KR20230059135A - Video Coding Method And Apparatus Using Various Block Partitioning Structure - Google Patents

Abstract

Disclosed are a video coding method and device using various block division structures. In the present embodiment, in order to improve video coding efficiency and video quality, the video coding method and device use various block division structures based on the width, height, or aspect ratio of the block.

Description

Video coding method and apparatus using various block partitioning structures

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

The contents described below merely provide background information related to the present embodiment and do not constitute 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 processing for compression.

Therefore, when video data is stored or transmitted, an encoder is used to compress and store or transmit the video data, and a decoder receives, decompresses, and reproduces the compressed video data. Examples of such video compression technologies include H.264/AVC, High Efficiency Video Coding (HEVC), and Versatile Video Coding (VVC), which has improved coding efficiency by about 30% or more compared to HEVC.

However, since the size, resolution, and frame rate of video are gradually increasing, and the amount of data to be encoded accordingly increases, a new compression technology with higher encoding efficiency and higher picture quality improvement effect than existing compression technologies is required.

In video encoding/decoding, one picture may be divided into a plurality of Coding Tree Units (CTUs). The CTU is again divided into a plurality of sub-coding units (CUs, Coding Units), which is defined as a block partitioning structure. In this case, the CU is a coding block corresponding to one or more different color components (or luma components and luminance and chrominance components), and corresponding syntax elements elements) is defined as a term encompassing.

A method of dividing one CTU into multiple sub-CUs, in which one square block is divided into 4 lower square blocks using a quad-tree structure there is A method of dividing one square or rectangular block into two horizontally divided sub-blocks or two vertically divided sub-blocks is referred to as a block partitioning method using a binary tree structure. A method of dividing one square or rectangular block into three horizontally divided sub-blocks or three vertically divided sub-blocks is referred to as a block partitioning method using a ternary tree structure. Also, a method of performing block partitioning by combining one or more of a quad tree structure, a binary tree structure, and a ternary tree structure is referred to as a multi-type tree structure.

The block division structure is a technical field that affects the overall video encoding/decoding process, such as basic prediction, transformation, quantization, and entropy encoding/decoding, and greatly affects encoding/decoding performance improvement. Accordingly, in order to improve coding efficiency and image quality, various block division structures need to be considered.

An object of the present disclosure is to provide a video coding method and apparatus using various block division structures based on block width, height, or aspect ratio to improve video coding efficiency and video quality.

According to an embodiment of the present disclosure, in a method of dividing a current block, performed by a video decoding apparatus, decoding a width and a height of the current block and a division flag indicating whether the current block is divided from a bitstream ; Calculating an aspect ratio of the current block from the width and height of the current block, wherein the aspect ratio is a ratio obtained by dividing the width of the current block by the height; checking a value of the split flag, wherein if the split flag is false, checking whether the aspect ratio satisfies a preset first condition and the width and height satisfy a preset second condition; When the aspect ratio satisfies the first condition and the width and height satisfy the second condition, decoding a continuous partition flag indicating application of a sequential quad tree structure from the bitstream; and dividing the current block into sub-blocks using the contiguous quad tree structure when the contiguous partitioning flag is true.

According to another embodiment of the present disclosure, a method of dividing a current block, performed by an image encoding apparatus, includes determining a width and a height of the current block; determining a division flag indicating whether to divide the current block; Calculating an aspect ratio of the current block from the width and height of the current block, wherein the aspect ratio is a ratio obtained by dividing the width of the current block by the height; checking a value of the split flag, wherein if the split flag is false, checking whether the aspect ratio satisfies a preset first condition and the width and height satisfy a preset second condition; determining a continuous division flag indicating application of a sequential quad tree structure when the aspect ratio satisfies the first condition and the width and height satisfy the second condition; splitting the current block into sub-blocks using the contiguous quad tree structure when the contiguous division flag is true; and encoding the width and height of the current block, the split flag, and the continuous split flag.

According to another embodiment of the present disclosure, a computer readable recording medium storing a bitstream generated by an image encoding method, the image encoding method comprising: determining a width and a height of a current block; determining a division flag indicating whether to divide the current block; Calculating an aspect ratio of the current block from the width and height of the current block, wherein the aspect ratio is a ratio obtained by dividing the width of the current block by the height; checking a value of the split flag, wherein if the split flag is false, checking whether the aspect ratio satisfies a preset first condition and the width and height satisfy a preset second condition; determining a continuous division flag indicating application of a sequential quad tree structure when the aspect ratio satisfies the first condition and the width and height satisfy the second condition; splitting the current block into sub-blocks using the contiguous quad tree structure when the contiguous division flag is true; and encoding the width and height of the current block, the division flag, and the continuous division flag.

As described above, according to the present embodiment, it is possible to improve video encoding efficiency and video quality by providing a video coding method and apparatus using various block division structures based on block width, height, or aspect ratio. There is a cancellation effect.

