Method and apparatus for video coding using rearrangement of prediction signals in intra block copy mode

Abstract

The present embodiment discloses a method and apparatus for video coding using rearrangement of a prediction signal in an intra block copy mode. In this embodiment, a video decoding device obtains a splitting direction indicating a horizontal splitting or a vertical splitting of a current block, and obtains a ratio of sub-blocks with respect to the current block. A video decoding device generates an initial prediction block of a current block according to an intra block copy (IBC) mode. The video decoding device splits the initial prediction block into sub-blocks according to the splitting direction and the proportion of the sub-blocks, and then rearranges the order of the sub-blocks to generate a final prediction block of the current block.

Description

Technical Field

[0001] The present disclosure relates to a video coding method and apparatus using rearrangement of a prediction signal in an intra block copy mode. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Since video data has a large data amount compared with audio or still image data, the video data requires a large amount of hardware resources (including memory) to store or transmit the video data without compression processing.

[0004] Thus, encoders are generally used to compress and store or transmit video data. A decoder receives compressed video data, decompresses the received compressed video data, and plays the decompressed video data. Video compression technologies include H.264 / Advanced Video Coding (AVC), High Efficiency Video Coding (HEVC), and Versatile Video Coding (VVC), which have improved coding efficiency of about 30% or more compared to HEVC.

[0005] However, as image size, resolution and frame rate gradually increase, the amount of data to be encoded also increases. Thus, a new compression technology that provides higher encoding efficiency and improved image enhancement effect than existing compression technologies is needed.

[0006] When performing prediction of the current block, the intra block copy (IBC) mode generates a prediction block of the current block from the reconstructed area in the current frame using the parsed block vector information. The IBC mode is divided into a merge mode and an advanced motion vector prediction (AMVP) mode. In the merge mode, the encoder signals a merge index, and in the AMVP mode, the encoder signals an index indicating a block vector predictor (BVP) and a block vector difference (BVD). In the IBC mode as described above, the current block is processed as a single block. Therefore, in order to improve video coding efficiency and enhance video quality, it is necessary to consider utilizing sub-blocks of the current block. Summary of the invention

[0007] [Technical issues]

[0008] The present disclosure attempts to provide a video encoding method and apparatus for reconstructing a current block by rearranging an initial prediction signal when the prediction signal of the current block is generated from a reconstructed region in a current frame by using a block vector.

[0009] [Technical solution]

[0010] At least one aspect of the present disclosure provides a method for reconstructing a current block by a video decoding device. The method includes: obtaining a split direction of the current block, the split direction indicating horizontal splitting or vertical splitting. The method also includes obtaining a ratio of a sub-block relative to the current block. The method also includes: generating an initial prediction block of the current block according to an intra-block copy (IBC) mode. The method also includes splitting the initial prediction block into sub-blocks based on the split direction and the ratio of the sub-blocks. The method also includes generating a final prediction block of the current block by rearranging the sub-blocks.

[0011] Another aspect of the present disclosure provides a method for encoding a current block by a video encoding device. The method includes: generating an initial prediction block of the current block according to an intra-block copy (IBC) mode. The method also includes obtaining a split direction of the current block, and the split direction indicates horizontal splitting or vertical splitting. The method also includes obtaining a ratio of a sub-block relative to the current block. The method also includes splitting the initial prediction block into sub-blocks based on the split direction and the ratio of the sub-blocks. The method also includes generating a final prediction block of the current block by rearranging the sub-blocks.

[0012] Another aspect of the present disclosure provides a computer-readable recording medium storing a bitstream generated by a video encoding method. The video encoding method includes: generating an initial prediction block of a current block according to an intra-block copy (IBC) mode. The video encoding method includes: obtaining a split direction of the current block, and the split direction indicates horizontal splitting or vertical splitting. The video encoding method includes: obtaining a ratio of a sub-block relative to the current block. The video encoding method includes: splitting the initial prediction block into sub-blocks based on the split direction and the ratio of the sub-blocks. The video encoding method includes: generating a final prediction block of the current block by rearranging the sub-blocks.

[0013] [Beneficial Effects]

[0014] As described above, the present disclosure provides a video encoding method and apparatus for reconstructing a current block by rearranging an initial signal when a prediction signal of the current block is generated from a reconstruction region of a current frame by using a block vector. Thus, the video encoding method and apparatus improve video encoding efficiency and improve video quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram of a video encoding device that may implement the techniques of this disclosure.

[0016] Figure 2 A method for partitioning blocks using a quadtree plus binary tree ternary tree (QTBTTT) structure is shown.

[0017] 3A and 3B illustrate a plurality of intra prediction modes including a wide-angle intra prediction mode.

[0018] Figure 4Neighboring blocks of the current block are shown.

[0019] Figure 5 is a block diagram of a video decoding device that may implement the techniques of this disclosure.

[0020] Figure 6 is a block diagram detailing a portion of a video decoding apparatus according to at least one embodiment of the present disclosure.

[0021] Figure 7 The present invention is a flowchart of a method for predicting a current block based on an IBC (Intra Block Copy) mode, performed by a video decoding apparatus according to at least one embodiment of the present disclosure.

[0022] Figure 8 is a diagram illustrating vertically divided sub-blocks according to at least one embodiment of the present disclosure.

[0023] Fig. 9 is a diagram illustrating horizontally partitioned sub-blocks according to at least one embodiment of the present disclosure.

[0024] Figures 10 to 13 is a diagram illustrating rearrangement of initial prediction blocks according to some embodiments of the present disclosure.

[0025] Fig.14 is a flowchart of a method for predicting a current block based on an IBC mode, performed by a video decoding device according to another embodiment of the present disclosure.

[0026] Fig.15 is a diagram showing vertically or horizontally partitioned sub-blocks according to at least one embodiment of the present disclosure.

[0027] 16A and 16B are diagrams illustrating application of filtering to a sub-block boundary according to at least one embodiment of the present disclosure.

[0028] 17A and 17B are diagrams illustrating application of filtering to a sub-block boundary according to another embodiment of the present disclosure.

[0029] Fig.18 The present invention is a flowchart of a method for predicting a current block based on an IBC mode, performed by a video encoding apparatus according to at least one embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Hereinafter, some embodiments of the present disclosure are described in detail with reference to the accompanying drawings. In the following description, the same reference numerals represent the same elements, although the elements are shown in different drawings. In addition, in the following description of some embodiments, for the purpose of clarity and brevity, detailed descriptions of related known parts and functions may be omitted when it is considered to obscure the subject matter of the present disclosure.

[0031] Figure 1 is a block diagram of a video encoding device that can implement the technology of the present disclosure. Figure 1 , describing a video encoding apparatus and components of the apparatus.

[0032] The encoding device may include a picture splitter 110, a predictor 120, a subtractor 130, a transformer 140, a quantizer 145, a rearrangement unit 150, an entropy encoder 155, an inverse quantizer 160, an inverse transformer 165, an adder 170, a loop filter unit 180 and a memory 190.

[0033] Each component of the encoding device can be implemented as hardware or software or as a combination of hardware and software. In addition, the function of each component can be implemented as software, and a microprocessor can also be implemented to execute the function of the software corresponding to each component.

[0034] A video consists of one or more sequences including multiple pictures. Each picture is split into multiple regions, and encoding is performed on each region. For example, a picture is split into one or more tiles or / and slices. Here, one or more slices can be defined as a slice group. Each slice or / and slice is split into one or more coding tree units (CTUs). In addition, each CTU is split into one or more coding units (CUs) through a tree structure. The information applied to each coding unit (CU) is encoded as the syntax of the CU, and the information commonly applied to the CU included in a CTU is encoded as the syntax of the CTU. In addition, the information commonly applied to all blocks in a slice is encoded as the syntax of the slice header, and the information applied to all blocks constituting one or more pictures is encoded as a picture parameter set (PPS) or a picture header. In addition, the information commonly referenced by multiple pictures is encoded into a sequence parameter set (SPS). In addition, the information commonly referenced by one or more SPSs is encoded into a video parameter set (VPS). Further, the information commonly applied to a slice or a slice group can also be encoded as the syntax of a slice or a slice group header. The syntax included in the SPS, PPS, slice header, slice or slice group header may be referred to as a high-level syntax.

