Method and apparatus for video encoding / decoding using intra block copy

Abstract

Disclosed are a method and an apparatus for video encoding / decoding using intra block copy. The method for decoding video data comprises the steps of: decoding encoding information on a chroma block from a bitstream; determining to decode the chroma block using intra block copy based on the encoding information; identifying a pre-decoded luma block by using intra block copy within a luma region corresponding to the chroma block; deriving a block vector for the chroma block based on a block vector of the pre-decoded luma block; and deriving a prediction block of the chroma block based on the block vector for the chroma block.

Description

Technical Field

[0001] The present disclosure generally relates to methods, devices and storage media for video encoding / decoding. More specifically, the present disclosure relates to a method and device for video encoding / decoding based on intra-frame block replication. Background Art

[0002] With the continuous development of the information and communication industry, broadcast services supporting high definition (HD) resolution have become popular all over the world. Through this popularity, a large number of users have become accustomed to high-resolution and high-definition images and / or videos.

[0003] In order to meet the user's demand for high definition, many organizations have accelerated the development of next-generation imaging devices. User interest in UHD TV, which has a resolution more than four times that of full HD (FHD) TV, as well as high-definition TV (HDTV) and FHD TV has increased. As people's interest in it increases, image encoding / decoding technology for images with higher resolution and higher definition is currently required.

[0004] As the image compression technology, there are various technologies such as an inter-frame prediction technology, an intra-frame prediction technology, transform, a quantization technology, a filtering technology, and an entropy coding technology.

[0005] The inter-frame prediction technique is a technique for predicting the value of a pixel included in the current picture using a picture before and / or after the current picture. The intra-frame prediction technique is a technique for predicting the value of a pixel included in the current picture using information about the pixel in the current picture. The transform and quantization technique may be a technique for compressing the energy of the residual signal. The entropy coding technique is a technique for assigning short codewords to frequently occurring values ​​and assigning long codewords to less frequently occurring values.

[0006] By utilizing this image compression technology, data regarding images can be efficiently compressed, transmitted, and stored. Summary of the invention

[0007] Technical issues

[0008] The present disclosure provides methods for improving encoding and decoding processes using intra-frame block copying. Specifically, the present disclosure provides encoding and decoding processes for intra-frame block copying of various resolutions using block vectors. In addition, the present invention provides methods for efficiently using intra-frame block copying techniques for luma components and chroma components. For example, some techniques relate to methods for deriving block vectors for chroma component blocks from block vectors for luma component blocks, while other techniques relate to methods for minimizing the encoding information of residual blocks for both chroma components and luma components.

[0009] Technical Solution

[0010] In one example of the present invention, a method for encoding video data includes: determining to use intra-frame block copying to encode a chroma block in a current picture, identifying a previously encoded luminance block using intra-frame block copying in a luminance region corresponding to the chroma block, deriving a block vector of the chroma block based on a block vector of the previously encoded luminance block, deriving a prediction block of the chroma block, or encoding encoding information for the chroma block in a bitstream.

[0011] The method may further include determining a block vector resolution of the chroma block, wherein the block vector resolution is an integer pixel resolution or a fractional pixel resolution. The block vector resolution of the chroma block may be selected from a plurality of available resolutions. The block vector resolution of the chroma block may be determined separately for a horizontal direction component and a vertical direction component. The step of deriving the block vector of the chroma block may further include rounding a block vector of the previously encoded luminance block to the block vector resolution of the chroma block. The encoding information for the chroma block includes a syntax element indicating the block vector resolution for the chroma block among the plurality of available resolutions.

[0012] The tree type of the chroma block may be a single tree type. The step of identifying the previously encoded luma block may include searching for predefined sample positions in a luma region corresponding to the chroma block in a predefined order until a luma block previously encoded in an intra block copy mode containing at least one of the predefined sample positions is found. In this case, the tree type of the chroma block may be a dual tree type.

[0013] The encoding information for the chroma block may include: a syntax element indicating an intra-frame prediction mode for the chroma block, wherein the syntax element may indicate one of an intra-frame block copy mode, a planar mode, a DC mode, a vertical mode, a horizontal mode, a direct mode (DM), and a linear mode (LM).

[0014] The method may further include: generating a residual block for the current block based on the prediction block, wherein the encoding information for the chroma block may further include: residual data representing the residual block for the current block.

[0015] In one example of the present invention, a method for decoding video data includes: decoding encoding information for a chroma block from a bitstream, determining to use intra-block copying to decode the chroma block based on the encoding information, identifying a previously decoded luminance block using intra-block copying in a luminance region corresponding to the chroma block, deriving a block vector of the chroma block based on a block vector of the previously decoded luminance block, or deriving a prediction block of the chroma block based on the block vector of the chroma block.

[0016] In one example of the present invention, a non-transitory computer-readable storage medium stores instructions, wherein when the instructions are executed by one or more processors, the one or more processors are instructed to perform the following operations: determine to use intra-frame block copying to encode a chroma block in a current picture; identify a previously encoded luminance block using intra-frame block copying in a luminance region corresponding to the chroma block; derive a block vector of the chroma block based on a block vector of the previously encoded luminance block; derive a prediction block for the chroma block; and encode encoding information for the chroma block in a bitstream.

[0017] In one example of the present invention, a non-transitory computer-readable storage medium stores instructions, wherein when the instructions are executed by one or more processors, the one or more processors are instructed to perform the following operations: decode encoding information for a chroma block from a bitstream; determine to use intra-block copying to decode the chroma block based on the encoding information; identify a previously decoded luminance block using intra-block copying in a luminance region corresponding to the chroma block; derive a block vector of the chroma block based on a block vector of the previously decoded luminance block; and derive a prediction block of the chroma block based on the block vector of the chroma block.

[0018] Beneficial Effects

[0019] According to the present disclosure, encoding information (eg, a block vector) of a chroma component block to be encoded / decoded is derived from encoding information of the chroma component block based on intra block copying.

[0020] Furthermore, according to the present disclosure, various resolutions of block vectors may be utilized, thereby improving the performance of predicting blocks for encoding / decoding based on intra block copying. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a block diagram showing a configuration of an embodiment of an encoding device to which the present disclosure is applied;

[0022] Figure 2 is a block diagram showing a configuration of an embodiment of a decoding device to which the present disclosure is applied;

[0023] Figure 3 is a diagram schematically showing a partition structure of an image when the image is encoded and decoded;

[0024] Figure 4 is a diagram showing a form of a prediction unit (PU) that a coding unit (CU) may include;

[0025] Figure 5 is a diagram showing a form of a transform unit (TU) that may be included in a CU;

[0026] Figure 6 shows segmentation of blocks according to an example;

[0027] Figure 7 is a diagram for explaining an embodiment of an intra prediction process;

[0028] Figure 8 is a diagram showing reference samples used in an intra prediction process;

[0029] Fig. 9 is a diagram for explaining an embodiment of an inter-frame prediction process;

[0030] Fig.10 shows spatial candidates according to an embodiment;

[0031] Fig.11 shows the order in which motion information of spatial candidates is added to a merge list according to an embodiment;

[0032] Fig.12 shows a transform and quantization process according to an example;

[0033] Fig.13 shows a diagonal scan according to an example;

[0034] Fig.14 shows a horizontal scan according to an example;

[0035] Fig.15 shows vertical scanning according to an example;

[0036] Fig.16 is a configuration diagram of an encoding device according to an embodiment;

[0037] Fig.17 is a configuration diagram of a decoding device according to an embodiment;

[0038] Fig.18 A method of encoding a block of video data using intra-block copying according to an embodiment of the present disclosure is shown;

[0039] Fig.19 A method of decoding a block of video data using intra-block copying according to an embodiment of the present disclosure is shown;

[0040] Fig. 20 shows exemplary positions of current block and prediction block;

[0041] Fig.21 A method for determining prediction block vector candidates is shown;

[0042] Fig. 22 A pattern showing partitioning of a parent block into child blocks to be encoded / decoded in intra block copy mode;

[0043] Fig.23 A conceptual diagram showing a list of block vector candidates that share a parent block position with a child block;

[0044] Fig.24 shows the amvr_precisions set when num_amvr_precision is 4;

[0045] Fig.25 shows the amvr_precisions set and the additional_amvr_precisions set when num_amvr_precisions is 4 and num_additional_amvr_precisions is 3;

[0046] Fig.26 An example of determining a relative position of a reference prediction block specified by a block vector relative to a current block is shown;

[0047] Fig. 27 shows a 64×64 block to which a reference block for intra block copy may belong;

[0048] Fig.28 An example showing a region encoded / decoded before a current block and a reference region buffer for intra block copy;

[0049] Fig.29 A reference region buffer is shown;

[0050] Fig.30 shows an example of a region encoded / decoded before the current block;

[0051] Fig.31 shows the state of the reference region buffer changing as the CTB is encoded / decoded;

[0052] Fig.32 An example of partitioning a CTU having a 4:2:0 chroma format according to a dual-tree structure is shown;

[0053] Fig.33 An example of partitioning a chroma component block and a luma component block into respective sub-blocks in an example of partitioning a CTU having a 4:2:0 chroma format according to a dual-tree structure is shown;

[0054] Fig.34 Showing the sub-blocks of the luminance component block and the specific sample point positions within each sub-block;

[0055] Fig.35 shows a process for deriving a prediction block for a current luma component block;

[0056] Fig.36An example is shown in which the prediction coding mode of the luminance component sub-block corresponding to the chrominance component block is the same;

[0057] Fig.37 An example is shown in which the prediction coding mode of the luminance component sub-block corresponding to the chrominance component block is different;

[0058] Fig.38 and Fig.39 An exemplary syntax structure that may be used to signal coding information related to intra-block copying is shown;

[0059] Fig.40 An example of a method for signaling encoding information after redundancy in the signaled cu_cbf information and tu_cbf_luma information has been removed is shown;

[0060] Fig.41 Another example of a method for signaling encoding information after redundancy in the signaled cu_cbf information and tu_cbf_luma information has been removed is shown; and

[0061] Fig.42 Still another example of a method for signaling encoding information after redundancy in the signaled cu_cbf information and tu_cbf_luma information has been removed is shown. DETAILED DESCRIPTION

[0062] The present invention can be variously modified and can have various embodiments, and specific embodiments will be described in detail below with reference to the accompanying drawings. However, it should be understood that those embodiments are not intended to limit the present invention to a specific disclosed form, and they include all changes, equivalents or modifications included in the spirit and scope of the present invention.

[0063] The following detailed description of exemplary embodiments will be made with reference to the accompanying drawings showing specific embodiments. These embodiments are described so that a technician with ordinary knowledge in the technical field to which the present disclosure belongs can easily practice the embodiments. It should be noted that the various embodiments are different from each other, but do not need to be mutually exclusive. For example, without departing from the spirit and scope of the embodiments related to the embodiments, the specific shapes, structures and characteristics described herein may be implemented as other embodiments. In addition, it should be understood that the position or arrangement of each component in each disclosed embodiment may be changed without departing from the spirit and scope of the embodiments. Therefore, the attached detailed description is not intended to limit the scope of the present disclosure, and the scope of the exemplary embodiments is limited only by the attached claims and their equivalents, as long as they are appropriately described.

[0064] In the drawings, like reference numerals are used to designate the same or similar functions in various aspects. The shapes, sizes, etc. of components in the drawings may be exaggerated to make the description clear.

[0065] Terms such as "first" and "second" may be used to describe various components, but the components are not limited by the terms. These terms are only used to distinguish one component from another component. For example, without departing from the scope of this specification, a first component may be named a second component. Similarly, a second component may be named a first component. The term "and / or" may include a combination of multiple related description items or any one of multiple related description items.

[0066] It will be understood that when a component is referred to as being "connected" or "coupled" to another component, the two components may be directly connected or coupled to each other, or there may be an intermediate component between the two components. On the other hand, it will be understood that when a component is referred to as being "directly connected or coupled", there are no intermediate components between the two components.

[0067] In addition, in order to indicate different characteristic functions, the components described in the embodiments are shown independently, but this does not mean that each of the components is formed by separate hardware or software. That is, for ease of description, the components are arranged and included separately. For example, at least two of the components can be integrated into a single component. On the contrary, a component can be divided into multiple components. An embodiment of an integrated component or an embodiment of separating some components is included in the scope of this specification as long as it does not depart from the essence of this specification.

[0068] The terms used in the embodiments are only used to describe specific embodiments and are not intended to limit the present invention. Unless otherwise specifically indicated in the context, singular expressions include plural expressions. In an embodiment, it should be understood that terms such as "including" or "having" are only intended to indicate the presence of features, numbers, steps, operations, components, parts, or a combination thereof, and are not intended to exclude the possibility of having or adding one or more other features, numbers, steps, operations, components, parts, or a combination thereof. That is, in an embodiment, the expression that describes a component "including" a specific component means that other components may be included within the scope of the practice of the present invention or the technical spirit of the present invention, but does not exclude the presence of components other than the specific components.

[0069] In an embodiment, the term "at least one" may mean one of 1 or more numbers, such as 1, 2, 3, and 4. In an embodiment, the term "plurality" may mean one of 2 or more numbers, such as 2, 3, and 4.

[0070] Some components of the embodiment are not essential components for performing essential functions, but may be optional components for only improving performance. The embodiment may be implemented using only the essential components for realizing the essence of the embodiment. For example, a structure including only essential components and not including optional components used only to improve performance is also included in the scope of the embodiment.

[0071] The embodiments will be described in detail below with reference to the accompanying drawings so that a person with ordinary knowledge in the technical field to which the embodiments belong can easily practice the embodiments. In the following description of the embodiments, detailed descriptions of known functions or configurations that are considered to obscure the subject matter of this specification will be omitted. In addition, throughout the drawings, the same reference numerals are used to designate the same components, and repeated descriptions of the same components will be omitted.

[0072] Hereinafter, "image" may refer to a single picture constituting a video, or may refer to the video itself. For example, "encoding and / or decoding of an image" may refer to "encoding and / or decoding of a video", and may also refer to "encoding and / or decoding of any one of the images constituting the video".

[0073] Hereinafter, the terms 'video' and 'moving picture' may be used to have the same meaning and may be used interchangeably with each other.

[0074] Hereinafter, a target image may be an encoding target image as a target to be encoded and / or a decoding target image as a target to be decoded. In addition, the target image may be an input image input to an encoding device or an input image input to a decoding device. And, the target image may be a current image, that is, a target to be currently encoded and / or decoded. For example, the terms "target image" and "current image" may be used to have the same meaning and may be used interchangeably with each other.

[0075] Hereinafter, the terms “image”, “picture”, “frame”, and “screen” may be used to have the same meaning and may be used interchangeably with each other.

[0076] Hereinafter, the target block may be an encoding target block (a target to be encoded) and / or a decoding target block (a target to be decoded). In addition, the target block may be a current block, that is, a target to be encoded and / or decoded at present. Here, the terms "target block" and "current block" may be used to have the same meaning and may be used interchangeably with each other. The current block may represent an encoding target block that is an encoding target during encoding and / or a decoding target block that is a decoding target during decoding. In addition, the current block may be at least one of a coding block, a prediction block, a residual block, and a transform block.

[0077] Hereinafter, the terms "block" and "unit" may be used to have the same meaning and may be used interchangeably with each other. Alternatively, a "block" may refer to a specific unit.

[0078] Hereinafter, the terms "region" and "segment" may be used interchangeably with each other.

[0079] In the following embodiments, specific information, data, flags, indexes, elements, and attributes may have their respective values. The value "0" corresponding to each of the information, data, flags, indexes, elements, and attributes may indicate false, logically false, or a first predefined value. In other words, the value "0", false, logically false, and the first predefined value may be used interchangeably. The value "1" corresponding to each of the information, data, flags, indexes, elements, and attributes may indicate true, logically true, or a second predefined value. In other words, the value "1", true, logically true, and the second predefined value may be used interchangeably.

[0080] When a variable such as i or j is used to indicate a row, column, or index, the value of i may be an integer of 0 or greater or may be an integer of 1 or greater. In other words, in an embodiment, each of the row, column, and index may be counted from 0 or may be counted from 1.

[0081] In an embodiment, the term “one or more” or the term “at least one” may mean the term “plurality.” The term “one or more” or the term “at least one” may be used interchangeably with “plurality.”

[0082] Hereinafter, terms to be used in the embodiments will be described.

[0083] Encoder: An encoder refers to a device for performing encoding. That is, an encoder may mean an encoding device.

[0084] Decoder: A decoder refers to a device for performing decoding. That is, a decoder may mean a decoding apparatus.

[0085] Unit: A unit may mean a unit of image encoding and decoding. The terms "unit" and "block" may be used to have the same meaning and may be used interchangeably with each other.

[0086] - A cell may be an M×N array of samples. Each of M and N may be a positive integer. A cell may generally mean an array of samples in a two-dimensional form.

[0087] - In encoding and decoding of an image, a "unit" may be a region generated by partitioning one image. In other words, a "unit" may be a region specified in one image. A single image may be partitioned into a plurality of units. Alternatively, one image may be partitioned into sub-parts, and when encoding or decoding is performed on the partitioned sub-parts, a unit may represent each of the partitioned sub-parts.

[0088] - In encoding and decoding of images, a predefined process may be performed on each unit according to the type of the unit.

[0089] - According to functions, the unit type may be classified into a macro unit, a coding unit (CU), a prediction unit (PU), a residual unit, a transform unit (TU), etc. Alternatively, according to functions, the unit may represent a block, a macro block, a coding tree unit, a coding tree block, a coding unit, a coding block, a prediction unit, a prediction block, a residual unit, a residual block, a transform unit, a transform block, etc. For example, a target unit as a target of encoding and / or decoding may be at least one of a CU, a PU, a residual unit, and a TU.

[0090] - The term "unit" may mean information including a luma component block, a chroma component block corresponding to the luma component block, and syntax elements for each block, so that the unit is designated to be distinguished from the block.

[0091] - The size and shape of the unit can be achieved in various ways. In addition, the unit can have any of a variety of sizes and shapes. In particular, the shape of the unit can include not only a square, but also a geometric figure that can be represented in two dimensions (2D), such as a rectangle, a trapezoid, a triangle, and a pentagon.

[0092] - In addition, the unit information may include one or more of a type of unit, a size of the unit, a depth of the unit, an encoding order of the unit, and a decoding order of the unit, etc. For example, the type of the unit may indicate one of CU, PU, ​​residual unit, and TU.

[0093] - A cell can be partitioned into sub-cells, each sub-cell having a size smaller than that of the associated cell.

[0094] Depth: Depth may mean the degree to which a unit is partitioned. In addition, the depth of a unit may indicate the level at which the corresponding unit exists when (one or more) units are represented by a tree structure.

[0095] - The cell partition information may include a depth indicating the depth of the cell. The depth may indicate the number of times the cell is partitioned and / or the extent to which the cell is partitioned.

[0096] -In a tree structure, the root node can be considered to have the smallest depth and the leaf node can be considered to have the largest depth. The root node can be the highest (top) node. The leaf node can be the lowest node.

[0097] - A single unit may be hierarchically partitioned into a plurality of subunits while having depth information based on a tree structure. In other words, a unit and a subunit generated by partitioning the unit may correspond to a node and a subnode of the node, respectively. Each of the partitioned subunits may have a unit depth. Since the depth indicates the number of times a unit is partitioned and / or the degree to which a unit is partitioned, the partition information of the subunit may include information about the size of the subunit.

[0098] - In the tree structure, the top node may correspond to the initial node before partitioning. The top node may be referred to as a "root node". In addition, the root node may have a minimum depth value. Here, the top node may have a depth of level "0".

[0099] - A node with a depth of level "1" may represent a cell generated when the initial cell is partitioned once. A node with a depth of level "2" may represent a cell generated when the initial cell is partitioned twice.

[0100] - A leaf node with a depth of level "n" may represent a cell generated when the initial cell has been partitioned n times.

[0101] - A leaf node may be a bottom node, which cannot be partitioned further. The depth of a leaf node may be a maximum level. For example, the predefined value of the maximum level may be 3.

[0102] -QT depth may represent the depth used for quad-partitioning. BT depth may represent the depth used for binary-partitioning. TT depth may represent the depth used for ternary-partitioning.

[0103] Sample: Samples can be the basic unit of a block. Depending on the bit depth (Bd), it can be from 0 to 2. Bd A value of -1 indicates a sample point.

[0104] - A sample can be a pixel or a pixel value.

[0105] - Hereinafter, the terms "pixel" and "sample" may be used to have the same meaning and may be used interchangeably with each other.

[0106] Coding Tree Unit (CTU): A CTU may consist of a single luma component (Y) coding tree block and two chroma component (Cb, Cr) coding tree blocks related to the luma component coding tree block. In addition, CTU may mean information including the above blocks and syntax elements for each of the blocks.

[0107] - Each coding tree unit (CTU) may be partitioned using one or more partitioning methods such as quadtree (QT), binary tree (BT), and ternary tree (TT) to configure sub-units such as coding units, prediction units, and transform units. Quadtree may mean a quadtree. In addition, one or more partitioning methods may be used to partition each coding tree unit using a multi-type tree (MTT).

[0108] - "CTU" may be used as a term to designate a pixel block, which is a processing unit in image decoding and encoding processes, such as in the case of a partition of an input image.

[0109] Coding Tree Block (CTB): “CTB” may be used as a term to designate any one of a Y coding tree block, a Cb coding tree block, and a Cr coding tree block.

[0110] Neighboring block: A neighboring block (or neighboring block) may mean a block adjacent to a target block. A neighboring block may mean a reconstructed neighboring block.

[0111] Hereinafter, the terms “neighboring block” and “adjacent block” may be used to have the same meaning and may be used interchangeably with each other.

[0112] The neighboring block may mean a reconstructed neighboring block.

[0113] Spatial neighboring blocks: Spatial neighboring blocks may be blocks that are spatially adjacent to the target block. Neighboring blocks may include spatial neighboring blocks.

[0114] - A target block and spatially neighboring blocks may be included in a target picture.

[0115] - A spatially neighboring block may mean a block whose boundary contacts the target block, or a block located within a predetermined distance from the target block.

[0116] - A spatially adjacent block may mean a block adjacent to a vertex of the target block. Here, a block adjacent to a vertex of the target block may mean a block vertically adjacent to a neighboring block horizontally adjacent to the target block or a block horizontally adjacent to a neighboring block vertically adjacent to the target block.

[0117] Temporal neighboring blocks: Temporal neighboring blocks may be blocks that are temporally adjacent to the target block. Neighboring blocks may include temporal neighboring blocks.

[0118] - Temporally neighboring blocks may include co-located blocks (col blocks).

[0119] The col block may be a block in a previously reconstructed co-located picture (col picture). The position of the col block in the col picture may correspond to the position of the target block in the target picture. Alternatively, the position of the col block in the col picture may be equal to the position of the target block in the target picture. The col picture may be a picture included in a reference picture list.

[0120] - The temporal neighboring block may be a block that is temporally adjacent to the spatial neighboring block of the target block.

[0121] Prediction mode: The prediction mode may be information indicating a mode for intra prediction or a mode for inter prediction.

[0122] Prediction unit: A prediction unit may be a basic unit for prediction such as inter prediction, intra prediction, inter compensation, intra compensation, and motion compensation.

[0123] - A single prediction unit can be divided into multiple partitions or sub-prediction units with smaller sizes. Multiple partitions can also be basic units in the execution of prediction or compensation. Partitions generated by dividing a prediction unit can also be prediction units.

[0124] Prediction unit partition: A prediction unit partition may be a shape into which a prediction unit is divided.

[0125] Reconstructed neighboring unit: The reconstructed neighboring unit may be an already decoded and reconstructed unit that is neighboring to the target unit.

[0126] The reconstructed neighboring cell may be a cell that is spatially adjacent to the target cell or temporally adjacent to the target cell.

[0127] The reconstructed spatially neighboring unit may be a unit that is included in the target picture and has been reconstructed through encoding and / or decoding.

[0128] -The reconstructed temporally adjacent unit may be a unit that is included in a reference image and has been reconstructed by encoding and / or decoding. The position of the reconstructed temporally adjacent unit in the reference image may be the same as the position of the target unit in the target picture, or may correspond to the position of the target unit in the target picture. In addition, the reconstructed temporally adjacent unit may be a block that is adjacent to a corresponding block in the reference image. Here, the position of the corresponding block in the reference image may correspond to the position of the target block in the target image. Here, the fact that the positions of the blocks correspond to each other may mean that the positions of the blocks are the same as each other, may mean that one block is included in another block, or may mean that one block occupies a specific position in another block.

[0129] Sub-picture: A picture can be divided into one or more sub-pictures. A sub-picture can be composed of one or more tile rows and one or more tile columns.

[0130] - A sub-picture may be a region in a picture having a square shape or a rectangular (ie, non-square rectangular) shape. In addition, a sub-picture may include one or more CTUs.

[0131] - A sub-picture can be a rectangular area of ​​one or more slices in a picture.

[0132] - A sub-picture may include one or more tiles, one or more partitions and / or one or more slices.

[0133] Tile: A tile may be an area in a picture having a square shape or a rectangular (ie, non-square rectangular) shape.

[0134] - A tile may include one or more CTUs.

[0135] - A tile can be partitioned into one or more partitions.

[0136] Block: A block may represent one or more CTU rows in a tile.

[0137] - A tile can be partitioned into one or more partitions. Each partition can include one or more CTU rows.

[0138] -A parallel block that is not partitioned into two parts can also represent a partition.

[0139] Slice: A slice may include one or more tiles in a picture. Alternatively, a slice may include one or more partitions in a tile.

[0140] - A sub-picture may contain one or more slices that together cover a rectangular area of ​​the picture. Thus, every sub-picture boundary is always also a slice boundary, and every vertical sub-picture boundary is always also a vertical tile boundary.

[0141] Parameter set: A parameter set may correspond to header information in the internal structure of a bitstream.

[0142] The parameter set may include at least one of a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a decoding parameter set (DPS), etc.

[0143] - Information signaled by each parameter set may be applied to pictures that reference the corresponding parameter set. For example, information in a VPS may be applied to pictures that reference the VPS. Information in an SPS may be applied to pictures that reference the SPS. Information in a PPS may be applied to pictures that reference the PPS.

[0144] -Each parameter set can refer to a higher parameter set. For example, PPS can refer to SPS. SPS can refer to VPS.

[0145] - In addition, the parameter set may include a parallel block group, a slice header information, and a parallel block header information. A parallel block group may be a group including a plurality of parallel blocks. In addition, the meaning of "parallel block group" may be the same as the meaning of "slice".

[0146] Rate-distortion optimization: The encoding device may use rate-distortion optimization in order to provide high encoding efficiency by utilizing a combination of the size of a coding unit (CU), a prediction mode, the size of a prediction unit (PU), motion information, and the size of a transform unit (TU).

[0147] -The rate-distortion optimization scheme can calculate the rate-distortion cost of each combination in order to select the best combination from the combinations. The rate-distortion cost can be calculated using the equation "D+(λ×R)". Generally, the combination that can minimize the rate-distortion cost can be selected as the optimal combination in the rate-distortion optimization scheme.

[0148] -D may represent distortion. D may be the mean of the squares of the differences between the original transform coefficients and the reconstructed transform coefficients in the transform unit (ie, the mean square error).

[0149] -R may represent rate, which may represent the bit rate using relevant context information.

[0150] -λ represents a Lagrange multiplier. R may include not only encoding parameter information such as prediction mode, motion information, and coding block flag, but also bits generated due to encoding of transform coefficients.

[0151] - The encoding device may perform processes such as inter-frame prediction and / or intra-frame prediction, transformation, quantization, entropy coding, inverse quantization (dequantization) and / or inverse transformation in order to calculate accurate D and R. These processes may greatly increase the complexity of the encoding device.

[0152] - Bitstream: A bitstream may refer to a stream of bits including encoded image information.

[0153] Parsing: Parsing may be the decision on the value of a syntax element made by performing entropy decoding on the bitstream. Alternatively, the term "parsing" may mean such entropy decoding itself.

[0154] Symbol: A symbol may be at least one of a syntax element, a coding parameter, and a transform coefficient of a coding target unit and / or a decoding target unit. In addition, a symbol may be a target of entropy coding or a result of entropy decoding.

