KR20220136316A - Method and apparatus for prediction using reference block - Google Patents

Abstract

The present invention relates to a video decoding method and apparatus and a video encoding method and apparatus, wherein a prediction mode may be selected from among a plurality of prediction modes by using prediction mode information of a target block in video encoding and decoding, and based on the selected prediction mode, prediction of the target block may be performed. The prediction mode information may comprise information related to a reference block, and the reference block may comprise one or more among spatial neighbor blocks spatially adjacent to the target block and temporal neighbor blocks temporally adjacent to the target block. When the selected prediction mode is plural, a prediction mode to be used for prediction of a target block may be selected from among the plural selected prediction modes through signaling of prediction mode determination information.

Description

Prediction method and apparatus using reference blocks

The following embodiments relate to a video decoding method, a decoding apparatus, an encoding method, and an encoding apparatus, and to a method and apparatus for performing prediction using a reference block in encoding and decoding a video.

With the continuous development of the information and communication industry, a broadcasting service having a high definition (HD) resolution has spread worldwide. Through this proliferation, many users have become accustomed to high-resolution and high-definition images and/or videos.

In order to satisfy users' demand for high image quality, many organizations are spurring the development of next-generation imaging devices. User interest in High Definition TV (HDTV) and Full HD (FHD) TV, as well as Ultra High Definition (UHD) TV, which has a resolution four times higher than that of FHD TV has increased, and with this increase in interest, image encoding/decoding technology for an image having higher resolution and image quality is required.

An image encoding/decoding apparatus and method for encoding/decoding high-resolution and high-definition images, such as inter prediction technology, intra prediction technology, entropy encoding technology, etc. can be used The inter prediction technique may be a technique of predicting a value of a pixel included in a current picture using a temporally previous picture and/or a temporally later picture. The intra prediction technique may be a technique of predicting the value of a pixel included in the current picture by using information on the pixel in the current picture. The entropy encoding technique may be a technique of allocating a short code to a symbol having a high frequency of occurrence and a technique of assigning a long code to a symbol having a low frequency of occurrence.

Various prediction methods have been developed to improve the efficiency and accuracy of intra prediction and/or inter prediction. Efficiency of prediction may vary greatly depending on which prediction method among various applicable prediction methods is used for encoding and/or decoding of a block.

An embodiment may provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method for performing prediction using information about a reference block.

An embodiment may provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method for performing prediction using information about a spatial reference block and/or a temporal reference block.

In one aspect, comprising: a processing unit that selects a prediction mode from among a plurality of prediction modes using prediction mode information on the target block, and performs prediction on the target block based on the selected prediction mode, the prediction mode The information includes information related to a reference block, and the reference block includes at least one of a spatial neighboring block spatially adjacent to the target block and a temporal neighboring block temporally adjacent to the target block.

In another aspect, a processing unit that selects a prediction mode from among a plurality of prediction modes using prediction mode information on the target block, and performs prediction on the target block based on the selected prediction mode, wherein the prediction The mode information includes information related to a reference block, and the reference block includes at least one of a spatial neighboring block spatially adjacent to the target block and a temporal neighboring block temporally adjacent to the target block.

In another aspect, the method includes: selecting a prediction mode from among a plurality of prediction modes by using prediction mode information on a target block; and performing prediction on the target block based on the selected prediction mode, wherein the prediction mode information includes information related to a reference block, wherein the reference block includes a spatial neighboring block spatially adjacent to the target block and the A decoding method including one or more temporally neighboring blocks temporally adjacent to a target block is provided.

The selected prediction mode may be plural.

A prediction mode to be used for prediction of the target block among the plurality of selected prediction modes may be determined using the prediction mode determination information.

The decoding method may further include receiving a bitstream including the prediction mode determination information.

The prediction mode determination information may include one or more partial prediction mode determination information.

The selected prediction mode may be one or more.

According to the selected one or more prediction modes, at least a part of the one or more partial prediction mode determination information may be omitted in the signaling of the prediction mode determination information.

The prediction mode determination information may include a matching mode identifier.

When there are a plurality of the selected prediction modes, the matching mode identifier may indicate a prediction mode used for decoding the target block from among the plurality of selected prediction modes.

When the selected prediction mode is one, the prediction mode determination information may not include the matching mode identifier.

The prediction mode determination information may include a matching prediction identifier.

The matching prediction identifier may indicate whether the prediction mode is selected from among the plurality of prediction modes.

The information related to the reference block includes a motion vector of the reference block, a prediction direction of the reference block, a reference picture index of the reference block, an encoding mode of the reference block, a reference picture list of the reference block, and a picture order of the reference block. It may include at least one of a picture order count (POC), a quantization parameter (QP) of the reference block, and a coded block flag (CBF) of the reference block.

The plurality of prediction modes may include a template matching mode and a bilateral matching mode.

The reference block may be plural.

Motion vectors of the plurality of reference blocks may be derived, correlation of the derived motion vectors may be determined, and the prediction mode may be selected based on the correlation.

According to the comparison between the correlation and the threshold, one of a template matching mode and a bilateral matching mode may be selected as the prediction mode of the target block.

The prediction mode may be selected from among the plurality of prediction modes using a prediction direction.

The prediction direction may be a prediction direction of the target block or a prediction direction of the reference block.

The prediction mode may be selected according to whether the inter prediction of the target block is uni-prediction or bi-prediction.

If the inter prediction is bi-directional prediction, a bilateral matching mode may be selected from among the plurality of prediction modes.

When the inter prediction is unidirectional prediction, a template matching mode may be selected from among the plurality of prediction modes.

The prediction mode may be selected from among the plurality of prediction modes by using the coding parameter of the reference block.

It is determined whether the prediction mode of the reference block is an intra prediction mode or an inter prediction mode according to the coding parameter of the reference block, and a plurality of prediction modes according to which the prediction mode of the reference block is an intra prediction mode and an inter prediction mode Among them, the selected prediction mode may be determined.

The prediction mode may be selected from among the plurality of prediction modes based on a difference between the specified POCs.

An encoding apparatus, an encoding method, a decoding apparatus, and a decoding method for performing prediction by using information about a reference block are provided.

Provided are an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method for performing prediction using information about a spatial reference block and/or a temporal reference block.

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 illustrating a form of a prediction unit (PU) that a coding unit (CU) may include.
5 is a diagram illustrating a form of a transform unit (TU) that may be included in a coding unit (CU).
6 is a diagram for explaining an embodiment of an intra prediction process.
7 is a diagram for explaining a position of a reference sample used in an intra prediction process.
8 is a diagram for explaining an embodiment of an inter prediction process.
9 shows spatial candidates according to an example.
10 illustrates an order of adding motion information of spatial candidates to a merge list according to an example.
11 illustrates a process of transformation and quantization according to an example.
12 is a structural diagram of an encoding apparatus according to an embodiment.
13 is a structural diagram of a decoding apparatus according to an embodiment.
14 is a flowchart of a prediction method according to an embodiment.
15 is a flowchart of a prediction mode selection method according to an embodiment.
16 shows reference blocks according to an example.
17 illustrates signaling of prediction mode determination information when two prediction modes are selected according to an example.
18 illustrates signaling of prediction mode determination information when one prediction mode is selected according to an example.
19 illustrates signaling of prediction mode determination information when one prediction mode is selected according to an example.
20 illustrates prediction of a target block using a bilateral matching mode according to an example.
21 illustrates prediction of a target block using a template matching mode according to an example.
22 is a flowchart of a method of predicting a target block and a method of generating a bitstream according to an embodiment.

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 should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0014] 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 implemented 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 as claimed.

Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects. The shapes and sizes of elements in the drawings may be exaggerated for clearer description.

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 is referred to as being “connected” or “connected” to another component, the two components may be directly connected or connected to each other, but in the above 2 It should be understood that other components may exist in the middle of the components. When a component is referred to as being “directly connected” or “directly connected” to another component, it should be understood that there is no other component in the middle of the two components.

The 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 included by listing as individual components for convenience of description. As long as they can be implemented and integrated embodiments and separate embodiments of each of these components do not depart from the essence of the present invention, they are included in the scope of the present invention.

In addition, the description of "including" a specific configuration in exemplary embodiments does not exclude configurations other than the above specific configuration, and additional configurations are the implementation of the exemplary embodiments or the technical spirit of the exemplary embodiments. It means that it can be included in the scope.

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 "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the possibility of the presence 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 additional configurations may also be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Hereinafter, in order to enable those of ordinary skill in the art to easily implement the embodiments, embodiments will be described in detail with reference to the accompanying drawings. In describing the embodiments, 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 thereof will be omitted. In addition, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

Hereinafter, an image may mean one picture constituting a video, or may indicate a video itself. For example, "encoding and/or decoding of an image" may mean "encoding and/or decoding of a video", and may mean "encoding and/or decoding of one image among images constituting a video". may be

Hereinafter, the terms “video” and “motion picture” may be used interchangeably and may be used interchangeably.

Hereinafter, the target image may be an encoding target image to be encoded and/or a decoding target image to be decoded. In addition, the target image may be an input image input to the encoding apparatus or may be an input image input to the decoding apparatus.

Hereinafter, the terms “image”, “picture”, “frame” and “screen” may be used interchangeably and may be used interchangeably.

Hereinafter, the object block may be an encoding object block to be encoded and/or a decoding object block to be decoded. Also, the target block may be a current block that is a target of current encoding and/or decoding. For example, the terms "target block" and "current block" may be used interchangeably and may be used interchangeably.

Hereinafter, the terms “block” and “unit” may be used with the same meaning, and may be used interchangeably. Or “block” may indicate a specific unit.

Hereinafter, the terms “region” and “segment” may be used interchangeably.

Hereinafter, a specific signal may be a signal representing a specific block. For example, the original signal may be a signal representing the target block. A prediction signal may be a signal indicating a prediction block. The residual signal may be a signal indicating a residual block.

In embodiments, each of the specified information, data, flags and elements, attributes, etc. may have a value. A value "0" of information, data, flags and elements, attributes, etc. may represent logical false or a first predefined value. In other words, the value "0", false, logical false and the first predefined value may be used interchangeably. A value “1” of information, data, flags and elements, attributes, etc. may represent logical true or a second predefined value. In other words, the value “1”, true, logical true and the second predefined value may be used interchangeably.

When a variable such as i or j is used to indicate a row, column, or index, the value of i may be an integer of 0 or more, or an integer of 1 or more. That is, in embodiments, a row, column, index, etc. may be counted from 0, and may be counted from 1.

In the following, terms used in the embodiments are described.

Encoder: refers to a device that performs encoding.

Decoder: refers to a device that performs decoding.

Unit: A unit may indicate a unit of encoding and decoding of an image. The terms “unit” and “block” may be used interchangeably and may be used interchangeably.

- A unit may be an MxN array of samples. M and N may each be a positive integer. A unit can often mean an arrangement of two-dimensional samples.

- In image encoding and decoding, a unit may be an area generated by segmentation of one image. One image may be divided into a plurality of units. Alternatively, the unit may refer to the divided part when one image is divided into subdivided parts and encoding or decoding is performed on the divided part.

- In video encoding and decoding, a predefined process for the unit may be performed according to the type of the unit.

- According to the function, the type of unit is a macro unit, a coding unit (CU), a prediction unit (PU), a residual unit, and a transform unit (TU), etc. can be classified as Or, according to a function, a unit is a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding unit, a coding block, and a prediction 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), etc. may mean.

- A unit may refer to information including a luma component block, a chroma component block corresponding thereto, and a syntax element for each block in order to be distinguished from a block.

- The size and shape of the unit may vary. In addition, the units may have various sizes and various shapes. In particular, the shape of the unit may include not only a square, but also a geometric figure that can be expressed in two dimensions, such as a rectangle, 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.

- One unit can be further divided into sub-units having a smaller size compared to the unit.

Unit depth: The unit depth may mean the degree of division of a unit. Also, the unit depth may indicate a level at which a unit exists when the unit is expressed in a tree structure.

- The unit division information may include a unit depth with respect to the depth of the unit. Unit depth may indicate the number and/or degree to which a unit is divided.

- In the tree structure, the depth of the root node is the shallowest and the depth of the leaf node is the deepest.

- One unit may be hierarchically divided into a plurality of sub-units while having depth information based on a tree structure. In other words, a unit and a sub-unit generated by division of the unit may correspond to a node and a child node of the node, respectively. Each divided sub-unit may have a unit depth. Since the unit depth indicates the number and/or degree of division of the unit, the division information of the sub-unit may include information about the size of the sub-unit.

- In the tree structure, the highest node may correspond to the first undivided unit. The highest node may be referred to as a root node. Also, the highest node may have a minimum depth value. In this case, the highest node may have a depth of level 0.

- A node with a depth of level 1 may represent a unit created as the original unit is split once. A node with a depth of level 2 may represent a unit generated as the original unit is split twice.

- A node having a depth of level n may represent a unit generated as the original unit is divided n times.

- A leaf node may be the lowest node and may be a node that cannot be further divided. The depth of the leaf node may be the maximum level. For example, the predefined value of the maximum level may be three.

Sample: A sample may be a base unit constituting a block. A sample can be represented as values from 0 to 2 ^Bd- 1 depending on the bit depth (Bd).

- Samples can be pixels or pixel values.

- Hereinafter, the terms "pixel", "pixel" and "sample" may be used interchangeably and may be used interchangeably.

Coding Tree Unit (CTU): A CTU may be composed of one luminance component (Y) coding tree block and two chrominance component (Cb, Cr) coding tree blocks related to the luminance component coding tree block. have. In addition, the CTU may mean including the above blocks and a syntax element for each block of the above blocks.

- 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.

- CTU may be used as a term to refer to a pixel block, which is a processing unit in the decoding and encoding process of an image, as in segmentation of an input image.