[0035] The picture splitter 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 an SPS or a PPS and transmitted to a video decoding apparatus.

[0036] The picture splitter 110 splits each picture constituting a video into a plurality of coding tree units (CTUs) having a predetermined size, and then recursively splits the CTUs by using a tree structure. A leaf node in the tree structure becomes a coding unit (CU), which is a basic unit of encoding.

[0037] The tree structure can be a quadtree (QT), in which a higher node (or parent node) is split into four lower nodes (or child nodes) of the same size. The tree structure can also be a binary tree (BT), in which a higher node is split into two lower nodes. The tree structure can also be a ternary tree (TT), in which a higher node is split into three lower nodes at a ratio of 1:2:1. The tree structure can also be a structure in which two or more of the QT structure, the BT structure, and the TT structure are mixed. For example, a quadtree plus a binary tree (QTBT) structure can be used or a quadtree plus a binary tree ternary tree (QTBTTT) structure can be used. Here, a binary tree ternary tree (BTTT) is added to the tree structure to be referred to as a multi-type tree (MTT).

[0038] Figure 2 is a diagram for describing a method of splitting a block by using a QTBTTT structure.

[0039] like Figure 2 As shown, the CTU can first be split into a QT structure. The quadtree splitting can be recursive until the size of the split block reaches the minimum block size (MinQTSize) of the leaf node allowed in QT. The first flag (QT_split_flag) indicating whether each node of the QT structure is split into four nodes of the lower layer is encoded by the entropy encoder 155 and sent to the video decoding device. When the leaf node of QT is not larger than the maximum block size (MaxBTSize) of the root node allowed in BT, the leaf node can be further split into at least one of the BT structure and the TT structure. There may be multiple splitting directions in the BT structure and / or the TT structure. For example, there may be two directions, namely, the direction in which the blocks of the corresponding node are split horizontally and the direction in which the blocks of the corresponding node are split vertically. As Figure 2 As shown, when MTT splitting begins, a second flag (mtt_split_flag) indicating whether the node is split and a flag further indicating the split direction (vertical or horizontal) and / or a flag indicating the split type (two-pronged or three-pronged) if the node is split are encoded by the entropy encoder 155 and sent to the video decoding device with a signal.

[0040] Optionally, before encoding the first flag (QT_split_flag) indicating whether each node is split into four nodes of the lower layer, a CU split flag (split_cu_flag) indicating whether the node is split may also be encoded. When the value of the CU split flag (split_cu_flag) indicates that each node is not split, the block of the corresponding node becomes a leaf node in the split tree structure and becomes a CU as a basic unit of encoding. When the value of the CU split flag (split_cu_flag) indicates that each node is split, the video encoding device first starts encoding the first flag through the above scheme.

[0041] When QTBT is used as another example of a tree structure, there may be two types, namely, a type in which the block of the corresponding node is horizontally split into two blocks of the same size (i.e., symmetrical horizontal splitting) and a type in which the block of the corresponding node is vertically split into two blocks of the same size (i.e., symmetrical vertical splitting). A split flag (split_flag) indicating whether each node of the BT structure is split into blocks of the lower layer and split type information indicating the split type are encoded by the entropy encoder 155 and transmitted to the video decoding device. At the same time, a type in which the block of the corresponding node is split into two blocks that are asymmetric to each other may be additionally presented. The symmetrical form may include a form in which the block of the corresponding node is split into two rectangular blocks having a size ratio of 1:3, or may also include a form in which the block of the corresponding node is split in a diagonal direction.

[0042] A CU may have different sizes according to the QTBT or QTBTTT split from a CTU. In the following, a block corresponding to a CU to be encoded or decoded (i.e., a leaf node of a QTBTTT) is referred to as a "current block". Due to the adoption of QTBTTT splitting, the shape of the current block may be a rectangular shape in addition to a square shape.

[0043] The predictor 120 predicts the current block to generate a predicted block. The predictor 120 includes an intra predictor 122 and an inter predictor 124.

[0044] Typically, each of the current blocks in a picture may be predictively encoded. Typically, the prediction of the current block may be performed using intra-prediction techniques (using data from the picture including the current block) or inter-prediction techniques (using data from a picture encoded before the picture including the current block). Inter-prediction includes both unidirectional prediction and bidirectional prediction.

[0045] The intra-frame predictor 122 predicts the pixels in the current block by using the pixels (reference pixels) located in the neighboring position of the current block in the current picture including the current block. According to the prediction direction, there are multiple intra-frame prediction modes. For example, as shown in Figure 3A, multiple intra-frame prediction modes may include 2 non-directional modes including a plane mode and a DC mode, and may include 65 directional modes. Neighboring pixels and the arithmetic equations to be used are defined differently according to each prediction mode.

[0046] In order to perform effective directional prediction on the current block having a rectangular shape, a directional mode (#67 to #80, intra prediction mode #-1 to #-14) as illustrated by the dotted arrows in FIG. 3B may be additionally used. The directional mode may be referred to as a "wide-angle intra prediction mode". In FIG. 3B, the arrow indicates the corresponding reference sample used for prediction and does not indicate the prediction direction. The prediction direction is opposite to the direction indicated by the arrow. When the current block has a rectangular shape, the wide-angle intra prediction mode is a mode in which prediction is performed in a direction opposite to a specific directional mode without additional bit transmission. In this case, in the wide-angle intra prediction mode, some wide-angle intra prediction modes that can be used for the current block can be determined by the ratio of the width and height of the current block having a rectangular shape. For example, when the current block has a rectangular shape with a height less than the width, a wide-angle intra prediction mode (intra prediction mode #67 to #80) with an angle less than 45 degrees is available. When the current block has a rectangular shape with a width greater than the height, a wide-angle intra prediction mode with an angle greater than -135 degrees may be used.

[0047] The intra-frame predictor 122 may determine an intra-frame prediction to be used for encoding the current block. In some instances, the intra-frame predictor 122 may encode the current block by using multiple intra-frame prediction modes, and may further select an appropriate intra-frame prediction mode to be used from a test mode. For example, the intra-frame predictor 122 may calculate a rate-distortion value by using a rate-distortion analysis for multiple tested intra-frame prediction modes, and may further select an intra-frame prediction mode having the best rate-distortion characteristics in the test mode.

[0048] The intra predictor 122 selects an intra prediction mode from among a plurality of intra prediction modes and predicts the current block by using adjacent pixels (reference pixels) and an arithmetic equation determined according to the selected intra prediction mode. Information on the selected intra prediction mode is encoded by the entropy encoder 155 and transmitted to the video decoding apparatus.

[0049] The inter-frame predictor 124 generates a prediction block for the current block by using a motion compensation process. The inter-frame predictor 124 searches for a block most similar to the current block in a reference picture that is encoded and decoded earlier than the current picture, and generates a prediction block for the current block by using the searched block. In addition, a motion vector (MV) is generated, which corresponds to the displacement between the current block in the current picture and the prediction block in the reference picture. Typically, motion estimation is performed on the luminance component, and the motion vector calculated based on the luminance component is used for both the luminance component and the chrominance component. Motion information including information about the reference picture and information about the motion vector used to predict the current block is encoded by the entropy encoder 155 and transmitted to the video decoding device.

[0050] The inter-frame predictor 124 may also perform interpolation on a reference picture or a reference block to increase the accuracy of the prediction. In other words, the subsamples between two consecutive integer samples are interpolated by applying the filter coefficients to a plurality of consecutive integer samples including two integer samples. When the process of searching for the block most similar to the current block is performed for the interpolated reference picture, the decimal unit precision may be used instead of the integer sample unit precision for the motion vector representation. The precision or resolution of the motion vector may be set differently for each target region to be encoded (e.g., units such as slices, slices, CTUs, CUs, etc.). When such an adaptive motion vector resolution (AMVR) is applied, information about 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 about the motion vector resolution applied to each CU is signaled. The information about the motion vector resolution may be information representing the precision of the motion vector difference to be described below.

