CN117461312A - Video encoding and decoding method and device - Google Patents

Video encoding and decoding method and device Download PDF

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Publication number
CN117461312A
CN117461312A CN202280041485.1A CN202280041485A CN117461312A CN 117461312 A CN117461312 A CN 117461312A CN 202280041485 A CN202280041485 A CN 202280041485A CN 117461312 A CN117461312 A CN 117461312A
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China
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intra
prediction
mode
block
intra prediction
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Chinese (zh)
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朴胜煜
许镇
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Hyundai Motor Co
Kia Corp
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Hyundai Motor Co
Kia Corp
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Priority claimed from KR1020220066258A external-priority patent/KR20220167219A/en
Application filed by Hyundai Motor Co, Kia Corp filed Critical Hyundai Motor Co
Priority claimed from PCT/KR2022/007767 external-priority patent/WO2022260341A1/en
Publication of CN117461312A publication Critical patent/CN117461312A/en
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Abstract

A video encoding and decoding method and apparatus are provided. The video decoding method according to the present disclosure may include the steps of: generating an intra prediction mode list based on intra prediction modes of neighboring blocks adjacent to the current block; selecting at least three intra-prediction modes from the intra-prediction mode list based on the number of intra-prediction modes occurring in the intra-prediction mode list being three or more; generating at least three prediction blocks based on at least three intra prediction modes; and generating a prediction block of the current block by means of a weighted average of at least three prediction blocks.

Description

Video encoding and decoding method and device
Technical Field
The present invention relates to a video encoding/decoding method and apparatus, and more particularly, to a video encoding/decoding method and apparatus for generating a histogram (HoM) of modes using intra prediction modes of neighboring blocks adjacent to a current block and deriving intra prediction modes of the current block from the histogram.
Background
The statements in this section merely provide background information related to the present embodiments and may not necessarily constitute prior art.
Because video data has a large amount of data compared to audio or still picture data, the video data requires a large amount of hardware resources (including memory) to store or transmit the video data without performing processing for compression.
Thus, encoders are commonly used to compress and store or transmit video data. The decoder receives compressed video data, decompresses the received compressed video data, and reproduces the decompressed video data. Video compression techniques include h.264/AVC, high Efficiency Video Coding (HEVC), and Versatile Video Coding (VVC), which have improved coding efficiency of about 30% or more compared to HEVC.
However, since the picture size, resolution, and frame rate gradually increase, the amount of data to be encoded also increases. Thus, new compression techniques are needed that provide higher coding efficiency and improved picture enhancement than existing compression techniques.
Intra prediction is a prediction technique that allows only spatial reference, and refers to a method of predicting a current block by referring to blocks that have been reconstructed around the block to be currently encoded. The encoder transmits intra prediction mode information of a block currently to be encoded to the decoder. A technique for deriving an intra prediction mode in a Decoder (Decoder-side Intra Mode Derivation: DIMD) is a technique in which an encoder derives an intra prediction mode in a decoding process instead of transmitting intra prediction mode information to the Decoder. Since the DIMD derives the intra prediction mode of the current block without receiving intra prediction mode information from the decoder, coding efficiency is improved, but complexity in the decoder needs to be reduced.
Disclosure of Invention
It is an object of the present disclosure to provide a method and apparatus for deriving an intra prediction mode based on intra prediction modes of neighboring blocks adjacent to a current block.
Further, it is an object of the present disclosure to provide a method and apparatus for deriving an intra prediction mode without an encoder parsing intra prediction mode information to a decoder.
Furthermore, it is an object of the present disclosure to provide methods and apparatus for deriving intra-prediction modes based on techniques for deriving intra-prediction modes in a Decoder (Decoder-side Intra Mode Derivation: DIMD).
Further, it is an object of the present disclosure to provide a method and apparatus for determining an assigned weight value to increase the accuracy of the weight value in consideration of intra prediction modes of all neighboring blocks.
Further, it is an object of the present disclosure to provide methods and apparatus for limiting DIMD flag resolution under certain conditions.
Further, it is an object of the present disclosure to provide a method and apparatus for deriving an intra prediction mode of a chroma block based on a mode of a luma block.
Further, it is an object of the present disclosure to provide a method and apparatus for improving video encoding/decoding efficiency.
Further, it is an object of the present disclosure to provide a recording medium storing a bitstream generated by using the video encoding/decoding method or the video encoding/decoding apparatus of the present disclosure.
Further, it is an object of the present disclosure to provide a method and apparatus for transmitting a bitstream generated by using the video encoding/decoding method or apparatus of the present disclosure.
According to the present invention, a video decoding method includes: an intra prediction mode list is generated based on intra prediction modes of neighboring blocks adjacent to the current block. The video decoding method further includes: at least three intra-prediction modes are selected from the intra-prediction mode list based on the number of intra-prediction modes occurring in the intra-prediction mode list being three or more. The video decoding method also includes: at least three prediction blocks are generated based on at least three intra prediction modes. The video decoding method further comprises: the prediction block of the current block is generated by performing a weighted average on at least three prediction blocks.
In the video decoding method according to the present invention, the at least three intra prediction modes are three intra prediction modes having the highest occurrence frequency in the intra prediction mode list.
In the video decoding method according to the present invention, generating a prediction block of a current block by performing weighted average on at least three prediction blocks includes: the method includes assigning weight values determined based on highest occurrence frequencies of at least three intra prediction modes to at least three prediction blocks, and adding the at least three prediction blocks to which the weight values are assigned.
In the video decoding method according to the present invention, the video decoding method further includes: at least two intra prediction modes having the highest occurrence frequency are selected from among the at least three intra prediction modes based on the absence of a plane mode among the at least three intra prediction modes. The video decoding method also includes: at least three prediction blocks are generated based on at least two intra prediction modes and a plane mode. The video decoding method further comprises: the prediction block of the current block is generated by performing a weighted average on at least three prediction blocks.
In the video decoding method according to the present invention, the video decoding method further includes: one or two intra-prediction modes are selected from the default mode set based on the number of intra-prediction modes present in the intra-prediction mode list being one or two. The video decoding method also includes: at least three prediction blocks are generated based on intra prediction modes occurring in the intra prediction mode list and based on one or two intra prediction modes selected from a default mode set. The video decoding method further comprises: the prediction block of the current block is generated by performing a weighted average on at least three prediction blocks.
In the video decoding method according to the present invention, one or two intra prediction modes selected from the default mode set do not overlap with intra prediction modes appearing in the intra prediction mode list.
In the video decoding method according to the present invention, the video decoding method further includes: one or two intra-prediction modes are selected from the intra-prediction mode list based on the number of intra-prediction modes present in the intra-prediction mode list being one or two. The video decoding method also includes: one or two prediction blocks are generated based on one or two intra prediction modes. The video decoding method further comprises: the prediction block of the current block is generated by performing a weighted average on one or both prediction blocks.
In the video decoding method according to the present invention, the video decoding method further includes: information indicating whether the intra prediction mode is derived in the decoder is obtained based on the presence of at least one directional mode among intra prediction modes appearing in the intra prediction mode list or the presence of intra prediction modes as at least one directional mode among neighboring blocks.
In the video decoding method according to the present invention, the video decoding method further includes: information indicating whether the intra prediction mode is derived in the decoder is obtained based on whether the frequency at which the intra prediction mode is derived in the decoder at a neighboring block at a specific position or the neighboring block adjacent to the current block exceeds any value.
In the video decoding method according to the present disclosure, the video decoding method further includes: information indicating whether the intra prediction mode is derived in the decoder is obtained based on the intra prediction mode having the highest occurrence frequency in the intra prediction mode list being different from any mode in the MPM (most probable mode) list.
According to the present invention, a video encoding method includes: an intra prediction mode list is generated based on intra prediction modes of neighboring blocks adjacent to the current block. The video encoding method further includes: at least three intra-prediction modes are selected from the intra-prediction mode list based on the number of intra-prediction modes occurring in the intra-prediction mode list being three or more. The video encoding method also includes: at least three prediction blocks are generated based on at least three intra prediction modes. The video encoding method further comprises: the prediction block of the current block is generated by performing a weighted average on at least three prediction blocks.
In the video encoding method according to the present invention, the at least three intra prediction modes are three intra prediction modes having the highest occurrence frequency in the intra prediction mode list.
In the video encoding method according to the present invention, generating a prediction block of a current block by performing weighted average on at least three prediction blocks includes: the method includes assigning weight values determined based on highest occurrence frequencies of at least three intra prediction modes to at least three prediction blocks, and adding the at least three prediction blocks to which the weight values are assigned.
In the video encoding method according to the present disclosure, the video encoding method further includes: at least two intra prediction modes having the highest occurrence frequency are selected from among the at least three intra prediction modes based on the absence of the planar mode among the at least three intra prediction modes. The video encoding method also includes: at least three prediction blocks are generated based on at least two intra prediction modes and a plane mode. The video encoding method further comprises: the prediction block of the current block is generated by performing a weighted average on at least three prediction blocks.
