CN110024394A - The recording medium of method and apparatus and stored bits stream to encoding/decoding image - Google Patents

Abstract

The present invention relates to a method for encoding and decoding images. The method for decoding an image may include the steps of: generating a first prediction block of the current block from motion data of the current block; determining a current lower level that can be used to generate the second prediction block among motion data of adjacent lower level blocks at least one motion data of the block; at least one second prediction block of the current subordinate block is generated by the determined at least one motion data; generated based on the weighted sum of the first prediction block of the current block and the at least one second prediction block of the current subordinate block Final prediction block.

Description

Method and apparatus for encoding/decoding image and recording medium for storing bit stream

technical field

The present invention relates to a method and apparatus for encoding/decoding an image and a recording medium storing a bitstream. More particularly, the present invention relates to a method and apparatus for encoding/decoding images using overlapping block motion compensation.

Background technique

Recently, demands for high-resolution quality images such as high-definition (HD) images or ultra-high-definition (UHD) images have increased in various application fields. However, the data volume of image data of higher resolution and quality has increased compared to conventional image data. Therefore, when the image data is transmitted by using a medium such as a conventional wired broadband network or a wireless broadband network, or when the image data is stored in a conventional storage medium, the transmission cost and the storage cost increase. In order to solve these problems that arise as the resolution and quality of image data increase, efficient image encoding/decoding techniques are required.

Image compression techniques include various techniques, including: an inter prediction technique that predicts pixel values included in the current picture from a previous or subsequent picture of the current picture; Intra prediction techniques for pixel values; entropy coding techniques that assign short codes to high-frequency values and long codes to low-frequency values; and so on. By using such an image compression technique, image data can be efficiently compressed, and the compressed image data is transmitted or stored.

A disadvantage of conventional image encoding/decoding methods and apparatuses is that the computational complexity increases during the computation of the weighted sum for motion compensation of overlapping blocks and the deriving of motion information for neighboring blocks.

SUMMARY OF THE INVENTION

technical problem

Therefore, the present invention has taken into account the above problems arising in the prior art, and an object of the present invention is to provide a method for reducing computational complexity during calculation of a weighted sum for motion compensation for overlapping blocks and deriving motion information of adjacent blocks A method and apparatus for simultaneously performing overlapping block motion compensation.

solution

In order to achieve the above objects, the present invention provides a method for decoding an image, the method comprising: generating a first prediction block of the current block using motion information of the current block; at least one adjacent sub-block of the current sub-block Determine the motion information that can be used to generate the second prediction block from the motion information of the current sub-block; use the determined motion information to generate at least one second prediction block of the current sub-block; A weighted sum of the at least one second prediction block is used to generate a final prediction block.

In the image decoding method, in the step of determining motion information that can be used to generate the second prediction block, it may be determined based on at least one of the size and direction of motion vectors of neighboring sub-blocks of the current sub-block that can be used to generate the first prediction block. 2. The motion information of the prediction block.

In the image decoding method, in the step of determining motion information that can be used to generate the second prediction block, it may be determined based on a picture count (POC) of a reference picture of the adjacent sub-block and a POC of a reference picture of the current block Motion information for generating the second prediction block.

In the image decoding method, in the step of determining motion information that can be used to generate the second prediction block, only when the POC of the reference picture of the adjacent sub-block is equal to the POC of the reference picture of the current block, the adjacent sub-block is The motion information of the block is determined as motion information that can be used to generate the second prediction block.

In the image decoding method, the current subblock may have at least one of a square shape and a rectangular shape.

In the image decoding method, in the step of generating the at least one second prediction block, at least one neighboring subblock of the current subblock may be used only when the current block has neither a motion vector derivation mode nor an affine motion compensation mode of motion information to generate the at least one second prediction block.

In the image decoding method, in the step of generating the final prediction block, when the current sub-block is included in the boundary area of the current block, by obtaining each part of the row or column of the first prediction block adjacent to the boundary A weighted sum of one sample and each sample in a partial row or partial column of the second predicted block adjacent to the boundary produces the final predicted block.

In the image decoding method, the samples in the partial row or the partial column adjacent to the boundary of the first prediction block and the partial row or the partial column adjacent to the boundary of the second prediction block The samples may be determined based on at least one of the block size of the current subblock, the size and direction of the motion vector of the current subblock, the inter prediction indicator of the current block, and the POC of the reference picture of the current block.

In the image decoding method, in the step of generating the final prediction block, different weighting factors may be applied to samples in the first prediction block and the second prediction block by at least one of the size and direction of the motion vector of the current subblock point to obtain the weighted sum of the first prediction block and the second prediction block.

The present invention provides a method for encoding an image, the method comprising: generating a first prediction block of the current block using motion information of the current block; determining among motion information of at least one adjacent sub-block of the current sub-block motion information that can be used to generate a second prediction block; use the determined motion information to generate at least one second prediction block of the current subblock; based on the first prediction block of the current block and the at least one second prediction of the current subblock The weighted sum of the blocks is used to generate the final predicted block.

In the image encoding method, in the step of determining motion information that can be used to generate the second prediction block, it may be determined that the motion information that can be used to generate the second prediction block can be used based on at least one of a size and a direction of a motion vector of the adjacent sub-block. sports information.

In the image coding method, in the step of determining the motion information that can be used to generate the second prediction block, it may be determined that the motion information that can be used to generate the second prediction block may be determined based on the POC of the reference picture of the adjacent sub-block and the POC of the reference picture of the current block. 2. The motion information of the prediction block.

In the image encoding method, in the step of determining motion information that can be used to generate the second prediction block, only when the POC of the reference picture of the adjacent sub-block is equal to the POC of the reference picture of the current block, the adjacent sub-block may be The motion information of the sub-block is determined as motion information that can be used to generate the second prediction block.

In the image encoding method, the current subblock may have at least one of a square shape and a rectangular shape.

In the image coding method, in the step of generating the at least one second prediction block, the motion of the at least one adjacent sub-block may be used only when the current block has neither a motion vector derivation mode nor an affine motion compensation mode information to generate the at least one second prediction block.

In the image encoding method, in the step of generating the final prediction block, when the current sub-block is included in the boundary area of the current block, the sample may be points and the weighted sum of the samples in part of the row or part of the column of the second prediction block adjacent to the boundary to produce the final prediction block.

In the image coding method, the samples in the partial row or the partial column adjacent to the boundary of the first prediction block and the partial row or the partial column adjacent to the boundary of the second prediction block The samples may be determined based on at least one of the block size of the current subblock, the size and direction of the motion vector of the current subblock, the inter prediction indicator of the current block, and the POC of the reference picture of the current block.

In the image encoding method, in the step of generating the final prediction block, different weight values may be applied to samples in the first prediction block and the second prediction block by at least one of the size and direction of the motion vector of the current subblock. points to obtain the weighted sum.

The present invention provides a recording medium for storing a bit stream generated by an image encoding method, the image encoding method comprising: generating a first prediction block of the current block using motion information of the current block; Determine the motion information that can be used to generate the second prediction block from the motion information of the sub-block; use the determined motion information to generate at least one second prediction block of the current sub-block; based on the first prediction block of the current block and the current sub-block A weighted sum of the at least one second prediction block to generate a final prediction block.

beneficial effect

According to the present invention, a method and apparatus for encoding/decoding an image with improved compression efficiency can be provided.

According to the present invention, image encoding/decoding efficiency can be improved.

According to the present invention, the computational complexity of the image encoder and the image decoder can be reduced.

Description of drawings

1 is a block diagram showing a configuration of an encoding apparatus according to an embodiment to which the present invention is applied;

2 is a block diagram showing a configuration of a decoding apparatus according to an embodiment to which the present invention is applied;

3 is a diagram schematically showing a partition structure of an image used when encoding or decoding an image;

4 is a diagram illustrating an embodiment of an inter prediction process;

5 is a flowchart illustrating an image encoding method according to an embodiment of the present invention;

6 is a flowchart illustrating an image decoding method according to an embodiment of the present invention;

7 is a flowchart illustrating an image encoding method according to another embodiment of the present invention;

8 is a flowchart illustrating an image decoding method according to another embodiment of the present invention;

9 is a diagram illustrating an example of deriving a spatial motion vector candidate for a current block;

10 is a diagram illustrating an example of deriving a temporal motion vector candidate for a current block;

11 is a diagram illustrating an example of adding a spatial merge candidate to a merge candidate list;

12 is a diagram illustrating an example of adding a temporal merge candidate to a merge candidate list;

13 is a diagram illustrating an example of performing overlapping block motion compensation on a sub-block-by-sub-block basis;

14 is a diagram illustrating an example of performing overlapping block motion compensation using motion information of sub-blocks of a co-located block;

15 is a diagram illustrating an example of performing overlapping block motion compensation using motion information of a block adjacent to a boundary of a reference block;

16 is a diagram illustrating an example of performing overlapping block motion compensation on a sub-block group-by-sub-block group basis;

17 is a diagram showing an example of the number of pieces of motion information for overlapping block motion compensation;

18 and 19 are diagrams illustrating an order of deriving motion information for generating a second prediction block;

20 is a diagram illustrating determining whether motion information of a neighboring subblock is information that can be used to generate a second prediction block by comparing the POC of the reference picture of the current subblock with the POC of the reference pictures of neighboring subblocks of the current subblock A diagram of the example;

21 is a diagram illustrating an embodiment of applying a weighting factor when calculating a weighted sum of a first prediction block and a second prediction block;

22 is a diagram illustrating an embodiment of applying different weighting factors to samples in a block according to their positions when calculating a weighted sum of a first prediction block and a second prediction block;

23 is a diagram illustrating an embodiment of cumulatively calculating a weighted sum of a first prediction block and a second prediction block sequentially in a predetermined order during overlapping block motion compensation;

24 is a diagram illustrating an embodiment of calculating a weighted sum of a first prediction block and a second prediction block during overlapping block motion compensation;

FIG. 25 is a flowchart illustrating an image decoding method according to another embodiment of the present invention.

Detailed ways

Various modifications can be made to the invention, and there are various embodiments of the invention, examples of which will now be provided and described in detail with reference to the accompanying drawings. However, the present invention is not limited thereto, although the exemplary embodiments may be construed to include all modifications, equivalents, or alternatives within the technical idea and technical scope of the present invention. Like reference numbers refer to the same or similar functions in all respects. In the drawings, the shapes and sizes of elements may be exaggerated for clarity. In the following detailed description of the invention, reference is made to the accompanying drawings which show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure. It should be understood that the various embodiments of the present disclosure, although different, are not necessarily mutually exclusive. For example, the specific features, structures and characteristics described herein in association with one embodiment can be implemented in other embodiments without departing from the spirit and scope of the present disclosure. Furthermore, it should be understood that the position or arrangement of various elements within each disclosed embodiment may be modified without departing from the spirit and scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the disclosure is defined solely by the appended claims (along with the full scope of equivalents to which such claims are entitled, where properly interpreted).

The terms "first", "second", etc. used in the specification may be used to describe various components, but these components should not be construed as being limited to the terms. The terms are only used to distinguish one component from another. For example, a "first" component could be termed a "second" component, and a "second" component could similarly be termed a "first" component, without departing from the scope of the present invention. The term "and/or" includes combinations of items or any of the items.

It will be understood that in this specification, when an element is simply referred to as being "connected to" or "coupled to" another element rather than being "directly connected to" or "directly coupled to" another element, it may be "directly connected to" or "coupled directly to" another element. Connected to" or "directly coupled to" another element, or connected to or coupled to another element with intervening other elements. In contrast, it will be understood that when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements present.

Furthermore, the constituent parts shown in the embodiments of the present invention are shown independently so as to exhibit characteristic functions different from each other. Therefore, it does not mean that each constituent element is composed as a separate hardware or software constituent unit. In other words, for convenience, each component includes each of the enumerated components. Accordingly, at least two of each component may be combined to form one component, or one component may be divided into a plurality of components to perform each function. Embodiments in which each constituent element is combined and embodiments in which one constituent element is divided are also included in the scope of the present invention without departing from the essence of the present invention.

The terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. An expression used in the singular includes the plural unless it has a clearly different meaning from the context. In this specification, it will be understood that terms such as "comprising", "having", etc. are intended to designate features, quantities, steps, acts, elements, components, or combinations thereof disclosed in the specification is not intended to exclude the possibility that one or more other features, numbers, steps, acts, elements, components, or combinations thereof may be present or may be added. In other words, when a particular element is referred to as being "included", elements other than the corresponding element are not excluded, but rather, additional elements may be included in embodiments of the present invention or within the scope of the present invention .

Furthermore, some constituent elements may not be indispensable constituent elements to perform the necessary functions of the present invention, but optional constituent elements that merely enhance the performance thereof. The present invention can be implemented by including only the essential components for implementing the present invention and excluding components used in improving performance. A structure including only the indispensable constituent parts and excluding optional constituent parts used only when improving performance is also included in the scope of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing exemplary embodiments of the present invention, well-known functions or constructions will not be described in detail since they would unnecessarily obscure an understanding of the present invention. The same constituent elements in the drawings are denoted by the same reference numerals, and repeated descriptions of the same elements will be omitted.

Also, hereinafter, an image may mean a picture constituting a video, or may mean a video itself. For example, "encode or decode a picture or both" may mean "encode or decode a video or both" and may mean "encode or decode one of a plurality of pictures of a video" Or do both". Here, the picture and the image may have the same meaning.

term description

Encoder: means a device that performs encoding.

Decoder: means a device that performs decoding.

Blocks: are samples of an MxN matrix. Here, M and N mean positive integers, and block may mean a sample matrix in two-dimensional form. A block can refer to a unit. The current block may mean an encoding target block to be targeted when encoding, or a decoding target block to be targeted when decoding. Also, the current block may be at least one of an encoding block, a prediction block, a residual block, and a transform block.

Sample: is the basic unit that makes up a block. A sample can be represented as a value from 0 to 2 ^Bd -1 according to the bit depth (Bd). In the present invention, a sample point may be used as the meaning of a pixel.

Unit: Refers to encoding and decoding units. When encoding and decoding images, a cell may be a region created by partitioning a single image. Also, a unit may mean a sub-division unit when a single image is partitioned into a plurality of sub-division units during encoding or decoding. When encoding and decoding an image, predetermined processing for each unit can be performed. A single unit can be partitioned into subunits of smaller size than the size of the unit. By function, a unit may mean a block, a macroblock, 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, or the like. Furthermore, to distinguish a unit from a block, a unit may include a luma component block, a chroma component block associated with the luma component block, and syntax elements for each color component block. The cells may have various sizes and shapes, and in particular, the shapes of the cells may be two-dimensional geometric shapes, such as rectangular shapes, square shapes, trapezoidal shapes, triangular shapes, pentagonal shapes, and the like. Also, the unit information may include at least one of a unit type (indicating a coding unit, a prediction unit, a transform unit, etc.), a unit size, a unit depth, an order in which the units are encoded and decoded, and the like.

Coding tree unit: A single coding tree block configured with luma component Y and two coding tree blocks associated with chroma components Cb and Cr. Additionally, a coding tree unit may be meant to include blocks and syntax elements for each block. Lower layer units, such as coding units, prediction units, transform units, etc., may be constructed by partitioning each coding tree unit using at least one of a quadtree partition method and a binary tree partition method. A coding tree unit may be used as a term for specifying a block of pixels that becomes a processing unit when encoding/decoding an image that is an input image.

Coding tree block: A term that can be used to designate any one of Y coding tree block, Cb coding tree block and Cr coding tree block.

Neighboring block: means a block that is adjacent to the current block. A block adjacent to the current block may mean a block in contact with the boundary of the current block, or a block located within a predetermined distance from the current block. A neighboring block may mean a block that is adjacent to a vertex of the current block. Here, the block adjacent to the vertex of the current block may mean a block that is vertically adjacent to a neighboring block that is horizontally adjacent to the current block, or a block that is horizontally adjacent to a neighboring block that is vertically adjacent to the current block.

Reconstructed neighboring blocks: means neighboring blocks that are adjacent to the current block and have been temporally/spatially encoded or decoded. Here, reconstructing a neighboring block may mean reconstructing a neighboring unit. A reconstructed spatially adjacent block may be a block within the current picture that has been reconstructed by encoding or decoding, or both. A reconstructed temporal neighboring block is a block within the reference picture that is co-located with the current block of the current picture, or a neighboring block to the block.

Cell Depth: It means the extent to which the cell is partitioned. In a tree structure, the root node can be the highest node and the leaf nodes can be the lowest node. Additionally, when a unit is represented as a tree structure, the level at which the unit exists may mean the unit depth.

Bitstream: means a bitstream including encoded image information.

Parameter set: Corresponds to the header information in the structure within the bitstream. At least one of a video parameter set, a sequence parameter set, a picture parameter set, and an adaptation parameter set may be included in the parameter set. Additionally, the parameter set may include slice header and parallel tile header information.

Parsing: may mean determining the value of a syntax element by performing entropy decoding, or may mean entropy decoding itself.

Symbol: may mean at least one of a syntax element, an encoding parameter, and a transform coefficient value of the encoding/decoding target unit. In addition, a symbol may mean an entropy encoding target or an entropy decoding result.