[0051] Meanwhile, the inter-frame predictor 124 may perform inter-frame prediction by using bidirectional prediction. In the case of bidirectional prediction, two reference pictures and two motion vectors representing the block position most similar to the current block in each reference picture are used. The inter-frame predictor 124 selects a first reference picture and a second reference picture from a reference picture list 0 (RefPicList0) and a reference picture list 1 (RefPicList1), respectively. The inter-frame predictor 124 also searches for a block most similar to the current block in the corresponding reference picture to generate a first reference block and a second reference block. In addition, a prediction block of the current block is generated by averaging or weighted averaging the first reference block and the second reference block. In addition, motion information including information about two reference pictures for predicting the current block and including information about two motion vectors is transmitted to the entropy encoder 155. Here, the reference picture list 0 may be composed of pictures before the current picture in the display order among the pre-reconstructed pictures, and the reference picture list 1 may be composed of pictures after the current picture in the display order among the pre-reconstructed pictures. However, although not particularly limited thereto, a pre-reconstructed picture after the current picture in the display order may be additionally included in the reference picture list 0. Conversely, a pre-reconstructed picture before the current picture may also be additionally included in the reference picture list 1.

[0052] In order to minimize the number of bits consumed for encoding motion information, various methods may be used.

[0053] For example, when the reference picture and motion vector of the current block are the same as those of the adjacent block, information capable of identifying the adjacent block is encoded to transmit the motion information of the current block to the video decoding device. This method is called merge mode.

[0054] In the merge mode, the inter predictor 124 selects a predetermined number of merge candidate blocks (hereinafter, referred to as “merge candidates”) from the neighboring blocks of the current block.

[0055] As a neighboring block for deriving merge candidates, such as Figure 4 As shown in , all or some of the left block A0, the lower left block A1, the upper block B0, the upper right block B1, and the upper left block B2 adjacent to the current block in the current picture can be used. Further, blocks located in a reference picture other than the current picture in which the current block is located (which may be the same as or different from the reference picture used to predict the current block) can also be used as merge candidates. For example, a block located at the same location as the current block or a block adjacent to a block located at the same location in the reference picture can be used as a merge candidate in addition. If the number of merge candidates selected by the method described above is less than the preset number, a zero vector is added to the merge candidate.

[0056] The inter-frame predictor 124 configures a merge list including a predetermined number of merge candidates by using neighboring blocks. A merge candidate to be used as motion information of the current block is selected from 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 entropy encoder 155 and transmitted to the video decoding device.

[0057] Merge skip mode is a special case of merge mode. After quantization, when all transform coefficients for entropy coding are close to zero, only the neighbor block selection information is sent without the residual signal. By using merge skip mode, relatively high coding efficiency can be achieved for images with slight motion, still images, screen content images, etc.

[0058] Hereinafter, the merge mode and the merge skip mode are collectively referred to as the merge / skip mode.

[0059] Another method for encoding motion information is the Advanced Motion Vector Prediction (AMVP) mode.

[0060] In the AMVP mode, the inter-frame predictor 124 derives a motion vector predictor candidate for a motion vector of the current block by using neighboring blocks of the current block. As neighboring blocks for deriving motion vector predictor candidates, the neighboring blocks in the Figure 4All or some of the left block A0, lower left block A1, upper block B0, upper right block B1 and upper left block B2 adjacent to the current block in the current picture shown in . In addition, blocks located in a reference picture other than the current picture in which the current block is located (which may be the same as or different from the reference picture used to predict the current block) may also be used as adjacent blocks for deriving motion vector prediction candidates. For example, blocks located at the same location as the current block within the reference picture or blocks adjacent to blocks at the same location may be used. If the number of motion vector candidates selected by the above method is less than the preset number, a zero vector is added to the motion vector candidates.

[0061] The inter predictor 124 derives a motion vector prediction candidate by using the motion vector of the neighboring block, and determines a motion vector prediction for the motion vector of the current block by using the motion vector prediction candidate. In addition, a motion vector difference is calculated by subtracting the motion vector prediction from the motion vector of the current block.

[0062] A motion vector prediction can be obtained by applying a predefined function (e.g., center value and average value calculation, etc.) to a motion vector prediction candidate. In this case, the video decoding device also knows the predefined function. In addition, since the neighboring blocks used to derive the motion vector prediction candidate are blocks for which encoding and decoding have been completed, the video decoding device may also already know the motion vectors of the neighboring blocks. Therefore, the video encoding device does not need to encode information for identifying the motion vector prediction candidate. Thus, in this case, information about the motion vector difference and information about the reference picture used to predict the current block are encoded.

[0063] Meanwhile, the motion vector prediction may also be determined by selecting any one of the motion vector prediction candidates. In this case, information for identifying the selected motion vector prediction candidate is additionally encoded jointly with information about the motion vector difference and information about the reference picture used to predict the current block.

[0064] The subtractor 130 generates a residual block by subtracting a prediction block generated by the intra predictor 122 or the inter predictor 124 from the current block.

[0065] The transformer 140 transforms the residual signal in the residual block having the pixel value in the spatial domain into the transform coefficient in the frequency domain. The transformer 140 may transform the residual signal in the residual block by using the total size of the residual block as the transform unit, or may also split the residual block into a plurality of sub-blocks, and may perform the transform by using the sub-block as the transform unit. Optionally, the residual block is split into two sub-blocks, namely a transform region and a non-transform region, so as to transform the residual signal using only the transform region sub-block as the transform unit. Here, the transform region sub-block 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) indicates that only the sub-block is transformed, and the direction (vertical / horizontal) information (cu_sbt_horizontal_flag) and / or the position information (cu_sbt_pos_flag) are encoded by the entropy encoder 155 and sent to the video decoding device by a signal. In addition, the size of the transform region sub-block may have a size ratio of 1:3 based on the horizontal axis (or vertical axis). In this case, a flag (cu_sbt_quad_flag) for dividing the corresponding split is additionally encoded by the entropy encoder 155 and sent to the video decoding device using a signal.

[0066] At the same time, the transformer 140 may perform transformations on the residual block separately in the horizontal direction and the vertical direction. For the transformation, different 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 transformation set (MTS). The transformer 140 may select a transformation function pair with the highest transformation efficiency in the MTS, and may transform the residual block in each of the horizontal and vertical directions. Information about the transformation function pair in the MTS (mts_idx) is encoded by the entropy encoder 155 and sent to the video decoding device with a signal.

[0067] The quantizer 145 quantizes the transform coefficients output from the transformer 140 using the quantization parameters and outputs the quantized transform coefficients to the entropy encoder 155. The quantizer 145 can also immediately quantize the relevant residual block without transforming any block or frame. The quantizer 145 can also apply different quantization coefficients (scaling values) according to the position of the transform coefficient in the transform block. The quantization matrix applied to the quantized transform coefficients arranged in 2 dimensions can be encoded and sent to the video decoding device with a signal.

[0068] The rearrangement unit 150 may perform rearrangement of coefficient values ​​with respect to the quantized residual value.

[0069] The rearrangement unit 150 can change the 2D coefficient array into a 1D coefficient sequence by using coefficient scanning. For example, the rearrangement unit 150 can output the ID coefficient sequence by scanning the DC coefficient into a high frequency domain coefficient using a zigzag scan or a diagonal scan. Depending on the size of the transform unit and the intra-frame prediction mode, a vertical scan that scans the 2D coefficient array in the column direction and a horizontal scan that scans the 2D block type coefficient in the row direction can also be used instead of the zigzag scan. In other words, depending on the size of the transform unit and the intra-frame prediction mode, the scanning method to be used can be determined among zigzag scanning, diagonal scanning, vertical scanning, and horizontal scanning.

