the intra prediction unit 122 or the inter prediction unit 124 from the current block.

The transform unit 140 transforms the residual signal in the residual block having pixel values in the spatial domain into transform coefficients in the frequency domain. The transform unit 140 may transform the residual signals in the residual block by using the entire size of the residual block as a transform unit, or divide the residual block into a plurality of sub-blocks and use the sub-blocks as transform units to perform transformation. You may. Alternatively, the residual signals may be transformed by dividing the sub-block into two sub-blocks, which are a transform region and a non-transform region, and use only the transform region sub-block as a transform unit. Here, the transform region subblock may be one of two rectangular blocks having a size ratio of 1:1 based on the horizontal axis (or vertical axis). In this case, the flag (cu_sbt_flag) indicating that only the subblock is transformed, the vertical/horizontal information (cu_sbt_horizontal_flag), and/or the position information (cu_sbt_pos_flag) are encoded by the entropy encoder 155 and signaled to the video decoding apparatus. do. Also, the size of the transform region subblock may have a size ratio of 1:3 based on the horizontal axis (or vertical axis). Signaled to the decoding device.

Meanwhile, the transform unit 140 may separately transform the residual block in a horizontal direction and a vertical direction. For transformation, various types of transformation functions or transformation matrices may be used. For example, a pair of transform functions for horizontal transformation and vertical transformation may be defined as a multiple transform set (MTS). The transform unit 140 may select one transform function pair having the best transform efficiency among MTSs and transform the residual blocks in horizontal and vertical directions, respectively. Information (mts_idx) on the transform function pair selected from among MTS is encoded by the entropy encoder 155 and signaled to the image decoding apparatus.

The quantization unit 145 quantizes the transform coefficients output from the transform unit 140 using a quantization parameter, and outputs the quantized transform coefficients to the entropy encoding unit 155 . The quantization unit 145 may directly quantize a related residual block for a certain block or frame without transformation. The quantization unit 145 may apply different quantization coefficients (scaling values) according to positions of the transform coefficients in the transform block. A quantization matrix applied to two-dimensionally arranged quantized transform coefficients may be encoded and signaled to an image decoding apparatus.

The rearrangement unit 150 may rearrange the coefficient values on the quantized residual values.

The reordering unit 150 may change a two-dimensional coefficient array into a one-dimensional coefficient sequence by using coefficient scanning. For example, the reordering unit 150 may output a one-dimensional coefficient sequence by scanning from DC coefficients to coefficients in a high frequency region using a zig-zag scan or a diagonal scan. . A vertical scan for scanning a two-dimensional coefficient array in a column direction and a horizontal scan for scanning a two-dimensional block shape coefficient in a row direction may be used instead of the zig-zag scan according to the size of the transform unit and the intra prediction mode. That is, a scanning method to be used among a zig-zag scan, a diagonal scan, a vertical scan, and a horizontal scan may be determined according to the size of the transform unit and the intra prediction mode.

The entropy encoding unit 155 uses various encoding methods such as Context-based Adaptive Binary Arithmetic Code (CABAC) and Exponential Golomb to convert the one-dimensional quantized transform coefficients output from the reordering unit 150 . A bitstream is created by encoding the sequence.

In addition, the entropy encoder 155 encodes information such as a CTU size, a CU split flag, a QT split flag, an MTT split type, an MTT split direction, etc. related to block splitting, so that the video decoding apparatus divides the block in the same way as the video encoding apparatus. to be able to divide. Also, the entropy encoding unit 155 encodes information on a prediction type indicating whether the current block is encoded by intra prediction or inter prediction, and intra prediction information (ie, intra prediction) according to the prediction type. Mode information) or inter prediction information (information on an encoding mode (merge mode or AMVP mode) of motion information, a merge index in the case of a merge mode, and a reference picture index and information on a differential motion vector in the case of an AMVP mode) is encoded. Also, the entropy encoder 155 encodes information related to quantization, that is, information about a quantization parameter and information about a quantization matrix.

The inverse quantization unit 160 inverse quantizes the quantized transform coefficients output from the quantization unit 145 to generate transform coefficients. The inverse transform unit 165 restores the residual block by transforming the transform coefficients output from the inverse quantization unit 160 from the frequency domain to the spatial domain.

The addition unit 170 restores the current block by adding the reconstructed residual block to the prediction block generated by the prediction unit 120 . Pixels in the reconstructed current block are used as reference pixels when intra-predicting the next block.

The loop filter unit 180 reconstructs pixels to reduce blocking artifacts, ringing artifacts, blurring artifacts, etc. generated due to block-based prediction and transformation/quantization. filter on them. The filter unit 180 may include all or a part of a deblocking filter 182, a sample adaptive offset (SAO) filter 184, and an adaptive loop filter (ALF) 186 as an in-loop filter. .

The deblocking filter 182 filters the boundary between the reconstructed blocks in order to remove a blocking artifact caused by block-by-block encoding/decoding, and the SAO filter 184 and alf 186 deblocking filtering Additional filtering is performed on the captured image. The SAO filter 184 and the alf 186 are filters used to compensate for the difference between the reconstructed pixel and the original pixel caused by lossy coding. The SAO filter 184 improves encoding efficiency as well as subjective image quality by applying an offset in units of CTUs. On the other hand, the ALF 186 performs block-by-block filtering, and compensates for distortion by applying different filters by classifying the edge of the corresponding block and the degree of change. Information on filter coefficients to be used for ALF may be encoded and signaled to an image decoding apparatus.