[0155] Reference picture: A reference picture may be an image referenced by a unit in order to perform inter-frame prediction or motion compensation. Alternatively, a reference picture may be an image including a reference unit referenced by a target unit in order to perform inter-frame prediction or motion compensation.

[0156] Hereinafter, the terms 'reference picture' and 'reference image' may be used to have the same meaning and may be used interchangeably with each other.

[0157] Reference picture list: A reference picture list may be a list including one or more reference pictures used for inter prediction or motion compensation.

[0158] - The types of reference picture lists may include List Combination (LC), List 0 (L0), List 1 (L1), List 2 (L2), List 3 (L3), etc.

[0159] - For inter prediction, one or more reference picture lists may be used.

[0160] Inter prediction indicator: The inter prediction indicator may indicate the inter prediction direction for the target unit. The inter prediction may be one of unidirectional prediction and bidirectional prediction. Optionally, the inter prediction indicator may indicate the number of reference pictures used to generate the prediction unit for the target unit. Optionally, the inter prediction indicator may indicate the number of prediction blocks used for inter prediction or motion compensation for the target unit.

[0161] Prediction list utilization flag: The prediction list utilization flag may indicate whether at least one reference picture in a specific reference picture list is used to generate a prediction unit.

[0162] - The prediction list utilization flag may be used to derive the inter prediction indicator. Conversely, the prediction list utilization flag may be used to derive the prediction list utilization flag. For example, the case where the prediction list utilization flag indicates "0" as a first value may indicate that, for the target unit, the reference picture in the reference picture list is not used to generate the prediction block. The case where the prediction list utilization flag indicates "1" as a second value may indicate that, for the target unit, the reference picture list is used to generate the prediction unit.

[0163] Reference picture index: A reference picture index may be an index indicating a specific reference picture in a reference picture list.

[0164] Picture Order Count (POC): The POC value of a picture may indicate the order in which the corresponding picture is displayed.

[0165] Motion Vector (MV): A motion vector may be a 2D vector used for inter prediction or motion compensation. A motion vector may mean the offset between a target image and a reference image.

[0166] - For example, MV can be represented as (mv x ,mv y ) format. x Can indicate the horizontal component, and mv y May indicate the vertical component.

[0167] - Search range: The search range may be a 2D area where the search of the MV is performed during inter prediction. For example, the size of the search range may be M×N. M and N may be respective positive integers.

[0168] Motion vector candidate: A motion vector candidate may be a block that is a prediction candidate when predicting a motion vector or a motion vector of a block that is a prediction candidate.

[0169] -The motion vector candidate may be included in the motion vector candidate list.

[0170] Motion vector candidate list: A motion vector candidate list may be a list configured using one or more motion vector candidates.

[0171] Motion vector candidate index: The motion vector candidate index may be an indicator for indicating a motion vector candidate in a motion vector candidate list. Alternatively, the motion vector candidate index may be an index of a motion vector predictor.

[0172] Motion information: The motion information may be information including at least one of a reference picture list, a reference image, a motion vector candidate, a motion vector candidate index, a merge candidate, and a merge index, as well as a motion vector, a reference picture index, and an inter prediction indicator.

[0173] Merge candidate list: A merge candidate list may be a list configured using one or more merge candidates.

[0174] Merge candidates: The merge candidates may be spatial merge candidates, temporal merge candidates, combined merge candidates, combined bi-predictive merge candidates, history-based candidates, candidates based on the average of two candidates, zero merge candidates, etc. The merge candidates may include an inter prediction indicator and may include motion information such as prediction type information, reference picture index for each list, motion vector, prediction list utilization flag, and inter prediction indicator.

[0175] Merge index: The merge index may be an indicator for indicating a merge candidate in the merge candidate list.

[0176] - The merge index may indicate a reconstructed unit used for deriving a merge candidate between a reconstructed unit spatially adjacent to the target unit and a reconstructed unit temporally adjacent to the target unit.

[0177] - The merge index may indicate at least one of a plurality of pieces of motion information of a merge candidate.

[0178] Transform unit: A transform unit may be a basic unit of residual signal encoding and / or residual signal decoding (such as transform, inverse transform, quantization, inverse quantization, transform coefficient encoding, and transform coefficient decoding). A single transform unit may be partitioned into a plurality of sub-transform units having a smaller size. Here, the transform may include one or more of a primary transform and a secondary transform, and the inverse transform may include one or more of a primary inverse transform and a secondary inverse transform.

[0179] Scaling: Scaling may refer to the process of multiplying the levels of transform coefficients by a factor.

[0180] - As a result of scaling of the transform coefficient levels, the transform coefficients may be generated. Scaling may also be referred to as "inverse quantization".

[0181] Quantization parameter (QP): A quantization parameter may be a value used to generate a transform coefficient level for a transform coefficient in quantization. Alternatively, a quantization parameter may also be a value used to generate a transform coefficient by scaling the transform coefficient level in inverse quantization. Alternatively, a quantization parameter may be a value mapped to a quantization step size.

[0182] Delta quantization parameter: The delta quantization parameter may mean the difference between the predicted quantization parameter and the quantization parameter of the target unit.

[0183] Scanning: Scanning may refer to a method for aligning the order of coefficients in a cell, block, or matrix. For example, a method for aligning a 2D array in the form of a one-dimensional (1D) array may be referred to as "scanning". Alternatively, a method for aligning a 1D array in the form of a 2D array may also be referred to as "scanning" or "inverse scanning".

[0184] Transform coefficient: The transform coefficient may be a coefficient value generated when the encoding device performs transformation. Alternatively, the transform coefficient may be a coefficient value generated when the decoding device performs at least one of entropy decoding and inverse quantization.

[0185] - Quantization levels or quantized transform coefficient levels generated by applying quantization to transform coefficients or residual signals may also be included in the meaning of the term "transform coefficient".

[0186] Quantization level: The quantization level may be a value generated when the encoding device performs quantization on a transform coefficient or a residual signal. Alternatively, the quantization level may be a value that is a target of inverse quantization when the decoding device performs inverse quantization.

[0187] -The quantized transform coefficient level as a result of transformation and quantization may also be included in the meaning of the quantization level.

[0188] Non-zero transform coefficient: A non-zero transform coefficient may be a transform coefficient having a value other than 0 or a transform coefficient level having a value other than 0. Alternatively, a non-zero transform coefficient may be a transform coefficient whose value is not zero or a transform coefficient level whose value is not zero.

[0189] Quantization matrix: A quantization matrix may be a matrix used in a quantization process or an inverse quantization process to improve the subjective image quality or objective image quality of an image. A quantization matrix may also be referred to as a "scaling list".

[0190] Quantization matrix coefficient: A quantization matrix coefficient can be each element in the quantization matrix. A quantization matrix coefficient can also be called a "matrix coefficient".

[0191] Default matrix: The default matrix may be a quantization matrix predefined by an encoding device and a decoding device.

[0192] Non-default matrix: A non-default matrix may be a quantization matrix that is not predefined by the encoding device and the decoding device. A non-default matrix may mean a quantization matrix that is signaled by a user from the encoding device to the decoding device.

[0193] Most Probable Mode (MPM): The MPM may represent an intra prediction mode having a high probability of being used for intra prediction of a target block.

[0194] The encoding apparatus and the decoding apparatus may determine one or more MPMs based on an encoding parameter associated with the target block and a property of an entity associated with the target block.

[0195] The encoding device and the decoding device may determine one or more MPMs based on the intra prediction mode of the reference block. The reference block may include multiple reference blocks. The multiple reference blocks may include a spatially adjacent block adjacent to the left side of the target block and a spatially adjacent block adjacent to the top of the target block. In other words, depending on which intra prediction modes have been used for the reference block, one or more different MPMs may be determined.

[0196] - One or more MPMs may be determined in the same manner in the encoding device and the decoding device. That is, the encoding device and the decoding device may share the same MPM list including the one or more MPMs.

[0197] MPM list: The MPM list may be a list including one or more MPMs. The number of the one or more MPMs in the MPM list may be predefined.

[0198] MPM indicator: The MPM indicator may indicate an MPM to be used for intra prediction of a target block among one or more MPMs in an MPM list. For example, the MPM indicator may be an index to the MPM list.

[0199] - Since the MPM list is determined in the same manner in the encoding device and the decoding device, there is no need to transmit the MPM list itself from the encoding device to the decoding device.

[0200] - The MPM indicator may be signaled from the encoding apparatus to the decoding apparatus. When the MPM indicator is signaled, the decoding apparatus may determine an MPM to be used for intra prediction of a target block among the MPMs in the MPM list.

[0201] MPM usage indicator: The MPM usage indicator may indicate whether an MPM usage mode is to be used for prediction of a target block. The MPM usage mode may be a mode of determining an MPM to be used for intra prediction of a target block using an MPM list.

[0202] - An MPM usage indicator may be signaled from an encoding device to a decoding device.

[0203] Signaling: "Signaling" may mean that information is transmitted from an encoding device to a decoding device. Alternatively, "signaling" may mean that the information is included in a bitstream or a recording medium by the encoding device. The information signaled by the encoding device may be used by the decoding device.

[0204] -The encoding device may generate encoding information by performing encoding on information to be transmitted with a signal. The encoding information may be sent from the encoding device to the decoding device. The decoding device may obtain the information by decoding the transmitted encoding information. Here, the encoding may be entropy encoding, and the decoding may be entropy decoding.

[0205] Selective signaling: Information may be selectively signaled. Selective signaling of information may mean that an encoding device selectively includes the information in a bitstream or a recording medium (according to certain conditions). Selective signaling of information may mean that a decoding device selectively extracts the information from a bitstream (according to certain conditions).

[0206] Omission of signaling: Signaling for information may be omitted. Omission of signaling for information may mean that the encoding device (according to certain conditions) does not include the information in the bitstream or recording medium. Omission of signaling for information may mean that the decoding device (according to certain conditions) does not extract the information from the bitstream.

[0207] Statistical value: A variable, encoding parameter, constant, etc. may have a computable value. A statistical value may be a value generated by performing a calculation (operation) on the value of a specified target. For example, a statistical value may indicate one or more of an average value, a weighted average value, a weighted sum, a minimum value, a maximum value, a modulus value, a median value, and an interpolated value of the values ​​of a particular variable, a particular encoding parameter, a particular constant, etc.

[0208] Figure 1 is a block diagram showing the configuration of an embodiment of an encoding device to which the present disclosure is applied.

[0209] The encoding device 100 may be an encoder, a video encoding device, or an image encoding device. A video may include one or more images (pictures). The encoding device 100 may sequentially encode one or more images of a video.

[0210] Reference Figure 1 , the encoding device 100 includes an inter-frame prediction unit 110, an intra-frame prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, an entropy encoding unit 150, an inverse quantization (inverse quantization) unit 160, an inverse transform unit 170, an adder 175, a filter unit 180 and a reference picture buffer 190.

[0211] The encoding apparatus 100 may perform encoding on a target image using an intra mode and / or an inter mode. In other words, a prediction mode for a target block may be one of an intra mode and an inter mode.

[0212] Hereinafter, the terms “intra mode”, “intra prediction mode”, “intra-screen mode”, and “intra-screen prediction mode” may be used to have the same meaning and may be used interchangeably with each other.

[0213] Hereinafter, the terms “inter mode”, “inter prediction mode”, “inter-picture mode” and “inter-picture prediction mode” may be used to have the same meaning and may be used interchangeably with each other.

[0214] Hereinafter, the term "image" may indicate only a portion of an image, or may indicate a block. In addition, processing of an "image" may indicate sequential processing of a plurality of blocks.

[0215] In addition, the encoding device 100 may generate a bitstream including encoding information by encoding the target image, and may output and store the generated bitstream. The generated bitstream may be stored in a computer-readable storage medium and may be streamed through a wired and / or wireless transmission medium.

[0216] When the intra mode is used as the prediction mode, the switch 115 may switch to the intra mode. When the inter mode is used as the prediction mode, the switch 115 may switch to the inter mode.

[0217] The encoding apparatus 100 may generate a prediction block of the target block. In addition, after generating the prediction block, the encoding apparatus 100 may encode a residual block of the target block using a residual between the target block and the prediction block.

[0218] When the prediction mode is the intra mode, the intra prediction unit 120 may use pixels of a previously encoded / decoded neighboring block adjacent to the target block as reference samples. The intra prediction unit 120 may perform spatial prediction on the target block using the reference samples, and may generate prediction samples for the target block via spatial prediction. The prediction samples may refer to samples in the prediction block.

[0219] The inter prediction unit 110 may include a motion prediction unit and a motion compensation unit.

[0220] When the prediction mode is the inter mode, the motion prediction unit may search the reference image for an area that most closely matches the target block during the motion prediction process, and may derive a motion vector for the target block and the found area based on the found area. Here, the motion prediction unit may use the search range as the target area for the search.

[0221] The reference image may be stored in the reference picture buffer 190. More specifically, when encoding and / or decoding of the reference image has been processed, the encoded and / or decoded reference image may be stored in the reference picture buffer 190.

[0222] Since the decoded pictures are stored, the reference picture buffer 190 may be a decoded picture buffer (DPB).

[0223] The motion compensation unit may generate a prediction block for the target block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional (2D) vector for inter-frame prediction. In addition, the motion vector may indicate an offset between a target image and a reference image.

[0224] When the motion vector has a value other than an integer, the motion prediction unit and the motion compensation unit may generate a prediction block by applying an interpolation filter to a partial area of ​​the reference image. In order to perform inter prediction or motion compensation, it may be determined which of the skip mode, merge mode, advanced motion vector prediction (AMVP) mode, and current picture reference mode corresponds to a method for predicting the motion of a PU included in a CU based on the CU and compensating for the motion, and inter prediction or motion compensation may be performed according to the mode.

[0225] The subtractor 125 may generate a residual block, which is the difference between the target block and the prediction block. The residual block may also be referred to as a "residual signal".

[0226] The residual signal may be the difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by transforming or quantizing the difference between the original signal and the prediction signal or by transforming and quantizing the difference. The residual block may be a residual signal for a block unit.

[0227] The transform unit 130 may generate a transform coefficient by transforming the residual block, and may output the generated transform coefficient. Here, the transform coefficient may be a coefficient value generated by transforming the residual block.

[0228] The transform unit 130 may use one of a plurality of predefined transform methods when performing the transform.

[0229] The plurality of predefined transform methods may include discrete cosine transform (DCT), discrete sine transform (DST), Karhunen-Loeve transform (KLT), and the like.

[0230] The transform method for transforming the residual block may be determined according to at least one of the encoding parameters for the target block and / or the neighboring block. For example, the transform method may be determined based on at least one of the inter prediction mode for the PU, the intra prediction mode for the PU, the size of the TU, and the shape of the TU. Alternatively, transform information indicating the transform method may be transmitted from the encoding device 100 to the decoding device 200 by signaling.

[0231] When the transform skip mode is used, the transform unit 130 may omit transforming the residual block.

[0232] By applying quantization to the transform coefficients, quantized transform coefficient levels or quantization levels may be generated. Hereinafter, in an embodiment, each of the quantized transform coefficient levels and the quantization levels may also be referred to as a 'transform coefficient'.

[0233] The quantization unit 140 may generate a quantized transform coefficient level (ie, a quantization level or a quantization coefficient) by quantizing the transform coefficient according to the quantization parameter. The quantization unit 140 may output the generated quantized transform coefficient level. In this case, the quantization unit 140 may quantize the transform coefficient using a quantization matrix.

[0234] The entropy encoding unit 150 may generate a bitstream by performing entropy encoding based on probability distribution based on the value calculated by the quantization unit 140 and / or the encoding parameter value calculated during the encoding process. The entropy encoding unit 150 may output the generated bitstream.

[0235] The entropy encoding unit 150 may perform entropy encoding on information about pixels of an image and information required for decoding the image. For example, the information required for decoding the image may include syntax elements and the like.

[0236] When entropy coding is applied, fewer bits can be allocated to symbols that appear more frequently, and more bits can be allocated to symbols that appear less frequently. Since the symbols are represented by this allocation, the size of the bit string of the target symbol to be encoded can be reduced. Therefore, the compression performance of video coding can be improved by entropy coding.

[0237] In addition, for entropy coding, the entropy coding unit 150 may use a coding method such as exponential Golomb, context adaptive variable length coding (CAVLC) or context adaptive binary arithmetic coding (CABAC). For example, the entropy coding unit 150 may use a variable length coding / code (VLC) table to perform entropy coding. For example, the entropy coding unit 150 may derive a binarization method for a target symbol. In addition, the entropy coding unit 150 may derive a probability model for a target symbol / binary bit. The entropy coding unit 150 may use the derived binarization method, probability model and context model to perform arithmetic coding.

[0238] The entropy encoding unit 150 may transform coefficients in a 2D block form into a 1D vector form through a transform coefficient scanning method in order to encode quantized transform coefficient levels.

[0239] The coding parameters may be information required for coding and / or decoding. The coding parameters may include information encoded by the coding device 100 and transmitted from the coding device 100 to the decoding device, and may also include information that can be derived during the coding or decoding process. For example, the information transmitted to the decoding device may include syntax elements.

[0240] The coding parameters may include not only information (or flags or indexes) encoded by the coding device and transmitted by the coding device to the decoding device using a signal, such as syntax elements, but also information derived in the coding or decoding process. In addition, the coding parameters may include information required to encode or decode the image. For example, the coding parameters may include at least one value, combination or statistics of the following items: the size of the unit / block, the shape / form of the unit / block, the depth of the unit / block, the partition information of the unit / block, the partition structure of the unit / block, information indicating whether the unit / block is partitioned in a quadtree structure, information indicating whether the unit / block is partitioned in a binary tree structure, the partition direction of the binary tree structure (horizontal or vertical), the partition form of the binary tree structure (symmetric partitioning or asymmetric partitioning), information indicating whether the unit / block is partitioned in a ternary tree structure, the partition direction of the ternary tree structure (horizontal or vertical), the partition form of the ternary tree structure (symmetric partitioning or asymmetric partitioning), etc.), information indicating whether the unit / block is partitioned in a multi-type tree structure, a combination and direction of partitions of the multi-type tree structure (horizontal direction or vertical direction, etc.), a partition form of the multi-type tree structure (symmetric partition or asymmetric partition, etc.), a partition tree in the form of a multi-type tree (binary tree or ternary tree), a prediction type (intra-frame prediction or inter-frame prediction), an intra-frame prediction mode / direction, an intra-frame luminance prediction mode / direction, an intra-frame chrominance prediction mode / direction, an intra-frame partition information, an inter-frame partition information, a coding block partition flag, a prediction block partition flag, a transform block partition flag, a reference sample filtering method, a reference sample filter tap, a reference sample filter coefficient, a prediction block filtering method, a prediction prediction block filter taps, prediction block filter coefficients, prediction block boundary filtering method, prediction block boundary filter taps, prediction block boundary filter coefficients, inter prediction mode, motion information, motion vector, motion vector difference, reference picture index, inter prediction direction, inter prediction indicator, prediction list utilization flag, reference picture list, reference image, POC, motion vector predictor, motion vector prediction index, motion vector prediction candidate, motion vector candidate list, information indicating whether to use merge mode, merge index, merge candidate, merge candidate list, information indicating whether to use skip mode, type of interpolation filter, taps of interpolation filter, filter of interpolation filter information indicating whether a deblocking filter is applied, coefficients of the in-loop filter, taps of the in-loop filter, shape / form of the in-loop filter, information indicating whether a deblocking filter is applied, coefficients of the deblocking filter,taps of a deblocking filter, strength of a deblocking filter, shape / form of a deblocking filter, information indicating whether an adaptive sample offset is applied, value of an adaptive sample offset, category of an adaptive sample offset, type of an adaptive sample offset, information indicating whether an adaptive in-loop filter is applied, coefficients of an adaptive in-loop filter, taps of an adaptive in-loop filter, shape / form of an adaptive in-loop filter, binarization / debinarization method, context model, context model determination method, context model update method, information indicating whether a normal mode is performed, information whether a bypass mode is performed, a valid coefficient flag, a last valid coefficient flag, a coding flag for a coefficient group, a position of a last valid coefficient, information indicating whether a coefficient value is greater than 1, information indicating whether a coefficient value is greater than 2, information indicating whether a coefficient value is greater than 3, residual coefficient value information, sign information, reconstructed luminance samples, reconstructed chrominance samples, context bits, bypass bits, residual Differential luminance samples, residual chrominance samples, transform coefficients, luminance transform coefficients, chrominance transform coefficients, quantization levels, luminance quantization levels, chrominance quantization levels, transform coefficient levels, transform coefficient level scanning methods, the size of the motion vector search area on the decoding device side, the shape / form of the motion vector search area on the decoding device side, the number of motion vector searches on the decoding device side, the size of the CTU, the minimum block size, the maximum block size, the maximum block depth, the minimum block depth, the image display / output order, the stripe identification information, the stripe type, the stripe partition information, the parallel block group identification information, the parallel block group type, the parallel block group partition information, the parallel block identification information, the parallel block type, the parallel block partition information, the picture type, the bit depth, the input sample bit depth, the reconstruction sample bit depth, the residual sample bit depth, the transform coefficient bit depth, the quantization level bit depth, the information about the luminance signal, the information about the chrominance signal, the color space of the target block and the color space of the residual block. In addition, the above-mentioned coding parameter related information may also be included in the coding parameters. Information used to calculate and / or derive the above-mentioned coding parameters may also be included in the coding parameters. Information calculated or derived using the above encoding parameters may also be included in the encoding parameters.

[0241] The first transform selection information may indicate a first transform applied to the target block.

[0242] The secondary transform selection information may indicate a secondary transform applied to the target block.

[0243] The residual signal may represent the difference between the original signal and the predicted signal. Alternatively, the residual signal may be a signal generated by transforming the difference between the original signal and the predicted signal. Alternatively, the residual signal may be a signal generated by transforming and quantizing the difference between the original signal and the predicted signal. The residual block may be the residual signal of the block.

[0244] Here, signaling information may mean that the encoding apparatus 100 includes entropy encoding information generated by performing entropy encoding on a flag or an index in a bitstream, and the decoding apparatus 200 obtains information by performing entropy decoding on the entropy encoding information extracted from the bitstream. Here, the information may include a flag, an index, etc.

[0245] A signal may mean information to be transmitted using a signal. Hereinafter, information for an image and a block may be referred to as a signal. In addition, hereinafter, the terms "information" and "signal" may be used to have the same meaning and may be used interchangeably with each other. For example, a specific signal may be a signal representing a specific block. An original signal may be a signal representing a target block. A prediction signal may be a signal representing a prediction block. A residual signal may be a signal representing a residual block.

[0246] The bitstream may include information based on a specific syntax. The encoding apparatus 100 may generate a bitstream including the information according to the specific syntax. The decoding apparatus 200 may acquire information from the bitstream according to the specific syntax.

[0247] Since the encoding apparatus 100 performs encoding via inter-frame prediction, the encoded target image can be used as a reference image of another (one or more) images to be processed subsequently. Therefore, the encoding apparatus 100 may reconstruct or decode the encoded target image and store the reconstructed or decoded image as a reference image in the reference picture buffer 190. For decoding, inverse quantization and inverse transformation of the encoded target image may be processed.

[0248] The quantization level may be inversely quantized by the inverse quantization unit 160, and may be inversely transformed by the inverse transform unit 170. The inverse quantization unit 160 may generate an inversely quantized coefficient by performing inverse quantization on the quantization level. The inverse transform unit 170 may generate an inversely quantized and inversely transformed coefficient by performing inverse transformation on the inversely quantized coefficient.

[0249] The inverse quantized and inverse transformed coefficients may be added to the prediction block by the adder 175. The inverse quantized and inverse transformed coefficients are added to the prediction block, and then a reconstructed block may be generated. Here, the inverse quantized and / or inverse transformed coefficients may mean coefficients on which one or more of inverse quantization and inverse transformation are performed, and may also mean a reconstructed residual block. Here, the reconstructed block may mean a restored block or a decoded block.

[0250] The reconstructed block may be filtered by the filter unit 180. The filter unit 180 may apply one or more of a deblocking filter, a sample adaptive offset (SAO) filter, an adaptive loop filter (ALF), and a non-local filter (NLF) to the reconstructed samples, the reconstructed block, or the reconstructed picture. The filter unit 180 may also be referred to as an "in-loop filter".

[0251] The deblocking filter can eliminate block distortion that occurs at the boundary between blocks in the reconstructed picture. In order to determine whether to apply the deblocking filter, the number of rows or columns included in the block and including (one or more) pixels for the following operation can be determined: whether to apply the deblocking filter to the target block is determined based on the (one or more) pixels.

[0252] When a deblocking filter is applied to a target block, the filter applied may be different according to the required strength of the deblocking filter. In other words, among different filters, a filter determined by considering the strength of the deblocking filter may be applied to the target block. When a deblocking filter is applied to a target block, one or more filters among a long tap filter, a strong filter, a weak filter, and a Gaussian filter may be applied to the target block according to the required strength of the deblocking filter.

[0253] In addition, when vertical filtering and horizontal filtering are performed on the target block, the horizontal filtering and the vertical filtering may be processed in parallel.

[0254] SAO may add a suitable offset to the value of a pixel to compensate for a coding error. SAO may perform correction of an offset using a difference between an original image and an image to which deblocking is applied on a pixel basis for an image to which deblocking is applied. In order to perform offset correction on an image, a method for dividing pixels included in an image into a certain number of regions, determining a region to which an offset is to be applied among the divided regions, and applying the offset to the determined region may be used, and a method for applying an offset in consideration of edge information of each pixel may also be used.

[0255] The ALF may perform filtering based on a value obtained by comparing the reconstructed image with the original image. After the pixels included in the image have been divided into a predetermined number of groups, the filter to be applied to each group may be determined, and filtering may be performed differently for each group. Information related to whether an adaptive loop filter is applied may be transmitted with a signal for each CU. Such information may be transmitted with a signal for a luminance signal. The shape and filter coefficients of the ALF to be applied to each block may be different for each block. Alternatively, an ALF having a fixed form may be applied to the block regardless of the characteristics of the block.

[0256] The non-local filter may perform filtering based on a reconstructed block similar to the target block. An area similar to the target block may be selected from the reconstructed picture, and the statistical characteristics of the selected similar area may be used to perform filtering of the target block. Information on whether to apply the non-local filter may be transmitted with a signal for a coding unit (CU). In addition, the shape and filter coefficients of the non-local filter to be applied to the block may be different according to the block.

[0257] The reconstructed block or the reconstructed image filtered by the filter unit 180 may be stored as a reference picture in the reference picture buffer 190. The reconstructed block filtered by the filter unit 180 may be a part of the reference picture. In other words, the reference picture may be a reconstructed picture composed of the reconstructed blocks filtered by the filter unit 180. The stored reference picture may be subsequently used for inter-frame prediction or motion compensation.

[0258] Figure 2 is a block diagram showing a configuration of an embodiment of a decoding device to which the present disclosure is applied.

[0259] The decoding device 200 may be a decoder, a video decoding device, or an image decoding device.

[0260] Reference Figure 2 , the decoding device 200 may include an entropy decoding unit 210, an inverse quantization (dequantization) unit 220, an inverse transform unit 230, an intra-frame prediction unit 240, an inter-frame prediction unit 250, a switch 245, an adder 255, a filter unit 260 and a reference picture buffer 270.

[0261] The decoding apparatus 200 may receive a bitstream output from the encoding apparatus 100. The decoding apparatus 200 may receive a bitstream stored in a computer-readable storage medium, and may receive a bitstream streamed through a wired / wireless transmission medium.

[0262] The decoding apparatus 200 may perform decoding on a bitstream in an intra mode and / or an inter mode. In addition, the decoding apparatus 200 may generate a reconstructed image or a decoded image through decoding, and may output the reconstructed image or the decoded image.

[0263] For example, switching to the intra mode or the inter mode based on the prediction mode for decoding may be performed by the switch 245. When the prediction mode for decoding is the intra mode, the switch 245 may be operated to switch to the intra mode. When the prediction mode for decoding is the inter mode, the switch 245 may be operated to switch to the inter mode.