[0070] The entropy encoder 155 generates a bitstream by encoding the sequence of ID-quantized transform coefficients output from the rearrangement unit 150 using various encoding schemes including context-based adaptive binary arithmetic coding (CABAC), exponential Golomb, and the like.

[0071] In addition, the entropy encoder 155 encodes information related to block splitting (such as CTU size, CTU splitting flag, QT splitting flag, MTT splitting type, MTT splitting direction, etc.) to allow the video decoding device to split the block equally to the video encoding device. In addition, the entropy encoder 155 encodes information about the prediction type indicating whether the current block is encoded by intra-frame prediction or inter-frame prediction. The entropy encoder 155 encodes intra-frame prediction information (i.e., information about intra-frame prediction mode) or inter-frame prediction information (in the case of merge mode, merge index, and in the case of AMVP mode, information about reference picture index and motion vector difference) according to the prediction type. In addition, the entropy encoder 155 encodes information related to quantization (i.e., information about quantization parameters and information about quantization matrices).

[0072] The inverse quantizer 160 dequantizes the quantized transform coefficient output from the quantizer 145 to generate a transform coefficient. The inverse transformer 165 transforms the transform coefficient output from the inverse quantizer 160 from the frequency domain to the spatial domain to reconstruct a residual block.

[0073] The adder 170 reconstructs the current block by adding the reconstructed residual block and the prediction block generated by the predictor 120. When intra prediction is performed on the next sequential block, pixels in the reconstructed current block may be used as reference pixels.

[0074] The loop filter unit 180 performs filtering on the reconstructed pixels in order to reduce block artifacts, ringing artifacts, blur artifacts, etc. that occur due to block-based prediction and transform / quantization. The loop filter unit 180 as a loop filter may include all or some of a deblocking filter 182, a sample adaptive offset (SAO) filter 184, and an adaptive loop filter (ALF) 186.

[0075] The deblocking filter 182 filters the boundaries between the reconstructed blocks to remove block artifacts that occur due to block unit encoding / decoding, and the SAO filter 184 and the ALF 186 perform additional filtering for the deblocked filtered video. The SAO filter 184 and the ALF 186 are filters for compensating for the difference between the reconstructed pixels and the original pixels due to lossy encoding. The SAO filter 184 applies an offset as a CTU unit to enhance subjective image quality and coding efficiency. On the other hand, the ALF 186 performs block unit filtering and applies different filters to compensate for distortion by dividing the boundaries of the corresponding blocks and the degree of variation. Information about the filter coefficients to be used for the ALF can be encoded and sent to the video decoding device with a signal.

[0076] The reconstructed blocks filtered by the deblocking filter 182, the SAO filter 184, and the ALF 186 are 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-frame prediction of blocks in a picture to be encoded later.

[0077] The video encoding device may store the bit stream of the encoded video data in a non-transitory storage medium, or transmit the bit stream to the video decoding device through a communication network.

[0078] Figure 5 is a functional block diagram of a video decoding device that can implement the technology of the present disclosure. Figure 5 , describing a video decoding apparatus and components of the apparatus.

[0079] The video decoding apparatus may include an entropy decoder 510 , a rearrangement unit 515 , an inverse quantizer 520 , an inverse transformer 530 , a predictor 540 , an adder 550 , a loop filter unit 560 , and a memory 570 .

[0080] and Figure 1 Similar to the video encoding device of the present invention, each component of the video decoding device can be implemented as hardware or software or as a combination of hardware and software. In addition, the function of each component can be implemented as software, and a microprocessor can also be implemented to execute the function of the software corresponding to each component.

[0081] The entropy decoder 510 extracts information related to block splitting by decoding a bitstream generated by a video encoding apparatus to determine a current block to be decoded, and extracts prediction information required to reconstruct the current block and information about a residual signal.

[0082] The entropy decoder 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 a determined size. In addition, the CTU is determined as the highest level of the tree structure, i.e., the root node, and the split information of the CTU can be extracted to split the CTU using the tree structure.

[0083] For example, when a CTU is split using a QTBTTT structure, a first flag (QT_split_flag) associated with the splitting of the QT is first extracted to split each node into four nodes of the lower layer. In addition, for a node corresponding to a leaf node of the QT, a second flag (mtt_split_flag) associated with the splitting of the MTT, a splitting direction (vertical / horizontal) and / or a splitting type (binary / ternary) are extracted to split the corresponding leaf node into an MTT structure. As a result, each node below the leaf node of the QT is recursively split into a BT or TT structure.

[0084] As another example, when a CTU is split by using a QTBTTT structure, a CU split flag (split_cu_flag) indicating whether the CU is split is extracted. When the corresponding block is split, a first flag (QT_split_flag) may also be extracted. During the splitting process, for each node, 0 or more recursive MTT splits may occur after 0 or more recursive QT splits. For example, for a CTU, MTT splitting may occur immediately, or conversely, only multiple QT splits may occur.

[0085] As another example, when the CTU is split using the QTBT structure, the first flag (QT_split_flag) related to the splitting of the QT is extracted to split each node into four nodes of the lower layer. In addition, the splitting flag (split_flag) indicating whether the node corresponding to the leaf node of the QT is further split into BTs and the splitting direction information are extracted.

[0086] Meanwhile, when the entropy decoder 510 determines the current block to be decoded by splitting using the tree structure, the entropy decoder 510 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 decoder 510 extracts syntax elements of intra-prediction information (intra-prediction mode) for the current block. When the prediction type information indicates inter-prediction, the entropy decoder 510 extracts information representing syntax elements for inter-prediction information (i.e., motion vectors and reference pictures referenced by motion vectors).

[0087] Furthermore, the entropy decoder 510 extracts quantization-related information and extracts information on a quantized transform coefficient of the current block as information on a residual signal.

[0088] The rearrangement unit 515 may change the sequence of 1D quantized transform coefficients entropy-decoded by the entropy decoder 510 into a 2D coefficient array (ie, block) again in the reverse order of the coefficient scanning order performed by the video encoding device.

[0089] The inverse quantizer 520 dequantizes the quantized transform coefficients and dequantizes the quantized transform coefficients by using quantization parameters. The inverse quantizer 520 may also apply different quantization coefficients (scaling values) to the quantized transform coefficients arranged in 2D. The inverse quantizer 520 may perform dequantization by applying a matrix (scaling value) of quantization coefficients from a video encoding device to a 2D array of quantized transform coefficients.

[0090] The inverse transformer 530 generates a residual block of the current block by inversely transforming the dequantized transform coefficients from the frequency domain into the spatial domain to reconstruct a residual signal.

[0091] In addition, when the inverse transformer 530 inversely transforms a partial region (sub-block) of the transform block, the inverse transformer 530 extracts a flag (cu_sbt_flag) that only the sub-block of the transform block is transformed, direction (vertical / horizontal) information (cu_sbt_horizontal_flag) of the sub-block, and / or position information (cu_sbt_pos_flag) of the sub-block. The inverse transformer 530 also inversely transforms the transform coefficient of the corresponding sub-block from the frequency domain to the spatial domain to reconstruct the residual signal and fills the uninverse-transformed region with a value of "0" as the residual signal to generate a final residual block of the current block.

[0092] In addition, when MTS is applied, the inverse transformer 530 determines a transform index or a transform matrix applied in each of the horizontal and vertical directions by using MTS information (mts_idx) signaled from the video encoding device. The inverse transformer 530 also performs inverse transform on the transform coefficients in the transform block in the horizontal and vertical directions by using the determined transform function.

[0093] The predictor 540 may include an intra predictor 542 and an inter predictor 544. The intra predictor 542 is activated when the prediction type of the current block is intra prediction, and the inter predictor 544 is activated when the prediction type of the current block is inter prediction.

[0094] The intra predictor 542 determines an intra prediction mode of a current block among a plurality of intra prediction modes according to a syntax element of the intra prediction mode extracted from the entropy decoder 510. The intra predictor 542 also predicts the current block by using neighboring reference pixels of the current block according to the intra prediction mode.