1 is an exemplary block diagram of an image encoding apparatus capable of implementing the techniques of this 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 neighboring blocks of a current block.
5 is an exemplary block diagram of a video decoding apparatus capable of implementing the techniques of this disclosure.
6 is an exemplary diagram illustrating various block divisions according to block division structures.
7A and 7B are exemplary diagrams illustrating a block division structure according to an embodiment of the present disclosure.
8A and 8B are exemplary diagrams illustrating a coding order of divided blocks in a block division structure according to an embodiment of the present disclosure.
9 is an exemplary diagram conceptually illustrating a signaling structure of syntax elements according to a block division structure.
10 is an exemplary diagram conceptually illustrating a signaling structure of syntax elements based on a block division structure according to an embodiment of the present disclosure.
11 is an exemplary diagram conceptually illustrating a signaling structure of syntax elements based on a block division structure according to another embodiment of the present disclosure.

DETAILED DESCRIPTION Some embodiments of the present disclosure are described in detail below with reference to exemplary drawings. In adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present embodiments, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present embodiments, the detailed description will be omitted.

1 is an exemplary block diagram of an image encoding apparatus capable of implementing the techniques of this disclosure. Hereinafter, with reference to the illustration of FIG. 1, an image encoding device and sub-components of the device will be described.

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 rearrangement 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.

Each component of the image encoding device may be implemented as hardware or software, or as a combination of hardware and software. Also, the function of each component may be implemented as software, and the microprocessor may be implemented to execute the software function 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 areas and encoding is performed for each area. For example, one picture is divided into one or more tiles or/and 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 coded as a CU syntax, and information commonly applied to CUs included in one CTU is coded as a CTU syntax. In addition, information commonly applied to all blocks in one slice is coded as syntax of a slice header, and information applied to all blocks constituting one or more pictures is a picture parameter set (PPS) or picture coded in the header. Furthermore, information commonly referred to by a plurality of pictures is coded into a Sequence Parameter Set (SPS). Also, information commonly referred to by one or more SPSs is coded into a video parameter set (VPS). Also, information commonly applied to one tile or tile group may be encoded as syntax of a tile or tile group header. Syntax 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 SPS or PPS syntax and transmitted to the video decoding apparatus.

The picture division unit 110 divides each picture constituting an image into a plurality of Coding Tree Units (CTUs) having a predetermined size, and then iteratively divides the CTUs using a tree structure. Divide (recursively). A leaf node in the tree structure becomes a coding unit (CU), which is a basic unit of encoding.

As a tree structure, a quad tree (QT) in which a parent node (or parent node) is divided into four subnodes (or child nodes) of the same size, or a binary tree (BinaryTree) in which a parent node is divided into two subnodes , BT), or a TernaryTree (TT) in which a parent node is split into three subnodes at a ratio of 1:2:1, or a structure in which two or more of these QT structures, BT structures, and TT structures are mixed. there is. 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 combined to be referred to as MTT (Multiple-Type Tree).

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

As shown in FIG. 2, the CTU may first be divided into QT structures. Quadtree splitting can be repeated until the size of the splitting block reaches the minimum block size (MinQTSize) of leaf nodes allowed by 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 video decoding device. If the leaf node of QT is not larger than the maximum block size (MaxBTSize) of the root node allowed in BT, it may be further divided into either a BT structure or a 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 blocks of the corresponding node are divided horizontally and vertically. As shown in FIG. 2, when MTT splitting starts, a second flag (mtt_split_flag) indicating whether nodes are split, and if split, a flag indicating additional split direction (vertical or horizontal) and/or split type (Binary or Ternary) is encoded by the entropy encoding unit 155 and signaled to the video decoding apparatus.

Alternatively, prior to coding 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 coded. It could be. When the value of the CU split flag (split_cu_flag) 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 encoding. When the value of the CU split flag (split_cu_flag) indicates splitting, the video encoding apparatus starts encoding from the first flag in the above-described manner.

As another example of a tree structure, when QTBT is used, the block of the corresponding node is divided into two blocks of the same size horizontally (i.e., symmetric horizontal splitting) and the type that splits vertically (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 video decoding device. Meanwhile, a type in which a block of a corresponding node is divided into two blocks having an asymmetric shape may additionally exist. 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 may be included.

A CU can 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'. Depending on the adoption of the QTBTTT division, the shape of the current block may be rectangular as well as square.

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

In general, each current block in a picture can be coded predictively. In general, prediction of a current block uses an intra-prediction technique (using data from a picture containing the current block) or an 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 predictor 122 predicts pixels in the current block 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 the 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. Depending on each prediction mode, the neighboring pixels to be used and the arithmetic expression are defined differently.

For efficient directional prediction of the rectangular current block, directional modes (numbers 67 to 80 and -1 to -14 intra prediction modes) indicated by dotted arrows in FIG. 3B may be additionally used. These may be referred to as “wide angle intra-prediction modes”. In FIG. 3B , arrows indicate corresponding reference samples used for prediction and do not indicate prediction directions. The prediction direction is opposite to the direction the arrow is pointing. Wide-angle intra prediction modes are modes that perform prediction in the opposite direction of a specific directional mode without additional bit transmission when the current block is rectangular. At this time, among the wide-angle intra prediction modes, some wide-angle intra prediction modes usable for the current block may be determined by the ratio of the width and height of the rectangular current block. For example, wide-angle intra prediction modes (67 to 80 intra prediction modes) having an angle smaller than 45 degrees are usable when the current block has a rectangular shape with a height smaller than a width, and a wide angle having an angle greater than -135 degrees. Intra prediction modes (-1 to -14 intra prediction modes) are available when the current block has a rectangular shape where the width is greater than the 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 be used from the tested modes. For example, the intra predictor 122 calculates rate-distortion values using rate-distortion analysis for several tested intra-prediction modes, and has the best rate-distortion characteristics among the tested modes. Intra prediction mode can also be selected.

