KR20210082421A - Method and apparatus for encoding/decoding image and recording medium for storing bitstream - Google Patents

Abstract

The present invention relates to an image encoding and decoding method. An image decoding method for this purpose may include the steps of: generating the first prediction block of a current block using motion information of the current block; generating the second prediction block of at least one current sub-block by using motion information of at least one neighboring sub-block of the current sub-block; and generating a final prediction block 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. An object of the present invention is to provide a method and apparatus for performing overlapping block motion compensation by increasing the number of motion information of neighboring blocks in order to improve image encoding/decoding efficiency.

Description

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

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

Recently, demand for high-resolution and high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images is increasing in various application fields. As the image data becomes higher resolution and higher quality, the amount of data increases relative to the existing image data. Therefore, when transmitting image data using a medium such as an existing wired or wireless broadband line or storing it using an existing storage medium, the transmission cost and storage costs will increase. In order to solve these problems that occur as image data becomes high-resolution and high-quality, high-efficiency image encoding/decoding technology for images having higher resolution and image quality is required.

Inter-screen prediction technology that predicts pixel values included in the current picture from pictures before or after the current picture with image compression technology, intra-picture prediction technology that predicts pixel values included in the current picture using pixel information in the current picture, Various techniques exist, such as transformation and quantization techniques for compressing the energy of the residual signal, and entropy coding techniques that assign short codes to high frequency values and long codes to low frequency values. Image data can be effectively compressed and transmitted or stored.

Conventional image encoding/decoding methods and apparatuses have limitations in improving encoding efficiency because only limited motion information of neighboring blocks is used for overlapping block motion compensation.

The present invention may provide a method and apparatus for performing overlapping block motion compensation by increasing the number of motion information of neighboring blocks in order to improve image encoding/decoding efficiency.

According to an aspect of 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 a first prediction block of the current block and the at least one current sub-block generating a final prediction block based on a weighted sum of the second prediction blocks of

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

In the image decoding method, the generating of the second prediction block includes, when the current sub-block is not included in the left boundary region and the upper boundary region of the current block, at least one of the sub-blocks of the corresponding block. At least one second prediction block may be generated using motion information of a neighboring sub-block of .

In the image decoding method, the generating of the second prediction block includes a merge list and a motion vector list of the current block when the current sub-block is not included in a left boundary region and an upper boundary region of the current block. A second prediction block may be generated by using motion information included in at least one of .

In the image decoding method, the generating of the second prediction block includes: only when the current sub-block is included in at least one of a left boundary region and an upper boundary region of the current block, at least one neighboring sub-block At least one second prediction block may be generated using the motion information.

In the image decoding method, the generating of the second prediction block includes: when the current sub-block is included in a left boundary region of the current block, a left neighboring sub-block of the current sub-block, an upper-left neighboring sub-block, and At least one second prediction block is generated by using at least one piece of motion information among the lower-left neighboring sub-blocks, and when the current sub-block is included in the upper boundary area of the current block, the upper peripheral lower-order of the current sub-block At least one second prediction block may be generated using motion information of at least one of a block, an upper-left neighboring sub-block, and a lower-right neighboring sub-block.

In the image decoding method, the generating of the second prediction block includes: when the current sub-block is not included in a left boundary region and an upper boundary region of the current block, an upper peripheral sub-block of the current sub-block; At least one second one using 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 generated.

In the image decoding method, the generating of 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 the at least one induced motion information can be used to generate at least one second prediction block.

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

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

According to an aspect of 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 a first prediction block of the current block and the at least one current sub-block generating a final prediction block based on a weighted sum of the second prediction blocks of

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 generating of the second prediction block includes at least one of the sub-blocks of the corresponding location block when the current sub-block is not included in the left boundary region and the upper boundary region of the current block. At least one second prediction block may be generated using motion information of a neighboring sub-block of .

In the image encoding method, the generating of the second prediction block includes a merge list and a motion vector list of the current block when the current sub-block is not included in a left boundary region and an upper boundary region of the current block. A second prediction block may be generated by using motion information included in at least one of .

In the video encoding method, the generating of the second prediction block includes: only when the current sub-block is included in at least one of a left boundary region and an upper boundary region of the current block, at least one neighboring sub-block At least one second prediction block may be generated using the motion information.

In the image encoding method, the generating of the second prediction block includes: when the current sub-block is included in a left boundary region of the current block, a left neighboring sub-block of the current sub-block, an upper-left neighboring sub-block, and At least one second prediction block is generated by using at least one piece of motion information among the lower-left neighboring sub-blocks, and when the current sub-block is included in the upper boundary area of the current block, the upper peripheral lower-order of the current sub-block At least one second prediction block may be generated using motion information of at least one of a block, an upper-left neighboring sub-block, and a lower-right neighboring sub-block.

In the image encoding method, the generating of the second prediction block includes: when the current sub-block is not included in a left boundary region and an upper boundary region of the current block, an upper neighboring sub-block of the current sub-block; At least one second one using 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 generated.

In the video encoding method, the generating of 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 the derived at least one motion information can be used to generate at least one second prediction block.

In the video encoding method, the generating of the final prediction block comprises: calculating weights for each sample of the first prediction block and the second prediction block according to positions of neighboring sub-blocks used to generate the second prediction block. Weighted summation can be performed differently by applying it.

In the video encoding method, the generating of the final prediction block includes: when there are a plurality of second prediction blocks of the current sub-block, between a first prediction block of the current block and a second prediction block of the current sub-block The final prediction block may be generated by simultaneously summing the weighted sum.

The recording medium of the present invention may include: 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 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 of may be stored.

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

According to the present invention, it is possible to improve the encoding and decoding efficiency of an image.

According to the present invention, it is possible to reduce the computational complexity of an encoder and a decoder of an image.

1 is a block diagram illustrating a configuration of an encoding apparatus to which the present invention is applied according to an embodiment.
2 is a block diagram illustrating a configuration of a decoding apparatus to which the present invention is applied according to an embodiment.
FIG. 3 is a diagram schematically illustrating a split structure of an image when encoding and decoding an image.
4 is a diagram for explaining an embodiment of an inter prediction process.
5 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.
6 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.
7 is a flowchart illustrating an image encoding method according to another embodiment of the present invention.
8 is a flowchart illustrating an image decoding method according to another embodiment of the present invention.
9 is a diagram for explaining an example of deriving a spatial motion vector candidate of a current block.
10 is a diagram for explaining an example of deriving a temporal motion vector candidate of a current block.
11 is a diagram for explaining an example in which a spatial merge candidate is added to a merge candidate list.
12 is a diagram for describing an example in which a temporal merge candidate is added to a merge candidate list.
13 is a view for explaining an example in which overlapping block motion compensation is performed in units of sub-blocks.
14 is a view for explaining an example in which superimposed block motion compensation is performed using motion information of a lower block of a corresponding location block.
15 is a diagram illustrating an example in which overlapped block motion compensation is performed using motion information of a block adjacent to a boundary region of a reference block.
16 is a view for explaining an example in which overlapping block motion compensation is performed in units of lower block groups.
17 is a diagram for explaining an example of the number of motion information used for overlapping block motion compensation.
18 and 19 are diagrams for explaining a derivation order of motion information used to generate a second prediction block.
20 is a diagram for explaining an example of determining whether motion information is usable for generating a second prediction block by comparing a POC of a reference picture of a current sub-block and a POC of a reference picture of a neighboring sub-block.
21 is a diagram for explaining an embodiment of applying a weight when calculating a weighted sum of a first prediction block and a second prediction block.
22 is a diagram for explaining an embodiment in which different weights are applied according to sample positions in blocks when a weighted sum of a first prediction block and a second prediction block is calculated.
23 is a diagram for explaining an embodiment in which a weighted sum of a first prediction block and a second prediction block is cumulatively calculated in a predetermined order during overlapping block motion compensation.
24 is a diagram for explaining an embodiment in which a weighted sum of a first prediction block and a second prediction block is calculated when overlapping block motion is compensated.
25 is a flowchart illustrating an image decoding method according to an embodiment of the present invention.

Since the present invention can have various changes and can have various embodiments, specific embodiments are 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 it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects. Shapes and sizes of elements in the drawings may be exaggerated for clearer description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] Reference is made 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 various embodiments are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein with respect to one embodiment may be embodied in other embodiments without departing from the spirit and scope of the invention. In addition, 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 set forth below is not intended to be taken in a limiting sense, and the scope of exemplary embodiments, if properly described, is limited only by the appended claims, along with all scope equivalents to those claimed.

In the present invention, terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed 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 should be understood that there may be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

Components shown in the embodiment of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is composed of separate hardware or a single software component. That is, each component is listed as each component for convenience of description, and at least two components of each component are 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 be divided into a plurality of components. Integrated embodiments and separate embodiments of components are also included in the scope of the present invention without departing 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. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof. That is, the description of “including” a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and it means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Some components of the present invention are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to 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 is omitted, and the same reference numerals are used for the same components in the drawings. and repeated descriptions of the same components are omitted.

In addition, hereinafter, an image may mean one picture constituting a video, or may indicate a moving picture 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 image among images constituting a video". may be 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: MxN array of Samples. Here, M and N mean positive integer values, and a block may mean a sample array in a two-dimensional form. A block may mean a unit. The current block may mean an encoding object block to be encoded during encoding and a decoding object block to be a decoding object during decoding. Also, the current block may be at least one of a coding block, a prediction block, a residual block, and a transform block.

Sample: A basic unit that composes a block. It may be expressed as a value ranging from 0 to 2 ^Bd - 1 according to the bit depth (B _{d ).} In the present invention, a sample may be used synonymously with a pixel or a pixel.

Unit: means a unit of video encoding and decoding. In encoding and decoding of an image, a unit may be a region obtained by dividing one image. Also, the unit may refer to the divided unit when encoding or decoding an image by dividing it into subdivided units. In encoding and decoding of an image, a process predefined for each unit may be performed. One unit may be further divided into sub-units having a smaller size compared to the unit. According to a function, a unit is a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding block, and a prediction. It may mean a unit (Prediction Unit), a prediction block (Prediction Block), a residual unit (Residual Unit), a residual block (Residual Block), a transform unit (Transform Unit), a transform block (Transform Block), and the like. Also, a unit may mean including a luminance (Luma) component block, a chroma component block corresponding thereto, and a syntax element for each block in order to be distinguished from the block. The unit may have various sizes and shapes, and in particular, the shape of the unit may include not only a rectangle but also a geometric figure that can be expressed in two dimensions, such as a square, a trapezoid, a triangle, and a pentagon. In addition, the unit information may include at least one of a unit type indicating a coding unit, a prediction unit, a residual unit, a transform unit, etc., a size of a unit, a depth of a unit, an encoding and decoding order of the unit, and the like.

