KR20240005637A - Method and apparatus for encoding/decoding image and recording medium for storing bitstream - Google Patents

Abstract

The present invention relates to video encoding and decoding methods. An image decoding method for this includes generating a first prediction block of the current block using motion information of the current block, and generating at least one prediction block of the current sub-block using motion information of at least one neighboring sub-block of the current sub-block. Generating a second prediction block of a block and generating a final prediction block based on a weighted sum of a first prediction block of the current block and a second prediction block of the at least one current sub-block. there is.

Description

Video encoding/decoding method, device, and recording medium storing bitstream {METHOD AND APPARATUS FOR ENCODING/DECODING IMAGE AND RECORDING MEDIUM FOR STORING BITSTREAM}

The present invention relates to a video encoding/decoding method, device, and recording medium storing bitstreams. Specifically, the present invention relates to a method and device for video encoding/decoding using overlapped block motion compensation.

Recently, demand for high-resolution, high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images is increasing in various application fields. As video data becomes higher resolution and higher quality, the amount of data increases relative to existing video data. Therefore, when video data is transmitted using media such as existing wired or wireless broadband lines or stored using existing storage media, transmission costs and Storage costs increase. In order to solve these problems that arise as image data becomes higher resolution and higher quality, highly efficient image encoding/decoding technology for images with higher resolution and quality is required.

Inter-screen prediction technology that predicts pixel values included in the current picture from pictures before or after the current picture using video compression technology, intra-screen prediction technology that predicts pixel values included in the current picture using pixel information in the current picture, A variety of technologies exist, such as transformation and quantization technology to compress the energy of the residual signal, and entropy coding technology that assigns short codes to values with a high frequency of occurrence and long codes to values with a low frequency of occurrence, and these image compression technologies can be used to Video data can be effectively compressed and transmitted or stored.

Conventional video encoding/decoding methods and devices have limitations in improving encoding efficiency because they only use limited motion information of neighboring blocks when compensating for motion of overlapping blocks.

The present invention can provide a method and device for performing overlapped block motion compensation by increasing the number of motion information of neighboring blocks to improve video encoding/decoding efficiency.

According to the present invention, an image decoding method includes generating a first prediction block of the current block using motion information of the current block; Generating a second prediction block of at least one current sub-block using motion information of at least one neighboring sub-block of the current sub-block, and generating a first prediction block of the current block and the at least one current sub-block It may include generating a final prediction block based on the weighted sum of the second prediction blocks.

In the video decoding method, the neighboring sub-block may include a neighboring sub-block of a sub-block of a corresponding location block temporally corresponding to the current block.

In the image decoding method, the step of generating the second prediction block includes, when the current sub-block is not included in the left border area and the top border area of the current block, at least one of the sub-blocks of the corresponding location block. At least one second prediction block can be generated using motion information of neighboring sub-blocks.

In the video decoding method, the step of generating the second prediction block includes, when the current sub-block is not included in the left border area and the top border area of the current block, a merge list and a motion vector list of the current block. A second prediction block can be generated using motion information included in at least one of the following.

In the image decoding method, the step of generating the second prediction block may be performed on at least one neighboring sub-block only when the current sub-block is included in at least one of a left border area and an upper border area of the current block. At least one second prediction block can be generated using motion information.

In the image decoding method, the step of generating the second prediction block includes, when the current sub-block is included in the left boundary area of the current block, a left neighboring sub-block, an upper-left neighboring sub-block, and At least one second prediction block is generated using motion information of at least one of the lower left neighboring sub-blocks, and when the current sub-block is included in the upper border area of the current block, the upper neighboring sub-block of the current sub-block At least one second prediction block can be generated using motion information of at least one of the block, the upper-left neighboring sub-block, and the lower-right neighboring sub-block.

In the image decoding method, the step of generating the second prediction block includes, when the current sub-block is not included in the left border area and the top border area of the current block, the upper neighboring sub-block of the current sub-block, At least one second motion information is generated using the motion information of at least one of the left peripheral sub-block, the lower peripheral sub-block, the right peripheral sub-block, the upper-left peripheral sub-block, the lower-left peripheral sub-block, the lower-right peripheral sub-block, and the upper-right peripheral sub-block. A prediction block can be created.

In the image decoding method, the step of generating the second prediction block includes deriving motion information of at least one neighboring sub-block of the current sub-block based on a predetermined order, and deriving motion information of at least one neighboring sub-block of the current sub-block. At least one second prediction block can be generated using .

In the image decoding method, the step of generating the final prediction block includes calculating weights for each sample of the first prediction block and the second prediction block according to the positions of neighboring sub-blocks used when generating the second prediction block. Weighted sum can be performed by applying it differently.

In the image decoding method, the step of generating the final prediction block includes, when there are a plurality of second prediction blocks of the current sub-block, the difference between the first prediction block of the current block and the second prediction block of the current sub-block. The final prediction block can be generated by simultaneously summing the weighted sums.

According to the present invention, an image encoding method includes generating a first prediction block of the current block using motion information of the current block; Generating a second prediction block of at least one current sub-block using motion information of at least one neighboring sub-block of the current sub-block, and generating a first prediction block of the current block and the at least one current sub-block It may include generating a final prediction block based on the weighted sum of the second prediction blocks.

In the video encoding method, the neighboring sub-block may include a neighboring sub-block of a sub-block of a corresponding location block temporally corresponding to the current block.

In the image encoding method, the step of generating the second prediction block includes, when the current sub-block is not included in the left border area and the top border area of the current block, at least one of the sub-blocks of the corresponding location block. At least one second prediction block can be generated using motion information of neighboring sub-blocks.

In the video encoding method, the step of generating the second prediction block includes, when the current sub-block is not included in the left border area and the top border area of the current block, a merge list and a motion vector list of the current block. A second prediction block can be generated using motion information included in at least one of the following.

In the image encoding method, the step of generating the second prediction block may include generating the second prediction block of at least one neighboring sub-block only when the current sub-block is included in at least one of a left border area and an upper border area of the current block. At least one second prediction block can be generated using motion information.

In the image encoding method, the step of generating the second prediction block includes, when the current sub-block is included in the left border area of the current sub-block, a left neighboring sub-block, an upper-left neighboring sub-block, and At least one second prediction block is generated using motion information of at least one of the lower left neighboring sub-blocks, and when the current sub-block is included in the upper border area of the current block, the upper neighboring sub-block of the current sub-block At least one second prediction block can be generated using motion information of at least one of the block, the upper-left neighboring sub-block, and the lower-right neighboring sub-block.

In the image encoding method, the step of generating the second prediction block includes, when the current sub-block is not included in the left border area and the top border area of the current block, the upper neighboring sub-block of the current sub-block, At least one second motion information is generated using the motion information of at least one of the left peripheral sub-block, the lower peripheral sub-block, the right peripheral sub-block, the upper-left peripheral sub-block, the lower-left peripheral sub-block, the lower-right peripheral sub-block, and the upper-right peripheral sub-block. A prediction block can be created.

In the image encoding method, the step of generating the second prediction block includes deriving motion information of at least one neighboring sub-block of the current sub-block based on a predetermined order, and generating the derived motion information of at least one neighboring sub-block. At least one second prediction block can be generated using .

In the image encoding method, the step of generating the final prediction block includes calculating weights for each sample of the first prediction block and the second prediction block according to the positions of neighboring sub-blocks used when generating the second prediction block. Weighted sum can be performed by applying it differently.

In the image encoding method, the step of generating the final prediction block includes, when the second prediction block of the current sub-block is plural, the first prediction block of the current block and the second prediction block of the current sub-block. The final prediction block can be generated by simultaneously summing the weighted sums.

The recording medium of the present invention includes the steps of generating a first prediction block of the current block using motion information of the current block; Generating a second prediction block of at least one current sub-block using motion information of at least one neighboring sub-block of the current sub-block, and generating a first prediction block of the current block and the at least one current sub-block A bitstream generated by an image encoding method including generating a final prediction block based on a weighted sum of the second prediction blocks can be stored.

According to the present invention, a video encoding/decoding method and device with improved compression efficiency can be provided.

According to the present invention, video encoding and decoding efficiency can be improved.

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

1 is a block diagram showing the configuration of an encoding device to which the present invention is applied according to an embodiment.
Figure 2 is a block diagram showing the configuration of a decoding device according to an embodiment to which the present invention is applied.
Figure 3 is a diagram schematically showing the division structure of an image when encoding and decoding an image.
Figure 4 is a diagram for explaining an embodiment of the inter-screen prediction process.
Figure 5 is a flowchart showing an image encoding method according to an embodiment of the present invention.
Figure 6 is a flowchart showing an image decoding method according to an embodiment of the present invention.
Figure 7 is a flowchart showing an image encoding method according to another embodiment of the present invention.
Figure 8 is a flowchart showing an image decoding method according to another embodiment of the present invention.
Figure 9 is a diagram for explaining an example of deriving a spatial motion vector candidate for the current block.
Figure 10 is a diagram for explaining an example of deriving a temporal motion vector candidate for the current block.
Figure 11 is a diagram to explain an example in which a spatial merge candidate is added to the merge candidate list.
Figure 12 is a diagram for explaining an example in which a temporal merge candidate is added to the merge candidate list.
FIG. 13 is a diagram illustrating an example in which overlapped block motion compensation is performed on a sub-block basis.
FIG. 14 is a diagram illustrating an example in which overlapped block motion compensation is performed using motion information of a sub-block of a corresponding location block.
FIG. 15 is a diagram illustrating an example in which overlapped block motion compensation is performed using motion information of blocks adjacent to the boundary area of a reference block.
FIG. 16 is a diagram illustrating an example in which overlapped block motion compensation is performed on a sub-block group basis.
FIG. 17 is a diagram illustrating an example of the number of motion information used for overlapping block motion compensation.
Figures 18 and 19 are diagrams to explain the derivation order of motion information used to generate the second prediction block.
FIG. 20 is a diagram illustrating an example of determining whether motion information is usable for generating a second prediction block by comparing the POC of the reference image of the current sub-block and the POC of the reference image of the surrounding sub-block.
FIG. 21 is a diagram illustrating an example of weight application when calculating the weighted sum of a first prediction block and a second prediction block.
FIG. 22 is a diagram illustrating an embodiment in which different weights are applied depending on sample positions within the block when calculating the weighted sum of the first prediction block and the second prediction block.
FIG. 23 is a diagram illustrating an embodiment in which the weighted sum of a first prediction block and a second prediction block is cumulatively calculated in a predetermined order when compensating for overlapped block motion.
FIG. 24 is a diagram illustrating an embodiment in which a weighted sum of a first prediction block and a second prediction block is calculated when compensating for overlapped block motion.
Figure 25 is a flowchart explaining an image decoding method according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. Similar reference numbers in the drawings refer to identical or similar functions across various aspects. The shapes and sizes of elements in the drawings may be exaggerated for clearer explanation. For a detailed description of the exemplary embodiments described below, refer to the accompanying drawings, which illustrate specific embodiments by way of example. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that the various embodiments are different from one another but are not necessarily mutually exclusive. For example, specific shapes, structures and characteristics described herein with respect to one embodiment may be implemented in other embodiments without departing from the spirit and scope of the invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiment. Accordingly, the detailed description that follows is not to be taken in a limiting sense, and the scope of the exemplary embodiments is limited only by the appended claims, together with all equivalents to what those claims assert if properly described.

In the present invention, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, the second component may also be named a first component without departing from the scope of the present invention. The term and/or includes any of a plurality of related stated items or a combination of a plurality of related stated items.

When a component of the present invention is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but other components may exist in between. It must be understood that it may be possible. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

The components appearing in the embodiments of the present invention are shown independently to represent different characteristic functions, and do not mean that each component is comprised of separate hardware or a single software component. That is, each component is listed and included as a separate component for convenience of explanation, and at least two of each component can be combined to form one component, or one component can be divided into a plurality of components to perform a function, and each of these components can perform a function. Integrated embodiments and separate embodiments of the constituent parts are also included in the scope of the present invention as long as they do not deviate from the essence of the present invention.

The terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof. In other words, the description of “including” a specific configuration in the present invention does not exclude configurations other than the configuration, and means that additional configurations may be included in the practice of the present invention or the scope of the technical idea of the present invention.

Some of the components of the present invention may not be essential components that perform essential functions in the present invention, but may simply be optional components to improve performance. The present invention can be implemented by including only essential components for implementing the essence of the present invention excluding components used only to improve performance, and a structure including only essential components excluding optional components used only to improve performance. is also included in the scope of rights of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description will be omitted, and the same reference numerals will be used for the same components in the drawings. Redundant descriptions of the same components are omitted.

Additionally, hereinafter, a video may refer to a single picture constituting a video, and may also represent the video itself. For example, “encoding and/or decoding of an image” may mean “encoding and/or decoding of a video,” and may mean “encoding and/or decoding of one of the images that constitute a video.” It may be possible. Here, a picture may have the same meaning as an image.

Glossary of Terms

Encoder: Refers to a device that performs encoding.

Decoder: Refers to a device that performs decoding.

Block: An MxN array of samples. Here, M and N mean positive integer values, and a block can often mean a two-dimensional sample array. A block may mean a unit. The current block may mean an encoding target block that is the target of encoding during encoding, or a decoding target block that is the target of decoding during decoding. Additionally, the current block may be at least one of a coding block, a prediction block, a residual block, and a transform block.

Sample: It is the basic unit that makes up a block. Depending on the bit depth (B _d ), it can be expressed as a value from 0 to 2 ^Bd - 1. In the present invention, sample may be used in the same sense as pixel or pixel.

Unit: Refers to the unit of video encoding and decoding. In video encoding and decoding, a unit may be an area divided from one video. Additionally, a unit may refer to a divided unit when an image is divided into segmented units and encoded or decoded. In encoding and decoding images, predefined processing may be performed for each unit. One unit may be further divided into subunits having a smaller size compared to the unit. Depending on the function, the units are Block, Macroblock, Coding Tree Unit, Coding Tree Block, Coding Unit, Coding Block, and Prediction. It may mean a Prediction Unit, Prediction Block, Residual Unit, Residual Block, Transform Unit, Transform Block, etc. Additionally, in order to refer to a unit separately from a block, a unit may mean that it includes a luminance (Luma) component block, a corresponding chroma component block, and syntax elements for each block. Units may have various sizes and shapes, and in particular, the shape of the unit may include geometric shapes that can be expressed in two dimensions, such as squares, trapezoids, triangles, and pentagons, as well as rectangles. Additionally, the unit information may include at least one of the unit type, unit size, unit depth, unit encoding and decoding order indicating a coding unit, prediction unit, residual unit, transformation unit, etc.

Coding Tree Unit: Consists of one luminance component (Y) coding tree block and two chrominance component (Cb, Cr) coding tree blocks. Additionally, it may mean including the blocks and syntax elements for each block. Each coding tree unit may be divided using one or more partitioning methods, such as a quad tree or binary tree, to form subunits such as a coding unit, prediction unit, or transformation unit. It can be used as a term to refer to a pixel block that becomes a processing unit in the image decoding/coding process, such as segmentation of an input image.

Coding Tree Block: Can be used as a term to refer to any one of Y coding tree block, Cb coding tree block, and Cr coding tree block.