The restored block filtered through the deblocking filter 182 , the SAO filter 184 , and the ALF 186 is stored in the memory 190 . When all blocks in one picture are reconstructed, the reconstructed picture may be used as a reference picture for inter prediction of blocks in a picture to be encoded later.

5 is an exemplary block diagram of an image decoding apparatus capable of implementing the techniques of the present disclosure. Hereinafter, an image decoding apparatus and sub-components of the apparatus will be described with reference to FIG. 5 .

The image decoding apparatus includes an entropy decoding unit 510, a reordering unit 515, an inverse quantization unit 520, an inverse transform unit 530, a prediction unit 540, an adder 550, a loop filter unit 560, and a memory ( 570) may be included.

Like the image encoding apparatus of FIG. 1 , each component of the image decoding apparatus may be implemented as hardware or software, or a combination of hardware and software. In addition, the function of each component may be implemented as software and the microprocessor may be implemented to execute the function of software corresponding to each component.

The entropy decoding unit 510 decodes the bitstream generated by the image encoding apparatus and extracts information related to block division to determine a current block to be decoded, and prediction information and residual signal required to reconstruct the current block. extract information, etc.

The entropy decoder 510 extracts information on the CTU size from a sequence parameter set (SPS) or a picture parameter set (PPS) to determine the size of the CTU, and divides the picture into CTUs of the determined size. Then, the CTU is determined as the uppermost layer of the tree structure, that is, the root node, and the CTU is divided using the tree structure by extracting division information on the CTU.

For example, when a CTU is split using the QTBTTT structure, a first flag (QT_split_flag) related to QT splitting is first extracted and each node is split into four nodes of a lower layer. And, for the node corresponding to the leaf node of QT, the second flag (MTT_split_flag) related to the split of MTT and the split direction (vertical / horizontal) and / or split type (binary / ternary) information are extracted and the corresponding leaf node is set to MTT split into structures. Accordingly, each node below the leaf node of the QT is recursively divided into a BT or TT structure.

As another example, when a CTU is split using the QTBTTT structure, a CU split flag (split_cu_flag) indicating whether a CU is split is extracted first, and when the block is split, a first flag (QT_split_flag) is extracted. may be In the partitioning process, each node may have zero or more repeated MTT splits after zero or more repeated QT splits. For example, in the CTU, MTT division may occur immediately, or conversely, only multiple QT divisions may occur.

As another example, when a CTU is split using a QTBT structure, a first flag (QT_split_flag) related to QT splitting is extracted and each node is split into four nodes of a lower layer. And, for a node corresponding to a leaf node of QT, a split flag (split_flag) indicating whether to further split into BT and split direction information are extracted.

On the other hand, when the entropy decoding unit 510 determines a current block to be decoded by using the tree structure division, information on a prediction type indicating whether the current block is intra-predicted or inter-predicted is extracted. When the prediction type information indicates intra prediction, the entropy decoder 510 extracts a syntax element for intra prediction information (intra prediction mode) of the current block. When the prediction type information indicates inter prediction, the entropy decoding unit 510 extracts a syntax element for the inter prediction information, that is, information indicating a motion vector and a reference picture referenced by the motion vector.

Also, the entropy decoding unit 510 extracts quantization-related information and information on quantized transform coefficients of the current block as information on the residual signal.

The reordering unit 515 re-orders the sequence of one-dimensional quantized transform coefficients entropy-decoded by the entropy decoding unit 510 in a reverse order of the coefficient scanning order performed by the image encoding apparatus into a two-dimensional coefficient array (that is, block) can be changed.

The inverse quantization unit 520 inversely quantizes the quantized transform coefficients and inversely quantizes the quantized transform coefficients using the quantization parameter. The inverse quantizer 520 may apply different quantization coefficients (scaling values) to the two-dimensionally arranged quantized transform coefficients. The inverse quantizer 520 may perform inverse quantization by applying a matrix of quantization coefficients (scaling values) from the image encoding apparatus to a two-dimensional array of quantized transform coefficients.

The inverse transform unit 530 inversely transforms the inverse quantized transform coefficients from the frequency domain to the spatial domain to reconstruct residual signals to generate a residual block for the current block.

In addition, when the inverse transform unit 530 inversely transforms only a partial region (subblock) of the transform block, a flag (cu_sbt_flag) indicating that only the subblock of the transform block has been transformed, and vertical/horizontal information (cu_sbt_horizontal_flag) of the subblock ) and/or subblock position information (cu_sbt_pos_flag), and by inversely transforming the transform coefficients of the corresponding subblock from the frequency domain to the spatial domain, the residual signals are restored. By filling in , the final residual block for the current block is created.

In addition, when MTS is applied, the inverse transform unit 530 determines a transform function or a transform matrix to be applied in the horizontal and vertical directions, respectively, using the MTS information (mts_idx) signaled from the image encoding apparatus, and uses the determined transform function. Inverse transform is performed on transform coefficients in the transform block in the horizontal and vertical directions.