Prediction unit: means a basic unit when performing prediction such as inter prediction, intra prediction, inter compensation, intra compensation, and motion compensation. A single prediction unit may be partitioned into multiple partitions having a small size, or may be partitioned into lower-level prediction units.

PU partition: means the shape obtained by partitioning the PU.

Reference picture list: means a list including one or more reference pictures used for inter-picture prediction or motion compensation. LC (List Combined), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3), etc. are types of reference picture lists. One or more reference picture lists may be used for inter-picture prediction.

Inter-picture prediction indicator: may mean the inter-picture prediction direction (unidirectional prediction, bidirectional prediction, etc.) of the current block. Alternatively, the inter-picture prediction indicator may mean the number of reference pictures used to generate the prediction block of the current block. Further optionally, the inter prediction indicator may mean the number of prediction blocks used to perform inter prediction or motion compensation for the current block.

Reference picture index: means an index indicating a specific reference picture in the reference picture list.

Reference picture: may mean a picture referenced by a particular block for inter-picture prediction or motion compensation.

Motion vector: is a two-dimensional vector used for inter-picture prediction or motion compensation, and may mean an offset between a reference picture and an encoding/decoding target picture. For example, (mvX, mvY) may represent the motion vector, mvX may represent the horizontal component, and mvY may represent the vertical component.

Motion vector candidate: may mean a block that becomes a prediction candidate when a motion vector is predicted, or may mean a motion vector of the block. The motion vector candidates may be listed in a motion vector candidate list.

Motion Vector Candidate List: Can mean a list of motion vector candidates.

Motion Vector Candidate Index: may mean an indicator that indicates a motion vector candidate in the motion vector candidate list. The motion vector candidate index is also referred to as the index of the motion vector predictor.

Motion information: may mean information including motion vector, reference picture index, inter-picture prediction indicator, and at least any one of the following: reference picture list information, reference picture, motion vector candidate, motion vector candidate index, merge candidate and merged indexes.

Merge Candidate List: means a list consisting of merge candidates.

Merge candidate: means spatial merge candidate, temporal merge candidate, combined merge candidate, combined bidirectional prediction merge candidate, zero merge candidate, and the like. A merge candidate may have an inter-picture prediction indicator, a reference picture index for each list, and motion information such as a motion vector.

Merge index: means information indicating merge candidates within the merge candidate list. The merge index may indicate a block used to derive a merge candidate among reconstructed blocks that are spatially and/or temporally adjacent to the current block. The merge index may indicate at least one item of motion information owned by the merge candidate.

Transform unit: means a basic unit when encoding/decoding such as transform, inverse transform, quantization, inverse quantization, and transform coefficient encoding/decoding is performed on a residual signal. A single transform unit may be partitioned into multiple transform units having small sizes.

Scaling: means the process of multiplying transform coefficient levels by factors. Transform coefficients may be generated by scaling transform coefficient levels. Scaling can also be referred to as inverse quantization.

Quantization parameter: may mean the value used when generating the transform coefficient level of the transform coefficient during quantization. A quantization parameter may also mean a value used in generating transform coefficients by scaling transform coefficient levels during inverse quantization. The quantization parameter may be a value mapped on the quantization step size.

Variable delta (Delta) quantization parameter: means the difference between the quantization parameter of the encoding/decoding target unit and the predicted quantization parameter.

Scan: means a method of ordering the coefficients within a block or matrix. For example, changing a two-dimensional matrix of coefficients to a one-dimensional matrix may be referred to as scanning, and changing a one-dimensional matrix of coefficients to a two-dimensional matrix may be referred to as scanning or inverse scanning.

Transform coefficients: may mean coefficient values that are generated after transform is performed in the encoder. Transform coefficients may mean coefficient values generated after at least one of entropy decoding and inverse quantization is performed in a decoder. Quantized levels or quantized transform coefficient levels obtained by quantizing transform coefficients or residual signals may also fall within the meaning of transform coefficients.

Level of quantization: means the value produced by quantizing the transform coefficients or residual signal in the encoder. Alternatively, the level of quantization may mean a value that is an inverse quantization target that undergoes inverse quantization in the decoder. Similarly, quantized transform coefficient levels that are the result of transform and quantization may also fall within the meaning of quantized levels.

Non-zero transform coefficient: means a transform coefficient whose value is not 0, or means a transform coefficient level whose value is not 0.

Quantization matrix: means a matrix used in the quantization process or inverse quantization process performed in order to improve the subjective image quality or the objective image quality. The quantization matrix may also be referred to as a scaling list.

Quantization matrix coefficients: means to quantize each element in the matrix. The quantized matrix coefficients may also be referred to as matrix coefficients.

Default matrix: means a predetermined quantization matrix that is preliminarily defined in the encoder or decoder.

Non-default matrix: means a quantization matrix not initially defined in the encoder or decoder but signaled by the user.

FIG. 1 is a block diagram showing the configuration of an encoding apparatus according to an embodiment to which the present invention is applied.

The encoding device 100 may be an encoder, a video encoding device, or an image encoding device. The video may include at least one image. The encoding apparatus 100 may sequentially encode the at least one image.

1 , the encoding apparatus 100 may include a motion prediction unit 111 , a motion compensation unit 112 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , a transform unit 130 , a quantization unit 140 , an entropy encoding unit 150 , and an inverse quantization unit 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference picture buffer 190 .

The encoding apparatus 100 may perform encoding on the input picture by using the intra mode or the inter mode or both the intra mode and the inter mode. Also, the encoding apparatus 100 may generate a bitstream by encoding an input picture, and may output the generated bitstream. The generated bit stream may be stored in a computer-readable recording medium, or may be streamed through a wired/wireless transmission medium. When the intra mode is used as the prediction mode, the switch 115 may switch to intra. Alternatively, when the inter mode is used as the prediction mode, the switch 115 may switch to the inter mode. Here, the intra mode may mean an intra prediction mode, and the inter mode may mean an inter prediction mode. The encoding apparatus 100 may generate a prediction block of an input block of an input image. Also, after generating the prediction block, the encoding apparatus 100 may encode the residual between the input block and the prediction block. The input image may be referred to as the current image that is the current encoding target. The input block may be referred to as a current block that is a current encoding target or may be referred to as an encoding target block.

When the prediction mode is the intra mode, the intra prediction unit 120 may use pixel values of encoded/decoded blocks adjacent to the current block as reference pixels. The intra prediction unit 120 may perform spatial prediction by using reference pixels, or may generate prediction samples of the input block by performing spatial prediction. Here, intra prediction may mean prediction within a frame.

When the prediction mode is the inter mode, the motion prediction unit 111 may search for an area that best matches the input block from a reference image when performing motion prediction, and may derive a motion vector by using the searched area. Reference images may be stored in the reference picture buffer 190 .

Motion compensation unit 112 may generate a prediction block by performing motion compensation using the motion vector. Here, inter prediction may mean prediction or motion compensation between frames.

When the value of the motion vector is not an integer, the motion prediction unit 111 and the motion compensation unit 112 may generate a prediction block by applying an interpolation filter to a partial region of the reference picture. In order to perform inter-picture prediction or motion compensation on a coding unit, it may be determined which mode among skip mode, merge mode, advanced motion vector prediction (AMVP) mode, and current picture reference mode is used for prediction included in the corresponding coding unit Motion prediction and motion compensation for cells. Then, inter-picture prediction or motion compensation may be differently performed according to the determined mode.

The subtractor 125 may generate a residual block by using the residual between the input block and the prediction block. The residual block may be referred to as a residual signal. The residual signal may mean the difference between the original signal and the predicted signal. In addition, the residual signal may be a signal generated by transforming or quantizing, or transforming and quantizing the difference between the original signal and the predicted signal. The residual block may be a block-unit residual signal.

The transform unit 130 may generate transform coefficients by performing transform on the residual block, and may output the generated transform coefficients. Here, the transform coefficients may be coefficient values generated by performing transform on the residual block. When transform skip mode is applied, transform unit 130 may skip transforming the residual block.

The quantized levels may be generated by applying quantization to the transform coefficients or to the residual signal. Hereinafter, in an embodiment, the level of quantization may also be referred to as a transform coefficient.

The quantization unit 140 may generate a quantized level by quantizing a transform coefficient or a residual signal according to a parameter, and may output the generated quantized level. Here, the quantization unit 140 may quantize the transform coefficients by using a quantization matrix.

The entropy encoding unit 150 may generate a bitstream by performing entropy encoding on a value calculated by the quantization unit 140 or an encoding parameter value calculated when encoding is performed according to a probability distribution, and may output the generated bitstream. The entropy encoding unit 150 may perform entropy encoding on pixel information of the image and information for decoding the image. For example, the information used to decode the image may include syntax elements.

When entropy coding is applied, symbols can be represented in such a way that a smaller number of bits are allocated to symbols with a high generation chance and a larger number of bits are allocated to symbols with a low generation chance, thereby reducing the amount of time needed to be coded. The size of the bitstream of symbols. The entropy encoding unit 150 may use an encoding method for entropy encoding such as Exponential Golomb, Context Adaptive Variable Length Coding (CAVLC), Context Adaptive Binary Arithmetic Coding (CABAC). For example, the entropy encoding unit 150 may perform entropy encoding by using a variable length coding/code (VLC) table. Also, the entropy encoding unit 150 may derive a binarization method of the target symbol and a probability model of the target symbol/bin, and may perform arithmetic encoding by using the derived binarization method and context model.

In order to encode the transform coefficient level, the entropy encoding unit 150 may change the coefficients in a two-dimensional block form into a one-dimensional vector form by using a transform coefficient scanning method.

Encoding parameters may include information such as syntax elements (flags, indices, etc.) encoded in the encoder and signaled to the decoder, as well as information derived when encoding or decoding is performed. Encoding parameters may mean information required when encoding or decoding an image. For example, the encoding parameters may include at least one value or combination of the following: unit/block size, unit/block depth, unit/block partition information, unit/block partition structure, whether to perform quad-tree partitioning, whether to perform Partition in binary tree form, partition direction in binary tree form (horizontal direction or vertical direction), partition form in binary tree form (symmetric partition or asymmetric partition), intra prediction mode/direction, reference sample filtering method, prediction block filtering method, Prediction Block Filter Taps, Prediction Block Filter Coefficients, Inter Prediction Mode, Motion Information, Motion Vector, Reference Picture Index, Inter Prediction Angle, Inter Prediction Indicator, Reference Picture List, Reference Picture, Motion Vector Predictor Candidate , motion vector candidate list, whether to use merge mode, merge candidate, merge candidate list, whether to use skip mode, interpolation filter type, interpolation filter tap, interpolation filter coefficient, motion vector size, motion vector representation precision, transform Type, transform size, information on whether to use primary (first) transform, information on whether to use secondary transform, primary transform index, secondary transform index, information on whether residual signal exists, coding block style, coding block flag (CBF) , quantization parameter, quantization matrix, whether to apply in-loop filter, in-loop filter coefficients, in-loop filter taps, in-loop filter shape/form, whether to apply deblocking filter, deblocking filter coefficients , DF tap, DF strength, DF shape/form, whether to apply Adaptive Sample Offset, Adaptive Sample Offset Value, Adaptive Sample Offset Category, Adaptive Sample Offset type, whether to apply adaptive in-loop filter, adaptive in-loop filter coefficients, adaptive in-loop filter taps, adaptive in-loop filter shape/form, binarization/de-binarization method, context Model determination method, context model update method, whether to execute normal mode, whether to execute bypass mode, context bins, bypass bins, transform coefficients, transform coefficient levels, transform coefficient level scan method, image display/output order, stripes Identification information, slice type, slice partition information, parallel block identification information, parallel block type, parallel block partition information, picture type, bit depth, and information of luma signal or chroma signal.

Here, signaling a flag or index may mean that the corresponding flag or index is entropy-encoded by the encoder and included in the bitstream, and may mean that the corresponding flag or index is entropy-decoded by the decoder from the bitstream.

When the encoding apparatus 100 performs encoding through inter prediction, the encoded current image may be used as a reference image for another image that is subsequently processed. Accordingly, the encoding apparatus 100 may reconstruct or decode the encoded current image, or may store the reconstructed or decoded image as a reference image.

The quantized levels may be inverse quantized in the inverse quantization unit 160 , or may be inversely transformed in the inverse transform unit 170 . The inverse quantized or inverse transformed coefficients or both inverse quantized and inverse transformed coefficients may be added to the prediction block by the adder 175 . A reconstructed block may be generated by adding the inverse quantized or inverse transformed coefficients, or both inverse quantized and inverse transformed coefficients, to the prediction block. Here, the inverse-quantization or inverse-transformed coefficients or both inverse-quantization and inverse-transformation coefficients may mean coefficients on which at least one of inverse quantization and inverse transformation is performed, and may mean a reconstructed residual block.

The reconstructed block may pass through filter unit 180 . Filter unit 180 may apply at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed block or reconstructed image. Filter unit 180 may be referred to as an in-loop filter.

A deblocking filter can remove block distortions generated at boundaries between blocks. In order to determine whether to apply the deblocking filter, whether to apply the deblocking filter to the current block may be determined based on pixels included in several rows or columns included in the block. When a deblocking filter is applied to a block, another filter may be applied according to the desired deblocking filtering strength.

To compensate for encoding errors, appropriate offset values can be added to pixel values by using sample adaptive offsets. The sample adaptive offset can correct the offset between the deblocked image and the original image on a pixel-by-pixel basis. A method of applying the offset considering edge information about each pixel may be used, or a method of partitioning the pixels of the image into a predetermined number of areas, determining the area to which the offset is applied, and applying the offset to the determined area.

The adaptive loop filter may perform filtering based on a comparison between the filtered reconstructed image and the original image. Pixels included in the image may be partitioned into predetermined groups, filters to be applied to each group may be determined, and different filtering may be performed for each group. Information on whether to apply ALF may be signaled per coding unit (CU), and the shape and coefficients of ALF to be applied to each block may vary.

The reconstructed blocks or reconstructed images passed through the filter unit 180 may be stored in the reference picture buffer 190 . FIG. 2 is a block diagram showing the configuration of a decoding apparatus to which the present invention is applied, according to an embodiment.

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

2 , the decoding apparatus 200 may include an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , a motion compensation unit 250 , an adder 255 , a filter unit 260 , and a reference picture buffer 270 .

The decoding apparatus 200 may receive the bit stream output from the encoding apparatus 100 . The decoding apparatus 200 may receive a bitstream stored in a computer-readable recording medium, or may receive a bitstream streamed through a wired/wireless transmission medium. The decoding apparatus 200 may decode the bitstream by using the intra mode or the inter mode. Also, the decoding apparatus 200 may generate a reconstructed image or a decoded image generated by performing the decoding, and may output the reconstructed image or the decoded image.

When the prediction mode used in decoding is intra mode, the switch may be switched to intra. Alternatively, when the prediction mode used in decoding is the inter mode, the switch may be switched to the inter mode.

The decoding apparatus 200 may obtain a reconstructed residual block by decoding an input bitstream, 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 to be a decoding target by adding the reconstructed residual block to the prediction block. The decoding target block may be referred to as a current block.

The entropy decoding unit 210 may generate symbols by entropy decoding the bitstream according to the probability distribution. The generated symbols may include quantized, graded symbols. Here, the entropy decoding method may be an inverse process of the entropy encoding method described above.

In order to decode the transform coefficient level, the entropy decoding unit 210 may change the coefficients in the form of a one-dimensional vector to the form of a two-dimensional block by using a transform coefficient scanning method.

The quantized levels may be inverse quantized in the inverse quantization unit 220 , or may be inversely transformed in the inverse transform unit 230 . The level of quantization may be the result of inverse quantization or inverse transform, or both, and may be produced as a reconstructed residual block. Here, the inverse quantization unit 220 may apply a quantization matrix to the quantized level.

When the intra mode is used, the intra prediction unit 240 may generate a prediction block by performing spatial prediction using pixel values of already decoded blocks adjacent to the decoding target block.

When the inter mode is used, the motion compensation unit 250 may generate a prediction block by performing motion compensation using a reference image and a motion vector stored in the reference picture buffer 270 .

The adder 255 may generate the reconstructed block by adding the reconstructed residual block to the prediction block. Filter unit 260 may apply at least one of a deblocking filter, a sample adaptive offset, and an adaptive loop filter to the reconstructed block or reconstructed image. The filter unit 260 may output the reconstructed image. The reconstructed block or reconstructed image may be stored in the reference picture buffer 270 and may be used when performing inter prediction.

FIG. 3 is a diagram schematically showing a partition structure of an image when the image is encoded and decoded. FIG. 3 schematically shows an example of partitioning a single cell into multiple subordinate cells.

For efficient partitioning of images, coding units (CUs) may be used when encoding and decoding. The coding unit may be used as a basic unit when encoding/decoding an image. In addition, the coding unit may be used as a unit for distinguishing intra mode and inter mode when encoding/decoding an image. A coding unit may be a basic unit for predicting, transforming, quantizing, inverse transforming, inverse quantizing, or encoding/decoding processing of transform coefficients.