The intra prediction unit 122 selects one intra prediction mode from among a plurality of intra prediction modes, and predicts a current block using neighboring pixels (reference pixels) 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 video decoding apparatus.

The inter prediction unit 124 generates a prediction block for a current block using a motion compensation process. The inter-prediction unit 124 searches for a block most similar to the current block in the encoded and decoded reference picture prior to 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 on 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 reference picture information and motion vector information used to predict the current block is encoded by the entropy encoding unit 155 and transmitted to the video 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 a process of searching for a block most similar to the current block is performed for the interpolated reference picture, the motion vector can be expressed with precision of decimal units instead of integer sample units. 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, tile, CTU, or CU. When such adaptive motion vector resolution (AMVR) is applied, information on motion vector resolution to be applied to each target region must 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. Information on the motion vector resolution may be information indicating the precision of differential motion vectors, which will be described later.

Meanwhile, the inter prediction unit 124 may perform inter prediction using bi-prediction. In the case of bi-directional prediction, two reference pictures and two motion vectors representing positions of blocks most similar to the current block within each reference picture are used. The inter prediction unit 124 selects a first reference picture and a second reference picture from reference picture list 0 (RefPicList0) and reference picture list 1 (RefPicList1), respectively, and searches for a block similar to the current block within each reference picture. A first reference block and a second reference block are generated. Then, a prediction block for the current block is generated by averaging or weighted averaging the first reference block and the second reference block. Further, motion information including information on two reference pictures used to predict the current block and information on two motion vectors is delivered to the encoder 150. Here, reference picture list 0 may include pictures prior to the current picture in display order among restored pictures, and reference picture list 1 may include pictures after the current picture in display order among restored pictures. there is. However, it is not necessarily limited to this, and in order of display, ups and downs pictures subsequent to the current picture may be additionally included in reference picture list 0, and conversely, ups and downs pictures prior to the current picture may be additionally included in reference picture list 1. may also 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 those of the neighboring block, the motion information of the current block can be delivered to the video decoding apparatus by encoding information capable of 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.

Neighboring blocks for deriving merge candidates include a left block (A0), a lower left block (A1), an upper block (B0), and an upper right block (B1) adjacent to the current block in the current picture, as shown in FIG. ), 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 a 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 additionally used as a merge candidate. If the number of merge candidates selected by the method described above is less 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 using these neighboring blocks. Among the merge candidates included in the merge list, a merge candidate to be used as motion information of the current block is selected, 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 video decoding apparatus.

Merge skip mode is a special case of merge mode. After performing quantization, when all transform coefficients for entropy encoding are close to zero, only neighboring block selection information is transmitted without transmitting a residual signal. By using the merge skip mode, it is possible to achieve a relatively high encoding efficiency in low-motion images, still images, screen content images, and the like.

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

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

In the AMVP mode, the inter prediction unit 124 derives predictive motion vector candidates for the motion vector of the current block using neighboring blocks of the current block. Neighboring blocks used to derive predictive motion vector candidates include a left block A0, a lower left block A1, an upper block B0, and an upper right block 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 where the current block is located will be used as a neighboring block used to derive motion vector candidates. may be For example, a collocated block co-located with the current block within the reference picture or blocks adjacent to the collocated block may be used. If the number of motion vector candidates is smaller than the preset number according to the method described above, a 0 vector is added to the motion vector candidates.

The inter-prediction unit 124 derives predicted motion vector candidates using the motion vectors of the neighboring blocks, and determines a predicted motion vector for the motion vector of the current block using the predicted 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 predicted motion vector may be obtained by applying a predefined function (eg, median value, average value operation, etc.) to predicted motion vector candidates. In this case, the video decoding apparatus also knows the predefined function. In addition, since a neighboring block used to derive a predicted motion vector candidate is a block that has already been encoded and decoded, the video decoding apparatus also knows the motion vector of the neighboring block. Therefore, the video encoding apparatus does not need to encode information for identifying a predictive motion vector candidate. Therefore, in this case, information on differential motion vectors and information on reference pictures used to predict the current block are encoded.

Meanwhile, the predicted motion vector may be determined by selecting one of the predicted motion vector candidates. In this case, along with information on differential motion vectors and information on reference pictures used to predict the current block, information for identifying the selected predictive motion vector candidate is additionally encoded.

The subtractor 130 subtracts the prediction block generated by the intra prediction unit 122 or the inter prediction unit 124 from the current block to generate a residual 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 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 subblocks and use the subblocks as a transform unit to perform transformation. You may. Alternatively, the residual signals may be divided into two subblocks, a transform region and a non-transform region, and transform the residual signals using only the transform region subblock as a transform unit. Here, the transformation region subblock may be one of two rectangular blocks having a size ratio of 1:1 based on a horizontal axis (or a vertical axis). In this case, a flag (cu_sbt_flag) indicating that only subblocks have been transformed, directional (vertical/horizontal) information (cu_sbt_horizontal_flag), and/or location information (cu_sbt_pos_flag) are encoded by the entropy encoding unit 155 and signaled to the video decoding device. do. In addition, the size of the transform region subblock may have a size ratio of 1:3 based on the horizontal axis (or vertical axis), and in this case, a flag (cu_sbt_quad_flag) for distinguishing the corresponding division is additionally encoded by the entropy encoder 155 to obtain an image It is signaled to the decryption device.