The predictor 540 may include an intra predictor 542 and an inter predictor 544 . The intra prediction unit 542 is activated when the prediction type of the current block is intra prediction, and the inter prediction unit 544 is activated when the prediction type of the current block is inter prediction.

The intra prediction unit 542 determines the intra prediction mode of the current block from among the plurality of intra prediction modes from the syntax elements for the intra prediction mode extracted from the entropy decoding unit 510, and references the vicinity of the current block according to the intra prediction mode. Predict the current block using pixels.

The inter prediction unit 544 determines a motion vector of the current block and a reference picture referenced by the motion vector by using the syntax element for the inter prediction mode extracted from the entropy decoding unit 510, and divides the motion vector and the reference picture. is used to predict the current block.

The adder 550 reconstructs the current block by adding the residual block output from the inverse transform unit and the prediction block output from the inter prediction unit or the intra prediction unit. Pixels in the reconstructed current block are used as reference pixels when intra-predicting a block to be decoded later.

The loop filter unit 560 may include a deblocking filter 562 , an SAO filter 564 , and an ALF 566 as an in-loop filter. The deblocking filter 562 deblocks and filters the boundary between the reconstructed blocks in order to remove a blocking artifact caused by block-by-block decoding. The SAO filter 564 and the ALF 566 perform additional filtering on the reconstructed block after deblocking filtering in order to compensate for the difference between the reconstructed pixel and the original pixel caused by lossy coding. The filter coefficients of the ALF are determined using information about the filter coefficients decoded from the non-stream.

The restored block filtered through the deblocking filter 562 , the SAO filter 564 , and the ALF 566 is stored in the memory 570 . When all blocks in one picture are reconstructed, the reconstructed picture is used as a reference picture for inter prediction of blocks in a picture to be encoded later.

This embodiment relates to encoding and decoding of an image (video) as described above. In more detail, when predicting the current block using arbitrary block division, transform and inverse transform are performed on residual signals of the randomly divided block, or some pixels adjacent to the division boundary according to the arbitrary division of the current block Provided are a video coding method and apparatus for performing transform and inverse transform on a residual signal corresponding to .

The following embodiments may be applied to the picture divider 110 , the predictor 120 , the transform unit 140 , and the inverse transform unit 165 in the image encoding apparatus. In addition, it may be applied to the inverse transform unit 530 and the prediction unit 540 in the image decoding apparatus.

In the following description, the term 'target block' to be encoded/decoded may be used in the same meaning as the current block or coding unit (CU) as described above, or may mean a partial region of the coding unit. may be

Hereinafter, the division of the target block into sub-blocks of arbitrary types is expressed as arbitrary block partitioning or arbitrary partitioning. In addition, the divided subblocks are expressed as arbitrary partitioned blocks.

I. Arbitrary Block Segmentation Using Line Segments

6 is an exemplary diagram illustrating arbitrary block division using line segments according to an embodiment of the present disclosure.

In the example of FIG. 6 , the current block may be a square or rectangular block. The picture divider 110 in the image encoding apparatus may recursively divide the square or rectangular block into various tree shapes. As described above, the picture divider 110 may divide the current block into lower sub-blocks according to a structure such as a quad tree, a binary tree, or a ternary tree.

In addition, as illustrated in FIG. 6 , the picture dividing unit 110 divides the current block into two different arbitrary divided blocks using a line segment having a specific angle θ and a distance ρ from the origin of the block. can be divided into In this case, the image encoding apparatus may signal the angle and distance from the origin as parameters for representing the line segment to the image decoding apparatus in block units. Alternatively, the image encoding apparatus may signal a specific index value generated by combining an angle and a distance.

Meanwhile, the origin of the block may be a geometrical center. For example, with respect to a square or rectangular block, an intersection point between a straight line dividing a side edge of the block and a straight line vertically bisecting a lower side of the block may be the origin of the block.

Hereinafter, a method and an apparatus for transforming/inverse transforming only a part of residual signals in an arbitrary block-divided block will be described. Also, a method and apparatus for dividing a residual signal in an arbitrary block-divided block into a plurality of residual subblocks and then transforming/inversely transforming them differently for each subblock are also described.

7 is an exemplary diagram illustrating mask-based arbitrary block division according to an embodiment of the present disclosure.

As another embodiment, the picture divider 110 may perform mask-based arbitrary block division. For example, the picture divider 110 may randomly divide the current block by applying different weights according to pixel positions. In the example of FIG. 7 , for example, the weight may have a value of 0 to 8. Also, with respect to pixels in an area adjacent to an arbitrary division line segment, the weight of the pixels may decrease or increase according to a distance from the division line segment. For example, in the case of the upper block, the largest weight of 8 is applied to the pixels near the upper left corner of the current block, the middle weight of 4 is applied to the pixels adjacent to the boundary line, and the pixels near the lower right are applied. By applying 0, which is the smallest weight to , the picture divider 110 may randomly divide the upper block from the current block using the weight. Also, the picture dividing unit 110 may arbitrarily divide the lower block from the current block by applying the weights in reverse.

The reason why different weights are applied based on the randomly divided line segment is because of the statistical property that a large residual signal is generated in pixels adjacent to the randomly divided line segment. Therefore, by using different weights based on the distance from the arbitrary division line segment, boundary deterioration that may occur at the boundary of arbitrary block division can be reduced.