Coding Tree Unit: Consists of two chrominance component (Cb, Cr) coding tree blocks related to one luminance component (Y) coding tree block. Also, it may mean including the blocks and a syntax element for each block. Each coding tree unit may be split using one or more splitting methods, such as a quad tree and a binary tree, to configure subunits such as a coding unit, a prediction unit, and a transform unit. Like segmentation of an input image, it may be used as a term to refer to a pixel block that becomes a processing unit in an image decoding/encoding process.

Coding tree block: may be used as a term to refer to any one of a Y coding tree block, a Cb coding tree block, and a 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. The neighboring block may mean 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 vertical neighbor block vertically adjacent to the current block. The neighboring block may mean a reconstructed neighboring block.

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

Unit Depth: The degree to which a unit is divided. In a tree structure, a root node may have the shallowest depth, and a leaf node may have the deepest depth. Also, when the unit is expressed in a tree structure, a level at which the unit is present may mean the unit depth.

Bitstream: A bit stream including encoded image information.

Parameter Set: Corresponds to header information among 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. In addition, the parameter set may include slice header and tile header information.

Parsing: It may mean determining a value of a syntax element by entropy-decoding a bitstream, or may mean entropy decoding itself.

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

Prediction Unit: A basic unit for performing prediction, such as inter prediction, intra prediction, inter picture compensation, intra picture compensation, and motion compensation. One prediction unit may be divided into a plurality of small partitions or sub-prediction units.

Prediction Unit Partition: A form in which a prediction unit is divided.

Reference picture list: Refers to a list including one or more reference pictures used for inter prediction or motion compensation. The type of the reference image list may include LC (List Combined), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3), etc. A list can be used.

Inter Prediction Indicator: It may mean an inter 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 mean the number of prediction blocks used when inter prediction or motion compensation is performed on the current block.

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

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

Motion vector: A two-dimensional vector used for inter prediction or motion compensation, and may mean an offset between an encoding/decoding target image and a 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: When a motion vector is predicted, it means a block that is a prediction candidate or a motion vector of the block. Also, the motion vector candidate may be included in the motion vector candidate list.

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

Motion Vector Candidate Index: An indicator indicating a motion vector candidate in the motion vector candidate list. It can also be referred to as an index of a motion vector predictor.

Motion information: at least among a motion vector, a reference picture index, an inter prediction indicator, as well as reference picture list information, a reference picture, a motion vector candidate, a motion vector candidate index, a merge candidate, a merge index, etc. It may mean information including one.

Merge Candidate List: 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 bi-prediction merge candidate, a zero merge candidate, and the like. The merge candidate may include motion information such as an inter prediction indicator, a reference image index for each list, and a motion vector.

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

Transform Unit: A basic unit for performing residual signal encoding/decoding such as transform, inverse transform, quantization, inverse quantization, and transform coefficient encoding/decoding. One transformation unit may be divided into a plurality of small transformation units.

Scaling: Refers to the process of multiplying the transform coefficient level by a factor. A transform coefficient may be generated as a result of scaling to the transform coefficient level. Scaling may also be referred to as dequantization.

Quantization parameter: may mean a value used when generating a transform coefficient level with respect to a transform coefficient in quantization. Alternatively, it may mean a value used when generating a transform coefficient by scaling a transform coefficient level in inverse quantization. The quantization parameter may be a value mapped to a quantization step size.

Residual quantization parameter (Delta Quantization Parameter): means a difference value between a predicted quantization parameter and a quantization parameter of a unit to be encoded/decoded.

Scan: A method of arranging the order of coefficients in a block or matrix. For example, sorting a two-dimensional array into a one-dimensional array is called a scan. Alternatively, arranging the one-dimensional array in the form of a two-dimensional array may also be referred to as scan or inverse scan.

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

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

Non-zero transform coefficient (Non-zero Transform Coefficient): It means a transform coefficient whose value is not 0 or a transform coefficient level whose value is not 0.

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

Quantization matrix coefficient: means each element in the quantization matrix. The quantization matrix coefficient may also be referred to as a matrix coefficient.

Default matrix: It means a predetermined quantization matrix predefined in the encoder and the decoder.

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

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

The encoding apparatus 100 may be an encoder, a video encoding apparatus, or an image encoding apparatus. A video may include one or more images. The encoding apparatus 100 may sequentially encode one or more images.

Referring to FIG. 1 , the encoding apparatus 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 encoder 150 , an inverse quantizer 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference picture buffer 190 .

The encoding apparatus 100 may encode an input image in an intra mode and/or an inter mode. Also, the encoding apparatus 100 may generate a bitstream by encoding an input image, and may output the generated bitstream. The generated bitstream may be stored in a computer-readable recording medium or streamed through a wired/wireless transmission medium. 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, the intra mode may mean an intra prediction mode, and the inter mode may mean an inter prediction mode. The encoding apparatus 100 may generate a prediction block for the input block of the input image. Also, after the prediction block is generated, the encoding apparatus 100 may encode a residual between the input block and the prediction block. The input image may be referred to as a current image that is a current encoding target. The input block may be referred to as a current block that is a current encoding target or an encoding object block.

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

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

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

When the motion vector value does not have an integer value, the motion predictor 111 and the motion compensator 112 may generate a prediction block by applying an interpolation filter to a partial region in the reference image. . In order to perform inter prediction or motion compensation, the motion prediction and motion compensation methods of the prediction unit included in the corresponding coding unit based on the coding unit are skip mode, merge mode, and improved motion vector prediction ( It may be determined whether the method is an Advanced Motion Vector Prediction (AMVP) mode or a current picture reference mode, and inter-screen prediction or motion compensation may be performed according to each mode.

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

The transform unit 130 may perform transform on the residual block to generate a transform coefficient, and may output a transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing transform on the residual block. When a transform skip mode is applied, the transform unit 130 may skip transform on the residual block.

A quantized level may be generated by applying quantization to the transform coefficients or the residual signal. Hereinafter, in embodiments, a 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 may output the quantized level. In this case, the quantization unit 140 may quantize the transform coefficients using a quantization matrix.

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

When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence and a large number of bits are allocated to a symbol having a low probability of occurrence to express the symbol, so that bits for symbols to be encoded The size of the column may be reduced. The entropy encoder 150 may use an encoding method such as exponential Golomb, Context-Adaptive Variable Length Coding (CAVLC), or Context-Adaptive Binary Arithmetic Coding (CABAC) 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 encoder 150 derives a binarization method of a target symbol and a probability model of a target symbol/bin, and then derives a binarization method, a probability model, and a context model. can also be used to perform arithmetic encoding.

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

Coding parameters may include information (flags, indexes, etc.) that is encoded in the encoder and signaled to the decoder, such as syntax elements, as well as information derived from encoding or decoding, and when encoding or decoding an image It can mean any information you need. For example, unit/block size, unit/block depth, unit/block partition information, unit/block partition structure, whether to split in a quadtree format, whether to split in a binary tree format, or a binary tree format partitioning direction (horizontal or vertical direction), binary tree-type division (symmetrical or asymmetrical division), intra prediction mode/direction, reference sample filtering method, prediction block filtering method, prediction block filter tab, prediction block filter coefficients, inter prediction mode, motion information, motion vector, reference picture index, inter prediction direction, inter prediction indicator, reference picture list, reference picture, motion vector prediction candidate, motion vector candidate list, whether to use merge mode, merge candidate, merge candidate list, skip (skip) mode use, interpolation filter type, interpolation filter tab, interpolation filter coefficients, motion vector size, motion vector expression accuracy, transform type, transform size, information on whether to use primary transformation, information on whether to use secondary transformation, primary Transform index, secondary transform index, residual signal presence information, coded block pattern, coded block flag, quantization parameter, quantization matrix, whether or not to apply loop filter in the picture, loop filter coefficient in the picture , in-screen loop filter tab, in-screen loop filter shape/shape, deblocking filter applied or not, deblocking filter coefficients, deblocking filter tab, deblocking filter strength, deblocking filter shape/shape, whether adaptive sample offset is applied, Adaptive sample offset value, adaptive sample offset category, adaptive sample offset type, whether adaptive in-loop filter is applied, adaptive in-loop filter coefficients, adaptive in-loop filter tab, adaptive in-loop filter shape/shape, binarization /Inverse binarization method, context model determination method, context model update method, regular mode performing, bypass mode performing, context bin, bypass bin, transform coefficient, transform coefficient level, transform coefficient level scanning method, image display/output order, slice identification information, slice At least one value or a combination of information on a rice type, slice division information, tile identification information, tile type, tile division information, picture type, bit depth, luminance signal, or chrominance signal may be included in the encoding parameter.

Here, signaling the flag or index may mean entropy encoding the flag or index in the encoder and including the flag or index in the bitstream, and the decoder receives the flag or index from the bitstream. It may mean entropy decoding.

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

The quantized level may be dequantized by the dequantization unit 160 . An inverse transform may be performed in the inverse transform unit 170 . The inverse quantized and/or inverse transformed coefficients may be summed with the prediction block via an adder 175. A reconstructed block may be generated by summing the inverse quantized and/or inverse transformed coefficients and the prediction block. Here, the inverse quantized and/or inverse transformed coefficient means a coefficient on which at least one of inverse quantization and inverse transformation has been performed, and may mean a reconstructed residual block.

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

The deblocking filter may remove block distortion generated at the boundary between blocks. In order to determine whether to perform the deblocking filter, it may be determined whether to apply the deblocking filter to the current block based on pixels included in several columns or rows included in the block. When a deblocking filter is applied to a block, different filters can be applied according to the required deblocking filtering strength.

An appropriate offset value may be added to the pixel value in order to compensate for the encoding error using the sample adaptive offset. The sample adaptive offset may correct an offset from the original image on a pixel-by-pixel basis with respect to the image on which the deblocking has been performed. A method of dividing pixels included in an image into a certain number of areas, determining an area to be offset, and applying the offset to the area, or a method of applying the offset in consideration of edge information of each pixel may be used.