Referring to FIG. 3 , a picture 300 is sequentially partitioned according to largest coding units (LCUs), and the LCU units are determined as a partition structure. Here, the LCU may be used in the same meaning as a coding tree unit (CTU). Cell partitioning may mean partitioning the blocks associated with the cell. In the block partition information, information of the unit depth may be included. The depth information may represent the number or extent or both the number and extent of the cell being partitioned. A single unit may be partitioned in layers associated with depth information based on a tree structure. Each partitioned subordinate unit may have depth information. The depth information may be information representing the size of a CU, and may be stored in each CU.

The partition structure may mean the distribution of coding units (CUs) in the LCU 310 . Such a distribution may be determined depending on whether a single CU is partitioned into multiple (positive integers equal to or greater than 2, including 2, 4, 8, 16, etc.) CUs. The horizontal and vertical sizes of the CU generated by partitioning may be half of the horizontal and vertical sizes of the CU before partitioning, respectively, or may have smaller horizontal and vertical sizes, respectively, than those before partitioning according to the number of partitioning size. A CU may be recursively partitioned into multiple CUs. Partitioning of a CU may be performed recursively up to a predefined depth or a predefined size. For example, the depth of the LCU may be 0, and the depth of the smallest coding unit (SCU) may be a predefined maximum depth. Here, the LCU may be a coding unit having the largest coding unit size, and the SCU may be a coding unit having the smallest coding unit size as described above. Starting from LCU 310 for partitioning, the CU depth is increased by 1 when the horizontal size or vertical size or both of the CU's horizontal size and vertical size are reduced by partitioning.

Also, information on whether the CU is partitioned may be represented by using partition information of the CU. The partition information may be 1-bit information. All CUs except SCUs may include partition information. For example, when the value of the partition information is the first value, the CU may not be partitioned, and when the value of the partition information is the second value, the CU may be partitioned.

Referring to FIG. 3 , an LCU with depth 0 may be a 64×64 block. 0 can be the minimum depth. An SCU with depth 3 may be an 8x8 block. 3 can be the maximum depth. CUs for a 32x32 block and a 16x16 block may be denoted as depth 1 and depth 2, respectively.

For example, when a single coding unit is partitioned into four coding units, the horizontal and vertical sizes of the partitioned four coding units may be half the horizontal and vertical sizes of the CU before being partitioned. In one embodiment, when a coding unit having a size of 32×32 is partitioned into four coding units, each of the partitioned four coding units may have a size of 16×16. When a single coding unit is partitioned into four coding units, it may be said that the coding unit may be partitioned into a quad-tree form.

For example, when a single coding unit is partitioned into two coding units, the horizontal or vertical size of the two coding units may be half of the horizontal or vertical size of the coding unit before being partitioned. For example, when a coding unit having a size of 32×32 is partitioned in a vertical direction, each of the partitioned two coding units may have a size of 16×32. When a single coding unit is partitioned into two coding units, the coding unit may be said to be partitioned in a binary tree form. The LCU 320 of FIG. 3 is an example of an LCU to which both quad-tree form partitions and binary tree form partitions are applied.

FIG. 4 is a diagram illustrating an example of an inter-picture prediction process.

In FIG. 4, a rectangle may represent a picture. In Fig. 4, arrows indicate prediction directions. The pictures may be classified into intra pictures (I pictures), predictive pictures (P pictures), and bidirectional predictive pictures (B pictures) according to the encoding type of the pictures.

I-pictures can be encoded by intra-frame prediction without inter-picture prediction. A P-picture may be encoded via inter-picture prediction by using a reference picture that exists in one direction (ie, forward or backward) with respect to the current block. A B picture may be encoded via inter-picture prediction by using reference pictures that are preset in two directions (ie, forward and backward) with respect to the current block. When inter-picture prediction is used, the encoder may perform inter-picture prediction or motion compensation, and the decoder may perform corresponding motion compensation.

Hereinafter, embodiments of inter-picture prediction will be described in detail.

Inter-picture prediction or motion compensation may be performed using reference pictures and motion information.

The motion information of the current block may be derived by each of the encoding apparatus 100 and the decoding apparatus 200 during inter-picture prediction. The motion information of the current block may be derived by using motion information of reconstructed neighboring blocks, co-located blocks (also referred to as col blocks or co-located blocks), and/or motion information of blocks adjacent to the co-located block. A co-located block may mean a block that is spatially co-located with the current block within a previously reconstructed co-located picture (also referred to as a col picture or a co-located picture). The co-located picture may be one picture among one or more reference pictures included in the reference picture list.

The method of deriving the motion information of the current block may vary according to the prediction mode of the current block. For example, as prediction modes for inter-picture prediction, there may be AMVP mode, merge mode, skip mode, current picture reference mode, and the like. The merge mode may be referred to as a motion merge mode.

For example, when AMVP is used as a prediction mode, at least one of a motion vector of a reconstructed adjacent block, a motion vector of a co-located block, a motion vector of a block adjacent to the co-located block, and a motion vector (0,0) may be determined. is a motion vector candidate for the current block, and a motion vector candidate list is generated by using the motion vector candidate. The motion vector candidates of the current block may be derived by using the generated motion vector candidate list. The motion information of the current block may be determined based on the derived motion vector candidates. A motion vector of a co-located block or a motion vector of a block adjacent to the co-located block may be referred to as a temporal motion vector candidate, and a motion vector of a reconstructed adjacent block may be referred to as a spatial motion vector candidate.

The encoding apparatus 100 may calculate a motion vector difference (MVD) between the motion vector of the current block and the motion vector candidates, and may perform entropy encoding on the motion vector difference (MVD). Also, the encoding apparatus 100 may perform entropy encoding on the motion vector candidate index and generate a bitstream. The motion vector candidate index may indicate the best motion vector candidate among the motion vector candidates included in the motion vector candidate list. The decoding apparatus may perform entropy decoding on the motion vector candidate index included in the bitstream, and may select the motion vector candidate of the decoding target block from among the motion vector candidates included in the motion vector candidate list by using the entropy-decoded motion vector candidate index . In addition, the decoding apparatus 200 may add the entropy-decoded MVD to the motion vector candidates extracted through the entropy decoding, thereby deriving a motion vector of the decoding target block.

The bitstream may include a reference picture index indicating a reference picture. The reference picture index may be entropy encoded by the encoding apparatus 100 and then signaled to the decoding apparatus 200 as a bitstream. The decoding apparatus 200 may generate a prediction block of the decoding target block based on the derived motion vector and reference picture index information.

Another example of the method of deriving the motion information of the current block may be merge mode. The merge mode may mean a method of merging motions of a plurality of blocks. The merge mode may mean a mode in which motion information of the current block is derived from motion information of neighboring blocks. When the merge mode is applied, the merge candidate list may be generated using the motion information of the reconstructed neighboring blocks and/or the motion information of the co-located blocks. The motion information may include at least one of a motion vector, a reference picture index, and an inter-picture prediction indicator. The prediction indicator may indicate unidirectional prediction (L0 prediction or L1 prediction) or bidirectional prediction (L0 prediction and L1 prediction).

The merge candidate list may be a list of stored motion information. The motion information included in the merging candidate list may be at least one of a zero merging candidate and new motion information, wherein the new motion information is motion information (spatial merging candidate) of a neighboring block adjacent to the current block, current The block includes a combination of motion information (temporal merging candidates) of co-located blocks in the reference picture, and motion information present in the merging candidate list.

The encoding apparatus 100 may generate a bitstream by performing entropy encoding on at least one of the merge flag and the merge index, and may signal the bitstream to the decoding apparatus 200 . The merge flag may be information indicating whether a merge mode is performed for each block, and the merge index may be information indicating which adjacent block among adjacent blocks of the current block is a merge target block. For example, neighboring blocks of the current block may include left neighboring blocks to the left of the current block, upper neighboring blocks above the current block, and temporal neighboring blocks temporally neighboring to the current block.

The skip mode may be a mode in which motion information of an adjacent block is applied to the current block as it is. When the skip mode is applied, the encoding apparatus 100 may perform entropy encoding on information of the fact of which block's motion information is to be used as the current block's motion information to generate a bitstream, and may signal the bitstream to the decoding apparatus 200. The encoding apparatus 100 may not signal a syntax element on at least any one of the motion vector difference information, the encoding block flag, and the transform coefficient level to the decoding apparatus 200 .

The current picture reference mode may mean a prediction mode in which a previously reconstructed region to which the current block within the current picture belongs is used for prediction. Here, a vector may be used to specify the previously reconstructed area. The information indicating whether the current block is to be encoded in the current picture reference mode may be encoded by using the reference picture index of the current block. A flag or index indicating whether the current block is a block encoded in the current picture reference mode may be signaled and may be derived based on the reference picture index of the current block. In the case where the current block is encoded in the current picture reference mode, the current picture may be added to the reference picture list for the current block so as to be at a fixed position or a random position in the reference picture list. The fixed position may be, for example, the position indicated by the reference picture index 0 or the last position in the list. When the current picture is added to the reference picture list so as to be at the random location, a reference picture index indicating the random location may be signaled.

Based on the above description, the image encoding method and the image decoding method according to the embodiments of the present invention will be described in detail below.

FIG. 5 is a flowchart illustrating an image encoding method according to an embodiment of the present invention, and FIG. 6 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

5, the encoding apparatus may derive motion vector candidates (step S501), and may generate a motion vector candidate list based on the derived motion vector candidates (step S502). After the motion vector candidate list is generated, a motion vector may be determined based on the generated motion vector candidate list (step S503 ), and motion compensation may be performed based on the determined motion vector (step S504 ). Thereafter, the encoding apparatus may encode information associated with motion compensation (step S505).

6, the decoding apparatus may perform entropy decoding on the information associated with motion compensation received from the encoding apparatus (step S601), and may derive motion vector candidates (step S602). The decoding apparatus may generate a motion vector candidate list based on the derived motion vector candidates (step S603 ), and determine a motion vector using the generated motion vector candidate list (step S604 ). Thereafter, the decoding apparatus may perform motion compensation by using the determined motion vector (step S605).

FIG. 7 is a flowchart illustrating an image encoding method according to another embodiment of the present invention, and FIG. 8 is a flowchart illustrating an image decoding method according to another embodiment of the present invention.

Referring to FIG. 7 , the encoding apparatus may derive merge candidates (step S701 ), and generate a merge candidate list based on the derived merge candidates. After the merge candidate list is generated, the encoding apparatus may determine motion information using the generated merge candidate list (step S702 ), and may perform motion compensation on the current block using the determined motion information (step S703 ). Thereafter, the encoding apparatus may perform entropy encoding on the information associated with the motion compensation (step S704).

8 , the decoding apparatus may perform entropy decoding on the information associated with motion compensation received from the encoding apparatus ( S801 ), derive merge candidates ( S802 ), and generate a merge candidate list based on the derived merge candidates. After the merging candidate list is generated, the decoding apparatus may determine motion information of the current block by using the generated merging candidate list (S803). Thereafter, the decoding apparatus may perform motion compensation using the motion information (S804).

5 and 6 show examples in which the AMVP shown in FIG. 4 is applied, and FIGS. 7 and 8 show examples in which the merge mode shown in FIG. 4 is applied.

Hereinafter, each step in FIGS. 5 and 6 will be described, and then each step in FIGS. 7 and 8 will be described. However, the motion compensation steps corresponding to S504, S605, S703 and S804 and the entropy encoding/decoding steps corresponding to S505, S601, S704 and S801 will be collectively described.

Hereinafter, each step in FIGS. 5 and 6 will be described in detail below.

First, the steps of deriving motion vector candidates (S501, S602) will be described in detail.

The motion vector candidates of the current block may include one of spatial motion vector candidates and temporal motion vector candidates, or both spatial motion vector candidates and temporal motion vector candidates.

The spatial motion vector of the current block may be derived from reconstructed blocks adjacent to the current block. For example, motion vectors of reconstructed blocks adjacent to the current block may be determined as spatial motion vector candidates of the current block.

FIG. 9 is a diagram illustrating an example of deriving spatial motion vector candidates of the current block.

Referring to FIG. 9 , spatial motion vector candidates of the current block may be derived from neighboring blocks adjacent to the current block X. The adjacent blocks adjacent to the current block X include the block B1 adjacent to the upper end of the current block, the block A1 adjacent to the left end of the current block, the block B0 adjacent to the upper right corner of the current block, and the upper left corner of the current block. At least one of the adjacent block B2 and the block A0 adjacent to the lower left corner of the current block. Neighboring blocks adjacent to the current block may have a square shape or a non-square shape. When one adjacent block among a plurality of adjacent blocks adjacent to the current block has a motion vector, the motion vector of the adjacent block may be determined as a spatial motion vector candidate of the current block. Whether the neighboring block has a motion vector or whether the motion vector of the neighboring block can be used as the spatial motion vector of the current block may be determined based on the determination of whether the neighboring block exists or whether the neighboring block has been encoded through the inter prediction process candidate. The determination of whether a particular neighboring block has a motion vector or the determination of whether the motion vector of the neighboring block can be used as a spatial motion vector candidate of the current block may be performed in a predetermined order. For example, as shown in FIG. 9, the availability determination of the motion vector may be performed in the order of blocks A0, A1, B0, B1, and B2.

When the reference picture of the current block and the reference pictures of neighboring blocks having motion vectors are different from each other, the motion vectors of the neighboring blocks are scaled, and then the scaled motion vectors can be used as spatial motion vector candidates of the current block. The motion vector scaling may be performed based on at least any one of a distance between the current picture and a reference picture of the current block and a distance between the current picture and a reference picture of an adjacent block. Here, the spatial motion vector candidate of the current block may be derived by scaling the motion vector of the neighboring block according to the ratio of the distance between the current picture and the reference picture of the current block to the distance between the current picture and the reference picture of the neighboring block.

However, when the reference picture index of the current block and the reference picture index of the neighboring block having the motion vector are different, the scaled motion vector of the neighboring block may be determined as the spatial motion vector candidate of the current block. Even in this case, scaling may be performed based on at least one of the distance between the current picture and the reference picture of the current block and the distance between the current picture and the reference picture of the neighboring block.

Regarding scaling, motion vectors of neighboring blocks may be scaled based on a reference picture indicated by a reference picture index having a predefined value, and the scaled motion vector may be determined as a spatial motion vector candidate of the current block. The predefined value may be zero or a positive integer. For example, the distance between the current picture and the reference picture with the predefined value of the adjacent block may be compared by the ratio between the distance between the current picture and the reference picture of the current block indicated by the reference picture index with the predefined value The motion vectors of neighboring blocks are scaled to derive spatial motion vector candidates for the current block.

Alternatively, the spatial motion vector candidate of the current block may be derived based on at least one of the coding parameters of the current block.

The temporal motion vector candidates of the current block may be derived from reconstructed blocks included in co-located pictures of the current picture. A co-located picture is a picture encoded/decoded before the current picture, and may be different from the current picture in time order.

FIG. 10 is a diagram illustrating an example of deriving a temporal motion vector candidate of a current block.

10, a temporal motion vector candidate for a current block may be derived from a block outside a co-located picture (also referred to as a co-located picture) including the current picture that is spatially co-located with the current block X, or from a block including The temporal motion vector candidate of the current block is derived from a block located inside a block that is spatially co-located with the current block X. Here, the temporal motion vector candidate may mean a motion vector of a co-located block of the current block. For example, the temporal motion vector candidate of the current block X may be derived from the block H adjacent to the lower left corner of the block C that is spatially co-located with the current block X, or the current block may be derived from the block C3 including the middle position of the block C Temporal motion vector candidates for X. Block H, block C3, etc. used for deriving temporal motion vector candidates of the current block are called co-located blocks.

Optionally, at least one of a temporal motion vector candidate, a co-located picture, a co-located block, a prediction list utilization flag, and a reference picture index may be derived based on at least one of the encoding parameters.

When the distance between the current picture including the current block and the reference picture of the current block is different from the distance between the co-located picture including the co-located block and the reference picture of the co-located block, the current picture may be obtained by scaling the motion vector of the co-located block Temporal motion vector candidates for the block. Here, scaling may be performed based on at least one of the distance between the current picture and the reference picture of the current block and the distance between the co-located picture and the reference picture of the co-located block. For example, the temporal motion vector candidate for the current block may be derived by scaling the motion vector of the co-located block according to the ratio of the distance between the current picture and the reference picture of the current block to the distance between the co-located picture and the reference picture of the co-located block.

Next, the steps of generating a motion vector candidate list based on the derived motion vector candidates (S502, S503) will be described.

The generating of the motion vector candidate list may include a process of adding or removing motion vector candidates to or from the motion vector candidate list, and a process of adding combined motion vector candidates to the motion vector candidate list.

First, a process of adding or removing a derived motion vector candidate to a motion vector candidate list or removing a derived motion vector candidate from the motion vector candidate list will be described. The encoding apparatus and the decoding apparatus may add the derived motion vector candidates to the motion vector candidate list in the order in which the motion vector candidates are derived.

It is assumed that the motion vector candidate list mvpListLX may mean a motion vector candidate list corresponding to the reference picture lists L0, L1, L2, and L3. That is, the motion vector candidate list corresponding to the reference picture list L0 can be represented by mvpListL0.