II. Transformation of randomly partitioned blocks

8 is a block diagram illustrating a block transform apparatus for transforming randomly divided blocks according to an embodiment of the present disclosure.

The block transform apparatus according to the present embodiment transforms only a part of residual signals in randomly divided blocks. The block transform apparatus includes all or a part of a partition information obtaining unit 802 , a transform area determining unit 804 , a transform area obtaining unit 806 , and a transforming unit 140 . The partition information acquisition unit 802, the transformation region determiner 804, and the transformation region acquisition unit 806 in the block transformation apparatus correspond to preprocessing steps for transformation, and have been described separately for convenience, but a part of the transformation unit 140 is can be included as Accordingly, the block transform apparatus may be included in the transform unit 140 in the image encoding apparatus.

The division information obtaining unit 802 obtains arbitrary division information of the current block. That is, the partition information obtaining unit 802 may derive or parse information on a form in which the current block is divided into arbitrary partition blocks. Here, the current block is a single square or rectangular block, and arbitrary divided blocks may not be square or rectangular.

As an example, the random division information is information indicating a case in which the current block is divided into two using one line segment. For this type of division, random division information may be signaled from a higher level using one or more syntaxes. The division information obtaining unit 802 may parse the signaled syntax or derive it from the syntax to obtain arbitrary division information. The arbitrary division information may include the angle and distance of the division line segment based on the origin of the current block, as described above. In addition, the arbitrary division information may include one index value combining the reference angle and the distance from the origin of the division line segment.

As another example, the random division information may be information indicating a case in which the current block is divided into two or more divisions using one or more line segments.

Meanwhile, the pixels in the current block may be a residual signal obtained by subtracting a signal predicted by the prediction unit 120 from the original signal.

The transformation region determining unit 804 determines a transformation region to be transformed by using the arbitrary division information. In this case, a transformation region including pixels to be transformed may be determined differently according to the arbitrary division information. That is, the transform region determiner 804 may use pixels predefined according to the division form of the current block as the transform region. Alternatively, the transform region determiner 804 may calculate pixels to be transformed based on a boundary of an arbitrary division. As a result, the transformation region determiner 804 may select pixels located at the boundary of an arbitrary division and pixels spatially adjacent to the boundary among the pixels in the current block as the transformation region.

The transform region obtaining unit 806 generates a residual block by obtaining and vectorizing residual signals of target pixels determined as transform regions. Since the residual block is generated from the transform region, the size of the encoding object block and the size of the residual block may be different. The generated residual block is transmitted to the transform unit 140 .

The transform unit 140 transforms the transferred residual block to generate transformed coefficients of the current block.

Hereinafter, a method of determining a transform region and a method of acquiring pixels in the transform region will be described using the examples of FIGS. 9A to 9D and FIG. 10 .

9A to 9D are exemplary views illustrating selection of some pixels of an arbitrary division boundary according to an embodiment of the present disclosure.

As an embodiment, in the example of FIGS. 9A to 9D , the 16×8 size current block is arbitrarily divided into two triangular blocks by a line segment connecting the lower right and upper left corners.

The example of FIG. 9A shows pixels located at the boundary of arbitrary block division. As in the example of FIG. 9A , the transformation region determiner 804 may select only pixels located at the boundary of an arbitrary division and determine the corresponding pixels as the transformation region. Thereafter, the transform region obtaining unit 806 may vectorize pixels positioned at an arbitrary division boundary. For example, the transform region obtaining unit 806 vectorizes 16 pixels positioned at an arbitrary division boundary into a 1D (1-Dimensional) vector of 16×1 or 1×16, or 4×4, 8×2, or It can be vectorized as a 2D (2-Dimensional) vector of 2×8.

As another embodiment, the transform region determiner 804 may determine the transform region up to the upper, lower, left, and right pixels based on the pixels positioned at the boundary of the arbitrary block division, as shown in the example of FIG. 9B . For example, the transformation region determiner 804 may select pixels located at the boundary of an arbitrary division and pixels located at x+1, x-1, y+1, and y-1 positions based on the boundary as the transformation region. can

Meanwhile, in the example of FIG. 9B , the total number of transformation target pixels included in the transformation region is 44, and includes a factor that is not a multiple of 2. Accordingly, when the target pixels are configured as a 2D vector having a size of 4×11, it may be difficult to connect with components of the existing video coding apparatus.

As another embodiment, the transformation region determiner 804 may set the total number of transformation target pixels included in the transformation region to a number that is easy for transformation, such as a multiple of 8 or 16, as illustrated in FIG. 9C . When selecting specific pixels based on the boundary of arbitrary block division, the transformation region determiner 804 may adjust the number of target pixels so that the number of pixels is suitable for the transformation performed thereafter. For example, in the example of FIG. 9C , the number of target pixels is 48, and the transformation region obtaining unit 806 may vectorize the target pixels into a 2D vector having a size of 16×3 or 8×6.

As described above, when the video coding method and apparatus perform pixel-by-pixel processing, the complexity of memory access and operation may increase. Accordingly, in order to solve these problems, target pixels may be selected in units of sub-blocks. As another embodiment, the transform region determiner 804 may divide the pixels positioned at the boundary of the arbitrary block division into 4×4 sub-block units, as illustrated in FIG. 9D . Thereafter, using a total of four 4×4 blocks, the transform domain obtaining unit 806 may vectorize the 16×4 blocks for transformation.