Coding tree block (CTB): The 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: It means a block adjacent to the target block. A block adjacent to the target block may mean a block having a boundary contacting the target block or a block located within a predetermined distance from the target block. The neighboring block may mean a block adjacent to the vertex of the target block. Here, the block adjacent to the vertex of the target block may be a block vertically adjacent to a neighboring block horizontally adjacent to the target block or a block horizontally adjacent to a neighboring block vertically adjacent to the target block. The neighboring block may mean a reconstructed neighboring block.

Prediction unit: may mean a base unit for prediction, such as inter prediction, intra prediction, inter compensation, intra compensation, and motion compensation.

- One prediction unit may be divided into a plurality of partitions having a smaller size or sub-prediction units. A plurality of partitions may also be a basis unit in performing prediction or compensation. A partition generated by division of a prediction unit may also be a prediction unit.

Prediction unit partition: It may mean a form in which a prediction unit is divided.

Reconstructed neighboring unit: A reconstructed neighboring unit may be a previously decrypted and reconstructed unit in the vicinity of the target unit.

- The reconstructed neighboring unit may be a spatial neighboring unit or a temporal neighboring unit for the target unit.

- The reconstructed spatial neighboring unit may be a unit within the current picture and already reconstructed through encoding and/or decoding.

- The reconstructed temporal neighboring unit may be a unit within the reference image and already reconstructed through encoding and/or decoding. The location of the reconstructed temporal neighboring unit in the reference image may be the same as the location of the target unit in the current picture or may correspond to the location of the target unit in the current picture.

Parameter set: The parameter set may correspond to header information among structures in the bitstream. For example, the parameter set may include a sequence parameter set, a picture parameter set, an adaptation parameter set, and the like.

Rate-distortion optimization: The encoding apparatus uses a combination of a size of a coding unit, a prediction mode, a size of a prediction unit, motion information, and a size of a transform unit to provide high encoding efficiency. Distortion optimization can be used.

- The rate-distortion optimization method may calculate a rate-distortion cost of each combination in order to select an optimal combination from among the above combinations. The rate-distortion cost can be calculated using Equation 1 below. In general, the combination in which the rate-distortion cost is minimized may be selected as the optimal combination in the rate-distortion optimization method.

[Formula 1]

- D may indicate distortion. D may be the mean square error of difference values between the original transform coefficients and the reconstructed transform coefficients within the transform unit.

- R can represent the rate. R may represent a bit rate using related context information.

- λ may represent a Lagrangian multiplier. R may include not only coding parameter information such as prediction mode, motion information, and a coded block flag, but also bits generated by encoding of transform coefficients.

- The encoding apparatus may perform processes such as inter prediction and/or intra prediction, transformation, quantization, entropy encoding, inverse quantization, and inverse transformation in order to accurately calculate D and R. These processes may greatly increase the complexity of the encoding apparatus.

Bitstream: A bitstream may mean a string of bits including encoded image information.

Parameter set: The parameter set may correspond to header information among structures in the bitstream.

- The parameter set may include at least one of a video parameter set, a sequence parameter set, a picture parameter set, and an adaptation parameter set. In addition, the parameter set may include information of a slice header and information of a tile header.

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

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

Reference picture: A reference picture may mean an image referenced by a unit for inter prediction or motion compensation. Alternatively, the reference picture may be an image including the reference unit referenced by the target unit for inter prediction or motion compensation.

Hereinafter, the terms “reference picture” and “reference image” may be used with the same meaning, and may be used interchangeably.

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

- The types of reference picture lists are List Combined (LC), List 0 (List 0; L0), List 1 (List 1; L1), List 2 (List 2; L2), and List 3 (List 3; L3). ), and so on.

- One or more reference picture lists may be used for inter prediction.

Inter prediction indicator: The inter prediction indicator may indicate a direction of inter prediction of a target unit. Inter prediction may be one of unidirectional prediction and bidirectional prediction. Alternatively, the inter prediction indicator may indicate the number of reference images used when generating a prediction unit of a target unit. Alternatively, the inter prediction indicator may mean the number of prediction blocks used for inter prediction or motion compensation for a target unit.

Reference picture index: The reference picture index may be an index indicating a specific reference picture in the reference picture list.

Motion Vector (MV): A motion vector may be a two-dimensional vector used in inter prediction or motion compensation. The motion vector may mean an offset between the encoding target image/decoding target image and the reference image.

- For example, MV can be expressed in the form (mv _x , mv _y ). mv _x may represent a horizontal component, and mv _y may represent a vertical component.

Search range: The search range may be a two-dimensional area in which an MV is searched during inter prediction. For example, the size of the search area may be MxN. M and N may each be a positive integer.

Motion vector candidate: The motion vector candidate may mean a block that is a prediction candidate or a motion vector of a block that is a prediction candidate when a motion vector is predicted.

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

Motion vector candidate list: The motion vector candidate list may refer to a list constructed using one or more motion vector candidates.

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

Motion information: Motion information includes motion vectors, reference picture indexes and inter prediction indicators, as well as reference picture list information, reference pictures, motion vector candidates, motion vector candidate indexes, merge candidates and merge indexes, etc. It may mean information including at least one of

Merge candidate list: The merge candidate list may refer 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 picture index for each list, and a motion vector.

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

- The merge index may indicate a reconstructed unit that derived a merge candidate among reconstructed units spatially adjacent to the target unit and reconstructed units temporally adjacent to the target unit.

- The merge index may indicate at least one of motion information of a merge candidate.

Transform unit: A transform unit may be a basic unit in residual signal encoding and/or residual signal decoding, such as transform, inverse transform, quantization, inverse quantization, transform coefficient encoding, and transform coefficient decoding. One transform unit may be divided into a plurality of transform units having a smaller size.

Scaling: Scaling may refer to a process of multiplying a transform coefficient level by a factor.

- As a result of scaling to the transform coefficient level, a transform coefficient may be generated. Scaling may be referred to as dequantization.

Quantization Parameter (QP): A 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 the transform coefficient level in inverse quantization. Alternatively, the quantization parameter may be a value mapped to a quantization step size.

Delta quantization parameter: The delta quantization parameter refers to a differential value between a predicted quantization parameter and a quantization parameter of a unit to be encoded/decoded.

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

Transform coefficient: The transform coefficient may be a coefficient value generated as the encoding apparatus performs transformation. Alternatively, the transform coefficient may be a coefficient value generated by performing at least one of entropy decoding and inverse quantization in the decoding apparatus.

- A transform coefficient or a quantized level to which quantization is applied to a residual signal or a quantized transform coefficient level may also be included in the meaning of the transform coefficient.

Quantized level: A quantized level may mean a value generated by performing quantization on a transform coefficient or a residual signal in an encoding apparatus. Alternatively, the quantized level may mean a value that is a target of inverse quantization when the decoding apparatus performs inverse quantization.

- 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: The non-zero transform coefficient may mean a transform coefficient having a non-zero value or a transform coefficient level having a non-zero value. Alternatively, the non-zero transform coefficient may mean a transform coefficient having a non-zero value or a transform coefficient level having a non-zero value.

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

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

Default matrix: The default matrix may be a quantization matrix predefined in the encoding apparatus and the decoding apparatus.

Non-default matrix: The non-default matrix may be a quantization matrix that is not predefined in the encoding apparatus and the decoding apparatus. The non-default matrix may be signaled from the encoding apparatus to the decoding apparatus.

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 of a video.

Referring to FIG. 1 , the encoding apparatus 100 includes an inter prediction unit 110 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , a transform unit 130 , a quantization unit 140 , and entropy encoding. It may include a unit 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 the target image by using the intra mode and/or the inter mode.

Also, the encoding apparatus 100 may generate a bitstream including encoding information through encoding of the target image, and may output the generated bitstream. The generated bitstream may be stored in a computer-readable recording medium, and may be streamed through a wired/wireless transmission medium.

As the prediction mode, when the intra mode is used, the switch 115 may be switched to the intra mode. As the prediction mode, when the inter mode is used, the switch 115 may be switched to the inter mode.

The encoding apparatus 100 may generate a prediction block for the target block. Also, after the prediction block is generated, the encoding apparatus 100 may encode a residual between the target block and the prediction block.

When the prediction mode is the intra mode, the intra prediction unit 120 may use pixels of an already encoded/decoded block adjacent to the target block as reference samples. The intra prediction unit 120 may perform spatial prediction on the object block by using the reference sample, and may generate prediction samples for the object block through spatial prediction.

The inter prediction unit 110 may include a motion prediction unit and a motion compensator.

When the prediction mode is the inter mode, the motion prediction unit may search for a region that best matches the target block from the reference image in the motion prediction process, and derive a motion vector for the target block and the searched region using the searched region. can do.

The reference picture may be stored in the reference picture buffer 190 , and may be stored in the reference picture buffer 190 when encoding and/or decoding of the reference picture is processed.

The motion compensator may generate a prediction block for the target block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional vector used for inter prediction. Also, the motion vector may indicate an offset between the target image and the reference image.

When the motion vector has a non-integer value, the motion predictor and the motion compensator 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, a method of motion prediction and motion compensation of a PU included in a CU based on the CU is a skip mode, a merge mode, and an advanced motion vector prediction (advanced motion vector). prediction; AMVP) mode and the current picture reference mode may be determined, and inter prediction or motion compensation may be performed according to each mode.

The subtractor 125 may generate a residual block that is a difference between the target 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 for each block.

The transform unit 130 may perform transform on the residual block to generate a transform coefficient, and may output the generated 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 omit transform on the residual block.

A quantized transform coefficient level or a quantized level may be generated by applying quantization to the transform coefficients. Hereinafter, in embodiments, a quantized transform coefficient level and a quantized level may also be referred to as transform coefficients.

The quantizer 140 may generate a quantized transform coefficient level or a quantized level by quantizing the transform coefficient according to the quantization parameter. The quantization unit 140 may output the generated quantized transform coefficient level or the generated 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 based on the values calculated by the quantization unit 140 and/or coding parameter values calculated during the encoding process. . The entropy encoder 150 may output the generated 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.

The coding parameter may be information required for encoding and/or decoding. The coding parameter may include information encoded by the encoding apparatus 100 and transmitted from the encoding apparatus 100 to the decoding apparatus, and may include information that can be inferred during encoding or decoding. For example, as information transmitted to the decoding device, there is a syntax element.

For example, the coding parameters may include a prediction mode, a motion vector, a reference picture index, a coding block pattern, the presence or absence of a residual signal, a transform coefficient, a quantized transform coefficient, a quantization parameter, a block size, and a block partition. ) may include values or statistics such as information. The prediction mode may refer to an intra prediction mode or an inter prediction mode.

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

When entropy encoding is applied, a small number of bits may be allocated to a symbol having a high occurrence probability, and a large number of bits may be allocated to a symbol having a low occurrence probability. As a symbol is expressed through this allocation, the size of a bitstring for symbols to be encoded may be reduced. Accordingly, compression performance of image encoding may be improved through entropy encoding.

In addition, the entropy encoding unit 150 performs exponential golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (Context-Adaptive Binary) for entropy encoding. A coding method such as Arithmetic Coding (CABAC) may be used. For example, the entropy encoding unit 150 may perform entropy encoding using a Variable Length Coding/Code (VLC) table. For example, the entropy encoder 150 may derive a binarization method for a target symbol. Also, the entropy encoder 150 may derive a probability model of a target symbol/bin. The entropy encoder 150 may perform arithmetic encoding using the derived binarization method, a probability model, and a context model.

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

A coding parameter may include information (or flags, indexes, etc.) encoded by the encoding device and signaled from the encoding device to the decoding device, such as syntax elements, as well as information derived from the encoding process or decoding process. have. Also, the coding parameter may include information required for encoding or decoding an image. For example, the size of the unit/block, the depth of the unit/block, the division information of the unit/block, the division structure of the unit/block, information indicating whether the unit/block is divided in the form of a quad tree, the unit/block is binary Information indicating whether the tree is split in the form of a tree, the split direction of the binary tree (horizontal or vertical), the split form of the binary tree (symmetric split or asymmetric split), the prediction method (intra-prediction or inter-prediction), intra prediction Mode/direction, reference sample filtering method, prediction block filtering method, prediction block boundary filtering method, filter tap of filtering, filter coefficient of filtering, inter prediction mode, motion information, motion vector, reference picture index, inter prediction direction, inter prediction Indicator, reference picture list, reference picture, motion vector predictor, motion vector prediction candidate, motion vector candidate list, information indicating whether to use merge mode, merge candidate, merge candidate list, whether to use skip mode Information indicating, type of interpolation filter, filter tab of interpolation filter, filter coefficients of interpolation filter, motion vector size, motion vector expression accuracy, transform type, transform size, information indicating whether to use first-order transform, add (second-order) ) information indicating whether to use transformation, primary transformation index, secondary transformation index, information indicating the presence or absence of a residual signal, coded block pattern, coded block flag, quantization parameter , quantization matrix, information about intra-loop filter, information on whether to apply intra-loop filter, coefficients of intra-loop filter, filter tap of intra-loop, shape/form of intra-loop filter ), information indicating whether to apply a deblocking filter, deblocking filter coefficients, deblocking filter tap, deblocking filter strength, deblocking filter shape/shape, information indicating whether to apply an adaptive sample offset, adaptive samples Offset value, adaptive sample offset category, adaptive Sample offset type, whether to apply adaptive in-loop filter, adaptive in-loop filter coefficients, adaptive in-loop filter tap, adaptive in-loop filter shape/shape, binarization/inverse binarization method, context model, context model determination method, context model update method, whether to perform regular mode, whether to perform bypass mode, context bin, bypass bin, transform coefficient, transform coefficient level, transform coefficient level scanning method, At least one of image display/output order, slice identification information, slice type, slice division information, tile identification information, tile type, tile division information, picture type, bit depth, information about a luminance signal, and information about a chrominance signal A value or a combined form may be included in the coding parameter.

Here, the signaling of the flag or index means that the encoding apparatus 100 performs entropy encoding on the flag or index to generate an entropy-encoded flag or entropy-encoded index in a bitstream. It may mean to include, and the decoding apparatus 200 performs entropy decoding on the entropy-coded flag or entropy-encoded index extracted from the bitstream, so that it may mean acquiring the flag or index. .