In the video encoding method according to the present invention, the video encoding method further includes: one or two intra-prediction modes are selected from the default mode set based on the number of intra-prediction modes present in the intra-prediction mode list being one or two. The video encoding method also includes: at least three prediction blocks are generated based on intra prediction modes occurring in the intra prediction mode list and based on one or two intra prediction modes selected from a default mode set. The video encoding method further comprises: the prediction block of the current block is generated by performing a weighted average on at least three prediction blocks.
In the video encoding method according to the present invention, the video encoding method further includes: one or two intra-prediction modes are selected from the intra-prediction mode list based on the number of intra-prediction modes present in the intra-prediction mode list being one or two. The video encoding method also includes: one or two prediction blocks are generated based on one or two intra prediction modes. The video encoding method further comprises: the prediction block of the current block is generated by performing a weighted average on one or both prediction blocks.
In the video encoding method according to the present invention, the video encoding method further includes: information indicating whether the intra prediction mode is derived in the decoder is encoded based on the presence of at least one directional mode among intra prediction modes occurring in the intra prediction mode list or the presence of an intra prediction mode as at least one directional mode among neighboring blocks.
In the video encoding method according to the present disclosure, the video encoding method further includes: information indicating whether the intra prediction mode is derived in the decoder is encoded based on whether a frequency at which the intra prediction mode is derived in the decoder at a neighboring block at a specific position or the neighboring block adjacent to the current block exceeds any value.
In the video encoding method according to the present disclosure, the video encoding method further includes: information indicating whether the intra prediction mode is derived in the decoder is encoded based on the intra prediction mode having the highest occurrence frequency in the intra prediction mode list being different from any mode in the MPM (most probable mode) list.
Further, according to the present disclosure, a method of transmitting a bitstream generated by a video encoding method or a video encoding apparatus according to the present disclosure may be provided.
In addition, according to the present disclosure, a recording medium storing a bitstream generated by the video encoding method or the video encoding apparatus according to the present disclosure may be provided.
In addition, according to the present disclosure, a recording medium storing a bitstream received and decoded by a video decoding apparatus according to the present disclosure and used to reconstruct video may be provided.
In accordance with the present disclosure, a method and apparatus for deriving an intra prediction mode based on intra prediction modes of neighboring blocks adjacent to a current block may be provided.
Furthermore, a method and apparatus for deriving an intra prediction mode may be provided without an encoder parsing intra prediction mode information to a decoder.
In addition, methods and apparatus can be provided for deriving intra-prediction modes based on techniques for deriving intra-prediction modes in a Decoder (Decoder-side Intra Mode Derivation: DIMD).
Further, in accordance with the present disclosure, methods and apparatus for determining assigned weight values to increase the accuracy of the weight values taking into account intra prediction modes of all neighboring blocks may be provided.
Further, in accordance with the present disclosure, methods and apparatus for restricting DIMD flag resolution under certain conditions may be provided.
Further, in accordance with the present disclosure, methods and apparatus for deriving intra prediction modes of a chroma block based on modes of a luma block may be provided.
Further, according to the present disclosure, a method and apparatus for improving video encoding/decoding efficiency may be provided.
Effects that can be obtained from the present disclosure are not limited to the above-mentioned effects, and other effects that are not mentioned can be clearly understood by those of ordinary skill in the art from the following description.
Drawings
Fig. 1 is a block diagram illustrating a video encoding apparatus in which the techniques of this disclosure may be implemented.
Fig. 2 is a diagram illustrating a method for partitioning blocks using a quadtree plus binary tree trigeminal tree (QTBTTT) structure.
Fig. 3a and 3b are diagrams illustrating a plurality of intra prediction modes including a wide-angle intra prediction mode.
Fig. 4 is a block diagram illustrating the neighboring blocks of the current block.
Fig. 5 is a block diagram illustrating a video decoding device that may implement the techniques of this disclosure.
Fig. 6 is a diagram illustrating a process of generating a prediction block based on a technique for deriving an intra prediction mode in a decoder (decoder-side intra mode derivation: DIMD) according to an embodiment of the present disclosure.
Fig. 7 is a diagram illustrating a DIMD-based decoding process according to an embodiment of the present disclosure.
Fig. 8 is a diagram illustrating a DIMD blend mode in which weight values are assigned to prediction values of intra prediction modes of neighboring blocks according to a DIMD index according to another embodiment of the present disclosure.
Fig. 9 is a diagram illustrating neighboring blocks adjacent to a current block according to an embodiment of the present disclosure.
Fig. 10 is a diagram illustrating a process of deriving an intra prediction mode and generating a prediction block based on a histogram of the mode according to an embodiment of the present disclosure.
Fig. 11 is a diagram illustrating a process of deriving an intra prediction mode based on a histogram of a mode without considering a plane mode and generating a prediction block according to an embodiment of the present disclosure.
Fig. 12 is a diagram illustrating a process of deriving an intra prediction mode based on a histogram of a mode in consideration of a plane mode and generating a prediction block according to an embodiment of the present disclosure.
Fig. 13 is a diagram illustrating a process for deriving an intra prediction mode and generating a prediction block when the number of modes in a histogram of modes is one or two according to an embodiment of the present disclosure.
Fig. 14 is a diagram illustrating a process for deriving an intra prediction mode and generating a prediction block when the number of modes in a histogram of modes is one or two according to another embodiment of the present disclosure.
Fig. 15 is a diagram illustrating a process of restricting DIMD flag resolution based on patterns derived in a histogram of patterns according to an embodiment of the present disclosure.
Fig. 16 is a diagram illustrating a process for limiting resolution of DIMD flags based on DIMD usage frequencies of neighboring blocks according to another embodiment of the present disclosure.
Fig. 17 is a diagram illustrating a process of restricting resolution of DIMD flags based on a pattern-based histogram and an MPM list according to an embodiment of the disclosure.
Fig. 18 is a diagram illustrating a video decoding process according to an embodiment of the present disclosure.
Fig. 19 is a diagram illustrating a video encoding process according to an embodiment of the present disclosure.
Detailed Description
Hereinafter, some embodiments of the present disclosure are described in detail with reference to the accompanying drawings. In the following description, like reference numerals denote like elements, although the elements are shown in different drawings. Furthermore, in the following description of some embodiments, a detailed description of related known components and functions when considered as obscuring the subject matter of the present disclosure has been omitted for the sake of clarity and conciseness.
Fig. 1 is a block diagram of a video encoding apparatus that may implement the techniques of this disclosure. Hereinafter, a video encoding apparatus and components of the apparatus are described with reference to the description of fig. 1.
The encoding device may include a picture divider 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.
Each component of the encoding apparatus may be implemented as hardware or software or as a combination of hardware and software. Further, the function of each component may be implemented as software, and a microprocessor may also be implemented to execute the function of the software corresponding to each component.
A video is made up of one or more sequences comprising a plurality of pictures. Each picture is divided into a plurality of regions, and encoding is performed on each region. For example, a picture is divided into one or more tiles or/and slices. Herein, one or more patches may be defined as a set of patches. Each patch or/and slice is divided into one or more Coding Tree Units (CTUs). In addition, each CTU is divided into one or more Coding Units (CUs) by a tree structure. Information applied to each CU is encoded as a syntax of the CU, and information commonly applied to CUs included in one CTU is encoded as a syntax of the CTU. Further, information commonly applied to all blocks in one slice is encoded as a syntax of a slice header, and information applied to all blocks constituting one or more pictures is encoded as a Picture Parameter Set (PPS) or a picture header. Furthermore, information commonly referred to by a plurality of pictures is encoded to a Sequence Parameter Set (SPS). In addition, information commonly referenced by one or more SPS's is encoded to a Video Parameter Set (VPS). In addition, information commonly applied to a patch or patch group may also be encoded as a syntax of a patch or patch group header. The syntax included in the SPS, PPS, slice header, patch, or patch group header may be referred to as a high level syntax.
The picture divider 110 determines the size of a Coding Tree Unit (CTU). Information about the size of CTUs (CTU size) is encoded as a syntax of SPS or PPS and delivered to a video decoding device.
The picture divider 110 divides each picture constituting a video into a plurality of Coding Tree Units (CTUs) having a predetermined size, and then recursively divides the CTUs by using a tree structure. Leaf nodes in the tree structure become Coding Units (CUs), which are the base units of the encoding.
The tree structure may be a Quadtree (QT) in which a higher node (or parent node) is divided into four lower nodes (or child nodes) having the same size. The tree structure may also be a Binary Tree (BT) in which a higher node is divided into two lower nodes. The tree structure may also be a Trigeminal Tree (TT), wherein the higher nodes are represented by 1:2: the ratio of 1 is divided into three lower nodes. The tree structure may also be a structure in which two or more of a QT structure, a BT structure, and a TT structure are mixed. For example, a quadtree plus binary tree (QTBT) structure may be used or a quadtree plus binary tree trigeminal tree (QTBTTT) structure may be used. Here, BTTT is added to the tree structure to be referred to as a multi-type tree (MTT).
Fig. 2 is a diagram for describing a method of dividing blocks by using the QTBTTT structure.