Meanwhile, the transform unit 140 may individually transform the residual block in the horizontal direction and the vertical direction. For the transformation, various types of transformation functions or transformation matrices may be used. For example, a pair of transformation 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 highest transform efficiency among the MTS and transform the residual blocks in the horizontal and vertical directions, respectively. Information (mts_idx) on a pair of transform functions selected from the MTS is encoded by the entropy encoding unit 155 and signaled to the video decoding device.

The quantization unit 145 quantizes 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 without transformation for a certain block or frame. The quantization unit 145 may apply different quantization coefficients (scaling values) according to positions of transform coefficients in the transform block. A quantization matrix applied to the two-dimensionally arranged quantized transform coefficients may be coded and signaled to the video decoding apparatus.

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

The reordering unit 150 may change a 2D coefficient array into a 1D coefficient sequence using coefficient scanning. For example, the reordering unit 150 may output a one-dimensional coefficient sequence by scanning DC coefficients to coefficients in a high frequency region using a zig-zag scan or a diagonal scan. . Depending on the size of the transformation unit and intra prediction mode, instead of zig-zag scan, vertical scan that scans a 2D coefficient array in a column direction and horizontal scan that scans 2D block-shaped coefficients in a row direction may be used. That is, a scan method to be used among zig-zag scan, diagonal scan, vertical scan, and 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 schemes such as CABAC (Context-based Adaptive Binary Arithmetic Code) and Exponential Golomb to convert the one-dimensional quantized transform coefficients output from the reordering unit 150 to each other. A bitstream is created by encoding the sequence.

In addition, the entropy encoding unit 155 encodes information such as CTU size, CU splitting flag, QT splitting flag, MTT splitting type, and MTT splitting direction related to block splitting so that the video decoding apparatus can divide the block in the same way as the video encoding apparatus. make it possible to divide In addition, the entropy encoding unit 155 encodes information about a prediction type indicating whether the current block is encoded by intra prediction or inter prediction, and encodes intra prediction information (ie, intra prediction) according to the prediction type. mode) or inter prediction information (motion information encoding mode (merge mode or AMVP mode), merge index in case of merge mode, reference picture index and differential motion vector information in case of AMVP mode) are encoded. Also, the entropy encoding unit 155 encodes information related to quantization, that is, information about quantization parameters and information about quantization matrices.

The inverse quantization unit 160 inversely quantizes the quantized transform coefficients output from the quantization unit 145 to generate transform coefficients. The inverse transform unit 165 transforms transform coefficients output from the inverse quantization unit 160 from a frequency domain to a spatial domain to restore a residual block.

The adder 170 restores the current block by adding the restored residual block and the predicted block generated by the predictor 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 in order to reduce blocking artifacts, ringing artifacts, blurring artifacts, etc. caused by block-based prediction and transformation/quantization. perform filtering on The filter unit 180 is an in-loop filter and may include all or part of a deblocking filter 182, a sample adaptive offset (SAO) filter 184, and an adaptive loop filter (ALF) 186. .

The deblocking filter 182 filters the boundary between reconstructed blocks to remove blocking artifacts caused by block-by-block encoding/decoding, and the SAO filter 184 and alf 186 perform deblocking filtering. Additional filtering is performed on the image. The SAO filter 184 and the alf 186 are filters used to compensate for a difference between a reconstructed pixel and an original pixel caused by lossy coding. The SAO filter 184 improves not only subjective picture quality but also coding efficiency by applying an offset in units of CTUs. In contrast, the ALF 186 performs block-by-block filtering. Distortion is compensated for by applying different filters by distinguishing the edge of the corresponding block and the degree of change. Information on filter coefficients to be used for ALF may be coded and signaled to the video decoding apparatus.

The reconstruction 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 can be used as a reference picture for inter-prediction of blocks in the picture to be encoded later.

5 is an exemplary block diagram of a video decoding apparatus capable of implementing the techniques of this disclosure. Hereinafter, referring to FIG. 5, a video decoding device and sub-elements of the device will be described.

The image decoding apparatus includes an entropy decoding unit 510, a rearrangement 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 configured.

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

The entropy decoding unit 510 determines a current block to be decoded by extracting information related to block division by decoding the bitstream generated by the video encoding apparatus, and provides prediction information and residual signals necessary for restoring the current block. extract information, etc.

The entropy decoding unit 510 determines the size of the CTU by extracting information about the CTU size from a sequence parameter set (SPS) or a picture parameter set (PPS), and divides the picture into CTUs of the determined size. Then, the CTU is divided using the tree structure by determining the CTU as the top layer of the tree structure, that is, the root node, and extracting division information for the CTU.

For example, when a CTU is split using the QTBTTT structure, a first flag (QT_split_flag) related to splitting of QT is first extracted and each node is split into four nodes of a lower layer. In addition, for a node corresponding to a leaf node of QT, a second flag (MTT_split_flag) related to splitting of MTT and split direction (vertical / horizontal) and / or split type (binary / ternary) information are extracted and the corresponding leaf node is MTT split into structures Accordingly, each node below the leaf node of 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 the CU is split is first extracted, and when the corresponding block is split, a first flag (QT_split_flag) is extracted. may be During the splitting process, each node may have zero or more iterative MTT splits after zero or more repetitive QT splits. For example, the CTU may immediately undergo MTT splitting, or conversely, only QT splitting may occur multiple times.