Neighbor block: refers to a block adjacent to the current block. A block adjacent to the current block may mean a block bordering the current block or a block located within a predetermined distance from the current block. A neighboring block may refer to a block adjacent to the vertex of the current block. Here, the block adjacent to the vertex of the current block may be a block vertically adjacent to a neighboring block horizontally adjacent to the current block, or a block horizontally adjacent to a neighboring block vertically adjacent to the current block. The surrounding block may also mean a restored surrounding block.

Reconstructed Neighbor Block: Refers to a neighboring block that has already been spatially/temporally encoded or decoded around the current block. At this time, the restored peripheral block may mean a restored peripheral unit. The reconstructed spatial neighboring block may be a block in the current picture and may be a block that has already been restored through encoding and/or decoding. The reconstructed temporal neighboring block may be a reconstructed block at the same location as the current block of the current picture within the reference picture or a neighboring block thereof.

Unit Depth: Refers to the degree to which the unit is divided. In a tree structure, the root node has the shallowest depth, and the leaf node has the deepest depth. Additionally, when a unit is expressed in a tree structure, the level at which the unit exists may mean the unit depth.

Bitstream: refers to a string of bits containing encoded video information.

Parameter Set: Corresponds to header information among the structures in 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 tile header information.

Parsing: This may mean entropy decoding a bitstream to determine the value of a syntax element, or it may mean entropy decoding itself.

Symbol: May mean at least one of a syntax element of a unit to be encoded/decoded, a coding parameter, or a transform coefficient value. Additionally, the symbol may mean the target of entropy encoding or the result of entropy decoding.

Prediction Unit: Refers to the basic unit when performing predictions such as inter-screen prediction, intra-screen prediction, inter-screen compensation, intra-screen compensation, and motion compensation. One prediction unit may be divided into multiple small partitions or sub-prediction units.

Prediction Unit Partition: This refers to the form in which the prediction unit is divided.

Reference Picture List: Refers to a list containing one or more reference pictures used for inter-screen prediction or motion compensation. The types of reference image lists may include LC (List Combined), L0 (List 0), L1 (List 1), L2 (List 2), and L3 (List 3), and inter-screen prediction requires one or more reference images. Lists can be used.

Inter Prediction Indicator: May refer to the inter-screen prediction direction (unidirectional prediction, bidirectional prediction, etc.) of the current block. Alternatively, it may mean the number of reference images used when generating a prediction block of the current block. Alternatively, it may refer to the number of prediction blocks used when performing inter-screen prediction or motion compensation for the current block.

Reference Picture Index: Refers to an index that indicates a specific reference picture in the reference picture list.

Reference Picture: This may refer to an image referenced by a specific block for inter-screen prediction or motion compensation.

Motion Vector: A two-dimensional vector used for inter-screen prediction or motion compensation, and may refer to the offset between the image to be encoded/decoded and the reference image. For example, (mvX, mvY) may represent a motion vector, mvX may represent a horizontal component, and mvY may represent a vertical component.

Motion Vector Candidate: Refers to a block that is a prediction candidate when predicting a motion vector or the motion vector of that block. Additionally, the motion vector candidate may be included in the motion vector candidate list.

Motion Vector Candidate List: This may refer to a list constructed using motion vector candidates.

Motion Vector Candidate Index: Refers to an indicator pointing to a motion vector candidate in the motion vector candidate list. It can also be called the index of the motion vector predictor.

Motion Information: At least one of reference image list information, reference image, motion vector candidate, motion vector candidate index, merge candidate, merge index, etc., as well as motion vector, reference image index, and inter-prediction indicator. It can mean information containing one thing.

Merge Candidate List: This refers to a list constructed using merge candidates.

Merge Candidate: refers to a spatial merge candidate, a temporal merge candidate, a combined merge candidate, a combined positive prediction merge candidate, a zero merge candidate, etc. Merge candidates may include motion information such as inter-screen prediction indicators, reference image indexes for each list, and motion vectors.

Merge Index: Refers to information indicating a merge candidate in the merge candidate list. Additionally, the merge index may indicate a block from which a merge candidate is derived among blocks restored spatially/temporally adjacent to the current block. Additionally, the merge index may indicate at least one piece of motion information possessed by the merge candidate.

Transform Unit: Refers to a basic unit when performing residual signal encoding/decoding, such as transformation, inverse transformation, quantization, inverse quantization, and transformation coefficient encoding/decoding. One conversion unit may be divided into a plurality of smaller conversion units.

Scaling: refers to the process of multiplying the conversion coefficient level by a factor. A transformation coefficient can be generated as a result of scaling the transformation coefficient level. Scaling can also be called dequantization.

Quantization Parameter: May refer to a value used when generating a transform coefficient level for a transform coefficient in quantization. Alternatively, it may refer to a value used when generating a transform coefficient by scaling the transform coefficient level in dequantization. The quantization parameter may be a value mapped to the quantization step size.

Residual quantization parameter (Delta Quantization Parameter): refers to the difference between the predicted quantization parameter and the quantization parameter of the encoding/decoding target unit.

Scan: This refers to a method of sorting the order of coefficients in a block or matrix. For example, sorting a two-dimensional array into a one-dimensional array is called scanning. Alternatively, sorting a one-dimensional array into a two-dimensional array can also be called a scan or inverse scan.

Transform Coefficient: Refers to the coefficient value generated after performing transformation in the encoder. Alternatively, it may mean a coefficient value generated after performing at least one of entropy decoding and dequantization in the decoder. The quantized level or quantized transform coefficient level obtained by applying quantization to the transform coefficient or residual signal also means the transform coefficient. may be included in

Quantized Level: This refers to a value generated by quantizing the transform coefficient or residual signal in the encoder. Alternatively, it may mean a value that is the target of inverse quantization before performing inverse quantization in the decoder. Similarly, quantized transform coefficient levels that are the result of transform and quantization may also be included in the meaning of quantized level.

Non-zero Transform Coefficient: Refers to a transform coefficient whose value size is not 0 or a transform coefficient level whose value size is not 0.

Quantization Matrix: Refers to a matrix used in the quantization or dequantization process to improve the subjective or objective image quality of an image. The quantization matrix can also be called a scaling list.

Quantization Matrix Coefficient: Refers to each element in the quantization matrix. Quantization matrix coefficients may also be referred to as matrix coefficients.

Default Matrix: Refers to a predetermined quantization matrix predefined in the encoder and decoder.

Non-default Matrix: refers to a quantization matrix that is not predefined in the encoder and decoder and is signaled by the user.

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

The encoding device 100 may be an encoder, a video encoding device, or an image encoding device. A video may contain one or more images. The encoding device 100 can sequentially encode one or more images.

Referring to FIG. 1, the encoding device 100 includes 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, and a quantization unit. It may include a unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transform unit 170, an adder 175, a filter unit 180, and a reference picture buffer 190.

The encoding device 100 may perform encoding on an input image in intra mode and/or inter mode. Additionally, the encoding device 100 can generate a bitstream by encoding an input image and output the generated bitstream. The generated bitstream can be stored in a computer-readable recording medium or streamed through wired/wireless transmission media. When the intra mode is used as the prediction mode, the switch 115 may be switched to the intra mode, and when the inter mode is used as the prediction mode, the switch 115 may be switched to the inter mode. Here, intra mode may mean intra-screen prediction mode, and inter mode may mean inter-screen prediction mode. The encoding device 100 may generate a prediction block for an input block of an input image. Additionally, the encoding device 100 may encode the residual of the input block and the prediction block after the prediction block is generated. The input image may be referred to as the current image that is currently the target of encoding. The input block may be referred to as the current block that is currently the target of encoding or the encoding target block.

When the prediction mode is intra mode, the intra prediction unit 120 may use the pixel value of a block that has already been encoded/decoded around the current block as a reference pixel. The intra prediction unit 120 can perform spatial prediction using reference pixels and generate prediction samples for the input block through spatial prediction. Here, intra prediction may mean prediction within the screen.

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

The motion compensation unit 112 may generate a prediction block by performing motion compensation using a motion vector. Here, inter prediction may mean inter-screen prediction or motion compensation.

When the motion vector value does not have an integer value, the motion prediction unit 111 and the motion compensation unit 112 can generate a prediction block by applying an interpolation filter to some areas in the reference image. . To perform inter-screen prediction or motion compensation, the motion prediction and motion compensation methods of the prediction unit included in the coding unit based on the coding unit include skip mode, merge mode, and improved motion vector prediction ( It is possible to determine whether it is in Advanced Motion Vector Prediction (AMVP) mode or the current picture reference mode, and inter-screen prediction or motion compensation can be performed depending on each mode.

The subtractor 125 may generate a residual block using the difference between the input block and the prediction block. The residual block may also be referred to as a residual signal. The residual signal may refer to the difference between the original signal and the predicted signal. Alternatively, 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 remaining block may be a residual signal in block units.

The transform unit 130 may generate a transform coefficient by performing transformation on the remaining block and output the transform coefficient. Here, the transformation coefficient may be a coefficient value generated by performing transformation on the remaining block. When the transform skip mode is applied, the transform unit 130 may skip transforming the remaining blocks.

Quantized levels can be generated by applying quantization to the transform coefficients or residual signals. Hereinafter, in embodiments, the quantized level 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 quantization parameter, and output the quantized level. At this time, the quantization unit 140 may quantize the transform coefficient using a quantization matrix.

The entropy encoding unit 150 can generate a bitstream by performing entropy encoding according to a probability distribution on the values calculated by the quantization unit 140 or the coding parameter values calculated during the encoding process. and bitstream can be output. The entropy encoding unit 150 may perform entropy encoding on information about pixels of an image and information for decoding the image. For example, information for decoding an image may include syntax elements, etc.

When entropy coding is applied, a small number of bits are allocated to symbols with a high probability of occurrence and a large number of bits are allocated to symbols with a low probability of occurrence to represent symbols, so that the bits for the symbols to be encoded are expressed. The size of the column may be reduced. The entropy encoding unit 150 may use encoding methods such as exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) for entropy encoding. For example, the entropy encoding unit 150 may perform entropy encoding using a Variable Length Coding/Code (VLC) table. In addition, the entropy encoding unit 150 derives a binarization method of the target symbol and a probability model of the target symbol/bin, and then uses the derived binarization method, probability model, and context model. Arithmetic coding can also be performed using .

The entropy encoder 150 can change a two-dimensional block-type coefficient into a one-dimensional vector form through a transform coefficient scanning method to encode the transform coefficient level.

Coding parameters may include information derived from the encoding or decoding process as well as information (flags, indexes, etc.) encoded by the encoder and signaled to the decoder, such as syntax elements, when encoding or decoding an image. It may mean necessary information. For example, unit/block size, unit/block depth, unit/block division information, unit/block division structure, quad tree type division, binary tree type division, binary tree type division direction (horizontal or vertical direction), binary tree-type division type (symmetric division or asymmetric division), intra-screen prediction mode/direction, reference sample filtering method, prediction block filtering method, prediction block filter tab, prediction block filter coefficient, inter-screen prediction mode, Motion information, motion vector, reference image index, inter-screen prediction direction, inter-screen prediction indicator, reference image list, reference image, motion vector prediction candidate, motion vector candidate list, whether to use merge mode, merge candidate, merge candidate list, skip (skip) mode usage, interpolation filter type, interpolation filter tab, interpolation filter coefficient, motion vector size, motion vector expression accuracy, transformation type, transformation size, information on whether to use primary transformation, information on whether to use secondary transformation, primary Transformation index, secondary transformation index, residual signal presence information, Coded Block Pattern, Coded Block Flag, quantization parameters, quantization matrix, application of intra-screen loop filter, intra-screen loop filter coefficient , In-screen loop filter tab, In-screen loop filter shape/shape, Whether to apply deblocking filter, Deblocking filter coefficient, Deblocking filter tab, Deblocking filter strength, Deblocking filter shape/shape, 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 coefficient, adaptive in-loop filter tab, adaptive in-loop filter shape/form, binarization /Inverse binarization method, context model determination method, context model update method, whether to perform regular mode, whether to perform bypass mode, context bin, bypass bin, transformation coefficient, transformation coefficient level, transformation coefficient level scanning method, image display/output At least one value or a combination of information on order, slice identification information, slice type, slice division information, tile identification information, tile type, tile division information, picture type, bit depth, luminance signal, or chrominance signal is an encoding parameter. may be included in

Here, signaling a flag or index may mean that the encoder entropy encodes the flag or index and includes it in the bitstream, and the decoder may include the flag or index from the bitstream. This may mean entropy decoding.

When the encoding device 100 performs encoding through inter prediction, the encoded current image can be used as a reference image for another image to be processed later. Accordingly, the encoding device 100 can restore or decode the current encoded image and store the restored or decoded image as a reference image.

The quantized level may be dequantized in the dequantization unit 160. It may be inverse transformed in the inverse transform unit 170. The inverse quantized and/or inverse transformed coefficients may be combined with the prediction block through the adder 175. A reconstructed block may be generated by combining the inverse quantized and/or inverse transformed coefficients and the prediction block. Here, the inverse-quantized and/or inverse-transformed coefficient refers to a coefficient on which at least one of inverse-quantization and inverse-transformation has been performed, and may refer to a restored residual block.

The restored block may pass through the filter unit 180. The filter unit 180 can apply at least one deblocking filter, sample adaptive offset (SAO), and adaptive loop filter (ALF) to the restored block or restored image. there is. The filter unit 180 may also be referred to as an in-loop filter.

The deblocking filter can remove block distortion occurring at the boundaries between blocks. To determine whether to perform a deblocking filter, it is possible to determine whether to apply a deblocking filter to the current block based on the pixels included in several columns or rows included in the block. When applying a deblocking filter to a block, different filters can be applied depending on the required deblocking filtering strength.

Using sample adaptive offset, an appropriate offset value can be added to the pixel value to compensate for the encoding error. Sample adaptive offset can correct the offset of the deblocked image from the original image on a pixel basis. You can either divide the pixels included in the image into a certain number of areas, determine the area to perform offset, and apply the offset to that area, or apply the offset by considering the edge information of each pixel.

The adaptive loop filter can perform filtering based on a comparison value between the restored image and the original image. After dividing the pixels included in the image into predetermined groups, filtering can be performed differentially for each group by determining the filter to be applied to that group. Information related to whether to apply an adaptive loop filter may be signaled for each coding unit (CU), and the shape and filter coefficients of the adaptive loop filter to be applied may vary for each block.

The reconstructed block or reconstructed image that has passed through the filter unit 180 may be stored in the reference picture buffer 190. Figure 2 is a block diagram showing the configuration of a decoding device according to an embodiment to which the present invention is applied.

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

Referring to FIG. 2, the decoding device 200 includes 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, and an adder 255. , may include a filter unit 260 and a reference picture buffer 270.

The decoding device 200 may receive the bitstream output from the encoding device 100. The decoding device 200 may receive a bitstream stored in a computer-readable recording medium or receive a bitstream streamed through a wired/wireless transmission medium. The decoding device 200 may perform decoding on a bitstream in intra mode or inter mode. Additionally, the decoding device 200 can generate a restored image or a decoded image through decoding, and output the restored image or a decoded image.

If the prediction mode used for decoding is intra mode, the switch may be switched to intra. If the prediction mode used for decoding is inter mode, the switch may be switched to inter.

The decoding device 200 can decode the input bitstream to obtain a reconstructed residual block and generate a prediction block. When the reconstructed residual block and the prediction block are obtained, the decoding device 200 may generate a restored block to be decoded by adding the restored residual block and the prediction block. The block to be decrypted may be referred to as the current block.