The adaptive loop filter may perform filtering based on a value obtained by comparing the reconstructed image and the original image. After dividing pixels included in an image into a predetermined group, a filter to be applied to the corresponding group is determined, and filtering can be performed differentially for each group. Information related to whether to apply the 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 according to 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 . 2 is a block diagram illustrating a configuration of a decoding apparatus to which the present invention is applied according to an embodiment.

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

Referring to FIG. 2 , the decoding apparatus 200 includes an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , a motion compensator 250 , and an adder 255 . , a filter unit 260 and a reference picture buffer 270 may be included.

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

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

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

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

The entropy decoding unit 210 may change a one-dimensional vector form coefficient into a two-dimensional block form through a transform coefficient scanning method in order to decode a transform coefficient level.

The quantized level may be inverse quantized by the inverse quantizer 220 and inversely transformed by the inverse transform unit 230 . The quantized level may be generated as a reconstructed residual block as a result of performing inverse quantization and/or inverse transformation. In this case, the inverse quantizer 220 may apply a quantization matrix to the quantized level.

When the intra mode is used, the intra prediction unit 240 may generate a prediction block by performing spatial prediction using pixel values of an already decoded block around the decoding object block.

When the inter mode is used, the motion compensator 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 region in the reference image. In order to perform motion compensation, based on the coding unit, it may be determined whether the motion compensation method of the prediction unit included in the corresponding coding unit is any of the skip mode, the merge mode, the AMVP mode, and the current picture reference mode, and each mode motion compensation may be performed accordingly.

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

FIG. 3 is a diagram schematically illustrating a split structure of an image when encoding and decoding an image. 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) may be used in encoding and decoding. An encoding unit may be used as a basic unit of image encoding/decoding. Also, when encoding/decoding an image, an encoding unit may be used as a unit for dividing an intra-screen mode and an inter-screen mode. The encoding unit may be a basic unit used for a process of prediction, transformation, quantization, inverse transformation, inverse quantization, or encoding/decoding of transform coefficients.

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

The partition structure may mean a distribution of coding units (CUs) within the LCU 310 . Such a distribution may be determined according to whether one CU is divided into a plurality of CUs (a positive integer of 2 or more including 2, 4, 8, 16, etc.). The horizontal size and vertical size of the CU created by division are half the horizontal size and half the vertical size of the CU before division, respectively, or a size smaller than the horizontal size and vertical size of the CU before division according to the number of divisions. can have A CU may be recursively divided into a plurality of CUs. The division of a CU may be made recursively up to a predefined depth or a predefined size. For example, the depth of the LCU may be 0, and the depth of a Smallest Coding Unit (SCU) may be a predefined maximum depth. Here, the LCU may be a coding unit having the largest coding unit size as described above, and the SCU may be a coding unit having the smallest coding unit size. The division starts from the LCU 310, and the depth of the CU increases by 1 whenever the horizontal size and/or the vertical size of the CU is reduced by the division.

Also, information on whether a CU is split may be expressed through split information of the CU. The division information may be 1-bit information. All CUs except for the SCU may include partition information. For example, if the value of the partitioning information is a first value, the CU may not be partitioned, and if the value of the partitioning information is a second value, the CU may be partitioned.

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

For example, when one coding unit is divided into 4 coding units, the horizontal and vertical sizes of the divided 4 coding units may have half sizes compared to the horizontal and vertical sizes of the coding units before splitting. have. For example, when a 32x32 coding unit is divided into 4 coding units, each of the divided 4 coding units may have a size of 16x16. When one coding unit is divided into four coding units, it can be said that the coding unit is divided into 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 have a half size compared to the horizontal or vertical size of the coding unit before splitting. . For example, when a 32x32 coding unit is vertically split into two coding units, each of the two split coding units may have a size of 16x32. When one coding unit is split into two coding units, it can be said that the coding unit is split in the form of a binary-tree. The LCU 320 of FIG. 3 is an example of an LCU to which both quadtree-type partitioning and binary tree-type partitioning are applied.

4 is a diagram for explaining an embodiment of an inter prediction process.

The rectangle shown in FIG. 4 may represent an image. Also, an arrow in FIG. 4 may indicate a prediction direction. Each image may be classified into an I picture (intra picture), a P picture (predictive picture), a B picture (bi-predictive picture), etc. according to the encoding type.

I-pictures may be encoded through intra prediction without inter prediction. A P picture may be encoded through inter prediction using only a reference picture existing in a unidirectional (eg, forward or backward) direction. A B picture may be encoded through inter prediction using reference pictures existing in bidirectional (eg, forward and backward) directions. Here, when inter prediction is used, the encoder may perform inter prediction or motion compensation, and the decoder may perform motion compensation corresponding thereto.

Below, inter prediction according to an embodiment will be described in detail.

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

Motion information on the current block may be derived during inter prediction by each of the encoding apparatus 100 and the decoding apparatus 200 . The motion information may be derived using motion information of a reconstructed neighboring block, motion information of a collocated block, and/or a block adjacent to the collocated block. The collocated block may be a block corresponding to the spatial position of the current block in an already reconstructed collocated picture (col picture). Here, the collocated picture may be one picture from among at least one reference picture included in the reference picture list.

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

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

The encoding apparatus 100 may calculate a motion vector difference (MVD) between a motion vector of a current block and a motion vector candidate, and may entropy-encode the MVD. Also, the encoding apparatus 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 among motion vector candidates included in the motion vector candidate list. The decoding apparatus 200 entropy-decodes the motion vector candidate index from the bitstream, and uses the entropy-decoded motion vector candidate index to select the motion vector candidate of the decoding object block from among the motion vector candidates included in the motion vector candidate list. . Also, the decoding apparatus 200 may derive the motion vector of the decoding object block through the sum of the entropy-decoded MVD and the motion vector candidate.

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

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

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

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

The skip mode may be a mode in which motion information of a neighboring block is applied to the current block as it is. When the skip mode is used, the encoding apparatus 100 entropy-encodes information on which block motion information is to be used as the motion information of the current block, and may signal it to the decoding apparatus 200 through a bitstream. In this case, the encoding apparatus 100 may not signal a syntax element related to at least one of motion vector difference information, a coding block flag, and a transform coefficient level to the decoding apparatus 200 .

The current picture reference mode may refer to a prediction mode using a pre-reconstructed region in the current picture to which the current block belongs. In this case, a vector may be defined to specify the pre-restored region. Whether the current block is encoded in the current picture reference mode may be encoded using a 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. When the current block is encoded in the current picture reference mode, the current picture may be added to a fixed position or an arbitrary position in the reference picture list for the current block. The fixed position may be, for example, a position in which the reference image index is 0 or the last position. When the current picture is added to an arbitrary position in the reference image list, a separate reference image index indicating the arbitrary position may be signaled.

Based on the above, an image encoding/decoding method according to the present invention will be described in detail.

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

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

Referring to FIG. 6 , the decoding apparatus entropy-decodes motion compensation information received from the encoding apparatus (S601), and may derive a motion vector candidate (S602). Then, the decoding apparatus may generate a motion vector candidate list based on the derived motion vector candidate (S603) and determine a motion vector by using the generated motion vector candidate list (S604). Thereafter, the decoding apparatus may perform motion compensation by using the motion vector (S605).

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

Referring to FIG. 7 , the encoding apparatus may derive 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 may be determined using the generated merge candidate list (S702), and motion compensation of the current block may be performed using the determined motion information (S703). Thereafter, the encoding apparatus may entropy-encode the motion compensation information (S704).

Referring to FIG. 8 , the decoding apparatus entropy-decodes motion compensation information received from the encoding apparatus (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, motion information of the current block may be determined using the generated merge candidate list (S803). Thereafter, the decoding apparatus may perform motion compensation using the motion information (S804).

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

Hereinafter, 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 descriptions of the motion compensation performing steps S504, S605, S703, and S804 and the entropy encoding/decoding steps S505, S601, S704, and S801 will be collectively described.

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

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

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

The spatial motion vector of the current block may be derived from a reconstructed block around the current block. For example, a motion vector of a reconstructed block adjacent to the current block may be determined as a spatial motion vector candidate for the current block.

9 is a diagram for explaining an example of deriving a spatial motion vector candidate of a 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 neighboring blocks adjacent to the current block include a block B1 adjacent to the top of the current block, a block A1 adjacent to the left of the current block, a block B0 adjacent to an upper right corner of the current block, and an upper left corner of the current block. It may include at least one of the block B2 adjacent to the corner and the block A0 adjacent to the lower left corner of the current block. Meanwhile, a neighboring block adjacent to the current block may have a square shape or a non-square shape. When 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 of 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 of the current block is based on whether the neighboring block exists or whether the neighboring block is encoded through inter prediction, etc. can be judged as In this case, 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 of the current block may be determined according to a predetermined priority. For example, in the example shown in FIG. 9 , availability of motion vectors may be determined in the block order of positions A0, A1, B0, B1, and B2.

When the reference image of the current block is different from the reference image of the neighboring block having the motion vector, the scaling of the motion vector of the neighboring block may be determined as a spatial motion vector candidate of the current block. Here, the scaling may be performed based on at least one of a distance between the current image and a reference image referenced by the current block and a distance between the current image and a reference image referenced by a neighboring block. For example, the spatial motion vector candidate of the current block is derived by scaling the motion vector of the neighboring 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 neighboring block. can be

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

In relation to scaling, a spatial motion vector candidate may be determined by scaling a motion vector of a neighboring block based on a reference image indicated by a reference image index having a predefined value. In this case, the predefined value may be a positive integer including 0. For example, according to the ratio of the distance between the current image and the reference image of the current block indicated by the reference image index having a predefined value and the distance between the current image and the reference image of the neighboring block having a predefined value, By scaling the motion vector, a spatial motion vector candidate of the current block can be derived.

Also, 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 a reconstructed block included in a co-located picture of the current image. Here, the corresponding position image is an image encoded/decoded before the current image, and may be an image having a different temporal order from the current image.

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

Referring to FIG. 10 , in a collocated picture of the current image, a block including an upper position of a block corresponding to a position spatially identical to the current block X or a position spatially identical to the current block X A temporal motion vector candidate of the current block may be derived from a block including the internal position of the block corresponding to . Here, the temporal motion vector candidate may mean a motion vector of a corresponding location block. For example, the temporal motion vector candidate of the current block (X) is a block (H) adjacent to the lower left corner of the block (C) corresponding to the spatially same position as the current block (H) or a block (C3) including the center point of the block (C) can be derived from A block H or block C3 used to derive a temporal motion vector candidate of the current block may be referred to as a 'collocated block'.