[0264] The decoding apparatus 200 may obtain a reconstructed residual block by decoding an input bit stream, and may generate a prediction block. When the reconstructed residual block and the prediction block are obtained, the decoding apparatus 200 may generate a reconstructed block as a target to be decoded by adding the reconstructed residual block and the prediction block.

[0265] The entropy decoding unit 210 may generate symbols by performing entropy decoding on the bitstream based on the probability distribution of the bitstream. The generated symbols may include symbols in the form of quantized transform coefficient levels (i.e., quantization levels or quantization coefficients). Here, the entropy decoding method may be similar to the above-mentioned entropy encoding method. That is, the entropy decoding method may be an inverse process of the above-mentioned entropy encoding method.

[0266] The entropy decoding unit 210 may change a coefficient having a one-dimensional (1D) vector form into a 2D block shape through a transform coefficient scanning method in order to decode quantized transform coefficient levels.

[0267] For example, by scanning the block coefficients using an upper right diagonal scan, the coefficients of the block can be changed into a 2D block shape. Optionally, which of the upper right diagonal scan, vertical scan, and horizontal scan to use can be determined according to the size of the corresponding block and / or the intra prediction mode.

[0268] The quantized coefficients may be inversely quantized by the inverse quantization unit 220. The inverse quantization unit 220 may generate an inversely quantized coefficient by performing inverse quantization on the quantized coefficients. In addition, the inversely quantized coefficients may be inversely transformed by the inverse transform unit 230. The inverse transform unit 230 may generate a reconstructed residual block by performing inverse transformation on the inversely quantized coefficients. As a result of performing inverse quantization and inverse transformation on the quantized coefficients, a reconstructed residual block may be generated. Here, the inverse quantization unit 220 may apply a quantization matrix to the quantized coefficients when generating the reconstructed residual block.

[0269] When the intra mode is used, the intra prediction unit 240 may generate a predicted block by performing spatial prediction using pixel values ​​of a previously decoded neighboring block adjacent to the target block with respect to the target block.

[0270] The inter prediction unit 250 may include a motion compensation unit. Alternatively, the inter prediction unit 250 may be designated as a "motion compensation unit."

[0271] When the inter mode is used, the motion compensation unit may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference picture buffer 270 with respect to the target block.

[0272] The motion compensation unit may apply an interpolation filter to a partial area of ​​a reference image when a motion vector has a value other than an integer, and may generate a prediction block using the reference image to which the interpolation filter is applied. In order to perform motion compensation, the motion compensation unit may determine which of a skip mode, a merge mode, an advanced motion vector prediction (AMVP) mode, and a current picture reference mode corresponds to a motion compensation method for a PU included in the CU based on the CU, and may perform motion compensation according to the determined mode.

[0273] The reconstructed residual block and the prediction block may be added to each other by the adder 255. The adder 255 may generate a reconstructed block by adding the reconstructed residual block to the prediction block.

[0274] The reconstructed block may be filtered by the filter unit 260. The filter unit 260 may apply at least one of a deblocking filter, an SAO filter, an ALF, and an NLF to the reconstructed block or the reconstructed image. The reconstructed image may be a picture including the reconstructed block.

[0275] The filter unit may output a reconstructed image.

[0276] The reconstructed image and / or the reconstructed block filtered by the filter unit 260 may be stored as a reference picture in the reference picture buffer 270. The reconstructed block filtered by the filter unit 260 may be a part of the reference picture. In other words, the reference picture may be an image composed of the reconstructed blocks filtered by the filter unit 260. The stored reference picture may be subsequently used for inter-frame prediction or motion compensation.

[0277] Figure 3 is a diagram schematically showing a partition structure of an image when the image is encoded and decoded.

[0278] Figure 3 An example where a single unit is partitioned into a plurality of sub-units may be schematically shown.

[0279] In order to efficiently partition an image, a coding unit (CU) may be used in encoding and decoding. The term "unit" may be used to collectively specify 1) a block including image samples and 2) a syntax element. For example, "partition of a unit" may mean "partition of a block corresponding to a unit".

[0280] CU can be used as a basic unit for image encoding / decoding. CU can be used as a unit to which one mode selected from intra mode and inter mode is applied in image encoding / decoding. In other words, in image encoding / decoding, it can be determined which one of the intra mode and the inter mode is applied to each CU.

[0281] Also, a CU may be a basic unit in prediction, transformation, quantization, inverse transformation, inverse quantization, and encoding / decoding of a transform coefficient.

[0282] Reference Figure 3 , the image 300 may be sequentially partitioned into units corresponding to a maximum coding unit (LCU), and a partition structure may be determined for each LCU. Here, LCU may be used to have the same meaning as a coding tree unit (CTU).

[0283] The partition of a unit may mean the partition of a block corresponding to the unit. The block partition information may include depth information about the depth of the unit. The depth information may indicate the number of times the unit is partitioned and / or the degree to which the unit is partitioned. A single unit may be hierarchically partitioned into a plurality of sub-units with depth information based on a tree structure.

[0284] Each of the sub-units of the partition may have depth information. The depth information may be information indicating the size of the CU. The depth information may be stored for each CU.

[0285] Each CU may have depth information. When a CU is partitioned, a CU generated by partitioning may have a depth increased by 1 from the depth of the partitioned CU.

[0286] The partition structure may mean the distribution of coding units (CUs) for efficiently encoding an image in the LCU 310. Such distribution may be determined according to whether a single CU is to be partitioned into a plurality of CUs. The number of CUs generated by partitioning may be a positive integer of 2 or more, including 2, 3, 4, 8, 16, etc.

[0287] According to the number of CUs generated by partitioning, the horizontal size and vertical size of each of the CUs generated by partitioning may be smaller than the horizontal size and vertical size of the CU before partitioning. For example, the horizontal size and vertical size of each of the CUs generated by partitioning may be half of the horizontal size and vertical size of the CU before partitioning.

[0288] The CU of each partition may be recursively partitioned into four CUs in the same manner. Through recursive partitioning, at least one of the horizontal size and the vertical size of the CU of each partition may be reduced compared to at least one of the horizontal size and the vertical size of the CU before partitioning.

[0289] Partitioning of the CU may be performed recursively up to a predefined depth or a predefined size.

[0290] For example, the depth of the CU may have a value ranging from 0 to 3. According to the depth of the CU, the size of the CU may range from a size of 64×64 to a size of 8×8.

[0291] For example, the depth of the LCU 310 may be 0, and the depth of the minimum coding unit (SCU) may be a predefined maximum depth. Here, as described above, the LCU may be a CU having a maximum coding unit size, and the SCU may be a CU having a minimum coding unit size.

[0292] Partitioning may start from the LCU 310, and the depth of the CU may increase by one whenever the horizontal and / or vertical size of the CU is reduced by partitioning.

[0293] For example, for each depth, a non-partitioned CU may have a size of 2N×2N. In addition, in the case where the CU is partitioned, a CU of size 2N×2N may be partitioned into four CUs, each of which has a size of N×N. Whenever the depth increases by 1, the value of N may be halved.

[0294] Reference Figure 3 , an LCU with a depth of 0 may have 64×64 pixels or 64×64 blocks. 0 may be the minimum depth. An SCU with a depth of 3 may have 8×8 pixels or 8×8 blocks. 3 may be the maximum depth. Here, a CU with 64×64 blocks as an LCU may be represented by a depth of 0. A CU with 32×32 blocks may be represented by a depth of 1. A CU with 16×16 blocks may be represented by a depth of 2. A CU with 8×8 blocks as an SCU may be represented by a depth of 3.

[0295] Information about whether the corresponding CU is partitioned may be represented by partition information of the CU. The partition information may be 1-bit information. All CUs except the SCU may include partition information. For example, the value of the partition information of a non-partitioned CU may be a first value. The value of the partition information of a partitioned CU may be a second value. When the partition information indicates whether the CU is partitioned, the first value may be "0" and the second value may be "1".

[0296] For example, when a single CU is partitioned into four CUs, the horizontal size and vertical size of each of the four CUs generated by partitioning may be half the horizontal size and vertical size of the CU before partitioning. When a CU having a size of 32×32 is partitioned into four CUs, the size of each of the four partitioned CUs may be 16×16. When a single CU is partitioned into four CUs, it may be considered that the CU has been partitioned in a quadtree structure. In other words, it may be considered that quadtree partitioning has been applied to the CU.

[0297] For example, when a single CU is partitioned into two CUs, the horizontal size or vertical size of each of the two CUs generated by partitioning may be half the horizontal size or vertical size of the CU before partitioning. When a CU with a size of 32×32 is partitioned vertically into two CUs, the size of each of the two CUs after partitioning may be 16×32. When a CU with a size of 32×32 is partitioned horizontally into two CUs, the size of each of the two CUs after partitioning may be 32×16. When a single CU is partitioned into two CUs, it can be considered that the CU has been partitioned in a binary tree structure. In other words, it can be considered that binary tree partitioning has been applied to the CU.

[0298] For example, when a single CU is partitioned (or split) into three CUs, the original CU before partitioning is partitioned so that its horizontal size or vertical size is divided at a ratio of 1:2:1, thereby enabling the generation of three sub-CUs. For example, when a CU with a size of 16×32 is partitioned horizontally into three sub-CUs, the three sub-CUs generated by the partitioning may have sizes of 16×8, 16×16, and 16×8, respectively, in the direction from top to bottom. For example, when a CU with a size of 32×32 is partitioned vertically into three sub-CUs, the three sub-CUs generated by the partitioning may have sizes of 8×32, 16×32, and 8×32, respectively, in the direction from left to right. When a single CU is partitioned into three CUs, the CU may be considered to be partitioned in a ternary tree form. In other words, it may be considered that ternary tree partitioning has been applied to the CU.

[0299] Both quadtree partitioning and binary tree partitioning are applied to Figure 3 LCU 310.

[0300] In the encoding apparatus 100, a coding tree unit (CTU) having a size of 64×64 may be partitioned into a plurality of smaller CUs by a recursive quadtree structure. A single CU may be partitioned into four CUs having the same size. Each CU may be recursively partitioned and may have a quadtree structure.

[0301] Through recursive partitioning of CUs, the best partitioning method that results in the minimum rate-distortion penalty can be selected.

[0302] Figure 3 The coding tree unit (CTU) 320 in FIG. 1 is an example of a total CTU to which quadtree partitioning, binary tree partitioning, and ternary tree partitioning are applied.

[0303] As described above, in order to partition a CTU, at least one of quadtree partitioning, binary tree partitioning, and ternary tree partitioning may be applied to the CTU. The partitioning may be applied based on a specific priority.

[0304] For example, quadtree partitioning may be preferentially applied to CTUs. A CU that cannot be further partitioned in the form of a quadtree may correspond to a leaf node of a quadtree. A CU corresponding to a leaf node of a quadtree may be a root node of a binary tree and / or a ternary tree. That is, a CU corresponding to a leaf node of a quadtree may be partitioned in the form of a binary tree or a ternary tree, or may not be further partitioned. In this case, each CU generated by applying a binary tree partitioning or a ternary tree partitioning to a CU corresponding to a leaf node of a quadtree is prevented from being subjected to quadtree partitioning again, thereby effectively performing partitioning of a block and / or signaling of block partition information.

[0305] The four partition information may be used to signal the partition of the CU corresponding to each node of the quadtree. The four partition information having a first value (e.g., "1") may indicate that the corresponding CU is partitioned in a quadtree form. The four partition information having a second value (e.g., "0") may indicate that the corresponding CU is not partitioned in a quadtree form. The four partition information may be a flag having a specific length (e.g., 1 bit).

[0306] There may be no priority between binary tree partitioning and ternary tree partitioning. That is, the CU corresponding to the leaf node of the quadtree may be partitioned in a binary tree form or a ternary tree form. In addition, the CU generated by binary tree partitioning or ternary tree partitioning may be further partitioned in a binary tree form or a ternary tree form, or may not be further partitioned.

[0307] Partitioning performed when there is no priority between binary tree partitioning and ternary tree partitioning may be referred to as "multi-type tree partitioning". That is, the CU corresponding to the leaf node of the quadtree may be the root node of the multi-type tree. The partition of the CU corresponding to each node of the multi-type tree may be signaled using at least one of information indicating whether the CU is partitioned in a multi-type tree, partition direction information, and partition tree information. For the partition of the CU corresponding to each node of the multi-type tree, information indicating whether partitioning in a multi-type tree is performed, partition direction information, and partition tree information may be sequentially signaled.

[0308] For example, information indicating whether a CU is partitioned in a multi-type tree and having a first value (e.g., "1") may indicate that the corresponding CU is partitioned in a multi-type tree. Information indicating whether a CU is partitioned in a multi-type tree and having a second value (e.g., "0") may indicate that the corresponding CU is not partitioned in a multi-type tree.

[0309] When a CU corresponding to each node of the multi-type tree is partitioned in the multi-type tree form, the corresponding CU may further include partition direction information.

[0310] The partition direction information may indicate the partition direction of the multi-type tree partition. The partition direction information having a first value (e.g., "1") may indicate that the corresponding CU is partitioned in the vertical direction. The partition direction information having a second value (e.g., "0") may indicate that the corresponding CU is partitioned in the horizontal direction.

[0311] When a CU corresponding to each node of a multi-type tree is partitioned in a multi-type tree form, the corresponding CU may further include partition tree information. The partition tree information may indicate a tree used for multi-type tree partitioning.

[0312] For example, partition tree information having a first value (eg, "1") may indicate that the corresponding CU is partitioned in a binary tree form. Partition tree information having a second value (eg, "0") may indicate that the corresponding CU is partitioned in a ternary tree form.

[0313] Here, each of the above-mentioned information indicating whether partitioning with a multi-type tree is performed, the partition tree information, and the partition direction information may be a flag having a specific length (eg, 1 bit).

[0314] At least one of the above-mentioned four partition information, the information indicating whether to perform partitioning with a multi-type tree, the partition direction information, and the partition tree information may be entropy encoded and / or entropy decoded. In order to perform entropy encoding / decoding of such information, information of a neighboring CU adjacent to the target CU may be used.

[0315] For example, it can be considered that the partition form (i.e., partition / non-partition, partition tree and / or partition direction) of the left CU and / or the upper CU and the partition form of the target CU will be similar to each other with a high probability. Therefore, based on the information of the neighboring CU, context information for entropy encoding and / or entropy decoding of the information of the target CU can be derived. Here, the information of the neighboring CU may include at least one of the following items: 1) four partition information of the neighboring CU, 2) information indicating whether the neighboring CU is partitioned in a multi-type tree, 3) partition direction information of the neighboring CU, and 4) partition tree information of the neighboring CU.

[0316] In another embodiment, among the binary tree partitioning and the ternary tree partitioning, the binary tree partitioning may be performed preferentially. That is, the binary tree partitioning may be applied first, and then the CU corresponding to the leaf node of the binary tree may be set as the root node of the ternary tree. In this case, the quadtree partitioning or the binary tree partitioning may not be performed on the CU corresponding to the node of the ternary tree.

[0317] A CU that is no longer further partitioned by quadtree partitioning, binary tree partitioning, and / or ternary tree partitioning may be a unit for coding, prediction, and / or transformation. That is, the CU may not be further partitioned for prediction and / or transformation. Therefore, a partition structure for partitioning a CU into a prediction unit (PU) and / or a transformation unit (TU), its partition information, and the like may not be present in the bitstream.

[0318] However, when the size of the CU as a unit of partition is larger than the size of the maximum transform block, the CU may be recursively partitioned until the size of the CU becomes smaller than or equal to the size of the maximum transform block. For example, when the size of the CU is 64×64 and the size of the maximum transform block is 32×32, the CU may be partitioned into four 32×32 blocks in order to perform transform. For example, when the size of the CU is 32×64 and the size of the maximum transform block is 32×32, the CU may be partitioned into two 32×32 blocks.

[0319] In this case, information indicating whether the CU is partitioned for transformation may not be separately signaled. Without signaling, whether the CU is partitioned may be determined via a comparison between the horizontal size (and / or vertical size) of the CU and the horizontal size (and / or vertical size) of the largest transform block. For example, when the horizontal size of the CU is larger than the horizontal size of the largest transform block, the CU may be bisected vertically. In addition, when the vertical size of the CU is larger than the vertical size of the largest transform block, the CU may be bisected horizontally.

[0320] Information about the maximum size and / or minimum size of the CU and information about the maximum size and / or minimum size of the transform block may be signaled or determined at a higher level than the CU level. For example, the higher level may be a sequence level, a picture level, a tile level, a tile group level, or a slice level. For example, the minimum size of the CU may be set to 4×4. For example, the maximum size of the transform block may be set to 64×64. For example, the maximum size of the transform block may be set to 4×4.

[0321] Information about the minimum size of the CU corresponding to the leaf node of the quadtree (i.e., the minimum size of the quadtree) and / or information about the maximum depth of the path from the root node of the multi-type tree to the leaf node (i.e., the maximum depth of the multi-type tree) may be signaled or determined at a higher level than the level of the CU corresponding to the leaf node of the quadtree. For example, the higher level may be a sequence level, a picture level, a slice level, a tile group level, or a tile level. Information about the minimum size of the quadtree and / or information about the maximum depth of the multi-type tree may be signaled or determined separately at each level of the intra-slice level and the inter-slice level.

[0322] Information about the difference between the size of the CTU and the maximum size of the transform block may be signaled or determined at a higher level than the level of the CU. For example, the higher level may be a sequence level, a picture level, a slice level, a parallel block group level, or a parallel block level. Information about the maximum size of the CU corresponding to each node of the binary tree (i.e., the maximum size of the binary tree) may be determined based on the size and difference information of the CTU. The maximum size of the CU corresponding to each node of the ternary tree (i.e., the maximum size of the ternary tree) may have different values ​​depending on the type of the slice. For example, the maximum size of the ternary tree at the intra-slice level may be 32×32. For example, the maximum size of the ternary tree at the inter-slice level may be 128×128. For example, the minimum size of the CU corresponding to each node of the binary tree (i.e., the minimum size of the binary tree) and / or the minimum size of the CU corresponding to each node of the ternary tree (i.e., the minimum size of the ternary tree) may be set to the minimum size of the CU.

[0323] In another example, the maximum size of the binary tree and / or the maximum size of the ternary tree may be signaled or determined at the slice level. In addition, the minimum size of the binary tree and / or the minimum size of the ternary tree may be signaled or determined at the slice level.

[0324] Based on the above-mentioned various block sizes and depths, quad partition information, information indicating whether partitioning with a multi-type tree is performed, partition tree information, and / or partition direction information may or may not exist in a bitstream.

[0325] For example, when the size of the CU is not greater than the minimum size of the quadtree, the CU may not include quad partition information, and the quad partition information of the CU may be inferred as a second value.

[0326] For example, when the size (horizontal size and vertical size) of the CU corresponding to each node of the multi-type tree is greater than the maximum size (horizontal size and vertical size) of the binary tree and / or the maximum size (horizontal size and vertical size) of the ternary tree, the CU may not be partitioned in a binary tree form and / or a ternary tree form. With this determination, information indicating whether partitioning in a multi-type tree is performed may not be signaled but may be inferred as a second value.

[0327] Optionally, when the size (horizontal size and vertical size) of the CU corresponding to each node of the multi-type tree is equal to the minimum size (horizontal size and vertical size) of the binary tree, or when the size (horizontal size and vertical size) of the CU is equal to twice the minimum size (horizontal size and vertical size) of the ternary tree, the CU may not be partitioned in a binary tree form and / or a ternary tree form. With this determination method, information indicating whether partitioning in a multi-type tree is performed may not be transmitted by a signal, but may be inferred as a second value. The reason is that when the CU is partitioned in a binary tree form and / or a ternary tree form, a CU smaller than the minimum size of the binary tree and / or the minimum size of the ternary tree is generated.

[0328] Optionally, binary tree partitioning or ternary tree partitioning may be limited based on the size of a virtual pipeline data unit (ie, the size of a pipeline buffer). For example, when a CU is partitioned into sub-CUs that are not suitable for the size of a pipeline buffer by binary tree partitioning or ternary tree partitioning, binary tree partitioning or ternary tree partitioning may be limited. The size of the pipeline buffer may be equal to the maximum size of a transform block (eg, 64×64).

[0329] For example, when the size of the pipeline buffer is 64×64, the following partitions may be limited.

[0330] -Ternary tree partitioning of N×M CUs (where N and / or M is 128)

[0331] - 128×N CU horizontal binary tree partitioning (where N<=64)

[0332] -N×128 CU vertical binary tree partition (where N<=64)

[0333] Optionally, when the depth of the CU corresponding to each node of the multi-type tree is equal to the maximum depth of the multi-type tree, the CU may not be partitioned in a binary tree form and / or a ternary tree form. With this determination, information indicating whether partitioning in a multi-type tree is performed may not be transmitted by a signal, but may be inferred as a second value.

[0334] Alternatively, information indicating whether partitioning in a multi-type tree is performed may be transmitted by signal only when at least one of vertical binary tree partitioning, horizontal binary tree partitioning, vertical ternary tree partitioning, and horizontal ternary tree partitioning is possible for a CU corresponding to each node of a multi-type tree. Otherwise, the CU may not be partitioned in a binary tree form and / or a ternary tree form. With this determination, information indicating whether partitioning in a multi-type tree is performed may not be transmitted by signal, but may be inferred as a second value.

[0335] Optionally, for the CU corresponding to each node of the multi-type tree, partition direction information may be transmitted with a signal only when both vertical binary tree partitioning and horizontal binary tree partitioning are possible or only when both vertical ternary tree partitioning and horizontal ternary tree partitioning are possible. Otherwise, the partition direction information may not be transmitted with a signal, but may be inferred as a value indicating the direction in which the CU may be partitioned.

[0336] Optionally, for the CU corresponding to each node of the multi-type tree, partition tree information may be signaled only when both vertical binary tree partitioning and vertical ternary tree partitioning are possible or only when both horizontal binary tree partitioning and horizontal ternary tree partitioning are possible. Otherwise, the partition tree information may not be signaled but may be inferred as a value indicating a tree of partitions applicable to the CU.

[0337] Figure 4 is a diagram illustrating a form of prediction units that a coding unit may include.

[0338] When a CU that is not further partitioned among CUs partitioned from an LCU can be divided into one or more prediction units (PUs), such division is also called 'partitioning'.

[0339] PU can be a basic unit for prediction. PU can be encoded and decoded in any one of skip mode, inter mode and intra mode. PU can be partitioned into various shapes according to each mode. For example, Figure 1 The target block described and the above reference Figure 2 The described target blocks may each be a PU.

[0340] A CU may not be partitioned into PUs. When a CU is not partitioned into PUs, the size of the CU and the size of the PU may be equal to each other.

[0341] In skip mode, partitions may not exist in a CU. In skip mode, a 2N×2N mode 410 may be supported without partitions, wherein in the 2N×2N mode 410, the sizes of the PU and the CU are the same as each other.

[0342] In inter mode, there may be eight types of partition shapes in a CU. For example, in inter mode, 2N×2N mode 410, 2N×N mode 415, N×2N mode 420, N×N mode 425, 2N×nU mode 430, 2N×nD mode 435, nL×2N mode 440, and nR×2N mode 445 may be supported.

[0343] In intra mode, 2N×2N mode 410 and N×N mode 425 may be supported.

[0344] In 2N×2N mode 410, a PU having a 2N×2N size may be encoded. A PU having a 2N×2N size may mean a PU having the same size as that of a CU. For example, a PU having a 2N×2N size may have a size of 64×64, 32×32, 16×16, or 8×8.

[0345] In N×N mode 425 , a PU having an N×N size may be encoded.

[0346] For example, in intra prediction, when the size of the PU is 8×8, the PUs of four partitions may be encoded. The size of the PU of each partition may be 4×4.

[0347] When a PU is encoded in intra mode, any one of multiple intra prediction modes may be used to encode the PU. For example, HEVC technology may provide 35 intra prediction modes, and a PU may be encoded in any one of the 35 intra prediction modes.

[0348] Which of the 2Nx2N mode 410 and the NxN mode 425 is to be used to encode the PU may be determined based on the rate-distortion cost.

[0349] The encoding device 100 may perform an encoding operation on a PU of size 2N×2N. Here, the encoding operation may be an operation of encoding the PU according to each of a plurality of intra prediction modes that may be used by the encoding device 100. Through the encoding operation, an optimal intra prediction mode for a PU of size 2N×2N may be derived. The optimal intra prediction mode may be an intra prediction mode that incurs a minimum rate distortion cost when encoding a PU of size 2N×2N among a plurality of intra prediction modes that may be used by the encoding device 100.

[0350] In addition, the encoding device 100 may sequentially perform encoding operations on each PU obtained from the N×N partition. Here, the encoding operation may be an operation of encoding the PU according to each of a plurality of intra prediction modes that can be used by the encoding device 100. Through the encoding operation, an optimal intra prediction mode for a PU of size N×N may be derived. The optimal intra prediction mode may be an intra prediction mode that incurs a minimum rate distortion cost when encoding a PU of size N×N among a plurality of intra prediction modes that can be used by the encoding device 100.

[0351] The encoding apparatus 100 may determine which one of a PU of size 2N×2N and a PU of size N×N to be encoded based on a comparison of a rate-distortion cost of a PU of size 2N×2N and a rate-distortion cost of a PU of size N×N.

[0352] A single CU may be partitioned into one or more PUs, and a PU may be partitioned into multiple PUs.

[0353] For example, when a single PU is partitioned into four PUs, the horizontal size and vertical size of each of the four PUs generated by partitioning may be half the horizontal size and vertical size of the PU before partitioning. When a PU of size 32×32 is partitioned into four PUs, the size of each of the four partitioned PUs may be 16×16. When a single PU is partitioned into four PUs, it may be considered that the PU has been partitioned in a quadtree structure.

[0354] For example, when a single PU is partitioned into two PUs, the horizontal size or vertical size of each of the two PUs generated by partitioning may be half the horizontal size or vertical size of the PU before partitioning. When a PU of size 32×32 is partitioned vertically into two PUs, the size of each of the two partitioned PUs may be 16×32. When a PU of size 32×32 is partitioned horizontally into two PUs, the size of each of the two partitioned PUs may be 32×16. When a single PU is partitioned into two PUs, it may be considered that the PU has been partitioned in a binary tree structure.

[0355] Figure 5 is a diagram illustrating a form of a transformation unit that may be included in a coding unit.

[0356] A transform unit (TU) may have a basic unit for processes such as transformation, quantization, inverse transformation, inverse quantization, entropy encoding, and entropy decoding in a CU.

[0357] A TU may have a square shape or a rectangular shape. The shape of a TU may be determined based on the size and / or shape of a CU.

[0358] In a CU partitioned from an LCU, a CU that is not further partitioned into a CU may be partitioned into one or more TUs. Here, the partition structure of the TU may be a quadtree structure. For example, Figure 5 As shown, a single CU 510 can be partitioned once or multiple times according to a quadtree structure. With this partitioning, a single CU 510 can be composed of TUs of various sizes.

[0359] It can be considered that when a single CU is partitioned two or more times, the CU is recursively partitioned. Through partitioning, a single CU can be composed of transform units (TUs) of various sizes.

[0360] Alternatively, a single CU may be partitioned into one or more TUs based on the number of vertical and / or horizontal lines that partition the CU.

[0361] The CU may be partitioned into symmetric TUs or asymmetric TUs. In order to partition into asymmetric TUs, information about the size and / or shape of each TU may be transmitted from the encoding device 100 to the decoding device 200 using a signal. Alternatively, the size and / or shape of each TU may be derived from information about the size and / or shape of the CU.

[0362] A CU may not be partitioned into TUs. When a CU is not partitioned into TUs, the size of the CU and the size of the TU may be equal to each other.

[0363] A single CU may be partitioned into one or more TUs, and a TU may be partitioned into multiple TUs.

[0364] For example, when a single TU is partitioned into four TUs, the horizontal size and vertical size of each of the four TUs generated by partitioning may be half the horizontal size and vertical size of the TU before partitioning. When a TU of size 32×32 is partitioned into four TUs, the size of each of the four partitioned TUs may be 16×16. When a single TU is partitioned into four TUs, the TU may be considered to have been partitioned in a quadtree structure.