The entropy decoding unit 210 may generate symbols by performing entropy decoding according to a probability distribution for the bitstream. The generated symbols may include symbols in the form of quantized levels. Here, the entropy decoding method may be the reverse process of the entropy encoding method described above.

The entropy decoder 210 can change one-dimensional vector form coefficients into two-dimensional block form through a transform coefficient scanning method in order to decode the transform coefficient level.

The quantized level may be inversely quantized in the inverse quantization unit 220 and inversely transformed in the inverse transformation unit 230. The quantized level may be generated as a restored residual block as a result of performing inverse quantization and/or inverse transformation. At this time, the inverse quantization unit 220 may apply the 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 surrounding the decoding target block.

When inter mode is used, the motion compensation unit 250 may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference picture buffer 270. When the motion vector value does not have an integer value, the motion compensator 250 may generate a prediction block by applying an interpolation filter to a partial area in the reference image. To perform motion compensation, based on the coding unit, it can be determined whether the motion compensation method of the prediction unit included in the coding unit is skip mode, merge mode, AMVP mode, or current picture reference mode, and each mode Motion compensation can be performed according to .

The adder 255 may generate a restored block by adding the restored residual block and the prediction block. The 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 the reconstructed image. The filter unit 260 may output a restored image. The reconstructed block or reconstructed image may be stored in the reference picture buffer 270 and used for inter prediction.

Figure 3 is a diagram schematically showing the division structure of an image when encoding and decoding an image. Figure 3 schematically shows an embodiment in which one unit is divided into a plurality of sub-units.

In order to efficiently segment an image, a coding unit (CU) can be used in encoding and decoding. A coding unit can be used as a basic unit of video encoding/decoding. Additionally, when encoding/decoding video, a coding unit can be used as a unit that distinguishes between the intra-screen mode and the inter-screen mode. A coding unit may be a basic unit used for the process of prediction, transformation, quantization, inverse transformation, inverse quantization, or encoding/decoding of transformation coefficients.

Referring to FIG. 3, the image 300 is sequentially divided in units of largest coding units (LCUs), and the division structure is determined in units of LCUs. Here, LCU may be used in the same sense as Coding Tree Unit (CTU). Division of a unit may mean division of a block corresponding to the unit. Block division information may include information about the depth of the unit. Depth information may indicate the number and/or extent to which a unit is divided. One unit can be hierarchically divided with depth information based on a tree structure. Each divided sub-unit may have depth information. Depth information may be information indicating the size of a CU and may be stored for each CU.

The division structure may refer to the distribution of coding units (CUs) within the LCU 310. This distribution can be determined depending on whether to divide one CU into multiple CUs (positive integers greater than 2, including 2, 4, 8, 16, etc.). The horizontal and vertical sizes of the CU created by division are half the horizontal size and half the vertical size of the CU before division, respectively, or, depending on the number of divisions, are smaller than the horizontal size and vertical size of the CU before division. You can have it. A CU can be recursively divided into multiple CUs. Division of the CU can be done recursively up to a predefined depth or 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 with the maximum coding unit size as described above, and the SCU may be a coding unit with the minimum coding unit size. Division begins from the LCU 310, and the depth of the CU increases by 1 each time the horizontal and/or vertical size of the CU decreases due to division.

Additionally, information about whether the CU is divided can be expressed through the division information of the CU. Segmentation information may be 1 bit of information. All CUs except SCU may include segmentation information. For example, if the value of the division information is the first value, the CU may not be divided, and if the value of the division information is the second value, the CU may be divided.

Referring to FIG. 3, an LCU with a depth of 0 may be a 64x64 block. 0 may be the minimum depth. A SCU with a depth of 3 may be an 8x8 block. 3 may be the maximum depth. CUs of 32x32 blocks and 16x16 blocks can be expressed as depth 1 and depth 2, respectively.

For example, when one coding unit is divided into four coding units, the horizontal and vertical sizes of the four divided coding units may each be half the size compared to the horizontal and vertical sizes of the coding unit before splitting. there is. For example, when a coding unit of size 32x32 is divided into four coding units, each of the four divided coding units may have a size of 16x16. When one coding unit is divided into four coding units, the coding unit can be said to be divided in the form of a quad-tree.

For example, when one coding unit is split into two coding units, the horizontal or vertical size of the two split coding units may be half the size compared to the horizontal or vertical size of the coding unit before splitting. . For example, when a coding unit with a size of 32x32 is vertically divided into two coding units, the two divided coding units may each have a size of 16x32. When one coding unit is split into two coding units, the coding unit can be said to be split in the form of a binary tree. The LCU 320 of FIG. 3 is an example of an LCU to which both quad-tree type partitioning and binary tree-type partitioning are applied.

Figure 4 is a diagram for explaining an embodiment of the inter-screen prediction process.

The square shown in FIG. 4 may represent an image. Additionally, in Figure 4, the arrow may indicate the prediction direction. Each video can be classified into I-picture (Intra Picture), P-picture (Predictive Picture), B-picture (Bi-predictive Picture), etc. depending on the encoding type.

I-pictures can be encoded through intra-screen prediction without inter-screen prediction. A P picture can be encoded through inter-prediction using only reference images that exist in one direction (eg, forward or reverse). B pictures can be encoded through inter-prediction using reference pictures existing in both directions (eg, forward and reverse). Here, when inter-screen prediction is used, the encoder can perform inter-screen prediction or motion compensation, and the decoder can perform corresponding motion compensation.

Below, inter-screen prediction according to the embodiment is described in detail.

Inter-screen prediction or motion compensation can be performed using reference pictures and motion information.

Motion information for the current block may be derived by each of the encoding device 100 and the decoding device 200 during inter-screen prediction. The motion information may be derived using motion information of a restored neighboring block, motion information of a collocated block (col block), and/or a block adjacent to the collocated block. The collocated block may be a block corresponding to the spatial location of the current block within an already restored collocated picture (col picture). Here, the call picture may be one picture among at least one reference picture included in the reference picture list.

The method of deriving motion information may vary depending on the prediction mode of the current block. For example, prediction modes applied for inter-screen prediction may include AMVP mode, merge mode, skip mode, and current picture reference mode. Here, the merge mode may be referred to as motion merge mode.

For example, when AMVP is applied as the prediction mode, at least one of the motion vector of the restored neighboring block, the motion vector of the call block, the motion vector of the block adjacent to the call block, and the (0, 0) motion vector is used as the motion vector. By determining the candidate, a motion vector candidate list can be generated. A motion vector candidate can be derived using the generated motion vector candidate list. The motion information of the current block can be determined based on the derived motion vector candidate. Here, the motion vector of the call block or the motion vector of the block adjacent to the call block may be referred to as a temporal motion vector candidate, and the motion vector of the restored neighboring block may be referred to as a spatial motion vector candidate. ) can be referred to as.

The encoding device 100 can calculate a motion vector difference (MVD) between the motion vector of the current block and the motion vector candidate, and entropy encode the MVD. Additionally, the encoding device 100 may generate a bitstream by entropy encoding the motion vector candidate index. The motion vector candidate index may indicate an optimal motion vector candidate selected from motion vector candidates included in the motion vector candidate list. The decoding device 200 entropy-decodes the motion vector candidate index from the bitstream, and selects the motion vector candidate of the decoding target block from among the motion vector candidates included in the motion vector candidate list using the entropy-decoded motion vector candidate index. . Additionally, the decoding device 200 may derive the motion vector of the decoding target block through the sum of the entropy-decoded MVD and the motion vector candidate.

The bitstream may include a reference image index indicating a reference picture. The reference image index may be entropy encoded and signaled from the encoding device 100 to the decoding device 200 through a bitstream. The decoding device 200 may generate a prediction block for the decoding target block based on the derived motion vector and reference image index information.

Another example of a method for deriving motion information is merge mode. Merge mode may mean merging movements of a plurality of blocks. Merge mode may refer to a mode in which motion information of the current block is derived from motion information of neighboring blocks. When the merge mode is applied, a merge candidate list can be generated using motion information of the restored neighboring blocks and/or motion information of the call block. The motion information may include at least one of 1) a motion vector, 2) a reference image index, and 3) an inter-screen prediction indicator. Prediction indicators can be unidirectional (L0 prediction, L1 prediction) or bidirectional.

The merge candidate list may represent a list in which motion information is stored. The motion information stored in the merge candidate list includes motion information of neighboring blocks adjacent to the current block (spatial merge candidate) and motion information of the block corresponding to the current block in the reference image (collocated) (temporal merge candidate). temporal merge candidate)), may be at least one of new motion information generated by a combination of motion information already existing in the merge candidate list and a zero merge candidate.

The encoding device 100 may generate a bitstream by entropy encoding at least one of the merge flag and the merge index and then signal the bitstream to the decoding device 200. The merge flag may be information indicating whether to perform merge mode for each block, and the merge index may be information about which block to merge with among neighboring blocks adjacent to the current block. For example, neighboring blocks of the current block may include at least one of a left neighboring block, a top neighboring block, and a temporal neighboring block of the current block.

Skip mode may be a mode in which movement information of surrounding blocks is applied to the current block as is. When skip mode is used, the encoding device 100 may entropy encode information about which block's motion information will be used as the motion information of the current block and signal it to the decoding device 200 through a bitstream. At this time, the encoding device 100 may not signal syntax elements related to at least one of motion vector difference information, coding block flag, and transform coefficient level to the decoding device 200.

The current picture reference mode may refer to a prediction mode using a pre-restored area within the current picture to which the current block belongs. At this time, a vector may be defined to specify the pre-restored area. Whether the current block is encoded in the current picture reference mode can be encoded using the reference image 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, or may be inferred through the reference image index of the current block. If the current block is encoded in the current picture reference mode, the current picture may be added to a fixed position or a random position within the reference picture list for the current block. For example, the fixed position may be a position where the reference image index is 0 or the very last position. When the current picture is added to a random position in the reference picture list, a separate reference picture index indicating the random position may be signaled.

Based on the above, let us look in detail at the video encoding/decoding method according to the present invention.

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

Referring to FIG. 5, the encoding device may derive a motion vector candidate (S501) and generate a motion vector candidate list based on the derived motion vector candidate (S502). Once the motion vector candidate list is generated, a motion vector can be determined using the generated motion vector candidate list (S503), and motion compensation can be performed using the motion vector (S504). Afterwards, the encoding device may entropy encode information about motion compensation (S505).

Referring to FIG. 6, the decoding device can entropy decode information about motion compensation received from the encoding device (S601) and derive a motion vector candidate (S602). Then, the decoding device can generate a motion vector candidate list based on the derived motion vector candidate (S603) and determine a motion vector using the generated motion vector candidate list (S604). Afterwards, the decoding device can perform motion compensation using the motion vector (S605).

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

Referring to FIG. 7, the encoding device may derive a merge candidate (S701) and generate a merge candidate list based on the derived merge candidate. When the merge candidate list is generated, motion information can be determined using the generated merge candidate list (S702), and motion compensation of the current block can be performed using the determined motion information (S703). Afterwards, the encoding device may entropy encode information about motion compensation (S704).

Referring to FIG. 8, the decoding device entropy decodes the information about motion compensation received from the encoding device (S801), derives a merge candidate (S802), and generates a merge candidate list based on the derived merge candidate. . When the merge candidate list is generated, the motion information of the current block can be determined using the generated merge candidate list (S803). Afterwards, the decoding device can perform motion compensation using the motion information (S804).

Here, FIGS. 5 and 6 may be an example in which the AMVP mode described in FIG. 4 is applied, and FIGS. 7 and 8 may be an example in which the merge mode described in FIG. 4 is applied.

Below, each step shown in FIGS. 5 and 6 will be described, and then each step shown in FIGS. 7 and 8 will be described. However, the description of the motion compensation performance step (S504, S605, S703, S804) and the entropy encoding/decoding step (S505, S601, S704, S801) should be described in an integrated manner.

Hereinafter, each step shown in FIGS. 5 and 6 will be looked at in detail.

First, the step of deriving a motion vector candidate will be described in detail (S501, S602).

The motion vector candidate for the current block may include at least one of a spatial motion vector candidate or a temporal motion vector candidate.

The spatial motion vector of the current block may be derived from reconstructed blocks surrounding the current block. As an example, the motion vector of a reconstructed block surrounding the current block may be determined as a spatial motion vector candidate for the current block.

Figure 9 is a diagram for explaining an example of deriving a spatial motion vector candidate for the current block.

Referring to FIG. 9, the spatial motion vector candidate of the current block may be derived from neighboring blocks adjacent to the current block (X). Here, the surrounding blocks adjacent to the current block are the block adjacent to the top of the current block (B1), the block adjacent to the left of the current block (A1), the block adjacent to the upper right corner of the current block (B0), and the upper left of the current block. It may include at least one of a block (B2) adjacent to a corner and a block (A0) adjacent to the lower left corner of the current block. Meanwhile, neighboring blocks adjacent to the current block may be square or non-square. If a motion vector exists in a neighboring block adjacent to the current block, the motion vector of the neighboring block may be determined as a spatial motion vector candidate for the current block. Whether the motion vector of the neighboring block exists or whether the motion vector of the neighboring block is available as a spatial motion vector candidate for the current block is based on whether the neighboring block exists or whether the neighboring block was encoded through inter-screen prediction. It can be judged as At this time, whether the motion vector of the neighboring block exists or whether the motion vector of the neighboring block can be used as a spatial motion vector candidate for the current block may be determined according to a predetermined priority. For example, in the example shown in FIG. 9, the availability of motion vectors may be determined in the order of blocks at positions A0, A1, B0, B1, and B2.

If the reference image of the current block and the reference image of a neighboring block having a motion vector are different, a scaled motion vector of the neighboring block may be determined as a spatial motion vector candidate for the current block. Here, scaling may be performed based on at least one of the distance between the current image and the reference image referenced by the current block and the distance between the current image and the reference image referenced by the surrounding block. As an example, the spatial motion vector candidate of the current block is derived by scaling the motion vector of the surrounding block according to the ratio of the distance between the current image and the reference image referenced by the current block and the distance between the current image and the reference image referenced by the surrounding block. It can be.

Meanwhile, if the reference image index of the current block and the reference image index of a neighboring block having a motion vector are different, a scaled motion vector of the neighboring block may be determined as a spatial motion vector candidate for the current block. Even in this case, scaling may be performed based on at least one of the distance between the current image and the reference image referenced by the current block and the distance between the current image and the reference image referenced by the surrounding block.

Regarding scaling, the motion vector of a neighboring block can be determined as a spatial motion vector candidate by scaling it based on a reference image indicated by a reference image index with a predefined value. At this time, the predefined value may be a positive integer including 0. As an example, the distance between the current image and the reference image of the current block indicated by the reference image index with a predefined value and the distance between the current image and the reference image of the surrounding block with a predefined value are used to determine the distance between the current image and the reference image of the surrounding block with a predefined value. By scaling the motion vector, a spatial motion vector candidate for the current block can be derived.

Additionally, a spatial motion vector candidate of the current block may be derived based on at least one of the encoding parameters of the current block.

The temporal motion vector candidate of the current block may be derived from the reconstructed block included in the co-located picture of the current image. Here, the corresponding position image is an image for which encoding/decoding has been completed before the current image, and may be an image with a different temporal order from the current image.