As shown in fig. 2, CTUs may be first divided into QT structures. Quadtree partitioning may be recursive until the size of the partitioned block reaches the minimum block size (MinQTSize) of leaf nodes allowed in QT. A first flag (qt_split_flag) indicating whether each node of the QT structure is divided into four nodes of a lower layer is encoded by the entropy encoder 155 and transmitted to the video decoding device. When the leaf node of QT is not greater than the maximum block size (MaxBTSize) of the root node allowed in BT, the leaf node may be further divided into at least one of BT structure or TT structure. There may be a plurality of division directions in the BT structure and/or the TT structure. For example, there may be two directions, i.e., a direction in which the block of the corresponding node is divided horizontally and a direction in which the block of the corresponding node is divided vertically. As shown in fig. 2, when the MTT division starts, a second flag (MTT _split_flag) indicating whether a node is divided and a flag additionally indicating a division direction (vertical or horizontal) and/or a flag indicating a division type (binary or ternary) if a node is divided are encoded by the entropy encoder 155 and signaled to the video decoding apparatus.
Alternatively, a CU partition flag (split_cu_flag) indicating whether or not a node is partitioned may also be encoded before encoding a first flag (qt_split_flag) indicating whether or not each node is partitioned into four nodes of a lower layer. When the value of the CU partition flag (split_cu_flag) indicates that each node is not partitioned, the block of the corresponding node becomes a leaf node in the partition tree structure and becomes a CU as a base unit of encoding. When the value of the CU partition flag (split_cu_flag) indicates that each node is partitioned, the video encoding apparatus first starts encoding the first flag through the above scheme.
When QTBT is used as another example of the tree structure, there may be two types, i.e., a type in which a block of a corresponding node is horizontally divided into two blocks having the same size (i.e., symmetrical horizontal division) and a type in which a block of a corresponding node is vertically divided into two blocks having the same size (i.e., symmetrical vertical division). A partition flag (split_flag) indicating whether each node of the BT structure is partitioned into lower-layer blocks and partition type information indicating a partition type are encoded by the entropy encoder 155 and delivered to the video decoding apparatus. Meanwhile, a type in which a block of a corresponding node is divided into two blocks in an asymmetric form with each other may be additionally presented. The asymmetric form may include where the blocks of the corresponding nodes are partitioned to have 1:3, or may also include a form in which blocks of corresponding nodes are divided in a diagonal direction.
A CU may have different sizes according to QTBT or QTBTTT partitioning from CTUs. Hereinafter, a block corresponding to a CU to be encoded or decoded (i.e., a leaf node of QTBTTT) is referred to as a "current block". Since QTBTTT division is adopted, the shape of the current block may be a rectangular shape in addition to a square shape.
The predictor 120 predicts a current block to generate a predicted block. Predictor 120 includes an intra predictor 122 and an inter predictor 124.
In general, each current block in a picture may be predictively coded. In general, prediction of a current block may be performed by using an intra prediction technique (using data from a picture including the current block) or an inter prediction technique (using data from a picture coded before the picture including the current block). Inter prediction includes both unidirectional prediction and bi-directional prediction.
The intra predictor 122 predicts pixels in the current block by using pixels (reference pixels) located on neighbors of the current block in the current picture including the current block. Depending on the prediction direction, there are multiple intra prediction modes. For example, as shown in fig. 3a, the plurality of intra prediction modes may include 2 non-directional modes including a planar mode and a DC mode, and may include 65 directional modes. The neighboring pixels and the algorithm equations to be used are defined differently according to each prediction mode.
For efficient directional prediction of a current block having a rectangular shape, directional modes (# 67 to # 80), intra prediction modes # -1 to # -14) as indicated by dashed arrows in fig. 3b may be additionally used. The orientation mode may be referred to as a "wide-angle intra prediction mode". In fig. 3b, the arrows indicate the corresponding reference samples for prediction and do not represent the prediction direction. The predicted 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 direction mode without additional bit transmission. In this case, in the wide-angle intra prediction mode, some wide-angle intra prediction modes available for the current block may be determined by a ratio of the width and the height of the current block having a rectangular shape. For example, when the current block has a rectangular shape with a height smaller than a width, wide-angle intra prediction modes (intra prediction modes #67 to # 80) having angles smaller than 45 degrees are available. When the current block has a rectangular shape having a width greater than a height, a wide-angle intra prediction mode having an angle greater than-135 degrees may be used.
The intra predictor 122 may determine intra prediction to be used for encoding the current block. In some examples, intra predictor 122 may encode the current block by using a plurality of intra prediction modes, and also select an appropriate intra prediction mode to be used from among the test modes. For example, the intra predictor 122 may calculate a rate-distortion value by using a rate-distortion analysis for a plurality of tested intra prediction modes, and also select an intra prediction mode having the best rate-distortion characteristic among the tested modes.
The intra predictor 122 selects one intra prediction mode among a plurality of intra prediction modes, and predicts the current block by using neighboring pixels (reference pixels) and an algorithm equation determined according to the selected intra prediction mode. Information about the selected intra prediction mode is encoded by the entropy encoder 155 and delivered to the video decoding device.
The inter predictor 124 generates a prediction block for the current block by using a motion compensation process. The inter predictor 124 searches for a block most similar to the current block in a reference picture 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 a displacement between a current block in the current picture and a predicted block in the reference picture. In general, motion estimation is performed on a luminance component, and a motion vector calculated based on the luminance component is used for both the luminance component and the chrominance component. Motion information including information on a reference picture and information on a motion vector for predicting a current block is encoded by the entropy encoder 155 and delivered to a video decoding device.
The inter predictor 124 may also perform interpolation on reference pictures or reference blocks in order to increase the accuracy of prediction. In other words, sub-samples between two consecutive integer samples are interpolated by applying the filter coefficients to a plurality of consecutive integer samples comprising the two integer samples. When the process of searching for a block most similar to the current block is performed with respect to the interpolated reference picture, it may represent not an integer-sampling-unit precision but a decimal-unit precision with respect to the motion vector. 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, tiles, CTUs, CUs, etc.). When this Adaptive Motion Vector Resolution (AMVR) is applied, information on the motion vector resolution to be applied to each target area should be signaled for each target area. For example, when the target area is a CU, information about the resolution of a motion vector applied to each CU is signaled. The information on the resolution of the motion vector may be information representing the accuracy of a motion vector difference to be described below.
Meanwhile, the inter predictor 124 may perform inter prediction by using bi-directional prediction. In the case of bi-prediction, two reference pictures and two motion vectors representing the block positions most similar to the current block in each reference picture are used. The inter predictor 124 selects a first reference picture and a second reference picture from the reference picture list0 (RefPicList 0) and the reference picture list1 (RefPicList 1), respectively. The inter 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 on two reference pictures for predicting the current block and information on two motion vectors is delivered to the entropy encoder 155. Here, the reference picture list0 may be composed of pictures preceding the current picture in display order among the previously reconstructed pictures, and the reference picture list1 may be composed of pictures following the current picture in display order among the previously reconstructed pictures. However, although not particularly limited thereto, a pre-reconstructed picture following the current picture in display order may be additionally included in the reference picture list 0. Conversely, a pre-reconstructed picture preceding the current picture may be additionally included in the reference picture list 1.
In order to minimize the number of bits consumed for encoding motion information, various methods may be used.
For example, when a reference picture and a motion vector of a current block are identical to those of a neighboring block, information capable of identifying the neighboring block is encoded to deliver motion information of the current block to a video decoding apparatus. This approach is called merge mode.
In the merge mode, the inter predictor 124 selects a predetermined number of merge candidate blocks (hereinafter, referred to as "merge candidates") from neighboring blocks of the current block.
As the neighboring blocks for deriving the merge candidates, as shown in fig. 4, all or some of a left block A0, a lower left block A1, an upper block B0, an upper right block B1, and an upper left block B2 adjacent to the current block in the current picture may be used. Further, blocks other than the current picture at 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 merging candidates. For example, a co-located block having a current block within a reference picture or a block adjacent to a co-located block may additionally be used as a merge candidate. If the number of merging candidates selected by the method described above is smaller than the preset number, a zero vector is added to the merging candidates.
The inter 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 among the merge candidates included in the merge list, and merge index information for identifying the selected candidate is generated. The generated merging index information is encoded by the entropy encoder 155 and delivered to a video decoding device.
The merge skip mode is a special case of the merge mode. After quantization, when all transform coefficients used 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, relatively high encoding efficiency can be achieved for pictures with slight motion, still pictures, screen content pictures, and the like.
Hereinafter, the merge mode and the merge skip mode are collectively referred to as a merge/skip mode.
Another method for encoding motion information is Advanced Motion Vector Prediction (AMVP) mode.
In AMVP mode, the inter predictor 124 derives a motion vector prediction (motion vector predictor) candidate for a motion vector of a current block by using neighboring blocks of the current block. As the neighboring blocks used to derive the motion vector prediction candidates, 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 shown in fig. 4 may be used. Furthermore, blocks other than the current picture located at the current block, which are located within the reference picture (which may be the same as or different from the reference picture used to predict the current block), may also be used as neighboring blocks used to derive motion vector prediction candidates. For example, a co-located block with the current block or a block adjacent to the co-located block within the reference picture may be used. If the number of motion vector candidates selected by the above method is less than a preset number, a zero vector is added to the motion vector candidates.