Since encoding through inter prediction is performed by the encoding apparatus 100 , the encoded target image may be used as a reference image for other image(s) to be processed later. Accordingly, the encoding apparatus 100 may reconstruct or decode the encoded target image and store the reconstructed or decoded image as a reference image in the reference picture buffer 190 . Inverse quantization and inverse transformation of the encoded target image for decoding may be processed.

The quantized level may be inversely quantized by the inverse quantization unit 160 and may be inversely transformed by 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 may mean a coefficient on which at least one of dequantization and inverse-transformation has been performed, and may mean a reconstructed residual block.

The reconstructed block may pass through the filter unit 180 . The filter unit 180 reconstructs at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) into a reconstructed block or reconstructed It can be applied to pictures. The filter unit 180 may be referred to as an in-loop filter.

The deblocking filter may remove block distortion occurring at the boundary between blocks. In order to determine whether to apply the deblocking filter, whether to apply the deblocking filter to the target block may be determined based on pixel(s) included in several columns or rows included in the block. When the deblocking filter is applied to the target block, the applied filter may vary depending on the required strength of the deblocking filtering. That is, a filter determined according to the strength of deblocking filtering among different filters may be applied to the target block.

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

The ALF may perform filtering based on a comparison value between the reconstructed image and the original image. After dividing the pixels included in the image into predetermined groups, a filter to be applied to the divided group may be determined, and filtering may be performed differentially for each group. Information related to whether to apply the adaptive loop filter may be signaled for each CU. , the shape of the ALF applied to each block and the filter coefficients may be different for each block.

The reconstructed block or reconstructed image passing through the filter unit 180 may be stored in the reference picture buffer 190 . The reconstructed block passing through the filter unit 180 may be a part of the reference picture. In other words, the reference picture may be a reconstructed picture composed of reconstructed blocks that have passed through the filter unit 180 . The stored reference picture may be used for inter prediction later.

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 , an inter prediction unit 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, and may receive a bitstream streamed through a wired/wireless transmission medium.

The decoding apparatus 200 may perform intra-mode and/or inter-mode decoding on the bitstream. Also, the decoding apparatus 200 may generate a reconstructed image or a decoded image through decoding, and may output the generated reconstructed image or a decoded image.

For example, switching to an intra mode or an inter mode according to a prediction mode used for decoding may be performed by a switch. 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 entropy decoding unit 210 may generate symbols by performing entropy decoding on the bitstream based on the probability distribution of the bitstream. The generated symbols may include a symbol in the form of a quantized level. Here, the entropy decoding method may be similar to the entropy encoding method described above. For example, the entropy decoding method may be a reverse process of the above-described entropy encoding method.

The quantized coefficient may be inverse quantized by the inverse quantizer 220 . The inverse quantizer 220 may generate an inverse quantized coefficient by performing inverse quantization on the quantized coefficient. Also, the inverse quantized coefficient may be inversely transformed by the inverse transform unit 230 . The inverse transform unit 230 may generate a reconstructed residual block by performing inverse transform on the inverse quantized coefficients. As a result of performing inverse quantization and inverse transformation on the quantized coefficients, a reconstructed residual block may be generated. In this case, the inverse quantization unit 220 may apply a quantization matrix to the quantized coefficients in generating the reconstructed residual block.

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 target block.

The inter prediction unit 250 may include a motion compensator. Alternatively, the inter prediction unit 250 may be referred to as a motion compensator.

When the inter mode is used, the motion compensator 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 has a non-integer value, the motion compensator may apply an interpolation filter to a partial region in the reference image, and may generate a prediction block using the reference image to which the interpolation filter is applied. The motion compensator may determine which mode is a skip mode, a merge mode, an AMVP mode, and a current picture reference mode as a motion compensation method used for a PU included in a CU based on the CU to perform motion compensation, and the determined mode motion compensation may be performed accordingly.

The reconstructed residual block and the prediction block may be added through an adder 255 . The adder 255 may generate a reconstructed block by adding the reconstructed residual block and the prediction block.

The reconstructed block may pass through the filter unit 260 . The filter unit 260 may apply at least one of the deblocking filter, SAO, and ALF to the reconstructed block or the reconstructed picture.

The reconstructed block passing through the filter unit 260 may be stored in the reference picture buffer 270 . The reconstructed block passing through the filter unit 260 may be a part of the reference picture. In other words, the reference image may be an image composed of blocks reconstructed through the filter unit 260 . The stored reference image may then be used for inter prediction.

FIG. 3 is a diagram schematically illustrating a split structure of an image when encoding and decoding an image.

3 may schematically show an example 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. A unit may be a term that collectively refers to 1) a block including image samples and 2) a syntax element. For example, "division of a unit" may mean "division of a block corresponding to a unit".

A CU may be used as a base unit for image encoding/decoding. In addition, the CU may be used as a unit to which a selected one of an intra mode and an inter mode is applied in image encoding/decoding. That is, in image encoding/decoding, it may be determined which mode among the intra mode and the inter mode is applied to each CU.

Also, a CU may be a base unit in prediction, transformation, quantization, inverse transformation, inverse quantization, and encoding/decoding of transform coefficients.

Referring to FIG. 3 , an image 300 may be sequentially divided in units of a Largest Coding Unit (LCU), and the division structure of the image 300 may be determined according to the LCU. 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 depth information regarding 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 into lower units 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. Depth information may be stored for each CU. Each CU may have depth information.

The partition structure may mean a distribution of CUs for efficiently encoding an image in the LCU 310 . Such a distribution may be determined according to whether one CU is divided into a plurality of CUs. The number of partitioned CUs may be a positive integer of 2 or more including 2, 3, 4, 8 and 16, and the like. The horizontal size and vertical size of a CU generated by division may be smaller than the horizontal size and vertical size of a CU before division, depending on the number of CUs generated by division.

A divided CU may be recursively divided into a plurality of CUs in the same manner. By the recursive division, at least one of a horizontal size and a vertical size of the divided CU may be reduced compared to at least one of a horizontal size and a vertical size of the CU before division.

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 CU having the largest coding unit size as described above, and the SCU may be a CU having the smallest coding unit size.

The division may start from the LCU 310, and whenever the horizontal size and/or the vertical size of the CU is reduced by the division, the depth of the CU may increase by one.

For example, for each depth, an undivided CU may have a size of 2Nx2N. In addition, in the case of a divided CU, a CU having a size of 2Nx2N may be divided into four CUs having a size of NxN. The size of N can be halved for each increase in depth by 1.

Referring to FIG. 3 , an LCU having a depth of 0 may be 64×64 pixels or a 64×64 block. 0 may be the minimum depth. An SCU of depth 3 may be 8x8 pixels or an 8x8 block. 3 may be the maximum depth. In this case, a CU of a 64x64 block that is an LCU may be expressed as depth 0. A CU of a 32x32 block may be expressed as depth 1. A CU of a 16x16 block may be expressed as depth 2. A CU of an 8x8 block, which is an SCU, may be expressed as depth 3.

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, the value of the partition information of a CU that is not split may be 0, and the value of the partition information of the CU to be split may be 1.

For example, when one CU is divided into 4 CUs, the horizontal size and vertical size of each CU of the 4 CUs generated by division are half the horizontal size and half the vertical size of the CU before division, respectively. can When a CU of size 32x32 is divided into 4 CUs, the sizes of the divided 4 CUs may be 16x16. When one CU is divided into 4 CUs, it can be said that the CU is divided in a quad-tree form.

For example, when one CU is divided into two CUs, the horizontal size or vertical size of each CU of the two CUs generated by the division is half the horizontal size or half the vertical size of the CU before division, respectively. can When a CU having a size of 32x32 is vertically split into two CUs, the sizes of the split two CUs may be 16x32. When one CU is split into two CUs, it can be said that the CU is split in a binary-tree form.

In addition to the quad-tree type division and binary-tree type division, the LCU 310 may be applied.

4 is a diagram illustrating a form of a prediction unit (PU) that a coding unit (CU) may include.

A CU that is no longer split among CUs split from an LCU may be split into one or more prediction units (PUs).

A PU may be a base unit for prediction. The PU may be encoded and decoded in any one of a skip mode, an inter mode, and an intra mode. The PU may be divided into various forms according to each mode. For example, the target block described above with reference to FIG. 1 and the target block described above with reference to FIG. 2 may be PU.

In skip mode, there may be no partitions within a CU. In the skip mode, the 2Nx2N mode 410 in which PU and CU sizes are the same may be supported without division.

In the inter mode, 8 types of divided types within a CU may be supported. For example, in the inter mode, 2Nx2N mode 410, 2NxN mode 415, Nx2N mode 420, NxN mode 425, 2NxnU mode 430, 2NxnD mode 435, nLx2N mode 440 and nRx2N mode. Mode 445 may be supported.

In the intra mode, the 2Nx2N mode 410 and the NxN mode 425, and the 2NxN mode and Nx2N mode may be supported.

In the 2Nx2N mode 410, a PU having a size of 2Nx2N may be encoded. A PU having a size of 2Nx2N may mean a PU having the same size as the size of a CU. For example, a PU having a size of 2Nx2N may have a size of 64x64, 32x32, 16x16, or 8x8.

In the NxN mode 425 , a PU having a size of NxN may be encoded.

For example, in intra prediction, when the size of a PU is 8x8, four divided PUs may be coded. The size of the divided PU may be 4x4.

When a PU is encoded by an intra mode, the PU may be encoded using one intra prediction mode among a plurality of intra prediction modes. For example, a High Efficiency Video Coding (HEVC) technique may provide 35 intra prediction modes, and a PU may be encoded in one intra prediction mode among 35 intra prediction modes.

Whether the PU is encoded by the 2Nx2N mode 410 or the NxN mode 425 may be determined by rate-distortion cost.

The encoding apparatus 100 may perform an encoding operation on a PU having a size of 2Nx2N. Here, the encoding operation may be encoding the PU using each of a plurality of intra prediction modes that the encoding apparatus 100 can use. An optimal intra prediction mode for a PU having a size of 2Nx2N may be derived through an encoding operation. The optimal intra prediction mode may be an intra prediction mode that generates a minimum rate-distortion cost for encoding a PU having a size of 2Nx2N among a plurality of intra prediction modes that can be used by the encoding apparatus 100 .

Also, the encoding apparatus 100 may sequentially perform an encoding operation on each PU of the PUs divided into NxN. Here, the encoding operation may be encoding the PU using each of a plurality of intra prediction modes that the encoding apparatus 100 can use. An optimal intra prediction mode for a PU having an NxN size may be derived through an encoding operation. The optimal intra-prediction mode may be an intra-prediction mode that generates a minimum rate-distortion cost for encoding an NxN-sized PU among a plurality of intra prediction modes that can be used by the encoding apparatus 100 .

5 is a diagram illustrating a form of a transform unit (TU) that may be included in a coding unit (CU).

A transform unit (TU) may be a base unit used for processes of transform, quantization, inverse transform, inverse quantization, entropy encoding, and entropy decoding within a CU. A TU may have a square shape or a rectangular shape.

Among CUs split from an LCU, a CU that is no longer split into CUs may be split into one or more TUs. In this case, the partition structure of the TU may be a quad-tree structure. For example, as shown in FIG. 5 , one CU 510 may be divided one or more times according to a quad-tree structure. Through division, one CU 510 may be composed of TUs of various sizes.

In the encoding apparatus 100 , a 64x64 coding tree unit (CTU) may be divided into a plurality of smaller CUs by a recursive quad-tree structure. One CU may be divided into 4 CUs having the same sizes. CUs may be recursively partitioned, and each CU may have a quad tree structure.

A CU may have depth. When a CU is split, CUs generated by splitting may have a depth increased by 1 from the depth of the split CU.

For example, the depth of the CU may have a value of 0 to 3. The size of the CU may range from 64x64 to 8x8 according to the depth of the CU.

Through recursive segmentation for CUs, an optimal segmentation method that produces the minimum rate-distortion ratio can be selected.

6 is a diagram for explaining an embodiment of an intra prediction process.

Arrows outward from the center of the graph of FIG. 6 may indicate prediction directions of intra prediction modes. Also, a number indicated adjacent to the arrow may indicate an example of an intra prediction mode or a mode value assigned to a prediction direction of the intra prediction mode.

Intra encoding and/or decoding may be performed using reference samples of units adjacent to the target block. The neighboring blocks may be neighboring reconstructed blocks. For example, intra encoding and/or decoding may be performed using a value or a coding parameter of a reference sample included in a neighboring reconstructed block.

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

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

The unit of the prediction block may be the size of at least one of CU, PU, and TU. The prediction block may have a square shape having a size of 2Nx2N or NxN. The size of NxN may include 4x4, 8x8, 16x16, 32x32 and 64x64.

Alternatively, the prediction block may be a rectangular block having an MxN size such as 2x8, 4x8, 2x16, 4x16, and 8x16.

Intra prediction may be performed according to an intra prediction mode for the target block. The number of intra prediction modes that the target block can have may be a predefined fixed value, or a value determined differently according to the properties of the prediction block. For example, the properties of the prediction block may include the size of the prediction block and the type of the prediction block.

For example, the number of intra prediction modes may be fixed to 35 regardless of the size of the prediction block. Or, for example, the number of intra prediction modes may be 3, 5, 9, 17, 34, 35, or 36.

The intra prediction mode may be a non-directional mode or a directional mode. For example, the intra prediction mode may include two non-directional modes and 33 directional modes as shown in FIG. 6 .

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

The directional modes may be prediction modes having a specific direction or a specific angular angle. Modes other than the DC mode and the planar mode among the plurality of intra prediction modes may be a directional mode.

The intra prediction mode may be expressed by at least one of a mode number, a mode value, a mode number, and a mode angle. The number of intra prediction modes may be M. M may be 1 or more. In other words, the intra prediction modes may be M including the number of non-directional modes and the number of directional modes.