[0095] The inter predictor 544 determines a motion vector of a current block and a reference picture to which the motion vector refers by using a syntax element for the inter prediction mode extracted from the entropy decoder 510 .

[0096] The adder 550 reconstructs the current block by adding the residual block output from the inverse transformer 530 and the prediction block output from the inter predictor 544 or the intra predictor 542. When intra prediction is performed on a block to be decoded later, pixels within the reconstructed current block are used as reference pixels.

[0097] The loop filter unit 560 as a loop filter may include a deblocking filter 562, an SAO filter 564, and an ALF 566. The deblocking filter 562 performs deblocking filtering on the boundary between the reconstructed blocks in order to remove block artifacts that occur due to block unit decoding. The SAO filter 564 and the ALF 566 perform additional filtering on the reconstructed blocks after deblocking filtering in order to compensate for the difference between the reconstructed pixels and the original pixels due to lossy encoding. The filter coefficients of the ALF are determined by using information about the filter coefficients decoded from the bitstream.

[0098] The reconstructed blocks filtered by the deblocking filter 562, the SAO filter 564, and the ALF 566 are stored in the memory 570. When all blocks in one picture are reconstructed, the reconstructed picture can be used as a reference picture for inter-frame prediction of blocks in a picture to be encoded later.

[0099] In some embodiments, the present disclosure relates to encoding and decoding a video image as described above. More specifically, the present disclosure provides a video encoding method and apparatus for reconstructing a current block by rearranging an initial prediction signal when the prediction signal of the current block is generated from a reconstructed region in a current frame using a block vector.

[0100] The following embodiments may be performed by the predictor 120 in the video encoding apparatus. The following embodiments may also be performed by the predictor 540 in the video decoding apparatus.

[0101] During encoding of the current block, the video encoding device may generate signaling information associated with the present embodiment in terms of optimizing rate distortion. The video encoding device may encode the signaling information using an entropy encoder 155 and send the encoded signaling information to a video decoding device. The video decoding device may use an entropy decoder 510 to decode the signaling information associated with decoding of the current block from a bitstream.

[0102] In the following description, the term 'target block' may be used interchangeably with a current block or a coding unit (CU), or may refer to a certain region of a coding unit.

[0103] In addition, a flag value of true indicates that the flag is set to 1. In addition, a flag value of false indicates that the flag is set to 0.

[0104] I. Intra-Block Copy (IBC)

[0105] IBC uses a block vector to copy a reference block in the same frame and performs intra-frame prediction of the current block to generate a prediction block for the current block.

[0106] The video encoding device performs block matching to derive an optimal block vector. Here, the block vector represents the displacement from the current block to the reference block. In order to increase the coding efficiency, the video encoding device may not send the block vector as it is, but may split it into a block vector predictor (BVP) and a block vector difference (BVD), encode the BVP and BVD, and then send the BVP and BVD to the video decoding device.

[0107] In the following, BVD and block vectors are considered to have the same spatial resolution.

[0108] In terms of utilizing block vectors, IBC has the characteristics of inter-frame prediction. Therefore, IBC can be classified into IBC merge / skip mode and IBC AMVP mode.

[0109] In the case of IBC merge / skip mode, the video encoding device first constructs an IBC merge list. In terms of optimizing coding efficiency, the video encoding device can select a block vector of one candidate included in the candidate in the IBC merge list, and use the selected block vector as a block vector predictor (BVP). The video encoding device determines a merge index indicating the selected block vector. However, the video encoding device does not generate a BVD. The video encoding device encodes the merge index and sends it to the video decoding device. The IBC merge list can be constructed in the same way by the video encoding device and the video decoding device. After decoding the merge index, the video decoding device can use the merge index to generate a block vector from the IBC merge list.

[0110] In the case of the IBC skip mode, the video encoding apparatus performs block vector transmission using the same method as the IBC merge mode, but does not transmit a residual block corresponding to the difference between the current block and the predicted block.

[0111] When in IBC AMVP mode, the video encoding device determines a block vector and constructs an IBC AMVP list in terms of optimizing coding efficiency. The video encoding device determines a candidate index indicating one of the candidate block vectors included in the IBC AMVP list as a BVP (block vector predictor). The video encoding device calculates a BVD (block vector difference) as a difference between the BVP and the block vector. Then, the video encoding device encodes the candidate index and the BVD, and transmits the candidate index and the BVD to the video decoding device.

[0112] On the other hand, the video decoding apparatus decodes the candidate index and the BVD. When obtaining the BVP indicated by the candidate index from the IBC AMVP list, the video decoding apparatus may add the BVP and the BVD to reconstruct the block vector.

[0113] The following embodiments are described with reference to a video decoding device, but may be equally or similarly implemented in a video encoding device.

[0114] II. Implementations according to the present disclosure

[0115] Figure 6 is a block diagram detailing a portion of a video decoding apparatus according to at least one embodiment of the present disclosure.

[0116] According to some embodiments, the video decoding device can determine the prediction unit and the transformation unit, and for the current block corresponding to the determined unit, perform prediction and inverse transformation by using the determined prediction technology and prediction mode to finally generate a reconstructed block of the current block. Figure 6 The operations shown in FIG. 5 can be performed by the inverse transformer 530, the predictor 540, and the adder 550 of the video decoding device. Figure 6 The same operation shown in FIG. 1 can be performed by the inverse transformer 165, the picture splitter 110, the predictor 120, and the adder 170 of the video encoding device. In this case, the video decoding device uses the encoding information parsed from the bitstream, but the video encoding device can use the encoding information set from a higher level in terms of minimizing rate distortion. Hereinafter, for convenience, the embodiment is described with the video decoding device as the center.

[0117] like Figure 5 As shown in FIG. 5 , the predictor 540 includes an intra-frame predictor 542 and an inter-frame predictor 544, depending on the prediction technique, but as shown in FIG. Figure 6 As shown in , the predictor 540 may include all or part of a prediction unit determiner 602 , a prediction technique determiner 604 , a prediction mode determiner 606 , and a prediction executor 608 .

[0118] The prediction unit determiner 602 determines a prediction unit (PU). The prediction technique determiner 604 determines a prediction technique, such as intra prediction, inter prediction, or intra block copy (IBC) mode, palette mode, etc., with respect to the prediction unit. The prediction mode determiner 606 determines a detailed prediction mode for the prediction technique. The prediction executor 608 generates a prediction block of the current block according to the determined prediction mode.

[0119] The inverse transformer 530 includes a transform unit determiner 610 and an inverse transform performer 612. The transform unit determiner 610 determines a transform unit (TU) in response to an inverse quantization signal of a current block, and the inverse transform performer 612 inversely transforms the transform unit represented by the inverse quantization signal to generate a residual signal.

[0120] The adder 550 sums the predicted block and the residual signal to generate a reconstructed block. The reconstructed block is stored in a memory and can be used to predict other blocks in the future.

[0121] The prediction unit determined by the prediction unit determiner 602 may become one of the sub-blocks in the current block or the sub-blocks split from the current block. In this case, the prediction unit of the chrominance component may correspond in size to the prediction unit of the luma component depending on the color format. Alternatively, the prediction units of the luma component and the chrominance component may be determined separately, and prediction may be performed for the prediction unit of the chrominance component.

[0122] The prediction technique determiner 604 determines a prediction technique for a prediction unit. As described above, the prediction technique may be one of inter prediction, intra prediction, IBC mode, and palette mode.

[0123] In one embodiment, if the prediction technique of the current block is not intra prediction, the video decoding device parses the 1-bit flag information. If the parsed flag indicates the skip mode, the video decoding device may determine the prediction mode of the current block as the inter-prediction merge mode or the IBC merge mode. The video decoding device may also use the predicted signal as the reconstructed signal and skip the inverse transform.