The inter predictor 124 derives a motion vector prediction candidate by using the motion vectors of the neighboring blocks and determines 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 a motion vector prediction from a motion vector of the current block.
Motion vector prediction may be obtained by applying a predefined function (e.g., center value and average value calculation, etc.) to the motion vector prediction candidates. In this case, the video decoding device also knows the predefined function. Furthermore, since the neighboring block used to derive the motion vector prediction candidate is a block for which encoding and decoding have been completed, the video decoding apparatus may also already know the motion vector of the neighboring block. Therefore, the video encoding device does not need to encode information for identifying motion vector prediction candidates. Thus, in this case, information on the motion vector difference and information on the reference picture for predicting the current block are encoded.
Meanwhile, motion vector prediction may also be determined by selecting a scheme of any one of the motion vector prediction candidates. In this case, information for identifying the selected motion vector prediction candidate is encoded in association with information on a motion vector difference and information on a reference picture for predicting the current block.
The subtractor 130 generates a residual block by subtracting the prediction block generated by the intra predictor 122 or the inter predictor 124 from the current block.
The transformer 140 transforms a residual signal in a residual block having pixel values of a spatial domain into transform coefficients of a frequency domain. The transformer 140 may transform the residual signal in the residual block by using the overall size of the residual block as a transform unit, or may also divide the residual block into a plurality of sub-blocks and may perform the transform by using the sub-blocks as transform units. Alternatively, the residual block is divided into two sub-blocks, a transform region and a non-transform region, respectively, to transform the residual signal using only the transform region sub-block as a transform unit. Here, the transform region sub-block may be 1 with a horizontal axis (or vertical axis) based: 1, one of two rectangular blocks of size ratio. In this case, a flag (cu_sbt_flag) indicates only a transform sub-block, and direction (vertical/horizontal) information (cu_sbt_horizontal_flag) and/or position information (cu_sbt_pos_flag) are encoded by the entropy encoder 155 and signaled to the video decoding device. Furthermore, the transform region sub-block may have a size of 1 based on the horizontal axis (or vertical axis): 3. In this case, the flag (cu_sbt_quad_flag) divided into the corresponding partitions is additionally encoded by the entropy encoder 155 and signaled to the video decoding device.
Meanwhile, the transformer 140 may perform transformation 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, transform function pairs for horizontal transforms and vertical transforms may be defined as Multiple Transform Sets (MTS). The transformer 140 may select one transform function pair having the highest transform efficiency in the MTS and may transform the residual block in each of the horizontal and vertical directions. The information (mts_idx) of the transform function pair in the MTS is encoded by the entropy encoder 155 and signaled to the video decoding device.
The quantizer 145 quantizes the transform coefficient output from the transformer 140 using quantization parameters and outputs the quantized transform coefficient to the entropy encoder 155. The quantizer 145 may also immediately quantize the relevant residual block without a transform for any block or frame. The quantizer 145 may also apply different quantization coefficients (scaling values) according to the positions of the transform coefficients in the transform block. A quantization matrix applied to quantized transform coefficients arranged in 2 dimensions may be encoded and signaled to a video decoding device.
The rearrangement unit 150 may perform realignment of coefficient values for quantized residual values.
The rearrangement unit 150 may change the 2D coefficient array to a 1D coefficient sequence by using coefficient scanning. For example, the rearrangement unit 150 may output a 1D coefficient sequence by scanning the DC coefficient into a high frequency domain coefficient using a zig-zag scan or a diagonal scan. Instead of zig-zag scanning, vertical scanning that scans the 2D coefficient array in the column direction and horizontal scanning that scans the 2D block type coefficients in the row direction may also be used, depending on the size of the transform unit and the intra prediction mode. In other words, according to the size of the transform unit and the intra prediction mode, a scan method to be used may be determined in zig-zag scan, diagonal scan, vertical scan, and horizontal scan.
The entropy encoder 155 generates a bitstream by encoding a sequence of 1D quantized transform coefficients output from the rearrangement unit 150 using various encoding schemes including a context-based adaptive binary arithmetic code (CABAC), exponential golomb, and the like.
Further, the entropy encoder 155 encodes information related to block division, such as CTU size, CTU division flag, QT division flag, MTT division type, MTT division direction, etc., to allow the video decoding apparatus to equally divide blocks to the video encoding apparatus. Further, the entropy encoder 155 encodes information on a prediction type indicating whether the current block is encoded by intra prediction or inter prediction. The entropy encoder 155 encodes intra prediction information (i.e., information about an intra prediction mode) or inter prediction information (a merging index in the case of a merging mode, and information about a reference picture index and a motion vector difference in the case of an AMVP mode) according to a prediction type. Further, the entropy encoder 155 encodes information related to quantization (i.e., information about quantization parameters and information about quantization matrices).
The inverse quantizer 160 dequantizes the quantized transform coefficients output from the quantizer 145 to generate transform coefficients. The inverse transformer 165 transforms the transform coefficients output from the inverse quantizer 160 from the frequency domain to the spatial domain to reconstruct the residual block.
The adder 170 adds the reconstructed residual block and the prediction block generated by the predictor 120 to reconstruct the current block. Pixels in the reconstructed current block may be used as reference pixels when intra-predicting the next sequential block.
The loop filter unit 180 performs filtering on the reconstructed pixels in order to reduce block artifacts, ringing artifacts, blurring artifacts, etc., which 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.
The deblocking filter 182 filters boundaries between reconstructed blocks to remove blocking artifacts occurring due to block unit encoding/decoding, and the SAO filter 184 and ALF 186 perform additional filtering on the deblocking filtered video. SAO filter 184 and ALF 186 are filters used to compensate for differences between reconstructed pixels and original pixels that occur due to lossy coding. The SAO filter 184 applies an offset as a CTU unit to enhance subjective picture quality and coding efficiency. On the other hand, the ALF 186 performs block unit filtering, and compensates for distortion by applying different filters by dividing boundaries of corresponding blocks and the degree of variation. Information about filter coefficients to be used for ALF may be encoded and signaled to a video decoding device.
Reconstructed blocks filtered by the deblocking filter 182, the SAO filter 184, and the ALF 186 are stored in a memory 190. When all blocks in one picture are reconstructed, the reconstructed picture may be used as a reference picture for inter prediction of blocks within a picture to be encoded later.
Fig. 5 is a functional block diagram of a video decoding device that may implement the techniques of this disclosure. Hereinafter, referring to fig. 5, a video decoding apparatus and components of the apparatus are described.
The video decoding device 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.
Similar to the video encoding device of fig. 1, each component of the video decoding device may be implemented as hardware or software or as a combination of hardware and software. Further, the function of each component may be implemented as software, and a microprocessor may also be implemented to execute the function of the software corresponding to each component.
The entropy decoder 510 extracts information related to block division by decoding a bitstream generated by a video encoding device to determine a current block to be decoded, and extracts prediction information and information about a residual signal required to restore the current block.
The entropy decoder 510 determines the size of CTUs by extracting information on the size of CTUs from a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS), and divides pictures into CTUs having the determined size. In addition, the CTU is determined to be the highest layer of the tree structure, i.e., the root node, and division information of the CTU may be extracted to divide the CTU using the tree structure.
For example, when dividing CTUs using the QTBTTT structure, first a first flag (qt_split_flag) related to the division of QT is extracted to divide each node into four nodes of the lower layer. Further, with respect to a node corresponding to a leaf node of QT, a second flag (MTT _split_flag) related to division of MTT, a division direction (vertical/horizontal), and/or a division type (binary/ternary) are extracted to divide the corresponding leaf node into MTT structures. Thus, each node below the leaf node of QT is recursively divided into BT or TT structures.
As another example, when CTUs are divided by using the QTBTTT structure, a CU division flag (split_cu_flag) indicating whether a CU is divided is extracted. When the corresponding block is divided, a first flag (qt_split_flag) may also be extracted. During the partitioning process, 0 or more recursive MTT partitions may occur after 0 or more recursive QT partitions with respect to each node. For example, MTT partitioning may occur immediately, or conversely, QT partitioning may occur only multiple times, relative to CTUs.
As another example, when dividing CTUs using a QTBT structure, a first flag (qt_split_flag) related to the division of QT is extracted to divide each node into four nodes of a lower layer. Further, a division flag (split_flag) indicating whether a node corresponding to a leaf node of QT is further divided into BT and division direction information are extracted.
Meanwhile, when the entropy decoder 510 determines a current block to be decoded by using the division of the tree structure, the entropy decoder 510 extracts information on 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 for intra prediction information (intra prediction mode) of the current block. When the prediction type information indicates inter prediction, the entropy decoder 510 extracts information representing syntax elements (i.e., motion vectors and reference pictures to which the motion vectors refer) for the inter prediction information.
Further, the entropy decoder 510 extracts quantization related information and extracts information on quantized transform coefficients of the current block as information on a residual signal.
The rearrangement unit 515 may change the sequence of the 1D quantized transform coefficients entropy decoded by the entropy decoder 510 into a 2D coefficient array (i.e., block) again in the reverse order of the coefficient scan order performed by the video encoding device.