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 BTs and split direction information are extracted.

Meanwhile, when the entropy decoding unit 510 determines a current block to be decoded by using tree structure partitioning, it extracts information about a prediction type indicating whether the current block is intra-predicted or inter-predicted. When the prediction type information indicates intra prediction, the entropy decoding unit 510 extracts syntax elements 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 syntax elements for the inter prediction information, that is, information indicating a motion vector and a reference picture to which the motion vector refers.

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

The reordering unit 515 converts the sequence of 1-dimensional quantized transform coefficients entropy-decoded in the entropy decoding unit 510 into a 2-dimensional coefficient array (ie, in the reverse order of the coefficient scanning performed by the image encoding apparatus). block) can be changed.

The inverse quantization unit 520 inverse quantizes the quantized transform coefficients and inverse quantizes the quantized transform coefficients using a quantization parameter. The inverse quantization unit 520 may apply different quantization coefficients (scaling values) to the two-dimensionally arranged quantized transform coefficients. The inverse quantization unit 520 may perform inverse quantization by applying a matrix of quantization coefficients (scaling values) from the image encoding device to a 2D array of quantized transformation coefficients.

The inverse transform unit 530 inversely transforms the inverse quantized transform coefficients from the frequency domain to the spatial domain to restore residual signals, thereby generating a residual block for the current block.

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

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

The prediction unit 540 may include an intra prediction unit 542 and an inter prediction unit 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 among a plurality of intra prediction modes from the syntax element for the intra prediction mode extracted from the entropy decoding unit 510, and references the current block according to the intra prediction mode. The current block is predicted using pixels.

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

The adder 550 restores 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 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 in-loop filters. The deblocking filter 562 performs deblocking filtering on boundaries between reconstructed blocks in order to remove blocking artifacts generated by block-by-block decoding. The SAO filter 564 and the ALF 566 perform additional filtering on the reconstructed block after deblocking filtering to compensate for the difference between the reconstructed pixel and the original pixel caused by lossy coding. ALF filter coefficients are determined using information on filter coefficients decoded from the non-stream.

The reconstruction 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 the picture to be encoded later.

This embodiment relates to encoding and decoding of images (video) as described above. More specifically, to improve video encoding efficiency and video quality, a video coding method and apparatus using various block division structures based on block width, height, or aspect ratio are provided.

The following embodiments, block division methods using various block division structures, may be performed by the picture divider 110 in the image encoding apparatus. Also, the video encoding apparatus may transmit the block division structure generated by the picture division unit 110 and signaling information related thereto to the video decoding apparatus.

The video encoding apparatus may generate a block division structure of the current block and related signaling information in terms of bit rate distortion optimization. The image encoding device may encode them using the entropy encoding unit 155 and transmit them to the image decoding device. The video decoding apparatus may decode a block division structure of a current block and related signaling information from a bitstream using the entropy decoding unit 510 .

As described above, the generated block division structure and signaling information related thereto may be utilized in the prediction unit 120, the transform unit 140, the quantization unit 150, and the like within the video encoding apparatus. In addition, the decoded block division structure and related signaling information may be utilized in the inverse quantization unit 520, the inverse transform unit 530, the prediction unit 540, and the like in the video decoding apparatus.

In the following description, one block may be a current block or a coding block. A current block and a coding block may be used interchangeably. In this case, coding is an expression that collectively refers to encoding and decoding.

In addition, the aspect ratio of the block is defined as a value obtained by dividing the horizontal length of the block by the vertical length.

Also, a value of one flag being true indicates a case in which the flag is set to 1. In addition, a false value of one flag indicates a case in which the flag is set to 0.

I. Conventional block partitioning structures

6 is an exemplary diagram illustrating various block divisions according to block division structures.

As an example, encoding and decoding may be performed in the form of NO_SPLIT without splitting one coding block into additional sub-blocks.

As another example, one square block can be divided into QT_SPLIT (hereinafter, used interchangeably with 'QT') into four sub-square blocks. A method of dividing one square block into four sub-square blocks is referred to as a block division method using a quad tree structure.

As another example, one square or rectangular block may be divided into BT_HOR divided into two horizontally divided subblocks or BT_VER divided into two vertically divided subblocks. A method of dividing one square or rectangular block into two horizontally divided sub-blocks or two vertically divided sub-blocks is referred to as a block partitioning method using a binary tree structure. Hereinafter, BT_HOR and BT_VER may be collectively referred to as BT.

As another example, one square or rectangular block may be divided into TT_HOR divided into 3 horizontally divided sub-blocks or TT_VER divided into 3 vertically divided sub-blocks. A method of dividing one square or rectangular block into three horizontally divided sub-blocks or three vertically divided sub-blocks is referred to as a block partitioning method using a ternary tree structure. Hereinafter, TT_HOR and TT_VER may be collectively referred to as TT.

II. Proposed block division structure

7A and 7B are exemplary diagrams illustrating a block division structure according to an embodiment of the present disclosure.