In addition to the spatial motion vector candidates and the temporal motion vector candidates, a motion vector having a predetermined value may be added to the motion vector candidate list. For example, when the number of motion vector candidates in the motion vector candidate list is less than the maximum number of motion vector candidates that can be included in the motion vector candidate list, a motion vector having a value of 0 may be added to the motion vector candidate list.

Next, the process of adding the combined motion vector candidate to the motion vector candidate list will be described.

When the number of motion vector candidates in the motion vector candidate list is less than the maximum number of motion vector candidates that can be included in the motion vector candidate list, one or more motion vector candidates in the motion vector candidate list are combined to generate an or More combined motion vector candidates, and the resulting combined motion vector candidates may be added to the motion vector candidate list. For example, at least one or more of spatial motion vector candidates, temporal motion vector candidates, and zero motion vector candidates included in the motion vector candidate list are used to generate combined motion vector candidates, and the generated combined motion vector candidates may be Add to motion vector candidate list.

Alternatively, a combined motion vector candidate may be generated based on at least one of the encoding parameters, and the combined motion vector candidate generated based on the at least one of the encoding parameters may be added to the motion vector candidate list.

Next, the steps of selecting the predicted motion vector of the current block from the motion vector candidate list ( S503 , S604 ) will be described below.

Among the motion vector candidates included in the motion vector candidate list, the motion vector candidate indicated by the motion vector candidate index may be determined as the predicted motion vector of the current block.

The encoding apparatus may calculate a difference between the predicted motion vector and the motion vector of the current block, thereby generating a motion vector difference. The decoding apparatus may generate the motion vector of the current block by adding the predicted motion vector and the motion vector difference.

The steps of performing motion compensation ( S504 , S605 ) and the steps of entropy encoding/decoding ( S505 , S601 ) of information associated with motion compensation shown in FIGS. 5 and 6 will be collectively described later, and the steps shown in FIGS. 7 and FIG. 8 show the steps of performing motion compensation (S703, S804) and the steps of entropy encoding/decoding (S704, S801).

Hereinafter, each step shown in FIGS. 7 and 8 will be described in detail.

First, the steps of deriving merge candidates ( S701 , S802 ) will be described.

The merging candidates of the current block may include at least one of spatial merging candidates, temporal merging candidates, and additional merging candidates. Here, the expression "deriving a spatial merging candidate" means a process of deriving a spatial merging candidate and adding the derived merging candidate to the merging candidate list.

Referring to FIG. 9 , spatial merging candidates of the current block may be derived from neighboring blocks adjacent to the current block X. The adjacent blocks adjacent to the current block X may include a block B1 adjacent to the upper end of the current block, a block A1 adjacent to the left end of the current block, a block B0 adjacent to the upper right corner of the current block, and a block B0 adjacent to the upper left of the current block. At least one of the block B2 adjacent to the corner, and the block A0 adjacent to the lower left corner of the current block.

To derive spatial merging candidates for the current block, it is determined whether each neighboring block adjacent to the current block is available for the derivation of spatial merging candidates for the current block. Such determinations may be made for adjacent blocks in a predetermined priority order. For example, in the example of FIG. 9, the availability of spatial merging candidates may be determined in the order of blocks A1, B1, B0, A0, and B2. The spatial merging candidates determined based on the availability determination order may be sequentially added to the merging candidate list of the current block.

FIG. 11 is a diagram illustrating an example of a process of adding a spatial merging candidate to a merging candidate list.

Referring to FIG. 11, four spatial merging candidates are derived from four adjacent blocks A1, B0, A0, and B2, and the derived spatial merging candidates may be sequentially added to a merging candidate list.

Optionally, spatial merging candidates may be derived based on at least one of the encoding parameters.

Here, the motion information of the spatial merging candidate may include three or more pieces of motion information, wherein the three or more pieces of motion information include L2 motion information and L3 motion information in addition to L0 motion information and L1 motion information . Here, there may be at least one reference picture list including, for example, L0, L1, L2, and L3.

Next, a method of deriving temporal merging candidates of the current block will be described.

The temporal merging candidates for the current block may be derived from reconstructed blocks included in co-located pictures of the current picture. The co-located picture may be a picture encoded/decoded before the current picture, and may be different from the current picture in time order.

The expression "deriving a temporal merging candidate" means a process of deriving a temporal merging candidate and adding the derived temporal merging candidate to a merging candidate list.

10, the temporal merging candidate for the current block may be derived from a block in a co-located picture (also referred to as a co-located picture) including the current picture, which is located outside a block that is spatially co-located with the current block X, or may be derived from A block that includes a position inside a block that is spatially co-located with the current block X in a co-located picture of the current picture derives a temporal merging candidate for the current block. The term "temporal merging candidate" may mean motion information of a co-located block. For example, the temporal merging candidate of the current block X may be derived from the block H adjacent to the lower left corner of the block C that is spatially co-located with the current block X, or the current block X may be derived from the block C3 including the middle position of the block C time merging candidates. Blocks H, C3, etc. used to derive temporal merging candidates of the current block are called co-located blocks (also referred to as co-located blocks).

When a temporal merging candidate of the current block can be derived from a block H including a location outside of block C, block H is set as a co-located block of the current block. In this case, the temporal merging candidate of the current block may be derived based on the motion information of block H. Conversely, when the temporal merging candidate of the current block cannot be deduced from block H, block C3 including a position located inside block C may be set as a co-located block of the current block. In this case, the temporal merging candidate of the current block may be derived based on the motion vector of block C3. When any temporal merging candidate for the current block cannot be derived from neither block H nor block C3 (eg, both block H and block C3 are intra-coded blocks), the temporal merging candidate for the current block may not be derived at all, Or the temporal merging candidates for the current block may be derived from blocks other than blocks H and C3.

Alternatively, for example, multiple temporal merging candidates for the current block may be derived from multiple blocks included within a co-located picture. That is, multiple temporal candidates for the current block can be derived from blocks H, C3, and so on.

FIG. 12 is a diagram illustrating an example of a process of adding a temporal merge candidate to a merge candidate list.

Referring to FIG. 12, when a temporal merging candidate is derived from the co-located block located at position H1, the derived temporal merging candidate may be added to the merging candidate list.

When the distance between the current picture including the current block and the reference picture of the current block is different from the distance between the co-located picture including the co-located block and the reference picture of the co-located block, the current picture may be obtained by scaling the motion vector of the co-located block The motion vector of the block's temporal merging candidate. Here, scaling of the motion vector may be performed based on at least one of the distance between the current picture and the reference picture of the current block and the distance between the co-located picture and the reference picture of the co-located block. For example, the motion of the temporal merging candidate of the current block may be derived by scaling the motion vector of the co-located block according to the ratio of the distance between the current picture and the reference picture of the current block to the distance between the co-located picture and the reference picture of the co-located block vector.

In addition, at least one of a temporal merging candidate, a co-located picture, a co-located block, a prediction list utilization flag, and a reference picture index may be derived based on at least one of encoding parameters of the current block, neighboring blocks, or co-located blocks.

The merging candidate list may be generated by generating at least one merging candidate of a spatial merging candidate and a temporal merging candidate and sequentially adding the derived merging candidates to the merging candidate list in the derived order.

Next, a method of deriving additional merge candidates for the current block will be described.

The term "additional merging candidate" may mean at least one of a modified spatial merging candidate, a modified temporal merging candidate, a combined merging candidate, and a predetermined merging candidate having a predetermined motion information value. Here, the expression "derivation of additional merging candidates" may mean a process of deriving additional merging candidates and adding the derived additional merging candidates to the merging candidate list.

The modified spatial merging candidate may mean a merging candidate obtained by modifying at least one item of motion information of the derived spatial merging candidate.

The modified temporal merging candidate may mean a modified merging candidate obtained by modifying at least one item of motion information of the derived temporal merging candidate.

Combining the merging candidates may mean by moving at least one of a spatial merging candidate, a temporal merging candidate, a modified spatial merging candidate, a modified temporal merging candidate, a combined merging candidate, and a predetermined merging candidate having a predetermined motion information value A merging candidate obtained by combining information, wherein a spatial merging candidate, a temporal merging candidate, a modified spatial merging candidate, a modified temporal merging candidate, a combined merging candidate, and a predetermined merging candidate with a predetermined motion information value are all included in the Merge candidate list.

Alternatively, a combined merging candidate may mean a merging candidate derived by combining motion information of at least one of the following merging candidates: not included in the merging candidate list but from which a spatial merging candidate and a temporal merging candidate can be derived. A spatial merging candidate and a temporal merging candidate derived from at least one of the blocks; a modified spatial merging candidate and a modified temporal merging candidate derived based on the spatial merging candidate and temporal merging candidate derived from the block; combining merging candidates; and predetermined merging candidates having predetermined motion information values.

Alternatively, the combined merge candidates may be derived using motion information obtained by performing entropy decoding on the bitstream in the decoder. In this case, the motion information used to derive the combined merge candidates may be entropy encoded into a bitstream in the encoder.

Combining merge candidates may mean combining bidirectional merge candidates. The combined bidirectional merge candidate is a merge candidate using bidirectional prediction, and the combined bidirectional merge candidate may be a merge candidate with L0 motion information and L1 motion information.

A merge candidate with a predetermined motion information value may be a zero merge candidate with a motion vector (0,0). A merge candidate having a predetermined motion information value may be set such that the merge candidate has the same value in the encoding device and the decoding device.

At least one of a modified spatial merging candidate, a modified temporal merging candidate, a combined merging candidate, and a merging candidate having a predetermined motion information value may be derived or generated based on at least one of coding parameters of the current block, neighboring blocks, or co-located blocks. One. In addition, at least one of the modified spatial merging candidate, the modified temporal merging candidate, the combined merging candidate, and the merging candidate having a predetermined motion information value may be merged based on at least one of coding parameters of the current block, the adjacent block, or the co-located block. Add to the merge candidate list.

The size of the merge candidate list may be determined based on encoding parameters of the current block, neighboring blocks, or co-located blocks, and may vary according to the encoding parameters.

Next, the steps of determining the motion information of the current block using the generated merge candidate list (S702, S803) will be described.

The encoder may select a merge candidate to be used for motion compensation of the current block from the merge candidate list through motion estimation, and may encode a merge candidate index merge_idx indicating the determined merge candidate to the bitstream.

In order to generate the prediction block of the current block, the encoder may select a merge candidate from a merge candidate list by using a merge candidate index, and determine motion information of the current block. Then, the encoder may perform motion compensation based on the determined motion information, thereby generating a prediction block of the current block.

The decoder may decode the merge candidate index in the received bitstream and determine the merge candidate indicated by the merge candidate index to be included in the merge candidate list. The determined merge candidate may be determined as motion information of the current block. The determined motion information is used for motion compensation of the current block. Here, the term "motion compensation" may have the same meaning as inter prediction.

Next, the steps of performing motion compensation using the motion vector or motion information (S504, S605, S703, S804) will be described.

The encoding apparatus and the decoding apparatus may calculate the motion vector of the current block by using the predicted motion vector and the motion vector difference. After calculating the motion vector, the encoding apparatus and the decoding apparatus may perform inter prediction or motion compensation using the calculated motion vector (S504, S605).

The encoding apparatus and the decoding apparatus may perform inter prediction or motion compensation using the determined motion information (S703, S804). Here, the current block may have motion information of the determined merge candidate.

The current block may have one (minimum value) to N (maximum value) motion vectors according to the prediction direction of the current block. One (minimum value) to N (maximum value) prediction blocks may be generated using the one to N motion vectors, and a final prediction block may be selected among the generated prediction blocks.

For example, when the current block has a motion vector, a prediction block generated using the motion vector (or motion information) is determined as the final prediction block of the current block.

Also, when the current block has multiple motion vectors (or pieces of motion information), multiple prediction blocks are generated using the multiple motion vectors (or the multiple pieces of motion information), and based on the multiple prediction blocks to determine the final predicted block of the current block. A plurality of reference pictures respectively including a plurality of prediction blocks respectively indicated by a plurality of motion vectors (or pieces of motion information) may be listed in different reference picture lists or in one reference picture list.

For example, a plurality of prediction blocks of the current block may be generated based on at least one of a spatial motion vector candidate, a temporal motion vector candidate, a motion vector having a predetermined value, and a combined motion vector candidate, and then may be based on the prediction blocks of the plurality of prediction blocks. The weighted sum is used to determine the final predicted block for the current block.

Alternatively, for example, a plurality of prediction blocks of the current block may be generated based on motion vector candidates indicated by a preset motion vector candidate index, and then a final prediction block of the current block may be determined based on a weighted sum of the plurality of prediction blocks . In addition, a plurality of prediction blocks may be generated based on motion vector candidates indicated by indexes within a predetermined motion vector candidate index range, and then a final prediction block of the current block may be determined based on a weighted sum of the plurality of prediction blocks.

The weight factor for each prediction block may be equal to 1/N (where N is the number of generated prediction blocks). For example, when two prediction blocks are generated, the weighting factor for each prediction block is 1/2. Similarly, when three prediction blocks are generated, the weighting factor for each prediction block is 1/3. When four prediction blocks are generated, the weighting factor for each prediction block may be 1/4. Alternatively, the final prediction block of the current block may be determined in a manner of applying different weighting factors to the respective prediction blocks.

The weighting factor for the prediction block may not be fixed but variable. The weighting factors used for prediction blocks may not be equal, but different. For example, when two prediction blocks are generated, the weighting factors for the two prediction blocks may be equal, such as (1/2, 1/2), or may be unequal, such as (1/3, 2/3) , (1/4, 3/4), (2/5, 3/5) or (3/8, 5/8). Weighting factors can be positive real-valued or negative real-valued values. That is, the value of the weighting factor may include negative real values, such as (-1/2, 3/2), (-1/3, 4/3) or (1-1/4, 5/4).

To apply variable weighting factors, one or more pieces of weighting factor information for the current block may be signaled through the bitstream. The weighting factor information may be signaled per prediction block, or may be signaled per reference picture. Optionally, multiple prediction blocks may share one weighting factor.

The encoding apparatus and the decoding apparatus may use a flag to determine whether to use a predicted motion vector (or predicted motion information) based on the predicted block list. For example, when the prediction block list utilization flag has a first value of one (1) for each reference picture list, the encoding apparatus and the decoding apparatus may perform inter prediction or motion compensation on the current block using the predicted motion vector of the current block. However, when the prediction block list utilization flag has the second value of zero (0), the encoding apparatus and the decoding apparatus may perform inter prediction or motion compensation on the current block without using the predicted motion vector of the current block. The first and second values of the predicted block list utilization flag may be set to 0 and 1, respectively, inversely. Expression 3 to Expression 5 are examples of the method of generating the final prediction block of the current block when the inter prediction indicator of the current block is PRED_BI, PRED_TRI or PRED_QUAD and when the prediction direction of each reference picture list is unidirectional .

[expression1]

P_BI=(WF_LO*P_LO+OFFSET_LO+WF_L1*P_L1+OFFSET_L1+RF)>>1

[expression 2]

P_TRI=(WF_LO*P_LO+OFFSET_LO+WF_L1*P_L1+OFFSET_L1+WF_L2*P_L2+OFFSET_L2+RF)/3

[expression 3]

P_QUAD=(WF_L0*P_L0+OFFSET_L0+WF_L1*P_L1+OFFSET_L1+WF_L2*P_L2+OFFSET_L2+WF_L3*P_L3+OFFSET_L3+RF)>>2

In Expression 1 to Expression 3, each of P_BI, P_TRI, and P_QUAD represents the final prediction block of the current block, and LX (X=0, 1, 2, 3) represents a reference picture list. WF_LX represents the weighting factor of the prediction block generated using the LX reference picture list. OFFSET_LX represents an offset value for a prediction block generated using the LX reference picture list. P_LX represents the prediction block of the current block generated using the motion vector (or motion information) of the LX reference picture list. RF means rounding factor, and it can be set to 0, a positive integer, or a negative integer. The LX reference picture list may include at least one of the following reference pictures: long-term reference pictures, reference pictures without filtering, reference pictures without sample adaptive offset, references without adaptive loop filter Picture, reference picture with only DF and AO, reference picture with DF and AL only, reference with sample Adaptive Offset and AL The picture, and the reference picture all passed through the deblocking filter, sample adaptive offset and adaptive loop filter. In this case, the LX reference picture list may be at least any one of the L2 reference picture list and the L3 reference picture list.

Even if there are multiple prediction directions for the predetermined reference picture list, the final prediction block of the current block may be obtained based on the weighted sum of the prediction blocks. In this case, weighting factors of a plurality of prediction blocks derived using one reference picture list may be equal, or may be different from each other.

At least the weight factor WF_LX or the offset OFFSET_LX of the plurality of prediction blocks may be an encoding parameter to be entropy encoded/decoded. Alternatively, for example, the weighting factors and offsets may be derived from previously encoded/decoded neighboring blocks adjacent to the current block. Here, the neighboring blocks adjacent to the current block may include at least one of a block for deriving a spatial motion vector candidate of the current block and a block for deriving a temporal motion vector candidate of the current block.