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

If the distance between the current image including the current block and the reference image of the current block is different from the distance between the corresponding position image including the corresponding position block and the reference image of the corresponding position block, the temporal motion vector candidate of the current block is the corresponding position It can be obtained by scaling the motion vector of the block. Here, the scaling may be performed based on at least one of a distance between the current image and a reference image referenced by the current block and a distance between the corresponding position image and a reference image referenced by the corresponding position 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 may be induced.

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

The generating of the motion vector candidate list may include adding or removing the motion vector candidate to the motion vector candidate list and adding the combined motion vector candidate to the motion vector candidate list.

From the step of adding or removing the derived motion vector candidate to the motion vector candidate list, the encoding apparatus and the decoding apparatus may 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 picture lists L0, L1, L2, and L3. For example, a motion vector candidate list corresponding to L0 in the reference picture list may be referred to as mvpListL0.

A motion vector having a predetermined value other than the spatial motion vector candidate and the temporal motion vector candidate may be added to the motion vector candidate list. For example, when 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 having a value of 0 may be added to the motion vector candidate list.

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

When the number of motion vector candidates included in the motion vector candidate list is smaller than the maximum number of motion vector candidates, a combined motion vector 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. For example, a combined motion vector candidate is generated by 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 or more of the encoding parameters, or the combined motion vector candidate may be added to the motion vector candidate list based on at least one or more of the encoding parameters.

Next, a step of determining a predicted motion vector from the motion vector candidate list will be described (S503 and S604).

A motion vector candidate indicated by a motion vector candidate index among motion vector candidates included in the motion vector candidate list may be determined as a predicted motion vector for the current block.

The encoding apparatus may calculate a difference between the motion vector and the predicted motion vector to calculate a motion vector difference value. The decoding apparatus may calculate the motion vector by summing the predicted motion vector and the motion vector difference.

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

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

First, the step of deriving a merge candidate will be described in detail (S701 and 802).

The merge candidate for the current block may include at least one of a spatial merge candidate, a temporal merge candidate, and an additional merge candidate. Here, inducing a spatial merge candidate may mean inducing a spatial merge candidate and adding the spatial merge candidate to the merge candidate list.

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

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

11 is a diagram for explaining an example in which a spatial merge candidate is added to a 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.

Also, 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 not only the motion information of L0 and L1 but also three or more pieces of motion information such as L2 and L3. Here, the reference image list may include at least one such as L0, L1, L2, and L3.

Next, a method of deriving a temporal merge candidate of the current block will be described.

The temporal merge candidate of 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 encoded/decoded before the current image, and may be an image having a different temporal order from the current image.

Inducing the temporal merge candidate may mean inducing the temporal merge candidate and adding it to the merge candidate list.

Referring to FIG. 10 , in a collocated picture of the current image, a block including an upper position of a block corresponding to a position spatially identical to the current block X or a position spatially identical to the current block X A temporal merge candidate of the current block may be derived from a block including the internal location of the block corresponding to . Here, the temporal merge candidate may mean motion information of a corresponding location block. As an example, the temporal merge candidate of the current block (X) is from a block (H) adjacent to the lower left corner of the block (C) corresponding to the spatially same position as the current block or a block (C3) including the center point of the block (C) can be induced. A block H or block C3 used to derive a temporal merge candidate of the current block may be referred to as a 'collocated block'.

When the temporal merge candidate of the current block can be derived from the block H including the position outside the block C, the block H may be set as the block corresponding to the current block. In this case, the temporal merge candidate of the current block may be derived based on the motion information of the block H. On the other hand, if the temporal merge candidate of the current block cannot be derived from the block H, block C3 including the internal location of the block C may be set as the corresponding block of the current block. In this case, the temporal merge candidate of the current block may be derived based on the motion information of the block C3. If the temporal merge of the current block cannot be derived from the block H and the block C3 (eg, when both the block H and the block C3 are coded in the picture), 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, the temporal merge candidate of 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.

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

Referring to FIG. 12 , when one temporal merge candidate is derived from the corresponding location block of the H1 location, the derived temporal merge candidate may be added to the merge candidate list.

When the distance between the current picture including the current block and the reference picture of the current block is different from the distance between the corresponding location image including 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 location block. Here, the scaling may be performed based on at least one of a distance between the current image and a reference image referenced by the current block and a distance between the corresponding position image and a reference image referenced by the corresponding position 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 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 may be generated by adding them to the merge candidate list in the order of the derived merge candidates.

Next, a method of deriving an additional merge candidate of the current block will be described.

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 having a predetermined motion information value. can do. Here, inducing an additional merge candidate may mean inducing an additional merge candidate and adding it to the merge candidate list.

The changed spatial merge candidate may mean a merge candidate in which at least one of motion information of the derived spatial merge candidate is changed.

The changed temporal merge candidate may mean a merge candidate in which at least one of motion information of the derived temporal merge candidate is changed.

The combined merge candidate is at least one of a spatial merge candidate, a temporal merge candidate, a modified spatial merge candidate, a modified temporal merge candidate, a combined merge candidate, and motion information of merge candidates having a predetermined motion information value existing in the merge candidate list. It may mean a merge candidate derived by combining motion information.

Alternatively, the combined merge candidate does not exist in the merge candidate list, but a spatial merge candidate and an induced temporal merge candidate derived from a block that can derive at least one of a spatial merge candidate and a temporal merge candidate, and a changed generated based on it It may mean 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 having a predetermined motion information value.

Alternatively, a combined merge candidate may be derived using motion information entropy-decoded from the bitstream in the decoder. In this case, the motion information used for derivation of the merge candidate combined in the encoder may be entropy-encoded in the bitstream.

The combined merge candidate may mean a combined bi-prediction merge candidate. The combined bi-prediction merge candidate is a merge candidate using bi-prediction and may mean a merge candidate having L0 motion information and L1 motion information.

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

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 derived or can create In addition, at least one of the changed spatial merge candidate, the changed temporal merge candidate, the combined merge candidate, and the merge candidate having a predetermined motion information value is based on at least one of the encoding parameters of the current block, the neighboring block, or the corresponding location 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 parameter of the current block, the neighboring block, or the corresponding block, and the size may be changed based on the encoding parameter.

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

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

Meanwhile, the encoder may 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 to generate the prediction block. Here, a prediction block of the current block may be generated by performing motion compensation based on the determined motion information.

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

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

The encoding apparatus and the decoding apparatus may calculate a motion vector by using the predicted motion vector and a difference value of the motion vector. When the motion vector is calculated, inter prediction or motion compensation may be performed using the calculated motion vector (S504 and S605).

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

The current block may have a minimum of 1 and a maximum of N motion vectors according to the prediction direction. A final prediction block of the current block may be derived by generating a minimum of 1 to a maximum of N prediction blocks using the motion vector.

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, when the current block has a plurality of motion vectors (or motion information), a plurality of prediction blocks are generated using the plurality of motion vectors (or motion information), and based on the weighted sum of the plurality of prediction blocks, the current The final prediction block of the block may be determined. Reference pictures including each of a plurality of prediction blocks indicated by a plurality of motion vectors (or motion information) may be included in different reference picture lists or may be included in the same reference picture list.

For 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 having a predetermined value, or a combined motion vector candidate, and based on a weighted sum of the plurality of prediction blocks , it is possible to determine the last prediction block of the current block.

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

A weight applied to each prediction block may have an equal value as 1/N (where N is the number of generated prediction blocks). For example, when two prediction blocks are generated, a weight applied to each prediction block is 1/2, when three prediction blocks are generated, a weight applied to each prediction block is 1/3, and 4 predictions When blocks are generated, a weight applied to each prediction block may be 1/4. Alternatively, the final prediction block of the current block may be determined by giving different weights to each prediction block.

The weight does not have to have a fixed value for each prediction block, but may have a variable value for each prediction block. In this case, the weights applied to each prediction block may be the same or different from each other. For example, when two prediction blocks are generated, the weights applied to the two prediction blocks are (1/3, 2/3), (1/4, 3) as well as (1/2, 1/2). /4), (2/5, 3/5), (3/8, 5/8), etc., may be a variable value for each block. Meanwhile, the weight may be a value of a positive real number or a value of a negative real number. As an example, it may include a negative real number value such as (-1/2, 3/2), (-1/3, 4/3), (-1/4, 5/4), and the like.

Meanwhile, in order to apply a variable weight, one or more weight information for the current block may be signaled through a bitstream. Weight information may be signaled for each prediction block, or may be signaled for each reference picture. It is also possible for a plurality of prediction blocks to share one piece of weight information.

The encoding apparatus and the decoding apparatus may 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 picture list indicates the first value of 1, the encoding apparatus and the decoding apparatus may use the predicted motion vector of the current block to perform inter prediction or motion compensation. and indicates that the second value 0 is indicated, the encoding apparatus and the decoding apparatus may indicate that inter prediction or motion compensation is not performed 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 examples of generating the final prediction block of the current block when the inter prediction indicators of the current block are PRED_BI, PRED_TRI, and PRED_QUAD, respectively, and the prediction direction for each reference picture list is unidirectional. indicates

In Equations 1 to 3, P_BI, P_TRI, and P_QUAD may represent a final prediction block of the current block, and LX (X=0, 1, 2, 3) may mean a reference picture list. WF_LX may indicate a weight value of a prediction block generated using LX, and OFFSET_LX may indicate an offset value with respect to a prediction block generated using LX. P_LX refers to a prediction block generated by using a motion vector (or motion information) for LX of the current block. RF means a rounding factor, and may be set to 0, a positive number, or a negative number. The LX reference picture list includes a long-term reference picture, a reference picture that does not perform a deblocking filter, a reference picture that does not perform a sample adaptive offset, and an adaptive loop filter. A reference picture without loop filter), a reference picture with only deblocking filter and adaptive offset, a reference picture with only deblocking filter and adaptive loop filter, and reference with sample adaptive offset and adaptive loop filter At least one of a reference image on which an image, a deblocking filter, a sample adaptive offset, and an adaptive loop filter are all performed may be included. In this case, the LX reference image list may be at least one of the L2 reference image list and the L3 reference image list.

Even when a prediction direction for a predetermined reference image list is plural, a final prediction block for the current block may be obtained based on a weighted sum of the prediction blocks. In this case, the weights applied to the prediction blocks derived from the same reference image list may have the same value or different values.