The number of intra prediction modes may be fixed to M regardless of the size of the block. Alternatively, the number of intra prediction modes may be different according to a size of a block and/or a type of a color component. For example, the number of prediction modes may be different depending on whether the color component is a luma signal or a chroma signal. For example, as the size of the block increases, the number of intra prediction modes may increase. Alternatively, the number of intra prediction modes of the luma component block may be greater than the number of intra prediction modes of the chrominance component block.

For example, in the case of a vertical mode having a mode value of 26, prediction may be performed in a vertical direction based on a pixel value of a reference sample.

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

The intra prediction mode located to the right of the vertical mode may be referred to as a vertical-right mode. The intra prediction mode located at the bottom of the horizontal mode may be called a horizontal-below mode. For example, in FIG. 6 , intra prediction modes whose mode value is one of 27, 28, 29, 30, 31, 32, 33, and 34 may be vertical right modes 613 . Intra prediction modes with a mode value of one of 2, 3, 4, 5, 6, 7, 8, and 9 may be horizontal bottom modes 616 .

The number of intra prediction modes and the mode value of each intra prediction mode described above may be merely exemplary. The number of the above-described intra prediction modes and a mode value of each intra prediction mode may be defined differently according to an embodiment, implementation, and/or need.

In order to perform intra prediction on the target block, an operation of checking whether samples included in the reconstructed neighboring block can be used as reference samples of the target block may be performed. If there is a sample that cannot be used as a reference sample of the current block among the samples of the neighboring block, a value generated by copying and/or interpolation using at least one sample value among samples included in the reconstructed neighboring block is It can be replaced with a sample value of a sample that is not available as a reference sample. When the values generated by copying and/or interpolation are replaced with sample values of samples, the samples can be used as reference samples of the target block.

During intra prediction, a filter may be applied to at least one of a reference sample and a prediction sample based on at least one of an intra prediction mode and a size of a target block.

When the intra prediction mode is the planar mode, in generating the prediction block of the target block, the upper reference sample of the target sample, the left reference sample of the target sample, and the upper right reference sample of the target block according to the location of the prediction target sample in the prediction block and a weight-sum of the lower left reference sample of the target block may be used to generate a sample value of the prediction target sample.

When the intra prediction mode is the DC mode, an average value of upper reference samples and left reference samples of the object block may be used in generating the prediction block of the object block.

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

Interpolation in real units may be performed to generate the above-described prediction samples.

The intra prediction mode of the target block may be predicted from intra prediction of a neighboring block of the target block, and information used for prediction may be entropy-encoded/decoded.

For example, if the intra prediction modes of the object block and the neighboring block are the same, it may be signaled that the intra prediction modes of the object block and the neighboring block are the same by using a predefined flag.

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

If the intra prediction modes of the target block and the neighboring block are different from each other, information on the intra prediction mode of the target block may be entropy encoded/decoded based on the intra prediction mode of the neighboring block.

7 is a diagram for explaining a position of a reference sample used in an intra prediction process.

7 illustrates a position of a reference sample used for intra prediction of a target block. Referring to FIG. 7 , the reconstructed reference samples used for intra prediction of a target block are lower-left reference samples 731 , left reference samples 733 , and upper-left reference samples 733 , left) a corner reference sample 735 , above reference samples 737 , and above-right reference samples 739 , and the like.

For example, the left reference samples 733 may mean a reconstructed reference pixel adjacent to the left side of the target block. The upper reference samples 737 may refer to reconstructed reference pixels adjacent to the upper end of the target block. The upper left corner reference sample 735 may mean a reconstructed reference pixel located in the upper left corner of the target block. Also, the lower left reference samples 731 may refer to reference samples located at the lower end of the left sample line among samples located on the same line as the left sample line composed of the left reference samples 733 . The upper right reference samples 739 may refer to reference samples located to the right of the upper pixel line among samples located on the same line as the upper sample line composed of the upper reference samples 737 .

When the size of the target block is NxN, the number of lower left reference samples 731 , left reference samples 733 , upper reference samples 737 , and upper right reference samples 739 may each be N.

A prediction block may be generated through intra prediction of the target block. Generation of the prediction block may include determining values of pixels of the prediction block. The size of the target block and the prediction block may be the same.

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

For example, when the intra prediction mode of the target block is a vertical mode having a mode value of 26, upper reference samples 737 may be used for intra prediction. When the intra prediction mode is the vertical mode, the value of the pixel of the prediction block may be the value of the reference sample positioned vertically above the pixel position. Accordingly, the top reference samples 737 adjacent to the top of the target block may be used for intra prediction. Also, the values of pixels in one row of the prediction block may be the same as the values of the upper reference samples 737 .

For example, when the mode value of the intra prediction mode of the target block is 18, at least some of the left reference samples 733, the upper left corner reference sample 735, and at least some of the upper reference samples 737. can be used When the mode value of the intra prediction mode is 18, the value of the pixel of the prediction block may be the value of the reference sample located at the upper left side diagonally with respect to the pixel.

The reference sample used to determine the pixel value of one pixel of the prediction block may be one, or may be two or more.

As described above, the pixel value of the pixel of the prediction block may be determined according to the position of the pixel and the position of the reference sample indicated by the direction of the intra prediction mode. When the position of the reference sample pointed to by the position of the pixel and the direction of the intra prediction mode is an integer position, the value of one reference sample pointed to by the integer position may be used to determine the pixel value of the pixel of the prediction block.

When the position of the reference sample indicated by the position of the pixel and the direction of the intra prediction mode is not an integer position, an interpolated reference sample may be generated based on the two reference samples closest to the position of the reference sample. have. The values of the interpolated reference samples may be used to determine the pixel values of the pixels of the prediction block. In other words, when the position of the pixel of the prediction block and the position of the reference sample pointed to by the direction of the intra prediction mode indicate between two reference samples, an interpolated value will be generated based on the values of the two samples. can

A prediction block generated by prediction may not be the same as the original target block. That is, a prediction error that is a difference between the target block and the prediction block may exist, and a prediction error may also exist between a pixel of the target block and a pixel of the prediction block.

Hereinafter, the terms “difference”, “error” and “residual” may be used with the same meaning, and may be used interchangeably.

For example, in the case of directional intra prediction, a larger prediction error may occur as a distance between a pixel of a prediction block and a reference sample is greater. Discontinuity may occur between the prediction block and neighboring blocks generated by such a prediction error.

Filtering on the prediction block may be used to reduce the prediction error. Filtering may be adaptively applying a filter to a region considered to have a large prediction error among prediction blocks. For example, a region considered to have a large prediction error may be a boundary of a prediction block. Also, a region considered to have a large prediction error among prediction blocks may be different according to an intra prediction mode, and filter characteristics may be different.

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

The rectangle shown in FIG. 8 may represent an image (or a picture). Also, an arrow in FIG. 8 may indicate a prediction direction. That is, the image may be encoded and/or decoded according to the prediction direction.

Each picture may be classified into an I picture (intra picture), a P picture (uni-prediction picture), and a B picture (bi-prediction picture) according to the encoding type. Each picture may be encoded according to the encoding type of each picture.

When a target image to be encoded is an I picture, the target image may be encoded using data within the image itself without inter prediction referring to another image. For example, an I picture may be coded only with intra prediction.

When the target image is a P picture, the target image may be encoded through inter prediction using only reference pictures existing in a unidirectional direction. Here, the unidirectional may be forward or reverse.

When the target picture is a B picture, the target picture may be encoded through inter prediction using reference pictures existing in both directions or inter prediction using reference pictures existing in one of the forward and backward directions. Here, the bidirectional may be a forward direction and a reverse direction.

P-pictures and B-pictures that are encoded and/or decoded using a reference picture may be regarded as images for which inter prediction is used.

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

Inter prediction may be performed using motion information.

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

Motion information on the target 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 motion information of a block adjacent to the collocated block. The collocated block may be a block in an already reconstructed collocated picture (col picture). The location of the collocated block in the collocated picture may correspond to the location of the target block in the target image. The collocated picture may be one picture among at least one reference picture included in the reference picture list.

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

The spatial candidate may be a reconstructed block spatially adjacent to the target block.

The temporal candidate may be a reconstructed block corresponding to a target block in an already reconstructed collocated picture (col picture).

In inter prediction, the encoding apparatus 100 and the decoding apparatus 200 may improve encoding efficiency and decoding efficiency by using motion information of a spatial candidate and/or a temporal candidate. The motion information of the spatial candidate may be referred to as spatial motion information. The motion information of the temporal candidate may be referred to as temporal motion information.

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

Inter prediction may be performed using a reference picture.

The reference picture may be at least one of a previous picture of the target picture or a subsequent picture of the target picture. The reference picture may mean an image used for prediction of a target block.

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

Inter prediction may select a reference picture and may select a reference block corresponding to a target block in the reference picture. In addition, inter prediction may generate a prediction block for the target block by using the selected reference block.

The motion information may be derived during inter prediction by each of the encoding apparatus 100 and the decoding apparatus 200 .

The spatial candidate may be a block that 1) exists in the target picture, 2) has already been reconstructed through encoding and/or decoding, and 3) is adjacent to the target block or located at a corner of the target block. Here, the block located at the corner of the target block may be a block vertically adjacent to a neighboring block horizontally adjacent to the target block or a block horizontally adjacent to a neighboring block vertically adjacent to the target block. “A block located at the corner of the target block” may have the same meaning as “a block adjacent to the corner of the target block”. A “block located at the corner of the target block” may be included in “a block adjacent to the target block”.

For example, a spatial candidate is a reconstructed block located at the left of the target block, a reconstructed block located at the top of the target block, a reconstructed block located at the lower left corner of the target block, and a reconstructed block located at the upper right corner of the target block It may be a reconstructed block or a reconstructed block located in the upper left corner of the target block.

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

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

For example, the collocated block may include a first collocated block and a second collocated block. When the coordinates of the identified block are (xP, yP) and the size of the identified block is (nPSW, nPSH), the first collocated block may be a block located at the coordinates (xP + nPSW, yP + nPSH). The second collocated block may be a block located at coordinates (xP + (nPSW >> 1), yP + (nPSH >> 1)). The second collocated block may be selectively used when the first collocated block is unavailable.

The motion vector of the target block may be determined based on the motion vector of the collocated block. Each of the encoding apparatus 100 and the decoding apparatus 200 may scale the motion vector of the collocated block. A scaled motion vector of the collocated block may be used as the motion vector of the target block. Also, the motion vector of the motion information of the temporal candidate stored in the list may be a scaled motion vector.

A ratio of the motion vector of the target block and the motion vector of the collocated block may be the same as the ratio of the first distance and the second distance. The first distance may be a distance between the reference picture and the target picture of the target block. The second distance may be a distance between the reference picture and the collocated picture of the collocated block.

A method of deriving motion information may vary according to the inter prediction mode of the target block. For example, as an inter prediction mode applied for inter prediction, there may be an Advanced Motion Vector Predictor (AMVP) mode, a merge mode and a skip mode, and a current picture reference mode. have. The merge mode may be referred to as a motion merge mode. In the following, each of the modes is described in detail.

1) AMVP mode

When the AMVP mode is used, the encoding apparatus 100 may search for a similar block in the vicinity of the target block. The encoding apparatus 100 may obtain a prediction block by performing prediction on the target block using the found motion information of a similar block. The encoding apparatus 100 may encode a residual block that is a difference between the target block and the prediction block.

1-1) Creation of a prediction motion vector candidate list

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

Hereinafter, the terms “prediction motion vector (candidate)” and “motion vector (candidate)” may be used with the same meaning, and may be used interchangeably.

The spatial motion candidate may include reconstructed spatial neighboring blocks. That is, the motion vector of the reconstructed neighboring block may be referred to as a spatial prediction motion vector candidate.

The temporal motion candidate may include a collocated block and a block adjacent to the collocated block. That is, 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 prediction motion vector candidate.

The zero vector may be a (0, 0) motion vector.

The prediction motion vector candidate may be a motion vector predictor for motion vector prediction. Also, in the encoding apparatus 100, the prediction motion vector candidate may be an initial motion vector search position.

1-2) Searching for a motion vector using the predicted motion vector candidate list

The encoding apparatus 100 may determine a motion vector to be used for encoding a target block within a search range by using the prediction motion vector candidate list. Also, the encoding apparatus 100 may determine a prediction motion vector candidate to be used as a motion vector prediction of the target block from among the motion vector prediction candidates in the prediction motion vector candidate list.

A motion vector to be used for encoding a target block may be a motion vector that can be encoded with a minimum cost.

Also, the encoding apparatus 100 may determine whether to use the AMVP mode in encoding the target block.

1-3) Transmission of inter prediction information

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

Inter prediction information includes 1) mode information indicating whether AMVP mode is used, 2) prediction motion vector index, 3) motion vector difference (MVD), 4) reference direction, and 5) reference picture index. can do.

Also, the inter prediction information may include a residual signal.

When the mode information indicates that the AMVP mode is used, the decoding apparatus 200 may obtain a predicted motion vector index, a motion vector difference, a reference direction, and a reference picture index from the bitstream through entropy decoding.

The prediction motion vector index may indicate a prediction motion vector candidate used for prediction of a target block among prediction motion vector candidates included in the prediction motion vector candidate list.

1-4) Inter prediction in AMVP mode using inter prediction information

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

The decoding apparatus 200 may determine a motion vector candidate for the target block from among the prediction motion vector candidates included in the prediction motion vector candidate list by using the prediction motion vector index. The decoding apparatus 200 may select a prediction motion vector candidate indicated by a prediction motion vector index from among the prediction motion vector candidates included in the prediction motion vector candidate list as the prediction motion vector of the target block.

A motion vector to be actually used for inter prediction of the target block may not match the predicted motion vector. A motion vector to be actually used for inter prediction of a target block and MVD may be used to indicate a difference between the prediction motion vectors. The encoding apparatus 100 may derive a prediction motion vector similar to a motion vector to be actually used for inter prediction of a target block in order to use an MVD of as small a size as possible.