[0365] For example, when a single TU is partitioned into two TUs, the horizontal size or vertical size of each of the two TUs generated by partitioning may be half the horizontal size or vertical size of the TU before partitioning. When a TU of size 32×32 is partitioned vertically into two TUs, the size of each of the two partitioned TUs may be 16×32. When a TU of size 32×32 is partitioned horizontally into two TUs, the size of each of the two partitioned TUs may be 32×16. When a single TU is partitioned into two TUs, the TU may be considered to have been partitioned in a binary tree structure.

[0366] Can be different from Figure 5The CU is partitioned in the manner shown.

[0367] For example, a single CU may be partitioned into three CUs. The horizontal sizes or vertical sizes of the three CUs generated by the partitioning may be 1 / 4, 1 / 2, and 1 / 4 of the horizontal size or vertical size of the original CU before the partitioning, respectively.

[0368] For example, when a CU of size 32×32 is vertically partitioned into three CUs, the sizes of the three CUs generated from the partitioning may be 8×32, 16×32, and 8×32, respectively. In this way, when a single CU is partitioned into three CUs, it may be considered that the CU is partitioned in the form of a ternary tree.

[0369] One of the exemplary partitioning forms (i.e., quadtree partitioning, binary tree partitioning, and ternary tree partitioning) may be applied to the partitioning of the CU, and multiple partitioning schemes may be combined and used together for the partitioning of the CU. Here, the case where multiple partitioning schemes are combined and used together may be referred to as "complex tree format partitioning".

[0370] Figure 6 The segmentation of blocks according to an example is shown.

[0371] In the video encoding and / or decoding process, the target block may be segmented, such as Figure 6 For example, the target block may be a CU.

[0372] For the partitioning of the target block, an indicator indicating the partitioning information may be signaled from the encoding apparatus 100 to the decoding apparatus 200. The partitioning information may be information indicating how the target block is partitioned.

[0373] The split information may be one or more of a split flag (hereinafter referred to as "split_flag"), a quad flag (hereinafter referred to as "QB_flag"), a quadtree flag (hereinafter referred to as "quadtree_flag"), a binary tree flag (hereinafter referred to as "binarytree_flag") and a binary type flag (hereinafter referred to as "Btype_flag").

[0374] "split_flag" may be a flag indicating whether a block is split. For example, a split_flag value of 1 may indicate that the corresponding block is split. A split_flag value of 0 may indicate that the corresponding block is not split.

[0375] "QB_flag" may be a flag indicating which of the quadtree form and the binary tree form corresponds to the shape in which the block is partitioned. For example, a QB_flag value of 0 may indicate that the block is partitioned in a quadtree form. A QB_flag value of 1 may indicate that the block is partitioned in a binary tree form. Alternatively, a QB_flag value of 0 may indicate that the block is partitioned in a binary tree form. A QB_flag value of 1 may indicate that the block is partitioned in a quadtree form.

[0376] "quadtree_flag" may be a flag indicating whether the block is partitioned in a quadtree form. For example, a quadtree_flag value of 1 may indicate that the block is partitioned in a quadtree form. A quadtree_flag value of 0 may indicate that the block is not partitioned in a quadtree form.

[0377] "binarytree_flag" may be a flag indicating whether the block is split in a binary tree form. For example, a binarytree_flag value of 1 may indicate that the block is split in a binary tree form. A binarytree_flag value of 0 may indicate that the block is not split in a binary tree form.

[0378] "Btype_flag" may be a flag indicating which of the vertical partitioning and the horizontal partitioning corresponds to the partitioning direction when the block is partitioned in the binary tree form. For example, a Btype_flag value of 0 may indicate that the block is partitioned in the horizontal direction. A Btype_flag value of 1 may indicate that the block is partitioned in the vertical direction. Alternatively, a Btype_flag value of 0 may indicate that the block is partitioned in the vertical direction. A Btype_flag value of 1 may indicate that the block is partitioned in the horizontal direction.

[0379] For example, as shown in Table 1 below, it can be derived by signaling at least one of quadtree_flag, binarytree_flag, and Btype_flag. Figure 6 The segmentation information of the blocks in .

[0380] [Table 1]

[0381]

[0382] For example, as shown in Table 2 below, it can be derived by signaling at least one of split_flag, QB_flag, and Btype_flag. Figure 6 The segmentation information of the blocks in .

[0383] [Table 2]

[0384]

[0385] Depending on the size and / or shape of the block, the partitioning method may be limited to a quadtree or a binary tree. When this limitation is applied, split_flag may be a flag indicating whether the block is partitioned in a quadtree form or a flag indicating whether the block is partitioned in a binary tree form. The size and shape of the block may be derived from the depth information of the block, and the depth information may be transmitted from the encoding device 100 to the decoding device 200 in a signal.

[0386] When the size of the block falls within a certain range, only segmentation in the form of a quadtree may be possible. For example, the certain range may be defined by at least one of a maximum block size and a minimum block size, wherein only segmentation in the form of a quadtree is possible under the maximum block size and the minimum block size.

[0387] Information indicating a maximum block size and a minimum block size for which only quadtree-type partitioning can be performed may be signaled through a bitstream from the encoding apparatus 100 to the decoding apparatus 200. In addition, the information may be signaled for at least one of units such as a video, a sequence, a picture, a parameter, a tile group, and a slice (or section).

[0388] Alternatively, the maximum block size and / or the minimum block size may be a fixed size predefined by the encoding device 100 and the decoding device 200. For example, when the size of the block is above 64×64 and below 256×256, only segmentation in the form of a quadtree may be possible. In this case, split_flag may be a flag indicating whether segmentation in the form of a quadtree is performed.

[0389] When the size of the block is larger than the maximum size of the transform block, only partitioning in a quadtree form may be possible. Here, the sub-block generated by the partitioning may be at least one of a CU and a TU.

[0390] In this case, split_flag may be a flag indicating whether the CU is partitioned in a quadtree form.

[0391] When the size of the block falls within a specific range, segmentation may be possible only in the form of a binary tree or a ternary tree. For example, the specific range may be defined by at least one of a maximum block size and a minimum block size, wherein segmentation may be possible only in the form of a binary tree or a ternary tree under the maximum block size and the minimum block size.

[0392] Information indicating a maximum block size and / or a minimum block size that can be partitioned only in a binary tree form or in a ternary tree form may be signaled through a bitstream from the encoding apparatus 100 to the decoding apparatus 200. In addition, the information may be signaled for at least one of units such as a sequence, a picture, and a slice (or segment).

[0393] Alternatively, the maximum block size and / or the minimum block size may be a fixed size predefined by the encoding device 100 and the decoding device 200. For example, when the size of the block is above 8×8 and below 16×16, only splitting in a binary tree form may be possible. In this case, split_flag may be a flag indicating whether to perform splitting in a binary tree form or a ternary tree form.

[0394] The above description about partitioning in a quadtree form may be equally applied to a binary tree form and / or a ternary tree form.

[0395] The partitioning of a block may be limited by a previous partitioning. For example, when a block is partitioned in a specific binary tree form and then a plurality of sub-blocks are generated from the partitioning, each sub-block may be partitioned only in a specific tree form. Here, the specific tree form may be at least one of a binary tree form, a ternary tree form, and a quadtree form.

[0396] When the horizontal size or the vertical size of the partition block is a size that cannot be further divided, the above-mentioned indicator may not be signaled.

[0397] Figure 7 is a diagram for explaining an embodiment of an intra prediction process.

[0398] Figure 7 The arrows extending radially from the center of the drawing in FIG. 8 indicate prediction directions of intra prediction modes. In addition, numbers appearing near arrows indicate examples of mode values ​​assigned to intra prediction modes or prediction directions of intra prediction modes.

[0399] exist Figure 7 In the example, the number 0 may represent the planar mode which is a non-directional intra prediction mode, and the number 1 may represent the DC mode which is a non-directional intra prediction mode.

[0400] Intra-frame encoding and / or decoding may be performed using reference samples of neighboring blocks of the target block. The neighboring blocks may be reconstructed neighboring blocks. The reference samples may refer to neighboring samples.

[0401] For example, intra encoding and / or decoding may be performed using values ​​of reference samples included in the reconstructed neighboring block or encoding parameters of the reconstructed neighboring block.

[0402] The encoding device 100 and / or the decoding device 200 may generate a prediction block by performing intra prediction on the target block based on information about samples in the target image. When performing intra prediction, the encoding device 100 and / or the decoding device 200 may generate a prediction block for the target block by performing intra prediction based on information about samples in the target image. When performing intra prediction, the encoding device 100 and / or the decoding device 200 may perform directional prediction and / or non-directional prediction based on at least one reconstructed reference sample.

[0403] The prediction block may be a block generated as a result of performing intra prediction. The prediction block may correspond to at least one of a CU, a PU, and a TU.

[0404] The unit of the prediction block may have a size corresponding to at least one of a CU, a PU, and a TU. The prediction block may have a square shape having a size of 2N×2N or N×N. The size of N×N may include a size of 4×4, 8×8, 16×16, 32×32, 64×64, etc.

[0405] Alternatively, the prediction block may be a square block of size 2×2, 4×4, 8×8, 16×16, 32×32, 64×64, etc. or a rectangular block of size 2×8, 4×8, 2×16, 4×16, 8×16, etc.

[0406] Intra prediction may be performed considering an intra prediction mode for a target block. The number of intra prediction modes that a target block may have may be a predefined fixed value, and may be a value determined differently according to properties of a prediction block. For example, the properties of a prediction block may include a size of a prediction block, a type of a prediction block, etc. In addition, the properties of a prediction block may indicate encoding parameters for the prediction block.

[0407] For example, the number of intra prediction modes may be fixed to N regardless of the size of the prediction block. Alternatively, the number of intra prediction modes may be 3, 5, 9, 17, 34, 35, 36, 65, 67, or 95, for example.

[0408] The intra prediction mode can be a non-directional mode or a directional mode.

[0409] For example, intra prediction modes may include Figure 7 The numbers 0 to 66 shown in FIG. 8 correspond to two non-directional modes and 65 directional modes.

[0410] For example, in the case of using a specific intra prediction method, the intra prediction mode may include Figure 7 The numbers -14 to 80 shown in the figure correspond to two non-directional modes and 93 directional modes.

[0411] The two non-directional modes may include a DC mode and a planar mode.

[0412] The directional mode may be a prediction mode with a specific direction or a specific angle. The directional mode may also be referred to as an "angle mode".

[0413] The intra prediction mode may be represented by at least one of a mode number, a mode value, a mode angle, and a mode direction. In other words, the terms "(mode) number of an intra prediction mode", "(mode) value of an intra prediction mode", "(mode) angle of an intra prediction mode", and "(mode) direction of an intra prediction mode" may be used to have the same meaning and may be used interchangeably with each other.

[0414] The number of intra prediction modes may be M. The value of M may be 1 or more. In other words, the number of intra prediction modes may be M, which includes the number of non-directional modes and the number of directional modes.

[0415] The number of intra prediction modes may be fixed to M regardless of the size of the block and / or the color component. For example, the number of intra prediction modes may be fixed to any one of 35 and 67 regardless of the size of the block.

[0416] Alternatively, the number of intra prediction modes may differ according to the shape, size and / or type of color component of the block.

[0417] For example, in Figure 7 In FIG. 4 , the directional prediction mode indicated by the dotted line can be applied only to the prediction of non-square blocks.

[0418] For example, the larger the size of the block, the larger the number of intra-frame prediction modes. Alternatively, the larger the size of the block, the smaller the number of intra-frame prediction modes. When the size of the block is 4×4 or 8×8, the number of intra-frame prediction modes may be 67. When the size of the block is 16×16, the number of intra-frame prediction modes may be 35. When the size of the block is 32×32, the number of intra-frame prediction modes may be 19. When the size of the block is 64×64, the number of intra-frame prediction modes may be 7.

[0419] For example, the number of intra prediction modes may differ depending on whether the color component is a luma signal or a chroma signal. Alternatively, the number of intra prediction modes corresponding to a luma component block may be greater than the number of intra prediction modes corresponding to a chroma component block.

[0420] For example, in a vertical mode with a mode value of 50, prediction may be performed in a vertical direction based on the pixel values ​​of the reference samples. For example, in a horizontal mode with a mode value of 18, prediction may be performed in a horizontal direction based on the pixel values ​​of the reference samples.

[0421] Even in a directional mode other than the above-described modes, the encoding apparatus 100 and the decoding apparatus 200 may perform intra prediction on a target unit using reference samples according to an angle corresponding to the directional mode.

[0422] An intra-frame prediction mode located to the right relative to the vertical mode may be referred to as a "vertical-right mode". An intra-frame prediction mode located below the horizontal mode may be referred to as a "horizontal-below mode". For example, in Figure 7 , the intra prediction mode having one of the mode values ​​51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, and 66 may be the vertical-right mode. The intra prediction mode having one of the mode values ​​2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and 17 may be the horizontal-down mode.

[0423] The non-directional mode may include a DC mode and a planar mode. For example, the value of the DC mode may be 1. The value of the planar mode may be 0.

[0424] The directional mode may include an angular mode. Among the plurality of intra prediction modes, the remaining modes except the DC mode and the planar mode may be directional modes.

[0425] When the intra prediction mode is the DC mode, the prediction block may be generated based on an average value of pixel values ​​of a plurality of reference pixels. For example, the value of a pixel of the prediction block may be determined based on the average value of pixel values ​​of a plurality of reference pixels.

[0426] The number of intra prediction modes and the mode values ​​of the intra prediction modes are merely exemplary and may be defined differently according to embodiments, implementations and / or requirements.

[0427] In order to perform intra prediction on a target block, a step of checking whether a sample included in a reconstructed neighboring block can be used as a reference sample of the target block may be performed. When there is a sample that cannot be used as a reference sample of the target block among the samples in the neighboring block, a value generated by copying and / or interpolation using at least one sample value among the samples included in the reconstructed neighboring block may replace a sample value of the sample that cannot be used as a reference sample. When the value generated by copying and / or interpolation replaces the sample value of the existing sample, the sample may be used as a reference sample of the target block.

[0428] When intra prediction is used, a filter may be applied to at least one of a reference sample and a prediction sample based on at least one of an intra prediction mode and a size of a target block.

[0429] The type of filter to be applied to at least one of the reference sample and the prediction sample may be different according to at least one of the intra prediction mode of the target block, the size of the target block, and the shape of the target block. The type of filter may be classified according to one or more of the length of the filter tap, the value of the filter coefficient, and the filter strength. The length of the filter tap may mean the number of the filter tap. In addition, the number of the filter tap may mean the length of the filter.

[0430] When the intra prediction mode is the planar mode, when generating a prediction block of a target block, the sample value of the predicted target block can be generated by using a weighted sum of the upper reference sample of the target block, the left reference sample of the target block, the upper right reference sample of the target block, and the lower left reference sample of the target block according to the position of the predicted target sample in the prediction block.

[0431] When the intra prediction mode is the DC mode, when generating a prediction block of a target block, an average value of a reference sample above the target block and a reference sample on the left side of the target block may be used. In addition, filtering using the value of the reference sample may be performed on a specific row or a specific column in the target block. The specific row may be one or more above rows adjacent to the reference sample. The specific column may be one or more left columns adjacent to the reference sample.

[0432] When the intra prediction mode is a directional mode, the prediction block may be generated using an upper reference sample, a left reference sample, an upper right reference sample, and / or a lower left reference sample of the target block.

[0433] In order to generate the above-mentioned prediction samples, real number-based interpolation may be performed.

[0434] The intra prediction mode of the target block may be predicted from intra prediction modes of neighboring blocks adjacent to the target block, and information used for the prediction may be entropy encoded / decoded.

[0435] For example, when the intra prediction modes of the target block and the neighboring block are identical to each other, a predefined flag may be used to signal that the intra prediction modes of the target block and the neighboring block are identical.

[0436] For example, an indicator indicating an intra prediction mode that is the same as the intra prediction mode of the target block among the intra prediction modes of a plurality of neighboring blocks may be signaled.

[0437] When intra prediction modes of a target block and a neighboring block are different from each other, information about the intra prediction mode of the target block may be encoded and / or decoded using entropy encoding and / or decoding.

[0438] Figure 8 is a diagram showing reference samples used in an intra prediction process.

[0439] Reconstructed reference samples used for intra prediction of the target block may include a lower left reference sample, a left reference sample, an upper left reference sample, an upper reference sample, and an upper right reference sample.

[0440] For example, a left reference sample may mean a reconstructed reference pixel adjacent to the left side of the target block. An upper reference sample may mean a reconstructed reference pixel adjacent to the top of the target block. An upper left corner reference sample may mean a reconstructed reference pixel located at the upper left corner of the target block. A lower left corner reference sample may mean a reference sample located below the left sample line among samples located on the same line as the left sample line composed of the left reference samples. An upper right corner reference sample may mean a reference sample located on the same line as the upper sample line composed of the upper reference samples and located to the right of the upper sample line.

[0441] When the size of the target block is N×N, the number of lower left reference samples, left reference samples, upper reference samples, and upper right reference samples may each be N.

[0442] By performing intra prediction on the target block, a prediction block may be generated. Generating the prediction block may include determining values ​​of pixels in the prediction block. The target block and the prediction block may be equal in size.

[0443] The reference samples used for intra prediction of the target block may vary according to the intra prediction mode of the target block. The direction of the intra prediction mode may represent the dependency between the reference samples and the pixels of the prediction block. For example, the value of a specified reference sample may be used as the value of one or more specified pixels in the prediction block. In this case, the specified reference sample and one or more specified pixels in the prediction block may be samples and pixels located on a straight line in the direction of the intra prediction mode. In other words, the value of the specified reference sample may be copied as the value of a pixel located in a direction opposite to the direction of the intra prediction mode. Alternatively, the value of a pixel in the prediction block may be the value of a reference sample located in the direction of the intra prediction mode relative to the position of the pixel.

[0444] In an example, when the intra prediction mode of the target block is a vertical mode, the upper reference sample can be used for intra prediction. When the intra prediction mode is a vertical mode, the value of a pixel in the prediction block can be the value of a reference sample located vertically above the position of the pixel. Therefore, the upper reference sample adjacent to the top of the target block can be used for intra prediction. In addition, the value of a pixel in a row of the prediction block can be the same as the value of the above reference sample.

[0445] In an example, when the intra prediction mode of the target block is the horizontal mode, the left reference sample may be used for intra prediction. When the intra prediction mode is the horizontal mode, the value of a pixel in the prediction block may be the value of a reference sample located horizontally to the left of the position of the pixel. Therefore, the left reference sample adjacent to the left side of the target block may be used for intra prediction. In addition, the value of a pixel in a column of the prediction block may be the same as the value of the left reference sample.

[0446] In an example, when the mode value of the intra prediction mode of the current block is 34, at least some of the left reference samples, the upper left reference samples, and at least some of the upper reference samples may be used for intra prediction. When the mode value of the intra prediction mode is 34, the value of a pixel in the prediction block may be the value of a reference sample diagonally located at the upper left corner of the pixel.

[0447] Furthermore, in the case of an intra prediction mode whose mode value is a value within a range of 52 to 66, at least a portion of the upper right reference sample may be used for intra prediction.

[0448] Furthermore, in the case of an intra prediction mode whose mode value is a value within a range of 2 to 17, at least a portion of the lower left reference samples may be used for intra prediction.

[0449] Also, in the case of an intra prediction mode whose mode value is a value within a range of 19 to 49, the top left corner reference sample may be used for intra prediction.

[0450] The number of reference samples used to determine the pixel value of one pixel in the prediction block may be 1 or 2 or more.

[0451] As described above, the pixel value of the pixel in the prediction block may be determined according to the position of the pixel and the position of the reference sample indicated by the direction of the intra prediction mode. When the position of the pixel and the position of the reference sample indicated by the direction of the intra prediction mode are integer positions, the value of one reference sample indicated by the integer position may be used to determine the pixel value of the pixel in the prediction block.

[0452] When the position of a pixel and the position of a reference sample indicated by the direction of an intra prediction mode are not integer positions, an interpolated reference sample based on two reference samples closest to the position of the reference sample may be generated. The value of the interpolated reference sample may be used to determine the pixel value of a pixel in a prediction block. In other words, when the position of a pixel in a prediction block and the position of a reference sample indicated by the direction of an intra prediction mode indicate a position between two reference samples, an interpolated value based on the values ​​of the two samples may be generated.

[0453] The prediction block generated via prediction may not be the same as the original target block. In other words, there may be a prediction error as the difference between the target block and the prediction block, and there may also be a prediction error between the pixels of the target block and the pixels of the prediction block.

[0454] Hereinafter, the terms “difference”, “error” and “residual” may be used to have the same meaning and may be used interchangeably with each other.

[0455] For example, in the case of directional intra prediction, the longer the distance between the pixels of the prediction block and the reference samples, the greater the prediction error that may occur. Such prediction error may lead to discontinuities between the generated prediction block and neighboring blocks.

[0456] In order to reduce the prediction error, filtering for the prediction block can be used. The filtering can be configured to adaptively apply the filter to the area in the prediction block that is considered to have a large prediction error. For example, the area considered to have a large prediction error can be the boundary of the prediction block. In addition, the area in the prediction block that is considered to have a large prediction error can be different according to the intra-frame prediction mode, and the characteristics of the filter can also be different according to the intra-frame prediction mode.

[0457] like Figure 8 As shown, for intra prediction of the target block, at least one of reference lines 0 to 3 may be used.

[0458] Figure 8 Each reference line in may indicate a reference sample point line including one or more reference sample points. When the number of the reference line is smaller, it may indicate that the line of the reference sample points is closer to the target block.

[0459] The samples in the partitions A and F may be obtained by filling with the samples in the partitions B and E that are closest to the target block, rather than being obtained from the reconstructed neighboring blocks.

[0460] Index information indicating a reference sample line to be used for intra prediction of a target block may be transmitted by a signal. The index information may indicate a reference sample line to be used for intra prediction of a target block among a plurality of reference sample lines. For example, the index information may have a value corresponding to any one of 0 to 3.

[0461] When the top boundary of the target block is the boundary of the CTU, only the reference sample line 0 may be available. Therefore, in this case, the index information may not be signaled. When an additional reference sample line other than the reference sample line 0 is used, filtering of the prediction block to be described later may not be performed.

[0462] In case of inter-color intra prediction, a prediction block for a target block of a second color component may be generated based on a corresponding reconstructed block of a first color component.

[0463] For example, the first color component may be a luminance component and the second color component may be a chrominance component.

[0464] To perform inter-color intra prediction, parameters for a linear model between a first color component and a second color component may be derived based on the template.

[0465] The template may include reference samples above the target block (upper reference samples) and / or reference samples on the left side of the target block (left reference samples), and may include upper reference samples and / or left reference samples of the reconstructed block of the first color component corresponding to the reference samples.

[0466] For example, parameters for a linear model may be derived using 1) the value of a sample having a maximum value of a first color component among the samples in a template, 2) the value of a sample of a second color component corresponding to the sample of the first color component, 3) the value of a sample having a minimum value of the first color component among the samples in the template, and 4) the value of a sample of a second color component corresponding to the sample of the first color component.

[0467] When the parameters for the linear model are derived, a prediction block for the target block may be generated by applying the corresponding reconstructed block to the linear model.

[0468] Depending on the image format, subsampling may be performed on samples adjacent to a reconstructed block of a first color component and a corresponding reconstructed block of the first color component. For example, when one sample of a second color component corresponds to four samples of a first color component, one corresponding sample may be calculated by performing subsampling on four samples of the first color component. When subsampling is performed, derivation of parameters for a linear model and inter-color intra prediction may be performed based on the corresponding samples of the subsampling.

[0469] Information on whether to perform inter-color intra prediction and / or the range of a template may be signaled in an intra prediction mode.

[0470] The target block may be partitioned into two or four sub-blocks in a horizontal direction and / or a vertical direction.

[0471] The sub-blocks generated by partitioning may be sequentially reconstructed. That is, when intra prediction is performed on each sub-block, a sub-prediction block for the sub-block may be generated. In addition, when inverse quantization (inverse quantization) and / or inverse transformation is performed on each sub-block, a sub-residual block for the corresponding sub-block may be generated. The reconstructed sub-block may be generated by adding the sub-prediction block to the sub-residual block. The reconstructed sub-block may be used as a reference sample for intra prediction of a sub-block having the next priority.

[0472] A subblock may be a block including a certain number (e.g., 16) of samples or more. For example, when the target block is an 8×4 block or a 4×8 block, the target block may be partitioned into two subblocks. In addition, when the target block is a 4×4 block, the target block cannot be partitioned into subblocks. When the target block has another size, the target block may be partitioned into four subblocks.

[0473] Information about whether to perform intra prediction based on such a subblock and / or information about a partition direction (horizontal direction or vertical direction) may be signaled.

[0474] Such subblock-based intra prediction may be restricted such that it is performed only when using reference sample line 0. When subblock-based intra prediction is performed, filtering of a prediction block to be described below may not be performed.

[0475] A final prediction block may be generated by performing filtering on a prediction block generated through intra prediction.

[0476] The filtering may be performed by applying a specific weight to a filtering target sample, a left reference sample, an upper reference sample, and / or an upper left reference sample, wherein the filtering target sample is a target to be filtered.

[0477] The weight and / or reference samples (eg, range of reference samples, position of reference samples, etc.) used for filtering may be determined based on at least one of a block size, an intra prediction mode, and a position of a filtering target sample in a prediction block.

[0478] For example, filtering may be performed only in a specific intra prediction mode (eg, a DC mode, a planar mode, a vertical mode, a horizontal mode, a diagonal mode, and / or an adjacent diagonal mode).

[0479] The adjacent diagonal pattern may be a pattern having a number obtained by adding k to the number of the diagonal pattern, and may be a pattern having a number obtained by subtracting k from the number of the diagonal pattern. In other words, the number of the adjacent diagonal pattern may be the sum of the number of the diagonal pattern and k, or may be the difference between the number of the diagonal pattern and k. For example, k may be a positive integer of 8 or less.

[0480] The intra prediction mode of the target block may be derived using intra prediction modes of neighboring blocks existing near the target block, and the intra prediction mode thus derived may be entropy encoded and / or entropy decoded.

[0481] For example, when the intra prediction mode of the target block is the same as that of the neighboring block, information indicating that the intra prediction mode of the target block is the same as that of the neighboring block may be signaled using specific flag information.

[0482] In addition, for example, indicator information for a neighboring block of an intra prediction mode identical to the intra prediction mode of the target block among intra prediction modes having a plurality of neighboring blocks may be signaled.

[0483] For example, when the intra prediction mode of the target block is different from the intra prediction mode of the neighboring block, information about the intra prediction mode of the target block may be entropy encoded and / or decoded by performing entropy encoding and / or entropy decoding based on the intra prediction mode of the neighboring block.

[0484] Fig. 9 is a diagram for explaining an embodiment of an inter-frame prediction process.

[0485] Fig. 9 The rectangle shown in can represent an image (or picture). Fig. 9 In the example, an arrow may indicate a prediction direction. An arrow pointing from a first picture to a second picture means that the second picture refers to the first picture. That is, each picture may be encoded and / or decoded according to the prediction direction.

[0486] According to the encoding type, images can be classified into intra-frame pictures (I pictures), unidirectional prediction pictures or predictive coding pictures (P pictures), and bidirectional prediction pictures or bidirectional prediction coding pictures (B pictures). Each picture can be encoded and / or decoded according to its encoding type.

[0487] When a target image to be encoded is an I picture, the target image may be encoded using data contained in the image itself without performing inter-frame prediction with reference to other images. For example, an I picture may be encoded only via intra-frame prediction.

[0488] When the target image is a P picture, the target image may be encoded via inter prediction using a reference picture existing in one direction. Here, the one direction may be a forward direction or a backward direction.

[0489] When the target image is a B picture, the image may be encoded via inter-frame prediction using reference pictures existing in two directions, or may be encoded via inter-frame prediction using reference pictures existing in one of a forward direction and a backward direction. Here, the two directions may be a forward direction and a backward direction.

[0490] P pictures and B pictures encoded and / or decoded using reference pictures may be regarded as images using inter-frame prediction.