Figure 10 is a diagram for explaining an example of deriving a temporal motion vector candidate for the current block.

Referring to FIG. 10, in the collocated picture of the current image, a block containing the upper position of the block corresponding to the spatially identical position as the current block (X) or a position spatially identical to the current block (X) A temporal motion vector candidate of the current block can be derived from a block containing the internal location of the block corresponding to . Here, the temporal motion vector candidate may mean the motion vector of the corresponding position block. As an example, the temporal motion vector candidate of the current block ( can be derived from Block H or block C3, etc., used to derive the temporal motion vector candidate of the current block, may be called a 'collocated block'.

Additionally, based on at least one of the encoding parameters, at least one of a temporal motion vector candidate, a corresponding location image, a corresponding location block, a prediction list utilization flag, and a reference image index may be derived.

If the distance between the current image containing the current block and the reference image of the current block is different from the distance between the corresponding location image containing the corresponding location block and the reference image of the corresponding location block, the temporal motion vector candidate of the current block is the corresponding location. It can be obtained by scaling the motion vector of the block. Here, scaling may be performed based on at least one of the distance between the current image and the reference image referenced by the current block and the distance between the corresponding location image and the reference image referenced by the corresponding location block. For example, by scaling the motion vector of the corresponding location block according to the ratio of the distance between the current image and the reference image referenced by the current block and the distance between the corresponding location image and the reference image referenced by the corresponding location block, the temporal motion vector of the current block Candidates can be induced.

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

Generating a motion vector candidate list may include adding or removing a motion vector candidate to the motion vector candidate list and adding a combined motion vector candidate to the motion vector candidate list.

Starting with the step of adding or removing the derived motion vector candidate to the motion vector candidate list, the encoding device and the decoding device can add the derived motion vector candidate to the motion vector candidate list in the order of derivation of the motion vector candidate.

It is assumed that the motion vector candidate list mvpListLX means a motion vector candidate list corresponding to the reference video lists L0, L1, L2, and L3. For example, the motion vector candidate list corresponding to L0 in the reference video list may be called mvpListL0.

In addition to the spatial motion vector candidate and the temporal motion vector candidate, a motion vector with a predetermined value may be added to the motion vector candidate list. For example, if the number of motion vector candidates included in the motion vector list is smaller than the maximum number of motion vector candidates, a motion vector with a value of 0 may be added to the motion vector candidate list.

Next, we will look at the step of adding the combined motion vector candidate to the motion vector candidate list.

If the number of motion vector candidates included in the motion vector candidate list is smaller than the maximum number of motion vector candidates, a motion vector combined using at least one of the motion vector candidates included in the motion vector candidate list is added to the motion vector candidate list. can do. As an example, a combined motion vector candidate is generated using at least one of a spatial motion vector candidate, a temporal motion vector candidate, and a zero motion vector candidate included in the motion vector candidate list, and the generated combined motion vector candidate is moved. It can be included in the vector candidate list.

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

Next, we will look at the step of determining a predicted motion vector from the motion vector candidate list (S503, S604).

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 for the current block.

The encoding device may calculate the difference between the motion vector and the predicted motion vector and calculate the motion vector difference value. The decoding device can calculate a motion vector by adding the predicted motion vector and the motion vector difference.

Meanwhile, the steps of performing motion compensation (S504, S605) of FIGS. 5 and 6 and the steps of entropy encoding/decoding information about motion compensation (S505, S601) are the same as the steps of performing motion compensation (S703) of FIGS. 7 and 8. , S804) and entropy encoding/decoding steps (S704, S801) and will be described later.

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

First, the steps for deriving merge candidates will be described in detail (S701, 802).

Merge candidates for the current block may include at least one of a spatial merge candidate, a temporal merge candidate, or an additional merge candidate. Here, deriving a spatial merge candidate may mean deriving a spatial merge candidate and adding it to the merge candidate list.

Referring to FIG. 9, a spatial merge candidate for the current block may be derived from neighboring blocks adjacent to the current block (X). The surrounding blocks adjacent to the current block are the block adjacent to the top of the current block (B1), the block adjacent to the left of the current block (A1), the block adjacent to the upper right corner of the current block (B0), and the block adjacent to the upper left corner of the current block. It may include at least one of an adjacent block (B2) and a block (A0) adjacent to the lower left corner of the current block.

In order to derive a spatial merge candidate for the current block, it can be determined whether neighboring blocks adjacent to the current block can be used to derive a spatial merge candidate for the current block. At this time, whether a neighboring block adjacent to the current block can be used to derive a spatial merge candidate for the current block may be determined according to a predetermined priority. For example, in the example shown in FIG. 9, the availability of spatial merge candidate induction may be determined in the order of blocks at positions A1, B1, B0, A0, and B2. Spatial merge candidates determined based on the availability determination order can be sequentially added to the merge candidate list of the current block.

Figure 11 is a diagram to explain an example in which a spatial merge candidate is added to the merge candidate list.

Referring to FIG. 11, when four spatial merge candidates are derived from neighboring blocks at positions A1, B0, A0, and B2, the derived spatial merge candidates may be sequentially added to the merge candidate list.

Additionally, the spatial merge candidate may be derived based on at least one of the encoding parameters.

Here, the motion information of the spatial merge candidate may include three or more pieces of motion information, including L2 and L3, as well as motion information of L0 and L1. Here, the reference image list may include at least one image, such as L0, L1, L2, and L3.

Next, we will explain how to derive a temporal merge candidate for the current block.

A temporal merge candidate for the current block may be derived from a reconstructed block included in a co-located picture of the current image. Here, the corresponding position image is an image for which encoding/decoding has been completed before the current image, and may be an image with a different temporal order from the current image.

Deriving a temporal merge candidate may mean deriving a temporal merge candidate and adding it to the merge candidate list.

Referring to FIG. 10, in the collocated picture of the current image, a block containing the upper position of the block corresponding to the spatially identical position as the current block (X) or a position spatially identical to the current block (X) A temporal merge candidate for the current block can be derived from a block containing the internal location of the block corresponding to . Here, the temporal merge candidate may mean motion information of the corresponding location block. As an example, a temporal merge candidate for the current block can be induced. Block H or block C3, etc., used to derive a temporal merge candidate for the current block, may be called a 'collocated block'.

If a temporal merge candidate for the current block can be derived from block H that includes the external location of block C, block H may be set as the corresponding location block of the current block. In this case, the temporal merge candidate of the current block can be derived based on the motion information of block H. On the other hand, if a temporal merge candidate for the current block cannot be derived from block H, block C3, which includes the internal location of block C, may be set as the corresponding location block of the current block. In this case, the temporal merge candidate for the current block can be derived based on the motion information of block C3. If the temporal merge of the current block cannot be derived from block H and block C3 (e.g., when both block H and block C3 are intra-coded), the temporal merge candidate for the current block is not derived or the block It may be derived from a block at a different location than H and block C3.

As another example, a temporal merge candidate for the current block may be derived from a plurality of blocks in the corresponding location image. As an example, a plurality of temporal merge candidates for the current block may be derived from block H and block C3.

Figure 12 is a diagram for explaining an example in which a temporal merge candidate is added to the merge candidate list.

Referring to FIG. 12, when one temporal merge candidate is derived from a block at the corresponding position of H1, the derived temporal merge candidate can be added to the merge candidate list.

If the distance between the current image containing the current block and the reference image of the current block is different from the distance between the corresponding location image containing the corresponding location block and the reference image of the corresponding location block, the motion vector of the temporal merge candidate of the current block is It can be obtained by scaling the motion vector of the corresponding position block. Here, scaling may be performed based on at least one of the distance between the current image and the reference image referenced by the current block and the distance between the corresponding location image and the reference image referenced by the corresponding location block. For example, by scaling the motion vector of the corresponding location block according to the ratio of the distance between the current image and the reference image referenced by the current block and the distance between the corresponding location image and the reference image referenced by the corresponding location block, the temporal merge candidate of the current block is generated. A motion vector of can be derived.

In addition, at least one of a temporal merge candidate, a corresponding location image, a corresponding location block, a prediction list utilization flag, and a reference image index may be derived based on at least one of the encoding parameters of the current block, the neighboring block, or the corresponding location block.

After deriving at least one of the spatial merge candidates and the temporal merge candidates, the merge candidate list can be generated by adding them to the merge candidate list in the order of the derived merge candidates.

Next, we will explain how to derive additional merge candidates for the current block.

The additional merge candidate means at least one of a modified spatial merge candidate, a modified temporal merge candidate, a combined merge candidate, and a merge candidate with a predetermined motion information value. can do. Here, deriving additional merge candidates may mean deriving additional merge candidates and adding them to the merge candidate list.

A changed spatial merge candidate may mean a merge candidate in which at least one piece of motion information of the derived spatial merge candidate has been changed.

A changed temporal merge candidate may mean a merge candidate in which at least one piece of motion information of the derived temporal merge candidate has been changed.

The combined merge candidate is at least one of motion information of spatial merge candidates, temporal merge candidates, changed spatial merge candidates, changed temporal merge candidates, combined merge candidates, and merge candidates with a predetermined motion information value that exist in the merge candidate list. It may refer to a merge candidate derived by combining motion information.

Alternatively, the combined merge candidate is a spatial merge candidate and a derived temporal merge candidate derived from a block that does not exist in the merge candidate list but can induce at least one of the spatial merge candidate and the temporal merge candidate, and the changed merge candidate generated based thereon. It may refer to a merge candidate derived by combining motion information of at least one of a spatial merge candidate, a modified temporal merge candidate, a combined merge candidate, and a merge candidate with a predetermined motion information value.

Alternatively, the decoder can derive a combined merge candidate using motion information entropy-decoded from the bitstream. At this time, the motion information used to derive the combined merge candidate in the encoder may be entropy-encoded into the bitstream.

A combined merge candidate may mean a combined positive prediction merge candidate. A combined bi-prediction merge candidate is a merge candidate that uses bi-prediction and may refer to a merge candidate that has L0 motion information and L1 motion information.

A merge candidate with a predetermined motion information value may mean a zero merge candidate with a motion vector of (0, 0). Meanwhile, a merge candidate with a predetermined motion information value may be preset to use the same value in the encoding device and the decoding device.

Deriving at least one of a changed spatial merge candidate, a changed temporal merge candidate, a combined merge candidate, and a merge candidate having a predetermined motion information value based on at least one of the encoding parameters of the current block, neighboring blocks, or the corresponding position block, or can be created. In addition, at least one of a changed spatial merge candidate, a changed temporal merge candidate, a combined merge candidate, and a merge candidate having a predetermined motion information value is used based on at least one of the encoding parameters of the current block, neighboring blocks, or the corresponding position block. It can be added to the merge candidate list.

Meanwhile, the size of the merge candidate list may be determined based on the encoding parameters of the current block, neighboring blocks, or corresponding location blocks, and the size may be changed based on the encoding parameters.

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

The encoder may determine a merge candidate used for motion compensation among the merge candidates in the merge candidate list through motion estimation, and encode a merge candidate index (merge_idx) indicating the determined merge candidate into the bitstream.

Meanwhile, in order to generate a prediction block, the encoder can determine motion information of the current block by selecting a merge candidate from the merge candidate list based on the above-described merge candidate index. Here, motion compensation can be performed based on the determined motion information to generate a prediction block of the current block.

The decoder can decode the merge candidate index in the bitstream and determine the merge candidate in the merge candidate list indicated by the merge candidate index. The determined merge candidate can be determined based on the movement information of the current block. The determined motion information is used for motion compensation of the current block. At this time, motion compensation may have the same meaning as inter prediction.

Next, we will look at the steps of performing motion compensation using a motion vector or motion information (S504, S605, S703, S804).

The encoding device and the decoding device can calculate a motion vector using the predicted motion vector and the motion vector difference value. Once the motion vector is calculated, inter-screen prediction or motion compensation can be performed using the calculated motion vector (S504, S605).

Meanwhile, the encoding device and the decoding device can perform inter-screen 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 can have from a minimum of 1 to a maximum of N motion vectors depending on the prediction direction. Using the motion vector, a minimum of 1 to a maximum of N prediction blocks can be generated to derive the final prediction block of the current block.

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

On the other hand, if the current block has multiple motion vectors (or motion information), multiple prediction blocks are generated using multiple motion vectors (or motion information), and based on the weighted sum of the multiple prediction blocks, the current block is The final prediction block of the block can be determined. Reference images including each of a plurality of prediction blocks indicated by a plurality of motion vectors (or motion information) may be included in different reference image lists or in the same reference image list.

As an example, a plurality of prediction blocks are generated based on at least one of a spatial motion vector candidate, a temporal motion vector candidate, a motion vector with a predetermined value, or a combined motion vector candidate, and based on a weighted sum of the plurality of prediction blocks. , the final prediction block of the current block can be determined.

As another example, a plurality of prediction blocks may be generated based on motion vector candidates indicated by a preset motion vector candidate index, and the final prediction block of the current block may be determined based on a weighted sum of the plurality of prediction blocks. Additionally, a plurality of prediction blocks may be generated based on motion vector candidates existing in a preset motion vector candidate index range, and the final prediction block of the current block may be determined based on a weighted sum of the plurality of prediction blocks.

The weight applied to each prediction block may have a uniform value of 1/N (where N is the number of generated prediction blocks). For example, when 2 prediction blocks are generated, the weight applied to each prediction block is 1/2, and when 3 prediction blocks are created, the weight applied to each prediction block is 1/3, and 4 prediction blocks are generated. When a block is generated, the weight applied to each prediction block may be 1/4. Alternatively, the final prediction block of the current block may be determined by assigning different weights to each prediction block.

The weight does not have to have a fixed value for each prediction block, and may have a variable value for each prediction block. At this time, the weights applied to each prediction block may be the same or different. For example, when two prediction blocks are generated, the weights applied to the two prediction blocks are not only (1/2, 1/2), but also (1/3, 2/3), (1/4, 3) The value may be variable for each block, such as /4), (2/5, 3/5), (3/8, 5/8), etc. Meanwhile, the weight may be a positive real number or a negative real number. For example, it may include negative real numbers such as (-1/2, 3/2), (-1/3, 4/3), (-1/4, 5/4), etc.

Meanwhile, in order to apply variable weights, one or more weight information for the current block may be signaled through the bitstream. Weight information may be signaled separately for each prediction block or may be signaled for each reference image. It is also possible for multiple prediction blocks to share one weight information.

The encoding device and the decoding device can determine whether to use the predicted motion vector (or motion information) based on the prediction block list utilization flag. For example, when the prediction block list utilization flag for each reference video list indicates the first value of 1, the encoding device and the decoding device can use the predicted motion vector of the current block to perform inter-screen prediction or motion compensation. When indicating the second value of 0, it may indicate that the encoding device and the decoding device do not perform inter-screen prediction or motion compensation using the predicted motion vector of the current block. Meanwhile, the first value of the prediction block list utilization flag may be set to 0 and the second value may be set to 1. Equations 1 to 3 below are an example of generating the final prediction block of the current block when the inter-screen prediction indicators of the current block are PRED_BI, PRED_TRI, and PRED_QUAD, and the prediction direction for each reference image list is unidirectional. represents.