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

As another example, the weight and the 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 is greater, the weight or offset may be set to a smaller value, and as the distance between the current image and the reference image is shorter, the weight or offset may be set to a greater value. For example, when the POC difference between the current image and the L0 reference image is 2, the weight value applied to the prediction block generated by referring 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. When is 1, the weight value applied to the prediction block generated by referring to the L0 reference image may 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, entropy encoding/decoding may be performed on at least one of a weight and an offset based on at least one of the encoding parameters. In addition, a weighted sum of prediction blocks may be calculated based on at least one of the encoding parameters.

The weighted sum of the plurality of prediction blocks may be applied only to a partial region within the prediction block. Here, the partial region may be a region corresponding to a boundary within the prediction block. As described above, in order to apply the weighted sum to only a partial region, the weighted sum may be performed in units of sub-blocks of the prediction block.

Inter-prediction or motion compensation may be performed using the same prediction block or the same final prediction block in sub-blocks having a smaller block size within a block having a block size indicated by the region information.

In addition, inter prediction or motion compensation may be performed using the same prediction block or the same final prediction block in sub-blocks having a deeper block depth within a block having a block depth indicated by the region information.

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

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

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

For example, it is possible to generate prediction blocks only from motion vector candidates having specific motion vector candidate indices, calculate a weighted sum of the prediction blocks, and use the calculated weighted sum as a final prediction block of the current block.

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

In addition, when calculating the weighted sum of prediction blocks using the merge mode, the weighted sum may 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 may be generated using only spatial merge candidates, a weighted sum of the prediction blocks may be calculated, and the calculated weighted sum may be used as the final prediction block of the current block.

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

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

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

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

The encoder and the decoder may perform motion compensation using motion vectors/information included in the current block. In this case, the final prediction block resulting from 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.

A final prediction block may be generated by performing overlapped block motion compensation on an 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 neighboring blocks of the current block. Here, the area corresponding to the boundary within the current block is one of the upper boundary area, the left boundary area, the lower boundary area, the right boundary area, the upper right corner area, the lower right corner area, the upper left corner area, and the lower left corner area in the current block. It may include at least one or more. Also, the region corresponding to the boundary within the current block may be a region corresponding to a portion within the prediction block of the current block.

In the overlapping block motion compensation, motion compensation is performed by calculating a weighted sum of the prediction block region corresponding to the boundary within the current block and the prediction block generated using motion information of the coded/decoded block adjacent to the current block. can mean

The weighted summation may be performed in units of sub-blocks after dividing the current block into a plurality of sub-blocks. That is, motion compensation may be performed using motion information of a block coded/decoded adjacent to the current block in units of sub-blocks. In this case, the sub-block may mean a sub-block.

In addition, in the weighted sum calculation, a first prediction block generated in units of sub-blocks using motion information of the current block and a second prediction block generated using motion information of neighboring sub-blocks spatially adjacent to the current block may be used. . In this case, using the motion information may mean inducing the motion information. In addition, the first prediction block may mean a prediction block generated using motion information of a sub-block to be encoded/decoded in the current block. Also, here, the second prediction block may refer to a prediction block generated by using motion information of a neighboring sub-block spatially adjacent to a sub-block to be encoded/decoded within the current block.

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

In addition, Advanced Motion Vector Prediction (AMVP), merge mode, affine motion compensation mode, decoder motion vector derivation mode, adaptive motion vector resolution mode, local illumination compensation mode, bidirectional optical flow When at least one of the modes is applicable, after dividing the current prediction block into sub-blocks, the overlapping block motion compensation for each sub-block may be performed.

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

A detailed description of the overlapped block motion compensation will be described later with reference to FIGS. 13 to 24 .

Next, the process of entropy encoding/decoding of motion compensation information will be described in detail (S505, S601, S704, and S801).

The encoding apparatus entropy-encodes motion compensation information through a bitstream, and the decoding apparatus entropy-decodes motion compensation information included in the bitstream. Here, the entropy-encoded/decoded motion compensation information includes an Inter Prediction Indicator (inter_pred_idc), a reference image index (ref_idx_l0, ref_idx_l1, ref_idx_l2, ref_idx_l3), a motion vector candidate index (mvp_mvp_l1_idxx_idxl0_idx, , mvp_l3_idx), motion vector difference, skip mode use information (cu_skip_flag), merge mode use 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, and offset_l3).

The inter prediction indicator may mean at least one of an inter prediction direction or the number of prediction directions of the current block when encoded/decoded by inter prediction of the current block. As an example, the inter prediction indicator may indicate unidirectional prediction or multi-directional prediction such as bidirectional prediction, three-way prediction, or four-way prediction. The inter 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 a plurality of directions. In this case, N (N>M) direction predictions may be performed using M reference images. The inter prediction indicator may mean the number of prediction blocks used when inter prediction or motion compensation is performed on 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 directions according to the number of prediction directions of the current block.

A prediction list utilization flag indicates whether a prediction block is generated using a 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 reference image list, and when the second value indicates 0, the reference image list is used It 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 use flag indicates the first value, the prediction block of the current block may be generated using motion information corresponding to the reference picture list.

The reference image index may specify a reference image referenced by the current block in each reference image list. One or more reference picture indexes may be entropy-encoded/decoded for each reference picture list. The current block may perform motion compensation using one or more reference image indexes.

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

The motion vector difference indicates a difference value between the motion vector and the predicted motion vector. One or more motion vector differences may be entropy-encoded/decoded with respect to the reference picture list or the motion vector candidate list generated for each reference picture index with respect to the current block. The current block may perform motion compensation by using one or more motion vector differences.

Skip mode use or not information cu_skip_flag may indicate skip mode use when it has a first value of 1, and may not indicate use of skip mode when it has a second value of 0. Motion compensation of the current block may be performed using the skip mode based on the skip mode usage information.

The merge mode usage information (merge_flag) may indicate use of the merge mode when it has a first value of 1, and may not indicate use of the merge mode when it has a second value of 0. Motion compensation of the current block may be performed using the merge mode based on whether or not the merge mode is used.

The merge index information (merge_index) may mean information indicating a merge candidate in a merge candidate list.

Also, the merge index information may mean information on a merge index.

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

Also, the merge index information may indicate at least one or more pieces of motion information of a merge candidate. For example, the merge index information may indicate a first merge candidate in the merge candidate list when it has a first value of 0, and may indicate a second merge candidate in the merge candidate list when it has a second value of 1, When it has a third value of 2, it is possible to indicate a third merge candidate in the merge candidate list. Similarly, when the 4th to Nth values are present, the merge candidates corresponding to the values may be indicated according to the order in the merge candidate list. Here, N may mean a positive integer including 0.

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

When two or more prediction blocks are generated during motion compensation for the current block, a final prediction block for the current block may be generated through a weighted sum of each prediction block. In the weighted sum operation, at least one of a weight and an offset may be applied to each prediction block. A weighting factor used in the weighting operation, such as a weighting factor or an offset, includes a reference picture list, a reference picture, a motion vector candidate index, a motion vector difference, a motion vector, information on whether to use a skip mode, and a merge mode. Entropy encoding/decoding may be performed by the number of at least one or more than at least one of the use availability information and the merge index information. In addition, the weighting factor of each prediction block may be entropy-encoded/decoded based on the inter prediction indicator. Here, the weighting factor may include at least one of a weight and an offset.

Information on motion compensation may be entropy-encoded/decoded in block units or entropy-encoded/decoded at a higher level. For example, information on motion compensation may be entropy encoded/decoded in units of blocks such as CTU, CU, or PU, or may be a video parameter set, a sequence parameter set, or a picture parameter set. ), an adaptation parameter set (Adaptation Parameter Set), or a slice header (Slice Header) may be entropy-encoded/decoded at a higher level.

The motion compensation information may be entropy encoded/decoded based on a difference value of the motion compensation information indicating a difference value between the motion compensation information and the motion compensation information prediction value.

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

Also, at least one of the motion compensation-related information may be derived based on at least one or more of the encoding parameters.

In addition, at least one or more of the motion compensation information may be entropy-decoded from the bitstream based on at least one or more of the encoding parameters. At least one or more of the motion compensation information may be entropy-encoded into a bitstream based on at least one of the encoding parameters.

The motion compensation information includes a motion vector, a motion vector candidate, a motion vector candidate index, a motion vector difference value, a motion vector prediction value, information on whether to use skip mode (skip_flag), information on whether to use merge mode (merge_flag), and information on merge index (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 derivation (decoder-side motion vector derivation) information and bi-directional optical flow information. Here, the decoder motion vector derivation may mean pattern matched motion vector derivation.

The motion vector resolution information may be information indicating whether a specific resolution is used for at least one of a motion vector and a motion vector difference value. Here, the resolution may mean precision. In addition, specific resolutions are 16-pel units, 8-pel units, 4-pel units, integer-pel units, and 1/2-pixel units. (1/2-pel) units, 1/4-pel units, 1/8-pixel units (1/8-pel) units, 1/16-pixel units (1/16-pel) units , 1/32-pixel (1/32-pel) unit, and 1/64-pixel (1/64-pel) unit.

The overlapped block motion compensation information may be information indicating whether to calculate a weighted sum of the prediction blocks of the current block by additionally using motion vectors of neighboring blocks spatially adjacent to the current block when the motion compensation of the current block is performed.

The 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 for motion compensation for the current block. Here, the affine motion model may be a model in which one block is divided into a plurality of sub-blocks using a plurality of parameters, and a motion vector of the divided sub-block is calculated using representative motion vectors.

The decoder motion vector derivation information may be information indicating whether a motion vector required for motion compensation is derived and used by the decoder. Information on motion vectors may not be entropy-encoded/decoded based on the decoder motion vector derivation information. In addition, when the decoder motion vector derivation information indicates that the decoder derives and uses the motion vector, information on the merge mode may be entropy-encoded/decoded. That is, the decoder motion vector derivation information may indicate whether the decoder uses the merge mode.

The bidirectional optical flow information may be information indicating whether motion compensation is performed by correcting a motion vector in units of pixels or sub-blocks. Based on the bidirectional optical flow information, the motion vectors in units of pixels or sub-blocks may not be entropy-encoded/decoded. Here, the motion vector calibration may be to change a motion vector value in units of blocks to a motion vector in units of pixels or subblocks.

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

In case of entropy encoding/decoding of motion compensation-related information, a truncated rice binarization method, a K-th order Exp_Golomb binarization method, a limited K-th order Exp_Golomb binarization method, and a K-th order Exp_Golomb ), a binarization method such as a binarization method, a fixed-length binarization method, a unary binarization method, or a truncated unary binarization method may be used.