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 quantized coefficients (scaling values) to the quantized transform coefficients arranged in 2D. The inverse quantizer 520 may perform dequantization by applying a matrix (scaled value) of quantized coefficients from a video encoding device to a 2D array of quantized transform coefficients.
The inverse transformer 530 generates a residual block for the current block by restoring a residual signal through inverse transforming the dequantized transform coefficients from the frequency domain to the spatial domain.
Further, 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) where 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 transform coefficients of the corresponding sub-block from the frequency domain to the spatial domain to reconstruct a residual signal and fills the region that is not inversely transformed with "0" values as the residual signal to generate a final residual block for the current block.
Further, when applying MTS, the inverse transformer 530 determines a transformation index or transformation matrix applied in each of the horizontal direction and the vertical direction by using MTS information (mts_idx) signaled from the video encoding apparatus. The inverse transformer 530 also performs inverse transformation on the transform coefficients in the transform block in the horizontal direction and the vertical direction by using the determined transform function.
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.
The intra predictor 542 determines an intra prediction mode of the 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 an intra prediction mode.
The inter predictor 544 determines a motion vector of the current block and a reference picture to which the motion vector refers by using syntax elements for the inter prediction mode extracted from the entropy decoder 510.
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. In intra prediction of a block to be decoded later, pixels within the reconstructed current block are used as reference pixels.
The loop filter unit 560, which is 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 boundaries between reconstructed blocks in order to remove blocking artifacts occurring due to block unit decoding. The SAO filter 564 and ALF 566 perform additional filtering on the reconstructed block after deblocking filtering to compensate for differences between the reconstructed pixels and the original pixels that occur due to lossy encoding. The filter coefficients of the ALF are determined by using information on the filter coefficients decoded from the bitstream.
The reconstructed block filtered by the deblocking filter 562, the SAO filter 564, and the ALF 566 is stored in a memory 570. When all blocks in one picture are reconstructed, the reconstructed picture may be used as a reference picture for inter prediction of blocks within a picture to be encoded later.
Fig. 6 is a diagram illustrating a process of generating a prediction block based on a technique for deriving an intra prediction mode in a decoder (decoder-side intra mode derivation: DIMD) according to an embodiment of the present disclosure. Intra-picture prediction may have the same meaning as intra-prediction. The DIMD may correspond to a method of deriving an intra prediction mode of a current block in a decoding process in a decoder without transmitting intra prediction mode information of the current block from an encoder to the decoder. In DIMD, a Sobel filter may be applied to neighboring pixels of the current block to calculate gradients of the pixels. A gradient histogram (HoG) may be generated based on the calculated gradients. From the histogram of gradients, the two gradients with the maximum value may be selected, and an intra prediction mode for pixels with the two gradients may be derived. Weight values are assigned to the derived predictors of the two intra prediction modes and the planar mode, and the predicted block of the current block may be generated by adding these predictors. Here, a fixed weight value of 1/3 may be assigned to the predicted value of the planar mode. The weight value, to which 2/3 is proportionally allocated based on the value of the gradient, is allocated to the predicted values of the two derived intra prediction modes. The sum of the weight value assigned to the predicted value of the plane mode and the weight values assigned to the predicted values of the two derived intra prediction modes may correspond to 1.
Referring to fig. 6, prediction values of intra prediction modes and plane modes of two neighboring blocks adjacent to the current block may correspond to Pred, respectively 1 、Pred 2 And Pred 3 . Weight value W 1 Can be assigned to Pred 1 Weight value W 2 Can be assigned to Pred 2 And weight value W 3 Can be assigned to Pred 1 . The weight values are assigned to the corresponding prediction values, which may be added to generate a prediction block of the current block. However, the present disclosure is not limited to the above embodiments.
Fig. 7 is a diagram illustrating a DIMD-based decoding process according to an embodiment of the present disclosure.
Referring to fig. 7, the decoding apparatus may obtain information (e.g., a DIMD flag) indicating whether to derive an intra prediction mode of a current block based on a DIMD (S710). The DIMD flag having a first value (e.g., 0) may indicate that the intra prediction mode of the current block is not derived based on DIMD. The DIMD flag having a second value (e.g., 1) may indicate that the intra prediction mode of the current block is derived based on DIMD. It may be determined whether the obtained DIMD flag has a first value (e.g., 0) (S720). When the DIMD flag has a first value (e.g., 0) (S720-yes), the decoding apparatus may obtain intra prediction mode information of the current block (S730). The decoding apparatus may reconstruct the current block based on the obtained intra prediction mode information (S740). When the DIMD flag has a second value (e.g., 1) (S720-no), the decoding apparatus may derive an intra prediction mode of the current block based on the DIMD (S750). The decoding apparatus may reconstruct the current block based on the derived intra prediction mode of the current block (S760).
Fig. 8 is a diagram illustrating a DIMD blend mode in which weight values are assigned to prediction values of intra prediction modes of neighboring blocks according to a DIMD index according to another embodiment of the present disclosure. In DIMD, a Sobel filter may be applied to neighboring pixels of the current block to calculate gradients of the pixels, and a histogram of the gradients may be generated based on the calculated gradients. The two gradients having the maximum value may be selected from the histogram of gradients, and an intra prediction mode of a pixel having the two gradients may be derived. There may be a DIMD blend mode in which the predictors of the two derived intra prediction modes are blended with the predictors of the planar mode. Assigning a weight value to an intra prediction mode may refer to assigning a weight value to a prediction value based on the intra prediction mode.
Referring to fig. 8, the derived two intra prediction modes may correspond to a first mode and a second mode, respectively. The first mixed mode may correspond to a mode in which the first mode and the second mode are mixed. Here, the weight value of each mode may be determined based on the value of the gradient selected from the histogram. The second mixed mode may correspond to a mode in which the second mode and the planar mode are mixed. Here, a fixed weight value of 1/3 may be assigned to the planar mode, and a fixed weight value of 2/3 may be assigned to the second mode. The third mixed mode may correspond to a mode in which the first mode, the second mode, and the planar mode are mixed. Here, a fixed weight value of 5/9 may be assigned to the planar mode, and a fixed weight value of 4/9 may be proportionally assigned to the first mode and the second mode based on the value of the gradient selected in the histogram. Of these three modes, the best hybrid mode may be determined based on a rate-distortion decision (RD decision). Information about the determined blend mode may be parsed from the encoder to the decoder as a DIMD indicator. Here, the intra prediction mode information may not be parsed to the decoder. When the DIMD indicator is a first value (e.g., 0), the intra prediction mode of the current block may not be derived based on DIMD. When the DIMD indicator is a second value (e.g., 1), the intra prediction mode of the current block may be derived based on the first hybrid mode. When the DIMD indicator is a third value (e.g., 2), the intra prediction mode of the current block may be derived based on the second hybrid mode. When the DIMD indicator is a fourth value (e.g., 3), the intra prediction mode of the current block may be derived based on the third hybrid mode.
Fig. 9 is a diagram illustrating neighboring blocks adjacent to a current block according to an embodiment of the present disclosure. In addition to a method of deriving an intra prediction mode based on a histogram of gradients of neighboring pixels adjacent to the current block, there may be a method of deriving an intra prediction mode based on a histogram of modes of neighboring blocks of the current block. Methods of deriving intra prediction modes based on histograms of modes may have low complexity because the histograms are generated by computing gradients on a block-by-block basis using intra prediction modes of neighboring blocks instead of using Sobel filters for neighboring pixels.
Referring to fig. 9, neighboring blocks adjacent to the current block may correspond to blocks a to Q. The sizes of the blocks a through Q may correspond to blocks in a minimum unit storing intra prediction mode information. A histogram of the mode may be generated based on intra prediction modes of neighboring blocks adjacent to the current block. As an example, a histogram of modes may be generated based on intra prediction modes of blocks a to D, I to L, and Q, which are neighboring blocks of the current block. As an example, a histogram of modes may be generated based on intra prediction modes of blocks a through Q. However, the present disclosure is not limited to these embodiments. The number and location of neighboring blocks used to generate the histogram of the pattern may be arbitrarily determined.
Fig. 10 is a diagram illustrating a process of deriving an intra prediction mode and generating a prediction block based on a histogram of the mode according to an embodiment of the present disclosure. A histogram of the mode may be generated based on intra prediction modes of neighboring blocks adjacent to the current block. The three modes having the highest occurrence frequencies may be selected from the histogram of modes, and weight values may be assigned to prediction blocks for the three modes and the above prediction blocks are added so that a final prediction block may be generated.
Referring to fig. 10, a histogram of modes may be generated based on intra prediction modes of neighboring blocks of a current block. M is M 1 、M 2 And M 3 The pattern may be selected as the pattern having the highest frequency of occurrence in the histogram of the pattern. Can be produced as M 1 、M 2 And M 3 Pred_M of prediction block of mode 1 、Pred_M 2 And pred_M 3 . Weight value W 1 、W 2 And W is 3 Assigned to pred_M 1 、Pred_M 2 And pred_M 3 And added so that a final prediction block F _ Pred can be generated.