The MVD may be a difference between a motion vector of a target block and a prediction motion vector. The encoding apparatus 100 may calculate the MVD and entropy-encode the MVD.

The MVD may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. The decoding apparatus 200 may decode the received MVD. The decoding apparatus 200 may derive the motion vector of the target block by summing the decoded MVD and the prediction motion vector. That is, the motion vector of the target block derived from the decoding apparatus 200 may be the sum of the entropy-decoded MVD and the motion vector candidate.

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

The reference direction only indicates a reference picture list used for prediction of a target block, and may not indicate that directions of reference pictures are limited to a forward direction or a backward direction. In other words, each of the reference picture list L0 and the reference picture list L1 may include forward and/or backward pictures.

That the reference direction is uni-direction may mean that one reference picture list is used. That the reference direction is bi-direction may mean that two reference picture lists are used. In other words, the reference direction may indicate that only the reference picture list L0 is used, that only the reference picture list L1 is used, and one of two reference picture lists.

The reference picture index may indicate a reference picture used for prediction of a target block among reference pictures of the reference picture list. The reference picture index may be entropy-encoded by the encoding apparatus 100 . The entropy-encoded reference picture index may be signaled from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream.

When two reference picture lists are used for prediction of the target block. One reference picture index and one motion vector may be used for each reference picture list. In addition, when two reference picture lists are used for prediction of the target block, two prediction blocks may be specified for the target block. For example, a (final) prediction block of the target block may be generated through an average or a weighted-sum of two prediction blocks for the target block.

The motion vector of the target block may be derived by the prediction motion vector index, the MVD, the reference direction, and the reference picture index.

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

By encoding the prediction motion vector index and the MVD without encoding the motion vector itself of the target block, the amount of bits transmitted from the encoding apparatus 100 to the decoding apparatus 200 may be reduced, and encoding efficiency may be improved.

Motion information of a neighboring block reconstructed with respect to the target block may be used. In a specific inter prediction mode, the encoding apparatus 100 may not separately encode the motion information itself for the target block. The motion information of the target block is not coded, but other information capable of deriving the motion information of the target block through the reconstructed motion information of the neighboring block may be coded instead. As other information is encoded instead, the amount of bits transmitted to the decoding apparatus 200 may be reduced, and encoding efficiency may be improved.

For example, as an inter prediction mode in which the motion information of the target block is not directly encoded, there may be a skip mode and/or a merge mode. In this case, the encoding apparatus 100 and the decoding apparatus 200 may use an identifier and/or an index indicating which motion information of which unit among the reconstructed neighboring units is used as the motion information of the target unit.

2) Merge mode

As a method of deriving motion information of a target block, there is a merge. Merge may mean merging motions for a plurality of blocks. Merge may mean applying motion information of one block to another block as well. In other words, the merge mode may refer to a mode in which motion information of a target block is derived from motion information of a neighboring block.

When the merge mode is used, the encoding apparatus 100 may perform prediction on motion information of a target block using motion information of a spatial candidate and/or motion information of a temporal candidate. The spatial candidate may include a reconstructed spatial neighboring block spatially adjacent to the target block. A spatially adjacent block may include a left adjacent block and a top adjacent block. A temporal candidate may include a collocated block. The terms “spatial candidate” and “spatial merge candidate” may be used interchangeably and may be used interchangeably. The terms “temporal candidate” and “temporal merge candidate” may be used interchangeably and may be used interchangeably.

The encoding apparatus 100 may obtain a prediction block through prediction. The encoding apparatus 100 may encode a residual block that is a difference between the target block and the prediction block.

2-1) Preparation of merge candidate list

When the merge mode is used, each of the encoding apparatus 100 and the decoding apparatus 200 may generate a merge candidate list using motion information of a spatial candidate and/or motion information of a temporal candidate. The motion information may include 1) a motion vector, 2) a reference picture index, and 3) a reference direction. The reference direction may be unidirectional or bidirectional.

The merge candidate list may include merge candidates. The merge candidate may be motion information. In other words, the merge candidate list may be a list in which motion information is stored.

The merge candidates may be motion information such as a temporal candidate and/or a spatial candidate. Also, the merge candidate list may include a new merge candidate generated by a combination of merge candidates already existing in the merge candidate list. In other words, the merge candidate list may include new motion information generated by a combination of motion information already existing in the merge candidate list.

Also, the merge candidate list may include zero vector motion information. A zero vector may be referred to as a zero merge candidate.

In other words, the motion information in the merge candidate list includes: 1) motion information of a spatial candidate, 2) motion information of a temporal candidate, 3) motion information generated by a combination of motion information already existing in the merge candidate list, 4) zero vector may be at least one of

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

The merge candidate list may be generated before prediction by the merge mode is performed.

The number of merge candidates in the merge candidate list may be predefined. The encoding apparatus 100 and the decoding apparatus 200 may add merge candidates to the merge candidate list according to a predefined method and a predefined order so that the merge candidate list has a predefined number of merge candidates. The merge candidate list of the encoding apparatus 100 and the merge candidate list of the decoding apparatus 200 may become the same through a predefined method and a predefined rank.

Merge may be applied on a CU basis or a PU basis. When the merge is performed in units of CUs or PUs, the encoding apparatus 100 may transmit a bitstream including predefined information to the decoding apparatus 200 . For example, the predefined information includes: 1) information indicating whether to perform a merge for each block partition, 2) which block among blocks that are spatial and/or temporal candidates for a target block to be merged with It may include information about whether

2-2) Search for motion vector using merge candidate list

The encoding apparatus 100 may determine a merge candidate to be used for encoding the target block. For example, the encoding apparatus 100 may perform predictions on a target block using merge candidates in the merge candidate list and generate residual blocks for the merge candidates. The encoding apparatus 100 may use a merge candidate requiring a minimum cost in prediction and encoding of the residual block for encoding of the target block.

Also, the encoding apparatus 100 may determine whether to use the merge mode in encoding the target block.

2-3) Transmission of inter prediction information

The encoding apparatus 100 may generate a bitstream including inter prediction information required for inter prediction. The encoding apparatus 100 may generate entropy-encoded inter prediction information by performing entropy encoding on the inter prediction information, and may transmit a bitstream including the entropy-encoded inter prediction information to the decoding apparatus 200 . Through the bitstream, entropy-encoded inter prediction information may be signaled from the encoding apparatus 100 to the decoding apparatus 200 .

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

The inter prediction information may include 1) mode information indicating whether a merge mode is used and 2) a merge index.

Also, the inter prediction information may include a residual signal.

The decoding apparatus 200 may obtain the merge index from the bitstream only when the mode information indicates that the merge mode is used.

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

The merge index may indicate a merge candidate used for prediction of a target block among merge candidates included in the merge candidate list. Alternatively, the merge index may indicate which block among neighboring blocks spatially or temporally adjacent to the target block is merged with.

2-4) Inter prediction of merge mode using inter prediction information

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

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

3) Skip mode

The skip mode may be a mode in which motion information of a spatial candidate or motion information of a temporal candidate is applied to the target block as it is. Also, the skip mode may be a mode that does not use a residual signal. In other words, when the skip mode is used, the reconstructed block may be a predictive block.

The difference between the merge mode and the skip mode may be whether a residual signal is transmitted or used. In other words, skip mode may be similar to merge mode except that no residual signal is transmitted or used.

When the skip mode is used, the encoding apparatus 100 transmits information indicating which block of blocks that are spatial candidates or temporal candidate blocks is used as the motion information of the target block to the decoding apparatus 200 through a bitstream. can be transmitted The encoding apparatus 100 may generate entropy-encoded information by performing entropy encoding on such information, and may signal the entropy-encoded information to the decoding apparatus 200 through a bitstream.

Also, when the skip mode is used, the encoding apparatus 100 may not transmit other syntax element information such as MVD to the decoding apparatus 200 . For example, when used with the skip mode, the encoding apparatus 100 may not signal a syntax element related to at least one of MVC, a coded block flag, and a transform coefficient level to the decoding apparatus 200 .

3-1) Preparation of merge candidate list

The skip mode may also use the merge candidate list. In other words, the merge candidate list can be used in both the merge mode and the skip mode. In this aspect, the merge candidate list may be referred to as a “skip candidate list” or a “merge/skip candidate list”.

Alternatively, the skip mode may use a separate candidate list different from the merge mode. In this case, in the following description, the merge candidate list and the merge candidate may be replaced with the skip candidate list and the skip candidate, respectively.

The merge candidate list may be generated before prediction by skip mode is performed.

3-2) Search for motion vector using merge candidate list

The encoding apparatus 100 may determine a merge candidate to be used for encoding the target block. For example, the encoding apparatus 100 may perform predictions on the target block using merge candidates in the merge candidate list. The encoding apparatus 100 may use a merge candidate requiring the minimum cost in prediction for encoding the target block.

Also, the encoding apparatus 100 may determine whether to use the skip mode in encoding the target block.

3-3) Transmission of inter prediction information

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

The inter prediction information may include 1) mode information indicating whether a skip mode is used and 2) a skip index.

The skip index may be the same as the merge index described above.

When the skip mode is used, the target block may be coded without a residual signal. The inter prediction information may not include a residual signal. Alternatively, the bitstream may not include a residual signal.

The decoding apparatus 200 may obtain the skip index from the bitstream only when the mode information indicates that the skip mode is used. As described above, the merge index and the skip index may be the same. The decoding apparatus 200 may obtain the skip index from the bitstream only when the mode information indicates that the merge mode or the skip mode is used.

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

3-4) Inter prediction in skip mode using inter prediction information

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

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

4) Current picture reference mode

The current picture reference mode may refer to a prediction mode using a pre-reconstructed region in the current picture to which the target block belongs.

A vector for specifying the pre-reconstructed region may be defined. Whether the target block is encoded in the current picture reference mode may be determined using the reference picture index of the target block.

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

When the target block is encoded in the current picture reference mode, the current picture may be added at a fixed position or an arbitrary position in the reference picture list for the target block.

For example, the fixed position may be a position in which the reference picture index is 0 or the last position.

When the current picture is added to an arbitrary position in the reference picture list, a separate reference picture index indicating the arbitrary position may be signaled from the encoding apparatus 100 to the decoding apparatus 200 .

In the aforementioned AMVP mode, merge mode, and skip mode, motion information to be used for prediction of a target block among motion information in the list may be specified through an index to the list.

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

Accordingly, the above-mentioned lists (ie, the prediction motion vector candidate list and the merge candidate list) may have to be derived in the same manner based on the same data in the encoding apparatus 100 and the decoding apparatus 200 . Here, the same data may include a reconstructed picture and a reconstructed block. Also, in order to specify an element by index, the order of the elements in the list may have to be constant.

9 shows spatial candidates according to an example.

In Fig. 9, the locations of spatial candidates are shown.

A large block in the middle may represent a target block. Five small blocks may represent spatial candidates.

The coordinates of the target block may be (xP, yP), and the size of the target block may be (nPSW, nPSH).

The spatial candidate A ₀ may be a block adjacent to the lower left corner of the target block. A ₀ may be a block occupying a pixel of coordinates (xP - 1, yP + nPSH + 1).

The spatial candidate A ₁ may be a block adjacent to the left of the target block. A ₁ may be the lowest block among blocks adjacent to the left of the target block. Alternatively, A ₁ may be a block adjacent to the top of A ₀ . A ₁ may be a block occupying a pixel of coordinates (xP - 1, yP + nPSH).

The spatial candidate B ₀ may be a block adjacent to the upper right corner of the target block. B ₀ may be a block occupying a pixel of coordinates (xP + nPSW + 1, yP - 1).

The spatial candidate B ₁ may be a block adjacent to the top of the target block. B ₁ may be a rightmost block among blocks adjacent to the top of the target block. Alternatively, B ₁ may be a block adjacent to the left of B ₀ . B ₁ may be a block occupying a pixel of coordinates (xP + nPSW, yP - 1).

The spatial candidate B ₂ may be a block adjacent to the upper left corner of the target block. B ₂ may be a block occupying a pixel of coordinates (xP - 1, yP - 1).

Determination of availability of spatial and temporal candidates

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

Hereinafter, a candidate block may include a spatial candidate and a temporal candidate.

For example, the above determination may be made by sequentially applying the following steps 1) to 4).

Step 1) If the PU including the candidate block is outside the boundary of the picture, the availability of the candidate block may be set to false. "Availability set to false" may have the same meaning as "availability set to unavailable".

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

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

Step 4) If the prediction mode of the PU including the candidate block is the intra prediction mode, the availability of the candidate block may be set to false. If the PU including the candidate block does not use inter prediction, the availability of the candidate block may be set to false.

10 illustrates an order of adding motion information of spatial candidates to a merge list according to an example.

As shown in FIG. 10 , in adding motion information of spatial candidates to the merge list, the order of A ₁ , B ₁ , B ₀ , A ₀ and B ₂ may be used. That is, in the order of A ₁ , B ₁ , B ₀ , A ₀ and B ₂ , motion information of available spatial candidates may be added to the merge list.

Method of derivation of merge list in merge mode and skip mode

As described above, the maximum number of merge candidates in the merge list may be set. The set maximum number is displayed as N. The set number may be transmitted from the encoding apparatus 100 to the decoding apparatus 200 . A slice header of a slice may include N. That is, the maximum number of merge candidates in the merge list for the target block of the slice may be set by the slice header. For example, the value of N may be 5 by default.

The motion information (ie, the merge candidate) may be added to the merge list in the order of steps 1) to 4) below.

Step 1) Among the spatial candidates, available spatial candidates may be added to the merge list. Motion information of available spatial candidates may be added to the merge list in the order shown in FIG. 10 . In this case, if motion information of an available spatial candidate overlaps with other motion information already existing in the merge list, the motion information may not be added to the merge list. Checking whether or not it overlaps with other motion information existing in the list may be abbreviated as "redundancy check".

There may be a maximum of N pieces of added motion information.