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

In addition, when entropy encoding/decoding of motion compensation information, information on motion compensation of neighboring blocks, information on previously coded/decoded motion compensation, information on the depth of the current block, and 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 the motion compensation information of the current block.

Hereinafter, a detailed description related to overlapped block motion compensation will be described with reference to FIGS. 13 to 24 .

* FIG. 13 is a diagram for explaining an example in which overlapping block motion compensation is performed in units of sub-blocks.

Referring to FIG. 13 , the shaded block is a region to which the overlapping block motion compensation is applied, and may be a sub-block corresponding to a boundary within the current block or a sub-block within the current block. Also, a block indicated by a thick line may be a current block.

Also, the arrow may mean that motion information of an adjacent neighboring sub-block 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. Also, a position corresponding to the head of the arrow may mean a current sub-block within the current block.

In the shaded block, a weighted sum of the first prediction block and the second prediction block may be calculated. As the motion information used to generate the first prediction block, motion information on a current sub-block in the current block may be used. 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 may be used as the motion information used to generate the second prediction block.

In addition, in order to improve encoding efficiency, motion information used to generate the second prediction block is an upper block, a left block, a lower block, a right block, an upper right block, a lower right block, and an upper left based on the position of the current lower block in the current block. It may be motion information of at least one block among a block and a lower left block. The positions of available neighboring sub-blocks may be determined according to the positions of the current sub-blocks. For example, when the current sub-block is located at the upper boundary, at least one neighboring sub-block located at the top, upper right, and upper left of the current sub-block may be used. When the current sub-block is located at the left boundary, at least one neighboring sub-block located at the left, upper left, and lower left of the current sub-block may be used.

Here, based on the position of the current sub-block, the upper block, left block, lower block, right block, upper right block, lower right block, upper left block, and lower left block are the upper neighboring subblock, the left neighboring subblock, and the lower neighboring subblock , the right surrounding sub-block, the upper right surrounding sub-block, the lower right surrounding sub-block, the upper left surrounding sub-block, and the lower left surrounding sub-block.

Meanwhile, in order to reduce computational complexity, motion information used to generate the second prediction block may vary according to a motion vector size 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, when neighboring sub-blocks are predicted in both directions, the second prediction block may be generated by comparing the magnitudes of motion vectors in the L0 and L1 directions, and using only motion information in one direction having a larger magnitude.

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

Also, in order to reduce computational complexity, motion information used to generate the second prediction block may vary according to the magnitude and direction of the motion vector of the current sub-block.

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

As another example, if the absolute value of the y component is large after comparing the magnitude of the absolute value of the x component and the y component of the motion vector of the current lower block, the second prediction is made using at least one of motion information of the upper block and the lower block. blocks can be created.

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

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

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

Also, the size of the sub-block may be determined according to the size of the current block. For example, when the size of the current block is K samples or less, a 4x4 sub-block may be used, and when the size of the current block is greater than K samples, an 8x8 sub-block may be used. Here, K is a positive integer, and may be, for example, 256.

Here, the information on the size of the sub-block may be entropy-encoded/decoded in at least one of a sequence unit, a picture unit, a slice unit, a tile unit, a CTU unit, a CU unit, and a PU unit. In addition, as the size of the lower block, a size predefined in the encoder and the decoder may be used.

The sub-block may have at least one of a square shape and a rectangular shape. For example, when the current block has a square shape or a rectangular shape, the sub-block may have a square shape.

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

Here, the information on the shape of the sub-block may be entropy-encoded/decoded and used in at least one of a sequence unit, a picture unit, a slice unit, a tile unit, a CTU unit, a CU unit, and a PU unit. In addition, the form of the sub-block may use a form predefined in the encoder and the decoder.

14 is a view for explaining an example in which superimposed block motion compensation is performed using motion information of a lower block of a corresponding location block. In order to improve encoding efficiency, motion information of a sub-block corresponding to the spatially identical position to the current block in the corresponding-position image or reference image may 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 in the corresponding location block may be used for motion compensation of the overlapping block of the current sub-block. Here, the position corresponding to the arrow tail may mean a sub-block within the corresponding position block. Also, a position corresponding to the head of the arrow may mean a current sub-block within the current block.

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

15 is a diagram illustrating an example in which overlapped block motion compensation is performed using motion information of a block adjacent to a boundary region of a reference block. In order to improve encoding efficiency, a reference block in a reference image is identified using at least one of a motion vector and a reference image index of the current block, and motion information of a neighboring block adjacent to the boundary of the identified reference block is generated to generate a second prediction block It can be used as motion information used for Here, the neighboring block may include an encoded/decoded block adjacent to a lower block located in the lower boundary region or the right boundary region of the reference block.

Referring to FIG. 15 , motion information of a block coded/decoded adjacent to the lower boundary region and the right boundary region of the reference block may be used for motion compensation of the overlapping block of the current lower block.

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

Meanwhile, in order to improve encoding efficiency, at least one or more motion information among merge candidates included in the merge candidate list may 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 prediction modes.

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

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

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

Alternatively, in order to improve encoding efficiency, at least one motion vector among motion vector candidates included in the motion vector candidate list may 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 the AMVP mode among the inter prediction modes.

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

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

When at least one of the above-described merge candidates and motion vector candidates is used as motion information used to generate the second prediction block, the region to which the overlapped block motion compensation is applied may be different. The area to which the overlapped block motion compensation is applied is set to an area adjacent to one boundary of the block (ie, a sub-block located at the block boundary) or an area not adjacent to the block boundary (ie, a sub-block not located at the block boundary), etc. can be

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

For example, block motion compensation overlapped in a region not adjacent to a block boundary may be performed using motion information of a spatial merge candidate or a spatial motion vector candidate.

As another example, block motion compensation overlapped in a region not adjacent to a block boundary may be performed using motion information of a temporal merge candidate or a temporal motion vector candidate.

As another example, block motion compensation superimposed on the lower boundary region and the right boundary region of the block may be performed using motion information of a spatial merge candidate or a spatial motion vector candidate.

As another example, block motion compensation superimposed on the lower boundary region and the right boundary region of the block may be performed using motion information of a temporal merge candidate or a temporal motion vector candidate.

In addition, in order to improve encoding efficiency, motion information derived from a specific location block in the merge candidate list or the motion vector candidate list may be used to compensate for motion of an overlapping block for a specific region.

For example, when motion information derived from the upper right block with respect to the current block is included in the merge candidate list or the motion vector candidate list, the corresponding motion information can be used to compensate for motion of an overlapped block in the right boundary region of the block.

As another example, when motion information derived from the lower left block with respect to the current block is included in the merge candidate list or the motion vector candidate list, the corresponding motion information can be used to compensate for motion of an overlapping block in the lower boundary region of the block. .

16 is a view for explaining an example in which overlapping block motion compensation is performed in units of lower block groups. In order to reduce computational complexity, the sub-block-based superimposed block motion compensation may be performed in units of one or more blocks in which several sub-blocks are combined. In this case, a block unit in which several sub-blocks are combined may mean a sub-block group unit.

Referring to FIG. 16 , each area separated from the hatched area may mean a sub-block group. Also, the arrow may mean that motion information of an adjacent neighboring sub-block 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. Also, a position corresponding to the head of the arrow may mean a current sub-block group within the current block.

In the lower block group, a weighted sum of the first prediction block and the second prediction block may be calculated. As motion information used to generate the first prediction block, motion information for a current sub-block group in the current block may be used. Here, the motion information for the current sub-block group in the current block may be any one of an average value, a median value, a minimum value, a maximum value, or a weighted sum of motion information for a sub-block included in the sub-block group. The motion information used when generating the second prediction block includes motion information of a neighboring sub-block adjacent to the current block, motion information of a neighboring sub-block group adjacent to the current block, and a neighboring sub-block adjacent to the current sub-block within the current block. At least one or more of the motion information of may be used. Here, the motion information of a neighboring sub-block group adjacent to the current block may be any one of an average value, a median value, a minimum value, a maximum value, or a weighted sum of motion information for a sub-block 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. Also, 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. Also, block motion compensation superimposed on at least one of sub-blocks positioned at an upper boundary within the current block and sub-blocks positioned at a left boundary within the current block may be performed.

Meanwhile, since blocks adjacent to the lower boundary and the right boundary of the current block are not encoded/decoded, a block overlapping at least one of the lower boundary within the current block and the lower blocks located on the right boundary within the current block Motion compensation may not be performed. Alternatively, since blocks adjacent to the lower boundary and the right boundary of the current block are not coded/decoded, the current sub-block is located in at least one of the lower boundary within the current block and the lower blocks located on the right boundary within the current block. The overlapped block motion compensation may be performed using motion information of at least one of an upper block, a left block, an upper left block, a lower left block, and an upper right block.

In addition, when the current block is in the merge mode and at least one of an enhanced temporal motion vector prediction candidate and a spatial-temporal motion vector prediction candidate is at least one, lower-order blocks located at the lower boundary within the current block and lower-level blocks located at the right boundary within the current block Block motion compensation superimposed on at least one of them 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 motion superimposed on at least one of sub-blocks located at the lower boundary within the current block and sub-blocks located at the right boundary within the current block Compensation may not be performed.

Meanwhile, the overlapped block motion compensation may be performed on at least one of color components of the current block. In this case, the color component may include at least one of a luminance component and a color difference component.

Also, the overlapped block motion compensation may be performed according to the inter prediction indicator of the current block. That is, it may be performed when the current block is at least one of unidirectional prediction, bidirectional prediction, three-way prediction, four-way prediction, and the like. Also, it can be performed only when the current block is unidirectional prediction. Also, it can be performed only when the current block is a bidirectional prediction.

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

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

For example, when generating the second prediction blocks using motion information of a neighboring sub-block adjacent to the current block, a maximum of two pieces of motion information may be derived using at least one of an upper block and a left block. In addition, when generating second prediction blocks using motion information of neighboring sub-blocks adjacent to the current sub-block in the current block, the upper block, the left block, the lower block, the right block, the upper left block, the upper right block, the lower left block and at least one of the lower right blocks may be used to derive up to four pieces of motion information. In this case, deriving the motion information may mean generating a second prediction block using the derived motion information and then using the generated second prediction block for motion compensation of the overlapped block.