Further alternatively, for example, the weighting factor and offset may be determined based on the display order of the current picture (picture order count (POC)) and the POC of each reference picture. In this case, as the distance between the current picture and the reference picture increases, the value of the weighting factor or offset may decrease. That is, when the current picture and the reference picture are close to each other, a larger value may be set as the weighting factor or offset. For example, when the distance between the POC of the current picture and the POC of the L0 reference picture is 2, the value of the weighting factor applied to the prediction block generated using the L0 reference picture may be set to 1/3. Meanwhile, when the difference between the POC of the current picture and the POC of the L0 reference picture is 1, the value of the weighting factor applied to the prediction block generated using the L0 reference picture may be set to 2/3. As described above, the weighting factor or offset may be inversely proportional to the difference between the display order (POC) of the current picture and the display order (POC) of the reference picture. Alternatively, the weighting factor or offset may be proportional to the difference between the display order (POC) of the current picture and the display order (POC) of the reference picture.

Optionally, for example, at least one of the weighting factor and the offset may be entropy encoded/decoded based on the at least one encoding parameter. Additionally, a weighted sum of prediction blocks may be calculated based on at least one encoding parameter.

The weighted sum of multiple prediction blocks may be applied to only a partial region of the prediction block. The partial area may be a boundary area adjacent to the boundary of each prediction block. In order to apply the weighted sum to only the partial region as described above, the weighted sum may be calculated sub-block by sub-block in each prediction block.

In a block having a block size indicated by the region information, inter prediction or motion compensation may be performed for a subblock smaller than the block by using the same prediction block or the same final prediction block.

In a block having a block depth indicated by region information, inter prediction or motion compensation may be performed for a subblock having a block depth deeper than that of the block by using the same prediction block or the same final prediction block.

In addition, when the weighted sum of prediction blocks is calculated by motion vector prediction, the weighted sum may be calculated using at least one of the motion vector candidates included in the motion vector candidate list, and the calculation result may be used as the final prediction of the current block piece.

For example, a prediction block may be generated using only spatial motion vector candidates, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as the final prediction block of the current block.

For example, a prediction block may be generated using the spatial motion vector candidate and the temporal motion vector candidate, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as a final prediction block of the current block.

For example, a prediction block may be generated using only the combined motion vector candidates, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as the final prediction block of the current block.

For example, a prediction block may be generated using only motion vector candidates indicated by a specific index, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as a final prediction block of the current block.

For example, a prediction block may be generated using only motion vector candidates indicated by indexes within a predetermined index range, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as a final prediction block of the current block.

When the weighted sum of the prediction blocks is calculated using the merge mode, the weighted sum may be calculated using at least one merge candidate among the merge candidates included in the merge candidate list, and the calculation result may be used as the final prediction block of the current block.

For example, a prediction block may be generated using only spatial merging candidates, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as the final prediction block of the current block.

For example, the spatial merging candidate and the temporal merging candidate may be used to generate a prediction block, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as the final prediction block of the current block.

For example, the prediction block may be generated using only the combined merge candidates, a weighted sum of the prediction blocks may be generated, and the calculated weighted sum may be used as the final prediction block of the current block.

For example, a prediction block may be generated using only merge candidates indicated by a specific index, a weighted sum of the prediction blocks may be generated, and the calculated weighted sum may be used as the final prediction block of the current block.

For example, a prediction block may be generated using only merge candidates indicated by indexes within a predetermined index range, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as a final prediction block of the current block.

In the encoder and decoder, motion compensation may be performed using the motion vector or motion information of the current block. At this time, at least one prediction block may be used to determine a final prediction block as a result of motion compensation. Here, the current block may mean at least one of a current coding block and a current prediction block.

The final prediction block of the current block may be generated by performing overlapping block motion compensation on the boundary region of the current block.

The boundary area of the current block may be an area located within the current block and adjacent to a boundary between the current block and neighboring blocks of the current block. The boundary area of the current block may include at least one of an upper boundary area, a left boundary area, a lower boundary area, a right boundary area, an upper right area, a lower right area, an upper left area, and a lower left area. The boundary area of the current block may be an area corresponding to a portion of the prediction block of the current block.

Overlapping block motion compensation may mean a process of performing motion compensation by calculating a weighted sum of a prediction block corresponding to a boundary region of the current block and a prediction block generated using motion information of encoded/decoded blocks adjacent to the current block.

The calculation of the weighted sum may be performed sub-block by sub-block by dividing the current block into a plurality of sub-blocks. That is, motion compensation of the current block may be performed sub-block by sub-block using motion information of encoded/decoded sub-blocks adjacent to the current block. A sub-block may mean a subordinate block of the current block.

In addition, when calculating the weighted sum, the first prediction block generated for each sub-block of the current block by using the motion information of the current block, and the first prediction block generated by using the motion information of the adjacent sub-blocks that are spatially adjacent to the current block can be used. Two prediction blocks. In this case, the expression "using motion information" means "deriving motion information". The first prediction block may mean a prediction block generated by using motion information of the encoding/decoding target subblock within the current block. The second prediction block may be a prediction block generated by using motion information of adjacent subblocks that are spatially adjacent to the encoding/decoding target subblock within the current block.

A weighted sum of the first prediction block and the second prediction block may be used to generate a final prediction block of the current block. That is, overlapping block motion compensation consists in finding the final prediction block of the current block using the motion information of the current block and the motion information of another block.

In addition, when at least one of Advanced Motion Vector Prediction (AMVP) mode, merge mode, affine motion compensation mode, decoder-side motion vector derivation mode, adaptive motion vector resolution mode, local illumination compensation mode, bidirectional optical flow mode When used, the current block may be divided into sub-blocks, and overlapping block motion compensation may be performed sub-block by sub-block.

When merge mode is used for motion compensation, overlapping block motion compensation may be performed on at least one of improved temporal motion vector predictor (ATMVP) candidates and spatial-temporal motion vector predictor (STMVP) candidates.

Details of overlapping block motion compensation will be described later with reference to FIGS. 13 to 24 .

Next, the process of performing entropy encoding/entropy decoding on the information associated with motion compensation ( S505 , S601 , S704 , S801 ) will be described.

The encoding apparatus may entropy encode the information associated with the motion compensation into the bitstream, and the decoder may decode the information associated with the motion compensation included in the bitstream. The information associated with motion compensation that is a target of entropy encoding or entropy decoding may include at least one of the following: inter prediction indicator inter_pred_idc, reference picture indices ref_idx_l0, ref_idx_l1, ref_idx_l2 and ref_idx_l3, motion vector candidate index mvp_l0_idx, mvp_l1_idx, mvp_l2_idx and mvp_l3_idx, motion vector difference, skip mode use/unuse information cu_skip_flag, merge mode use/unuse information merge_flag, merge index information merge_index, weight factors wf_l0, wf_l1, wf_l2 and wf_l3, and offset value offset_10, offset_11, offset_12 and offset_13.

The inter prediction indicator may mean the prediction direction of the inter prediction, the number of prediction directions, or both the prediction direction and the number of prediction directions of the inter prediction when the current block is encoded/decoded by the inter prediction. For example, the inter prediction indicator may indicate unidirectional prediction or multidirectional prediction (such as bidirectional prediction, three-way prediction, and four-way prediction). The inter prediction indicator may indicate the number of reference pictures used to generate the prediction block of the current block. Optionally, one reference picture can be used for prediction in multiple directions. In this case, M reference pictures are used to perform prediction in N directions (where N>M). The inter prediction indicator may also mean the number of prediction blocks used for inter prediction or motion compensation of the current block.

The reference picture indicator may indicate one direction PRED_LX, two directions PRED_BI, three directions PRED_TRI, four directions PRED_QUAD, or more directions according to the number of prediction directions of the current block.

The prediction list of a specific reference picture list uses a flag to indicate whether to use the reference picture list to generate the prediction block.

For example, when the prediction list utilization flag of a specific reference picture list has a first value of one (1), this means that the prediction block is generated using the reference picture list. When the prediction list utilization flag has the second value zero (0), it means that the prediction block is not generated using the reference picture list. Here, the first value and the second value of the prediction list utilization flag may be set to 0 and 1, respectively, inversely.

That is, when the prediction list utilization flag of the specific reference picture list has the first value, the prediction block of the current block may be generated using the motion information corresponding to the reference picture list.

The reference picture index may indicate a specific reference picture that exists in the reference picture list and is referenced by the current block. For each reference picture list, one or more reference picture indices may be entropy encoded/decoded. The current block may be motion compensated using one or more reference picture indices.

The motion vector candidate index indicates the motion vector candidate of the current block among the motion vector candidates included in the motion vector candidate list prepared for each reference picture list or each reference picture index. At least one or more motion vector candidate indices may be entropy encoded/entropy decoded for each motion vector candidate list. The current block may be motion compensated using at least one or more motion vector candidate indices.

The motion vector difference represents the difference between the current motion vector and the predicted motion vector. For each motion vector candidate list generated for each reference picture list or each reference picture index for the current block, one or more motion vector differences may be entropy encoded/entropy decoded. The current block may be motion compensated using one or more motion vector differences.

Regarding the skip mode use/unuse information cu_skip_flag, when the skip mode use/unuse information cu_skip_flag has a first value of one (1), the skip mode can be used. Conversely, when the skip mode use/unuse information cu_skip_flag has the second value zero (0), the skip mode may not be used. Motion compensation may be performed on the current block using the skip mode according to the skip mode usage/non-use information.

Regarding the merge mode use/unuse information merge_flag, when the merge mode use/unuse information merge_flag has a first value of one (1), the merge mode can be used. Conversely, when the merge mode use/unuse information merge_flag has the second value of zero (0), the merge mode may not be used. Motion compensation may be performed on the current block using the merge mode according to the merge mode usage/non-use information.

The merge index information merge_index may mean information indicating merge candidates within the merge candidate list.

Alternatively, the merge index information may mean information about a merge index.

In addition, the merge index information may indicate a reconstruction block for deriving a merge candidate among reconstruction blocks that are spatially/temporally adjacent to the current block.

The merge index information may indicate one or more pieces of motion information that the merge candidate has. For example, when the merge index information has a first value of zero (0), the merge index information may indicate the first merge candidate listed as the first entry in the merge candidate list; when the merge index information has a second value of one (1) , the merge index information may indicate the second merge candidate listed as the second entry in the merge candidate list; when the merge index information has a third value of two (2), the merge index information indicates that the merge candidate list is listed as the third item Destination third merge candidate. Similarly, when the merge index information has values from the fourth value to the Nth value, the merge index information may indicate merge candidates listed at positions according to the order of the values in the merge candidate list. Here, N may be 0 or a positive integer.

Motion compensation may be performed on the current block using the merge mode based on the merge mode index information.

When two or more prediction blocks are generated during motion compensation of the current block, a final prediction block of the current block may be determined based on a weighted sum of the prediction blocks. When calculating the weighted sum, the weighting factor, the offset, or both the weighting factor and the offset may be applied to each prediction block. The weighted sum factors (eg weighting factors and offsets) used to calculate the weighted sum may be entropy encoded/entropy decoded in an amount corresponding to at least one of the following items: Encoding/entropy decoding: reference picture list, reference picture, motion vector candidate index, motion vector difference, motion vector, skip mode used/unused information, merge mode used/unused information, merge index information. In addition, the weighted sum factor for each prediction block may be entropy encoded/entropy decoded based on the inter prediction indicator. The weighted sum factor may include at least one of a weighted factor and an offset.

The information associated with motion compensation may be entropy-encoded/entropy-decoded on a block-by-block basis, or may be entropy-encoded/entropy-decoded in units of higher-level units. For example, information associated with motion compensation may be entropy encoded/entropy decoded on a block-by-block basis (eg, CTU-by-CTU, CU-by-CU, or PU-by-PU). Alternatively, the information associated with motion compensation may be entropy-encoded/entropy-decoded in units of higher-level units such as video parameter sets, sequence parameter sets, picture parameter sets, adaptation parameter sets, or slice headers.

The information associated with motion compensation may be entropy encoded/entropy decoded based on a difference in motion compensation information, wherein the difference in motion compensation information indicates a difference between the information associated with motion compensation and a predicted value of the information associated with motion compensation .

Instead of entropy coding/entropy encoding the information associated with motion compensation of the current block, the information associated with motion compensation of the coded/decoded block adjacent to the current block may be used as the information associated with motion compensation of the current block Entropy decoding.

At least one piece of information associated with motion compensation may be derived based on at least one of the encoding parameters.

The bitstream may be decoded based on at least one of the encoding parameters to generate at least one piece of information associated with motion compensation. Instead, at least one piece of information associated with motion compensation may be entropy encoded into the bitstream based on at least one of the encoding parameters.

At least one piece of information associated with motion compensation may include motion vector, motion vector candidate, motion vector candidate index, motion vector difference, motion vector predictor, skip mode use/unuse information skip_flag, merge mode use/unuse information merge_flag , at least one of merge index information merge_index, motion vector resolution information, overlapping block motion compensation information, local illumination compensation information, affine motion compensation information, decoder side motion vector derivation information, and bidirectional optical flow information. Here, decoder-side motion vector derivation may mean pattern-matched motion vector derivation.

The motion vector resolution information may be information indicating which specific resolution is used for at least one of the motion vector and the motion vector difference. Here, resolution can mean precision. The specific resolution can be set to 16-pixel (16-pel) unit, 8-pixel (8-pel) unit, 4-pixel (4-pel) unit, integer-pixel (integer-pel) unit, 1 /2-pixel (1/2-pel) unit, 1/4-pixel (1/4-pel) unit, 1/8-pixel (1/8-pel) unit, 1/16-pixel (1/16 -pel) unit, at least any one of 1/32-pixel (1/32-pel) unit and 1/64-pixel (1/64-pel) unit.

The overlapping block motion compensation information may be information indicating whether motion vectors of neighboring blocks spatially adjacent to the current block are to be additionally used to calculate a weighted sum of prediction blocks of the current block during motion compensation of the current block.

The local luminance compensation information may be information indicating whether any one of the weighting factor and the offset is applied when the prediction block of the current block is generated. Here, at least one of the weighting factor and the offset may be a value calculated based on the reference block.

The affine motion compensation information may be information indicating whether an affine motion model is to be used for motion compensation of the current block. Here, the affine motion model may be a model that divides one block into a plurality of sub-blocks using a plurality of parameters and calculates motion vectors of the sub-blocks using a representative motion vector.

The decoder-side motion vector derivation information may be information indicating whether a motion vector required for motion compensation is derived by the decoder and then used in the decoder. From the decoder side motion vector derivation information, the information associated with the motion vector may not be entropy encoded/entropy decoded. When the decoder-side motion vector derivation information indicates that the motion vector is derived by the decoder and then used in the decoder, the information associated with the merge mode may be entropy encoded/entropy decoded. That is, the decoder-side motion vector derivation information may indicate whether merge mode is used in the decoder.

The bidirectional optical flow information may be information indicating whether the motion vector is modified pixel by pixel or subblock by subblock and then whether the modified motion vector is used for motion compensation. According to the bidirectional optical flow information, the motion vector may not be entropy encoded/entropy decoded on a per-pixel or per-subblock basis. The modification of the motion vector means converting the value of the block-based motion vector to the value of the pixel-based motion vector or the value of the sub-block-based motion vector.

The current block may be motion compensated based on at least one piece of information associated with motion compensation, and the at least one piece of information associated with motion compensation may be entropy encoded/entropy decoded.

When the information associated with motion compensation is entropy encoded/entropy decoded, binarization methods such as truncated Rice binarization method, K-order exponential Golomb binarization method, finite K-order exponential Golomb binarization method may be used , fixed-length binarization method, unary binarization method, and truncated unary binarization method.

When the information associated with motion compensation is entropy encoded/entropy decoded, the context model may be determined based on at least one of the following information: associated with motion information of neighboring blocks adjacent to the current block or region information of neighboring blocks information; previously encoded/decoded information associated with motion compensation or previously encoded/decoded region information; information about the depth of the current block; information about the size of the current block.

Alternatively, when the information associated with motion compensation is entropy encoded/entropy decoded, entropy encoding/entropy may be performed by using at least one of the following information as a predictor of the information associated with motion compensation of the current block. Entropy decoding: information associated with motion compensation of neighboring blocks, previously encoded/decoded information associated with motion compensation, information about the depth of the current block, and information about the size of the current block.

Hereinafter, details of overlapping block motion compensation may be described with reference to FIGS. 13 to 24 .

FIG. 13 is a diagram illustrating an example of performing overlapping block motion compensation on a sub-block-by-sub-block basis.

Referring to FIG. 13 , the shaded blocks are the regions where the overlapping block motion compensation is to be performed. The shaded blocks may include sub-blocks of the current block located at the boundary or sub-blocks in the current block. The area demarcated by the thick solid line may be the current block.

Arrows indicate that motion information of neighboring sub-blocks is used for motion compensation of the current sub-block. Here, the area where the tail of the arrow is located may mean (1) the adjacent sub-block adjacent to the current block or the adjacent sub-block adjacent to the current sub-block within the current block. The area where the arrow head is located may mean the current sub-block within the current block.