In Equations 1 to 3, P_BI, P_TRI, and P_QUAD may represent the final prediction block of the current block, and LX (X=0, 1, 2, 3) may represent a reference image list. WF_LX may represent the weight value of the prediction block generated using LX, and OFFSET_LX may represent the offset value for the prediction block generated using LX. P_LX refers to a prediction block generated using the motion vector (or motion information) for the LX of the current block. RF stands for rounding factor and can be set to 0, positive or negative. The LX reference image list includes a long-term reference image, a reference image without deblocking filter, a reference image without sample adaptive offset, and an adaptive loop filter. A reference image without performing a loop filter, a reference image with only a deblocking filter and an adaptive offset, a reference image with only a deblocking filter and an adaptive loop filter, and a reference image with only an adaptive offset and an adaptive loop filter. The image, deblocking filter, sample adaptive offset, and adaptive loop filter may all include at least one of the reference images performed. In this case, the LX reference image list may be at least one of an L2 reference image list and an L3 reference image list.

Even when the prediction direction for a given reference image list is multiple directions, the final prediction block for the current block can be obtained based on the weighted sum of the prediction blocks. At this time, weights applied to prediction blocks derived from the same reference image list may have the same value or different values.

At least one of the weight (WF_LX) and offset (OFFSET_LX) for a plurality of prediction blocks may be an encoding parameter that is entropy encoded/decoded. As another example, the weight and offset may be derived from encoded/decoded neighboring blocks surrounding the current block. Here, the neighboring blocks surrounding the current block may include at least one of a block used to derive a spatial motion vector candidate of the current block or a block used to derive a temporal motion vector candidate of the current block.

As another example, the weight and offset may be determined based on the display order (POC) of the current image and each reference image. In this case, as the distance between the current image and the reference image increases, the weight or offset can be set to a small value, and as the distance between the current image and the reference image decreases, the weight or offset can be set to a large value. For example, if the POC difference between the current image and the L0 reference image is 2, the weight value applied to the prediction block generated with reference to the L0 reference image is set to 1/3, while the POC difference between the current image and the L0 reference image is set to 1/3. If is 1, the weight value applied to the prediction block generated with reference to the L0 reference image can be set to 2/3. As illustrated above, the weight or offset value may have an inverse relationship with the display order difference between the current image and the reference image. As another example, it is also possible to have the weight or offset value have a proportional relationship with the display order difference between the current image and the reference image.

As another example, based on at least one of the encoding parameters, at least one of the weight or offset may be entropy encoded/decoded. Additionally, a weighted sum of prediction blocks may be calculated based on at least one of the encoding parameters.

The weighted sum of multiple prediction blocks can be applied only to some areas within the prediction block. Here, some areas may be areas corresponding to boundaries within the prediction block. In order to apply the weighted sum only to some areas as above, the weighted sum can be performed in sub-block units of the prediction block.

Inter-screen prediction or motion compensation can be performed on sub-blocks with a smaller block size within a block of the block size indicated by the region information using the same prediction block or the same final prediction block.

Additionally, inter-screen prediction or motion compensation can be performed using the same prediction block or the same final prediction block in sub-blocks with a deeper block depth within a block of the block depth indicated by the region information.

Additionally, when calculating the weighted sum of prediction blocks using motion vector prediction, the weighted sum can be calculated using at least one motion vector candidate existing in the motion vector candidate list and used as the final prediction block of the current block.

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

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

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

For example, prediction blocks can be generated only from motion vector candidates having specific motion vector candidate indices, a weighted sum of the prediction blocks can be calculated, and the calculated weighted sum can be used as the final prediction block of the current block.

For example, prediction blocks can be generated only from motion vector candidates that exist within a specific motion vector candidate index range, a weighted sum of the prediction blocks can be calculated, and the calculated weighted sum can be used as the final prediction block of the current block.

Additionally, when calculating the weighted sum of prediction blocks using the merge mode, the weighted sum can be calculated using at least one merge candidate existing in the merge candidate list and used as the final prediction block of the current block.

For example, prediction blocks can be generated only from spatial merge candidates, the weighted sum of the prediction blocks can be calculated, and the calculated weighted sum can be used as the final prediction block of the current block.

For example, prediction blocks can be generated from spatial merge candidates and temporal merge candidates, the weighted sum of the prediction blocks can be calculated, and the calculated weighted sum can be used as the final prediction block of the current block.

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

For example, prediction blocks can be generated only from merge candidates with specific merge candidate indices, a weighted sum of the prediction blocks can be calculated, and the calculated weighted sum can be used as the final prediction block of the current block.

For example, prediction blocks can be generated only from merge candidates that exist within a specific merge candidate index range, a weighted sum of the prediction blocks can be calculated, and the calculated weighted sum can be used as the final prediction block of the current block.

The encoder and decoder can perform motion compensation using the motion vector/information contained in the current block. At this time, the final prediction block that is the result of motion compensation may be generated using at least one prediction block. Here, the current block may mean at least one of a current coding block and a current prediction block.

The final prediction block can be generated by performing overlapped block motion compensation in the area corresponding to the boundary within the current block.

The area corresponding to the boundary within the current block may be an area within the current block adjacent to the boundary of a neighboring block of the current block. Here, the area corresponding to the border within the current block is one of the upper border area, left border area, lower border area, right border area, upper right corner area, lower right corner area, upper left corner area, and lower left corner area in the current block. It may contain at least one or more. Additionally, the area corresponding to the boundary within the current block may be an area corresponding to a portion of the prediction block of the current block.

The overlapped block motion compensation performs motion compensation by calculating a weighted sum of the prediction block generated using the prediction block area corresponding to the boundary within the current block and the motion information of the encoded/decoded block adjacent to the current block. It can mean.

Weighted sum can be performed on a sub-block basis after dividing the current block into multiple sub-blocks. That is, motion compensation can be performed on a sub-block basis using motion information of an encoded/decoded block adjacent to the current block. At this time, the sub-block may mean a sub-block.

In addition, in calculating the weighted sum, a first prediction block generated in sub-block units using motion information of the current block and a second prediction block generated using motion information of surrounding sub-blocks spatially adjacent to the current block may be used. . At this time, using motion information may mean deriving motion information. Additionally, the first prediction block may refer to a prediction block generated using motion information of a sub-block to be encoded/decoded within the current block. Additionally, here, the second prediction block may refer to a prediction block generated using motion information of neighboring sub-blocks spatially adjacent to the encoding/decoding target sub-block within the current block.

The final prediction block may be generated using the weighted sum of the first prediction block and the second prediction block. That is, overlapped block motion compensation can generate the final prediction block by using motion information of other blocks in addition to the motion information of the current block.

Additionally, Advanced Motion Vector Prediction (AMVP), merge mode, affine motion compensation mode, decoder motion vector guidance mode, adaptive motion vector resolution mode, local illumination compensation mode, and bidirectional optical flow. If at least one of the modes is applicable, the current prediction block can be divided into sub-blocks and then overlapped block motion compensation can be performed for each sub-block.

Here, in the case of merge mode, block motion compensation overlapped with at least one of the Advanced Temporal Motion Vector Predictor (ATMVP) candidate and the Spatial-Temporal Motion Vector Predictor (STMVP) candidate. can be performed.

A detailed description regarding overlapped block motion compensation will be described later based on FIGS. 13 to 24.

Next, we will look in detail at the process of entropy encoding/decoding information about motion compensation (S505, S601, S704, S801).

The encoding device can entropy-encode information about motion compensation through a bitstream, and the decoding device can entropy-decode information about motion compensation included in the bitstream. Here, information about motion compensation that is entropy encoded/decoded includes an inter prediction indicator (inter_pred_idc), reference image index (ref_idx_l0, ref_idx_l1, ref_idx_l2, ref_idx_l3), and motion vector candidate index (mvp_l0_idx, mvp_l1_idx, mvp_l2_idx). , mvp_l3_idx), motion vector difference, skip mode usage information (cu_skip_flag), merge mode usage information (merge_flag), merge index information (merge_index), weight values (wf_l0, wf_l1, wf_l2, wf_l3), and It may include at least one of the offset values (offset_l0, offset_l1, offset_l2, offset_l3).

When the inter-screen prediction indicator of the current block is encoded/decoded by inter-prediction, it may mean at least one of the inter-screen prediction direction or the number of prediction directions of the current block. As an example, the inter-screen prediction indicator may indicate one-way prediction, or may indicate multi-way prediction, such as two-way prediction, three-way prediction, or four-way prediction. The inter-screen prediction indicator may mean the number of reference images used by the current block to generate a prediction block. Alternatively, one reference image may be used for prediction of multiple directions. In this case, N(N>M) direction prediction can be performed using M reference images. The inter-screen prediction indicator may mean the number of prediction blocks used when performing inter-screen prediction or motion compensation for the current block.

The reference image indicator may indicate one-way (PRED_LX), two-way (PRED_BI), three-way (PRED_TRI), four-way (PRED_QUAD) or more directionality, depending on the number of prediction directions of the current block.

The prediction list utilization flag indicates whether a prediction block is generated using the corresponding reference image list.

As an example, when the prediction list utilization flag indicates a first value of 1, it indicates that a prediction block can be generated using the corresponding reference image list, and when it indicates a second value of 0, it indicates that the prediction block can be generated using the corresponding reference image list. This may indicate that a prediction block is not generated. Here, the first value of the prediction list utilization flag may be set to 0 and the second value may be set to 1.

That is, when the prediction list utilization flag indicates the first value, the prediction block of the current block can be generated using motion information corresponding to the corresponding reference image list.

The reference image index can specify the reference image referenced by the current block in each reference image list. For each reference image list, one or more reference image indices may be entropy encoded/decoded. The current block can perform motion compensation using one or more reference image indices.

The motion vector candidate index indicates the motion vector candidate for the current block in the motion vector candidate list generated for each reference video list or reference video index. At least one motion vector candidate index may be entropy encoded/decoded for each motion vector candidate list. The current block can perform motion compensation using at least one motion vector candidate index.

The motion vector difference represents the difference value between the motion vector and the predicted motion vector. One or more motion vector differences may be entropy encoded/decoded for a reference image list or a motion vector candidate list generated for each reference image index for the current block. The current block can perform motion compensation using one or more motion vector differences.

If the skip mode use information (cu_skip_flag) has a first value of 1, it may indicate the use of skip mode, and if it has a second value of 0, it may not indicate the use of skip mode. Motion compensation of the current block can be performed using skip mode based on information on whether skip mode is used.

If the merge mode use status information (merge_flag) has a first value of 1, it may indicate the use of merge mode, and if it has a second value of 0, it may not indicate the use of merge mode. Based on information on whether to use merge mode, motion compensation of the current block can be performed using merge mode.

Merge index information (merge_index) may refer to information indicating a merge candidate in a merge candidate list.

Additionally, merge index information may mean information about a merge index.

Additionally, merge index information may indicate a block from which a merge candidate is derived among blocks restored spatially/temporally adjacent to the current block.

Additionally, merge index information may indicate at least one piece of motion information contained in a merge candidate. For example, if the merge index information has a first value of 0, it may indicate the first merge candidate in the merge candidate list, and if it has a second value of 1, it may indicate the second merge candidate in the merge candidate list. If it has a third value of 2, it can indicate the third merge candidate in the merge candidate list. Likewise, when it has the fourth to Nth values, the merge candidate corresponding to the value can be indicated according to the order in the merge candidate list. Here, N may mean a positive integer including 0.

Merge mode Motion compensation of the current block can be performed using merge mode based on index information.

If two or more prediction blocks are generated during motion compensation for the current block, the final prediction block for the current block may be generated through a weighted sum for each prediction block. When calculating the weighted sum, at least one of a weight and an offset may be applied to each prediction block. Weighted sum factors used in weighted sum calculation, such as weighting factor or offset, are reference image list, reference image, motion vector candidate index, motion vector difference, motion vector, skip mode usage information, merge mode. Entropy may be encoded/decoded as much as at least one of usage information and merge index information, or at least one more. Additionally, the weighted sum factor of each prediction block may be entropy encoded/decoded based on the inter-prediction indicator. Here, the weighted sum factor may include at least one of a weight and an offset.

Information about motion compensation may be entropy encoded/decoded on a block basis or entropy encoded/decoded at a higher level. As an example, information about motion compensation is entropy encoded/decoded in block units such as CTU, CU, or PU, or is encoded in a video parameter set, sequence parameter set, or picture parameter set. ), may be entropy encoded/decoded at a higher level, such as an adaptation parameter set or slice header.

Information about motion compensation may be entropy encoded/decoded based on a difference value of information about motion compensation, which represents a difference value between information about motion compensation and a predicted value of information about motion compensation.

Instead of entropy encoding/decoding the information about the motion compensation of the current block, it is also possible to use the information about the motion compensation of encoded/decoded blocks around the current block as the information about the motion compensation of the current block.

Additionally, at least one piece of information regarding motion compensation may be derived based on at least one piece of encoding parameters.

Additionally, at least one piece of information related to motion compensation may be entropy decoded from a bitstream based on at least one piece of coding parameters. At least one piece of information related to motion compensation may be entropy-encoded into a bitstream based on at least one piece of coding parameters.

Information about motion compensation includes motion vector, motion vector candidate, motion vector candidate index, motion vector difference value, motion vector predicted value, information on whether skip mode is used (skip_flag), information on whether merge mode is used (merge_flag), and merge index information (merge_index). ), motion vector resolution information, overlapped block motion compensation information, local illumination compensation information, affine motion compensation information, decoder motion vector It may further include at least one of decoder-side motion vector derivation information and bi-directional optical flow information. Here, decoder motion vector derivation may mean pattern matched motion vector derivation.

Motion vector resolution information may be information indicating whether a specific resolution is used for at least one of the motion vector and the motion vector difference value. Here, resolution may mean precision. Additionally, specific resolutions include 16-pel units, 8-pel units, 4-pel units, integer-pel units, and 1/2-pel units. (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 , can be set to at least one of 1/32-pixel (1/32-pel) units and 1/64-pixel (1/64-pel) units.

The overlapping block motion compensation information may be information indicating whether the weighted sum of the prediction blocks of the current block is calculated by additionally using the motion vectors of neighboring blocks spatially adjacent to the current block when compensating for motion of the current block.

Local lighting compensation information may be information indicating whether at least one of a weight value and an offset value is applied when generating a prediction block of the current block. Here, at least one of the weight value and the offset value 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 used when compensating for motion for the current block. Here, the affine motion model may be a model that divides one block into multiple sub-blocks using a plurality of parameters and calculates motion vectors of the divided sub-blocks using representative motion vectors.

Decoder motion vector derivation information may be information indicating whether the decoder derives and uses a motion vector necessary for motion compensation. Based on the decoder motion vector derivation information, information about the motion vector may not be entropy encoded/decoded. Additionally, when the decoder motion vector derivation information indicates that the decoder derives and uses a motion vector, information about the merge mode may be entropy encoded/decoded. That is, the decoder motion vector derivation information may indicate whether the decoder uses merge mode.

Bidirectional optical flow information may be information indicating whether motion compensation is performed by correcting the motion vector on a pixel basis or a sub-block basis. Based on bidirectional optical flow information, motion vectors in pixel units or subblock units may not be entropy encoded/decoded. Here, motion vector correction may mean changing the motion vector value of a block-wise motion vector on a pixel-by-pixel or sub-block basis.

The current block may perform motion compensation using at least one piece of information about motion compensation, and entropy encode/decode at least one piece of information about motion compensation.