Referring to FIG. 17 , in order to improve encoding efficiency, motion information used to generate a second prediction block when it corresponds to at least one of subblocks located at the upper boundary within the current block and lower blocks located at the left boundary within the current block. can be induced up to three. That is, motion information used to generate the second prediction block may be derived using 3-connectivity.

For example, blocks corresponding to the upper boundary area within the current block may derive motion information from at least one of a neighboring upper block, a neighboring upper left block, and a neighboring upper right block adjacent to the current block.

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

In addition, blocks corresponding to the upper-left boundary area within the current block may derive motion information from at least one of a neighboring upper block that is a neighboring sub-block adjacent to the current block, a neighboring left block, and a neighboring upper-left block.

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

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

Meanwhile, in order to improve encoding efficiency, when it does not correspond to at least one of the lower blocks located at the upper boundary within the current block and the lower blocks located at the left boundary within the current block, the motion information used for generating the second prediction block is maximized. Up to 8 can be induced. That is, motion information used for generating the second prediction block may be derived using 8-connectivity.

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

Meanwhile, motion information used for generating the second prediction block may be derived even from a sub-block of the corresponding position in the corresponding position image. Also, motion information used for generating the second prediction block may be derived from blocks that are encoded/decoded adjacent to the lower boundary region and the right boundary region of the reference block in the reference image.

In addition, in order to improve encoding efficiency, the number of motion information used to generate the second prediction block may be determined according to the magnitude or direction of the motion vector.

For example, when the sum of the absolute values of the x component and the y component of the motion vector is equal to or greater than J, a maximum of L may be used as the number of motion information. Conversely, when the sum of the absolute values of the x component and the y component of the motion vector is less than J, a maximum of P may be used as the number of motion information. In this case, J, L, and P may be positive integers including 0. L and P are preferably different values, but may have the same value.

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

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

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

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

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

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

For example, blocks corresponding to the upper boundary area within the current block may derive motion information in the order of 1) a neighboring upper block adjacent to the current block, 2) a neighboring upper left block, and 3) a neighboring upper right block.

Also, blocks corresponding to the left boundary region within the current block may derive motion information in the order of 1) a neighboring left block adjacent to the current block, 2) a neighboring upper-left block, and 3) a neighboring lower-left block.

Also, blocks corresponding to the upper-left boundary area within the current block may derive motion information in the order of 1) a neighboring upper block adjacent to the current block, that is, 1) a neighboring upper block, 2) a neighboring left block, and 3) a neighboring upper-left block.

Also, blocks corresponding to the upper-right boundary area within the current block may derive motion information in the order of 1) a neighboring upper block adjacent to the current block, 2) an upper-left block, and 3) a neighboring upper-right block.

In addition, blocks corresponding to the lower-right boundary area within the current block may derive motion information in the order of 1) a neighboring sub-block adjacent to the current block, 1) a neighboring left block, 2) a neighboring upper-left block, and 3) a neighboring lower-left block. .

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

Meanwhile, the motion information of the sub-block at the corresponding location in the image of the corresponding location may be derived at a lower rank than the neighboring sub-blocks spatially adjacent to the current sub-block. Also, the motion information of the sub-block at the corresponding location in the image of the corresponding location may be derived in a higher order than the neighboring sub-blocks spatially adjacent to the current sub-block.

Also, motion information of a block coded/decoded adjacent to the lower boundary region and the right boundary region of the reference block in the reference image may be derived with a lower priority than the neighboring sub-blocks spatially adjacent to the current sub-block. Also, motion information of a block coded/decoded adjacent to the lower boundary region and the right boundary region of the reference block in the reference image may be derived with a higher priority than the neighboring sub-blocks spatially adjacent to the current sub-block.

Motion information 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 may be derived as motion information used for generating the second prediction block only when a specific condition is satisfied.

For example, when at least one of a neighboring sub-block adjacent to the current block and a neighboring sub-block adjacent to the current sub-block in the current block exist, motion information of the existing neighboring sub-block is used to generate the second prediction block. can be induced by

As another example, when at least one of a neighboring sub-block adjacent to the current block and a neighboring sub-block adjacent to the current sub-block within the current block is in the inter prediction mode, motion information of at least one neighboring sub-block in the inter prediction mode is obtained. It can be derived from motion information used to generate the second prediction block. On the other hand, when 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 prediction mode, there is no motion information in the corresponding block, so 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 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, uni-prediction, bi-prediction, 3 When at least one of the four-direction prediction and the four-direction prediction is not indicated, motion information used to generate the second prediction block may not be derived.

Meanwhile, when 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.

Also, when 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.

Also, when the reference image index used for generating the second prediction block is not the same as the reference image index used for generating the first prediction block, motion information used for generating the second prediction block may be derived.

In addition, when at least one of a motion vector and a reference picture index used to generate the second prediction block is not the same as at least one of a motion vector and a reference picture index used to generate the first prediction block, it is used to generate the second prediction block motion information to be used may be derived.

In addition, in order to reduce complexity, when the inter prediction indicator used to generate the first prediction block indicates unidirectional prediction, at least one of motion vectors and reference image indexes for L0 and L1 prediction directions used to generate the second prediction block When one is not the same as at least one of a motion vector and a reference image index used for generating the first prediction block, motion information used for generating the second prediction block may be derived.

In addition, in order to reduce complexity, based on the inter prediction indicator used to generate the first prediction block, when the inter prediction indicator indicates bidirectional prediction, the L0 and L1 prediction directions used to generate the second prediction block are When at least one of a combination of a motion vector and a reference picture index is not the same as at least one of a combination of a motion vector and a reference picture index for L0 and L1 prediction directions used for generating the first prediction block, the second prediction block is generated Motion information used may be derived.

In addition, in order to reduce complexity, when at least one or more of the motion information used to generate the second prediction block is not the same as at least one or more of the motion information used to generate the first prediction block, the second prediction block is used for generation. Motion information may be derived.

20 is a diagram for explaining an example of determining whether motion information is usable for generating a second prediction block by comparing a POC of a reference picture of a current sub-block and a POC of a reference picture of a neighboring sub-block.

Referring to FIG. 20 , in order to reduce complexity, when the POC of the reference picture of the current sub-block and the POC of the reference picture of the neighboring sub-block are the same, the motion information of the current sub-block is used to generate the second prediction block of the current sub-block. 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. Motion information used for .

Specifically, when the POC of the reference picture used to generate the second prediction block is not the same as the POC of the reference picture used to generate the first prediction block, the motion vector used to generate the second prediction block is generated by generating the first prediction block. By performing motion vector scaling based on the reference image used for , or the POC of the reference image, a motion vector used for generating the second prediction block may be derived.

21 is a diagram for explaining an embodiment of applying a weight when calculating a weighted sum of a first prediction block and a second prediction block.

In calculating the weighted sum of the first prediction block and the second prediction block, different weights may be used for each row or each column according to the sample position in the block. In addition, a weighted sum between samples corresponding to the same position in the first prediction block and the second prediction block may be calculated. In this case, at least one of a weight and an offset may be used when calculating a weighted sum for generation of the final prediction block.

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

Meanwhile, in 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 , a weight such as {3/4, 7/8, 15/16, 31/32} may be used for each row or each column for the first prediction block, and for the second prediction block, for each row Alternatively, a weight such as {1/4, 1/8, 1/16, 1/32} may be used for each column. In this case, as the weights, the same weights may be used at sample locations belonging to the same row or sample locations belonging to the same column.

For each weight, a weight having a larger value may be used as it is closer to the boundary of the current lower block. In addition, each weight may be applied to all samples in a lower block.

21 (a), (b), (c) and (d) are generated using motion information of a neighboring upper block, motion information of a neighboring lower block, motion information of a neighboring left block, and motion information of a neighboring right block. Examples of generating two prediction blocks may each be shown. Here, the upper second prediction block, the lower second prediction block, the second left prediction block, and the second right prediction block include motion information of the neighboring upper block, motion information of the neighboring lower block, motion information of the neighboring left block, and the neighboring right block. It may mean a second prediction block generated based on motion information of .

22 is a diagram for explaining an embodiment in which different weights are applied according to sample positions in blocks when a weighted sum of a first prediction block and a second prediction block is calculated. In order to improve encoding efficiency, different weights may be used according to sample positions within the block when calculating the weighted sum of the first prediction block and the second prediction block. That is, the weighted sum may be calculated with different weights according to positions of blocks spatially adjacent to the current sub-block. Also, a weighted sum between samples corresponding to the same position in the first prediction block and the second prediction block may be calculated.

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

In addition, the weight for the second prediction block generated by using motion information of the sub-block at the corresponding position in the corresponding position image may be the same at all sample positions.

Also, the weight of the second prediction block generated by using motion information of the sub-block at the corresponding position in the image of the corresponding position may be the same as the weight of the first prediction block.

In addition, weights for the second prediction block generated using motion information of blocks coded/decoded adjacent to the lower boundary region and the right boundary region of the reference block in the reference image may be the same at all sample positions.

In addition, the weight of the second prediction block generated using motion information of blocks that are encoded/decoded adjacent to the lower boundary region and the right boundary region 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 according to a motion vector size 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 the y component of the neighboring subblock is equal to or greater than a predefined value, {1/2, 3/4, 7/8, {1/2, 3/4, 7/8, 15/16} can be used. On the other hand, if the sum of the absolute values of the motion vector x component and the y component of the neighboring sub-block is less than a predefined value, {7/8, 15/16, 31/32, 63/64} as the weight of the current sub-block. can be used In this case, the predefined value may be a positive integer including 0.

Also, in order to reduce computational complexity, the weight value may vary according to the motion vector magnitude or motion vector direction of the current sub-block.

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

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

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

Also, when the size of the current block is less than NxM, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. In addition, when the current block is divided into sub-blocks and motion compensation is performed, 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. Also, 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 as or different from each other.

Also, 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. In this case, K may be a positive integer including 0, for example, 1 or 2. Also, 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. Also, when the current block is a color difference component, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary.

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

Also, 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. Also, when the current block is in the affine motion compensation mode, a weighted sum may be calculated for samples located in K rows/columns adjacent to each block boundary. In this case, K may be a positive integer including 0, for example, 1 or 2.

Meanwhile, 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 size of a sub-block of the current block.

For example, when the size of a sub-block of the current block is 4x4, a weighted sum may be calculated for samples located in one, two, three, or four rows/columns adjacent to each block boundary. In addition, when the size of the sub-block 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 for In this case, K is a positive integer including 0, and can have as many rows/columns as the maximum value of the lower block.