For shadow blocks, a weighted sum of the first prediction block and the second prediction block may be calculated. The motion information of the current sub-block within the current block may be used as motion information for generating the first prediction block. At least one or both of motion information of adjacent sub-blocks adjacent to the current block and motion information of adjacent sub-blocks adjacent to the current sub-block and included in the current block may be used as parameters for generating the second prediction block. sports information.

In addition, in order to improve coding efficiency, the motion information used to generate the second prediction block may include an upper block, a left block, a lower block, a right block, an upper right block, a lower right block, and an upper left block of the current subblock within the current block. and motion information for at least one of the lower left squares. Neighboring sub-blocks that can be used to generate the second prediction block may be determined according to the position of the current sub-block. For example, when the current subblock is located at the upper boundary of the current block, at least one neighboring subblock among neighboring subblocks located on the upper side, the upper right side, and the upper left side of the current subblock may be used. When the current subblock is located at the left boundary of the current block, at least one neighboring subblock among neighboring subblocks located on the left side, the upper left side, and the lower left side of the current subblock may be used.

Here, blocks located on the upper side, left side, lower side, right side, upper right side, lower right side, upper left side, and lower left side of the current sub-block may be referred to as upper adjacent sub-block, left adjacent sub-block, lower adjacent sub-block, respectively Sub-near-block, right-adjacent sub-block, upper-right adjacent sub-block, lower-right adjacent sub-block, upper-left adjacent sub-block, and lower-left adjacent sub-block.

Meanwhile, in order to reduce the computational complexity, the motion information for generating the second prediction block may be determined according to the size of the motion vector of the adjacent sub-block adjacent to the current block or the adjacent sub-block adjacent to the current sub-block within the current block. Variety.

For example, when the adjacent subblock is a bidirectionally predicted subblock, the sizes of the motion vector in the L0 direction and the L1 direction are compared, and only the motion information in the direction of the larger size may be used to generate the second prediction block.

Alternatively, for example, the sum of absolute values of the x component and the y component of the motion vector in the L0 direction and the sum of the absolute values of the x component and the y component of the L1 direction of the motion vector are calculated. Then, only motion vectors equal to or greater than a predetermined value may be used to generate the second prediction block. Here, the predetermined value may be 0 or a positive integer. The predetermined value may be a value determined based on information signaled from the encoder to the decoder. Alternatively, the predetermined value may not be signaled, but may be a value that is identically set in the encoder and decoder.

In addition, in order to reduce computational complexity, the motion information for generating the second prediction block may vary according to the size and direction of the motion vector of the current sub-block.

For example, the absolute values of the x-component and the y-component of the motion vector of the current subblock may be compared. When the absolute value of the x component is larger, motion information of at least one of the left subblock and the right subblock of the current subblock may be used to generate the second prediction block.

Alternatively, for example, the absolute values of the x-component and the y-component of the motion vector of the current sub-block may be compared. When the absolute value of the y component is larger, the motion information of at least one of the upper sub-block and the lower sub-block of the current sub-block may be used to generate the second prediction block.

Optionally, for example, when the absolute value of the x-component of the motion vector of the current sub-block is equal to or greater than a predetermined value, the motion information of at least one of the left sub-block and the right sub-block of the current sub-block may be used to generate the first sub-block. Two prediction blocks. Here, the predetermined value may be zero (0) or a positive integer. The predetermined value may be determined based on information signaled from the encoder to the decoder, or may be set identically in the encoder and decoder.

Further optionally, for example, when the absolute value of the y-component of the motion vector of the current sub-block is equal to or greater than a predetermined value, the motion information of at least one of the upper sub-block and the lower sub-block of the current sub-block may be used to generate the second sub-block. prediction block. Here, the predetermined value may be zero (0) or a positive integer. The predetermined value may be determined based on information signaled from the encoder to the decoder, or may be set identically in the encoder and decoder.

Here, the sub-block may have a size of N×M, where N and M are positive integers. N and M may or may not be equal. For example, the size of the sub-block may be 4x4 or 8x8. The information of the size of the sub-block may be entropy encoded/entropy decoded at the sequence unit level.

The size of the sub-block may be determined based on the size of the current block. For example, when the size of the current block is K samples or less, the size of the sub-block may be 4×4. Meanwhile, when the size of the current block is larger than K samples, the size of the sub-block may be 8×8. Here, K is a positive integer such as 256.

Here, the information of the size of the sub-block may be entropy-encoded/entropy-decoded in units of at least any one of a sequence, a picture, a slice, a parallel block, a CTU, a CU, and a PU. In addition, the size of the sub-block may be a predetermined value preset in the encoder and the decoder.

The sub-blocks may have a square shape or a rectangular shape. For example, when the current block has a square shape or a rectangular shape, the sub-block may have a square shape.

For example, when the current block has a rectangular shape, the sub-block may have a rectangular shape.

Here, the information of the shape of the sub-block may be entropy-encoded/entropy-decoded in units of at least one of a sequence, a picture, a slice, a parallel block, a CTU, a CU, and a PU. In addition, the shape of the sub-block may be a predetermined shape preset in the encoder and the decoder.

FIG. 14 is a diagram illustrating an example of performing overlapping block motion compensation using motion information of sub-blocks of a co-located block. To improve coding efficiency, motion information of co-located sub-blocks that are spatially co-located with the current block in the co-located picture or reference picture may be used to generate the second prediction block.

Referring to FIG. 14 , motion information of sub-blocks that are temporally adjacent to the current block within the co-located block may be used to perform overlapping block motion compensation on the current sub-block. The region in which the tail of the arrow is located may be a sub-block within a co-located block. The area where the arrow head is located may be the current sub-block within the current block.

In addition, motion information for at least one of a collocated sub-block in a collocated picture, a neighboring sub-block that is spatially adjacent to the current block, and a neighboring sub-block that is spatially adjacent to the current sub-block within the current block may be used to generate The second prediction block.

FIG. 15 is a diagram illustrating an example of performing overlapping block motion compensation using motion information of blocks adjacent to a boundary of a reference block. To improve coding efficiency, a reference block in a reference picture may be identified by using at least one of a motion vector of the current block and a reference picture index, and motion information of neighboring blocks adjacent to the boundary of the identified reference block may be used to generate The second prediction block. Here, the adjacent blocks may include coded/decoded blocks adjacent to sub-blocks of the reference block located at the right or left boundary.

Referring to FIG. 15 , motion information of encoded/decoded blocks adjacent to the lower or right boundary of the reference block may be used to perform overlapping block motion compensation on the current sub-block.

In addition, motion information of coded/decoded blocks adjacent to the lower or right boundary of the reference block, motion information of adjacent sub-blocks that are spatially adjacent to the current block, and spatially adjacent to the current sub-block within the current block At least one of the motion information of adjacent neighboring sub-blocks may be used to generate the second prediction block.

In order to improve coding efficiency, motion information of at least one merging candidate among a plurality of merging candidates included in the merging candidate list may be used to generate the second prediction block. Here, the merge candidate list may be a list used in a merge mode among a plurality of inter prediction modes.

For example, spatial merging candidates in the merging candidate list may be used as motion information for generating the second prediction block.

Alternatively, for example, temporal merging candidates in the merging candidate list may be used as motion information for generating the second prediction block.

Further alternatively, for example, combined merging candidates in the merging candidate list may be used as motion information for generating the second prediction block.

Optionally, in order to improve coding efficiency, at least one motion vector among a plurality of motion vector candidates included in the motion vector candidate list may be used as a motion vector for generating the second prediction block. Here, the motion vector candidate list may be a list used in AMVP mode among a plurality of inter prediction modes.

For example, spatial motion vector candidates in the motion vector candidate list may be used as motion information for generating the second prediction block.

Alternatively, for example, temporal motion vector candidates in the motion vector candidate list may be used as motion information for generating the second prediction block.

When at least one of a merge candidate and a motion vector candidate is used as motion information required for generating the second prediction block, a region to which the overlapping block motion compensation is applied may be set differently. The area to which the overlapping block motion compensation is applied may be the area of the block that is adjacent to the boundary (ie, the sub-block of the block that is located at the boundary) or the area of the block that is not adjacent to the boundary (ie, the sub-block of the block that is not located at the boundary. piece).

When overlapping block motion compensation is applied to a region of a block that is not adjacent to a boundary, at least one of a merge candidate and a motion vector candidate may be used as motion information required for generating the second prediction block.

For example, overlapping block motion compensation may be performed for a region of a block that is not adjacent to a boundary by using spatial merging candidates or spatial motion vector candidates as motion information.

Alternatively, for example, overlapping block motion compensation may be performed for an area of a block that is not adjacent to a boundary by using a temporal merge candidate or a temporal motion vector candidate as motion information.

Further alternatively, for example, overlapping block motion compensation may be performed for a region of the block adjacent to the lower boundary or the right boundary by using spatial merging candidates or spatial motion vector candidates as motion information.

Further alternatively, for example, overlapping block motion compensation may be performed for a region of the block adjacent to the lower boundary or the right boundary by using a temporal merge candidate or a temporal motion vector candidate as motion information.

In addition, in order to improve coding efficiency, motion information derived from a specific block within a merge candidate list or a motion vector candidate list may be used for overlapping block motion compensation for a specific region.

For example, when motion information of the upper-right neighboring block of the current block is included in the merge candidate list or the motion vector candidate list, the motion information may be used for overlapping block motion compensation of the right boundary region of the current block.

Alternatively, for example, when the motion information of the lower left neighboring block of the current block is included in the merge candidate list or the motion vector candidate list, the motion information may be used for overlapping block motion compensation of the lower boundary area of the current block.

FIG. 16 is a diagram illustrating an example of performing overlapping block motion compensation on a sub-block group-by-sub-block group basis. To reduce computational complexity, sub-block-based overlapping block motion compensation may be performed in units of a sub-block set including one or more sub-blocks. The unit of the sub-block set may mean the unit of the sub-block group.

Referring to FIG. 16 , the shaded areas marked with lines may be referred to as sub-block groups. Arrows mean that the motion information of adjacent neighboring sub-blocks can be used for motion compensation of the current sub-block group. The area where the tail of the arrow is located may be (1) adjacent sub-blocks adjacent to the current block, (2) adjacent sub-block groups adjacent to the current block, or (3) adjacent sub-blocks within the current block adjacent to the current sub-block. Adjacent sub-block groups. In addition, the area where the arrow head is located may mean the current sub-block group within the current block.

For each sub-block group, a weighted sum of the first prediction block and the second prediction block may be calculated. The motion information of the current sub-block group within the current block may be used as motion information for generating the first prediction block. Here, the motion information of the current sub-block group within the current block may be any one of an average value, a median value, a minimum value, a maximum value, and a weighted sum of the motion information of each sub-block within the current sub-block group. At least one of motion information of adjacent sub-blocks adjacent to the current block, motion information of adjacent sub-block groups adjacent to the current block, and motion information of adjacent sub-blocks adjacent to the current sub-block within the current block may be Used as motion information for generating the second prediction block. Here, the motion information of the adjacent sub-block group adjacent to the current block may be any of the average value, median, minimum value, maximum value and weighted sum of the motion information of each sub-block included in the adjacent sub-block group One.

Here, the current block may include one or more sub-block groups. The horizontal size of one sub-block group may be equal to or smaller than the horizontal size of one current sub-block. In addition, the vertical size of one subblock group may be equal to or smaller than the vertical size of one current subblock. In addition, overlapping block motion compensation may be performed for at least one sub-block among a plurality of sub-blocks of the current block located at the upper boundary and the left boundary.

Since blocks adjacent to the lower and right boundaries within the current block have not been encoded/decoded, overlapping block motion compensation may not be performed for at least one subblock among the plurality of subblocks located at the lower and right boundaries within the current block. Alternatively, since the blocks adjacent to the lower boundary and the right boundary within the current block have not been encoded/decoded, the motion information of the upper block of the current subblock, the motion information of the left block, the motion of the upper left block can be obtained by using the motion information of the current subblock. At least one of the information, the motion information of the lower left block, and the motion information of the upper right block, overlapping block motion compensation is performed for at least any one of a plurality of sub-blocks located at the left and right boundaries within the current block.

In addition, when the current block is to be predicted in merge mode and has at least one of an improved temporal motion vector prediction candidate and a spatio-temporal motion vector prediction candidate, for multiple sub-blocks located at the lower boundary and the right boundary within the current block For at least one sub-block of , overlapping block motion compensation may not be performed.

In addition, when the current block is to be predicted in the decoder-side motion vector derivation mode or the affine motion compensation mode, overlapping blocks may not be performed for at least one sub-block among a plurality of sub-blocks located at the lower boundary and the right boundary within the current block motion compensation.

Additionally, overlapping block motion compensation may be performed for at least one of the color components of the current block. The color components may include at least one of a luma component and a chroma component.

Optionally, overlapping block motion compensation may be performed according to the current block's inter prediction indicator. That is, when the current block is to be uni-predicted, bi-predicted, tri-predicted, and/or quad-predicted, overlapping block motion compensation may be performed. Alternatively, overlapping block motion compensation may be performed only when the current block is uni-directionally predicted. Further alternatively, overlapping block motion compensation may be performed only when the current block is bi-directionally predicted.

FIG. 17 is a diagram illustrating an example of pieces of motion information used for overlapping block motion compensation.

The maximum number of pieces of motion information for generating the second prediction block may be K. That is, at most K second prediction blocks can be generated and used for overlapping block motion compensation. Here, K may be zero (0) or a positive integer, eg, 1, 2, 3, or 4.

For example, when the second prediction block is generated using motion information of neighboring sub-blocks adjacent to the current block, at most two pieces of motion information may be derived from at least one of the upper block and the right block. When the second prediction block is generated based on the motion information of the adjacent sub-blocks adjacent to the current sub-block in the current block, the upper block, the left block, the right block, the upper-left block, the upper-right block, the lower-left block of the current sub-block may be At least one of the square and the lower right square derives up to four pieces of motion information. Here, the expression "deriving motion information" may mean a process of generating a second prediction block using the derived motion information and then performing overlapping block motion compensation using the generated second prediction block.

17 , in order to improve coding efficiency, when motion compensation is performed for at least one of a plurality of sub-blocks located at the upper and left boundaries within the current block, up to three pieces of motion information may be derived for generating the second prediction block. That is, motion information for generating the second prediction block may be derived based on 3 connections.

For example, when motion compensation is performed on a sub-block located at an upper boundary within the current block, it may be derived from at least one of an upper, upper-left, and upper-right adjacent block among adjacent sub-blocks adjacent to the current block sports information.

For example, when motion compensation is performed on a subblock located at the left boundary within the current block, at least one of a left adjacent block, an upper left adjacent block, and a lower left adjacent block among adjacent subblocks adjacent to the current block may be obtained from at least one Derive motion information.

In addition, when motion compensation is performed for a subblock located at the upper left boundary within the current block, it may be derived from at least one of an upper adjacent block, a left adjacent block, and an upper left adjacent block among adjacent subblocks adjacent to the current block sports information.

In addition, when motion compensation is performed for a sub-block located at the upper right boundary within the current block, it may be derived from at least one of an upper adjacent block, an upper left adjacent block, and an upper right adjacent block among adjacent sub-blocks adjacent to the current block sports information.

Meanwhile, when motion compensation is performed for a sub-block located at the lower left boundary within the current block, at least one of a left-side adjacent block, an upper-left adjacent block, and a lower-left adjacent block among adjacent sub-blocks adjacent to the current block may be selected from Derive motion information.

Optionally, in order to improve coding efficiency, when motion compensation is performed for a sub-block within the current block that is not at least one of the multiple sub-blocks located at the upper boundary and the left boundary, a maximum of 8 pieces of motion information may be derived to generate the first sub-block. Two prediction blocks. That is, motion information for generating the second prediction block may be derived based on 8 connections.

For example, for a subblock within the current block, it can be selected from the upper adjacent block, left adjacent block, lower adjacent block, right adjacent block, upper left adjacent block included in the current block as adjacent subblocks adjacent to the current subblock The motion information is derived from at least one of a square neighbor block, a lower left neighbor block, a lower right neighbor block, and an upper right neighbor block.

Additionally, motion information used to generate the second prediction block may be derived from the co-located sub-blocks within the co-located picture. In addition, motion information for generating the second prediction block may be derived from coded/decoded blocks within the reference picture that are adjacent to the lower and right boundaries of the reference block.

In addition, in order to improve coding efficiency, the number of pieces of motion information for generating the second prediction block may be determined according to the size and direction of the motion vector.

For example, when the sum of the absolute values of the x-component and the y-component of the motion vector is equal to or greater than J, up to L pieces of motion information may be used. Conversely, when the sum of the absolute values of the x-component and the y-component of the motion vector is less than J, at most P pieces of motion information may be used. In this case, J, L and P are zero or positive integers. L and P are preferably different values. However, L and P may be equal to each other.

In addition, when the current block is to be predicted in merge mode and when at least one of the improved temporal motion vector prediction candidate and the spatio-temporal motion vector prediction candidate is used, at most K pieces of motion information may be used to generate the second prediction piece. Here, K can be zero or a positive integer, such as 4.