Also, the transformation region determiner 804 may additionally select target pixels for transformation in units of 8×8 blocks or 16×16 blocks.

10 is an exemplary diagram illustrating acquisition and transformation of some pixels of an arbitrary division boundary according to an embodiment of the present disclosure.

As an embodiment, FIG. 10 is an example in which a 16×8 size current block is arbitrarily divided into two triangular blocks by a line segment connecting the lower right and upper left corners. Meanwhile, as described above, the pixels included in the current block may be a residual signal obtained by subtracting the signal predicted by the predictor 120 from the original signal. Accordingly, FIG. 10 exemplifies a process of transforming the residual signal corresponding to some pixel positions adjacent to the boundary of the arbitrary block division using these two randomly divided triangular blocks.

For the two arbitrarily divided triangular blocks, the transformation region determiner 804 determines pixels located at the arbitrary division boundary and pixels adjacent to the boundary as the transformation region. As in the example of FIG. 10 , for a plurality of pixels adjacent to a line segment connecting the lower right and upper left corners, the transformation region determiner 804 may determine pixels corresponding to a total of four 4×4 blocks as transformation regions. have.

The transform region obtaining unit 806 obtains and vectorizes residual signals of pixel positions in the transform region. As in the example of FIG. 10 , the transform domain obtaining unit 806 2D vectorizes the above-described four 4×4 blocks into one 16×4 residual block, and then converts the generated residual block to the transform unit 140 . can transmit Alternatively, the transform region obtaining unit 806 may 2D vectorize four 4×4 blocks into one 4×16 residual block, and then transmit the generated residual block to the transform unit 140 .

Meanwhile, in the example of FIG. 10 , 2D vectorization is obtained by obtaining residual signals of some pixel positions adjacent to the boundary of an arbitrary division from a current block having a size of 16×8, but the present invention is not limited thereto. For example, the transformation region determining unit 804 and the transformation region obtaining unit 806 are not limited to the positions of some of the pixels described above, but determine transformation regions expanded or reduced to various sizes, and A residual signal may be obtained and 2D vectorized.

The transform unit 140 transforms the transmitted residual signal to generate transform coefficients. In this case, the size of the encoding target block and the size of the residual block to be transformed may be different from each other as described above. For example, as illustrated in FIG. 10 , the size of the target block is 16×8 blocks, but the size of the residual block on which the transformation is performed on the target block is 16×4 blocks, and the size of the encoding target block and the residual block is different. do.

11 is a block diagram illustrating an apparatus for inverse block transform for inversely transforming randomly divided blocks according to an embodiment of the present disclosure.

The block inverse transform apparatus according to the present embodiment inversely transforms only some of the residual signals in arbitrary divided blocks. The block inverse transform apparatus includes all or a part of an inverse transform unit 530 , a partition information acquisition unit 1102 , a relocation area determiner 1104 , and a relocation unit 1106 . The division information acquisition unit 1102, the relocation region determiner 1104, and the rearrangement unit 1106 in the block inverse transformation apparatus correspond to the post-processing steps for inverse transformation, and have been described separately for convenience, but as a part of the inverse transformation unit 530 may be included. Accordingly, the block inverse transform apparatus may be included in the inverse transform unit 530 in the image decoding apparatus.

The inverse transform unit 530 inversely transforms transform coefficients decoded from the bitstream to generate a reconstructed residual block of the current block. In this case, the inverse transform unit 530 may perform inverse transform using a predefined transform method. Alternatively, the inverse transform unit 530 may utilize the inverse transform information signaled for the decoding object block, but may perform the inverse transform using one or more inverse transform schemes among a plurality of inverse transform schemes. Also, as described above , the size of the decoding object block may be different from the size of the inverse-transformed residual block.

The division information obtaining unit 1102 obtains arbitrary division information of the current block. That is, the partition information obtaining unit 1102 may derive or parse information on the form in which the current block is divided into arbitrary partition blocks from the decoded syntax. Here, the current block is a single square or rectangular block, and arbitrary divided blocks may not be square or rectangular.

As an example, the random division information is information indicating a case in which the current block is divided into two using one line segment. The arbitrary division information may include the angle and distance of the division line segment based on the origin of the current block. Alternatively, the arbitrary division information may include one index value combining the reference angle and the distance from the origin of the division line segment.

As another example, the random division information may be information indicating a case in which the current block is divided into two or more divisions using one or more line segments.

The relocation area determining unit 1104 determines a relocation area for relocating the residual signal in the reconstructed residual block in the current block by using the random division information. According to the randomization information, pixels in the current block to which the reconstructed residual signal is rearranged may be selected differently. That is, the rearrangement area determiner 1104 may use pixels predefined according to the division form of the current block as the rearrangement area. Alternatively, the rearrangement area determiner 1104 may calculate the rearranged pixels based on the boundary of the arbitrary division. As a result, the rearrangement area determining unit 1104 determines pixels located at the boundary of an arbitrary division and pixels adjacent to the boundary as the rearrangement area.

The relocation unit 1106 rearranges the restored residual signal in the determined relocation area.