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

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

Also, when 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.

In addition, 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 prediction indicator of the current block. K may be a positive integer including 0.

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

Also, 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 POC of the reference image of the current block. Here, K may be a positive integer including 0.

For example, when 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, when 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, weighted sum of samples located in K rows/columns adjacent to each block boundary according to the motion vector size 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 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 x component and the y component of the neighboring subblock is equal to or greater than a predefined value, the weighted sum is calculated for samples located in two rows/columns adjacent to each block boundary. can On the other hand, when the sum of the absolute values of the motion vector x component and the y component of the neighboring sub-block is less than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary. In this case, the predefined value may be a positive integer including 0.

Also, 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 motion vector magnitude or motion vector direction of the current sub-block. Here, K may be a positive integer including 0.

For example, when the absolute value of the motion vector x component of the current sub-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, when the absolute value of the motion vector x component of the current sub-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. In this case, the predefined value may be a positive integer including 0.

For example, when the absolute value of the motion vector y component of the current sub-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, when the absolute value of the motion vector y component of the current sub-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. In this case, the predefined value may be a positive integer including 0.

For example, when the sum of the absolute values of the x component and the y component of the motion vector is equal to or greater than 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, when the sum of the absolute values of the x component and the y component of the motion vector is less than a predefined value, a weighted sum may be calculated for samples located in one row/column adjacent to each block boundary. In this case, the predefined value may be a positive integer including 0.

23 is a diagram for explaining an embodiment in which a weighted sum of a first prediction block and a second prediction block is cumulatively calculated in a predetermined order during overlapping block motion compensation. The encoder and the decoder may calculate a weighted sum of the first prediction block and the second prediction block in a predetermined order.

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

As in the example of FIG. 23 , a weighted sum of the first prediction block and 1) the second prediction block generated using the motion information of the upper block may be calculated to generate a first weighted sum result block, and the generated first block may be generated. 1 weighted sum result block and 2) a weighted sum of the second prediction block generated using 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 ) A weighted sum of the second prediction block generated using the motion information of the lower block may be calculated to generate a third weighted sum block, and the generated third weighted sum result block and 4) motion information of the right block A weighted sum of the generated second prediction blocks may be calculated to generate a 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 from each other.

24 is a diagram for explaining an embodiment in which a weighted sum of a first prediction block and a second prediction block is calculated when overlapping block motion is compensated. In order to improve encoding efficiency, the weights of the second prediction blocks generated using at least one of the first prediction block, the upper block, the left block, the lower block, and the right block motion information are not accumulated when the weighted sum is calculated. The sum can be computed in any order.

In this case, the second prediction blocks generated using at least one of motion information of the upper block, the left block, the lower block, and the right block may have the same weight. Also, the weight used for the second prediction block and the weight used for the first prediction block may be the same.

Referring to FIG. 24 , a storage space may be allocated as much as the number of first prediction blocks and second prediction blocks, and a weighted sum may be calculated with the first prediction block with the same weight between the second prediction blocks when the final prediction block is generated. .

* Also, a weighted sum of the second prediction block and the first prediction block may be calculated using motion information of a sub-block at the corresponding position in the corresponding position image.

When the size of the current block is K samples or less, information on whether to perform overlapping block motion compensation for the current block may be entropy-encoded/decoded. In this case, K may be a positive integer, for example, 256.

In addition, when the size of the current block is greater than K samples or in a specific inter prediction mode (eg, merge mode or enhanced motion vector prediction mode), information on whether to perform overlapped block motion compensation on the current block is entropy-encoded. / It is possible to perform basically overlapping 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 region corresponding to the boundary of the current block. In this case, when the second prediction block is subtracted, a weighted sum of the second prediction block and the original signal may be calculated.

Enhanced Multiple Transform, which applies DCT (Discrete Cosine Transform)-based transforms and DST (Discrete Sine Transform)-based transforms to vertical/horizontal transforms, is not applied to the current block for which nested block motion compensation is not used. may not be That is, the enhanced multiple transform can be applied only to the current block in which the overlapped block motion compensation is used.

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

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

In addition, a second prediction block of at least one current sub-block may be generated by using motion information of at least one neighboring sub-block of the current sub-block (S2520). Here, 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.

Meanwhile, when the current sub-block is not included in the left boundary region and the upper boundary region of the current block, at least one second prediction 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, when the current sub-block is not included in the left boundary region and the upper boundary region of the current block, a second prediction block is generated using motion information included in at least one of a merge list and a motion vector list of the current block. can create

On the other hand, only when the current sub-block is included in at least one of a left boundary region and an upper boundary region of the current block, at least one second prediction block can be generated using motion information of at least one neighboring sub-block. have.

On the other hand, when the current sub-block is included in the left boundary region of the current block, at least one of the current sub-block using motion information of at least one of a left neighboring sub-block, an upper-left neighboring sub-block, and a lower-left neighboring sub-block generates a second prediction block of , and when the current sub-block is included in the upper boundary region of the current block, at least one of an upper neighboring sub-block, an upper left neighboring sub-block, and a lower right neighboring sub-block of the current sub-block At least one second prediction block may be generated using the motion information.

On the other hand, when the current sub-block is not included in the left boundary area and the upper boundary area of the current block, the upper neighboring sub-block, the left neighboring sub-block, the lower neighboring sub-block, the right neighboring sub-block, the upper left At least one second prediction block may be generated by using motion information of at least one of a neighboring sub-block, a lower-left neighboring sub-block, a lower-right neighboring sub-block, and an 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 piece of motion information.

Then, a final prediction block may be generated based on a 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 summing may be performed by applying different weights for each sample of the first prediction block and the second prediction block according to the positions of the neighboring sub-blocks used to generate the second prediction block.

Meanwhile, in the step of generating the final prediction block ( S2530 ), when there are a plurality of second prediction blocks of the current sub-block, a weighted sum between the first prediction block of the current block and the second prediction block of the current sub-block is performed. The final prediction block may be generated by summing them simultaneously.

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

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

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

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

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

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

The above embodiments of the present invention may be applied according to the size of at least one of a coding block, a prediction block, a transform block, a block, a current block, a coding unit, a prediction unit, a transform unit, a unit, and a current unit. Here, the size may be defined as a minimum size and/or a maximum size to which the embodiments are applied, or may be defined as a fixed size to which the embodiments are applied. Also, in the above embodiments, the first embodiment may be applied in the first size, and the second embodiment may be applied in the second size. That is, the regular embodiments may be complexly applied according to the size. In addition, the above embodiments of the present invention may be applied only when the minimum size or more and the maximum size or less. That is, the above embodiments may be applied only when the block size is included within a certain range.

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

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

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

A slice type to which the above embodiments of the present invention are applied is defined, and the above embodiments of the present invention can be applied according to the corresponding slice type.

In the above-described embodiments, the methods are described on the basis of a flowchart 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 concurrently with other steps as described above. can In addition, those of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive, other steps may be included, or that 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. It is not possible to describe every possible combination for representing the various aspects, but one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other substitutions, modifications and variations falling within the scope of the following claims.

The 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 in a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include hard disks, magnetic media such as floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, and magneto-optical media such as floppy disks. media), and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes 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 present invention, and vice versa.

In the above, the present invention has been described with specific matters such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , those of ordinary skill in the art to which the present invention pertains can make various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and not only the claims described below, but also all modifications equivalently or equivalently to the claims described below belong to the scope of the spirit of the present invention. will do it

Claims (19)

In the video decoding method,
generating a first prediction block and a second prediction block for the current block; and
generating a final prediction block for the current block by 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. According to claim 1,
The image decoding method, characterized in that 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. 3. The method of claim 2,
Further comprising the step of 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 by using a merge candidate indicated by the second merge index among candidates in the merge candidate list. According to claim 1,
The final prediction block for the current block is generated using a weighted sum of samples of the first prediction block and the samples of the second prediction block,
The image decoding method, characterized in that the weighted sum is applied only to a partial region of the current block. 5. The method of claim 4,
The partial area is an area corresponding to a boundary between two areas in the current block,
The image decoding method, characterized in that the weights of the weighted sum are determined based on the boundary. According to claim 1,
The current block includes a first area and a second area specified by triangulation for the current block,
The prediction values generated by the first prediction for the first prediction block include prediction values for the first region,
The prediction values generated by the second prediction of the second prediction block include prediction values of the second region. In the video encoding method,
generating a first prediction block and a second prediction block for the current block; and
Generating a final prediction block for the current block by 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,
and the second prediction block is generated by performing a second prediction on the current block. 8. The method of claim 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, the video encoding method . 9. The method of claim 8,
Further comprising the step of 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 candidates in the merge candidate list,
The information for generating the second prediction block is characterized in that it corresponds to a merge candidate indicated by the second merge index among candidates in the merge candidate list. 8. The method of claim 7,
The final prediction block for the current block is generated using a weighted sum of samples of the first prediction block and the samples of the second prediction block,
The image encoding method, characterized in that the weighted sum is applied only to a partial region of the current block. 8. The method of claim 7,
The partial area is an area corresponding to a boundary between two areas in the current block,
The image encoding method, characterized in that the weights of the weighted sum are determined based on the boundary. 11. The method of claim 10,
The current block includes a first area and a second area specified by triangulation for the current block,
The prediction values generated by the first prediction for the first prediction block include prediction values for the first region,
The prediction values generated by the second prediction of the second prediction block include prediction values of the second region. A computer-readable recording medium storing a bitstream generated by the video encoding method of claim 7. A computer-readable recording medium comprising a bitstream,
The bitstream is
Information about the prediction of the current block
including,
A first prediction block and a second prediction block for the current block are generated using the information about the prediction of the current block,
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 a second prediction on the current block. 15. The method of claim 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. 16. The method of claim 15,
Further comprising the step of 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 by using a merge candidate indicated by the second merge index among candidates in the merge candidate list. 15. The method of claim 14,
The final prediction block for the current block is generated using a weighted sum of samples of the first prediction block and the samples of the second prediction block,
The weighted sum is applied only to a partial region of the current block. 18. The method of claim 17,
The partial area is an area corresponding to a boundary between two areas in the current block,
The computer-readable recording medium, characterized in that the weights of the weighted sum are determined based on the boundary. 15. The method of claim 14,
The current block includes a first area and a second area specified by triangulation for the current block,
The prediction values generated by the first prediction for the first prediction block include prediction values for the first region,
The prediction values generated by the second prediction for the second prediction block include prediction values for the second region.

Images