Step 2) If the number of motion information in the merge list is smaller than N and a temporal candidate is available, the motion information of the temporal candidate may be added to the merge list. In this case, if motion information of an available temporal candidate overlaps with other motion information already present in the merge list, the motion information may not be added to the merge list.

Step 3) If the number of motion information in the merge list is smaller than N and the type of the target slice is “B”, the combined motion information generated by combined bi-prediction is added to the merge list. can

The target slice may be a slice including the target block.

The combined motion information may be a combination of L0 motion information and L1 motion information. The L0 motion information may be motion information referring only to the reference picture list L0. The L1 motion information may be motion information referring only to the reference picture list L1.

In the merge list, there may be one or more L0 motion information. Also, in the merge list, there may be one or more L1 motion information.

The combined motion information may be one or more. In generating the combined motion information, which L0 motion information and which L1 motion information among the one or more L0 motion information and the one or more L1 motion information are to be used may be predefined. One or more combined motion information may be generated in a predefined order by combined bidirectional prediction using different pairs of motion information in the merge list. One of the different pairs of motion information may be L0 motion information and the other may be L1 motion information.

For example, the combined motion information added with the highest priority may be a combination of L0 motion information having a merge index of 0 and L1 motion information having a merge index of 1. If the motion information having the merge index of 0 is not the L0 motion information or the motion information having the merge index of 1 is not the L1 motion information, the combined motion information may not be generated and added. Next added motion information may be a combination of L0 motion information having a merge index of 1 and L1 motion information having a merge index of 0. The following specific combinations may follow other combinations of encoding/decoding fields of moving pictures.

In this case, when the combined motion information overlaps with other motion information already existing in the merge list, the combined motion information may not be added to the merge list.

Step 4) If the number of motion information in the merge list is smaller than N, zero vector motion information may be added to the merge list.

The zero vector motion information may be motion information in which a motion vector is a zero vector.

There may be one or more zero vector motion information. Reference picture indices of one or more zero vector motion information may be different from each other. For example, the value of the reference picture index of the first zero vector motion information may be 0. The value of the reference picture index of the second zero vector motion information may be 1.

The number of zero vector motion information may be equal to the number of reference pictures in the reference picture list.

The reference direction of the zero vector motion information may be bidirectional. Both motion vectors may be zero vectors. The number of zero vector motion information may be the smaller of the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1. Alternatively, when the number of reference pictures in the reference picture list L0 and the number of reference pictures in the reference picture list L1 are different from each other, a unidirectional reference direction may be used for a reference picture index that can be applied to only one reference picture list.

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

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

The order of steps 1) to 4) described above is merely exemplary, and the order between the steps may be interchanged. Also, some of the steps may be omitted according to predefined conditions.

Method of deriving a predictive motion vector candidate list in AMVP mode

The maximum number of prediction motion vector candidates in the prediction motion vector candidate list may be predefined. The predefined maximum number is denoted by N. For example, the predefined maximum number may be two.

The motion information (ie, the prediction motion vector candidate) may be added to the prediction motion vector candidate list in the order of steps 1) to 3) below.

Step 1) Among the spatial candidates, available spatial candidates may be added to the prediction motion vector candidate list. The spatial candidates may include a first spatial candidate and a second spatial candidate.

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

Motion information of the available spatial candidates may be added to the prediction motion vector candidate list in the order of the first spatial candidate and the second spatial candidate. In this case, when motion information of an available spatial candidate overlaps with other motion information already existing in the prediction motion vector candidate list, the motion information may not be added to the prediction motion vector candidate list. That is, when the value of N is 2, if the motion information of the second spatial candidate is the same as the motion information of the first spatial candidate, the motion information of the second spatial candidate may not be added to the prediction motion vector candidate list.

There may be a maximum of N pieces of added motion information.

Step 2) If the number of motion information in the prediction motion vector candidate list is smaller than N and a temporal candidate is available, the motion information of the temporal candidate may be added to the prediction motion vector candidate list. In this case, when motion information of an available temporal candidate overlaps with other motion information already existing in the prediction motion vector candidate list, the motion information may not be added to the prediction motion vector candidate list.

Step 3) If the number of motion information in the prediction motion vector candidate list is smaller than N, zero vector motion information may be added to the prediction motion vector candidate list.

There may be one or more zero vector motion information. Reference picture indices of one or more zero vector motion information may be different from each other.

The encoding apparatus 100 and/or the decoding apparatus 200 may sequentially add zero vector motion information to the prediction motion vector candidate list while changing the reference picture index.

When the zero vector motion information overlaps with other motion information already existing in the prediction motion vector candidate list, the zero vector motion information may not be added to the prediction motion vector candidate list.

The description of the zero vector motion information described above for the merge list may also be applied to the zero vector motion information. A duplicate description is omitted.

The order of steps 1) to 3) described above is merely exemplary, and the order between the steps may be interchanged. Also, some of the steps may be omitted according to predefined conditions.

11 illustrates a process of transformation and quantization according to an example.

As shown in FIG. 11 , a quantized level may be generated by performing a transformation and/or quantization process on the residual signal.

The residual signal may be generated as a difference between the original block and the prediction block. Here, the prediction block may be a block generated by intra prediction or inter prediction.

The transformation may include at least one of a primary transformation and a secondary transformation. A transform coefficient may be generated by performing a first-order transform on the residual signal, and a second-order transform coefficient may be generated by performing a second-order transform on the transform coefficient.

A primary transform may be performed using at least one of a plurality of pre-defined transform methods. As an example, the plurality of pre-defined transform methods are based on a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), and a Karhunen-Loube Transform (KLT). transformations, and the like.

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

The transform method(s) applied to the primary transform and/or the quadratic transform may be determined according to at least one of coding parameters for the target block and/or the neighboring block. Alternatively, transformation information indicating a transformation method may be signaled from the encoding apparatus 100 to the decoding apparatus 200 .

A quantized level may be generated by performing quantization on a result or residual signal generated by performing a first-order transform and/or a second-order transform.

The quantized level may be scanned according to at least one of an upper right diagonal scan, a vertical scan, and a horizontal scan according to at least one of an intra prediction mode, a block size, and a block shape.

For example, the coefficients may be changed into a one-dimensional vector form by scanning the coefficients of the block using up-right diagonal scanning. Alternatively, a vertical scan that scans a two-dimensional block shape coefficient in a column direction or a horizontal scan that scans a two-dimensional block shape coefficient in a row direction may be used instead of the upper right diagonal scan according to the size of the transform block and/or the intra prediction mode have.

The scanned quantization level may be entropy-coded, and the bitstream may include the entropy-coded quantization level.

The decoding apparatus 200 may generate a quantized level through entropy decoding of the bitstream. The quantized levels may be aligned in a two-dimensional block form through inverse scanning. In this case, as a method of inverse scanning, at least one of an upper right diagonal scan, a vertical scan, and a horizontal scan may be performed.

Inverse quantization may be performed on the quantized level. A second-order inverse transform may be performed on a result generated by performing inverse quantization, depending on whether a second-order inverse transform is performed. Also, on the result generated by performing the second-order inverse transform, the first-order inverse transform may be performed depending on whether the first-order inverse transform is performed. A reconstructed residual signal may be generated by performing a first-order inverse transform on a result generated by performing a second-order inverse transform.

12 is a structural diagram of an encoding apparatus according to an embodiment.

The encoding apparatus 1200 may correspond to the above-described encoding apparatus 100 .

The encoding apparatus 1200 includes a processing unit 1210 , a memory 1230 , a user interface (UI) input device 1250 , a UI output device 1260 , and storage that communicate with each other through a bus 1290 . (1240) may be included. Also, the encoding apparatus 1200 may further include a communication unit 1220 connected to the network 1299 .

The processor 1210 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), the memory 1230 , or the storage 1240 . The processing unit 1210 may be at least one hardware processor.

The processing unit 1210 may generate and process a signal, data, or information input to the encoding apparatus 1200 , output from the encoding apparatus 1200 , or used inside the encoding apparatus 1200 , and a signal, Inspection, comparison, and judgment related to data or information may be performed. That is, in the embodiment, generation and processing of data or information, and inspection, comparison, and judgment related to data or information may be performed by the processing unit 1210 .

The processing unit 1210 includes an inter prediction unit 110 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , a transform unit 130 , a quantization unit 140 , an entropy encoding unit 150 , and inverse quantization. It may include a unit 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference picture buffer 190 .

Inter prediction unit 110 , intra prediction unit 120 , switch 115 , subtractor 125 , transform unit 130 , quantization unit 140 , entropy encoding unit 150 , inverse quantization unit 160 , At least some of the inverse transform unit 170 , the adder 175 , the filter unit 180 , and the reference picture buffer 190 may be program modules and may communicate with an external device or system. The program modules may be included in the encoding apparatus 1200 in the form of an operating system, an application program module, and other program modules.

Program modules may be physically stored on various known storage devices. Also, at least some of these program modules may be stored in a remote storage device capable of communicating with the encoding device 1200 .

Program modules include routines, subroutines, programs, objects, components, and data that perform functions or operations according to an embodiment or implement abstract data types according to an embodiment. It may include, but is not limited to, a data structure and the like.

The program modules may include instructions or codes that are executed by at least one processor of the encoding apparatus 1200 .

The processing unit 1210 includes an inter prediction unit 110 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , a transform unit 130 , a quantization unit 140 , an entropy encoding unit 150 , and inverse quantization. Commands or codes of the unit 160 , the inverse transform unit 170 , the adder 175 , the filter unit 180 , and the reference picture buffer 190 may be executed.

Storage may represent memory 1230 and/or storage 1240 . The memory 1230 and the storage 1240 may be various types of volatile or non-volatile storage media. For example, the memory 1230 may include at least one of a ROM 1231 and a RAM 1232 .

The storage unit may store data or information used for the operation of the encoding apparatus 1200 . In an embodiment, data or information included in the encoding apparatus 1200 may be stored in a storage unit.

For example, the storage unit may store pictures, blocks, lists, motion information, inter prediction information, and bitstreams.

The encoding apparatus 1200 may be implemented in a computer system including a recording medium that can be read by a computer.

The recording medium may store at least one module required for the encoding apparatus 1200 to operate. The memory 1230 may store at least one module, and the at least one module may be configured to be executed by the processing unit 1210 .

A function related to communication of data or information of the encoding apparatus 1200 may be performed through the communication unit 1220 .

For example, the communication unit 1220 may transmit the bitstream to the decoding apparatus 1300 to be described later.

13 is a structural diagram of a decoding apparatus according to an embodiment.

The decoding apparatus 1300 may correspond to the above-described decoding apparatus 200 .

The decryption apparatus 1300 communicates with each other via a bus 1390 (1310), a memory 1330, a user interface (UI) input device 1350, a UI output device 1360, and a storage (storage) ( 1340) may be included. Also, the decryption apparatus 1300 may further include a communication unit 1320 connected to the network 1399 .

The processing unit 1310 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), the memory 1330 , or the storage 1340 . The processing unit 1310 may be at least one hardware processor.

The processing unit 1310 may generate and process a signal, data, or information input to the decoding device 1300, output from the decoding device 1300, or used inside the decoding device 1300, the signal, Inspection, comparison, and judgment related to data or information may be performed. That is, in the embodiment, generation and processing of data or information, and inspection, comparison, and judgment related to data or information may be performed by the processing unit 1310 .

The processing unit 1310 includes an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , an inter prediction unit 250 , an adder 255 , a filter unit 260 and A reference picture buffer 270 may be included.

Entropy decoding unit 210 , inverse quantization unit 220 , inverse transform unit 230 , intra prediction unit 240 , inter prediction unit 250 , adder 255 , filter unit 260 , and reference picture buffer 270 . ) may be program modules, and may communicate with an external device or system. The program modules may be included in the decryption apparatus 1300 in the form of an operating system, an application program module, and other program modules.

Program modules may be physically stored on various known storage devices. Also, at least some of these program modules may be stored in a remote storage device capable of communicating with the decryption device 1300 .

Program modules include routines, subroutines, programs, objects, components, and data that perform functions or operations according to an embodiment or implement abstract data types according to an embodiment. It may include, but is not limited to, a data structure and the like.

The program modules may include instructions or codes that are executed by at least one processor of the decoding apparatus 1300 .

The processing unit 1310 includes an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , an inter prediction unit 250 , an adder 255 , a filter unit 260 and An instruction or code of the reference picture buffer 270 may be executed.

Storage may represent memory 1330 and/or storage 1340 . The memory 1330 and the storage 1340 may be various types of volatile or non-volatile storage media. For example, the memory 1330 may include at least one of a ROM 1331 and a RAM 1332 .

The storage unit may store data or information used for the operation of the decryption apparatus 1300 . In an embodiment, data or information included in the decryption apparatus 1300 may be stored in the storage unit.

For example, the storage unit may store pictures, blocks, lists, motion information, inter prediction information, and bitstreams.

The decryption apparatus 1300 may be implemented in a computer system including a recording medium that can be read by a computer.

The recording medium may store at least one module required for the decryption apparatus 1300 to operate. The memory 1330 may store at least one module, and the at least one module may be configured to be executed by the processing unit 1310 .

A function related to communication of data or information of the decryption apparatus 1300 may be performed through the communication unit 1320 .

For example, the communication unit 1320 may receive a bitstream from the encoding apparatus 1200 .

14 is a flowchart of a prediction method according to an embodiment.

The prediction method may be performed by the encoding apparatus 1200 and/or the decoding apparatus 1300 .

For example, the encoding apparatus 1200 may perform the prediction method of the embodiment to compare efficiencies of a plurality of prediction methods for the target block, and the prediction method of the embodiment to generate a reconstructed block for the target block can be performed.

For example, the decoding apparatus 1300 may perform the prediction method of the embodiment to generate a reconstructed block for the target block.

Hereinafter, the processing unit may correspond to the processing unit 1210 of the encoding apparatus 1200 and/or the processing unit 1310 of the decoding apparatus 1300 .

In operation 1410, the processor may select a prediction mode to be used for prediction of the target block. The selected prediction mode may be one or more.