This embodiment proposes a block partitioning method using a sequential quad tree structure, which divides a rectangular block into four consecutive sub-square blocks. Meanwhile, in the examples of FIGS. 7A and 7B , a rectangular block is divided into four consecutive sub-square blocks, but is not necessarily limited thereto. That is, a rectangular block may also be divided into a plurality of sub-rectangular blocks.

A block division method using a contiguous quad tree structure encodes or parses block division syntax indicating whether to divide a block when an aspect ratio of one coding block satisfies a specific condition. By doing this, it is possible to efficiently reduce syntax overhead due to block division and to determine whether to divide a corresponding block into lower blocks.

As an example, a block partitioning method using a contiguous quad tree structure, when the aspect ratio of a coding block satisfies a specific condition, as in SQT_VER illustrated in FIG. Can be divided into blocks. In this case, a specific condition represents a case in which the aspect ratio of the coding block is 4, that is, the ratio of the width to the height of the coding block is 4:1.

As another example, a block partitioning method using a contiguous quad tree structure, when the aspect ratio of one coding block satisfies a specific condition, as in SQT_HOR illustrated in FIG. It can be partitioned into square coding blocks. In this case, a specific condition represents a case in which the aspect ratio of the coding block is 1/4, that is, the ratio of the width to the height of the coding block is 1:4.

8A and 8B are exemplary diagrams illustrating a coding order of divided blocks in a block division structure according to an embodiment of the present disclosure.

Hereinafter, the width of the current block to be coded is defined as w and the height as h.

When one of the block division methods using the contiguous quad tree structure according to the present embodiment is divided into four square blocks from left to right, as illustrated in FIG. 8A, sub-blocks of the current block The width may have a size of w/4 and a height of h. In this case, when a rectangular block is divided into four sub-square blocks from left to right using a continuous quad tree structure, the four sub-blocks have a width of w/4 and a height of h, and all of them have the same size. Satisfy the condition.

In addition, as illustrated in FIG. 8A, when one of the block division methods using a contiguous quad tree structure is divided into 4 square blocks from left to right, coding of 4 square sub-blocks is performed. It can be performed sequentially in the order from left to right.

Additionally, a technique for changing the coding order of blocks, such as coding block reordering, may be used together. In this case, coding of the sub-blocks may be sequentially performed in a left-to-right order based on syntax information (eg, a coding order flag) for determining the coding order of the four square sub-blocks. Alternatively, coding of sub-blocks may be sequentially performed in a right-to-left order.

Meanwhile, when one block is divided into four square coding blocks in a top-to-bottom direction in a block division method using a contiguous quad tree structure according to the present embodiment, as illustrated in FIG. 8B, a lower block of the current block may have a width of w and a height of h/4. In this case, when one rectangular block is divided into four square blocks from top to bottom using a continuous quad tree structure, the four sub-blocks have the same size as w in width and h/4 in height. satisfies the condition that

In addition, as illustrated in FIG. 8B, when one of the block division methods using the contiguous quad tree structure is divided into 4 square blocks from the top to the bottom, coding of the 4 square sub-blocks is performed from the top to the bottom. It may be performed sequentially in the order of the bottom direction.

Additionally, techniques for changing the coding order of blocks, such as coding block reordering, may be used together. In this case, coding of the sub-blocks may be sequentially performed from top to bottom based on syntax information for determining the coding order of the four square sub-blocks. Alternatively, coding of sub-blocks may be sequentially performed in the order from the bottom to the top.

9 is an exemplary diagram conceptually illustrating a signaling structure of syntax elements according to a block division structure.

According to the syntax signaling and parsing order illustrated in FIG. 9, a block division method using a quad tree structure, a block division method using a binary tree structure, a block division method using a ternary tree structure, and the like are combined to be applied. can Meanwhile, the application of the partitioning method according to the present embodiment is not limited to the case of combining and using the three different block partitioning structures as described above.

As illustrated in FIG. 9 , in signaling block division for a current block, split_flag, which is a division flag indicating whether to divide into first sub-blocks, may be signaled. When the value of the split flag split_flag is true and the current block is split, signaling of additional split information can be continued. On the other hand, if the value of the split flag split_flag is false and the current block is not split, the current block is transferred to a leaf node of QT (Quadtree) or MTT (Multiple-type Tree) without additional signaling of split information. can be determined

As described above, when the current block is divided, flags indicating division information may be additionally signaled. For example, when using a quad tree structure, a flag qt_split_flag indicating quad tree splitting may be signaled. Here, if the value of the flag qt_split_flag is true, the current block may be divided into four sub-blocks according to a block division method using a quad tree structure. On the other hand, when the value of the flag qt_split_flag is false, the current block may be split into sub-blocks according to a block division method using a structure other than the quad tree structure. In this case, additional signaling may be performed for a block division method using a different structure.

If the value of the flag qt_split_flag is false, as shown in FIG. 9, when one or more block division methods of a binary tree structure or a ternary tree structure are used in the coding process of the current block, whether the block is split in the horizontal/vertical direction An indicating flag, mtt_vertical_flag, may be signaled. Here, if the value of the flag mtt_vertical_flag is true, the current block may be divided into sub-blocks in the vertical direction, and if the value of the flag mtt_vertical_flag is false, the current block may be divided into sub-blocks in the horizontal direction.