When entropy encoding/decoding information related to motion compensation, the Truncated Rice binarization method, K-th order Exp_Golomb binarization method, and limited K-th order Exp_Golomb ) Binarization methods such as the binarization method, fixed-length binarization method, unary binarization method, or truncated unary binarization method may be used.

When entropy encoding/decoding information about motion compensation, information about motion compensation of neighboring blocks around the current block or area information of neighboring blocks, information about previously encoded/decoded motion compensation, or previously encoded/decoded information about motion compensation A context model may be determined using at least one of area information, information about the depth of the current block, and information about the size of the current block.

In addition, when entropy encoding/decoding information about motion compensation, information about motion compensation of neighboring blocks, information about previously encoded/decoded motion compensation, information about the depth of the current block, and information about the size of the current block. Entropy encoding/decoding may be performed by using at least one piece of information as a prediction value for information about motion compensation of the current block.

Hereinafter, a detailed description related to Overlapped Block Motion Compensation will be described with reference to FIGS. 13 to 24.

*Figure 13 is a diagram illustrating an example in which overlapped block motion compensation is performed on a sub-block basis.

Referring to FIG. 13, the hatched block is an area where overlapped block motion compensation is applied and may be a subblock corresponding to the boundary within the current block or a subblock within the current block. Additionally, the block indicated by a thick line may be the current block.

Additionally, the arrow may mean that motion information of adjacent surrounding sub-blocks is used for motion compensation of the current sub-block. Here, the position corresponding to the arrow tail may mean 1) a neighboring sub-block adjacent to the current block, or 2) a neighboring sub-block adjacent to the current sub-block within the current block. Additionally, the position corresponding to the head of the arrow may mean the current sub-block within the current block.

In the hatched block, the weighted sum of the first prediction block and the second prediction block can be calculated. The motion information used when generating the first prediction block may be motion information about the current sub-block within the current block. The motion information used when generating the second prediction block may be at least one of motion information of a neighboring sub-block adjacent to the current block and motion information of a neighboring sub-block adjacent to the current sub-block within the current block.

In addition, in order to improve coding efficiency, the motion information used to generate the second prediction block is divided into upper block, left block, lower block, right block, upper right block, lower right block, upper left based on the position of the current sub-block in the current block. It may be movement information of at least one block among the block and the lower left block. The locations of available surrounding subblocks may be determined depending on the location of the current subblock. For example, when the current sub-block is located at the upper boundary, at least one surrounding sub-block located at the top, upper right, and upper left of the current sub block may be used. If the current sub-block is located at the left border, at least one surrounding sub-block located to the left, top left, and bottom left of the current sub-block can be used.

Here, based on the position of the current subblock, the top block, left block, bottom block, right block, top right block, bottom right block, top left block, and bottom left block are the top surrounding subblock, left surrounding subblock, and bottom surrounding subblock. , It can be named as right peripheral sub-block, upper-right peripheral sub-block, lower-right peripheral sub-block, upper-left peripheral sub-block, and lower-left peripheral sub-block.

Meanwhile, in order to reduce computational complexity, the motion information used to generate the second prediction block may vary depending on the size of the motion vector of the neighboring sub-block adjacent to the current block or the neighboring sub-block adjacent to the current sub-block within the current block.

For example, when neighboring sub-blocks are predicted in both directions, the sizes of motion vectors in the L0 and L1 directions can be compared to generate a second prediction block using only motion information in one direction with a larger size.

As another example, the second prediction block can be generated using only motion vectors in which the sum of the absolute values of the x and y components of the motion vectors among the L0 and L1 direction motion vectors of the surrounding sub-blocks is equal to or greater than a predefined value. . Here, the predefined value may be a positive integer including 0, may be determined by information signaled from the encoder to the decoder, or may be a value set identically to the encoder and decoder.

Additionally, in order to reduce computational complexity, the motion information used to generate the second prediction block may vary depending on the size and direction of the motion vector of the current lower block.

For example, after comparing the magnitude of the absolute value of the motion vector x component and y component of the current lower block, if the absolute value of the x component is large, a second prediction is performed using at least one of the motion information of the left block and the right block. Blocks can be created.

As another example, after comparing the magnitudes of the absolute values of the motion vector Blocks can be created.

As another example, if the absolute value of the motion vector x component of the current lower block is greater than or equal to a predefined value, a second prediction block can be generated using at least one of the motion information of the left block and the right block. . Here, the predefined value may be a positive integer including 0, may be determined by information signaled from the encoder to the decoder, or may be a value set identically to the encoder and decoder.

As another example, if the absolute value of the motion vector y component of the current lower block is greater than or equal to a predefined value, a second prediction block can be generated using at least one of the motion information of the upper block and the lower block. . Here, the predefined value may be a positive integer including 0, may be determined by information signaled from the encoder to the decoder, or may be a value set identically to the encoder and decoder.

Meanwhile, the size of the subblock may be NxM, where N and M may be positive integers. N and M may be the same or different from each other. For example, the sub-block size may be 4x4 or 8x8, and the sub-block size information may be entropy encoded/decoded in sequence units.

Additionally, the size of the subblock may be determined according to the size of the current block. For example, if the size of the current block is less than K samples, a 4x4 sub-block can be used, and if the size of the current block is larger than K samples, an 8x8 sub-block can be used. Here, K is a positive integer, for example, it can be 256.

Here, information about the size of the subblock may be entropy encoded/decoded and used in at least one of sequence units, picture units, slice units, tile units, CTU units, CU units, and PU units. Additionally, the size of the subblock can be a predefined size in the encoder and decoder.

The sub-block may have at least one of a square shape and a rectangular shape. For example, if the current block is square or rectangular, the lower block may be square.

For example, if the current block has a rectangular shape, the subblock may have a rectangular shape.

Here, information about the shape of the subblock may be entropy encoded/decoded and used in at least one of sequence units, picture units, slice units, tile units, CTU units, CU units, and PU units. Additionally, the encoder and decoder can use predefined shapes of the lower blocks.

FIG. 14 is a diagram illustrating an example in which overlapped block motion compensation is performed using motion information of a sub-block of a corresponding location block. To improve coding efficiency, motion information of a corresponding location sub-block corresponding to the same spatial position as the current block in the corresponding location image or reference image can be used as motion information used to generate the second prediction block.

Referring to FIG. 14, motion information of a sub-block temporally adjacent to the current block within the corresponding location block can be used to compensate for motion of an overlapped block of the current sub-block. Here, the position corresponding to the arrow tail may mean a sub-block within the corresponding position block. Additionally, the position corresponding to the head of the arrow may mean the current sub-block within the current block.

In addition, as described above, motion information of at least one of the motion information of the corresponding position sub-block in the corresponding position image, motion information of neighboring sub-blocks spatially adjacent to the current block, and neighboring sub-blocks spatially adjacent to the current sub-block within the current block. Can be used to generate the second prediction block.

FIG. 15 is a diagram illustrating an example in which overlapped block motion compensation is performed using motion information of blocks adjacent to the boundary area of a reference block. To improve coding efficiency, identify a reference block in the reference image using at least one of the motion vector of the current block and the reference image index, and generate a second prediction block using the motion information of a neighboring block adjacent to the boundary of the identified reference block. It can be used as movement information used in . Here, the neighboring block may include an encoded/decoded block adjacent to a lower block located in the lower border area or the right border area of the reference block.

Referring to FIG. 15, motion information of blocks encoded/decoded adjacent to the lower border area and the right border area of the reference block can be used to compensate for motion of the overlapped block of the current lower block.

In addition, as described above, motion information of blocks encoded/decoded adjacent to the lower border area and right border area of the reference block, motion information of neighboring sub-blocks spatially adjacent to the current block, and spatial information to the current sub-block within the current block. Motion information of at least one of adjacent neighboring sub-blocks may be used to generate the second prediction block.

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

As an example, a spatial merge candidate in the merge candidate list can be used as motion information used to generate the second prediction block.

As another example, a temporal merge candidate in the merge candidate list can be used as motion information used to generate the second prediction block.

As another example, merge candidates combined within the merge candidate list can be used as motion information used to generate the second prediction block.

Alternatively, to improve coding efficiency, at least one motion vector among motion vector candidates included in the motion vector candidate list can be used as a motion vector used to generate the second prediction block. Here, the motion vector candidate list may be a list used in AMVP mode among inter-screen prediction modes.

As an example, a spatial motion vector candidate in the motion vector candidate list can be used as motion information used to generate a second prediction block.

As another example, a temporal motion vector candidate in the motion vector candidate list can be used as motion information used to generate the second prediction block.

When at least one of the above-described merge candidate and motion vector candidate is used as motion information used to generate the second prediction block, the area to which overlapped block motion compensation is applied may be varied. The area to which overlapped block motion compensation is applied is set to an area adjacent to one border of the block (i.e., a sub-block located on the block boundary) or an area not adjacent to the block boundary (i.e., a sub-block not located on the block boundary). It can be.

In this case, block motion compensation overlapping in an area not adjacent to a block boundary may use at least one of a merge candidate and a motion vector candidate as motion information used in the second prediction block.

As an example, motion compensation for blocks overlapped in an area not adjacent to a block boundary can be performed using motion information of a spatial merge candidate or a spatial motion vector candidate.

As another example, motion compensation for blocks overlapped in an area not adjacent to a block boundary can be performed using motion information of a temporal merge candidate or a temporal motion vector candidate.

As another example, motion compensation for blocks overlapped in the lower border area and right border area of a block can be performed using motion information of a spatial merge candidate or a spatial motion vector candidate.

As another example, motion compensation for blocks overlapped in the lower border area and right border area of the block can be performed using the motion information of the temporal merge candidate or the temporal motion vector candidate.

Additionally, in order to improve coding efficiency, motion information derived from a specific location block in the merge candidate list or motion vector candidate list can be used when compensating motion of overlapping blocks for a specific area.

For example, if the merge candidate list or the motion vector candidate list includes motion information derived from the upper right block based on the current block, the corresponding motion information can be used when compensating for motion of overlapping blocks in the right border area of the block.

As another example, if the merge candidate list or the motion vector candidate list includes motion information derived from the lower left block based on the current block, the corresponding motion information can be used when compensating for motion of overlapping blocks in the lower border area of the block. .

FIG. 16 is a diagram illustrating an example in which overlapped block motion compensation is performed on a sub-block group basis. To reduce computational complexity, sub-block-based nested block motion compensation can be performed in units of one or more blocks that combine multiple sub-blocks. At this time, a block unit combining multiple sub-blocks may mean a sub-block group unit.

Referring to FIG. 16, each distinct area in the hatched area may mean a sub-block group. Additionally, the arrow may mean that motion information of adjacent surrounding sub-blocks is used for motion compensation of the current sub-block group. Here, the position corresponding to the arrow tail may mean 1) a neighboring sub-block adjacent to the current block, 2) a neighboring sub-block group adjacent to the current block, or 3) a neighboring sub-block adjacent to the current sub-block within the current block. Additionally, the position corresponding to the head of the arrow may mean the current sub-block group within the current block.

In the sub-block group, a weighted sum of the first prediction block and the second prediction block may be calculated. The motion information used when generating the first prediction block may be motion information about the current sub-block group within the current block. Here, the motion information for the current sub-block group within the current block may be any one of the average value, median value, minimum value, maximum value, or weighted sum of the motion information for the sub-blocks included in the sub-block group. And, the motion information used when generating the second prediction block is the motion information of the neighboring sub-block adjacent to the current block, the motion information of the neighboring sub-block group adjacent to the current block, and the neighboring sub-block adjacent to the current sub-block within the current block. At least one of the motion information may be used. Here, the motion information of the neighboring sub-block group adjacent to the current block may be any one of the average value, median value, minimum value, maximum value, or weighted sum of the motion information for the sub-blocks included in the neighboring sub-block group.

Here, at least one sub-block group unit may exist in the current block, and the horizontal size of the sub-block group unit may be the same as or smaller than the horizontal size of the current sub-block. Additionally, the vertical size of the sub-block group unit may be the same as or smaller than the vertical size of the current sub-block. Additionally, overlapping block motion compensation may be performed on at least one of the sub-blocks located at the upper boundary of the current block and the sub-blocks located at the left boundary of the current block.

Meanwhile, blocks adjacent to the bottom border and right border of the current block have not been encoded/decoded, so blocks overlapped with at least one of the sub-blocks located at the bottom border within the current block and the sub-blocks located at the right border within the current block. Motion compensation may not be performed. Alternatively, since the blocks adjacent to the lower boundary and right boundary of the current block have not been encoded/decoded, the current subblock Overlapping block motion compensation can be performed using motion information of at least one of the top block, left block, top left block, bottom left block, and top right block.

Additionally, if the current block is in merge mode and is at least one of the improved temporal motion vector prediction candidate and the spatial-temporal motion vector prediction candidate, the sub-blocks located at the lower border within the current block and the sub-blocks located at the right border within the current block Motion compensation for blocks overlapped with at least one of the blocks may not be performed.

In addition, when the current block is in the decoder motion vector derivation mode or the affine motion compensation mode, block movement overlapped with at least one of the sub-blocks located at the lower boundary within the current block and the sub-blocks located at the right boundary within the current block. Compensation may not be performed.

Meanwhile, overlapping block motion compensation may be performed on at least one of each color component of the current block. At this time, the color component may include at least one of a luminance component and a color difference component.

Additionally, overlapping block motion compensation may be performed according to the inter-screen prediction indicator of the current block. That is, it can be performed when the current block has at least one of unidirectional prediction, bidirectional prediction, 3-way prediction, and 4-way prediction. Additionally, it can be performed only when the current block is unidirectional prediction. Additionally, it can be performed only when the current block is bidirectional prediction.

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

There may be up to K pieces of motion information used to generate the second prediction block. That is, up to K second prediction blocks can be generated and used for overlapping block motion compensation. Here, K may be a positive integer including 0, for example, 1, 2, 3, or 4.

For example, when generating second prediction blocks using motion information of neighboring sub-blocks adjacent to the current block, up to two pieces of motion information can be derived using at least one of the top block and the left block. In addition, when generating second prediction blocks using the motion information of surrounding sub-blocks adjacent to the current sub-block within the current block, the top block, left block, bottom block, right block, top-left block, top-right block, bottom-left block Up to four pieces of motion information can be derived using at least one of the blocks in the lower right corner. At this time, deriving motion information may mean generating a second prediction block using the derived motion information and then using it for overlapping block motion compensation.

Referring to FIG. 17, in order to improve coding efficiency, motion information used to generate a second prediction block when it corresponds to at least one of the sub-blocks located at the upper border of the current block and the sub-blocks located at the left border of the current block. Up to three can be derived. That is, motion information used to generate the second prediction block can be derived using 3-connectivity.

As an example, blocks corresponding to the upper border area within the current block may derive motion information from at least one of the neighboring upper block, upper left block, and upper right block, which are neighboring sub-blocks adjacent to the current block.

Additionally, blocks corresponding to the left border area within the current block can derive motion information from at least one of the surrounding sub-blocks adjacent to the current block: the surrounding left block, the surrounding upper left block, and the surrounding lower left block.

Additionally, blocks corresponding to the upper left border area within the current block can derive motion information from at least one of the neighboring upper block, neighboring left block, and neighboring upper left block, which are neighboring sub-blocks adjacent to the current block.

In addition, blocks corresponding to the upper-right border area within the current block can derive motion information from at least one of the neighboring upper blocks, neighboring upper-left blocks, and neighboring upper-right blocks, which are neighboring sub-blocks adjacent to the current block.