[0124] On the other hand, if the parsed flag does not indicate the skip mode for the current block, the prediction technique determiner 604 may determine one of the prediction techniques (such as inter prediction, intra prediction, IBC mode, palette mode, etc.) by parsing a series of 1-bit flags with respect to the prediction technique of the current block. Hereinafter, the flag indicating whether the IBC mode is applied is referred to as an IBC flag.

[0125] For example, if skip mode is not applied to the current block and it is determined as inter prediction or IBC mode, the prediction mode determiner 606 may parse a 1-bit flag and determine whether the prediction mode of the current block is merge mode or AMVP mode based on the parsed flag.

[0126] If the prediction mode of the current block is the IBC mode, the prediction mode determiner 606 may parse a 1-bit flag and determine whether to use a mode for rearranging the initial prediction signal (hereinafter referred to as "rearrangement prediction mode") to generate a final prediction signal based on the parsed flag, hereinafter referred to as a "rearrangement flag". First, the video decoding apparatus generates an initial prediction block of the current block by using a block vector. Next, if the rearrangement flag is true and the rearrangement prediction mode is used, the video decoding apparatus may generate a final prediction block by splitting the initial prediction block into a plurality of sub-blocks and rearranging the sub-block positions.

[0127] The following describes the operation of the prediction executor 608 when the prediction technique of the current block is the IBC mode and the prediction mode is the permutation prediction mode. Hereinafter, the video decoding apparatus refers to the prediction executor 608.

[0128] Because the prediction technology of the current block is the IBC mode, the video decoding device can generate a block vector in the IBC merge mode as described above or generate a unidirectional block vector according to the IBC AMVP mode. In addition, the video decoding device can generate a bidirectional block vector according to the IBC merge mode / IBCAMVP mode. For example, one block vector can be generated according to the IBC merge mode, and another block vector can be generated according to the IBC AMVP mode. Optionally, the video decoding device can generate a block vector only in the IBC merge mode or only in the IBC AMVP mode. As described above, when in the IBC merge mode, the video encoding device sends a merge index with a signal. In addition, when in the IBC AMVP mode, the video encoding device can send a candidate index and a block vector difference with a signal. The video decoding device can parse the sent parameters and generate a block vector by using the parsed parameters.

[0129] As an example, the video encoding apparatus and the video decoding apparatus may construct a candidate block vector list by using motion information of a reconstructed block in a spatial neighborhood of the current block, motion information in a block encoded before the current block in a coding order, zero motion information, etc., such as Figure 4 When in IBC merge mode, the video decoding device may generate a block vector by using the merge index. When in IBC AMVP mode, the video decoding device may use the candidate index to derive a block vector predictor, and then compensate the block vector difference to thereby generate a block vector. In this case, Figure 4 Some positions of the reconstructed blocks in the spatial neighborhood of the current block illustrated in may be omitted or changed.

[0130] Figure 7The present invention is a flowchart of a method for predicting a current block based on an IBC mode, performed by a video decoding device according to at least one embodiment of the present disclosure.

[0131] The video decoding apparatus decodes an IBC flag from a bitstream (S700). Here, as described above, the IBC flag (IBC_flag) is adapted to indicate whether the IBC mode is applied.

[0132] The video decoding apparatus checks the IBC flag (S702).

[0133] If the IBC flag is true (Yes in S702 ), the video decoding apparatus decodes a reorder flag from the bitstream ( S704 ).

[0134] The video decoding apparatus checks a reorder flag (S706). Here, the reorder flag (reorder_flag) indicates whether the reorder prediction mode is to be enabled or disabled.

[0135] If the rearrangement flag is true (Yes in S706), the video decoding apparatus decodes a horizontal flag from the bitstream (S708). Here, the horizontal flag (hor_flag) indicates whether the current block is to be split horizontally or vertically.

[0136] The video decoding apparatus checks a level flag (S710).

[0137] If the horizontal flag is true (yes in S710), the video decoding apparatus decodes a split index (split_idx) for horizontally splitting the current block according to the rearrangement prediction (S712). Here, the split index indicates one of the preset ratios of the sub-block relative to the horizontally split sub-block. The sub-block ratio according to the split index may be a sub-block ratio as shown in Table 1.

[0138] [Table 1]

[0139] split_idx Sub-block ratio 0 1:1 1 1:2:1 2 1:3 3 3:1

[0140] On the other hand, if the horizontal flag is false (No in S710), the video decoding apparatus decodes a split index (split_idx) for vertically splitting the current block according to the rearrangement prediction (S714). Here, the split index indicates one of the ratios of the preset sub-blocks relative to the sub-blocks of the vertical split. The sub-block ratio according to the split index may be a sub-block ratio as shown in Table 1.

[0141] The video decoding apparatus generates a prediction block of the current block based on the rearrangement prediction mode (S716).

[0142] On the other hand, if the IBC flag is false (No in S702 ), the video decoding apparatus generates a prediction block of the current block based on another prediction technique such as intra prediction, inter prediction, or the like.

[0143] (S720).

[0144] In addition, if the reorder flag is false (No in S706), the video decoding apparatus generates a prediction block of the current block according to a conventional IBC mode that does not use a reorder prediction mode (S730).

[0145] In one example, the size (or aspect ratio) of the current block may implicitly determine the split direction of the sub-blocks used to perform the rearrangement prediction. This section describes the case where the current block prediction technique is the IBC mode and the current block is predicted according to the rearrangement prediction mode. With respect to the current block having a size of W×H (where W is the width and H is the height), if W>H, the video decoding apparatus may generate a vertically split sub-block, such as Figure 8 Optionally, if W<H, the video decoding device may generate sub-blocks split in the horizontal direction, such as Fig. 9 as shown in .

[0146] In one example, if the split direction of the sub-block used to perform permutation prediction is implicitly determined based on the size of the current block, or explicitly determined based on the parsed horizontal flag (e.g. Figure 7 ), then the sub-block ratio (i.e., the split index) may be implicitly determined based on the aspect ratio of the current block. Alternatively, the sub-block ratio may be explicitly determined based on the split index that is signaled and parsed, such as Figure 7 As described above, the sub-block ratios according to the splitting index can be shown in Table 1.

[0147] This section describes the step of generating a prediction block for the current block (S716), wherein the split direction of the sub-blocks used to perform the permutation prediction is implicitly determined according to the size of the current block, or explicitly determined according to the parsed horizontal flag, as in Figure 7 As shown in , and the subblock ratio is implicitly or explicitly determined. After generating a block vector of the current block based on the IBC merge mode or the IBC AMVP mode, the video decoding apparatus may perform prediction of the current block based on the rearrangement prediction mode using the generated block vector as follows.

[0148] In one example, when the current block is implicitly or explicitly split vertically and the sub-block ratio is implicitly or explicitly determined to be 1:1, the video decoding apparatus first generates an initial prediction block by using a block vector, such as Fig.10As shown in . The video decoding device vertically splits the initial prediction block to generate two sub-blocks. The video decoding device may then perform rearrangement to change the order of the two sub-blocks to generate a final prediction block of the current block.

[0149] As another example, if the current block is implicitly or explicitly vertically partitioned and the sub-block ratio is implicitly or explicitly determined to be 1:2:1, the video decoding apparatus may first generate an initial prediction block by using a block vector, such as Fig.11 As shown in . The video decoding device vertically splits the initial prediction block to generate three sub-blocks. The video decoding device may then perform rearrangement to change the order of the three sub-blocks to generate a final prediction block of the current block. Fig.11 In the example of , among the three sub-blocks, the rearranged blocks are sub-block 1 and sub-block 3 located on either side of the initial prediction block. Sub-block 2 located at the center may not be rearranged.

[0150] As another example, if the current block is implicitly or explicitly split vertically and the sub-block ratio is implicitly or explicitly determined to be 1:3, the video decoding device first generates an initial prediction block by using a block vector, such as Fig.12 As shown in . The video decoding device vertically splits the initial prediction block to generate two sub-blocks. The video decoding device may then perform rearrangement to change the order of the two sub-blocks to generate a final prediction block of the current block.