In an embodiment, when there are a plurality of selected prediction modes, prediction mode determination information for determining a prediction mode to be used for prediction of a target block from among the plurality of selected prediction modes may be used. In encoding of the target block, when there are a plurality of selected prediction modes, the processor may generate prediction mode determination information indicating a prediction mode to be used for prediction of the target block from among the plurality of selected prediction modes.

In an embodiment, the selected prediction mode may be an inter prediction mode. The prediction mode may be a specified inter prediction method among a plurality of inter prediction methods.

In one embodiment, the selected prediction mode may be an intra prediction mode. The prediction mode may be a specified intra prediction method among a plurality of intra prediction methods.

An example of step 1410 is described in detail below with reference to FIG. 15 .

In operation 1420, the processor may perform prediction of the target block based on the selected prediction mode.

In one embodiment, the prediction may be intra prediction or inter prediction.

In decoding the target block, when there are a plurality of selected prediction modes, the processor may determine a prediction mode to be used for prediction of the target block from among the plurality of selected prediction modes by using prediction mode determination information.

An example of step 1420 is described in detail below with reference to FIGS. 20 and 21 .

15 is a flowchart of a prediction mode selection method according to an embodiment.

The prediction mode selection method of the embodiment may correspond to the above-described step 1410 . Step 1410 may include steps 1510 and 1520 .

In operation 1410 , the processor may select one or more prediction modes from among a plurality of prediction modes when performing inter prediction on the target block.

The plurality of prediction modes may be referred to as a plurality of available prediction modes available in the encoding apparatus 1200 and/or the decoding apparatus 1300 . The selected one or more prediction modes may be named one or more prediction mode candidates. The selected one or more prediction modes may be one or more prediction mode candidates that can be used for encoding and/or decoding of a target block.

In one embodiment, the plurality of prediction modes are AMVP mode, merge mode, skip mode, Advanced Temporal Motion Vector Prediction (ATVP) mode, Spatial-Temporal Motion Vector Predictor (STMVP). ) mode, Pattern Matched Motion Vector Derivation (PMMVD) template matching mode, Bilateral matching mode, Affine mode, and BI-directional Optical It may include at least one of a flow (BIO) mode, a decoder-side motion vector refinement (DMVR) mode, and a Local Illumination Compensation (LIC) mode.

In an embodiment, the affine mode may include an affine inter mode and an affine merge mode.

In an embodiment, a merge or AMVP candidate list may be configured based on motion information of the first prediction mode. For example, a candidate having a motion vector similar to or identical to the motion vector of the first prediction mode may be excluded from the merge or AMVP candidate list, or the order of these candidates may be changed. The first prediction mode may be at least one of an AMVP mode, a merge mode, a skip mode, a template matching mode, a bilateral matching mode, and an affine merge mode.

In one embodiment, the plurality of prediction modes may include the other modes described above.

The processor may select one or more prediction modes from among the plurality of prediction modes by using at least one of the prediction mode selection method of operation 1510 and the prediction mode selection method of operation 1520 .

In operation 1510, the processor may select a prediction mode based on statistical values of the plurality of prediction modes.

For example, the prediction mode having the lowest statistical value or the highest statistical value may be selected through comparison of statistical values of the plurality of prediction modes.

The statistical value may mean at least one of an average value, a maximum value, a minimum value, a mode value, a median value, a weighted average value, a distortion value, and a rate-distortion value.

Alternatively, the aforementioned statistical value may be a statistical value for rate-distortion cost or rate-distortion cost. The processor may calculate rate-distortion costs of the plurality of prediction modes by performing entropy encoding of the target block using each prediction mode for each of the prediction modes of the plurality of prediction modes. The processing unit may select one or more prediction modes from among the plurality of prediction modes according to rate-distortion costs. The processing unit may select a prediction mode having the lowest rate-distortion cost through comparison of rate-distortion costs of the plurality of prediction modes.

In operation 1520 , the processor may derive prediction mode information for the target block, and may select one or more prediction modes from among a plurality of prediction modes using the derived prediction mode information.

In an embodiment, the processing unit may use information related to the reference block in deriving the prediction mode information. Alternatively, the prediction mode information may include information related to a reference block.

In an embodiment, the reference block may include one or more of a spatial neighboring block spatially adjacent to the target block and a temporal neighboring block temporally adjacent to the target block.

For example, in deriving the prediction mode information for the target block using the information related to the reference block, the processing unit is one of derivation of prediction mode information using a spatial neighboring block and derivation of prediction mode information using a temporal neighboring block. more can be used.

In an embodiment, information related to a reference block includes a motion vector of a reference block, a prediction direction of a reference block, a reference picture index of a reference block, an encoding mode of the reference block, a reference picture list of the reference block, and a picture order count ( It may include at least one of a picture order count (POC), a quantization parameter (QP) of a reference block, and a coded block flag (CBF) of the reference block.

Also, according to an embodiment, the information related to the reference block may further include information used for encoding and/or decoding of the aforementioned reference block.

In an embodiment, the processing unit may select a prediction mode from among a template matching mode and a bilateral matching mode. The plurality of prediction modes may include a template matching mode and a bilateral matching mode.

In selecting one or more prediction modes from among a plurality of prediction modes, such as a template matching mode and a bilateral matching mode, the processing unit may derive motion vectors of reference blocks, and determine the consistency of the derived motion vectors. and may select one or more prediction modes from among a plurality of prediction modes based on the determined correlation. The derivation of motion vectors, determination of correlation, and selection of a prediction mode are described below with reference to FIG. 16 .

In an embodiment, the processing unit may select one or more prediction modes from among a plurality of prediction modes by using the prediction direction. The prediction direction may be a prediction direction of a target block or a prediction direction of a reference block.

In an embodiment, the processing unit may select one or more prediction modes according to whether the inter prediction of the target block is uni-prediction or bi-prediction.

For example, if the inter prediction of the target block is bi-directional prediction, the processor may select a bilateral matching mode from among a plurality of prediction modes. The processing unit may select a template matching mode from among a plurality of prediction modes when the inter prediction of the target block is unidirectional prediction.

For example, if the inter prediction of the reference block is bi-directional prediction, the processor may select a bilateral matching mode from among a plurality of prediction modes. If the inter prediction of the reference block is uni-prediction, the processor may select a template matching mode from among a plurality of prediction modes.

In an embodiment, the processing unit may select one or more prediction modes from among a plurality of prediction modes by using the coding parameter. The coding parameter may be a coding parameter of a target block or a coding parameter of a reference block.

For example, the processor may determine whether the prediction mode of the reference block is the intra prediction mode or the inter prediction mode according to the coding parameter of the reference block. The processing unit may select one or more prediction modes from among a plurality of prediction modes according to whether the prediction mode of the reference block is an intra prediction mode or an inter prediction mode. The reference block may be a temporal neighboring block.

In an embodiment, the processing unit may select one or more prediction modes from among a plurality of prediction modes by using the POC. The POC may be the POC of the target picture including the target block or the POC of the reference picture including the reference block.

For example, the processing unit may select one or more prediction modes from among a plurality of prediction modes based on a difference between the specified POCs.

For example, the processing unit may select a template matching mode from among a plurality of prediction modes when a difference between the specified POCs is smaller than a threshold. Here, the specified POCs may be the POC of the target picture and the POC of the reference picture.

16 shows reference blocks according to an example.

As described above, in selecting one or more prediction modes for a target block from among a plurality of prediction modes, motion vectors of reference blocks may be used. The motion vector can be derived as follows.

The reference blocks may include spatially adjacent blocks of the target block.

In Fig. 16, "a" denotes a block a. Block a may be the leftmost block among blocks adjacent to the top of the target block. "b" represents block b. Block b may be the second block from the left among blocks adjacent to the top of the target block. "c" represents block c. Block c may be a second block from the right among blocks adjacent to the top of the target block. "d" represents block d. Block d may be the rightmost block among blocks adjacent to the top of the target block.

In Fig. 16, "e" denotes a block e. Block e may be an uppermost block among blocks adjacent to the left of the target block. "f" denotes block f. Block f may be the second block from the top among blocks adjacent to the left of the target block. "g" stands for block g. Block g may be a block second from the bottom among blocks adjacent to the left of the target block. "h" represents block h. Block h may be the lowest block among blocks adjacent to the left of the target block.

The processor may use motion vectors of n or more merge candidates in deriving the motion vector of the reference block. In other words, the reference block may be n or more merge candidates. n may be a positive integer.

For example, when the processor derives two motion vectors, the processor may use the first merge candidate and the second merge candidate as reference blocks.

For example, when the processor derives three motion vectors, the processor may use the first merge candidate, the second merge candidate, and the third merge candidate as reference blocks.

In one embodiment, the merge candidate may be a block located at a specified position with respect to the target block.

In an embodiment, the merge candidate may be a block generated based on blocks at positions specified with respect to the target block. Alternatively, the merge candidate may be a virtual block or a derived block determined based on blocks at positions specified with respect to the target block. Alternatively, the virtual block or the derived block may be regarded as a reference block. In this case, the reference block may be a block generated based on blocks at positions specified with respect to the target block.

Blocks at specified locations may include spatially adjacent blocks and temporally adjacent blocks.

For example, when two merge candidates are used, the plurality of merge candidates may include an upper location block and a left location block. The upper block may be a block adjacent to the top of the target block or a block generated based on blocks adjacent to the top of the target block. The left location block may be a block adjacent to the left side of the target block or a block generated based on blocks adjacent to the left side of the target block.

In an embodiment, the processing unit may derive a motion vector of one of block a, block b, block c, and block d, and use the derived motion vector as a motion vector of the upper block.

For example, the processing unit may use the motion vector of the block a as the motion vector of the upper position block.

For example, the processing unit may use the motion vector of block d as the motion vector of the upper position block.

In an embodiment, the processing unit may derive a motion vector of one of block e, block f, block g, and block h, and may use the derived motion vector as a motion vector of the left position block.

For example, the processing unit may use the motion vector of the block e as the motion vector of the left position block.

For example, the processing unit may use the motion vector of block h as the motion vector of the left position block.

In an embodiment, the processing unit may derive motion vectors of one or more blocks among block a, block b, block c, and block d, and use a combination of the derived motion vectors as a motion vector of the upper position block.

For example, the combination of derived motion vectors may be an average of the derived motion vectors or a weighted average of the derived motion vectors. Alternatively, the combination of the derived motion vectors may be a result of a calculation formula using the derived motion vectors or a motion vector determination method.

For example, the processing unit may use an average or a weighted average of the motion vector of the block a and the motion vector of the block b as the motion vector of the upper block.

For example, the processor may use an average or a weighted average of motion vectors of m leftmost blocks or m rightmost blocks among blocks adjacent to the top of the target block as the motion vector of the upper block. m may be an integer of 2 or more.

For example, the processing unit may use an average or a weighted average of motion vectors of block a, block b, block c, and block d as the motion vector of the upper block.

For example, the processor may use an average or a weighted average of motion vectors of blocks adjacent to the top of the target block as the motion vector of the top block.

In an embodiment, the processing unit may derive motion vectors of one or more blocks among block e, block f, block g, and block h, and use a combination of the derived motion vectors as the motion vector of the left-located block.

For example, the combination of derived motion vectors may be an average of the derived motion vectors or a weighted average of the derived motion vectors. Alternatively, the combination of the derived motion vectors may be a result of a calculation formula using the derived motion vectors or a motion vector determination method.

For example, the processing unit may use an average or a weighted average of the motion vector of the block e and the motion vector of the block f as the motion vector of the left position block.

For example, the processing unit may use an average or a weighted average of motion vectors of m uppermost blocks or m lowermost blocks among blocks adjacent to the left of the target block as the motion vector of the left location block. m may be an integer of 2 or more.

For example, the processing unit may use an average or a weighted average of motion vectors of block e, block f, block g, and block h as the motion vector of the left position block.

For example, the processing unit may use an average or a weighted average of motion vectors of blocks adjacent to the left side of the target block as the motion vector of the left position block.

In an embodiment, the processor may perform scaling of the motion vector in deriving a motion vector used for the motion vector of the left location block.

For example, if the POC of the reference picture of the adjacent block in the reference picture list L0 does not match ((POC of the target picture of the target block) - 1) in the reference picture list L0, the processing unit performs scaling of the motion vector of the adjacent block. can In this case, the processor may perform scaling of the motion vector of the adjacent block according to ((POC of the target picture) - 1).

For example, if the POC of the reference picture of the adjacent block in the reference picture list L1 does not match ((POC of the target picture of the target block) + 1) in the reference picture list L1, the processing unit performs scaling of the motion vector of the adjacent block. can In this case, the processor may perform scaling of the motion vector of the adjacent block according to ((POC of the target picture) + 1).

In the above-described embodiment, it has been described that one or more motion vectors of one or more adjacent blocks are used to derive a motion vector of a merge candidate. It may also be considered that one or more motion vectors of one or more adjacent blocks are used to select one or more prediction modes from among a plurality of prediction modes. In other words, the merge candidate may be a virtual block or a derived block for defining a motion vector used to select one or more prediction modes. In addition, the motion vector of the merge candidate may be regarded as a motion vector calculated, determined, or derived based on one or more motion vectors of one or more adjacent blocks.

Referring back to FIG. 15 , as described above, in operation 1520 , the processor may determine the correlation between the induced motion vectors of the reference blocks.

In one embodiment, there may be three reference blocks. The processor may calculate the correlation using motion vectors of the three reference blocks. In the calculation of the correlation, Equation 2 below may be used.

[Equation 2]

In "MV _nm " of the equation, n may indicate an index or number of a reference block. For example, MV ₀ may indicate the first reference block. m may mean an x-coordinate or a y-coordinate of a motion vector. For example, MV _nx may be an x-coordinate of a motion vector of a reference block having an index of n. MV _ny may be a y-coordinate of a motion vector of a reference block having an index of n.

"abs{}" in an expression can represent an absolute value.