[0491] Hereinafter, inter prediction in the inter mode according to an embodiment will be described in detail.

[0492] Inter-frame prediction or motion compensation may be performed using a reference image and motion information.

[0493] In the inter mode, the encoding apparatus 100 may perform inter prediction and / or motion compensation on the target block. The decoding apparatus 200 may perform inter prediction and / or motion compensation corresponding to the inter prediction and / or motion compensation performed by the encoding apparatus 100 on the target block.

[0494] During inter prediction, motion information of a target block may be separately derived by the encoding apparatus 100 and the decoding apparatus 200. The motion information may be derived using motion information of a reconstructed neighboring block, motion information of a col block, and / or motion information of a block adjacent to the col block.

[0495] For example, the encoding apparatus 100 or the decoding apparatus 200 may perform prediction and / or motion compensation by using motion information of the spatial candidate and / or the temporal candidate as motion information of the target block. The target block may mean a PU and / or a PU partition.

[0496] The spatial candidates may be reconstructed blocks that are spatially adjacent to the target block.

[0497] The temporal candidate may be a reconstructed block in a previously reconstructed co-located picture (col picture) corresponding to the target block.

[0498] In inter-frame prediction, the encoding device 100 and the decoding device 200 can improve encoding efficiency and decoding efficiency by using motion information of spatial candidates and / or temporal candidates. The motion information of the spatial candidate may be referred to as "spatial motion information". The motion information of the temporal candidate may be referred to as "temporal motion information".

[0499] Hereinafter, the motion information of the spatial candidate may be the motion information of the PU including the spatial candidate. The motion information of the temporal candidate may be the motion information of the PU including the temporal candidate. The motion information of the candidate block may be the motion information of the PU including the candidate block.

[0500] Inter prediction may be performed using reference pictures.

[0501] The reference picture may be at least one of a picture before the target picture and a picture after the target picture. The reference picture may be an image used for prediction of the target block.

[0502] In inter prediction, a region in a reference picture may be specified by using a reference picture index (or refIdx) indicating a reference picture, a motion vector (to be described later), etc. Here, the region specified in the reference picture may indicate a reference block.

[0503] Inter prediction may select a reference picture, and may also select a reference block corresponding to a target block from the reference picture. In addition, inter prediction may use the selected reference block to generate a prediction block for the target block.

[0504] Motion information may be derived by each of the encoding apparatus 100 and the decoding apparatus 200 during inter prediction.

[0505] A spatial candidate may be a block that satisfies the following items: 1) exists in the target picture, 2) has been previously reconstructed via encoding and / or decoding, and 3) is adjacent to the target block or is located at the corner of the target block. Here, a "block located at the corner of the target block" may be a block that is adjacent to the target block in the horizontal direction in the vertical direction, or may be a block that is adjacent to the target block in the vertical direction in the horizontal direction. In addition, a "block located at the corner of the target block" may have the same meaning as a "block adjacent to the corner of the target block". The meaning of a "block located at the corner of the target block" may be included in the meaning of a "block adjacent to the target block".

[0506] For example, the spatial candidate may be a reconstructed block located at the left side of the target block, a reconstructed block located above the target block, a reconstructed block located at the lower left corner of the target block, a reconstructed block located at the upper right corner of the target block, or a reconstructed block located at the upper left corner of the target block.

[0507] Each of the encoding apparatus 100 and the decoding apparatus 200 may identify a block existing at a position spatially corresponding to the target block in the col picture. The position of the target block in the target picture and the position of the identified block in the col picture may correspond to each other.

[0508] Each of the encoding apparatus 100 and the decoding apparatus 200 may determine the col block existing at a predefined relative position with respect to the identified block as a temporal candidate. The predefined relative position may be a position existing inside and / or outside the identified block.

[0509] For example, the col block may include a first col block and a second col block. When the coordinates of the identified block are (xP, yP) and the size of the identified block is represented by (nPSW, nPSH), the first col block may be a block located at the coordinates (xP+nPSW, yP+nPSH). The second col block may be a block located at the coordinates (xP+(nPSW>>1), yP+(nPSH>>1)). When the first col block is not available, the second col block may be selectively used.

[0510] The motion vector of the target block may be determined based on the motion vector of the col block. Each of the encoding device 100 and the decoding device 200 may scale the motion vector of the col block. The scaled motion vector of the col block may be used as the motion vector of the target block. In addition, the motion vector of the motion information for the temporal candidate stored in the list may be a scaled motion vector.

[0511] The ratio of the motion vector of the target block to the motion vector of the col block may be the same as the ratio of the first temporal distance to the second temporal distance. The first temporal distance may be the distance between the reference picture and the target picture of the target block. The second temporal distance may be the distance between the reference picture and the col picture of the col block.

[0512] The scheme for deriving motion information may change according to the inter prediction mode of the target block. For example, as an inter prediction mode applied to inter prediction, there may be an advanced motion vector prediction (AMVP) mode, a merge mode, a skip mode, a merge mode with a motion vector difference, a sub-block merge mode, a triangle partition mode, an inter-intra combined prediction mode, an affine inter mode, a current picture reference mode, etc. The merge mode may also be referred to as a "motion merge mode". Below, each mode is described in detail.

[0513] 1) AMVP model

[0514] When the AMVP mode is used, the encoding device 100 may search for a similar block in a neighboring area of ​​the target block. The encoding device 100 may obtain a prediction block by performing prediction on the target block using motion information of the found similar block. The encoding device 100 may encode a residual block, which is a difference between the target block and the prediction block.

[0515] 1-1) Creation of a list of motion vector prediction candidates

[0516] When the AMVP mode is used as the prediction mode, each of the encoding device 100 and the decoding device 200 may create a prediction motion vector candidate list using a motion vector of a spatial candidate, a motion vector of a temporal candidate, and a zero vector. The prediction motion vector candidate list may include one or more prediction motion vector candidates. At least one of the motion vector of the spatial candidate, the motion vector of the temporal candidate, and the zero vector may be determined and used as a prediction motion vector candidate.

[0517] Hereinafter, the terms "prediction motion vector (candidate)" and "motion vector (candidate)" may be used to have the same meaning and may be used interchangeably with each other.

[0518] Hereinafter, the terms “prediction motion vector candidate” and “AMVP candidate” may be used to have the same meaning and may be used interchangeably with each other.

[0519] Hereinafter, the terms “prediction motion vector candidate list” and “AMVP candidate list” may be used to have the same meaning and may be used interchangeably with each other.

[0520] The spatial candidate may include a reconstructed spatial neighboring block. In other words, the motion vector of the reconstructed neighboring block may be referred to as a "spatial prediction motion vector candidate".

[0521] The temporal candidate may include the col block and blocks adjacent to the col block. In other words, the motion vector of the col block or the motion vector of the block adjacent to the col block may be referred to as a "temporal prediction motion vector candidate".

[0522] The zero vector may be the (0,0) motion vector.

[0523] The predicted motion vector candidate may be a motion vector predictor for predicting a motion vector. In addition, in the encoding apparatus 100, each predicted motion vector candidate may be an initial search position for a motion vector.

[0524] 1-2) Searching for a motion vector using a list of predicted motion vector candidates

[0525] The encoding device 100 may determine a motion vector to be used for encoding a target block within a search range using the list of predicted motion vector candidates. In addition, the encoding device 100 may determine a predicted motion vector candidate to be used as a predicted motion vector of a target block among the predicted motion vector candidates present in the predicted motion vector candidate list.

[0526] The motion vector to be used for encoding the target block may be a motion vector that can be encoded at a minimum cost.

[0527] Also, the encoding apparatus 100 may determine whether to encode the target block using the AMVP mode.

[0528] 1-3) Transmission of inter-frame prediction information

[0529] The encoding apparatus 100 may generate a bitstream including inter prediction information required for inter prediction, and the decoding apparatus 200 may perform inter prediction on a target block using the inter prediction information of the bitstream.

[0530] The inter prediction information may include: 1) mode information indicating whether the AMVP mode is used, 2) a prediction motion vector index, 3) a motion vector difference (MVD), 4) a reference direction, and 5) a reference picture index.

[0531] Hereinafter, the terms 'prediction motion vector index' and 'AMVP index' may be used to have the same meaning and may be used interchangeably with each other.

[0532] In addition, the inter prediction information may include a residual signal.

[0533] When the mode information indicates that the AMVP mode is used, the decoding apparatus 200 may acquire a prediction motion vector index, an MVD, a reference direction, and a reference picture index from a bitstream through entropy decoding.

[0534] The predicted motion vector index may indicate a predicted motion vector candidate to be used for prediction of the target block among the predicted motion vector candidates included in the predicted motion vector candidate list.

[0535] 1-4) Inter-frame prediction in AMVP mode using inter-frame prediction information

[0536] The decoding apparatus 200 may derive a prediction motion vector candidate using the prediction motion vector candidate list, and may determine motion information of a target block based on the derived prediction motion vector candidate.

[0537] The decoding device 200 may determine a motion vector candidate for the target block among the predicted motion vector candidates included in the predicted motion vector candidate list using the predicted motion vector index. The decoding device 200 may select the predicted motion vector candidate indicated by the predicted motion vector index from among the predicted motion vector candidates included in the predicted motion vector candidate list as the predicted motion vector of the target block.

[0538] The encoding device 100 may generate an entropy-coded predicted motion vector index by applying entropy coding to the predicted motion vector index, and may generate a bitstream including the entropy-coded predicted motion vector index. The entropy-coded predicted motion vector index may be signaled from the encoding device 100 to the decoding device 200 through the bitstream. The decoding device 200 may extract the entropy-coded predicted motion vector index from the bitstream, and may obtain the predicted motion vector index by applying entropy decoding to the entropy-coded predicted motion vector index.

[0539] The motion vector to be actually used for inter prediction of the target block may not match the predicted motion vector. In order to indicate the difference between the motion vector to be actually used for inter prediction of the target block and the predicted motion vector, MVD may be used. The encoding apparatus 100 may derive a predicted motion vector similar to the motion vector to be actually used for inter prediction of the target block so as to use as small an MVD as possible.

[0540] The motion vector difference (MVD) may be a difference between a motion vector of a target block and a predicted motion vector. The encoding apparatus 100 may calculate the MVD, and may generate an entropy-coded MVD by applying entropy coding to the MVD. The encoding apparatus 100 may generate a bitstream including the entropy-coded MVD.

[0541] The MVD may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 may extract the entropy-encoded MVD from the bitstream, and may acquire the MVD by applying entropy decoding to the entropy-encoded MVD.

[0542] The decoding apparatus 200 may derive the motion vector of the target block by summing the MVD and the predicted motion vector. In other words, the motion vector of the target block derived by the decoding apparatus 200 may be the sum of the MVD and the motion vector candidate.

[0543] In addition, the encoding device 100 may generate entropy-encoded MVD resolution information by applying entropy encoding to the calculated MVD resolution information, and may generate a bitstream including the entropy-encoded MVD resolution information. The decoding device 200 may extract the entropy-encoded MVD resolution information from the bitstream, and may obtain the MVD resolution information by applying entropy decoding to the entropy-encoded MVD resolution information. The decoding device 200 may use the MVD resolution information to adjust the resolution of the MVD.

[0544] In addition, the encoding apparatus 100 may calculate the MVD based on the affine model. The decoding apparatus 200 may derive the affine controlled motion vector of the target block through the sum of the MVD and the affine controlled motion vector candidate, and may derive the motion vector of the subblock using the affine controlled motion vector.

[0545] The reference direction may indicate a list of reference pictures to be used for prediction of the target block. For example, the reference direction may indicate one of reference picture list L0 and reference picture list L1.

[0546] The reference direction only indicates a reference picture list to be used for prediction of a target block and may not mean that the direction of the reference picture is limited to the forward direction or the backward direction. In other words, each of the reference picture lists L0 and L1 may include pictures in the forward direction and / or the backward direction.

[0547] The reference direction being unidirectional may mean using a single reference picture list. The reference direction being bidirectional may mean using two reference picture lists. In other words, the reference direction may indicate one of a case where only reference picture list L0 is used, a case where only reference picture list L1 is used, and a case where two reference picture lists are used.

[0548] The reference picture index may indicate a reference picture used to predict the target block among the reference pictures present in the reference picture list. The encoding apparatus 100 may generate an entropy-coded reference picture index by applying entropy coding to the reference picture index, and may generate a bitstream including the entropy-coded reference picture index. The entropy-coded reference picture index may be signaled from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 may extract the entropy-coded reference picture index from the bitstream, and may obtain the reference picture index by applying entropy decoding to the entropy-coded reference picture index.

[0549] When two reference picture lists are used to predict a target block, a single reference picture index and a single motion vector may be used for each of the reference picture lists. In addition, when two reference picture lists are used to predict a target block, two prediction blocks may be specified for the target block. For example, an average or weighted sum of the two prediction blocks of the target block may be used to generate the (final) prediction block of the target block.

[0550] The motion vector of the target block may be derived by predicting the motion vector index, MVD, reference direction, and reference picture index.

[0551] The decoding apparatus 200 may generate a prediction block for the target block based on the derived motion vector and the reference picture index. For example, the prediction block may be a reference block indicated by the derived motion vector in the reference picture indicated by the reference picture index.

[0552] Since the predicted motion vector index and the MVD are encoded without encoding the motion vector itself of the target block, the number of bits transmitted from the encoding apparatus 100 to the decoding apparatus 200 may be reduced, and encoding efficiency may be improved.

[0553] For the target block, the motion information of the reconstructed neighboring blocks may be used. In a specific inter-frame prediction mode, the encoding device 100 may not separately encode the actual motion information of the target block. Instead of encoding the motion information of the target block, additional information that can derive the motion information of the target block using the motion information of the reconstructed neighboring blocks may be encoded. Since the additional information is encoded, the number of bits sent to the decoding device 200 may be reduced, and the encoding efficiency may be improved.

[0554] For example, as an inter-frame prediction mode in which the motion information of the target block is not directly encoded, there may be a skip mode and / or a merge mode. Here, each of the encoding device 100 and the decoding device 200 may use an identifier and / or an index indicating a unit whose motion information among the reconstructed neighboring units is to be used as the motion information of the target unit.

[0555] 2) Merge mode

[0556] As a scheme for deriving motion information of a target block, there is merging. The term "merge" may mean the merging of motions of multiple blocks. "Merge" may mean that the motion information of one block is also applied to other blocks. In other words, the merge mode may be a mode of deriving the motion information of the target block from the motion information of the neighboring blocks.

[0557] When using merge mode, the encoding device 100 may use the motion information of the spatial candidate and / or the motion information of the temporal candidate to predict the motion information of the target block. The spatial candidate may include a reconstructed spatial neighboring block that is spatially adjacent to the target block. The spatial neighboring blocks may include a left neighboring block and an upper neighboring block. The temporal candidate may include a col block. The terms "spatial candidate" and "spatial merge candidate" may be used to have the same meaning and may be used interchangeably with each other. The terms "temporal candidate" and "temporal merge candidate" may be used to have the same meaning and may be used interchangeably with each other.

[0558] The encoding apparatus 100 may obtain a prediction block through prediction. The encoding apparatus 100 may encode a residual block, which is a difference between a target block and a prediction block.

[0559] 2-1) Creation of Merge Candidate List

[0560] When the merge mode is used, each of the encoding device 100 and the decoding device 200 may create a merge candidate list using motion information of a spatial candidate and / or motion information of a temporal candidate. The motion information may include 1) a motion vector, 2) a reference picture index, and 3) a reference direction. The reference direction may be unidirectional or bidirectional. The reference direction may mean an inter-frame prediction indicator.

[0561] The merge candidate list may include a merge candidate. The merge candidate may be motion information. In other words, the merge candidate list may be a list in which a plurality of pieces of motion information are stored.

[0562] The merge candidate may be a plurality of pieces of motion information of a temporal candidate and / or a spatial candidate. In other words, the merge candidate list may include motion information of a temporal candidate and / or a spatial candidate, etc.

[0563] Furthermore, the merge candidate list may include a new merge candidate generated by combining merge candidates already present in the merge candidate list. In other words, the merge candidate list may include new motion information generated by combining a plurality of pieces of motion information previously present in the merge candidate list.

[0564] In addition, the merge candidate list may include a history-based merge candidate. The history-based merge candidate may be motion information of a block encoded and / or decoded before the target block.

[0565] Furthermore, the merge candidate list may include a merge candidate based on an average of two merge candidates.

[0566] The merge candidate may be a specific mode for deriving inter-frame prediction information. The merge candidate may be information indicating a specific mode for deriving inter-frame prediction information. The inter-frame prediction information of the target block may be derived according to the specific mode indicated by the merge candidate. In addition, the specific mode may include a process for deriving a series of inter-frame prediction information. The specific mode may be an inter-frame prediction information derivation mode or a motion information derivation mode.

[0567] Inter prediction information of the target block may be derived according to a mode indicated by a merge candidate selected by a merge index among merge candidates in the merge candidate list.

[0568] For example, the motion information derivation mode in the merge candidate list may be at least one of 1) a motion information derivation mode for a sub-block unit and 2) an affine motion information derivation mode.

[0569] In addition, the merge candidate list may include motion information of a zero vector. A zero vector may also be referred to as a "zero merge candidate."

[0570] In other words, the multiple motion information in the merge candidate list can be at least one of the following items: 1) motion information of spatial candidates, 2) motion information of temporal candidates, 3) motion information generated by combining multiple motion information previously existing in the merge candidate list, and 4) zero vector.

[0571] The motion information may include: 1) a motion vector, 2) a reference picture index, and 3) a reference direction. The reference direction may also be referred to as an "inter prediction indicator". The reference direction may be unidirectional or bidirectional. A unidirectional reference direction may indicate L0 prediction or L1 prediction.

[0572] A merge candidate list may be created before performing prediction in merge mode.

[0573] The number of merge candidates in the merge candidate list may be predefined. Each of the encoding device 100 and the decoding device 200 may add merge candidates to the merge candidate list according to a predefined scheme and a predefined priority so that the merge candidate list has a predefined number of merge candidates. The merge candidate list of the encoding device 100 and the merge candidate list of the decoding device 200 may be made identical to each other using a predefined scheme and a predefined priority.

[0574] Merging may be applied on a CU or PU basis. When merging is performed on a CU or PU basis, the encoding apparatus 100 may transmit a bitstream including predefined information to the decoding apparatus 200. For example, the predefined information may include: 1) information indicating whether merging is performed for each block partition, and 2) information about a block to be merged with, among blocks that are spatial candidates and / or temporal candidates for a target block.

[0575] 2-2) Searching for motion vectors using the merge candidate list

[0576] The encoding device 100 may determine a merge candidate to be used for encoding the target block. For example, the encoding device 100 may perform prediction on the target block using a merge candidate in the merge candidate list, and may generate a residual block for the merge candidate. The encoding device 100 may encode the target block using a merge candidate that causes the minimum cost in encoding the prediction and residual block.

[0577] Also, the encoding apparatus 100 may determine whether to encode the target block using the merge mode.

[0578] 2-3) Transmission of inter-frame prediction information

[0579] The encoding device 100 may generate a bitstream including inter-frame prediction information required for inter-frame prediction. The encoding device 100 may generate entropy-coded inter-frame prediction information by performing entropy encoding on the inter-frame prediction information, and may transmit the bitstream including the entropy-coded inter-frame prediction information to the decoding device 200. Through the bitstream, the entropy-coded inter-frame prediction information may be signaled by the encoding device 100 to the decoding device 200. The decoding device 200 may extract the entropy-coded inter-frame prediction information from the bitstream, and may obtain the inter-frame prediction information by applying entropy decoding to the entropy-coded inter-frame prediction information.

[0580] The decoding apparatus 200 may perform inter prediction on the target block using inter prediction information of the bitstream.

[0581] The inter prediction information may include: 1) mode information indicating whether a merge mode is used, 2) a merge index, and 3) correction information.

[0582] In addition, the inter prediction information may include a residual signal.

[0583] Only when the mode information indicates that the merge mode is used, the decoding apparatus 200 may acquire the merge index from the bitstream.

[0584] The mode information may be a merge flag. The unit of the mode information may be a block. The information about the block may include the mode information, and the mode information may indicate whether the merge mode is applied to the block.

[0585] The merge index may indicate a merge candidate to be used for prediction of the target block among merge candidates included in the merge candidate list. Alternatively, the merge index may indicate a block with which the target block is to be merged among neighboring blocks adjacent to the target block in space or time.

[0586] The encoding apparatus 100 may select a merge candidate having the highest encoding performance among the merge candidates included in the merge candidate list, and set a value of the merge index to indicate the selected merge candidate.

[0587] The correction information may be information for correcting a motion vector. The encoding apparatus 100 may generate the correction information. The decoding apparatus 200 may correct a motion vector of a merge candidate selected by a merge index based on the correction information.

[0588] The correction information may include at least one of information indicating whether correction is to be performed, correction direction information, and correction size information. A prediction mode that corrects a motion vector based on signaled correction information may be referred to as a 'merge mode with motion vector difference'.

[0589] 2-4) Inter-frame prediction using merge mode of inter-frame prediction information

[0590] The decoding apparatus 200 may perform prediction on the target block using a merge candidate indicated by a merge index among merge candidates included in the merge candidate list.

[0591] The motion vector of the target block may be specified by the motion vector of the merge candidate indicated by the merge index, the reference picture index, and the reference direction.

[0592] 3) Skip mode

[0593] The skip mode may be a mode in which the motion information of the spatial candidate or the motion information of the temporal candidate is applied to the target block without change. In addition, the skip mode may be a mode in which the residual signal is not used. In other words, when the skip mode is used, the reconstructed block may be the same as the predicted block.

[0594] The difference between the merge mode and the skip mode is whether the residual signal is transmitted or used. That is, the skip mode may be similar to the merge mode except that the residual signal is not transmitted or used.

[0595] When the skip mode is used, the encoding device 100 may transmit information about a block whose motion information is to be used as the motion information of the target block among blocks that are spatial candidates or temporal candidates to the decoding device 200 through a bitstream. The encoding device 100 may generate entropy-coded information by performing entropy encoding on the information, and may signal the entropy-coded information to the decoding device 200 through a bitstream. The decoding device 200 may extract the entropy-coded information from the bitstream, and may obtain the information by applying entropy decoding to the entropy-coded information.

[0596] In addition, when the skip mode is used, the encoding device 100 may not transmit other syntax information, such as MVD, to the decoding device 200. For example, when the skip mode is used, the encoding device 100 may not signal a syntax element related to at least one of the MVD, the coded block flag, and the transform coefficient level to the decoding device 200.

[0597] 3-1) Creation of Merge Candidate List

[0598] The skip mode may also use a merge candidate list. In other words, the merge candidate list may be used in both the merge mode and the skip mode. In this regard, the merge candidate list may also be referred to as a "skip candidate list" or a "merge / skip candidate list".

[0599] Optionally, the skip mode may use an additional candidate list different from the merge candidate list of the merge mode. In this case, in the following description, the merge candidate list and the merge candidate may be replaced with the skip candidate list and the skip candidate, respectively.

[0600] The merge candidate list may be created before performing prediction in skip mode.

[0601] 3-2) Searching for motion vectors using the merge candidate list

[0602] The encoding device 100 may determine a merge candidate to be used for encoding the target block. For example, the encoding device 100 may perform prediction on the target block using a merge candidate in the merge candidate list. The encoding device 100 may encode the target block using a merge candidate that causes the minimum cost in prediction.

[0603] Also, the encoding apparatus 100 may determine whether to encode the target block using the skip mode.

[0604] 3-3) Transmission of inter-frame prediction information

[0605] The encoding apparatus 100 may generate a bitstream including inter prediction information required for inter prediction, and the decoding apparatus 200 may perform inter prediction on a target block using the inter prediction information in the bitstream.

[0606] The inter prediction information may include: 1) mode information indicating whether a skip mode is used, and 2) a skip index.

[0607] The skip index can be the same as the merge index described above.

[0608] When the skip mode is used, the target block may be encoded without using the residual signal. The inter prediction information may not include the residual signal. Alternatively, the bitstream may not include the residual signal.

[0609] Only when the mode information indicates that the skip mode is used, the decoding device 200 can obtain the skip index from the bitstream. As described above, the merge index and the skip index may be the same as each other. Only when the mode information indicates that the merge mode or the skip mode is used, the decoding device 200 can obtain the skip index from the bitstream.

[0610] The skip index may indicate a merge candidate to be used for prediction of the target block among the merge candidates included in the merge candidate list.

[0611] 3-4) Inter-frame prediction in skip mode using inter-frame prediction information

[0612] The decoding apparatus 200 may perform prediction on the target block using a merge candidate indicated by a skip index among merge candidates included in the merge candidate list.

[0613] The motion vector of the target block may be specified by the motion vector of the merge candidate indicated by the skip index, the reference picture index, and the reference direction.

[0614] 4) Current picture reference mode

[0615] The current picture reference mode may indicate a prediction mode using a previously reconstructed area in a target picture to which the target block belongs.

[0616] A motion vector for specifying a previously reconstructed area may be used.A reference picture index of a target block may be used to determine whether the target block has been encoded in a current picture reference mode.

[0617] A flag or index indicating whether the target block is a block encoded in the current picture reference mode may be signaled by the encoding apparatus 100 to the decoding apparatus 200. Alternatively, whether the target block is a block encoded in the current picture reference mode may be inferred by a reference picture index of the target block.

[0618] When the target block is encoded in the current picture reference mode, the target picture may exist at a fixed position or an arbitrary position in the reference picture list for the target block.

[0619] For example, the fixed position may be a position where the value of the reference picture index is 0 or a last position.

[0620] When a target picture exists at an arbitrary position in the reference picture list, an additional reference picture index indicating such an arbitrary position may be signaled by the encoding apparatus 100 to the decoding apparatus 200 .

[0621] 5) Sub-block merging mode

[0622] The sub-block merge mode may be a mode in which motion information is derived from sub-blocks of a CU.

[0623] When the subblock merge mode is applied, the subblock merge candidate list may be generated using the motion information of the co-located subblock (col subblock) of the target subblock in the reference image (ie, subblock-based temporal merge candidates) and / or affine control point motion vector merge candidates.

[0624] 6) Triangle partition mode

[0625] In the triangular partition mode, the target block may be partitioned in the diagonal direction, and sub-target blocks generated by the partitioning may be generated. For each sub-target block, motion information of the corresponding sub-target block may be derived, and the derived motion information may be used to derive prediction samples for each sub-target block. The prediction samples of the target block may be derived by a weighted sum of the prediction samples of the sub-target blocks generated by the partitioning.

[0626] 7) Combined inter-intra prediction mode

[0627] The combined inter-intra prediction mode may be a mode in which a prediction sample of a target block is derived using a weighted sum of a prediction sample generated via inter prediction and a prediction sample generated via intra prediction.

[0628] In the above-mentioned mode, the decoding device 200 may autonomously correct the derived motion information. For example, the decoding device 200 may search for motion information having a minimum sum of absolute differences (SAD) in a specific area based on a reference block indicated by the derived motion information, and may derive the found motion information as the corrected motion information.

[0629] In the above mode, the decoding apparatus 200 may use the optical flow to compensate for the prediction samples derived through the inter-frame prediction.

[0630] In the above-mentioned AMVP mode, merge mode, skip mode, etc., motion information to be used for prediction of a target block may be specified among a plurality of pieces of motion information in the list using index information of the list.

[0631] In order to improve encoding efficiency, the encoding apparatus 100 may signal only the index of the element that causes the minimum cost in inter prediction of the target block among the elements in the list. The encoding apparatus 100 may encode the index and may signal the encoded index.

[0632] Therefore, the above lists (i.e., the predicted motion vector candidate list and the merge candidate list) must be able to be derived by the encoding device 100 and the decoding device 200 using the same scheme based on the same data. Here, the same data may include a reconstructed picture and a reconstructed block. In addition, in order to specify an element using an index, the order of the elements in the list must be fixed.

[0633] Fig.10 Spatial candidates according to an embodiment are shown.

[0634] exist Fig.10 , the positions of the spatial candidates are shown.

[0635] The large block in the center of the figure may represent the target block, and the five small blocks may represent spatial candidates.