Meanwhile, when block division is performed based on two or more different block division structures including a block division method using a binary tree structure and a block division method using a ternary tree structure, additional information indicating the division structure may be signaled. As illustrated in FIG. 9 , when a binary tree structure and a ternary tree structure are used, an additional flag mtt_binary_flag indicating a partition structure may be signaled. Here, when the value of the flag mtt_binary_flag is true, the current block is divided into two sub-blocks based on a block division method using a binary tree structure, and when the flag mtt_binary_flag is false, the current block uses a ternary tree structure. It can be divided into three sub-blocks based on the block division method.

10 is an exemplary diagram conceptually illustrating a signaling structure of syntax elements based on a block division structure according to an embodiment of the present disclosure.

According to the syntax signaling and parsing order illustrated in FIG. 10, a block division method using a quad tree structure, a block division method using a binary tree structure, a block division method using a ternary tree structure, and a contiguous quad tree A block partitioning method using a structure can be applied conjunctively.

As illustrated in FIG. 10 , in signaling block division for a current block, split_flag, which is a division flag indicating whether to divide into first sub-blocks, may be signaled. When the value of the split flag split_flag is true and the current block is split, signaling of additional split information can be continued as described above. On the other hand, when the value of the split flag split_flag is false and the current block is not split, in the example of FIG. 9 , the current block is determined as a leaf node of QT or a leaf node of MTT without additional signaling of split information.

However, in this embodiment, as illustrated in FIG. 10, before determining the current block as a leaf node of QT or MTT, if a condition for applying block division using a contiguous quad tree structure is satisfied, Additional syntax may be signaled. In this case, as illustrated in FIG. 10 , the additional syntax may be sqt_split_flag, which is a continuous split flag indicating application of a continuous quad tree structure. Here, when the value of the continuous split flag sqt_split_flag is true, as in the examples of FIGS. 8A and 8B , encoding and decoding may be sequentially performed after the current block is divided into four consecutive sub-blocks. In addition, when the value of the continuous split flag sqt_split_flag is false, the current block may be determined as a leaf node of QT or a leaf node of MTT.

Meanwhile, there may be a constraint that additional block partitioning is not performed on sub-blocks partitioned using the contiguous quad tree structure. That is, sub-blocks divided using the contiguous quad tree structure may be leaf nodes. Accordingly, syntax signaling and parsing processes according to block division as illustrated in FIGS. 9 and 10 for lower blocks may be omitted.

A condition for applying block division using a contiguous quad tree structure may be information derived from the width, height, and aspect ratio of the current block. As an example, this condition may be a case where the aspect ratio of the current block is 1:4 or 4:1. In addition, when the aspect ratio of the current block is 1:4 and the height is 4 times the width, the block may be divided according to the horizontal division using the block division illustrated in FIG. 8B. On the other hand, if the aspect ratio of the current block is 4:1 and the width is 4 times the height, the block may be divided according to vertical division using the block division illustrated in FIG. 8A.

However, if the aspect ratio condition of the current block and the condition that the smaller value of the width and height of the current block must be greater than or equal to the size of the smallest unit block available in the current encoding and decoding process are satisfied, the continuous quad tree structure A contiguous segmentation flag indicating application may be signaled or parsed. In this case, the size of the minimum unit block may be 4. As another example, the size of the minimum unit block may be replaced with 8 or 16 from the perspective of higher level syntax.

As described above, according to the present embodiment, it is possible to divide the current block in various ways while minimizing syntax overhead by minimizing additional syntax transmission even though a contiguous quad division structure is used in addition to the existing multi-type block division structure. it can be done

11 is an exemplary diagram conceptually illustrating a signaling structure of syntax elements based on a block division structure according to another embodiment of the present disclosure.

As illustrated in FIG. 11 , the current block may be quad-tree partitioned into four consecutive blocks according to a ratio of 1:1:1:1 or binary tree partitioned according to a ratio of 2:2. Alternatively, the current block may be split into an asymmetric binary tree according to a ratio of 1:3 or 3:1.

As illustrated in FIG. 11 , in dividing a current block into a plurality of sub-blocks according to the present embodiment, division methods according to the following four contiguous tree structures may be used in combination. A block division method of dividing the current block into four consecutive blocks in a horizontal or vertical direction according to a ratio of 1:1:1:1 may be used. A block division method of dividing the current block into two consecutive blocks in a horizontal or vertical direction according to a ratio of 2:2 may be used. A block division method of dividing the current block into two consecutive blocks in a horizontal or vertical direction according to a ratio of 1:3 may be used. Finally, a block division method of dividing the current block into two consecutive blocks in a horizontal or vertical direction according to a 3:1 ratio may be applied.

In this embodiment, as illustrated in FIG. 11, before determining the current block as a leaf node of QT or MTT, when a condition for applying block division using a contiguous quad tree structure is satisfied, additional syntax may be signaled. In this case, the additional syntax may be a contiguous split mode sqt_split_mode, which is a syntax indicating one of the four contiguous tree structures as described above. Accordingly, one of four contiguous tree structures is determined according to the value of the contiguous split mode sqt_split_mode (eg, 1 to 4), and the current block may be divided into contiguous blocks according to the determined contiguous tree structure. In addition, when the value of the continuous split mode sqt_split_mode is 0, the current block may be determined as a leaf node of QT or a leaf node of MTT.