[0151] As another example, if the current block is implicitly or explicitly vertically partitioned and the sub-block ratio is implicitly or explicitly determined to be 3:1, the video decoding device may first generate an initial prediction block by using a block vector, such as Fig.13 As shown in . The video decoding device vertically splits the initial prediction block to generate two sub-blocks. The video decoding device may then perform rearrangement to change the order of the two sub-blocks to generate a final prediction block of the current block.

[0152] In addition, if the current block is implicitly or explicitly split horizontally and the sub-block ratio is implicitly or explicitly determined, the video decoding device may first generate an initial prediction block by using a block vector. The video decoding device horizontally splits the initial prediction block to generate sub-blocks. Then, the video decoding device may perform rearrangement to change the order of the sub-blocks to generate a final prediction block of the current block.

[0153] Fig.14 is a flowchart of a method for predicting a current block based on an IBC mode, performed by a video decoding device according to another embodiment of the present disclosure.

[0154] and Figure 7 Compared with the flowchart, Fig.14 The instance only includes the case where IBC mode is applied and the reorder flag is true.

[0155] The video decoding apparatus decodes a 1:1 flag from a bitstream (S1400). Here, the 1:1 flag (1:1_flag) indicates whether the split sub-block ratio is 1:1 or 1:1:1:1 in the horizontal or vertical direction. For example, if the 1:1 flag is true, the sub-block ratio is 1:1, and if the 1:1 flag is false, the sub-block ratio may be 1:1:1:1.

[0156] The video decoding device checks the 1:1 flag (S1402).

[0157] If the 1:1 flag is true (Yes in S1402 ), the video decoding apparatus may perform the following steps ( S1404 to S1410 ).

[0158] The video decoding apparatus decodes a half flag from the bitstream (S1404). Here, the half flag (half_flag) indicates whether the sub-block ratio in the horizontal or vertical direction is 1:1 or 1:2:1. For example, if the half flag is true, the sub-block ratio is 1:1, and if the half flag is false, the sub-block ratio may be 1:2:1.

[0159] The video decoding apparatus decodes a horizontal flag from the bitstream (S1406). Here, the horizontal flag (hor_flag) indicates whether the current block is split horizontally or vertically.

[0160] The video decoding apparatus generates a sub-block of the current block based on the half flag and the horizontal flag (S1408).

[0161] The video decoding apparatus generates a prediction block of a current block based on a rearrangement prediction mode (S1410).

[0162] For example, if the half flag is true and the horizontal flag is false, the video decoding device may perform reorder prediction to generate a final prediction block for the current block, such as Fig.10 Optionally, if the half flag is false and the horizontal flag is false, the video decoding device may perform a reorder prediction to generate a final prediction block of the current block, such as Fig.11 as shown in .

[0163] If the 1:1 flag is false (No in S1402 ), the video decoding apparatus may perform the following steps ( S1420 to S1426 ).

[0164] The video decoding apparatus decodes a horizontal flag from a bitstream (S1420). Here, the horizontal flag (hor_flag) indicates whether the current block is split horizontally or vertically.

[0165] The video decoding apparatus generates sub-blocks of the current block based on the horizontal flag (S1422). The video decoding apparatus may split the current block to generate sub-blocks based on the value of the horizontal flag, such as Fig.15 as shown in .

[0166] The video decoding apparatus decodes a copy index from the bitstream (S1424). Here, the copy index (copy_idx) indicates which sub-blocks are to be rearranged. If two sub-blocks are rearranged, the rearranged blocks according to the copy index can be represented as shown in Table 2.

[0167] [Table 2]

[0168] copy_idx Rearrange blocks 0 A. B 1 A.C 2 C.D 3 B.D

[0169] The video decoding apparatus generates a prediction block of the current block based on the copy index (S1426).

[0170] If the current block is implicitly or explicitly split horizontally or vertically, the video decoding device splits the initial prediction block into sub-blocks and rearranges the split sub-blocks. The video decoding device may then apply filtering to samples adjacent to the boundary between the sub-blocks to generate a final prediction signal, as shown in the following embodiments.

[0171] In one example, after performing the rearrangement of the sub-blocks relative to the initial prediction block, the video decoding device can generate a final prediction signal as shown in Figures 16A and 16B by applying a filter 'f' to the prediction signal adjacent to the internal boundary to generate a signal of the sub-block boundary. In this case, the filter 'f' can be a filter such as a median filter, but can be a fixed filter with preset coefficients. Alternatively, the video encoding device can send information indicating one of the preset filters with a signal, and the video decoding device can parse the information sent with the signal to determine the filter, and then the determined filter can be used to perform filtering on the boundary between the sub-blocks. At this time, the video decoding device can perform filtering on the boundary between the sub-blocks by using the prediction signal of the area adjacent to the boundary between the sub-blocks. In the example of Figure 16A, the initial prediction block is split into two sub-blocks with a ratio of 1:1. In the example of Figure 16B, the initial prediction block is split into three sub-blocks with a ratio of 1:2:1.

[0172] According to another example, after performing the rearrangement of the sub-blocks for the initial prediction block, the video decoding device compares the value of the prediction signal at each sub-block boundary with the value of the prediction signal adjacent to the internal boundary. If the difference between the two adjacent sample values ​​is less than or equal to a certain threshold value "t", the video decoding device can generate the final prediction signal shown in Figures 17A and 17B by applying the filter 'f' to the prediction signal adjacent to the internal boundary to generate the signal of the sub-block boundary. On the other hand, if the difference between the two adjacent sample values ​​is greater than a certain threshold value "t", the video decoding device can prevent the filter from being applied to the prediction signal adjacent to the internal boundary. In this case, the threshold value can be a predefined value based on the agreement between the video encoding device and the video decoding device. Alternatively, the threshold value can be implicitly determined based on the bit depth of the input video. In this case, the filter f can be a filter such as a median filter, but can be a fixed filter with preset coefficients. Alternatively, the video encoding device can send information indicating one of the preset filters with a signal, and the video decoding device can parse the information sent with the signal to determine the filter, and then the determined filter can be used to perform filtering on the boundary between the sub-blocks. In this case, the video decoding apparatus may perform filtering of the boundary between the sub-blocks by using a prediction signal of a region adjacent to the boundary between the sub-blocks.

[0173] In the example of FIG. 17A , the initial prediction block is split into two sub-blocks with a ratio of 1:1. At this time, because |a0-b0|>t is satisfied, the video decoding device may not apply filtering to the boundary between a0 and b0. Further, in the example of FIG. 17B , the initial prediction block is split into three sub-blocks with a ratio of 1:2:1. At this time, because |a0-b0|>t and |cH-dH|>t are satisfied, the video decoding device may not apply filtering to the boundary between a0 and b0 and the boundary between cH and dH.

[0174] Fig.18 The present invention is a flowchart of a method for predicting a current block based on an IBC mode, performed by a video encoding apparatus according to at least one embodiment of the present disclosure.

[0175] Fig.18 Examples include cases where the IBC mode is applied.

[0176] The video encoding apparatus generates an initial prediction block of a current block based on the IBC mode ( S1800 ).

[0177] The video encoding apparatus may generate a block vector of the current block based on the IBC merge mode or the IBC AMVP mode, and may then use the generated block vector to generate an initial prediction block from a reconstructed region in the current frame.

[0178] The video encoding apparatus obtains a split direction of the current block (S1802). Here, the split direction indicates horizontal split or vertical split.

[0179] In one example, in terms of rate-distortion optimization, the video encoding device determines a horizontal flag. Here, the horizontal flag indicates whether the split direction is a horizontal split or a vertical split. The video encoding device can set the split direction based on the horizontal flag. Subsequently, the video encoding device can encode and then send a signal with the horizontal flag to the video decoding device.

[0180] As another example, the video encoding device may implicitly determine the split direction based on the size of the current block.

[0181] The video encoding apparatus obtains a ratio of the sub-block to the current block (S1804).