[0636] The coordinates of the target block may be (xP, yP), and the size of the target block may be represented by (nPSW, nPSH).

[0637] Space Candidate A 0 It can be the block adjacent to the lower left corner of the target block. 0 It may be a block occupying pixels located at coordinates (xP-1, yP+nPSH).

[0638] Space Candidate A 1 It can be the block adjacent to the left side of the target block. 1 It can be the lowest block among the blocks adjacent to the left side of the target block. 1 Can be with A 0 The top adjacent block of A. 1 It may be a block occupying pixels located at coordinates (xP-1, yP+nPSH-1).

[0639] Space Candidate B 0 It can be the block adjacent to the upper right corner of the target block. 0 It may be a block occupying pixels located at coordinates (xP+nPSW,yP-1).

[0640] Space Candidate B 1 Can be a block adjacent to the top of the target block. B 1 It can be the rightmost block among the blocks adjacent to the top of the target block. Optionally, B 1 Can be with B 0 The adjacent block on the left. B 1 It may be a block occupying pixels located at coordinates (xP+nPSW-1,yP-1).

[0641] Space Candidate B 2 It can be the block adjacent to the upper left corner of the target block. 2 It may be a block occupying pixels located at coordinates (xP-1, yP-1).

[0642] Determination of availability of spatial and temporal candidates

[0643] In order to include the motion information of the spatial candidate or the motion information of the temporal candidate in the list, it must be determined whether the motion information of the spatial candidate or the motion information of the temporal candidate is available.

[0644] Hereinafter, the candidate blocks may include spatial candidates and temporal candidates.

[0645] For example, the determination may be performed by sequentially applying the following steps 1) to 4) below.

[0646] Step 1) When the PU including the candidate block is outside the boundary of the picture, the availability of the candidate block may be set to “false.” The expression “availability is set to false” may have the same meaning as “set to unavailable.”

[0647] Step 2) When the PU including the candidate block is outside the boundary of the slice, the availability of the candidate block may be set to “false.” When the target block and the candidate block are located in different slices, the availability of the candidate block may be set to “false.”

[0648] Step 3) When the PU including the candidate block is outside the boundary of the tile, the availability of the candidate block may be set to “false”. When the target block and the candidate block are located in different tiles, the availability of the candidate block may be set to “false”.

[0649] Step 4) When the prediction mode of the PU including the candidate block is an intra prediction mode, the availability of the candidate block may be set to “false.” When the PU including the candidate block does not use inter prediction, the availability of the candidate block may be set to “false.”

[0650] Fig.11 An order in which motion information of spatial candidates is added to a merge list according to an embodiment is shown.

[0651] like Fig.11 As shown in FIG. , when multiple motion information of spatial candidates are added to the merge list, A can be used 1 , B 1 , B 0 , A 0 and B 2 In other words, you can follow the order of A 1 , B 1 , B 0 , A 0 and B 2 Add multiple motion information of available spatial candidates to the merge list in order.

[0652] Methods for deriving merge lists in merge mode and skip mode

[0653] As described above, the maximum number of merge candidates in the merge list may be set. The set maximum number is indicated by "N". The set number may be sent from the encoding device 100 to the decoding device 200. The slice header of the slice may include N. In other words, the maximum number of merge candidates in the merge list for the target block of the slice may be set by the slice header. For example, the value of N may be substantially 5.

[0654] A plurality of pieces of motion information (ie, merge candidates) may be added to the merge list in the order of the following steps 1) to 4).

[0655] Step 1)In the space candidate, available space candidates can be added to the merge list. Fig.11 The plurality of pieces of motion information of the available space candidate are added to the merge list in the order shown. Here, when the motion information of the available space candidate overlaps with other motion information already in the merge list, the motion information may not be added to the merge list. The operation of checking whether the corresponding motion information overlaps with other motion information in the list may be referred to as "overlap check" for short.

[0656] The maximum number of added motion information pieces may be N.

[0657] Step 2) When the number of motion information in the merge list is less than N and the temporal candidate is available, the motion information of the temporal candidate may be added to the merge list. Here, when the motion information of the available temporal candidate overlaps with other motion information already in the merge list, the motion information may not be added to the merge list.

[0658] Step 3) When the number of pieces of motion information in the merge list is less than N and the type of the target slice is 'B', combined motion information generated by combined bidirectional prediction (bi-prediction) may be added to the merge list.

[0659] The target slice may be a slice including the target block.

[0660] The combined motion information may be a combination of L0 motion information and L1 motion information. The L0 motion information may be motion information that refers only to the reference picture list L0. The L1 motion information may be motion information that refers only to the reference picture list L1.

[0661] In the merge list, there may be one or more pieces of L0 motion information. In addition, in the merge list, there may be one or more pieces of L1 motion information.

[0662] The combined motion information may include one or more pieces of combined motion information. When generating the combined motion information, the L0 motion information and the L1 motion information to be used for the generation may be predefined in one or more pieces of L0 motion information and one or more pieces of L1 motion information. The one or more pieces of combined motion information may be generated in a predefined order via a combined bidirectional prediction using a pair of different motion information in a merge list. One of the pair of different motion information may be L0 motion information, and the other of the pair may be L1 motion information.

[0663] For example, the combined motion information added with the highest priority may be a combination of L0 motion information having a merge index 0 and L1 motion information having a merge index 1. When the motion information having a merge index 0 is not L0 motion information or when the motion information having a merge index 1 is not L1 motion information, the combined motion information may be neither generated nor added. Next, the combined motion information added with the next priority may be a combination of L0 motion information having a merge index 1 and L1 motion information having a merge index 0. The subsequent detailed combination may conform to other combinations in the field of video encoding / decoding.

[0664] Here, when the combined motion information overlaps with other motion information already present in the merge list, the combined motion information may not be added to the merge list.

[0665] Step 4) When the number of pieces of motion information in the merge list is less than N, the motion information of the zero vector may be added to the merge list.

[0666] The zero-vector motion information may be motion information in which the motion vector is a zero vector.

[0667] The number of pieces of zero vector motion information may be one or more. The reference picture indexes of one or more pieces of zero vector motion information may be different from each other. For example, the value of the reference picture index of the first zero vector motion information may be 0. The value of the reference picture index of the second zero vector motion information may be 1.

[0668] The number of pieces of zero-vector motion information may be the same as the number of reference pictures in the reference picture list.

[0669] The reference direction of the zero-vector motion information may be bidirectional. Both of the motion vectors may be zero vectors. The number of pieces of zero-vector motion information may be the smaller of the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1. Optionally, when the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1 are different from each other, the reference direction as a unidirectional direction may be used for a reference picture index that may be applied only to a single reference picture list.

[0670] The encoding apparatus 100 and / or the decoding apparatus 200 may sequentially add zero-vector motion information to the merge list while changing the reference picture index.

[0671] When the zero-vector motion information overlaps with other motion information already present in the merge list, the zero-vector motion information may not be added to the merge list.

[0672] The order of the above steps 1) to 4) is merely exemplary and may be changed. In addition, some of the above steps may be omitted according to predefined conditions.

[0673] Method for deriving a candidate list of motion vector prediction in AMVP mode

[0674] The maximum number of motion vector predictor candidates in the motion vector predictor candidate list may be predefined. The predefined maximum number is indicated by N. For example, the predefined maximum number may be 2.

[0675] A plurality of pieces of motion information (ie, prediction motion vector candidates) may be added to the prediction motion vector candidate list in the order of the following steps 1) to 3).

[0676] Step 1) An available spatial candidate among the spatial candidates may be added to the prediction motion vector candidate list. The spatial candidate may include a first spatial candidate and a second spatial candidate.

[0677] The first spatial candidate may be A 0 , A 1 , scaled A 0 and scaled A 1 The second spatial candidate may be one of 0 , B 1 , B 2 , scaled B 0 , scaled B 1 and scaled B 2 one of the.

[0678] The plurality of motion information of the available spatial candidates may be added to the prediction motion vector candidate list in the order of the first spatial candidate and the second spatial candidate. In this case, when the motion information of the available spatial candidate overlaps with other motion information already in the prediction motion vector candidate list, the motion information may not be added to the prediction motion vector candidate list. In other words, when the value of N is 2, if the motion information of the second spatial candidate is the same as the motion information of the first spatial candidate, the motion information of the second spatial candidate may not be added to the prediction motion vector candidate list.

[0679] The maximum number of pieces of motion information added may be N.

[0680] Step 2) When the number of pieces of motion information in the prediction motion vector candidate list is less than N and the temporal candidate is available, the motion information of the temporal candidate may be added to the prediction motion vector candidate list. In this case, when the motion information of the available temporal candidate overlaps with other motion information already in the prediction motion vector candidate list, the motion information may not be added to the prediction motion vector candidate list.

[0681] Step 3)When the number of pieces of motion information in the motion vector predictor candidate list is less than N, zero vector motion information may be added to the motion vector predictor candidate list.

[0682] The zero-vector motion information may include one or more pieces of zero-vector motion information. Reference picture indexes of the one or more pieces of zero-vector motion information may be different from each other.

[0683] The encoding apparatus 100 and / or the decoding apparatus 200 may sequentially add a plurality of pieces of zero-vector motion information to the prediction motion vector candidate list while changing the reference picture index.

[0684] When the zero-vector motion information overlaps with other motion information already present in the motion vector predictor candidate list, the zero-vector motion information may not be added to the motion vector predictor candidate list.

[0685] The above description of the zero-vector motion information made in conjunction with the merge list can also be applied to the zero-vector motion information. The repeated description thereof will be omitted.

[0686] The order of the above steps 1) to 3) is merely exemplary and may be changed. In addition, some of the steps may be omitted according to predefined conditions.

[0687] Fig.12 Transformation and quantization processes according to examples are shown.

[0688] like Fig.12 As shown, the quantization level may be generated by performing a transform and / or quantization process on the residual signal.

[0689] The residual signal may be generated as a difference between the original block and the predicted block. Here, the predicted block may be a block generated via intra prediction or inter prediction.

[0690] The residual signal may be transformed into a signal in the frequency domain through a transform process as part of the quantization process.

[0691] The transform kernel used for the transform may include various DCT kernels such as a discrete cosine transform (DCT) type 2 (DCT-II) and a discrete sine transform (DST) kernel.

[0692] These transform kernels may perform separable transform or two-dimensional (2D) non-separable transform on the residual signal. The separable transform may be a transform indicating that a one-dimensional (1D) transform is performed on the residual signal in each of horizontal and vertical directions.

[0693] The DCT type and DST type adaptively used for 1D transform may include DCT-V, DCT-VIII, DST-I, and DST-VII in addition to DCT-II, as shown in each of the following Tables 3 and 4.

[0694] [Table 3]

[0695] Transformation Sets Transformation Candidates 0 DST-VII, DCT-VIII 1 DST-VII, DST-I 2 DST-VII, DCT-V

[0696] [Table 4]

[0697] Transformation Sets Transformation Candidates 0 DST-VII, DCT-VIII, DST-I 1 DST-VII, DST-I, DCT-VIII 2 DST-VII, DCT-V, DST-I

[0698] As shown in Tables 3 and 4, when deriving a DCT type or a DST type to be used for transformation, a transform set may be used. Each transform set may include a plurality of transform candidates. Each transform candidate may be a DCT type or a DST type.

[0699] Table 5 below shows an example of a transform set to be applied to a horizontal direction and a transform set to be applied to a vertical direction according to an intra prediction mode.

[0700] [Table 5]

[0701] Intra prediction mode 0 1 2 3 4 5 6 7 8 9 Vertical Transformation Set 2 1 0 1 0 1 0 1 0 1 Horizontal Transform Set 2 1 0 1 0 1 0 1 0 1 Intra prediction mode 10 11 12 13 14 15 16 17 18 19 Vertical Transformation Set 0 1 0 1 0 0 0 0 0 0 Horizontal Transform Set 0 1 0 1 2 2 2 2 2 2 Intra prediction mode 20 21 22 23 24 25 26 27 28 29 Vertical Transformation Set 0 0 0 1 0 1 0 1 0 1 Horizontal Transform Set 2 2 2 1 0 1 0 1 0 1 Intra prediction mode 30 31 32 33 34 35 36 37 38 39 Vertical Transformation Set 0 1 0 1 0 1 0 1 0 1 Horizontal Transform Set 0 1 0 1 0 1 0 1 0 1 Intra prediction mode 40 41 42 43 44 45 46 47 48 49 Vertical Transformation Set 0 1 0 1 0 1 2 2 2 2 Horizontal Transform Set 0 1 0 1 0 1 0 0 0 0 Intra prediction mode 50 51 52 53 54 55 56 57 58 59 Vertical Transformation Set 2 2 2 2 2 1 0 1 0 1 Horizontal Transform Set 0 0 0 0 0 1 0 1 0 1 Intra prediction mode 60 61 62 63 64 65 66 Vertical Transformation Set 0 1 0 1 0 1 0 Horizontal Transform Set 0 1 0 1 0 1 0

[0702] In Table 5, the numbers of vertical transform sets and horizontal transform sets in the horizontal direction to be applied to the residual signal according to the intra prediction mode of the target block are indicated.

[0703] As illustrated in Table 5, the transform set to be applied to the horizontal direction and the vertical direction may be predefined according to the intra prediction mode of the target block. The encoding device 100 may perform transform and inverse transform on the residual signal using the transform included in the transform set corresponding to the intra prediction mode of the target block. In addition, the decoding device 200 may perform inverse transform on the residual signal using the transform included in the transform set corresponding to the intra prediction mode of the target block.

[0704] In the transform and inverse transform, a transform set to be applied to the residual signal may be determined as illustrated in Tables 3, 4, and 5, and the transform set to be applied to the residual signal may not be signaled. The transform indication information may be signaled from the encoding apparatus 100 to the decoding apparatus 200. The transform indication information may be information indicating which one of a plurality of transform candidates included in the transform set to be applied to the residual signal is used.

[0705] For example, when the size of the target block is 64×64 or smaller, transform sets each having three transforms may be configured according to the intra prediction mode. An optimal transform method may be selected from a total of nine multi-transform methods generated by a combination of three transforms in the horizontal direction and three transforms in the vertical direction. Through such an optimal transform method, a residual signal may be encoded and / or decoded, and thus encoding efficiency may be improved.

[0706] Here, information indicating which of the transforms belonging to each transform set has been used for at least one of the vertical transform and the horizontal transform may be entropy encoded and / or decoded. Here, truncated unary binarization may be used to encode and / or decode such information.

[0707] As described above, methods using various transforms may be applied to a residual signal generated via intra prediction or inter prediction.

[0708] The transform may include at least one of a primary transform and a secondary transform. A transform coefficient may be generated by performing a primary transform on the residual signal, and a secondary transform coefficient may be generated by performing a secondary transform on the transform coefficient.

[0709] The first transform may be referred to as a “primary transform.” Furthermore, the first transform may also be referred to as an “adaptive multi-transform (AMT) scheme.” AMT may mean applying different transforms to each 1D direction (ie, vertical and horizontal directions) as described above.

[0710] The secondary transform may be a transform for improving the energy concentration on the transform coefficients generated by the primary transform. Similar to the primary transform, the secondary transform may be a separable transform or a non-separable transform. Such a non-separable transform may be a non-separable secondary transform (NSST).

[0711] The first transformation may be performed using at least one of a plurality of predefined transformation methods, for example, the plurality of predefined transformation methods may include discrete cosine transform (DCT), discrete sine transform (DST), Karhunen-Loeve transform (KLT), etc.

[0712] Furthermore, the first transform may be a transform having various transform types according to a kernel function defining a discrete cosine transform (DCT) or a discrete sine transform (DST).

[0713] For example, the transform type may be determined based on at least one of the following items: 1) a prediction mode of the target block (e.g., one of intra-frame prediction and inter-frame prediction), 2) a size of the target block, 3) a shape of the target block, 4) an intra-frame prediction mode of the target block, 5) a component of the target block (e.g., one of a luminance component and a chrominance component), and 6) a partition type applied to the target block (e.g., one of a quadtree, a binary tree, and a ternary tree).

[0714] For example, according to the transform kernel presented in Table 6 below, the first transform may include transforms such as DCT-2, DCT-5, DCT-7, DST-7, DST-1, DST-8, and DCT-8. In Table 6 below, various transform types and transform kernel functions for multiple transform selection (MTS) are illustrated.

[0715] MTS may refer to the selection of a combination of one or more DCT and / or DST kernels to transform the residual signal in the horizontal and / or vertical direction.

[0716] [Table 6]

[0717]

[0718] In Table 6, i and j may be integer values ​​equal to or greater than 0 and less than or equal to N-1.

[0719] A secondary transform may be performed on transform coefficients generated by performing the primary transform.

[0720] As in the first transform, the transform set may also be defined in the secondary transform. The method for deriving and / or determining the above transform set may be applied not only to the first transform but also to the secondary transform.

[0721] The primary transformation and the secondary transformation can be determined for a specific goal.

[0722] For example, the primary transform and the secondary transform may be applied to a signal component corresponding to one or more of a luminance (luma) component and a chrominance (chroma) component. Whether to apply the primary transform and / or the secondary transform may be determined based on at least one of the encoding parameters for the target block and / or the neighboring block. For example, whether to apply the primary transform and / or the secondary transform may be determined based on the size and / or shape of the target block.

[0723] In the encoding apparatus 100 and the decoding apparatus 200 , transform information indicating a transform method to be used for a target may be derived by using the designation information.

[0724] For example, the transform information may include a transform index to be used for the primary transform and / or the secondary transform. Alternatively, the transform information may indicate that the primary transform and / or the secondary transform is not to be used.

[0725] For example, when the target of the primary transform and the secondary transform is a target block, the (one or more) transform methods to be applied to the primary transform and / or the secondary transform indicated by the transform information may be determined based on at least one of the encoding parameters of the target block and / or a block adjacent to the target block.

[0726] Alternatively, transform information indicating a transform method for a specific target may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 .

[0727] For example, for a single CU, whether to use a primary transform, an index indicating the primary transform, whether to use a secondary transform, and an index indicating the secondary transform may be derived as transform information by the decoding device 200. Alternatively, for a single CU, transform information indicating whether to use a primary transform, an index indicating the primary transform, whether to use a secondary transform, and an index indicating the secondary transform may be transmitted by a signal.

[0728] The quantized transform coefficient (ie, the quantization level) may be generated by performing quantization on a result generated by performing the primary transform and / or the secondary transform, or by performing quantization on a residual signal.

[0729] Fig.13 A diagonal scan according to an example is shown.

[0730] Fig.14 A horizontal scan according to an example is shown.

[0731] Fig.15 A vertical scan according to an example is shown.

[0732] The quantized transform coefficient may be scanned via at least one of (upper right) diagonal scanning, vertical scanning, and horizontal scanning according to at least one of an intra prediction mode, a block size, and a block shape. The block may be a transform unit (TU).

[0733] Each scan may be initiated at a specific starting point and may be terminated at a specific ending point.

[0734] For example, by using Fig.13 The coefficients of the block are scanned by diagonal scanning, and the quantized transform coefficients can be changed into a 1D vector form. Optionally, the quantized transform coefficients can be used according to the size of the block and / or the intra prediction mode. Fig.14 Horizontal scan or Fig.15 The image is scanned vertically instead of diagonally.

[0735] Vertical scanning may be an operation of scanning 2D block coefficients in a column direction. Horizontal scanning may be an operation of scanning 2D block coefficients in a row direction.

[0736] In other words, which of diagonal scanning, vertical scanning, and horizontal scanning to use may be determined according to the size of a block and / or an inter prediction mode.

[0737] like Fig.13 , Fig.14 and Fig.15 As shown, the quantized transform coefficients may be scanned along a diagonal direction, a horizontal direction, or a vertical direction.

[0738] The quantized transform coefficients may be represented by a block shape. Each block may include a plurality of sub-blocks. Each sub-block may be defined according to a minimum block size or a minimum block shape.

[0739] In scanning, a scanning order according to a type or direction of scanning may be mainly applied to a subblock. In addition, a scanning sequence according to a direction of scanning may be applied to a quantized transform coefficient in each subblock.

[0740] For example, Fig.13 , Fig.14 and Fig.15 As shown, when the size of the target block is 8×8, the quantized transform coefficients can be generated by first transforming, second transforming and quantizing the residual signal of the target block. Therefore, one of the three types of scanning sequences can be applied to the four 4×4 sub-blocks, and the quantized transform coefficients can also be scanned for each 4×4 sub-block according to the scanning sequence.

[0741] The encoding apparatus 100 may generate entropy-coded quantized transform coefficients by performing entropy encoding on the scanned quantized transform coefficients, and may generate a bitstream including the entropy-coded quantized transform coefficients.

[0742] The decoding apparatus 200 may extract entropy-encoded quantized transform coefficients from a bitstream, and may generate quantized transform coefficients by performing entropy decoding on the entropy-encoded quantized transform coefficients. The quantized transform coefficients may be aligned in the form of 2D blocks via inverse scanning. Here, as a method of inverse scanning, at least one of upper right diagonal scanning, vertical scanning, and horizontal scanning may be performed.

[0743] In the decoding apparatus 200, inverse quantization may be performed on the quantized transform coefficient. A secondary inverse transform may be performed on a result generated by performing the inverse quantization according to whether the secondary inverse transform is performed. In addition, a primary inverse transform may be performed on a result generated by performing the secondary inverse transform according to whether the primary inverse transform is to be performed. A reconstructed residual signal may be generated by performing the primary inverse transform on a result generated by performing the secondary inverse transform.

[0744] For luma components reconstructed via intra prediction or inter prediction, inverse mapping with dynamic range may be performed before in-loop filtering.

[0745] The dynamic range may be divided into 16 equal segments and the mapping function for each segment may be signaled.Such a mapping function may be signaled at slice level or tile group level.

[0746] An inverse mapping function for performing inverse mapping may be derived based on the mapping function.

[0747] In-loop filtering, storage of reference pictures, and motion compensation may be performed in the inverse mapping area.

[0748] The prediction block generated via inter prediction can be changed to a mapping region by mapping using a mapping function, and the changed prediction block can be used to generate a reconstructed block. However, since intra prediction is performed in the mapping region, the prediction block generated via intra prediction can be used to generate a reconstructed block without mapping and / or inverse mapping.

[0749] For example, when the target block is a residual block of a chroma component, the residual block may be changed into an inverse mapping area by scaling the chroma component of the mapping area.

[0750] Whether scaling is available can be signaled at the slice level or tile group level.

[0751] For example, scaling may be applied only if a mapping is available for luma components and the partitions of the luma components and the partitions of the chroma components follow the same tree structure.

[0752] Scaling may be performed based on an average value of the values ​​of samples in a luma prediction block corresponding to a chroma prediction block. Here, when a target block uses inter prediction, the luma prediction block may mean a mapped luma prediction block.

[0753] The value required for scaling may be derived by referring to the lookup table using the index of the segment to which the average value of the sample values ​​of the luma prediction block belongs.

[0754] The residual block may be changed to the inverse mapping region by scaling the residual block using the finally derived value. Thereafter, for the block of the chroma component, reconstruction, intra prediction, inter prediction, in-loop filtering, and storage of reference pictures may be performed in the inverse mapping region.

[0755] For example, information indicating whether mapping and / or inverse mapping of luma components and chroma components is available may be signaled through a sequence parameter set.

[0756] A prediction block for a target block may be generated based on a block vector. The block vector may indicate a displacement between the target block and a reference block. The reference block may be a block in the target image.

[0757] In this manner, a prediction mode that generates a prediction block by referring to a target image may be referred to as an 'intra block copy (IBC) mode'.

[0758] The IBC mode may be applied to a CU having a specific size. For example, the IBC mode may be applied to an M×NCU. Here, M and N may be less than or equal to 64.

[0759] The IBC mode may include a skip mode, a merge mode, an AMVP mode, etc. In the case of the skip mode or the merge mode, a merge candidate list may be configured, and a merge index may be signaled, and thus a single merge candidate may be specified among the merge candidates present in the merge candidate list. The block vector of the specified merge candidate may be used as the block vector of the target block.

[0760] In the case of AMVP mode, a differential block vector may be transmitted by signal. In addition, a prediction block vector may be derived from the left neighboring block and the upper neighboring block of the target block. In addition, an index indicating which neighboring block will be used may be transmitted by signal.

[0761] The prediction block in the IBC mode may be included in the target CTU or the left CTU and may be limited to blocks within the previously reconstructed area. For example, the value of the block vector may be limited so that the prediction block of the target block is located in a specific area. The specific area may be an area defined by three 64×64 blocks encoded and / or decoded before the 64×64 block including the target block. The value of the block vector is limited in this way, and thus the memory consumption and device complexity caused by the implementation of the IBC mode may be reduced.

[0762] Fig.16 is a configuration diagram of an encoding device according to an embodiment.

[0763] The encoding device 1600 may correspond to the above-described encoding device 100 .

[0764] The encoding apparatus 1600 may include a processing unit 1610, a memory 1630, a user interface (UI) input device 1650, a UI output device 1660, and a storage device 1640, which communicate with each other through a bus 1690. The encoding apparatus 1600 may further include a communication unit 1620 coupled to a network 1699.

[0765] The processing unit 1610 may be a central processing unit (CPU) or a semiconductor device for executing processing instructions stored in the memory 1630 or the storage device 1640. The processing unit 1610 may be at least one hardware processor.

[0766] The processing unit 1610 may generate and process a signal, data, or information input to, output from, or used in the encoding device 1600, and may perform checks, comparisons, determinations, etc. related to the signal, data, or information. In other words, in an embodiment, generation and processing of data or information and checks, comparisons, and determinations related to data or information may be performed by the processing unit 1610.

[0767] The processing unit 1610 may include an inter-frame prediction unit 110, an intra-frame prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, a quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transform unit 170, an adder 175, a filter unit 180 and a reference picture buffer 190.

[0768] At least some of the inter prediction unit 110, the intra prediction unit 120, the switch 115, the subtractor 125, the transform unit 130, the quantization unit 140, the entropy encoding unit 150, the inverse quantization unit 160, the inverse transform unit 170, the adder 175, the filter unit 180, and the reference picture buffer 190 may be program modules and may communicate with an external device or system. The program module may be included in the encoding apparatus 1600 in the form of an operating system, an application program module, or other program modules.

[0769] The program modules may be physically stored in various types of known storage devices. In addition, at least some of the program modules may also be stored in a remote storage device capable of communicating with the encoding device 1600.

[0770] The program modules may include, but are not limited to, routines, subroutines, programs, objects, components, and data structures for performing functions or operations according to the embodiments or for implementing abstract data types according to the embodiments.

[0771] The program module may be implemented using instructions or codes executed by at least one processor of the encoding device 1600 .

[0772] The processing unit 1610 can execute instructions or codes in the inter-frame prediction unit 110, the intra-frame prediction unit 120, the switch 115, the subtractor 125, the transform unit 130, the quantization unit 140, the entropy encoding unit 150, the inverse quantization unit 160, the inverse transform unit 170, the adder 175, the filter unit 180 and the reference picture buffer 190.

[0773] The storage unit may represent the memory 1630 and / or the storage device 1640. Each of the memory 1630 and the storage device 1640 may be any of various types of volatile or non-volatile storage media. For example, the memory 1630 may include at least one of a read-only memory (ROM) 1631 and a random access memory (RAM) 1632.

[0774] The storage unit may store data or information used for the operation of the encoding apparatus 1600. In an embodiment, data or information of the encoding apparatus 1600 may be stored in the storage unit.

[0775] For example, the storage unit may store pictures, blocks, lists, motion information, inter-frame prediction information, bitstreams, and the like.

[0776] The encoding device 1600 may be implemented in a computer system including a computer-readable storage medium.

[0777] The storage medium may store at least one module required for the operation of the encoding apparatus 1600. The memory 1630 may store at least one module, and may be configured such that the at least one module is executed by the processing unit 1610.

[0778] Functions related to communication of data or information of the encoding device 1600 may be performed through the communication unit 1620 .

[0779] For example, the communication unit 1620 may transmit a bit stream to the decoding apparatus 1600 which will be described later.

[0780] Fig.17 is a configuration diagram of a decoding device according to an embodiment.

[0781] The decoding device 1700 may correspond to the above-mentioned decoding device 200 .