Fig. 11 is a diagram illustrating a process of deriving an intra prediction mode based on a histogram of a mode without considering a plane mode and generating a prediction block according to an embodiment of the present disclosure. The planar mode may be excluded from the three modes selected in the histogram of the modes. In this case, the planar mode may not be considered.
Referring to fig. 11, a histogram of the pattern may be generated (S1110). The three patterns having the highest occurrence frequency may be selected from the histogram of occurrence patterns (S1120). It may be determined whether the plane mode is included in the three selected modes (S1130). When a planar mode is included in the three selected modes (S1130-yes), the planar mode may be used to generate a prediction block of the current block (S1140). Here, weight values are assigned to a prediction block for a plane mode and a prediction block for two other selected modes and the above prediction blocks are added so that a prediction block of a current block can be generated. When the planar mode is not included among the three selected modes (S1130-no), the prediction block of the current block may be generated using the three selected modes instead of using the planar mode (S1150). Here, weight values are assigned to the prediction blocks for the three selected modes and the above prediction blocks are added so that the prediction block of the current block can be generated. The weight value may be determined by a proportional distribution according to the occurrence frequency of the pattern with respect to the total occurrence frequency of three patterns selected in the histogram of the patterns. The sum of the weight values of the three modes may correspond to 1.
Fig. 12 is a diagram illustrating a process of deriving an intra prediction mode and generating a prediction block considering a plane mode based on a mode histogram according to an embodiment of the present disclosure. Since the plane mode has a high frequency of occurrence in intra prediction, selecting the plane mode as the default mode may improve coding efficiency.
Referring to fig. 12, a histogram of patterns may be generated (S1210). The three patterns having the highest occurrence frequency may be selected from the histogram of occurrence patterns (S1220). It may be determined whether the plane mode is included in the three selected modes (S1230). When a plane mode is included in the three selected modes (S1230-yes), the plane mode may be used to generate a prediction block of the current block (S1240). Here, weight values are assigned to a prediction block for a plane mode and a prediction block for two other selected modes and the above prediction blocks are added so that a prediction block of a current block can be generated. The weight value may be determined as any fixed value. When the plane mode is not included among the three selected modes (S1230-no), two modes having the highest occurrence frequency among the three selected modes may be selected (S1250). The two selected modes and the plane mode may be used to generate a prediction block of the current block (S1260). Here, weight values are assigned to a prediction block for a plane mode and a prediction block for two other selected modes and the above prediction blocks are added so that a prediction block of a current block can be generated. The weight value assigned to the prediction block of the plane mode may be determined as a fixed value. The weight values assigned to the prediction blocks of the two other selected modes may be determined from values obtained by subtracting the weight values assigned to the prediction blocks of the planar mode from 1 according to the ratio distribution of the occurrence frequencies of the two selected modes.
Fig. 13 is a diagram illustrating a process for deriving an intra prediction mode and generating a prediction block when the number of modes in a histogram of modes is one or two according to an embodiment of the present disclosure. Three modes are selected from the histogram of modes so that a prediction block of the current block can be generated. However, the present disclosure is not limited to these embodiments. Any number of modes is selected from the histogram of modes such that a prediction block for the current block may be generated.
Referring to fig. 13, a histogram of the pattern can be generated (S1310). It may be determined whether the number of patterns occurring in the histogram of the patterns is one or two (S1320). When the number of patterns appearing in the histogram of patterns is one or two (S1320-yes), the same number of patterns as the number of insufficient patterns may be retrieved from the default pattern set and used to generate the prediction block of the current block (S1330). Here, the default mode setting may be set in advance. The default mode set may be composed of modes having a high occurrence frequency among the intra prediction modes. The patterns taken from the default pattern set may not overlap with one or both of the patterns that appear in the histogram of the patterns. Weight values may be assigned to one or both of the prediction blocks of modes that occur in the histogram of modes and the prediction blocks of modes that are taken from the default mode set. The weight value may be added so that a prediction block of the current block may be generated. Any fixed weight value may be assigned to the prediction block of modes taken from the default mode set. For a prediction block of one or two modes appearing in the histogram of the mode, weight values that are distributed in proportion to the frequency of occurrence of one or two modes in the histogram of the mode from among values obtained by subtracting a fixed weight value from 1 may be assigned. The default mode set may be preset as a plane mode, a DC mode, a vertical mode, a horizontal mode, etc. having a high occurrence probability. By accumulating the frequency of occurrence of intra prediction modes in units such as a sequence level, a picture level, and a slice level, a default mode set can be managed in descending order of the frequency of occurrence. Since a default mode set reflecting the picture characteristics is created for each sequence, picture, or slice, the accuracy of intra prediction can be improved.
When the number of patterns appearing in the histogram of the patterns is not one or two (S1320-no), the three patterns having the highest frequency of occurrence may be selected from the histogram of the patterns and may be used to generate a prediction block of the current block (S1340). Here, weight values are assigned to the prediction blocks for the three selected modes and the above prediction blocks are added so that the prediction block of the current block can be generated. The weight value may be determined by a proportional distribution according to the occurrence frequency of the pattern with respect to the total occurrence frequency of three patterns selected in the histogram of the patterns. The sum of the weight values assigned to the prediction blocks for the three modes may correspond to 1.
Fig. 14 is a diagram illustrating a process for deriving an intra prediction mode and generating a prediction block when the number of modes occurring in a histogram of modes is one or two according to another embodiment of the present disclosure.
Referring to fig. 14, a histogram of patterns may be generated (S1410). It may be determined whether the number of patterns occurring in the histogram of the patterns is one or two (S1420). When the number of patterns appearing in the histogram of the patterns is one or two (S1420-yes), only the patterns appearing may be used to generate a prediction block of the current block (S1430). The weight values are assigned to the prediction blocks for the appearance mode and added so that the prediction block of the current block can be generated. When there is only one appearance mode, the weight value may be 1. When two appearance modes exist, the weight values may be distributed in proportion to the frequencies of appearance of the two modes. When the number of patterns appearing in the histogram of the patterns is not one or two (S1420-no), three patterns having the highest frequency of occurrence may be selected from the histogram of the patterns and used to generate the prediction block of the current block (S1440). Here, weight values are assigned to the prediction blocks for the three selected modes and the above prediction blocks are added so that the prediction block of the current block can be generated. The weight value may be determined by a proportional distribution according to the occurrence frequency of the pattern with respect to the total occurrence frequency of three patterns selected in the histogram of the patterns. The sum of the weight values of the three modes may correspond to 1.
When generating a histogram of a mode to derive an intra prediction mode according to the present disclosure, and when neighboring blocks of a current block are in an inter prediction mode or matrix-based intra prediction Mode (MIP) instead of an intra prediction mode or do not contain information about a specific mode, the histogram of the mode may be generated, excluding information of the corresponding block. When all neighboring blocks are excluded, a default set of modes may be used to generate a histogram of modes. Alternatively, mapping to any preset pattern (such as a planar pattern or a DC pattern) is performed so that a histogram of the pattern can be generated.
Fig. 15 is a diagram illustrating a process of restricting DIMD flag resolution based on patterns derived in a histogram of patterns according to an embodiment of the present disclosure. The DIMD flag may correspond to information indicating whether an intra prediction mode is derived in the decoder. In the method of deriving the intra prediction mode of the current block based on the histogram of the gradient of the neighboring pixels, it is difficult to use a condition for parsing the DIMD flag in a specific case. In the parsing order of the encoding apparatus, all grammars related to one decoding tree unit are parsed in units of decoding tree units (CTUs), and residual signals of several decoding units (CUs) constituting the decoding tree unit may be sequentially parsed. Since syntax information of all coding units within a coding tree unit is first parsed and then a residual signal is parsed, reference pixel information of neighboring blocks cannot be used in the step of parsing the syntax of a specific coding unit. Therefore, in the step of parsing the DIMD flag of the decoding unit, since the residual signal is not parsed, the neighboring reference pixels cannot be used, and the gradient of the neighboring reference pixels cannot be calculated, so that the histogram of the gradient cannot be generated. In other words, in the method of deriving the intra prediction mode of the current block based on the histogram of the gradient of the neighboring pixels, the DIMD flag is always parsed.
According to the present disclosure, in the method of deriving the intra prediction mode of the current block based on the mode histogram, since syntax information of a decoding unit constituting a decoding tree unit is first parsed, mode information of a neighboring block for which parsing has been completed in the step of parsing the DIMD flag may be used. Thus, the mode information of the current block can be derived based on the mode information of the neighboring block that has been parsed, and various parsing conditions can be set. In a method of deriving an intra prediction mode of a current block based on a histogram of gradients of neighboring pixels, a DIMD flag is located at the top of a decoding process. Thus, the DIMD flag bit may be wasted when the intra prediction mode is not derived based on the DIMD. According to the present disclosure, a method of deriving an intra prediction mode of a current block based on a mode histogram can save a DIMD flag bit because a DIMD flag is parsed only when a specific condition is satisfied, instead of always parsing the DIMD flag.