In addition, when the current block is to be predicted in the decoder-side motion vector derivation mode, at most K pieces of motion information may be used to generate the second prediction block. Here, K can be zero or a positive integer, such as 4.

In addition, when the current block is to be predicted in the affine motion compensation mode, at most K pieces of motion information may be used to generate the second prediction block. Here, K can be zero or a positive integer, such as 4.

18 and 19 are diagrams illustrating an order of deriving motion information for generating a second prediction block. The motion information for generating the second prediction block may be derived in a predetermined order preset in the encoder and the decoder.

Referring to FIG. 18 , motion information may be derived from neighboring blocks of a current block in the order of an upper block, a left block, a lower block, and a right block.

Referring to FIG. 19 , in order to improve coding efficiency, an order of deriving motion information for generating the second prediction block may be determined based on the position of the current subblock.

For example, when the motion information is derived for a current subblock located at the upper boundary within the current block, it may be in accordance with (1) the upper adjacent block, (2) the upper left adjacent block, and (3) which are adjacent subblocks adjacent to the current block. The order of the upper right neighboring blocks derives motion information from neighboring sub-blocks.

In addition, when the motion information is derived for the current sub-block located at the left boundary within the current block, it may be determined as (1) the left-side neighboring block, (2) the upper-left neighboring block, and (3) as neighboring sub-blocks adjacent to the current block. ) The order of the lower left neighboring blocks derives motion information from neighboring sub-blocks.

In addition, when the motion information is derived for the current subblock located at the upper left boundary within the current block, it may be in accordance with (1) the upper adjacent block, (2) the left adjacent block, and (3) which are adjacent subblocks adjacent to the current block. The order of the upper left neighboring blocks derives motion information from neighboring sub-blocks.

In addition, when the motion information is derived for the current subblock located at the upper right boundary within the current block, it may be in accordance with (1) the upper adjacent block, (2) the upper left adjacent block, and (3) which are adjacent subblocks adjacent to the current block. The order of the upper right neighboring blocks derives motion information from neighboring sub-blocks.

In addition, when the motion information is derived for the current sub-block located at the lower right boundary of the current block, it may be performed according to (1) the left-side neighboring block, (2) the upper-left neighboring block and ( 3) The order of the lower left neighboring blocks derives motion information from neighboring sub-blocks.

As in the example of FIG. 19 , as adjacent sub-blocks adjacent to the current sub-block, (1) upper adjacent block, (2) left adjacent block, (3) lower adjacent block, (4) right adjacent block The motion information of the current sub-block within the current block is derived from the sequence of block, (5) upper left neighbor block, (6) lower left neighbor block, (7) lower right neighbor block, and (8) upper right neighbor block. Alternatively, the motion information may be derived in a different order than that shown in FIG. 19 .

On the other hand, motion information for co-located sub-blocks within a co-located picture may be subsequently derived after motion information for neighboring sub-blocks that are spatially adjacent to the current sub-block is derived. Alternatively, motion information for co-located sub-blocks within a co-located picture may be derived prior to deriving motion information for neighboring sub-blocks that are spatially adjacent to the current sub-block.

In addition, motion information for coded/decoded blocks located at the lower and right boundaries of the reference block within the reference picture may be subsequently derived after motion information for neighboring sub-blocks that are spatially adjacent to the current sub-block is derived. Alternatively, motion information for coded/decoded blocks located at the lower and right boundaries of the reference block within the reference picture may be derived before motion information for neighboring sub-blocks that are spatially adjacent to the current sub-block may be derived.

Only when a predetermined condition is satisfied, motion information of adjacent subblocks adjacent to the current block or motion information of adjacent subblocks adjacent to the current subblock may be derived as motion information for generating the second prediction block.

For example, when at least one of adjacent sub-blocks adjacent to the current block or adjacent sub-blocks within the current block adjacent to the current sub-block exists, the motion information of the existing adjacent sub-blocks may be derived as used for generating the first sub-block. 2. The motion information of the prediction block.

Further optionally, for example, when at least one of the adjacent subblocks adjacent to the current block or the adjacent subblocks within the current block adjacent to the current subblock is predicted in the inter prediction mode, it is predicted in the inter prediction mode. The motion information of the predicted neighboring sub-blocks may be derived as motion information for generating the second prediction block. Meanwhile, when at least one of the adjacent subblocks adjacent to the current block or adjacent subblocks within the current block adjacent to the current subblock is predicted in the intra prediction mode, the adjacent subblocks predicted in the intra prediction mode The motion information of the block may not be derived as motion information for generating the second prediction block, since the neighboring sub-blocks do not have motion information.

In addition, when the inter prediction indicator of at least one of the adjacent subblock adjacent to the current block or the adjacent subblock adjacent to the current subblock within the current block does not indicate L0 prediction, L1 prediction, L2 prediction, L3 prediction , unidirectional prediction, bidirectional prediction, three-way prediction, and four-way prediction, the motion information for generating the second prediction block may not be derived.

In addition, when the inter prediction indicator used to generate the second prediction block is different from the inter prediction indicator used to generate the first prediction block, motion information used to generate the second prediction block may be derived.

In addition, when the motion vector used for generating the second prediction block is different from the motion vector used for generating the first prediction block, motion information required for generating the second prediction block may be derived.

In addition, when the reference picture index used for generating the second prediction block is different from the reference picture index used for generating the first prediction block, motion information required for generating the second prediction block may be derived.

In addition, when at least one of the motion vector and the reference picture index used to generate the second prediction block is different from at least one of the motion vector and the reference picture index used to generate the first prediction block, it may be deduced to generate the second prediction block required sports information.

In addition, in order to reduce computational complexity, in the case where the inter prediction indicator used to generate the first prediction block indicates unidirectional prediction, when the motion vector sum of the L0 prediction direction and the L1 prediction direction used to generate the second prediction block When at least one of the reference picture indices is different from at least one of the motion vector and the reference picture index used to generate the first prediction block, motion information required for generating the second prediction block may be derived.

In addition, in order to reduce computational complexity, based on the inter prediction indicator used to generate the first prediction block, in the case where the inter prediction indicator indicates bidirectional prediction, when the L0 prediction direction and L1 used to generate the second prediction block When the at least one set of the motion vector of the prediction direction and the reference picture index is different from the at least one set of the motion vector and the reference picture index of the L0 prediction direction and the L1 prediction direction used to generate the first prediction block, the generation of the second prediction block may be derived required sports information.

In addition, in order to reduce computational complexity, when at least one piece of motion information used to generate the second prediction block is different from at least one piece of motion information used to generate the first prediction block, motion information required to generate the second prediction block may be derived.

20 is a diagram illustrating determining whether motion information of a specific neighboring subblock can be used for generating a second prediction block by comparing the POC of the reference picture of the current subblock with the POC of the reference picture of the specific neighboring subblock Illustration of an example of motion information.

20 , in order to reduce computational complexity, when the POC of the reference picture of the current subblock is equal to the POC of the reference picture of the adjacent subblock, the motion information of the current subblock may be used to generate the second prediction block of the current subblock.

In addition, in order to reduce the computational complexity, as in the example of FIG. 20 , when the POC of the reference picture used to generate the second prediction block is different from the POC of the reference picture used to generate the first prediction block, it can be deduced to generate the second prediction block. Motion information needed to predict the block.

Specifically, when the POC of the reference picture used to generate the second prediction block is different from the POC of the reference picture used to generate the first prediction block, the POC pair based on the reference picture or the reference picture may be used to generate the first prediction block is scaled to derive the motion vector used to generate the second prediction block.

FIG. 21 is a diagram illustrating an example of using a weighting factor when calculating a weighted sum of the first prediction block and the second prediction block.

When calculating the weighted sum of the first prediction block and the second prediction block, different weighting factors may be applied to the samples in the block which are used according to their position in the block. In addition, a weighted sum of samples co-located in the first prediction block and the second prediction block may be calculated. In this case, when the weighted sum is calculated to produce the final prediction block, at least one of the weighting factor and the offset may be used for the calculation.

Here, the weight factor may be a negative value less than zero or a positive value greater than zero. The offset can be zero, a negative value less than zero, or a positive value greater than zero.

When the weighted sum of the first prediction block and the second prediction block is calculated, the same weighting factor may be applied to all samples in each prediction block.

21 , for example, weighting factors {3/4, 7/8, 15/16 and 31/32} may be applied to respective rows or columns of the first prediction block, and weighting factors {1/4, 1 may be applied /8, 1/16 and 1/32} are applied to each row or column of the second prediction block. In this case, the samples in the same row or the same column may be applied with the same weighting factor.

The value of the weighting factor increases as the distance from the boundary of the current subblock decreases. Additionally, weighting factors can be applied to all samples within a sub-block.

In FIG. 21, (a), (b), (c), and (d) show the motion information of the upper adjacent block, the motion information of the lower adjacent block, the motion information of the left adjacent block, and the right adjacent block by using the motion information of the upper adjacent block, respectively. Motion information of neighboring blocks to generate the second prediction block. Here, the upper second prediction block, the lower second prediction block, the left second prediction block and the right second prediction block may be based on the motion information of the upper adjacent block, the motion information of the lower adjacent block, the left adjacent block, respectively. The second prediction block is generated from the motion information of the right adjacent block and the motion information of the adjacent block to the right.

FIG. 22 is a diagram illustrating an embodiment of applying different weighting factors to samples according to positions in the block when calculating the weighted sum of the first prediction block and the second prediction block. In order to improve coding efficiency, when the weighted sum of the first prediction block and the second prediction block is calculated, the weighting factor may vary according to the position of the sample in the block. That is, the weighted sum may be calculated using different weighting factors according to the positions of the samples that are spatially adjacent to the current sub-block. Additionally, a weighted sum may be calculated for samples co-located in the first prediction block and the second prediction block.

22 , in the first prediction block, weight factors {1/2, 3/4, 7/8, 15/16, 31/32, 63/64, 127/128, 255/256, 511/512 and 1023/ 1024} is applied to each sample, and in the second prediction block, weighting factors {1/2, 1/4, 1/16, 1/32, 1/64, 1/128, 1/256 may be applied according to position , 1/512 and 1/1024} are applied to each sample. Here, the weighting factor used in at least one of the upper second prediction block, the left second prediction block, the lower second prediction block, and the right second prediction block may be larger than that used in the upper left second prediction block, the lower left second prediction block A weighting factor used in at least one of the second prediction block, the lower right second prediction block, and the upper right second prediction block.

In addition, the weighting factor used in at least one of the upper second prediction block, the left second prediction block, the lower second prediction block, and the right second prediction block may be equal to that in the upper left second prediction block, the lower left prediction block A weighting factor used in at least one of the second prediction block, the lower right second prediction block, and the upper right second prediction block.

In addition, the weighting factors of all samples in the second prediction block generated using the motion information of the co-located sub-blocks in the co-located picture may be equal.

In addition, the weighting factor of the samples in the second prediction block generated using the motion information of the co-located sub-blocks in the co-located picture may be equal to the weighting factor of the samples in the first prediction block.

In addition, the weighting factors of all samples in the second prediction block generated using the motion information of the coded/decoded blocks adjacent to the lower and right boundaries of the reference block within the reference picture may be equal.

In addition, the weighting factor of the samples in the second prediction block generated using the motion information of the coded/decoded blocks adjacent to the lower and right boundaries of the reference block within the reference picture may be equal to the samples in the first prediction block Point weighting factor.

In order to reduce computational complexity, the weighting factor may vary according to the size of the motion vectors of neighboring sub-blocks adjacent to the current block or adjacent sub-blocks within the current block and adjacent to the current sub-block.

For example, {1/2, 3/4, 7/8, 15/16} may be used as the current sub-block when the sum of the absolute values of the x-component and the y-component of the motion vector of the adjacent sub-block is equal to or greater than a predetermined value Weight factor for the block. Conversely, when the sum of the absolute values of the x-component and the y-component of the motion vector of the adjacent subblock is smaller than the predetermined value, {7/8, 15/16, 31/32, 63/64} may be used as the current subblock weight factor. In this case, the predetermined value may be zero or a positive integer.

In addition, in order to reduce computational complexity, the weighting factor may be changed according to the magnitude or direction of the motion vector of the current sub-block.

For example, when the absolute value of the x-component of the motion vector of the current subblock is equal to or greater than a predetermined value, {1/2, 3/4, 7/8, 15/16} may be used as the left adjacent subblock and the right Weighting factor for side adjacent subblocks. Conversely, when the absolute value of the x-component of the motion vector of the current subblock is smaller than the predetermined value, {7/8, 15/16, 31/32, 63/64} may be used as the left adjacent subblock and the right Weighting factor for adjacent subblocks. In this case, the predetermined value may be zero or a positive integer.

For example, when the absolute value of the y component of the motion vector of the current subblock is equal to or greater than a predetermined value, {1/2, 3/4, 7/8, 15/16} may be used as the upper adjacent subblock and the lower adjacent subblock Weighting factor for subblocks. Conversely, when the absolute value of the y-component of the motion vector of the current sub-block is smaller than the predetermined value, {7/8, 15/16, 31/32, 63/64} may be used as the upper adjacent sub-block and the lower adjacent sub-block Weight factor for the block. In this case, the predetermined value may be zero or a positive integer.

For example, when the sum of absolute values of the x component and the y component of the motion vector of the current subblock is equal to or greater than a predetermined value, {1/2, 3/4, 7/8, 15/16} may be used as the current subblock Weight factor for the block. Conversely, when the sum of the absolute values of the x component and the y component of the motion vector of the current subblock is less than the predetermined value, {7/8, 15/16, 31/32, 63/64} may be used as the current subblock weight factor. In this case, the predetermined value may be zero or a positive integer.

The weighted sum may not be calculated for all samples within a sub-block, but only for some samples in the K rows/columns adjacent to each block boundary. In this case, K can be zero or a positive integer, such as 1 or 2.

Additionally, when the size of the current block is smaller than NxM, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary. In addition, when the current block is divided into sub-blocks and motion compensation is performed based on the sub-blocks, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary. Here, K can be zero or a positive integer, such as 1 or 2. In addition, N and M may be positive integers. For example, N and M can be 4 or greater and 8 or greater. N and M may or may not be equal.

Optionally, a weighted sum may be calculated for samples in the K rows/columns adjacent to each block boundary according to the type of color components of the current block. In this case, K can be zero or a positive integer, such as 1 or 2. When the current block is a luma component block, a weighted sum may be calculated for samples in two rows/columns adjacent to each block boundary. On the other hand, when the current block is a chroma component block, a weighted sum may be calculated for samples in a row/column adjacent to each block boundary.

In addition, when the current block is to be predicted in merge mode and has at least one of improved temporal motion vector prediction candidates and spatio-temporal motion vector prediction candidates, only K rows/columns adjacent to each block boundary may be used A weighted sum is calculated for the samples in .

Additionally, when the current block is to be predicted in the decoder-side motion vector derivation mode, a weighted sum may be calculated for the samples in the K rows/columns adjacent to each block boundary. Additionally, when the current block is to be predicted in affine motion compensation mode, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary. In these cases, K can be zero or a positive integer, such as 1 or 2.

Meanwhile, in order to reduce computational complexity, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary according to the size of sub-blocks of the current block.

For example, when the sub-blocks of the current block have a size of 4x4, the weighted sum may be calculated for the samples in one, two, three or four rows/columns adjacent to each block boundary. Optionally, when the sub-blocks of the current block have a size of 8×8, one, two, three, four, five, six, seven or eight adjacent to each block boundary may be A weighted sum is calculated for the samples in the row/column. In this case, K can be zero or a positive integer. The maximum value of K may correspond to the number of rows or columns included in the sub-block.

Additionally, to reduce computational complexity, a weighted sum may be computed for samples within a sub-block in one or two rows/columns adjacent to each block boundary.

In addition, in order to reduce computational complexity, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary according to the number of pieces of motion information used to generate the second prediction block. Here, K can be zero or a positive integer.

For example, when the number of pieces of motion information is less than a predetermined value, a weighted sum may be calculated for samples in two rows/columns adjacent to each block boundary.

In addition, when the number of pieces of motion information is equal to or greater than the predetermined value, a weighted sum may be calculated for samples in one row/column adjacent to each block boundary.

Additionally, to reduce computational complexity, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary according to the current block's inter prediction indicator. K can be zero or a positive integer.

For example, when the inter prediction indicator indicates uni-directional prediction, a weighted sum may be calculated for samples in two rows/columns adjacent to each block boundary. Meanwhile, when the inter prediction indicator indicates bidirectional prediction, a weighted sum may be calculated for samples in one row/column adjacent to each block boundary.

In addition, in order to reduce computational complexity, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary according to the POC of the reference picture of the current block. Here, K can be zero or a positive integer.

For example, when the difference between the POC of the current picture and the POC of the reference picture is less than a predetermined value, a weighted sum may be calculated for samples in two rows/columns adjacent to each block boundary. Conversely, when the difference between the POC of the current picture and the POC of the reference picture is equal to or greater than the predetermined value, a weighted sum may be calculated for samples in one row/column adjacent to each block boundary.