12 is an exemplary diagram illustrating inverse transformation and rearrangement of some pixels of an arbitrary division boundary according to an embodiment of the present disclosure.

As an embodiment, FIG. 12 is an example in which a 16×8 size current block is arbitrarily divided into two triangular blocks by a line segment connecting the lower right and upper left. Also, FIG. 12 illustrates a process of inversely transforming the residual signal corresponding to some pixel positions adjacent to the boundary of the arbitrary block division using these two randomly divided triangular blocks. Meanwhile, the example of FIG. 12 shows a reverse process to the example of FIG. 10, which is a case in which the current block is arbitrarily divided into two triangular blocks.

In the example of FIG. 12 , with respect to a block having a size of 16×4, the inverse transform unit 530 performs an inverse transform to generate a reconstructed residual block. In this case, as described above , the size of the decoding object block may be different from the size of the residual block on which the inverse transform is performed. For example, as illustrated in FIG. 12 , the size of the target block is a 16×8 block, but the size of the residual block on which the inverse transform is performed on the target block is a 16×4 block, and the sizes of the decoding target block and the residual block are different. can do.

When the reconstructed residual block is a part of the pixels in the arbitrarily divided current block, the relocation region determining unit 1104 and the relocating unit 1106 generate the entire residual block of the current block from the reconstructed residual block based on the random division information. In the example of FIG. 12 , the relocation region determining unit 1104 and the relocation unit 1106 rearrange the residual signal in the 16×4 residual block to the boundary of the arbitrary block division, and thus the total residual signal of the 16×8 size current block. create On the other hand, for a pixel position that is not adjacent to an arbitrary division boundary, the rearrangement unit 1106 may set a predefined value. Here, the predefined value may be, for example, 0 (zero). Subsequently, the relocated entire residual signal and the signal predicted by the prediction unit 540 may be added to generate a reconstructed signal of the current block.

Hereinafter, as another embodiment, in transforming/inverse transforming the entire residual signal of the current block using the diagrams of FIGS. 13 and 14, a different transform/inverse transform method is applied according to the pixel position of the boundary of an arbitrary block division. describe

13 is an exemplary diagram illustrating different transformations according to pixel positions of a boundary of an arbitrary division according to another embodiment of the present disclosure.

As an embodiment, FIG. 13 is an example in which a 16×8 size current block is arbitrarily divided into two triangular blocks by a line segment connecting the lower right and upper left corners. Meanwhile, as described above, the pixels included in the current block may be residual signals obtained by subtracting the signal predicted by the prediction unit 120 from the original signal. Accordingly, FIG. 13 exemplifies a process of differently transforming the residual signal according to a pixel position adjacent to the boundary of the arbitrary division using these two randomly divided triangular blocks.

With respect to the two arbitrarily divided triangular blocks, the transform region determiner 804 determines pixels of the arbitrarily divided boundary as the first transform region. Additionally, the transformation region determiner 804 may determine the remaining pixels in the two triangular blocks except for the first transformation region as the second transformation region. As in the example of FIG. 13 , for a plurality of pixels adjacent to a line segment connecting the lower right and upper left corners, the transformation region determiner 804 converts pixels corresponding to a total of four 4×4 blocks to the first transformation region. can be selected Also, the transformation region determiner 804 may select 16×4 pixels excluding the first transformation region, that is, pixels located at a spatially distant distance from the block division boundary as the second transformation region.

The transform region obtaining unit 806 generates subblocks by vectorizing the residual signals of pixel positions in the first transform region and the second transform region. As in the example of FIG. 13 , the transform domain obtaining unit 806 2D vectorizes four 4×4 blocks included in the first transform domain into one 16×4 first residual block, and additionally a second transform domain It is possible to 2D vectorize the four 4x4 blocks included in , into one 16x4 second residual block. The generated first residual block and second residual block, that is, sub-blocks may be transmitted to the transform unit 140 .

The transform unit 140 may generate transform coefficients of the current block by applying a different transform to each of the subblocks.

14 is an exemplary diagram illustrating different inverse transforms according to pixel positions of a boundary of an arbitrary division according to another embodiment of the present disclosure.

As an embodiment, in the example of FIG. 14 , a 16×8 current block is arbitrarily divided into two triangular blocks by a line segment connecting the lower right and upper left. Also, FIG. 14 exemplifies a process of inversely transforming the residual signal differently according to pixel positions adjacent to the boundary of the arbitrary division by using these two arbitrarily divided triangular blocks. On the other hand, the example of FIG. 14 shows a reverse process to the example of FIG. 13, which is a case in which the current block is arbitrarily divided into two triangular blocks.

When there are two subblocks corresponding to the current block, the inverse transform unit 530 generates inversely transformed first and second residual blocks by performing different inverse transforms on each subblock. As in the example of FIG. 14 , when the size of the decoding object block is a 16×8 block, the inverse transform unit 530 performs a different inverse transform on the transform coefficient blocks corresponding to two 16×4 subblocks to perform inverse transform A first residual block and a second residual block are generated. Here, both the first residual block and the second residual block are blocks having a size of 16×4. The first residual block includes a residual signal of a first transform region including a plurality of pixels adjacent to a boundary of an arbitrary block division, and the second residual block includes a residual signal of a second transform region including pixels other than the first transform region. Residual signals are included.