[0782] The decoding apparatus 1700 may include a processing unit 1710, a memory 1730, a user interface (UI) input device 1750, a UI output device 1760, and a storage device 1740, which communicate with each other through a bus 1790. The decoding apparatus 1700 may also include a communication unit 1720 coupled to a network 1799.

[0783] The processing unit 1710 may be a central processing unit (CPU) or a semiconductor device for executing processing instructions stored in the memory 1730 or the storage device 1740. The processing unit 1710 may be at least one hardware processor.

[0784] The processing unit 1710 may generate and process a signal, data, or information input to, output from, or used in the decoding device 1700, and may perform checks, comparisons, determinations, etc. related to the signal, data, or information. In other words, in an embodiment, generation and processing of data or information and checks, comparisons, and determinations related to data or information may be performed by the processing unit 1710.

[0785] The processing unit 1710 may include an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , an inter prediction unit 250 , a switch 245 , an adder 255 , a filter unit 260 , and a reference picture buffer 270 .

[0786] At least some of the entropy decoding unit 210, the inverse quantization unit 220, the inverse transform unit 230, the intra prediction unit 240, the inter prediction unit 250, the adder 255, the switch 245, the filter unit 260, and the reference picture buffer 270 of the decoding device 200 may be program modules and may communicate with an external device or system. The program module may be included in the decoding device 1700 in the form of an operating system, an application program module, or other program modules.

[0787] The program modules may be physically stored in various types of known storage devices. In addition, at least some of the program modules may also be stored in a remote storage device capable of communicating with the decoding apparatus 1700.

[0788] The program modules may include, but are not limited to, routines, subroutines, programs, objects, components, and data structures for performing functions or operations according to the embodiments or for implementing abstract data types according to the embodiments.

[0789] The program module may be implemented using instructions or codes executed by at least one processor of the decoding device 1700 .

[0790] The processing unit 1710 may execute instructions or codes in the entropy decoding unit 210 , the inverse quantization unit 220 , the inverse transform unit 230 , the intra prediction unit 240 , the inter prediction unit 250 , the switch 245 , the adder 255 , the filter unit 260 , and the reference picture buffer 270 .

[0791] The storage unit may represent the memory 1730 and / or the storage device 1740. Each of the memory 1730 and the storage device 1740 may be any of various types of volatile storage media or non-volatile storage media. For example, the memory 1730 may include at least one of the ROM 1731 and the RAM 1732.

[0792] The storage unit may store data or information used for the operation of the decoding device 1700. In an embodiment, data or information of the decoding device 1700 may be stored in the storage unit.

[0793] For example, the storage unit may store pictures, blocks, lists, motion information, inter-frame prediction information, bitstreams, and the like.

[0794] The decoding device 1700 may be implemented in a computer system including a computer-readable storage medium.

[0795] The storage medium may store at least one module required for the operation of the decoding device 1700. The memory 1730 may store at least one module, and may be configured such that the at least one module is executed by the processing unit 1710.

[0796] Functions related to communication of data or information of the decoding device 1700 may be performed through the communication unit 1720 .

[0797] For example, the communication unit 1720 may receive a bitstream from the encoding apparatus 1700 .

[0798] Hereinafter, the processing unit may represent the processing unit 1610 of the encoding device 1600 and / or the processing unit 1710 of the decoding device 1700. For example, with respect to a function related to prediction, the processing unit may represent the switch 115 and / or the switch 245. With respect to a function related to inter-prediction, the processing unit may represent the inter-prediction unit 110, the subtractor 125, and the adder 175, and may represent the inter-prediction unit 250 and the adder 255. With respect to a function related to intra-prediction, the processing unit may represent the intra-prediction unit 120, the subtractor 125, and the adder 175, and may represent the intra-prediction unit 240 and the adder 255. With respect to a function related to transform, the processing unit may represent the transform unit 130 and the inverse transform unit 170, and may represent the inverse transform unit 230. With respect to a function related to quantization, the processing unit may represent the quantization unit 140 and the inverse quantization unit 160, and may indicate the inverse quantization unit 220. Regarding functions related to entropy encoding and / or entropy decoding, the processing unit may indicate the entropy encoding unit 150 and / or the entropy decoding unit 210. Regarding functions related to filtering, the processing unit may indicate the filter unit 180 and / or the filter unit 260. Regarding functions related to reference pictures, the processing unit may indicate the reference picture buffer 190 and / or the reference picture buffer 270.

[0799] The present disclosure generally relates to methods and apparatus for encoding / decoding using intra block copying.

[0800] Many applications are commonly used in daily life, including remote desktop, remote gaming, wireless display, automotive infotainment, and cloud computing. The video content in these applications often includes natural scenes, text, and computer-generated graphics. Repeating patterns (such as letters, icons, and plus and minus signs) often appear in text and computer-generated graphics.

[0801] Intra-block copying (IBC) enables video encoders and video decoders to remove repetitive patterns and improve intra-picture coding efficiency. According to the intra-block copying technique, video encoders and decoders use previously encoded video data blocks belonging to the same picture as the current block of video data (to be encoded) to predict the current block.

[0802] Fig.18 A method for encoding a block of video data using intra block copying according to an embodiment of the present disclosure is shown. Fig.18 The method shown in can be used by Figure 1The video encoding device is used to perform the video encoding.

[0803] The video encoder may determine the encoding mode (or prediction mode) of the current block as the intra block copy mode. In other words, the video encoder may determine to encode and decode the current block in the intra block copy mode.

[0804] Reference Fig.18 , the video encoder may derive a block vector for intra block copy of the current block S1810. For example, the video encoder may find a block that is most similar to the current block in an area that has been encoded and decoded in the current picture, and derive a block vector based on the most similar block and the current block. The block vector may indicate the relative position of the most similar block to the current block. The most similar block may be used as a reference block.

[0805] The video encoder may generate a prediction sample (or prediction block) of the current block based on the reconstructed sample in the current picture indicated by the block vector S1820. For example, the encoding device may generate the prediction sample (or prediction block) by using the reconstructed sample (or reconstructed block) in the current picture as a reference sample (or reference block). The reconstructed sample may represent a pre-decoded sample or a reconstructed sample in the current picture, and the block vector may determine a relative position to the current block.

[0806] The video encoder may derive residual samples (or residual blocks) of the current block based on the prediction samples S1830. For example, the video encoder may derive residual samples (or residual blocks) for the current block based on the original samples and the prediction samples of the current block. In addition, the video encoder may generate reconstructed samples (or reconstructed blocks) by adding the residual samples (or residual blocks) to the prediction samples (or prediction blocks) S1840.

[0807] The video encoder may entropy encode encoding information related to the current block S1850. For example, the encoding information may include information about an encoding mode (or prediction mode) of the current block, and may also include information about residual samples.

[0808] Fig.19 A method for decoding a block of video data using intra block copying according to an embodiment of the present disclosure is shown. Fig.19 The method shown in can be used by Figure 2 The video decoding device is used to perform the video decoding.

[0809] Reference Fig.19 The video decoder may entropy decode the encoding information related to the current block S1910. For example, the encoding information may include information about the encoding mode (or prediction mode) of the current block, and may also include information about residual samples.

[0810] The video decoder may determine the encoding mode (or prediction mode) of the current block as the intra block copy mode based on the encoding information S1920. In other words, the video decoder may determine that the current block is encoded in the intra block copy mode, and therefore, decode the current block in the intra block copy mode.

[0811] The video decoder may derive a block vector of the current block based on the encoding information S1930.

[0812] The video decoder may generate predicted samples (or predicted blocks) of the current block based on previously decoded samples or reconstructed samples (or reference blocks) in the current picture S1940. The block vector may determine the relative position of the reference block to the current block.

[0813] The video decoder may derive residual samples (or residual blocks) for the current block based on the encoding information S1950.

[0814] The video decoder may generate a reconstructed sample (or a reconstructed block) of the current block based on the prediction sample (or the prediction block) and the residual sample (or the residual block) S1960.

[0815] The present disclosure provides methods for improving encoding and decoding processes using intra block copying (IBC). For example, the present disclosure provides methods for using various resolutions of block vectors for encoding and decoding processes using intra block copying. In addition, the present invention provides methods for efficiently using intra block copying techniques for luma components and chroma components. Some techniques relate to methods for deriving block vectors for chroma component blocks from block vectors for luma component blocks, while other techniques relate to methods for minimizing the coding information associated with IBC for residual blocks of both chroma components and luma components.

[0816] Blocks of a picture may be encoded and decoded using intra prediction, inter prediction, or intra block copy mode. For example, a given block within a picture may be encoded / decoded using one of three modes: intra prediction mode, inter prediction mode, and intra block copy mode.

[0817] Intra-block copying may be used in at least one of the following two cases: a case where the luminance component and the chrominance component have the same block partition structure (i.e., a single tree structure) and a case where the luminance component and the chrominance component have separate block partition structures (i.e., a dual tree structure).

[0818] In the intra block copy prediction mode, a prediction block for a target block to be encoded or decoded is derived from a previously encoded / decoded region in the same picture to which the target block belongs (i.e., within the picture). In this case, the same picture may refer to the current picture. The prediction block of the target block may be generated based on a block vector. A block vector may represent a displacement between a target block and a reference block. A reference block may be a block within a target image. A block vector may also be referred to as an intra block vector. The previously encoded / decoded region may be a region within a reconstructed image or a decoded image of the current picture. Here, a region within a reconstructed image may refer to a reconstructed region, and a region within a decoded image may refer to a decoded region. Here, a previously encoded / decoded region in the current picture may be a reconstructed region in the current picture to which at least one of chroma scaling (which is in-loop filtering), luminance mapping, deblocking filtering, adaptive sample offset, and adaptive in-loop filtering has not been performed. In addition, a previously encoded / decoded region in the current picture is a reconstructed / decoded region in the current picture to which at least one of chroma scaling (which is in-loop filtering), luminance mapping, deblocking filtering, adaptive sample offset, and adaptive in-loop filtering has been performed.

[0819] When the current target block to be encoded / decoded (i.e., the current block) is encoded / decoded in the intra block copy mode and the derived block vector is (x, y), a reference block having the same size as the current block within a previously encoded / decoded region and spaced apart from the current block by x samples in the horizontal direction and by y samples in the vertical direction may be used as a prediction block of the current block.

[0820] Specifically, if x is a positive integer, the reference block is located at x samples to the right of the current block in the horizontal direction; if x is a negative integer, the reference block is located at -x samples to the left of the current block in the horizontal direction. If y is a positive integer, the reference block is located at y samples below the current block in the vertical direction; if y is a negative integer, the reference block is located at -y samples above the current block in the vertical direction.

[0821] Fig. 20 exemplarily shows the positions of the current block and the predicted block. Fig. 20 In the example of , when both x and y are negative integers and the position of the upper left sample of the current block is (x0, y0), the position of the upper left sample of the prediction block for the current block indicated by the block vector (x, y) is given by (x0+x, y0+y). Here, the prediction block of the current block may refer to a reference block corresponding to the current block.

[0822] Here, the sample point shift positions according to the positive and negative signs may be opposite to each other. For example, if x is a positive integer, the block vector (x, y) may indicate an area separated by x samples in the left horizontal direction; if x is a negative integer, the block vector may indicate an area separated by -x samples in the right horizontal direction. In addition, if y is a positive integer, the block vector (x, y) may indicate an area separated by y samples in the upward horizontal direction; if y is a negative integer, the block vector (x, y) may indicate an area separated by -y samples in the downward horizontal direction.

[0823] The size of the current block and the size of the reference block may be different from each other. For example, the video encoder may reduce the size of the current block by performing downsampling or subsampling on the current block, determine the reference block, perform upsampling or interpolation on the determined reference block, and use the upsampled block or the interpolated block as a prediction block of the current block. At least one of the size of the current block and the size of the reference block may be determined according to at least one of the encoding parameters of the current block / CTB / CTU.

[0824] Intra-block copy detailed mode

[0825] When the luminance component block uses prediction using the intra block copy mode, the luminance component block may be encoded / decoded using one of the following methods.

[0826] i) Intra-block copy skip mode—In this mode, the encoder and decoder derive the block vector of the current block from the block vector of the block encoded / decoded before the current block, as in the skip mode of the inter-prediction mode, and do not entropy encode / decode the residual block.

[0827] ii) Intra-block copy merge mode—In this mode, the encoder and decoder derive the block vector of the current block from the block vectors of the neighboring blocks encoded / decoded before the current block, and entropy encode / decode the residual block, just like in the merge mode of the inter-prediction mode.

[0828] iii) Intra Block Copy AMVP mode—In this mode, the encoder and decoder encode / decode the motion vector difference (MVD) of the block vector as in the Advanced Motion Vector Prediction (AMVP) mode of the Inter prediction mode.

[0829] iv) Intra-block copy AMVR mode - In this mode, the encoder and decoder encode / decode the MVD of the block vector at one resolution adaptively selected from multiple resolutions, as in the AMVR mode of the inter-frame prediction mode. The intra-block copy AMVR mode is a secondary mode and can be used with other modes such as the intra-block copy AMVP mode. For example, the intra-block copy AMVR mode can presuppose the use of the intra-block copy AMVP mode.

[0830] v) Multi-hypothesis intra block copy mode - In this mode, the encoder and decoder use at least one or more block vectors or reference blocks, and use the weighted sum of the sample values ​​in at least one or more reference blocks as the prediction block of the current block. Here, a statistical value can be used instead of the weighted sum.

[0831] Information indicating the adoption of at least one of the intra-block copy skip mode, the intra-block copy merge mode, the intra-block copy AMVP mode, and the multi-hypothesis intra-block copy mode may be entropy encoded / decoded based on at least one of the encoding parameters of the current block / CTB / CTU and a neighboring block / CTB / CTU adjacent to the current block / CTB / CTU.

[0832] The coding mode of the current luma component block in the video encoder and the video decoder may be derived as follows.

[0833] In order to determine the encoding mode of the current luminance component block, at least one or more of the following encoding information may be used, and at least one or more of the following encoding information may be entropy encoded / decoded.

[0834] i) Information indicating a skip mode of a luma component block (eg, a skip mode identifier, a flag, an index, skip_flag, or cu_skip_flag).

[0835] When the skip mode information has a specific value, the skip mode information may indicate the skip mode. For example, when the corresponding identifier, flag, or index has a first value of 1, it may indicate the skip mode; when the corresponding identifier, flag, or index has a second value of 0, the skip mode information may indicate that the current mode is not the skip mode.

[0836] ii) Prediction mode information (eg, index, flag or identifier) ​​of the luma component block.

[0837] The prediction mode information may indicate one of a plurality of prediction modes including an intra prediction mode, an inter prediction mode, and an intra block copy mode. For example, when the syntax element representing the prediction mode information has a first value of 0, the prediction mode information may indicate the intra prediction mode; when the syntax element has a second value of 1, the inter prediction mode is indicated; and when the syntax element has a third value of 2, the intra block copy mode may be indicated.

[0838] In another example, the first prediction mode information (e.g., an index, a flag, an identifier, or pred_mode_flag) may indicate an intra-frame prediction mode. When the first prediction mode information has a first value of 1, it may indicate that the intra-frame prediction mode is used; when the first prediction mode information has a second value of 0, it may indicate that the intra-frame prediction mode is not used. When it is indicated that the intra-frame prediction mode is not used, the second prediction mode information (e.g., an index, a flag, an identifier, or pred_mode_ibc_flag) may be entropy encoded / decoded to indicate whether the inter-frame prediction mode or the intra-frame block copy mode is used. When the second prediction mode information has a first value of 1, it may indicate that the intra-frame block copy mode is adopted; and when the second prediction mode information has a second value of 0, it may indicate that the inter-frame prediction mode is adopted.

[0839] In another example, the first prediction mode information (e.g., an index, a flag, an identifier, or pred_mode_flag) may indicate whether the intra prediction mode or the inter prediction mode is adopted. When the first prediction mode information has a first value of 1, it may indicate that the intra prediction mode is adopted; when the first prediction mode information has a second value of 0, it may indicate that the inter prediction mode is adopted. In addition, the second prediction mode information (e.g., an index, a flag, an identifier, or pred_mode_ibc_flag) may be entropy encoded / decoded or derived; when the second prediction mode information has a first value of 1, it may be determined that the intra block copy mode is adopted; and when the second prediction mode information has a second value of 0, it may be determined that the prediction mode of the corresponding luminance component block may be determined as the intra prediction mode or the inter prediction mode determined by the first prediction mode information.

[0840] iii) Information indicating a merge mode of a luminance component block (e.g., a merge mode identifier, a flag, an index, or merge_flag). When the current luminance component block is not in skip mode but in intra block copy mode, the merge mode may be indicated when the information indicating the merge mode has a specific value. For example, an identifier, a flag, or an index as the information indicating the merge mode has a first value of 1, which may indicate the merge mode; and when the corresponding identifier, flag, or index has a second value of 0, it may indicate that the merge mode is not adopted.

[0841] The encoding mode of the current luma component block may be derived according to at least one of encoding parameters of the current block / CTB / CTU and a neighboring block / CTB / CTU adjacent to the current block / CTB / CTU.

[0842] In the above embodiment and / or other embodiments of the present disclosure, the first value and the second value may be different from the above values. For example, the first value may be 0, and the second value may be 1.

[0843] In the above embodiments and / or other embodiments of the present disclosure, a chroma component block may be used instead of a luminance component block. For example, a current luminance component block may be changed to a chroma component block and applied to the above embodiments and / or other embodiments of the present disclosure.

[0844] The encoding mode of the current luminance component block can be determined as follows using the above encoding information. Here, the encoding mode may mean a prediction mode. In addition, the encoding information may mean prediction mode information.

[0845] If the luma component block is in skip mode, and the sub-picture, partition, tile group, slice or tile to which the luma component block belongs belongs to type I, the encoder and the decoder may not entropy encode / decode the prediction mode information, and may determine that the corresponding block is encoded / decoded in intra block copy skip mode. This is because the prediction modes available for type I are intra prediction mode and intra block copy mode, and skip mode is not used for type I.

[0846] In addition, if the luminance component block is in skip mode, and the sub-picture, partition, tile group, slice or tile to which the luminance component block belongs is not type I, the encoder and decoder may entropy encode / decode the prediction mode information. Here, when it is determined based on the prediction mode information that the corresponding luminance component block is in intra-block copy mode, the encoder and decoder may determine that the corresponding luminance component block is encoded / decoded in intra-block copy skip mode.

[0847] In addition, when the luminance component block is not in skip mode and it is determined based on the prediction mode information that the corresponding luminance component block is in intra block copy mode, the encoder and the decoder may entropy encode / decode the information indicating the merge mode. Here, if the information indicating the merge mode indicates that the corresponding luminance component block is in merge mode, the encoder and the decoder may determine that the corresponding luminance component block is encoded / decoded in the intra block copy merge mode.

[0848] In addition, when the luminance component block is not in skip mode, the residual blocks of the luminance component block and the chrominance component block are encoded / decoded, and it is determined based on the prediction mode information that the corresponding luminance component block is in intra block copy mode, the encoder and the decoder may entropy encode / decode the information indicating the merge mode. Here, if the information indicating the merge mode indicates that the corresponding luminance component block is in merge mode, the encoder and the decoder may determine that the corresponding luminance component block is encoded / decoded in the intra block copy merge mode.

[0849] Furthermore, when the luma component block is in neither the skip mode nor the merge mode but in the intra block copy mode, the encoder and the decoder may determine that the corresponding luma component block is encoded / decoded in the intra block copy AMVP mode.

[0850] In the intra block copy mode, whether the luma component and the chroma component have the same block partition structure or have separate block partition structures may be considered.

[0851] qtbtt_dual_tree_intra_flag may mean that for an I slice, each CTU is partitioned into 64x64 coding units, and the 64x64 coding units are used as root nodes for luma and chroma components.

[0852] For example, when qtbtt_dual_tree_intra_flag has a first value (e.g., 0), it may indicate that each CTU is partitioned into 64×64 coding units, and the 64×64 coding units are not used as root nodes for luma components and chroma components; when qtbtt_dual_tree_intra_flag has a second value (e.g., 1), it may indicate that each CTU is partitioned into 64×64 coding units, and the 64×64 coding units are used as root nodes for luma components and chroma components.

[0853] When qtbtt_dual_tree_intra_flag has a first value (e.g., 0), the block partition structure of the luma component and the block partition structure of the chroma component may be the same. However, the block size of the luma component and the block size of the chroma component may be different depending on the format of the chroma component. In this case, it may be considered that a single tree structure is used. SINGLE_TREE may be used to identify a single tree type.

[0854] When the slice type is an I slice and qtbtt_dual_tree_intra_flag has a second value (e.g., 1), the block partition structure for the luma component and the block partition structure for the chroma component may be different from each other based on a 64×64 coding unit. Here, the block partition structure of the luma component and the block partition structure of the chroma component may be independent of each other. In this case, it may be considered that a dual tree structure is used. In the dual tree structure, DUAL_TREE_LUMA may be used to identify the tree type of the luma component, and DUAL_TREE_CHROMA may be used to identify the tree type of the chroma component.

[0855] In the case of a single tree structure, the minimum block size for chroma components using at least one of the intra block copy modes may be set to a 2×2 block. Here, blocks smaller than a 2×2 block may not be used for chroma components. In other words, blocks having a block size equal to or larger than a 2×2 block using at least one of the intra block copy modes may not be allowed to be partitioned into blocks smaller than a 2×2 block.

[0856] In addition, in the case of a single tree structure, the minimum block size for the chroma component using at least one of the intra block copy modes may be set to a 4×4 block. Here, 2×2 blocks, 2×4 blocks, and 4×2 blocks may not be used for chroma components. In other words, a block having a block size equal to or greater than at least one of 2×2 blocks, 2×4 blocks, and 4×2 blocks using at least one of the intra block copy modes may not be allowed to be partitioned into at least one of 2×2 blocks, 2×4 blocks, and 4×2 blocks.

[0857] In addition, in the case of a dual tree structure, the minimum block size for the chroma component using at least one of the intra block copy modes may be set to a 4×4 block. Here, 2×2 blocks, 2×4 blocks, and 4×2 blocks may not be used for chroma components. In other words, a block having a block size equal to or greater than at least one of 2×2 blocks, 2×4 blocks, and 4×2 blocks using at least one of the intra block copy modes may not be allowed to be partitioned into at least one of 2×2 blocks, 2×4 blocks, and 4×2 blocks.

[0858] In order to improve the subjective / objective quality of an image, the encoder may generate first transform coefficients by performing a first transform on a residual block, perform a second transform on the first transform coefficients, generate quantization coefficient levels by quantizing the second transform coefficients, and entropy encode the quantization coefficient levels.

[0859] The decoder may entropy decode the quantization coefficient levels, dequantize the quantization coefficient levels to generate secondary transform coefficients, perform secondary inverse transform on the secondary transform coefficients to generate primary transform coefficients, perform primary inverse transform on the primary transform coefficients, and generate a reconstructed residual block.

[0860] A secondary transform may be performed between the primary transform and quantization in the encoder, and an inverse secondary transform may be performed between inverse quantization and the primary inverse transform in the decoder. Here, the secondary transform may be referred to as a reduced secondary transform or a low frequency non-separable transform (LFNST).

[0861] When the current block uses at least one of the intra block copy modes, a secondary transform / inverse transform may be performed on the current block. Here, the secondary transform / inverse transform may be performed on at least one of the luminance component block and the chrominance component block. In addition, a transform matrix set may be determined according to at least one of the intra block copy modes of the current block. Here, when the secondary transform is performed on the current block, an entropy matrix index may be entropy encoded / decoded, wherein the transform matrix index indicates which transform matrix among the transform matrices in the transform matrix set is used for the secondary transform / inverse transform.

[0862] The encoding mode of the current chrominance component block in the encoder / decoder may be derived as follows. Here, the encoding mode may mean a prediction mode. In addition, the encoding information may indicate prediction mode information.

[0863] When the luma component and the chroma component have the same block partition structure (single tree type: SINGLE_TREE), the encoding mode may be determined as follows.

[0864] The prediction mode (intra-frame prediction mode, inter-frame prediction mode and intra-frame block copy mode) of the chrominance component block may be the same as the prediction mode of the corresponding luminance component block. In the above-mentioned embodiment and / or other embodiments of the present disclosure, the intra-frame block copy mode may indicate at least one of the intra-frame block copy skip mode, the intra-frame block copy merge mode and the intra-frame block copy AMVP mode.

[0865] Here, when the corresponding luma component block is in intra block copy skip mode, the chroma component block may not encode / decode the residual block, and the residual block information may not be transmitted by signal. Here, entropy encoding / decoding may not be performed on information (e.g., cu_cbf or tu_cbf) indicating that the corresponding residual block information is not transmitted by signal. Tu_cbf may include at least one of tu_cbf_cb and tu_cbf_cr.

[0866] In addition, when the corresponding luminance component block is in the intra block copy merge mode, the chrominance component block may not encode / decode the residual block, and the residual block information may not be transmitted by signal. Here, entropy encoding / decoding may not be performed on information (e.g., cu_cbf or tu_cbf) indicating that the corresponding residual block information is not transmitted by signal. Tu_cbf may include at least one of tu_cbf_cb and tu_cbf_cr.

[0867] When the luma component and the chroma component have separate block partition structures (dual tree type: DUAL_TREE), and the current chroma component block is in intra block copy mode (or when the luma component block corresponding to the current chroma component block is in intra block copy mode), information required for encoding / decoding of the current chroma component block may be derived from encoding information of the luma component block corresponding to the current chroma component block. Here, the luma component block corresponding to the current chroma component block may be a luma component block at a sample position corresponding to the center of the chroma component block and a luma component block at a sample position corresponding to the upper left of the chroma component block.

[0868] The encoding mode of the current chroma component block may be derived according to at least one of encoding parameters of the current chroma component block / CTB and a luma component block / CTB corresponding to the chroma component block / CTB.

[0869] When the luma component and the chroma component have separate block partition structures (i.e., tree type DUAL_TREE_LUMA or DUAL_TREE_CHROMA for a dual tree structure), the encoding mode of the chroma component block may be determined based on the encoding mode information of the chroma component block to be entropy encoded / decoded. The encoding mode of the chroma component block may include an intra prediction mode, an inter prediction mode, and an intra block copy mode in the same manner as the encoding mode of the luma component block. Here, the encoding mode may mean a prediction mode.

[0870] For example, when the syntax element representing the prediction mode information has a first value of 0, it may indicate an intra prediction mode; a second value of 1 may indicate an inter prediction mode; and a third value of 2 may indicate an intra block copy mode.

[0871] In another example, the first prediction mode information (e.g., an index, a flag, an identifier, or pred_mode_flag) may indicate an intra-frame prediction mode. When the first prediction mode information has a first value of 1, it may indicate that the intra-frame prediction mode is used; when the first prediction mode information has a second value of 0, it may indicate that the intra-frame prediction mode is not used. When it is indicated that the intra-frame prediction mode is not used, the second prediction mode information (e.g., an index, a flag, an identifier, or pred_mode_ibc_flag) may be entropy encoded / decoded to indicate whether the inter-frame prediction mode or the intra-frame block copy mode is used. When the second prediction mode information has a first value of 1, it may indicate that the intra-frame block copy mode is adopted; and when the second prediction mode information has a second value of 0, it may indicate that the inter-frame prediction mode is adopted.

[0872] In another example, the first prediction mode information (e.g., an index, a flag, an identifier, or a pred_mode_flag) may indicate whether the intra prediction mode or the inter prediction mode is adopted. When the first prediction mode information has a first value of 1, it may indicate that the intra prediction mode is adopted; when the first prediction mode information has a second value of 0, it may indicate that the inter prediction mode is adopted. In addition, the second prediction mode information (e.g., an index, a flag, an identifier, or a pred_mode_ibc_flag) may be entropy encoded / decoded or the second prediction mode information (e.g., an index, a flag, an identifier, or a pred_mode_ibc_flag) may be derived; when the second prediction mode information has a first value of 1, it may be determined that the intra block copy mode is adopted; and when the second prediction mode information has a second value of 0, it may be determined that the prediction mode of the corresponding luminance component block may be determined as the intra prediction mode or the inter prediction mode determined by the first prediction mode information.