In addition, in order to reduce the computational complexity, according to the size of the motion vector of the adjacent sub-block adjacent to the current block or the motion vector of the adjacent sub-block adjacent to the current sub-block within the current block, for each block boundary A weighted sum is calculated for the samples in the neighboring K rows/columns. Here, K can be zero or a positive integer.

For example, when the sum of absolute values of the x and y components of the motion vectors of adjacent subblocks is equal to or greater than a predetermined value, a weighted sum may be calculated for samples in two rows/columns adjacent to each block boundary. Conversely, when the sum of absolute values of the x and y components of the motion vectors of adjacent subblocks is less than the predetermined value, a weighted sum may be calculated for samples in a row/column adjacent to each block boundary. In this case, the predetermined value may be zero or a positive integer.

In addition, in order to reduce computational complexity, a weighted sum may be calculated for samples in K rows/columns adjacent to each block boundary according to the magnitude or direction of the motion vector of the current sub-block. Here, K can be zero or a positive integer.

For example, when the absolute value of the x-component of the motion vector of the current subblock is equal to or greater than a predetermined value, a weighted sum may be calculated for samples in two rows/columns adjacent to each of the left and right boundaries. Conversely, when the absolute value of the x-component of the motion vector of the current subblock is smaller than the predetermined value, a weighted sum may be calculated for samples in a row/column adjacent to each of the left and right boundaries. In this case, the predetermined value may be zero or a positive integer.

For example, when the absolute value of the y component of the motion vector of the current subblock is equal to or greater than a predetermined value, a weighted sum may be calculated for samples in two rows/columns adjacent to each of the upper and lower boundaries. Conversely, when the absolute value of the y component of the motion vector of the current subblock is smaller than the predetermined value, a weighted sum may be calculated for samples in one row/column adjacent to the upper and lower boundaries. In this case, the predetermined value may be zero or a positive integer.

For example, when the sum of absolute values of the x and y components of the motion vector is equal to or greater than a predetermined value, a weighted sum may be calculated for samples in two rows/columns adjacent to each block boundary. Conversely, when the sum of the absolute values of the x-component and the y-component of the motion vector is smaller than the predetermined value, a weighted sum may be calculated for the samples in one row/column adjacent to each block boundary. In this case, the predetermined value may be zero or a positive integer.

FIG. 23 is a diagram illustrating an embodiment in which a weighted sum of a first prediction block and a second prediction block is sequentially and cumulatively calculated in a predetermined order during overlapping block motion compensation. The weighted sums of the first prediction block and the second prediction block may be added in a predetermined order preset in the encoder and the decoder.

23, motion information may be derived from adjacent subblocks in the order of an upper block, a left block, and a right block adjacent to the current subblock; the derived motion information may be used in this order to generate a second prediction block; A weighted sum of the first prediction block and the second prediction block may be calculated. When the weighted sums are calculated in a predetermined order, the weighted sums may be accumulated in the above-mentioned order, and thus the final prediction block of the current block may be derived.

As in the example of FIG. 23 , the weighted sum of the first prediction block and the second prediction block generated using the motion information of the upper block is calculated, so that the first weighted sum result block can be generated. Then, a weighted sum of the first weighted sum result block and the second prediction block generated using the motion information of the left block may be calculated, so that a second weighted sum result block may be generated. Then, a weighted sum of the second weighted sum result block and the second prediction block generated using the motion information of the lower block may be calculated, so that a third weighted sum result block may be generated. Finally, a weighted sum of the third weighted sum result block and the second prediction block generated using the motion information of the right block may be calculated, so that the final prediction block may be generated.

On the other hand, the order of deriving the motion information for generating the second prediction block and the order of calculating the weighted sum of the first prediction block and the second prediction block may be different.

FIG. 24 is a diagram illustrating an embodiment of calculating a weighted sum of a first prediction block and a second prediction block during overlapping block motion compensation. In order to improve coding efficiency, when the weighted sum is calculated, the weighted sum is not calculated cumulatively in sequence, but the first prediction block can be calculated without considering the order in which the second prediction block is generated and the use of the upper block and the left block , a weighted sum of the second prediction block generated by the motion information of at least one of the lower block and the right block.

In this case, weighting factors for the second prediction block generated using motion information of at least one of the upper, left, lower, and right blocks may be equal to each other. Alternatively, the weighting factor for the second prediction block and the weighting factor for the first prediction block may be equal.

Referring to FIG. 24 , a plurality of recording spaces corresponding to the total number of the first prediction block and the second prediction block are prepared, and when the final prediction block is generated, the first prediction block may be calculated while using equal weighting factors for all the second prediction blocks. A weighted sum of the predicted block and each second predicted block.

In addition, even for a second prediction block generated using motion information of a co-located subblock within a co-located picture, a weighted sum of the first prediction block and the second prediction block may be calculated.

When the size of the current block is K samples or less, entropy encoding/entropy decoding may be performed on information determining whether to perform overlapping block motion compensation on the current block. Here, K can be a positive integer, such as 256.

Whether or not to perform overlapping block motion compensation on the current block may not be determined when the size of the current block is larger than K samples or when the current block is to be predicted in a specific inter prediction mode (eg, merge mode or advanced motion vector prediction mode) Entropy encoding/entropy decoding of the information, but overlapping block motion compensation can be substantially performed.

The encoder may perform prediction after subtracting the second prediction block from the original signal of the boundary area of the current block when performing motion prediction. In this case, when the second prediction block is subtracted from the original signal, a weighted sum of the second prediction block and the original signal may be calculated.

Enhanced Multiple Transform (EMT) may not be applied for the current block for which overlapping block motion compensation is not performed, in which Discrete Cosine Transform (DCT) and Discrete Sine Transform (DST) are applied to vertical/ Horizontal transformation. That is, the enhanced multiple transform may be applied only to the current block on which the overlapping block motion compensation is performed.

FIG. 25 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

Referring to FIG. 25, a first prediction block of the current block may be generated using motion information of the current block (step S2510).

Next, motion information that can be used to generate the second prediction block may be determined among motion information of at least one neighboring sub-block of the current sub-block (step S2520).

In this case, motion information that can be used to generate the second prediction block may be determined based on at least one of the magnitude and direction of motion vectors of adjacent sub-blocks.

In the step S2520 of determining motion information that can be used to generate the second prediction block, a picture count (POC) that can be used to generate the second prediction block may be determined based on the picture count (POC) of the reference picture of the adjacent sub-block and the POC of the reference picture of the current block. sports information. Specifically, only when the POC of the reference picture of the neighboring sub-block is equal to the POC of the reference picture of the current block, the motion information of the neighboring sub-block may be determined as motion information that can be used to generate the second prediction block.

The current subblock has a square shape or a non-square shape.

At least one second prediction block may be generated using the determined motion information determined at step S2520 (step S2530).

The at least one second prediction block may be generated using the motion information of at least one neighboring sub-block only when the current block has neither the motion vector derivation mode nor the affine motion compensation mode.

Next, a final prediction block may be generated based on the weighted sum of the first prediction block of the current block and the at least one second prediction block of the current sub-block (step S2540).

When the current sub-block is included in the boundary area of the current block, samples in several rows or columns of the first prediction block adjacent to the boundary and several rows adjacent to the boundary of the second prediction block may be obtained by obtaining or a weighted sum of samples in several columns to produce the final prediction block.

Here, the block size of the first prediction block may be determined based on at least one of a block size of the current subblock, a size and direction of a motion vector of the current subblock, an inter prediction indicator of the current block, and a POC of a reference picture of the current block. Samples in rows or columns adjacent to the boundary and samples in rows or columns adjacent to the boundary of the second prediction block.

In the final prediction block generation step S2540, the weighted sum may be calculated while applying different weighting factors to the samples in the first prediction block and the second prediction block according to at least one of the size and direction of the motion vector of the current subblock .

Each step of the image decoding method of FIG. 25 can be similarly applied to the corresponding step of the image encoding method of the present invention.

A bit stream generated by performing the image encoding method according to the present invention can be recorded in a recording medium.

The above embodiments can be implemented in the same way in encoders and decoders.

The order applied to the above embodiments may differ between the encoder and the decoder, or the order applied to the above embodiments may be the same in the encoder and the decoder.

The above embodiments may be performed for each luminance signal and chrominance signal, or may be performed identically for luminance signals and chrominance signals.

The block shape to which the above embodiments of the present invention are applied may have a square shape or a non-square shape.

The above embodiments of the present invention may be applied according to the size of at least one of a coding block, a prediction block, a transform block, a block, a current block, a coding unit, a prediction unit, a transform unit, a unit, and a current unit. Here, the size may be defined as a minimum size or a maximum size or both, such that the above embodiments are applied, or may be defined as a fixed size to which the above embodiments are applied. In addition, in the above embodiments, the first embodiment may be applied to the first size, and the second embodiment may be applied to the second size. In other words, the above embodiments may be applied in combination according to the size. In addition, the above embodiments can be applied when the size is equal to or larger than the minimum size and equal to or smaller than the maximum size. In other words, when the block size is included in a specific range, the above embodiments can be applied.

For example, when the size of the current block is 8×8 or larger, the above embodiments may be applied. For example, when the size of the current block is 4×4 or larger, the above embodiments may be applied. For example, when the size of the current block is 16×16 or larger, the above embodiments may be applied. For example, when the size of the current block is equal to or larger than 16×16 and equal to or smaller than 64×64, the above embodiments may be applied.

The above embodiments of the present invention may be applied according to time layers. In order to identify that the above embodiments may be applied to temporal layers, respective identifiers may be signaled, and the above embodiments may be applied to specific temporal layers identified by the respective identifiers. Here, the identifier may be defined as the lowest layer or the highest layer or both the lowest layer and the highest layer to which the above embodiments are applicable, or may be defined as indicating a specific layer to which the embodiment is applied. In addition, a fixed time horizon to which an embodiment is applied may be defined.

For example, the above embodiment can be applied when the temporal layer of the current image is the lowest layer. For example, when the temporal layer identifier of the current image is 1, the above embodiment can be applied. For example, the above embodiment can be applied when the temporal layer of the current image is the highest layer.

The stripe types to which the above embodiments of the present invention are applied may be defined, and the above embodiments may be applied according to the corresponding stripe types.

In the above-described embodiments, the method is described based on a flowchart having a series of steps or units, but the present invention is not limited to the order of the steps, but rather, some steps may be performed concurrently with other steps, or may be performed with other steps The steps are performed in different orders. Furthermore, it should be understood by those of ordinary skill in the art that the steps in the flowcharts are not mutually exclusive and that other steps may be added to the flowcharts, or some steps may be extracted from the flowcharts, without affecting the scope of the present invention. delete.

Embodiments include various aspects of examples. All possible combinations for the various aspects may not be described, but those skilled in the art will be able to recognize different combinations. Accordingly, the present invention may include all alternatives, modifications and changes within the scope of the claims.

Embodiments of the present invention may be implemented in the form of program instructions executable by various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc., alone or in combinations of program instructions, data files, data structures, and the like. The program instructions recorded in the computer-readable recording medium may be specially designed and constructed for the present invention or known to those of ordinary skill in the field of computer software technology. Examples of computer-readable recording media include: magnetic recording media (such as hard disks, floppy disks, and magnetic tapes); optical data storage media (such as CD-ROM or DVD-ROM); magneto-optical media (such as floppy disks); A hardware device (such as read only memory (ROM), random access memory (RAM), flash memory, etc.) for storing and implementing program instructions. Examples of program instructions include not only machine language code formed by a compiler, but also high-level language code that can be implemented by a computer using an interpreter. A hardware device may be configured to be operated by one or more software modules to perform processing in accordance with the present invention, and vice versa.

Although the present invention has been described in terms of specific terms, such as detailed elements, and limited embodiments and drawings, they are provided only to assist in a more general understanding of the present invention, and the present invention is not limited to the above-described embodiments. Those skilled in the art to which this invention pertains will appreciate that various modifications and changes can be made from the above description.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and the full scope of the appended claims and their equivalents are intended to fall within the scope and spirit of the present invention.

Industrial Availability

The present invention can be applied to an apparatus for encoding/decoding an image.

Claims (19)

1. A method for decoding an image, the method comprising: generating a first prediction block of the current block using the motion information of the current block; determining motion information that can be used to generate the second prediction block among motion information of at least one neighboring sub-block of the current sub-block; generating at least one second prediction block of the current subblock using the determined motion information; and A final prediction block is generated based on a weighted sum of the first prediction block of the current block and the at least one second prediction block of the current sub-block. 2. The method of claim 1, wherein the step of determining motion information that can be used to generate the second prediction block comprises: The motion information that can be used to generate the second prediction block is determined based on at least one of magnitude and direction of motion vectors of neighboring subblocks of the current subblock. 3. The method of claim 1, wherein the step of determining motion information that can be used to generate the second prediction block comprises: The motion information that can be used to generate the second prediction block is determined based on the picture count POC of the reference picture of the neighboring sub-block and the POC of the reference picture of the current block. 4. The method of claim 3, wherein, in the step of determining motion information that can be used to generate the second prediction block, only if the POC of the reference picture of the adjacent sub-block is equal to the POC of the reference picture of the current block , the motion information of the adjacent sub-block is determined as the motion information that can be used to generate the second prediction block. 5. The method of claim 1, wherein the current sub-block has at least one of a square shape and a rectangular shape. 6. The method of claim 1, wherein the step of generating at least one second prediction block comprises: The at least one second prediction block is generated using motion information of at least one neighboring sub-block of the current sub-block only when the current block has neither the motion vector derivation mode nor the affine motion compensation mode. 7. The method of claim 1, wherein the step of generating a final prediction block comprises: When the current sub-block is included in the boundary area of the current block, by obtaining each sample in a part row or part column of the first prediction block adjacent to the boundary and a part adjacent to the boundary of the second prediction block A weighted sum of each sample in a row or partial column produces the final prediction block. 8. The method of claim 7, wherein samples in the partial row or the partial column of the first prediction block adjacent to the boundary and the part of the second prediction block adjacent to the boundary The samples in the row or the partial column are based on at least one of the block size of the current subblock, the size and direction of the motion vector of the current subblock, the inter prediction indicator of the current block, and the POC of the reference picture of the current block It is determined. 9. The method of claim 1, wherein the step of generating a final prediction block comprises: The weighted sum of the first prediction block and the second prediction block is obtained by applying different weighting factors to the samples in the first prediction block and the second prediction block according to at least one of the size and the direction of the motion vector of the current subblock. 10. A method for encoding an image, the method comprising: generating a first prediction block of the current block using the motion information of the current block; determining motion information that can be used to generate the second prediction block among motion information of at least one neighboring sub-block of the current sub-block; generating at least one second prediction block of the current subblock using the determined motion information; A final prediction block is generated based on a weighted sum of the first prediction block of the current block and the at least one second prediction block of the current sub-block. 11. The method of claim 10, wherein the step of determining motion information that can be used to generate the second prediction block comprises: The motion information that can be used to generate the second prediction block is determined based on at least one of a magnitude and a direction of motion vectors of the neighboring sub-blocks. 12. The method of claim 10, wherein the step of determining motion information that can be used to generate the second prediction block comprises: The motion information that can be used to generate the second prediction block is determined based on the POC of the reference picture of the neighboring sub-block and the POC of the reference picture of the current block. 13. The method of claim 12, wherein the step of determining motion information that can be used to generate the second prediction block comprises: Only when the POC of the reference picture of the neighboring sub-block is equal to the POC of the reference picture of the current block, the motion information of the neighboring sub-block is determined as the motion information that can be used to generate the second prediction block. 14. The method of claim 10, wherein the current sub-block has at least one of a square shape and a rectangular shape. 15. The method of claim 10, wherein the step of generating at least one second prediction block comprises: The at least one second prediction block is generated using the motion information of the at least one neighboring sub-block only when the current block has neither the motion vector derivation mode nor the affine motion compensation mode. 16. The method of claim 10, wherein the step of generating a final prediction block comprises: When the current sub-block is included in the boundary area of the current block, based on the samples in the partial row or column of the first prediction block adjacent to the boundary and the partial row or part of the second prediction block adjacent to the boundary A weighted sum of the samples in the column to produce the final prediction block. 17. The method of claim 16, wherein the samples in the partial row or the partial column of the first prediction block adjacent to the boundary and the part of the second prediction block adjacent to the boundary The samples in the row or the partial column are based on at least one of the block size of the current subblock, the size and direction of the motion vector of the current subblock, the inter prediction indicator of the current block, and the POC of the reference picture of the current block It is determined. 18. The method of claim 10, wherein the step of generating a final prediction block comprises: The weighted sum is obtained by applying different weight values to the samples in the first prediction block and the second prediction block according to at least one of the magnitude and direction of the motion vector of the current subblock. 19. A recording medium storing a bitstream generated by an image encoding method, the image encoding method comprising: generating a first prediction block of the current block using the motion information of the current block; determining motion information that can be used to generate the second prediction block among motion information of at least one neighboring sub-block of the current sub-block; generating at least one second prediction block of the current subblock using the determined motion information; A final prediction block is generated based on a weighted sum of the first prediction block of the current block and the at least one second prediction block of the current sub-block.