The relocation region determiner 1104 and the relocation unit 1106 rearrange the first residual block and the second residual block based on random division information of the current block, thereby generating an overall residual signal of the current block. As shown in the example of FIG. 14 , the relocation region determiner 1104 and the relocation unit 1106 rearrange the first residual block having a size of 16×4 in the first transform region adjacent to the boundary of the arbitrary block division, and perform a 16×4 first residual block. The size of the second residual block is rearranged in the second transform region. Subsequently, the relocated entire residual signal and the signal predicted by the prediction unit 540 may be added to generate a reconstructed signal of the current block.

Meanwhile, in the examples of FIGS. 13 and 14 , two sub-blocks are used, but the present invention is not limited thereto. As another embodiment, the block transform/inverse transform apparatus divides the current block into two or more subblocks according to a distance from a boundary of arbitrary block division, and then applies different transform/inverse transforms to the divided subblocks. can do. In this case, the size of the sub-blocks divided according to the distance from the boundary of the arbitrary block division may be the same or different. For example, as in the example of FIGS. 13 and 14 , a 16×8 block may be equally divided into two 16×4 subblocks, but as another example, a 16×8 block may be divided into a 16×2 subblock and a 16×8 block. It may be divided into 6 subblocks differently. Alternatively, a 16×8 block may be equally divided into four 16×2 subblocks.

Hereinafter, a method of transforming/inverse transforming arbitrary block-divided blocks performed by the block transform/inverse transform apparatus will be described with reference to FIGS. 15 and 16 .

15 is a flowchart illustrating a block transform method for transforming randomly divided blocks according to an embodiment of the present disclosure.

The block transformation apparatus obtains random division information of the current block (S1500). Here, the random partition information is information indicating a form in which the current block is divided into arbitrary partition blocks.

The block transformation apparatus may derive or parse randomization information by using a syntax signaled from a higher stage. In this case, the current block is a single square or rectangular block, and arbitrary divided blocks may not be square or rectangular.

As an example, the random division information is information indicating a case in which the current block is divided into two using one line segment. The arbitrary division information may include the angle and distance of the division line segment based on the origin of the current block, as described above. Alternatively, the arbitrary division information may include one index value combining the reference angle and the distance from the origin of the division line segment.

Meanwhile, the pixels in the current block may be a residual signal obtained by subtracting a signal predicted by the prediction unit 120 from the original signal.

The block transform apparatus determines a transform region to be transformed from the randomly divided blocks by using the random partition information (S1502). In this case, a transformation region including pixels to be transformed may be determined differently according to the arbitrary division information. That is, the block transformation apparatus may use pixels predefined according to the division form of the current block as the transformation region. Alternatively, the block transform apparatus may calculate pixels to be transformed based on a boundary of an arbitrary division. Consequently, the block transformation apparatus may select pixels located at the boundary of an arbitrary division and pixels spatially adjacent to the boundary among pixels in the current block as the transformation region.

The block transform apparatus generates a residual block by obtaining the residual signals of pixels included in the transform region and performing two-dimensional vectorization (S1504). Since the residual block is generated from the transform domain, the size of the current block and the size of the residual block may be different.

The block transform apparatus transforms the residual block to generate transform coefficients of the current block (S1506).

16 is a flowchart illustrating a block inverse transform method for inversely transforming randomly divided blocks according to an embodiment of the present disclosure.

The block inverse transform apparatus inversely transforms the decoded transform coefficients to generate a reconstructed residual block ( S1600 ). In this case, the block inverse transform apparatus may perform inverse transform using a predefined transform method. Also, as described above , the size of the decoding object block may be different from the size of the inverse-transformed residual block.

The block inverse transform apparatus obtains random partition information of the current block (S1602). Here, the random partition information is information indicating a form in which the current block is divided into arbitrary partition blocks. The block inverse transform device is The syntax can be used to derive or parse randomization information. In this case, the current block is a single square or rectangular block, and arbitrary divided blocks may not be square or rectangular. As an example, the random division information is information indicating a case in which the current block is divided into two using one line segment.

The block inverse transform apparatus determines a relocation area for relocating the residual signal of the reconstructed residual block in the current block by using the random partition information (S1604). According to the randomization information, pixels in the current block to which the reconstructed residual signal is rearranged may be selected differently. That is, the block inverse transform apparatus may use pixels predefined according to the division form of the current block as the rearrangement area. Alternatively, the block inverse transform apparatus may calculate rearranged pixels based on a boundary of an arbitrary division. As a result, the block inverse transform apparatus determines, among pixels in the current block, pixels located at the boundary of an arbitrary division and pixels adjacent to the boundary as the rearrangement area.

The block inverse transform apparatus rearranges the residual signal in the rearrangement region (S1606).

Although it is described that each process is sequentially executed in the flowchart/timing diagram of the present specification, this is merely illustrative of the technical idea of an embodiment of the present disclosure. In other words, one of ordinary skill in the art to which an embodiment of the present disclosure pertains changes the order described in the flowchart/timing diagram within a range that does not deviate from the essential characteristics of an embodiment of the present disclosure, or performs one of each process Since it will be possible to apply various modifications and variations by executing the above process in parallel, the flowchart/timing diagram is not limited to a time-series order.