In the flow chart/timing diagram of the present specification, it is described that each process is sequentially executed, but this is merely an example of the technical idea of one embodiment of the present disclosure. In other words, those skilled in the art to which an embodiment of the present disclosure belongs may change and execute the order described in the flowchart/timing diagram within the range that does not deviate from the essential characteristics of the embodiment of the present disclosure, or one of each process Since the above process can be applied by performing various modifications and variations in parallel, the flow chart/timing chart is not limited to a time-series sequence.

It should be understood in the above description that the exemplary embodiments may be implemented in many different ways. 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 in this specification have been labeled "...unit" to particularly 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. Non-transitory recording media include, for example, all types of recording devices in which data is stored in a form readable by a computer system. For example, the non-transitory recording medium includes storage media 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 an example of the technical idea of the present embodiment, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment, but to explain, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of this embodiment should be construed according to the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of this embodiment.

110: picture division
155: entropy encoding unit
510: entropy decoding unit

Claims (14)

In the method of dividing a current block, performed by an image decoding apparatus,
decoding a width and height of the current block and a division flag indicating whether to divide the current block from a bitstream;
Calculating an aspect ratio of the current block from the width and height of the current block, wherein the aspect ratio is a ratio obtained by dividing the width of the current block by the height;
Checking the value of the split flag
Including,
If the split flag is false,
checking whether the aspect ratio satisfies a first preset condition and whether the width and height satisfy a preset second condition;
When the aspect ratio satisfies the first condition and the width and height satisfy the second condition, decoding a continuous partition flag indicating application of a sequential quad tree structure from the bitstream; and
Dividing the current block into sub-blocks using the contiguous quad tree structure when the contiguous division flag is true.
Characterized in that, the method comprising a. According to claim 1,
If the split flag is false,
and determining the current block as a leaf node when the aspect ratio does not satisfy the first condition or the width and height do not satisfy the second condition. . According to claim 1,
If the above split flag is true,
decoding one or more additional syntax elements to divide the current block; and
Dividing the current block according to the additional syntax elements
Characterized in that it further comprises, the method. According to claim 1,
The first condition is,
The method characterized in that the aspect ratio is 4: 1 or 1: 4 conditions. According to claim 1
The second condition is,
Characterized in that the condition that the smaller value of the width and height must be greater than or equal to the size of the predetermined minimum unit block. According to claim 1,
The step of dividing into the sub-blocks,
Based on the aspect ratio, the current block is divided into 4 consecutive sub-square blocks by vertical division or the current block is divided into 4 consecutive sub-square blocks by horizontal division, the sub-blocks having the same size. characterized by having, a method. According to claim 1,
The sub blocks are
Characterized in that leaf nodes are not subjected to further block splitting. According to claim 1,
The sub blocks are
In the case of vertically partitioned blocks, decoding is sequentially performed in a left-to-right order, and in the case of horizontally partitioned blocks, decoding is performed sequentially in a top-to-bottom order. According to claim 1,
Further comprising the step of decoding a flag indicating a coding order;
The sub blocks are
In the case of vertically segmented blocks, they are sequentially decoded from left to right or from right to left according to the value of the flag, and in the case of horizontally segmented blocks, from top to bottom according to the value of the flag. Characterized in that the decoding is performed sequentially in order or in order from bottom to top. According to claim 1,
and determining the current block as a leaf node when the continuous division flag is false. In the method of dividing a current block, performed by an image encoding apparatus,
determining the width and height of the current block;
determining a division flag indicating whether to divide the current block;
Calculating an aspect ratio of the current block from the width and height of the current block, wherein the aspect ratio is a ratio obtained by dividing the width of the current block by the height;
Checking the value of the split flag
Including,
If the split flag is false,
checking whether the aspect ratio satisfies a first preset condition and whether the width and height satisfy a preset second condition;
determining a continuous division flag indicating application of a sequential quad tree structure when the aspect ratio satisfies the first condition and the width and height satisfy the second condition;
splitting the current block into sub-blocks using the contiguous quad tree structure when the contiguous division flag is true; and
Encoding the width and height of the current block, the split flag, and the continuous split flag
Characterized in that, the method comprising a. According to claim 11,
If the split flag is false,
and determining the current block as a leaf node when the aspect ratio does not satisfy the first condition or the width and height do not satisfy the second condition. . According to claim 11,
and determining the current block as a leaf node when the continuous division flag is false. A computer-readable recording medium storing a bitstream generated by an image encoding method, the image encoding method comprising:
determining the width and height of the current block;
determining a division flag indicating whether to divide the current block;
Calculating an aspect ratio of the current block from the width and height of the current block, wherein the aspect ratio is a ratio obtained by dividing the width of the current block by the height;
Checking the value of the split flag
Including,
If the split flag is false,
checking whether the aspect ratio satisfies a first preset condition and whether the width and height satisfy a preset second condition;
determining a continuous division flag indicating application of a sequential quad tree structure when the aspect ratio satisfies the first condition and the width and height satisfy the second condition;
splitting the current block into sub-blocks using the contiguous quad tree structure when the contiguous division flag is true; and
Encoding the width and height of the current block, the split flag, and the continuous split flag
Characterized in that it comprises, a recording medium.

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