Referring to fig. 15, a histogram of the pattern may be generated (S1510). It may be determined whether all modes occurring in the histogram of the modes are non-directional modes or whether all neighboring blocks are inter prediction modes (S1520). When all modes in the histogram of modes are non-directional modes or all neighboring blocks are inter prediction modes (S1520-yes), the DIMD flag may not be parsed (S1530). In this case, the intra prediction mode derivation method based on DIMD may not be used. When there is a directional mode among modes appearing in the histogram of the modes or an intra prediction mode of the directional mode among neighboring blocks (S1520-no), the DIMD flag may be parsed (S1540). In this case, a DIMD-based intra prediction mode derivation method may be used.
Fig. 16 is a diagram illustrating a process for limiting resolution of DIMD flags based on DIMD usage frequencies of neighboring blocks according to another embodiment of the present disclosure. When neighboring blocks of the current block use the intra prediction mode derivation method, the current block is also likely to use the intra prediction mode derivation method. This is because there may be areas of particularly well-derived modes in neighboring blocks of the current block.
Referring to fig. 16, it may be determined whether the intra prediction mode is derived based on DIMD with respect to neighboring blocks at a specific location or whether the frequency of use of the DIMD-based intra prediction mode derivation of all neighboring blocks exceeds any specific threshold (S1610). The DIMD flag may be parsed (S1620) when neighboring blocks at a specific location derive intra prediction modes based on DIMD or when the frequency of use derived based on intra prediction modes of DIMD of all neighboring blocks exceeds a specific threshold (S1610-yes). In this case, a DIMD-based intra prediction mode derivation method may be used. When the intra prediction modes are not derived based on the DIMD in neighboring blocks at specific positions, and when the frequency of use of the DIMD-based intra prediction mode derivation of all neighboring blocks does not exceed a specific threshold (S1610-no), the DIMD flag may not be parsed (S1630). In this case, the intra prediction mode derivation method based on DIMD may not be used.
Fig. 17 is a diagram illustrating a process of restricting resolution of DIMD flags based on a pattern-based histogram and an MPM list according to an embodiment of the disclosure.
Referring to fig. 17, a histogram of the pattern may be generated (S1710). The pattern having the highest frequency of occurrence may be selected from the histogram of the occurrence pattern (S1720). It may be determined whether the selected mode having the highest frequency of occurrence and the first mode in the MPM list are the same (S1730). The present disclosure is not limited to this embodiment, and it may be determined whether any pattern other than the first pattern in the MPM list is the same as the pattern having the highest frequency of occurrence in the histogram of patterns. When the selected mode having the highest frequency of occurrence is the same as the first mode in the MPM list (S1730-yes), the DIMD flag may not be parsed (S1740). In this case, the intra prediction mode derivation method based on DIMD may not be used. When the mode having the highest frequency of occurrence in the MPM list is the same as the first mode, the current block has sufficient correlation with the neighboring block, and thus the predicted block of the current block may be generated by using the intra prediction mode of the neighboring block. When the selected mode having the highest occurrence frequency is different from the first mode in the MPM list (S1730-no), the DIMD flag may be parsed (S1750). In this case, a DIMD-based intra prediction mode derivation method may be used. According to the present disclosure, by selectively parsing the DIMD flag under specific conditions, instead of always parsing the DIMD flag, the DIMD flag bit can be saved and the encoding efficiency can be improved.
Hereinafter, a Direct Mode (DM) processing method in intra prediction of a chrominance component is described.
In the intra prediction of the chrominance component, when the intra prediction mode of the chrominance block is a direct mode, the mode of the corresponding luminance block may be used as it is for the mode of the chrominance block. In this case, when a corresponding luminance block is derived in the DIMD intra prediction mode, the mode of the chrominance block cannot be directly determined. In this case, the mode of the chroma block can be determined by two methods. In the first method, a pattern having the highest frequency of occurrence in the histogram of the pattern may be assigned to a pattern of a luminance block corresponding to a chrominance block. In this method, since a histogram of patterns is generated and the frequency of occurrence is calculated, complexity may be high. In the second method, a planar mode may be assigned to a mode of a luminance block corresponding to a chrominance block. Here, any mode other than the planar mode may be assigned to the mode of the luminance block corresponding to the chrominance block. At video with 4:2:2 or 4:4: in case of the 4 chroma format, the DIMD intra prediction derivation method for a luminance block is applied to a chroma block so that an intra prediction mode of the chroma block can be derived. Alternatively, the three modes having the highest occurrence frequency are selected from the histogram of the modes in which the luminance block occurs, and subjected to weighted average, so that a predicted block of the chrominance block can be generated.
Fig. 18 is a diagram illustrating a video decoding process according to an embodiment of the present disclosure.
Referring to fig. 18, an intra prediction mode list may be generated based on intra prediction modes of neighboring blocks adjacent to the current block (S1810). The intra prediction mode list may correspond to a histogram of modes. Based on the number of intra prediction modes appearing in the intra prediction mode list being three or more, at least three intra prediction modes may be selected from the intra prediction mode list (S1820). The at least three intra prediction modes selected may correspond to three intra prediction modes having the highest occurrence frequencies in the intra prediction mode list. When there is no plane mode among the selected at least three intra prediction modes, at least two intra prediction modes having the highest occurrence frequency may be selected from among the at least three intra prediction modes. At least three prediction blocks may be generated based on at least two intra prediction modes and a plane mode. A weighted average of at least three prediction blocks is performed so that a prediction block of the current block can be generated. When there is no plane mode among the selected at least three intra prediction modes, at least three prediction blocks may be generated based on the selected at least three intra prediction modes, regardless of the plane mode. A weighted average of at least three prediction blocks is performed so that a prediction block of the current block can be generated. Based on the number of intra-prediction modes occurring in the intra-prediction mode list being one or two, one or two intra-prediction modes may be selected from a default mode set. At least three prediction blocks may be generated based on the intra prediction mode that occurs and the intra prediction mode selected from the default mode set. A weighted average is performed on at least three prediction blocks, and a prediction block of the current block may be generated. The intra prediction mode selected from the default mode set may not overlap with the intra prediction modes appearing in the intra prediction mode list. Based on the number of intra prediction modes occurring in the intra prediction mode list being one or two, one or two intra prediction modes may be selected from the intra prediction mode list. One or two prediction blocks may be generated based on one or two intra prediction modes. A weighted average is performed on one or both prediction blocks so that a prediction block for the current block can be generated.
At least three prediction blocks may be generated based on at least three intra prediction modes (S1830). The prediction block of the current block may be generated by performing a weighted average on at least three prediction blocks (S1840). The weighted average of the at least three prediction blocks may correspond to assigning weight values determined based on the occurrence frequencies of the at least three intra prediction modes to the at least three prediction blocks, and adding the values. The information indicating whether the intra prediction mode is derived in the decoder may be obtained based on the presence of at least one directional mode among intra prediction modes occurring in the intra prediction mode list or the presence of intra prediction modes as at least one directional mode among neighboring blocks. The information indicating whether the intra prediction mode is derived in the decoder may correspond to a DIMD flag. The information indicating whether to derive the intra prediction mode in the decoder may be obtained based on whether the neighboring block at a specific position derives the intra prediction mode in the decoder or the neighboring block adjacent to the current block has a frequency exceeding any value at which the intra prediction mode is derived in the decoder. Based on the intra prediction mode having the highest occurrence frequency in the intra prediction mode list being different from any mode in the MPM list, information indicating whether the intra prediction mode is derived in the decoder may be obtained.
Fig. 19 is a diagram illustrating a video encoding process according to an embodiment of the present disclosure. An intra prediction mode list may be generated based on intra prediction modes of neighboring blocks adjacent to the current block (S1910). The intra prediction mode list may correspond to a histogram of modes. Based on the number of intra prediction modes appearing in the intra prediction mode list being three or more, at least three intra prediction modes may be selected from the intra prediction mode list (S1920). The at least three intra prediction modes selected may correspond to three intra prediction modes having the highest occurrence frequencies in the intra prediction mode list. When there is no plane mode among the selected at least three intra prediction modes, at least two intra prediction modes having the highest occurrence frequency may be selected from among the at least three intra prediction modes. At least three prediction blocks may be generated based on at least two intra prediction modes and a plane mode. A weighted average of at least three prediction blocks may be performed to generate a prediction block of the current block. When there is no plane mode among the selected at least three intra prediction modes, at least three prediction blocks may be generated based on the selected at least three intra prediction modes, regardless of the plane mode. A weighted average of at least three prediction blocks is performed so that a prediction block of the current block can be generated. Based on the number of intra-prediction modes occurring in the intra-prediction mode list being one or two, one or two intra-prediction modes may be selected from a default mode set. The at least three prediction blocks may be generated based on the intra-prediction mode that occurs and the intra-prediction mode selected from the default mode set. A weighted average is performed on at least three prediction blocks, and a prediction block of the current block may be generated. The intra prediction mode selected from the default mode set may not overlap with the intra prediction modes appearing in the intra prediction mode list. Based on the number of intra prediction modes occurring in the intra prediction mode list being one or two, one or two intra prediction modes may be selected from the intra prediction mode list. One or two prediction blocks may be generated based on one or two intra prediction modes. A weighted average is performed on one or both prediction blocks so that a prediction block for the current block can be generated.