Additionally, blocks corresponding to the lower-left border area within the current block can derive motion information from at least one of the surrounding sub-blocks adjacent to the current block: the surrounding left block, the surrounding upper-left block, and the surrounding lower-left block.

Meanwhile, in order to improve coding efficiency, if it does not correspond to at least one of the sub-blocks located at the upper boundary of the current block and the sub-blocks located at the left boundary of the current block, the motion information used to generate the second prediction block is increased to the maximum. Up to 8 can be derived. That is, motion information used to generate the second prediction block can be derived using 8-connectivity.

For example, the current sub-blocks within the current block are the surrounding sub-blocks adjacent to the current sub-block within the current block: the surrounding top block, surrounding left block, surrounding bottom block, surrounding right block, surrounding top left block, surrounding bottom left block, surrounding Movement information can be derived from at least one of the lower right block and the surrounding upper right block.

Meanwhile, motion information used to generate the second prediction block can be derived from the corresponding location sub-block within the corresponding location image. Additionally, motion information used to generate the second prediction block can be derived from encoded/decoded blocks adjacent to the lower border area and the right border area of the reference block in the reference image.

Additionally, to improve coding efficiency, the number of motion information used to generate the second prediction block can be determined depending on the size or direction of the motion vector.

For example, if the sum of the absolute values of the x and y components of the motion vector is equal to or greater than J, a maximum of L can be used as the number of motion information. Conversely, if the sum of the absolute values of the x and y components of the motion vector is less than J, a maximum of P can be used as the number of motion information. At this time, J, L, and P may be positive integers including 0. It is preferable that L and P are different values, but may have the same value.

Additionally, if the current block is in merge mode and is at least one of an improved temporal motion vector prediction candidate and a spatial-temporal motion vector prediction candidate, the number of motion information used to generate the second prediction block may be up to K pieces. Here, K may be a positive integer including 0, for example, 4.

Additionally, when the current block is in the decoder motion vector derivation mode, there may be up to K pieces of motion information used to generate the second prediction block. Here, K may be a positive integer including 0, for example, 4.

Additionally, when the current block is in the affine motion compensation mode, there may be up to K pieces of motion information used to generate the second prediction block. Here, K may be a positive integer including 0, for example, 4.

Figures 18 and 19 are diagrams for explaining the derivation order of motion information used to generate the second prediction block. Motion information used to generate the second prediction block may be derived from the encoder and decoder in a predetermined order.

Referring to FIG. 18, motion information can be derived in the order of the top block, left block, bottom block, and right block based on the position of the current lower block.

Referring to FIG. 19, in order to improve coding efficiency, the motion information derivation order used to generate the second prediction block may be determined based on the location of the current lower block.

As an example, blocks corresponding to the upper border area within the current block may derive motion information in the following order: 1) surrounding upper block, 2) neighboring upper left block, and 3) neighboring upper right block, which are neighboring sub-blocks adjacent to the current block.

Additionally, blocks corresponding to the left border area within the current block can derive motion information in the following order: 1) surrounding left block, 2) surrounding upper left block, and 3) surrounding lower left block that are adjacent to the current block.

Additionally, blocks corresponding to the upper left border area within the current block can derive motion information in the following order: 1) neighboring upper block, 2) neighboring left block, and 3) neighboring upper left block, which are neighboring sub-blocks adjacent to the current block.

In addition, blocks corresponding to the upper-right border area within the current block can derive motion information in the order of the surrounding sub-blocks adjacent to the current block: 1) neighboring upper-left block, 2) neighboring upper-left block, and 3) neighboring upper-right block.

In addition, the blocks corresponding to the lower-right border area within the current block can derive movement information in the order of the surrounding sub-blocks adjacent to the current block: 1) surrounding left block, 2) surrounding upper-left block, and 3) surrounding lower-left block. .

As in the example of Figure 19, the current sub-blocks within the current block are the surrounding sub-blocks adjacent to the current sub-block within the current block: 1) surrounding top block, 2) surrounding left block, 3) surrounding bottom block, and 4) surrounding right block. , Movement information can be derived in the order of 5) surrounding upper left block, 6) surrounding lower left block, 7) surrounding lower right block, and 8) surrounding upper right block. Meanwhile, motion information may be derived in an order different from that shown in FIG. 19.

Meanwhile, the motion information of the corresponding location sub-block within the corresponding location image may be derived to a lower rank than the surrounding sub-blocks spatially adjacent to the current sub-block. Additionally, the motion information of the corresponding location sub-block within the corresponding location image may be derived to a higher rank than the surrounding sub-blocks spatially adjacent to the current sub-block.

Additionally, the motion information of blocks encoded/decoded adjacent to the lower border area and the right border area of the reference block in the reference image may be derived to a lower rank than the surrounding sub-blocks spatially adjacent to the current sub-block. Additionally, the motion information of blocks encoded/decoded adjacent to the lower border area and the right border area of the reference block in the reference image may be derived to a higher rank than the surrounding sub-blocks spatially adjacent to the current sub-block.

Motion information of neighboring sub-blocks adjacent to the current block or neighboring sub-blocks adjacent to the current sub-block within the current block can be derived as motion information used to generate the second prediction block only when a specific condition is satisfied.

For example, if there is at least one of the neighboring sub-blocks adjacent to the current block and the neighboring sub-blocks adjacent to the current sub-block within the current block, the motion information of the existing neighboring sub-blocks is used to generate the second prediction block. It can be derived by:

As another example, if at least one of the neighboring sub-blocks adjacent to the current block and the neighboring sub-blocks adjacent to the current sub-block within the current block are in the inter-screen prediction mode, motion information of at least one neighboring sub-block in the inter-screen prediction mode is provided. It can be derived from motion information used to generate the second prediction block. On the other hand, if at least one of the neighboring sub-blocks adjacent to the current block and the neighboring sub-blocks adjacent to the current sub-block within the current block are in the intra-screen prediction mode, there is no motion information in the corresponding block, so at least one of the neighboring sub-blocks adjacent to the current sub-block within the current block is in the intra-screen prediction mode. The motion information of one neighboring sub-block may not be derived as motion information used to generate the second prediction block.

Meanwhile, at least one inter-screen prediction indicator among the neighboring sub-blocks adjacent to the current block and the neighboring sub-blocks adjacent to the current sub-block within the current block is L0 prediction, L1 prediction, L2 prediction, L3 prediction, one-way prediction, two-way prediction, 3 If at least one of four-way prediction and four-way prediction is not indicated, motion information used to generate the second prediction block may not be derived.

Meanwhile, if the inter-prediction indicator used to generate the second prediction block is not the same as the inter-prediction indicator used to generate the first prediction block, motion information used to generate the second prediction block may be derived.

Additionally, if the motion vector used to generate the second prediction block is not the same as the motion vector used to generate the first prediction block, motion information used to generate the second prediction block may be derived.

Additionally, if the reference image index used to generate the second prediction block is not the same as the reference image index used to generate the first prediction block, motion information used to generate the second prediction block may be derived.

Additionally, if at least one of the motion vector and reference image index used to generate the second prediction block is not the same as at least one of the motion vector and reference image index used to generate the first prediction block, it is used to generate the second prediction block. Motion information can be derived.

Additionally, to reduce complexity, when the inter-prediction indicator used to generate the first prediction block indicates unidirectional prediction, at least one of the motion vector and reference image index for the L0 and L1 prediction directions used to generate the second prediction block If one is not the same as at least one of the motion vector and the reference image index used to generate the first prediction block, motion information used to generate the second prediction block may be derived.

Additionally, in order to reduce complexity, based on the inter-prediction indicator used to generate the first prediction block, when the inter-prediction indicator indicates bi-directional prediction, the L0 and L1 prediction directions used to generate the second prediction block are If at least one of the combination of the motion vector and the reference image index is not the same as at least one of the combination of the motion vector and the reference image index for the L0 and L1 prediction directions used to generate the first prediction block, The movement information used can be derived.

Additionally, in order to reduce complexity, if at least one piece of motion information used to generate the second prediction block is not the same as at least one piece of motion information used to generate the first prediction block, Movement information can be derived.

FIG. 20 is a diagram illustrating an example of determining whether motion information is usable for generating a second prediction block by comparing the POC of the reference image of the current sub-block and the POC of the reference image of the surrounding sub-block.

Referring to FIG. 20, in order to reduce complexity, if the POC of the reference image of the current sub-block and the POC of the reference image of the surrounding sub-block are the same, the motion information of the current sub-block will be used to generate the second prediction block of the current sub-block. You can.

Meanwhile, to reduce complexity, as in the example of FIG. 20, when the POC of the reference image used to generate the second prediction block is not the same as the POC of the reference image used to generate the first prediction block, the second prediction block is generated. Movement information used for can be derived.

Specifically, if the POC of the reference image used to generate the second prediction block is not the same as the POC of the reference image used to generate the first prediction block, the motion vector used to generate the second prediction block is used to generate the first prediction block. The motion vector can be scaled based on the reference video used for or the POC of the reference video to derive the motion vector used for generating the second prediction block.

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

When calculating the weighted sum of the first prediction block and the second prediction block, different weights may be used for each row or column depending on the sample location within the block. And, a weighted sum between samples corresponding to the same position within the first prediction block and the second prediction block may be calculated. At this time, when calculating the weighted sum for generating the final prediction block, at least one of the weight and the offset can be used.

Here, the weight can be a negative number less than 0 and a positive number greater than 0. And, the offset can be 0, a negative number less than 0, and a positive number greater than 0.

Meanwhile, when calculating the weighted sum of the first prediction block and the second prediction block, the same weight may be used at all sample positions for each prediction block.

Referring to FIG. 21, weights such as {3/4, 7/8, 15/16, 31/32} can be used for each row or each column in the first prediction block, and weights such as {3/4, 7/8, 15/16, 31/32} can be used for each row in the second prediction block. Alternatively, weights such as {1/4, 1/8, 1/16, 1/32} can be used for each column. At this time, the same weight may be used at sample positions belonging to the same row or sample positions belonging to the same column.

For each weight, the closer it is to the boundary of the current subblock, the larger the weight can be used. Additionally, each weight can be applied to all samples within a subblock.

21 (a), (b), (c), and (d) are generated using the motion information of the surrounding upper block, the motion information of the surrounding lower block, the motion information of the surrounding left block, and the motion information of the surrounding right block. 2 Examples of generating prediction blocks can be shown. Here, the top second prediction block, the bottom second prediction block, the left second prediction block, and the right second prediction block are motion information of the surrounding top block, motion information of the surrounding bottom block, motion information of the surrounding left block, and surrounding right block. It may refer to a second prediction block generated based on the motion information of .

FIG. 22 is a diagram illustrating an embodiment in which different weights are applied depending on sample positions within the block when calculating the weighted sum of the first prediction block and the second prediction block. To improve coding efficiency, when calculating the weighted sum of the first prediction block and the second prediction block, different weights may be used depending on the sample position within the block. That is, the weighted sum can be calculated with different weights depending on the positions of blocks spatially adjacent to the current lower block. Additionally, a weighted sum between samples corresponding to the same position within the first prediction block and the second prediction block may be calculated.

Referring to FIG. 22, the first prediction block includes {1/2, 3/4, 7/8, 15/16, 31/32, 63/64, 127/128, 255/256, 511/ for each sample position. Weights such as 512, 1023/1024} may be used, and in the second prediction block, {1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/ Weights such as 128, 1/256, 1/512, 1/1024} may be used. Here, the weight value used in at least one of the top second prediction block, the left second prediction block, the bottom second prediction block, and the right second prediction block is the top left second prediction block, the bottom left second prediction block, and the bottom right. It may be greater than the weight value used in at least one of the second prediction block and the upper right second prediction block.

Meanwhile, the weight value 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 is the upper left second prediction block, the lower left second prediction block, and the lower right. It may be the same as the weight value used in at least one of the second prediction block and the upper right second prediction block.

Additionally, the weight for the second prediction block generated using the motion information of the corresponding location sub-block in the corresponding location image may be the same at all sample locations.

Additionally, the weight of the second prediction block generated using the motion information of the corresponding location sub-block in the corresponding location image may be the same as the weight of the first prediction block.

Additionally, the weight for the second prediction block generated using the motion information of the encoded/decoded block adjacent to the lower border area and the right border area of the reference block in the reference image may be the same at all sample positions.

Additionally, the weight of the second prediction block generated using the motion information of the encoded/decoded block adjacent to the lower border area and the right border area of the reference block in the reference image may be the same as the weight of the first prediction block.

Meanwhile, in order to reduce computational complexity, the weight value may vary depending on the size of the motion vector of a neighboring sub-block adjacent to the current block or a neighboring sub-block adjacent to the current sub-block within the current block.

For example, if the sum of the absolute values of the motion vector x component and y component of the surrounding sub-block is equal to or greater than a predefined value, the weight of the current sub-block is 15/16} can be used. On the other hand, if the sum of the absolute values of the motion vector can be used. At this time, the predefined value may be a positive integer including 0.

Additionally, in order to reduce computational complexity, the weight value may vary depending on the motion vector size or motion vector direction of the current lower block.

For example, if the absolute value of the motion vector 16} can be used. On the other hand, if the absolute value of the motion vector You can. At this time, the predefined value may be a positive integer including 0.

For example, if the absolute value of the motion vector y component of the current sub-block is equal to or greater than a predefined value, the weights of the upper and lower surrounding sub-blocks are {1/2, 3/4, 7/8, 15/ 16} can be used. On the other hand, if the absolute value of the motion vector y component of the current sub-block is smaller than the predefined value, {7/8, 15/16, 31/32, 63/64} is used as the weight of the upper and lower surrounding sub-blocks. You can. At this time, the predefined value may be a positive integer including 0.

For example, if the sum of the absolute values of the x and y components of the motion vector of the current sub-block is equal to or greater than a predefined value, the weight of the current sub-block is {1/2, 3/4, 7/8. , 15/16} can be used. On the other hand, if the sum of the absolute values of the x and y components of the motion vector of the current sub-block is less than the predefined value, the weight of the current sub-block is {7/8, 15/16, 31/32, 63/64. } can be used. At this time, the predefined value may be a positive integer including 0.

Meanwhile, the weighted sum calculation may not be performed on all sample positions within the sub-block, but on samples located in K rows/columns adjacent to each block boundary. At this time, K may be a positive integer including 0, for example, 1 or 2.

Additionally, if the size of the current block is less than NxM, a weighted sum can be calculated for samples located in K rows/columns adjacent to each block boundary. Additionally, when the current block is divided into sub-blocks and motion compensation is performed, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. Here, K may be a positive integer including 0, for example, 1 or 2. Additionally, N and M may be positive integers, for example, N and M may be 4 or 8 or more. N and M may be the same or different from each other.

Additionally, based on the color component of the current block, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. At this time, K may be a positive integer including 0, for example, 1 or 2. Additionally, when the current block is a luminance component, a weighted sum may be calculated for samples located in two rows/columns adjacent to each block boundary. Additionally, when the current block is a chrominance component, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary.

Additionally, if the current block is in merge mode and is at least one of an improved temporal motion vector prediction candidate and a spatial-temporal motion vector prediction candidate, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. .

Additionally, when the current block is in the decoder motion vector derivation mode, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. Additionally, when the current block is in an affine motion compensation mode, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. At this time, K may be a positive integer including 0, for example, 1 or 2.