[0873] In another example, the second prediction mode information (e.g., an index, a flag, an identifier, or a pred_mode_ibc_flag) may be transmitted or derived by a signal; when the second prediction mode information has a first value of 1, the decoder may determine that the intra block copy mode is adopted; when the second prediction mode information has a second value of 0, it may be determined that the intra prediction mode is adopted.

[0874] In yet another example, the second prediction mode information (e.g., index) may indicate one of an intra block copy mode, a plannar mode, a DC mode, a vertical mode, a horizontal mode, a direct mode (DM), and a linear mode (LM). Here, when the second prediction mode information indicates that the prediction mode of the current chroma component block is in the intra block copy mode, information (e.g., a block vector) necessary for encoding / decoding the current chroma component block may be derived from encoding information of a luminance component block corresponding to the current chroma component block.

[0875] Here, when the luma component and the chroma component have separate block partition structures, one or more luma component blocks may exist in a luma component region corresponding to a current chroma component block.

[0876] For example, the luminance component block corresponding to the current chrominance component block may be a luminance component block at a sample position corresponding to the center of the chrominance component block; alternatively, the luminance component block corresponding to the current chrominance component block may be a luminance component block at a sample position corresponding to the upper left of the chrominance component block.

[0877] In another example, the encoder and the decoder may search for a luma component block at a predefined sample position in a luma component region in a predefined order to find a luma component block encoded / decoded in an intra block copy mode. The predefined sample position may be, for example, a center (C) sample position, an upper left (TL) sample position, an upper right (TR) sample position, a lower left (BL) sample position, and a lower right (BR) sample position in the luma component region. The predefined order may be, for example, an order of center (C), upper left (TL), upper right (TR), lower left (BL), and lower right (BR). The encoder and the decoder may derive information (e.g., a block vector) necessary for encoding / decoding a current chroma component block from a block vector of a luma component block encoded / decoded in an intra block copy mode that is first encountered in the predefined order. For example, in order to derive a block vector of a current chroma component block, the block vector of the luma component block may be scaled according to the chroma component format.

[0878] Derivation of block vectors for intra block copy prediction

[0879] As part of a process of encoding a current block using an intra block copy mode, a video encoder may derive at least one block vector of the current block. Hereinafter, a method for deriving a block vector of a luma component block and a method for deriving a block vector of a chroma component block will be described.

[0880] 1) Derivation of block vector of luminance component block

[0881] A method for inducing a block vector when a current block is a luma component block and is encoded / decoded in an intra block copy skip mode or an intra block copy merge mode may be implemented as follows.

[0882] In order to derive the block vector of the luminance component block, a block vector candidate list may be constructed from block vector candidates of the luminance component block encoded / decoded before the current block, and at least one candidate among the candidates belonging to the constructed block vector candidate list may be used as the block vector of the current block. Here, at least one information for identifying a corresponding candidate from the corresponding block vector candidate list from block vector candidate information (e.g., an identifier, an index, a flag, or merge_idx) may be entropy encoded / decoded and derived based on at least one of the encoding parameters.

[0883] At this time, the block vector candidate list may consist of at least one or more elements; at least one or more block vector candidates may be used in the current block; and at least one or more pieces of block vector candidate information may be entropy encoded / decoded.

[0884] The block vector candidate list may consist of up to N candidates, where N may be a positive integer. Here, N may represent the maximum number of candidates in the block vector candidate list. N may be derived based on at least one of the coding parameters of the current block / CTB / CTU.

[0885] In addition, refer to Fig.21 At least one candidate described may be included in the block vector candidate list.

[0886] like Fig.21 As shown in the example of , a block vector may be derived from at least one of a block B1 adjacent to the top of the current block X, a block A1 adjacent to the left side of the current block, a block B0 located at the upper right corner of the current block, a block B2 located at the upper left corner of the current block, and a block A0 located at the lower left corner of the current block; and the block vector may be determined as a block vector candidate for the current block. Here, at least one of the derived block vectors may be included in the block vector candidate list. In this case, the derived block vector may be referred to as a "spatial block vector candidate" because the block vector is derived from a block vector of a neighboring block adjacent to the current block.

[0887] When deriving block vectors from all A1 blocks, B1 blocks, B0 blocks, and A0 blocks, block B2 located at the upper left corner of the current block may not be used to derive block vector candidates. In other words, the block vector of block B2 may not be included in the block vector candidate list.

[0888] In addition, at least one of the blocks at the A0 position, the A1 position, the B0 position, the B1 position, and the B2 position may be selected according to a predetermined priority to determine whether a block vector exists in the corresponding block (in other words, whether the corresponding block has been encoded / decoded using the intra block copy mode or whether the corresponding block is in the intra block copy mode); in the case where a block vector exists, the block vector of the corresponding block may be determined as a block vector candidate. Here, at least one of the determined block vectors may be included in a block vector candidate list. Here, the predetermined priority for configuring the block vector candidate list may be in the order of A1, B1, B0, A0, and B2.

[0889] When the block vector candidate list is constructed according to a predetermined priority, a redundancy check may be performed between the block vector candidates existing in the block vector candidate list and the block vector candidates newly added to the block vector candidate list. For example, if the block vector candidate newly added to the block vector candidate list overlaps with the block vector candidate existing in the block vector candidate list, the overlapping block vector candidate may not be added to the block vector candidate list.

[0890] For example, when the block vector candidate list is constructed in the order of A1, B1, B0, A0, and B2, a redundancy check may be performed on the B1 block and the A1 block, and a redundancy check may be performed on the B0 block and the B1 block. In addition, a redundancy check may be performed between the A0 block and the A1 block; and the redundancy of the B2 block may be checked for the A1 block and the B1 block. The redundancy check may be performed only when a block vector exists in the corresponding block. In another example, the redundancy of the block vector added to the block vector candidate list may be checked for all block vectors existing in the block vector candidate list.

[0891] Furthermore, assuming that a block vector exists in at least one of the blocks at position A0, position A1, position B0, position B1, and position B2; only when the block vector of the corresponding block is available for the current block, the block vector of the corresponding neighboring block may be determined as a block vector candidate. When the block vector is not available, the block vector may not be used as a block vector candidate. At this time, the availability of the block vector may be determined by the availability of the reference sample (block) at the position indicated by the corresponding block vector.

[0892] For example, if the area / position indicated by the corresponding block vector includes at least one of the samples included in the current block, the corresponding block vector may be determined to be unavailable. In another example, if the area / position indicated by the corresponding block vector includes at least one of an area / position / sample outside the boundary of a picture, a sub-picture, a slice, a tile group, a tile, or a partition, the corresponding block vector may be determined to be unavailable.

[0893] In addition, at least one of the block vectors of the blocks encoded / decoded before the current block may be stored in a buffer, and at least one of the block vectors stored in the corresponding buffer may be determined as a block vector candidate for the current block. Here, at least one of the determined block vector candidates may be included in the block vector candidate list.

[0894] Here, the block vectors may be stored in a buffer having a specific size in the order of encoding / decoding, and when the corresponding buffer becomes full, the block vector stored first is deleted, and a new block vector (i.e., a block vector of a most recently encoded / decoded block) may be stored in the buffer. Among the block vectors stored in the corresponding buffer, the priority of adding the block vectors stored in the corresponding buffer to the block vector candidate list may vary according to the order in which the block vectors are stored (e.g., according to the order of the oldest storage time or according to the order of the latest storage time). For example, the block vector last stored in the buffer may be added to the block vector candidate list first, or the block vector first stored in the buffer may be added to the block vector candidate list first. Such block vector candidates may be referred to as "history-based block vector candidates". In other words, the block vectors stored in the corresponding buffer may mean history-based block vector candidates.

[0895] The buffer including the history-based block vectors may be managed and used separately from the buffer used in the intra prediction mode.

[0896] When at least one of the history-based block vector candidates is used to construct a block vector candidate list, the corresponding history-based block vector candidate may be added to the block vector candidate list only when the corresponding history-based block vector candidate is available for the current block.

[0897] Here, the availability of the corresponding history-based block vector may be determined by the availability of the reference sample (block) at the position indicated by the corresponding block vector. For example, if the area / position indicated by the corresponding history-based block vector includes at least one of the samples included in the current block, the corresponding history-based block vector may be determined to be unavailable. In another example, if the area / position indicated by the corresponding history-based block vector includes at least one of the area / position / sample outside the boundary of a picture, a sub-picture, a slice, a tile group, a tile, or a partition, the corresponding history-based block vector may be determined to be unavailable.

[0898] When at least one of the history-based block vector candidates is used to construct a block vector candidate list, a redundancy check may be performed between the corresponding history-based block vector candidate and the block vector candidates present in the block vector candidate list; and in the case where there are no identical block vectors, the history-based block vector candidate may be added to the block vector candidate list. In another example, when at least one of the history-based block vector candidates is used to construct a block vector candidate list, a redundancy check may be performed between the corresponding history-based block vector candidate and the block vector candidate; and in the case where there are no identical block vectors, the history-based block vector candidate may be added to the block vector candidate list. In yet another example, when at least one of the history-based block vector candidates is used to construct a block vector candidate list, the corresponding history-based block vector candidate may be added to the block vector candidate list without performing a redundancy check between the corresponding history-based block vector candidate and the block vector candidates present in the block vector candidate list.

[0899] A buffer including history-based block vector candidates may be maintained during encoding / decoding in units of a picture, a slice, a sub-picture, a partition, a tile group, a tile, a CTU, a CTU row, or a CTU column, and the buffer including history-based block vector candidates may be used within a picture, a partition, a tile group, a tile, a CTU, a CTU row, or a CTU column unit.

[0900] The buffer may include at least one of encoding information of a block encoded / decoded before the current block in units of a picture, a slice, a sub-picture, a partition, a tile group, a tile, a CTU, a CTU row, or a CTU column.

[0901] In addition, when the buffer is configured in units of pictures, slices, sub-pictures, tiles, parallel tile groups, parallel tiles, CTUs, CTU rows, or CTU columns, the buffer can be initialized at the start position / region / block / cell of the picture, slice, sub-picture, tile, parallel tile group, parallel tile, CTU, CTU row, or CTU column unit. Here, when initializing the buffer, all block vectors existing in the buffer can be deleted. In addition, when initializing the buffer, all block vectors existing in the buffer can be set to a predetermined value. Here, the predetermined value can mean the values of x and y in the block vector (x, y); for example, x and y can be one of the integer values.

[0902] At least two or more block vector candidates existing in the block vector candidate list can be used to construct a combined block vector candidate. The "combined block vector candidate" can be added to the block vector candidate list. Here, the combined block vector candidate can have a statistical value for each of the x component and the y component of at least two or more block vectors among the block vector candidates existing in the block vector candidate list. Here, when constructing the combined block vector candidate, a history-based block vector candidate can be not used. Here, when constructing the combined block vector candidate, at least one of the block vector candidates of neighboring blocks adjacent to the current block can be not used. Here, the availability of the combined block vector candidate composed of the block vector candidates for the current block is checked, and the combined block vector candidate can be determined as the combined block vector candidate only when the combined block vector candidate is available. Here, the availability of the block vector can be determined by the availability of the reference sample (block) at the position indicated by the corresponding block vector.

[0903] For example, if the region / position indicated by the corresponding combined block vector candidate includes at least one sample included in the current block, the corresponding combined block vector candidate can be determined as unavailable.

[0904] For example, if the region / position indicated by the corresponding combined block vector candidate includes at least one of the regions / positions / samples outside the boundaries of the picture, sub-picture, slice, parallel tile group, parallel tile, or tile, the corresponding combined block vector candidate can be determined as unavailable.

[0905] When the width of the current luma component block is W and the height is H, (-(W << n)+a,-(H << n)+b), (-(W << n)+c,0), or (0,-(H << n)+d) can be included as block vector candidates in the block vector candidate list. Here, n is a positive integer, and a, b, c, and d can have integer values. The above block vectors can be referred to as "fixed basic block vector candidates". The fixed basic block vector candidates can be added to the block vector candidate list.

[0906] The block vector candidate list may be constructed using at least one of block vector candidates of neighboring blocks adjacent to the current block, history-based block vector candidates, combined block vector candidates, and fixed basic block vector candidates according to a predetermined priority.

[0907] For example, the order of constituting the block vector candidate list may follow the order of block vector candidates of neighboring blocks adjacent to the current block, history-based block vector candidates, combined block vector candidates, and fixed basic block vector candidates. Here, the fixed basic block vector candidates may be composed according to the order shown in Table 7, for example, until the number of candidates in the block vector candidate list reaches the maximum number of candidates in the block vector candidate list.

[0908] [Table 7]

[0909] order Basic Block Vector Candidates 1 (-(W<<1)，0) 2 (0，-(H<<1)) 3 (-(W<<1)-1，0) 4 (0，-(H<<1)-1) 5 (-(W<<1)-2，0) 6 (0，-(H<<1)-2) 7 (-(W<<1)-3，0) 8 (0，-(H<<1)-3) 9 (-(W<<1)-4，0) 10 (0，-(H<<1)-4)

[0910] In another example, the fixed basic block vector may be a (0, 0) vector; a block vector candidate list having a maximum number of candidates may be constructed by adding the fixed basic block vector to the block vector candidate list until the number of candidates in the block vector candidate list reaches the maximum number allowed by the block vector candidate list.

[0911] When constructing a block vector candidate list, the maximum number of block vector candidates of neighboring blocks adjacent to the current block that can be included in the block vector candidate list may be "maximum number of block vector candidates N" or "(Nm)". Here, N may be a positive integer, and m may be a positive integer. In addition, N may be greater than m.

[0912] When constructing a block vector candidate list, the maximum number of history-based block vector candidates that can be included in the block vector candidate list can be the maximum number of block vector candidates N or (Nm). Here, N can be a positive integer, and m can be a positive integer. In addition, N can be greater than m.

[0913] When constructing a block vector candidate list, the maximum number of combined block vector candidates that can be included in the block vector candidate list can be the maximum number of block vector candidates N or (Nm). Here, N can be a positive integer, and m can be a positive integer. In addition, N can be greater than m.

[0914] When constructing a block vector candidate list, the maximum number of fixed basic block vector candidates that can be included in the block vector candidate list can be the maximum number of block vector candidates N or (Nm). Here, N can be a positive integer, and m can be a positive integer. In addition, N can be greater than m.

[0915] The maximum number of candidates in the block vector candidate list may be a value preset in the encoder / decoder or a value signaled from the encoder to the decoder.

[0916] The block vector candidate may be derived according to at least one of the encoding parameters of the current block / CTB / CTU. The block vector candidate may be added to the block vector candidate list according to at least one of the encoding parameters of the current block / CTB / CTU.

[0917] In addition, the encoder and the decoder may partition the parent block and encode / decode each partitioned block in the intra block copy skip mode, the intra block copy merge mode, or the intra block copy AMVP mode.

[0918] For example, when at least one of the blocks partitioned from the parent block is smaller than a predetermined threshold, a block vector candidate list constructed from the parent block may be shared and used for at least one of the partitioned blocks.

[0919] At least one of the width W and the height H of the parent block or the child block may be used to determine whether to share the block vector candidate list constructed from the parent block. For example, when one of the following conditions is met, the block vector candidate list constructed from the parent block may be used for at least one of the child blocks (blocks partitioned from the parent block).

[0920] i) Quadtree partition from parent block to child block: (width of parent block × height of parent block) / 4 < threshold

[0921] ii) Binary tree partition from parent block to child block in horizontal or vertical direction: (width of parent block × height of parent block) / 2 < threshold

[0922] iii) Ternary tree partition from parent block to child block: (width of parent block × height of parent block) / 4 < threshold

[0923] Here, the threshold value may be a value pre-set in the encoder / decoder and may be a value transmitted from the encoder to the decoder using a signal. The threshold value may be a positive integer. In addition, the threshold value may be at least one of the values ​​representing the length or size of the block, such as the width of the block, the height of the block, and the product of the width and height of the block (block area). The threshold value may be determined based on at least one of the encoding parameters of the current block / CTB / CTU.

[0924] Fig. 22 A pattern showing partitioning of a parent block into sub-blocks to be encoded / decoded in intra block copy mode.

[0925] When partitioning by quadtree, vertical or horizontal binary tree, or ternary tree Fig. 22 When each parent block in the parent block shown in is partitioned into child blocks, the area of ​​at least one child block is less than 32. If the threshold in the above condition is 32, then Fig. 22 Every parent block shown in satisfies the condition.

[0926] When encoding / decoding each sub-block in intra-block copy skip mode, intra-block copy merge mode, or intra-block copy AMVP mode, the encoder and the decoder may encode / decode the sub-block by using a block vector candidate list consisting of at least one of the following items: block vector candidates of neighboring blocks A1, B1, B0, A0, and B2 adjacent to the parent block, history-based block vector candidates encoded / decoded before the parent block and stored in a buffer, combined block vector candidates, and fixed basic block vectors. Here, the fixed basic block vector may be derived from the width and height of the parent block.

[0927] When a block vector candidate list constructed from a parent block is shared and used by at least one of the subblocks, a reference block indicated by a block vector of the subblock may be restricted to not be located in the parent block.

[0928] Fig.23 A conceptual diagram showing a list of block vector candidates that share a parent block position with a child block.

[0929] like Fig.23 As shown in the example of , when the block vector candidate list at the parent block position (thick solid line) is shared and used by at least one of the sub-blocks, the block vector (BV) of the sub-block can be determined to be valid only when the area / position / sample indicated by the block vector of the block encoded / decoded in the intra block copy mode in at least one of the sub-blocks (thin solid line) indicates an area encoded / decoded before the parent block.

[0930] In other words, when the area / position / sample indicated by the block vector of the subblock includes at least one sample among the samples included in the parent block, it may be determined that the block vector of the corresponding subblock is unavailable.

[0931] When a block vector candidate list constructed from a parent block is shared and used by at least one of the subblocks, at least one of the partitioned subblocks may have an intra block copy skip mode or an intra block copy merge mode.

[0932] When a block vector candidate list constructed from a parent block is shared and used by at least one of the subblocks, at least one block among the partitioned subblocks may be encoded / decoded in an intra block copy skip mode or in an intra block copy merge mode.

[0933] When the merge candidate list constructed from the parent block is shared and used by at least one of the child blocks, the partitioned child blocks may not be encoded / decoded in the intra block copy skip mode and the intra block copy merge mode. Here, the child blocks may be encoded / decoded in the intra block copy AMVP mode; however, in this case, the block vector may be determined to be valid only when the block vector indicates an area that was encoded / decoded before the parent block. The merge candidate list may refer to a list consisting of at least one of a spatial motion vector and a temporal motion vector other than the block vector, a history-based motion vector, a combined motion vector, and a zero vector.

[0934] When the width and / or height of the current block is less than or equal to a threshold, at least one of the intra block copy skip mode and the intra block copy merge mode may not be allowed. The threshold may be a positive integer value pre-set in the encoder / decoder and a value transmitted from the encoder to the decoder using a signal.

[0935] For example, when the width and height of the current block are less than 8, at least one of the intra block copy skip mode and the intra block copy merge mode may not be allowed.

[0936] When the product of the width and height of the current block is less than or equal to a threshold condition that a merge candidate list constructed in the parent block can be used in the child block, at least one of the intra block copy skip mode and the intra block copy merge mode may not be allowed.

[0937] For example, when the threshold specifying the condition for allowing a child block to use a merge candidate list constructed from a parent block is 32, at least one of the intra block copy skip mode and the intra block copy merge mode may be allowed only when the product of the width and height of the current block is greater than 32.

[0938] On the contrary, when the product of the width and the height of the current block is less than or equal to a threshold condition that a block vector candidate list constructed from a parent block can be used in a child block, at least one of the skip mode and the merge mode may not be allowed. At least one of the skip mode and the merge mode may mean a mode related to motion compensation in which encoding / decoding is performed using motion vectors other than block vectors of spatial / temporal neighboring blocks of the current block.

[0939] For example, when the threshold specifying the condition for allowing a child block to use a block vector candidate list constructed from a parent block is 32, at least one of a skip mode and a merge mode based on a motion vector other than a block vector may be allowed only when the product of the width and the height of the current block is greater than 32.

[0940] In the above-mentioned embodiments and / or other embodiments of the present disclosure, prohibition of a specific mode may indicate that the specific mode is not used as the encoding mode of the current block.

[0941] When at least one of the blocks partitioned from the parent block is smaller than a predetermined threshold, at least one of the partitioned blocks may share and use an integrated merge candidate list constructed from the parent block using a motion vector and a block vector.

[0942] After constructing an integrated merge candidate list using at least one of motion vector candidates of neighboring blocks adjacent to the parent block, block vector candidates of neighboring blocks adjacent to the parent block, temporal motion vector candidates, history-based motion vector candidates, history-based block vector candidates, (0,0) motion vector candidates, and fixed basic block vector candidates, at least one of the child blocks may share and use the block vector candidate list constructed from the parent block.

[0943] For example, when the corresponding block is encoded / decoded in the intra block copy skip mode or the intra block copy merge mode, at least one of the candidates corresponding to the block vector (rather than the motion vector) from the integrated merge candidate list may be used to encode / decode the corresponding block. Here, when encoding / decoding is performed in the intra block copy skip mode or the intra block copy merge mode, the information for identifying the corresponding candidate from the integrated merge candidate list may indicate only the block vector candidate.

[0944] For example, when the corresponding block is encoded / decoded in skip mode or merge mode, at least one of the candidates corresponding to the motion vector (rather than the block vector) from the integrated merge candidate list may be used to encode / decode the corresponding block. Here, when encoding / decoding is performed in skip mode or merge mode, the information for identifying the corresponding candidate in the integrated merge candidate list may indicate only the motion vector candidate.

[0945] When a block vector candidate list constructed from a parent block is shared and used by at least one of the child blocks, the block vector of the child block may not be added to a buffer for deriving history-based block vector candidates.

[0946] Furthermore, when at least one of the sub-blocks does not share and use a block vector candidate list constructed from a parent block, a block vector of the sub-block may be added to a buffer for deriving history-based block vector candidates.

[0947] The above-mentioned block vector candidate list or merge candidate list includes block vector candidates (such as spatial block vector candidates, temporal block vector candidates, and history-based block vector candidates) as elements. However, the information included in the block vector candidate list is not limited to the block vector candidates, and other information of the precoding block / predecoding block used to derive the corresponding block vector candidate may be included in the block vector candidate list together with the corresponding block vector candidate. Here, the other information is information corresponding to the precoding block / predecoding block, which may include an indicator indicating the resolution of the block vector, a flag indicating whether local illumination compensation (LIC) is applied, and information about the geometric partition mode. The encoding device and the decoding device use the precoding block or predecoding block (i.e., candidate block) used to derive the block vector candidate to construct a block vector candidate list. Information related to the candidate block indicated by the merge index of the current block may be used as information for encoding / decoding of the current block. The above description means that at least one or more of a block vector corresponding to or derived from a candidate block indicated by a merge index of a current block, resolution information of the block vector, a local illumination compensation flag, and information about a geometric partitioning mode can be applied to the current block in the same manner. For example, when the block vector resolution information of the candidate block indicated by the merge index is in units of 1 / 4 samples, the block vector resolution of the current block is also expressed in units of 1 / 4 samples. When the local illumination compensation flag of the candidate block indicated by the merge index indicates application of local illumination compensation, local illumination compensation can also be applied to the current block. In another example, the current block can be geometrically partitioned ac...

Claims

1. A method for encoding video data, comprising: Determining to use intra block copying to encode chroma blocks in the current picture; identifying a previously encoded luma block using intra block copying in a luma region corresponding to the chroma block; deriving a block vector for the chrominance block based on a block vector for the previously encoded luminance block; deriving a prediction block for the chrominance block; as well as Coding information for the chrominance block is encoded in a bitstream.

2. The method according to claim 1, further comprising: determining a block vector resolution of the chroma block, The block vector resolution is integer pixel resolution or fractional pixel resolution.

3. The method according to claim 1, wherein: The block vector resolution of the chroma block is selected from a plurality of available resolutions.

4. The method according to claim 1, wherein: The block vector resolution of the chroma block is determined separately for the horizontal direction component and the vertical direction component.

5. The method according to claim 3, wherein: The step of deriving the block vector of the chroma block further comprises rounding the block vector of the previously encoded luminance block to the block vector resolution of the chroma block.

6. The method according to claim 3, wherein: The encoding information for the chroma block includes: a syntax element indicating the block vector resolution for the chroma block among the multiple available resolutions.

7. The method according to claim 1, wherein: The tree type of the chroma block is a dual tree type.

8. The method according to claim 7, wherein: The step of identifying the previously encoded luminance block comprises searching for predefined sample positions in a luminance area corresponding to the chrominance block in a predefined order until a luminance block previously encoded in an intra block copy mode is found that contains at least one of the predefined sample positions.

9. The method according to claim 7, wherein: The encoding information for the chroma block includes: a syntax element indicating an intra-frame prediction mode for the chroma block, wherein the syntax element indicates one of an intra-frame block copy mode, a planar mode, a DC mode, a vertical mode, a horizontal mode, a direct mode (DM), and a linear mode (LM).

10. The method according to claim 1, further comprising: generating a residual block for the current block based on the prediction block, The encoding information for the chrominance block further includes: residual data representing the residual block for the current block.

11. A method for decoding video data, comprising: decoding coding information for chrominance blocks from a bitstream; Determining to use intra block copying to decode the chroma block based on the encoding information; identifying a previously decoded luma block using intra block copying in a luma region corresponding to the chroma block; deriving a block vector for the chrominance block based on a block vector for the previously decoded luminance block; as well as A prediction block for the chroma block is derived based on the block vector of the chroma block.

12. The method according to claim 11, further comprising: determining a block vector resolution of the chroma block, The block vector resolution is integer pixel resolution or fractional pixel resolution.

13. The method according to claim 11, wherein: The block vector resolution of the chroma block is selected from a plurality of available resolutions.

14. The method according to claim 11, wherein: The block vector resolution of the chroma block is determined separately for the horizontal direction component and the vertical direction component.

15. The method according to claim 13, wherein: The step of deriving the block vector for the chroma block further comprises rounding the block vector of the previously encoded luminance block to the block vector resolution of the chroma block.

16. The method according to claim 13, wherein: The encoding information for the chroma block includes: a syntax element indicating the block vector resolution of the chroma block among the multiple available resolutions.

17. The method according to claim 11, wherein: The tree type of the chroma block is a dual tree type.

18. The method according to claim 17, wherein: The step of identifying the previously encoded luminance block comprises searching for predefined sample positions in a luminance area corresponding to the chrominance block in a predefined order until a luminance block previously encoded in an intra block copy mode is found that includes at least one of the predefined sample positions.

19. The method according to claim 17, wherein: The encoding information for the chroma block includes: a syntax element indicating an intra-frame prediction mode for the chroma block, wherein the syntax element indicates one of an intra-frame block copy mode, a planar mode, a DC mode, a vertical mode, a horizontal mode, a direct mode (DM), and a linear mode (LM).

20. The method according to claim 11, further comprising: generating a residual block for the current block based on residual data included in the encoding information for the chrominance block; as well as A reconstructed block for the chroma block is generated based on the residual block and the prediction block.

21. A non-transitory computer-readable storage medium storing instructions, wherein: When the instruction is executed by one or more processors, the one or more processors are instructed to perform the following operations: Determining to use intra block copying to encode chroma blocks in the current picture; identifying a previously encoded luma block using intra block copying in a luma region corresponding to the chroma block; deriving a block vector for the chrominance block based on a block vector for the previously encoded luminance block; deriving a prediction block for the chrominance block; as well as Coding information for the chrominance block is encoded in a bitstream.

22. A non-transitory computer-readable storage medium storing instructions, wherein: When the instruction is executed by one or more processors, the one or more processors are instructed to perform the following operations: decoding coding information for chrominance blocks from a bitstream; Determining to use intra block copying to decode the chroma block based on the encoding information; identifying a previously decoded luma block using intra block copying in a luma region corresponding to the chroma block; deriving a block vector for the chrominance block based on a block vector for the previously decoded luminance block; as well as A prediction block for the chroma block is derived based on the block vector of the chroma block.

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