It should be understood that the exemplary embodiments in the above description may be implemented in many different ways. The functions or methods described in one or more examples may be implemented in hardware, software, firmware, or any combination thereof. It should be understood that the functional components described herein have been labeled "...unit" to particularly further emphasize their implementation independence.

Meanwhile, various functions or methods described in this embodiment may be implemented as instructions stored in a non-transitory recording medium that can be read and executed by one or more processors. The non-transitory recording medium includes, for example, any type of recording device in which data is stored in a form readable by a computer system. For example, the non-transitory recording medium includes a storage medium such as an erasable programmable read only memory (EPROM), a flash drive, an optical drive, a magnetic hard drive, and a solid state drive (SSD).

The above description is merely illustrative of the technical idea of this embodiment, and various modifications and variations will be possible without departing from the essential characteristics of the present embodiment by those of ordinary skill in the art to which this embodiment belongs. Accordingly, the present embodiments are intended to explain rather than limit the technical spirit of the present embodiment, and the scope of the technical spirit of the present embodiment is not limited by these embodiments. The protection scope of this embodiment should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiment.

140: conversion unit
530: inverse transform unit
802: division information acquisition unit
804: transformation region determining unit
806: transformation region acquisition unit
1102: division information acquisition unit
1104: relocation area determining unit
1106: relocation unit

Claims (18)

A method of inverse transforming arbitrary partitioned blocks of a current block, performed by a computing device, comprising:
generating a reconstructed residual block by inverse transforming the decoded transform coefficients;
obtaining random partition information of the current block, wherein the random partition information is information indicating a form in which the current block is divided into the arbitrary partition blocks;
determining a relocation area for relocating residual signals of the reconstructed residual block within the current block by using the randomization information; and
relocating the residual signal to the relocation area
A method of inverse transform comprising a. According to claim 1,
The current block is square or rectangular, and the arbitrary divided blocks are not square and not rectangular. According to claim 1,
The step of generating the restored residual block comprises:
Inverse transform method, characterized in that the size of the current block and the size of the reconstructed residual block are different. According to claim 1,
The step of obtaining the random division information includes:
decrypted A method for inverse transformation, characterized in that the randomization information is derived or parsed using a syntax. According to claim 1,
The random division information is
A method for inverse transformation, characterized in that the current block represents a line segment corresponding to a boundary between arbitrary divided blocks into which the current block is bi-divided. 6. The method of claim 5,
The random division information is
Inverse transformation method, characterized in that it includes the angle and distance of the line segment based on the origin of the current block, or an index value indicating data obtained by combining the angle and distance of the line segment. 6. The method of claim 5,
The step of determining the relocation area comprises:
and determining, among pixels in the current block, pixels located at the boundary and pixels adjacent to the boundary as the rearrangement area. According to claim 1,
The rearrangement step is
The inverse transformation method, characterized in that among the pixels in the current block, the remaining pixels except for the rearrangement area are set to a predefined value. In the block inverse transform apparatus for inversely transforming arbitrary partitioned blocks of a current block,
an inverse transform unit generating a reconstructed residual block by inverse transforming the decoded transform coefficients;
a division information obtaining unit for obtaining arbitrary division information of the current block, wherein the arbitrary division information is information indicating a form in which the current block is divided into the arbitrary division blocks;
a relocation area determining unit for determining a relocation area for relocating residual signals of the reconstructed residual block within the current block by using the randomization information; and
a rearrangement unit that rearranges the residual signal in the rearrangement area
A block inverse transform device comprising a. 10. The method of claim 9,
Inverse block transform apparatus, characterized in that the size of the current block and the size of the reconstructed residual block are different. A method of converting arbitrary partitioned blocks of a current block, performed by a computing device, comprising:
obtaining random partition information of the current block, wherein the random partition information is information indicating a form in which the current block is divided into the arbitrary partition blocks;
determining a transform area to be transformed from the arbitrary division blocks by using the arbitrary division information;
generating a residual block by obtaining residual signals of pixels included in the transform region and performing two-dimensional vectorization; and
generating transform coefficients of the current block by transforming the residual block;
A method of transforming, comprising: 12. The method of claim 11,
The current block is square or rectangular, and the arbitrary divided blocks are not square and not rectangular. 12. The method of claim 11,
The pixel values in the current block are residual signals obtained by subtracting the prediction signal of the current block from the original signal of the current block. 12. The method of claim 11,
The step of obtaining the random division information includes:
A method of transforming, characterized in that the randomization information is derived or parsed using a syntax signaled from a higher stage. 12. The method of claim 11,
The random division information is
A method of transforming, characterized in that the current block represents a line segment corresponding to a boundary between the divided arbitrary divided blocks. 16. The method of claim 15,
The random division information is
A method of transforming, characterized in that it includes the angle and distance of the line segment based on the origin of the current block, or an index value indicating data obtained by combining the angle and distance of the line segment. 16. The method of claim 15,
The step of determining the transformation region comprises:
and determining, among pixels in the current block, pixels located at the boundary and pixels adjacent to the boundary as the transformation region. 12. The method of claim 11,
The step of generating the transform coefficient comprises:
The method of transforming, characterized in that the size of the current block and the size of the residual block are different.

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