[0182] In one example, in terms of rate-distortion optimization, the video encoding device determines a split index. Here, the split index indicates one of the preset sub-block ratios (e.g., Table 1). The video encoding device may determine the ratio of the sub-blocks based on the split index. Subsequently, the video encoding device may encode the split index and send it to the video decoding device with a signal.

[0183] As another example, the video encoding device may implicitly determine the scale of the sub-block based on the aspect ratio of the current block.

[0184] The video encoding apparatus may split the initial prediction block into sub-blocks based on the split direction and the ratio of the sub-blocks ( S1806 ).

[0185] The video encoding apparatus may rearrange the sub-blocks to generate a final prediction block of the current block ( S1808 ).

[0186] The video encoding apparatus may apply a preset filter to samples adjacent to a boundary between the rearranged subblocks.

[0187] Based on the initial prediction block and the final prediction block, the video encoding device determines a rearrangement flag (S1810). Here, the rearrangement flag indicates whether the sub-block will be rearranged. In terms of rate-distortion optimization, the video encoding device can determine the rearrangement flag by comparing the initial prediction block with the final prediction block. For example, if the initial prediction block is optimal, the video encoding device sets the rearrangement flag to false. On the other hand, if the final prediction block is optimal, the video encoding device can set the rearrangement flag to true.

[0188] The video encoding apparatus encodes the reorder flag (S1812).

[0189] As described above, if a split flag indicating a split direction is determined in terms of rate-distortion optimization, the video encoding device may further encode the split flag. In addition, if a split index indicating a ratio of subblocks is determined in terms of rate-distortion optimization, the video encoding device may encode the split index.

[0190] Although the steps in each flowchart are described as being performed sequentially, these steps merely illustrate the technical concepts of some embodiments of the present disclosure. Therefore, a person of ordinary skill in the art to which the present disclosure belongs can perform the steps by changing the order described in each figure or by performing two or more steps in parallel. Therefore, the steps in each flowchart are not limited to the time series order shown.

[0191] It should be understood that the above description presents illustrative embodiments that can be implemented in different other ways. The functions described in some embodiments can be implemented by hardware, software, firmware and / or a combination thereof. It should also be understood that the functional components described in this disclosure are identified with "... units" to strongly emphasize the possibility of their independent implementation.

[0192] At the same time, the various methods or functions described in some embodiments may be implemented as instructions stored in a non-transitory recording medium that can be read and executed by one or more processors. For example, the non-transitory recording medium may include various types of recording devices, in which data is stored in a form readable by a computer system. For example, the non-transitory recording medium may include 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).

[0193] Although the embodiments of the present disclosure have been described for illustrative purposes, however, those of ordinary skill in the art to which the present disclosure belongs should recognize that various modifications, additions, and substitutions are possible without departing from the concept and scope of the present disclosure. Therefore, for the sake of brevity and clarity, the embodiments of the present disclosure have been described. The scope of the technical concept of the embodiments of the present disclosure is not limited by the diagrams. Therefore, those of ordinary skill in the art to which the present disclosure belongs should understand that the scope of the present disclosure should not be limited by the embodiments explicitly described above, but by the claims and their equivalents.

[0194] (reference number)

[0195] 120: Predictor

[0196] 540: Predictor

[0197] 602: Prediction unit determiner

[0198] 604: Prediction Technology Determiner

[0199] 606: Prediction Mode Determiner

[0200] 608: Predictive Executor.

[0201] CROSS-REFERENCE TO RELATED APPLICATIONS

[0202] This application claims priority to and the benefit of Korean Patent Application No. 10-2022-0099353, filed on August 9, 2022, and Korean Patent Application No. 10-2023-0089974, filed on July 11, 2023, the entire contents of each of which are incorporated herein by reference.

Claims

1. A method for reconstructing a current block by a video decoding device, the method comprising: Obtaining a split direction of the current block, where the split direction indicates horizontal splitting or vertical splitting; Obtaining a ratio of a sub-block relative to the current block; generating an initial prediction block of the current block according to an intra block copy (IBC) mode; Splitting the initial prediction block into sub-blocks according to the splitting direction and the ratio of the sub-blocks; as well as A final prediction block of the current block is generated by rearranging the sub-blocks.

2. The method according to claim 1, further comprising: decoding from a bitstream a reordering flag indicating whether the sub-blocks are to be reordered; as well as Checking the reorder flag, Wherein, when the rearrangement flag is true, obtaining the split direction is performed by generating the final prediction block of the current block.

3. The method according to claim 2, further comprising, when the reorder flag is false: A prediction block of the current block is generated according to the IBC mode.

4. The method according to claim 2, further comprising: decoding an IBC flag from a bitstream, the IBC flag indicating whether an IBC mode is applied; as well as Check the IBC logo, Wherein, when the IBC flag is true, the rearrangement flag is decoded.

5. The method according to claim 1, wherein: Obtaining the splitting direction includes: Decoding a horizontal flag indicating whether the splitting direction is the horizontal splitting or the vertical splitting from a bit stream; and The splitting direction is set according to the horizontal mark.

6. The method according to claim 1, wherein: Obtaining the splitting direction includes: The split direction is implicitly determined based on the size of the current block.

7. The method according to claim 1, wherein: Obtaining the proportion of the sub-blocks includes: decoding a splitting index indicating one of the preset ratios of the sub-blocks from a bitstream; and The ratio of the sub-blocks is determined according to the split index.

8. The method according to claim 1, wherein: Obtaining the proportion of the sub-blocks includes: The scale of the sub-blocks is implicitly determined based on the aspect ratio of the current block.

9. The method according to claim 1, wherein: Generating the initial prediction block comprises: generating a block vector of the current block based on an IBC merge mode or an IBC advanced motion vector prediction (AMVP) mode; and The initial prediction block is generated from a reconstructed area in a current frame using the block vector.

10. The method according to claim 1, wherein: Generating the final prediction block comprises: A preset filter is applied to samples adjacent to a boundary between the rearranged sub-blocks.

11. The method according to claim 10, wherein: Generating the final prediction block comprises: When a difference between two sample values ​​adjacent to a boundary between the rearranged sub-blocks is less than or equal to a preset threshold, the preset filter is applied, and when the difference between the two sample values ​​is greater than the preset threshold, the preset filter is prevented from being applied.

12. A method for encoding a current block by a video encoding device, the method comprising: generating an initial prediction block of the current block according to an intra block copy (IBC) mode; Obtaining a split direction of the current block, where the split direction indicates horizontal splitting or vertical splitting; Obtaining a ratio of a sub-block relative to the current block; Splitting the initial prediction block into sub-blocks based on the splitting direction and the ratio of the sub-blocks; as well as A final prediction block of the current block is generated by rearranging the sub-blocks.

13. The method according to claim 12, further comprising: determining a reordering flag indicating whether the sub-block is to be reordered based on the initial prediction block and the final prediction block; as well as The reorder flag is encoded.

14. The method according to claim 12, wherein: Obtaining the splitting direction comprises: determining a horizontal flag indicating whether the splitting direction is the horizontal splitting or the vertical splitting; and The splitting direction is set according to the horizontal mark.

15. The method according to claim 14, further comprising: The level flag is encoded.

16. The method according to claim 12, wherein: Obtaining the proportion of the sub-blocks includes: determining a splitting index indicative of one of the preset ratios of the sub-blocks; and The ratio of the sub-blocks is determined according to the split index.

17. The method according to claim 16, further comprising: The split index is encoded.

18. A computer-readable recording medium storing a bit stream generated by a video encoding method, the video encoding method comprising: generating an initial prediction block for the current block according to an intra block copy (IBC) mode; Obtaining a split direction of the current block, where the split direction indicates horizontal splitting or vertical splitting; Obtaining a ratio of a sub-block relative to the current block; Splitting the initial prediction block into sub-blocks based on the splitting direction and the ratio of the sub-blocks; as well as A final prediction block of the current block is generated by rearranging the sub-blocks.

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