At least three prediction blocks may be generated based on at least three intra prediction modes (S1930). The prediction block of the current block can be generated by performing weighted average on at least three prediction blocks (S1940). The weighted average of the at least three prediction blocks may correspond to assigning weight values determined based on the occurrence frequencies of the at least three intra prediction modes to the at least three prediction blocks and summing the weight values. The information indicating whether the intra prediction mode is derived in the decoder may be encoded based on the presence of at least one directional mode among intra prediction modes occurring in the intra prediction mode list or the presence of intra prediction modes as at least one directional mode among neighboring blocks. The information indicating whether the intra prediction mode is derived in the decoder may correspond to a DIMD flag. The information indicating whether the intra prediction mode is derived in the decoder may be encoded based on neighboring blocks at a specific location deriving the intra prediction mode in the decoder or neighboring blocks adjacent to the current block deriving the intra prediction mode at a frequency exceeding any value in the decoder. Based on the intra prediction mode having the highest occurrence frequency in the intra prediction mode list being different from any mode in the MPM list, information indicating whether the intra prediction mode is derived in the decoder may be encoded.
Although the steps in the various flowcharts are described as being performed sequentially, these steps merely exemplify the technical concepts of some embodiments of the present disclosure. Accordingly, one of ordinary skill in the art to which the present disclosure pertains may perform the steps by changing the order depicted in the various figures or by performing more than two steps in parallel. Therefore, the steps in the respective flowcharts are not limited to the time series order shown.
It should be understood that the above description presents illustrative embodiments that may be implemented in various other ways. The functionality described in some embodiments may be implemented by hardware, software, firmware, and/or combinations thereof. It should also be appreciated that the functional components described in this specification are labeled with "units" to strongly emphasize their independent implementation possibilities.
Meanwhile, 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 apparatuses 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 memory drive, an optical disk drive, a magnetic hard disk drive, a Solid State Drive (SSD), and the like.
Although embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art to which the present disclosure pertains will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the present disclosure. Accordingly, embodiments of the present disclosure have been described for brevity and clarity. The scope of the technical idea of the embodiments of the present disclosure is not limited by the illustration. Accordingly, it will be understood by those of ordinary skill in the art to which this disclosure pertains that the scope of this disclosure is not limited to the embodiments explicitly described above, but is limited by the claims and their equivalents.
(reference numerals)
122. Intra-frame predictor
510. Entropy decoder
542. Intra-frame predictor
Cross Reference to Related Applications
The present application claims priority from korean patent application No. 10-2021-00740771, filed on 11 at 6 and 2022, and korean patent application No. 10-2022-0066258, filed on 30 at 5 and 2022, the contents of which are incorporated herein by reference in their entirety.

Claims (20)

1. A video decoding method, comprising:
generating an intra prediction mode list based on intra prediction modes of neighboring blocks adjacent to the current block;
selecting at least three intra-prediction modes from the intra-prediction mode list based on the number of intra-prediction modes occurring in the intra-prediction mode list being three or more;
Generating at least three prediction blocks based on the at least three intra prediction modes; and
a prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
2. The video decoding method of claim 1, wherein the at least three intra-prediction modes are the three intra-prediction modes with the highest occurrence frequency in the intra-prediction mode list.
3. The video decoding method of claim 1, wherein generating the prediction block of the current block by performing a weighted average on the at least three prediction blocks comprises: assigning weight values determined based on highest occurrence frequencies of the at least three intra prediction modes to the at least three prediction blocks, and adding the at least three prediction blocks to which the weight values are assigned.
4. The video decoding method of claim 1, further comprising:
selecting at least two intra prediction modes having highest occurrence frequencies from among the at least three intra prediction modes based on the absence of a plane mode among the at least three intra prediction modes;
generating the at least three prediction blocks based on the at least two intra prediction modes and a plane mode; and is also provided with
A prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
5. The video decoding method of claim 1, further comprising:
selecting one or two intra-prediction modes from a default mode set based on the number of intra-prediction modes occurring in the intra-prediction mode list being one or two;
generating the at least three prediction blocks based on the intra prediction modes occurring in the intra prediction mode list and based on the one or two intra prediction modes selected from the default mode set; and is also provided with
A prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
6. The video decoding method of claim 5, wherein the one or two intra-prediction modes selected from the default mode set do not overlap with the intra-prediction modes that occur in the intra-prediction mode list.
7. The video decoding method of claim 1, further comprising:
selecting one or two intra-prediction modes from the intra-prediction mode list based on the number of the intra-prediction modes appearing in the intra-prediction mode list being one or two;
Generating one or two prediction blocks based on the one or two intra prediction modes; and is also provided with
A prediction block of the current block is generated by performing a weighted average on the one or two prediction blocks.
8. The video decoding method of claim 1, further comprising:
information indicating whether the intra prediction mode is derived in a decoder is obtained based on the presence of at least one directional mode among intra prediction modes occurring in the intra prediction mode list or the presence of an intra prediction mode as at least one directional mode among neighboring blocks.
9. The video decoding method of claim 1, further comprising:
information indicating whether the intra prediction mode is derived in the decoder is obtained based on a frequency at which an intra prediction mode is derived in the decoder by a neighboring block at a specific position or a neighboring block adjacent to the current block exceeds any value.
10. The video decoding method of claim 1, further comprising:
information indicating whether the intra prediction mode is derived in a decoder is obtained based on the intra prediction mode having the highest occurrence frequency in the intra prediction mode list being different from any mode in an MPM (maximum probability mode) list.
11. A video encoding method, comprising:
generating an intra prediction mode list based on intra prediction modes of neighboring blocks adjacent to the current block;
selecting at least three intra-prediction modes from the intra-prediction mode list based on the number of intra-prediction modes occurring in the intra-prediction mode list being three or more;
generating at least three prediction blocks based on the at least three intra prediction modes; and
a prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
12. The video encoding method of claim 11, wherein the at least three intra-prediction modes are the three intra-prediction modes with the highest occurrence frequency in the intra-prediction mode list.
13. The video encoding method of claim 11, wherein generating the prediction block of the current block by performing a weighted average on the at least three prediction blocks comprises: assigning weight values determined based on highest occurrence frequencies of the at least three intra prediction modes to the at least three prediction blocks, and adding the at least three prediction blocks to which the weight values are assigned.
14. The video coding method of claim 11, further comprising:
selecting at least two intra-prediction modes having highest occurrence frequencies from the at least three intra-prediction modes based on the absence of a plane mode among the at least three intra-prediction modes;
generating the at least three prediction blocks based on the at least two intra prediction modes and a plane mode; and is also provided with
A prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
15. The video coding method of claim 11, further comprising:
selecting one or two intra-prediction modes from a default mode set based on the number of intra-prediction modes occurring in the intra-prediction mode list being one or two;
generating at least three prediction blocks based on the intra prediction modes occurring in the intra prediction mode list and based on the one or two intra prediction modes selected from the default mode set; and is also provided with
A prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
16. The video coding method of claim 11, further comprising:
Selecting one or two intra-prediction modes from the intra-prediction mode list based on the number of the intra-prediction modes appearing in the intra-prediction mode list being one or two;
generating one or two prediction blocks based on the one or two intra prediction modes; and is also provided with
A prediction block of the current block is generated by performing a weighted average on the one or two prediction blocks.
17. The video coding method of claim 11, further comprising:
information indicating whether the intra prediction mode is derived in a decoder is encoded based on the presence of at least one directional mode among intra prediction modes occurring in the intra prediction mode list or the presence of an intra prediction mode as at least one directional mode among neighboring blocks.
18. The video coding method of claim 11, further comprising:
information indicating whether the intra prediction mode is derived in the decoder is encoded based on a frequency at which an intra prediction mode is derived in the decoder at a neighboring block at a specific location or a neighboring block adjacent to the current block exceeds any value at which the intra prediction mode is derived in the decoder.
19. The video coding method of claim 11, further comprising:
information indicating whether the intra prediction mode is derived in a decoder is encoded based on the intra prediction mode having the highest occurrence frequency in the intra prediction mode list being different from any mode in an MPM (maximum probability mode) list.
20. A computer-readable recording medium having a bitstream generated by a video encoding method stored in the computer-readable recording medium, the video encoding method comprising:
generating an intra prediction mode list based on intra prediction modes of neighboring blocks adjacent to the current block;
selecting at least three intra-prediction modes from the intra-prediction mode list based on the number of intra-prediction modes occurring in the intra-prediction mode list being three or more;
generating at least three prediction blocks based on the at least three intra prediction modes; and
a prediction block of the current block is generated by performing a weighted average on the at least three prediction blocks.
CN202280041485.1A 2021-06-11 2022-05-31 Video encoding and decoding method and device Pending CN117461312A (en)

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KR10-2021-0076071 2021-06-11
KR10-2022-0066258 2022-05-30
KR1020220066258A KR20220167219A (en) 2021-06-11 2022-05-30 Method and apparatus for video encoding and decoding
PCT/KR2022/007767 WO2022260341A1 (en) 2021-06-11 2022-05-31 Video encoding/decoding method and device

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