Meanwhile, to reduce computational complexity, a weighted sum can be calculated for samples located in K rows/columns adjacent to each block boundary according to the size of the subblock of the current block.

For example, if the size of the subblock of the current block is 4x4, a weighted sum may be calculated for samples located in 1, 2, 3, or 4 rows/columns adjacent to each block boundary. In addition, if the size of the subblock of the current block is 8x8, samples located in 1, 2, 3, 4, 5, 6, 7, or 8 rows/columns adjacent to each block boundary A weighted sum can be calculated. At this time, K is a positive integer including 0, and its maximum value can be as many as the number of rows/columns of the lower block.

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

Additionally, in order to reduce computational complexity, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary according to the number of motion information used to generate the second prediction block. Here, K may be a positive integer including 0.

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

Additionally, if the number of motion information is equal to or greater than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary.

Additionally, in order to reduce computational complexity, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary according to the inter-screen prediction indicator of the current block. K may be a positive integer including 0.

For example, if the inter-screen prediction indicator is unidirectional prediction, a weighted sum may be calculated for samples located in two rows/columns adjacent to each block boundary. Additionally, when the inter-screen prediction indicator is bi-directional prediction, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary.

Additionally, to reduce computational complexity, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary according to the POC of the reference image of the current block. Here, K may be a positive integer including 0.

For example, if the difference between the POC of the current image and the POC of the reference image is smaller than a predefined value, a weighted sum may be calculated for samples located in two rows/columns adjacent to each block boundary. On the other hand, if the difference between the POC of the current image and the POC of the reference image is equal to or greater than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary.

In addition, in order to reduce computational complexity, a weighted sum is applied to samples located in K rows/columns adjacent to each block boundary according to the size of the motion vector of the neighboring sub-block adjacent to the current block or the neighboring sub-block adjacent to the current sub-block within the current block. This can be calculated. Here, K may be a positive integer including 0.

For example, if the sum of the absolute values of the motion vector You can. On the other hand, if the sum of the absolute values of the x-component and y-component of the motion vector of the surrounding sub-block is smaller than a predefined value, the weighted sum may be calculated for samples located in one row/column adjacent to the boundary of each block. At this time, the predefined value may be a positive integer including 0.

Additionally, to reduce computational complexity, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary according to the motion vector size or motion vector direction of the current lower block. Here, K may be a positive integer including 0.

For example, if the absolute value of the motion vector x component of the current lower block is equal to or greater than a predefined value, a weighted sum may be calculated for samples located in two rows/columns adjacent to the left and right boundaries. On the other hand, if the absolute value of the motion vector x component of the current lower block is smaller than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to the left and right boundaries. At this time, the predefined value may be a positive integer including 0.

For example, if the absolute value of the motion vector y component of the current lower block is equal to or greater than a predefined value, a weighted sum may be calculated for samples located in two rows/columns adjacent to the upper and lower boundaries. On the other hand, if the absolute value of the motion vector y component of the current lower block is smaller than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to the upper and lower boundaries. At this time, the predefined value may be a positive integer including 0.

For example, if the sum of the absolute values of the x and y components of the motion vector is equal to or greater than a predefined value, a weighted sum may be calculated for samples located in two rows/columns adjacent to each block boundary. On the other hand, if the sum of the absolute values of the x and y components of the motion vector is smaller than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary. At this time, the predefined value may be a positive integer including 0.

FIG. 23 is a diagram illustrating an embodiment in which the weighted sum of a first prediction block and a second prediction block is cumulatively calculated in a predetermined order when compensating for overlapped block motion. The weighted sum of the first prediction block and the second prediction block may be calculated in a predetermined order in the encoder and decoder.

Referring to FIG. 23, motion information can be derived in the order of the top block, left block, bottom block, and right block adjacent to the current lower block, and a second prediction block is generated using the derived motion information, making the first prediction A weighted sum of the block and the second prediction block may be calculated. When calculating the weighted sum in the predetermined order, the weighted sum may be accumulated in the above order to generate the final prediction block.

As in the example of FIG. 23, the weighted sum of the first prediction block and 1) the second prediction block generated using the motion information of the top block may be calculated to generate a first weighted sum result block, and the generated first The weighted sum of 1) the weighted sum result block and 2) the second prediction block generated using the motion information of the left block may be calculated to generate a second weighted sum result block, and the generated second weighted sum result block and 3) ) The weighted sum of the second prediction block generated using the motion information of the bottom block is calculated to generate a third weighted sum result block, and the generated third weighted sum result block and 4) the motion information of the right block are A weighted sum of the second prediction blocks generated using the second prediction block may be calculated to generate the final prediction block.

Meanwhile, the motion information derivation order used to generate the second prediction block and the weighted sum calculation order of the second prediction block when 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 in which a weighted sum of a first prediction block and a second prediction block is calculated when compensating for overlapped block motion. In order to improve coding efficiency, when calculating the weighted sum, the weighted sum is not accumulated, but the weight of the second prediction blocks generated using at least one of the motion information of the first prediction block, top block, left block, bottom block, and right block. The sum can be calculated in any order.

At this time, the second prediction blocks generated using at least one of the motion information of the top block, left block, bottom block, and right block may have the same weight. Additionally, the weight used in the second prediction block and the weight used in the first prediction block may be the same.

Referring to FIG. 24, storage space equal to the number of first and second prediction blocks is allocated, and when generating the final prediction block, the weighted sum of the first prediction block and the second prediction block can be calculated with equal weights between the second prediction blocks. .

*In addition, the weighted sum of the second prediction block generated using the motion information of the corresponding location sub-block in the corresponding location image may be calculated with the first prediction block.

If the size of the current block is less than or equal to K samples, entropy encoding/decoding may be performed on information on whether overlapped block motion compensation is performed for the current block. At this time, K may be a positive integer, for example, 256.

In addition, if the size of the current block is larger than K samples or in a specific inter-screen prediction mode (e.g., merge mode or enhanced motion vector prediction mode), entropy-encodes information on whether overlapped block motion compensation is performed for the current block. /You can basically perform overlapped block motion compensation without decoding.

In the motion prediction step, the encoder may perform motion prediction after subtracting the second prediction block from the original signal in the area corresponding to the boundary of the current block. At this time, when subtracting the second prediction block, a weighted sum can be calculated between the second prediction block and the original signal.

For the current block where overlapped block motion compensation is not used, the Enhanced Multiple Transform, which applies DCT (Discrete Cosine Transform)-based transforms and DST (Discrete Sine Transform)-based transforms to vertical/horizontal transformation, is not applied. It may not be possible. That is, improved multiple transformation can be applied only to the current block for which overlapped block motion compensation is used.

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

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

Then, a second prediction block of at least one current sub-block may be generated using motion information of at least one neighboring sub-block of the current sub-block (S2520). Here, the neighboring sub-block may include neighboring sub-blocks of the sub-blocks of the corresponding location block temporally corresponding to the current block.

Meanwhile, when the current sub-block is not included in the left border area and the top border area of the current block, at least one second prediction is performed using motion information of at least one neighboring sub-block of the sub-block of the corresponding location block. Blocks can be created.

In addition, if the current sub-block is not included in the left border area and the top border area of the current block, a second prediction block is created using motion information included in at least one of the merge list and the motion vector list of the current block. can be created.

Meanwhile, only when the current sub-block is included in at least one of the left border area and the top border area of the current block, at least one second prediction block can be generated using the motion information of at least one surrounding sub-block. there is.

Meanwhile, when the current sub-block is included in the left border area of the current sub-block, at least one is generated using motion information of at least one of the left neighboring sub-block, the upper-left neighboring sub-block, and the lower-left neighboring sub-block of the current sub-block. generates a second prediction block, and when the current sub-block is included in the upper boundary area of the current block, at least one of the upper neighboring sub-block, the upper-left neighboring sub-block, and the lower-right neighboring sub-block of the current sub-block At least one second prediction block can be generated using motion information.

Meanwhile, if the current sub-block is not included in the left border area and the top border area of the current sub-block, the top surrounding sub-block, left surrounding sub-block, bottom surrounding sub-block, right surrounding sub-block, and top left of the current sub-block At least one second prediction block may be generated using motion information of at least one of the neighboring sub-block, the lower-left neighboring sub-block, the lower-right neighboring sub-block, and the upper-right neighboring sub-block.

Meanwhile, motion information of at least one neighboring sub-block of the current sub-block may be derived based on a predetermined order, and at least one second prediction block may be generated using the derived at least one motion information.

Then, a final prediction block may be generated based on the weighted sum of the first prediction block of the current block and the second prediction block of the at least one current sub-block (S2530).

In this case, weighted sum may be performed by applying different weights for each sample of the first prediction block and the second prediction block depending on the positions of neighboring sub-blocks used when generating the second prediction block.

Meanwhile, in the step of generating the final prediction block (S2530), when the number of second prediction blocks of the current sub-block is plural, the weighted sum between the first prediction block of the current block and the second prediction block of the current sub-block is calculated. By simultaneously summing, the final prediction block can be generated.

Each step of the video decoding method of FIG. 25 can be equally applied to the video encoding method according to the present invention.

Meanwhile, the bitstream generated by the video encoding method according to the present invention can be stored in a recording medium.

The above embodiments can be performed in the same way in the encoder and decoder.

The order of applying the above embodiments may be different in the encoder and decoder, and the order of applying the above embodiments may be the same in the encoder and decoder.

The above embodiment can be performed for each of the luminance and chrominance signals, and the above embodiment can be equally performed for the luminance and chrominance signals.

The shape of the block 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. The size here may be defined as the minimum size and/or maximum size to which the above embodiments are applied, or may be defined as a fixed size to which the above embodiments are applied. Additionally, 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, constant embodiments can be applied in complex ways depending on the size. Additionally, the above embodiments of the present invention may be applied only when the size is above the minimum size and below the maximum size. That is, the above embodiments may be applied only when the block size is within a certain range.

For example, the above embodiments can be applied only when the size of the current block is 8x8 or larger. For example, the above embodiments can be applied only when the size of the current block is 4x4. For example, the above embodiments can be applied only when the size of the current block is 16x16 or less. For example, the above embodiments can be applied only when the current block size is 16x16 or more and 64x64 or less.

The above embodiments of the present invention can be applied according to the temporal layer. A separate identifier is signaled to identify the temporal layer to which the embodiments can be applied, and the embodiments can be applied to the temporal layer specified by the identifier. The identifier here may be defined as the lowest layer and/or highest layer to which the embodiment is applicable, or may be defined as indicating a specific layer to which the embodiment is applicable. Additionally, a fixed temporal hierarchy to which the above embodiment is applied may be defined.

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

The slice type to which the embodiments of the present invention are applied is defined, and the embodiments of the present invention can be applied depending on the slice type.

In the above-described embodiments, the methods are described based on flowcharts as a series of steps or units, but the present invention is not limited to the order of steps, and some steps may occur in a different order or simultaneously with other steps as described above. You can. Additionally, a person of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive and that other steps may be included or one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You will understand.

The above-described embodiments include examples of various aspects. Although it is not possible to describe all possible combinations for representing the various aspects, those skilled in the art will recognize that other combinations are possible. Accordingly, the present invention is intended to include all other substitutions, modifications and changes falling within the scope of the following claims.

Embodiments according to the present invention described above may be implemented in the form of program instructions that can be executed through 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., singly or in combination. Program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and usable by those skilled in the computer software field. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, and magneto-optical media such as floptical disks. media), and hardware devices specifically configured to store and perform program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include not only machine language code such as that created by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform processing according to the invention and vice versa.

In the above, the present invention has been described with specific details such as specific components and limited embodiments and drawings, but this is only provided to facilitate a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , a person skilled in the art to which the present invention pertains can make various modifications and variations from this description.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and the scope of the patent claims described below as well as all modifications equivalent to or equivalent to the scope of the claims fall within the scope of the spirit of the present invention. They will say they do it.

Claims (19)

Obtaining prediction mode information indicating the prediction mode of the current block;
generating a first prediction block and a second prediction block for the current block according to the prediction mode; and
Generating a final prediction block for the current block using the first prediction block and the second prediction block,
The first prediction block is generated by performing a first prediction on the current block,
The second prediction block is generated by performing second prediction on the current block. According to paragraph 1,
An image decoding method in which the first prediction block and the second prediction block are generated using one or more merge candidates existing in one merge candidate list for the current block. According to paragraph 2,
Further comprising obtaining a first merge index and a second merge index for the merge candidate list,
The first prediction block is generated using a merge candidate indicated by the first merge index among candidates in the merge candidate list,
The second prediction block is generated using a merge candidate indicated by the second merge index among candidates in the merge candidate list. According to paragraph 1,
An image decoding method in which the final prediction block for the current block is generated using a weighted sum of samples of the first prediction block and samples of the second prediction block. According to paragraph 4,
A video decoding method in which weight information about the weights for the weighted sum is received through a bitstream. According to clause 4,
A video decoding method in which the weight is decoded based on the encoding parameters for the current block. generating a first prediction block and a second prediction block for the current block; and
Generating a final prediction block for the current block using the first prediction block and the second prediction block,
The first prediction block is generated by performing a first prediction on the current block,
The second prediction block is generated by performing a second prediction on the current block,
An image encoding method for generating prediction mode information indicating the prediction mode of the current block. In clause 7,
The information for generating the first prediction block and the information for generating the second prediction block correspond to one or more merge candidates existing in one merge candidate list for the current block. According to clause 8,
Further comprising generating a first merge index and a second merge index for the merge candidate list,
The information for generating the first prediction block corresponds to a merge candidate indicated by the first merge index among the candidates in the merge candidate list,
The image encoding method wherein the information for generating the second prediction block corresponds to a merge candidate indicated by the second merge index among candidates in the merge candidate list. In clause 7,
An image encoding method in which the final prediction block for the current block is generated using a weighted sum of samples of the first prediction block and samples of the second prediction block. In clause 7,
A video encoding method in which a bitstream containing weight information about weights for the weighted sum is generated. According to clause 10,
An image encoding method in which the weight is decoded based on the encoding parameter for the current block. A computer-readable recording medium storing a bitstream generated by the video encoding method of claim 7. In a computer-readable recording medium containing a bitstream,
The bitstream is,
Prediction mode information indicating the prediction mode of the current block
Including,
A first prediction block and a second prediction block for the current block are generated using the prediction mode information,
A final prediction block for the current block is generated using the first prediction block and the second prediction block,
The first prediction block is generated by performing a first prediction on the current block,
The second prediction block is generated by performing second prediction on the current block. According to clause 14,
The first prediction block and the second prediction block are generated using one or more merge candidates existing in one merge candidate list for the current block. According to clause 15,
A first merge index and a second merge index for the merge candidate list are obtained,
The first prediction block is generated using a merge candidate indicated by the first merge index among candidates in the merge candidate list,
The second prediction block is a computer-readable recording medium generated using a merge candidate indicated by the second merge index among candidates in the merge candidate list. According to clause 14,
A computer-readable recording medium in which the final prediction block for the current block is generated using a weighted sum of samples of the first prediction block and samples of the second prediction block. According to clause 17,
A computer-readable recording medium in which weight information about weights for the weighted sum is received through a bitstream. According to clause 17,
A computer-readable recording medium in which the weight is decoded based on an encoding parameter for the current block.