For example, the three reference blocks may be the aforementioned first merge candidate, second merge candidate, and third merge candidate.

In an embodiment, the processor may calculate a correlation using motion vectors of two reference blocks. In the calculation of the correlation, Equation 3 below may be used.

[Equation 3]

In an embodiment, the processor may calculate the correlation using motion vectors existing in one reference block. In this case, the reference block may be a block decoded by bi-prediction, and correlation may be calculated using two existing motion vectors. In the calculation of the correlation, Equation 4 below may be used.

[Equation 4]

In "MVN _m " of the equation, N may indicate an index or number of a reference picture list of a reference block. For example, MV0 may indicate the reference picture list No. 0, and m may indicate an x-coordinate or a y-coordinate of a motion vector. For example, MVNx may be the x-coordinate of the motion vector of the N-th reference picture list of the reference block.

"abs{}" in an expression can represent an absolute value.

For example, the reference block may be the aforementioned first merge candidate, second merge candidate, or third merge candidate.

In selecting the prediction mode of the target block, the processor may select one of the template matching mode and the bilateral matching mode as the prediction mode of the target block based on the calculated correlation.

In an embodiment, the processing unit may select one of the template matching mode and the bilateral matching mode as the prediction mode of the target block according to the comparison between the calculated correlation and the threshold.

In an embodiment, when the calculated correlation is greater than the threshold, the processing unit may select the template matching mode as the prediction mode of the target block.

In an embodiment, when the calculated correlation is smaller than the threshold, the processing unit may select the template matching mode as the prediction mode of the target block.

In an embodiment, when the calculated correlation is greater than the threshold, the processing unit may add the template matching mode to one or more prediction modes selected for the target block.

In an embodiment, when the calculated correlation is smaller than the threshold, the processing unit may add the template matching mode to one or more prediction modes selected for the target block.

In an embodiment, when the calculated correlation is greater than the threshold, the processing unit may add the bilateral matching mode to one or more prediction modes selected for the target block.

In an embodiment, when the calculated correlation is smaller than the threshold, the processing unit may add the bilateral matching mode to one or more prediction modes selected for the target block.

In an embodiment, regardless of the calculated correlation, the processing unit may select both the template matching mode and the bilateral matching mode as one or more prediction modes for the target block.

In an embodiment, the threshold may be determined by a user of the encoding apparatus 1200 and/or the decoding apparatus 130 . Alternatively, the threshold may be determined by information related to the target block and/or information related to the reference block.

In one or more prediction modes selected by prediction mode information among a plurality of prediction modes, one of the selected one or more prediction modes may be used for encoding and/or decoding of a target block.

Prediction mode determination information may be used to indicate a prediction mode used for encoding and/or decoding of a target block among one or more selected prediction modes. That is, the prediction mode determination information may indicate a prediction mode for encoding and/or decoding of a target block. The processor may perform encoding and/or decoding of the target block by using the prediction mode indicated by the prediction mode determination information.

In order to determine the prediction mode for decoding the target block, prediction mode determination information for determining the prediction mode may be signaled from the encoding apparatus 1200 to the decoding apparatus 1300 .

When one or more prediction modes are selected from among a plurality of prediction modes according to prediction mode information, etc., prediction mode determination information may be at least partially omitted according to the selected one or more prediction modes.

In other words, the prediction mode determination information may include one or more partial prediction mode determination information, and one or more partial prediction mode determination information in signaling of the prediction mode determination information according to one or more prediction modes selected from among a plurality of prediction modes. At least some of them may be omitted.

In other words, if it can be determined by prediction mode information, etc. that a specified prediction mode among a plurality of prediction modes is excluded from selection, signaling of the prediction mode determination information may be performed so that information related to the excluded prediction mode is omitted. . Alternatively, if it can be determined by prediction mode information or the like that only a specified prediction mode from among a plurality of prediction modes is selected, signaling of the prediction mode determination information may be performed so that information on the specified prediction mode is included.

17 to 19 below show examples of signaling for prediction mode determination information according to an example.

17 illustrates signaling of prediction mode determination information when two prediction modes are selected according to an example.

In FIG. 17 , “1” may represent a first predefined value (eg, 1, logical 1, or true).

“0” may represent a second predefined value (eg, 0, logical 0 or false).

"X" may indicate not signaled.

The prediction mode determination information may include at least one of a merge identifier, a matching prediction identifier, a condition, and a matching mode identifier. For example, the above-described plurality of partial prediction mode determination information may be a merge identifier, a matching prediction identifier, a state and a matching mode identifier. Alternatively, the state may be a coding parameter or prediction mode information of a target block that is not included in the prediction mode determination information.

The merge identifier may indicate whether a merge mode is used. The merge mode may be a premise of selecting one or more prediction modes from among a plurality of prediction modes of the embodiments. That is, only when the merge mode is performed, one or more prediction modes may be selectively selected from among the plurality of prediction modes.

When the merge identifier has a first predefined value, the merge may be performed on the target block. When merging is performed on the target block as the merge identifier has a first predefined value, the prediction mode determination information may include at least one of a matching prediction identifier, a state, and a matching mode identifier.

When the merge identifier has a second predefined value, the merge on the target block may not be performed. When merging is not performed on the target block as the merge identifier has a second predefined value, the matching prediction identifier, the state, and the matching mode identifier may be excluded from the prediction mode determination information. That is, when merging is not performed on the target block, the prediction mode determination information may not include a matching prediction identifier, a state, and a matching mode identifier.

The matching prediction identifier may indicate whether one or more prediction modes are selected from among a plurality of prediction modes according to an embodiment.

When the matching prediction identifier has a first predefined value, one or more prediction modes from among a plurality of prediction modes may be selected using prediction mode information or the like as described above. As the matching prediction identifier has a first predefined value, when one or more prediction modes from among the plurality of prediction modes are selected, the prediction mode determination information may include at least one of a state and a matching mode identifier.

When the matching prediction identifier has a second predefined value, one or more prediction modes may not be selected, and the processing unit may use the specified prediction mode for decoding the target block. For example, the specified prediction mode may be a merge mode. As the matching prediction identifier has a second predefined value, when one or more prediction modes from among the plurality of prediction modes are not selected, the state and the matching mode identifier may be excluded from the prediction mode determination information. That is, when one or more prediction modes are not selected from among the plurality of prediction modes, the prediction mode determination information may not include a state and a matching mode identifier.

The processing unit may select one or more prediction modes from among the plurality of prediction modes using the state. In other words, the number of selected one or more prediction modes may be determined by a state. Depending on the state, the selected one or more prediction modes may be plural or there may be only one.

When the selected one or more prediction modes are plural, a prediction mode to be used for encoding the target block from among the plurality of selected prediction modes may need to be determined.

When a plurality of prediction modes are selected, a matching mode identifier may be required to determine prediction modes used for encoding and/or decoding of a target block from among the plurality of selected prediction modes.

The matching mode identifier may indicate a prediction mode used for encoding and/or decoding of a target block among a plurality of selected prediction modes. A value of the matching mode identifier may be a number or index of a prediction mode used for encoding and/or decoding of a target block among a plurality of selected prediction modes. For example, when the value of the matching mode identifier is L, the prediction mode used for encoding and/or decoding of the target block is the L-th prediction mode or the L+1-th prediction mode among the plurality of selected prediction modes. can

When a plurality of prediction modes are selected, the prediction mode determination information may include a matching mode identifier indicating prediction modes used for encoding and/or decoding of a target block among the plurality of selected prediction modes.

When one prediction mode is selected or when the selected prediction mode is one, the matching mode identifier may be excluded from the prediction mode determination information. That is, when only one prediction mode is selected and the prediction mode used for encoding and/or decoding of the target block can be determined without the matching mode identifier, the prediction mode determination information may not include the matching mode identifier.

In an embodiment, the state may indicate a slice of a target picture of a target block. For example, when the slice of the target picture is a B-slice, the selected one or more prediction modes may include a template matching mode and a bilateral matching mode.

For example, when the selected one or more prediction modes include a template matching mode and a bilateral matching mode, if the value of the matching mode identifier is a first predefined value, the template matching mode is selected for encoding and/or decoding of the target block. It may be the matching mode used. Also, in this case, if the value of the matching mode identifier is a second predefined value, the bilateral matching mode may be a matching mode used for encoding and/or decoding of the target block.

18 illustrates signaling of prediction mode determination information when one prediction mode is selected according to an example.

In FIG. 18 , the functions of the merge identifier and the matching prediction identifier may be the same and/or similar to those described above with reference to FIG. 17 . A duplicate description is omitted.

When the matching prediction identifier has a first predefined value, a prediction mode may be selected from among a plurality of prediction modes using prediction mode information or the like.

For example, a prediction mode selected using prediction mode information or the like may be one template matching mode. If the selected prediction mode is one, a matching mode identifier may not be required. That is, when there is one selected prediction mode, the matching mode identifier may be excluded from the prediction mode determination information. Alternatively, when there is one selected prediction mode, the prediction mode determination information may not include a matching mode identifier.

19 illustrates signaling of prediction mode determination information when one prediction mode is selected according to an example.

In FIG. 19 , the functions of the merge identifier and the matching prediction identifier may be the same and/or similar to those described above with reference to FIG. 17 . A duplicate description is omitted.

When the matching prediction identifier has a first predefined value, a prediction mode may be selected from among a plurality of prediction modes using prediction mode information or the like.

For example, a prediction mode selected using prediction mode information or the like may be one bilateral matching mode. If the selected prediction mode is one, a matching mode identifier may not be required. That is, when there is one selected prediction mode, the matching mode identifier may be excluded from the prediction mode determination information. Alternatively, when there is one selected prediction mode, the prediction mode determination information may not include a matching mode identifier.

The processing unit may identify which information the prediction mode determination information includes and which information does not include using the values of the above-described merge identifier, matching prediction identifier, and/or state.

In addition, the processor may determine a prediction mode used for encoding and/or decoding of the target block by using the values of the above-described merge identifier, matching prediction identifier, state, and/or matching mode identifier.

As described above, a bilateral matching mode and/or a template matching mode may be used for encoding and/or decoding a target block. 20 and 21 , prediction using the bilateral matching mode and prediction using the template matching mode are discussed respectively.

20 illustrates prediction of a target block using a bilateral matching mode according to an example.

In operation 1420, the processing unit may perform prediction on the target block using bilateral matching.

In an embodiment, the processing unit may determine whether to perform bilateral matching according to a slice type. The slice may be a slice of the target block.

For example, the processing unit may perform bilateral matching only when the slice is a B slice. Alternatively, the processing unit may perform bilateral matching only when the slice is a P slice or a B slice.

In an embodiment, in performing bilateral matching, the processing unit may derive a motion vector MV0 using an initial motion vector that may be derived from a target block, and may derive a motion vector MV1 according to the motion vector MV0. have.

The direction of the motion vector MV1 may be opposite to the direction of the derived motion vector MV0, and the motion trajectory of the motion vector MV1 may be the same as that of the derived motion vector MV0. That is, the motion vector MV1 may be a motion vector existing on the same trajectory as the trajectory of the derived motion vector MV0 in a direction opposite to the direction of the derived motion vector MV0.

The initial motion vector may be an initially derived motion vector.

“Ref0” may be reference picture 0 of MV0. “Ref1” may be reference picture 1 of MV1.

TD0 may be a trajectory distance between the target picture and the reference picture 0. TD1 may be a trajectory distance between the target picture and the reference picture 1.

In one embodiment, the initial motion vector may be one or more.

In an embodiment, as shown in FIG. 20 , the processing unit may derive an initial motion vector according to one or more directions of at least one or more motion vectors among MV0 and MV1.

For example, the processor may derive an initial motion vector from the reference picture list L0 with respect to the target block.

For example, the processor may derive an initial motion vector from the reference picture list L1 with respect to the target block.

In performing the bilateral matching, in deriving the initial motion vector for the target block, the processor may construct an initial motion vector candidate list, and select at least one of one or more initial motion vector candidates of the constructed initial motion vector candidate list. An initial motion vector candidate may be used as an initial motion vector.

For example, the processor may use the AMVP mode to construct an initial motion vector candidate list for the target block. The prediction motion vector candidates of the prediction motion vector candidate list of the AMVP mode may be one or more initial motion vector candidates of the initial motion vector candidate list. The processor may add the motion vector prediction candidates of the prediction motion vector candidate list of the AMVP mode to the initial motion vector candidate list.

For example, the processor may use the merge mode to construct an initial motion vector candidate list for the target block. Merge candidates of the merge candidate list of the merge mode may be one or more initial motion vector candidates of the initial motion vector candidate list. The processor may add merge candidates of the merge mode to the initial motion vector candidate list.

For example, the processing unit may configure the matching prediction unidirectional motion vector of the target block as an initial motion vector candidate list. The processing unit may add the matching prediction unidirectional motion vector of the target block to the initial motion vector candidate list.

For example, the processor may configure motion vectors of neighboring blocks of the target block as an initial motion vector candidate list. The processor may add motion vectors of blocks adjacent to the target block to the initial motion vector candidate list.

For example, the processing unit may construct combinations of the above-described motion vectors as an initial motion vector candidate list. The combinations of motion vectors may be N or more. N may be a positive integer. The processing unit may add combinations of the above-described motion vectors to the initial motion vector candidate list.

For example, in constructing the initial motion vector list, the processor may use a motion vector for at least one of a direction of the reference picture list L0 and a direction of the reference picture list L1. The processor may add a motion vector for at least one of a direction of the reference picture list L0 and a direction of the reference picture list L1 to the initial motion vector list.

In an embodiment, in performing bilateral matching, the processor may derive a bidirectional motion vector that best matches the initial motion vector indication block and the opposite block using the initial motion vector list. Here, the initial motion vector indication block may be a block indicated by the initial motion vector. The opposite block may be a block existing on the same trajectory as the trajectory of the initial motion vector indicating block in a direction opposite to the direction of the initial motion vector indicating block. That is, the direction of the initial motion vector block and the direction of the opposite block may be opposite to each other, and the trajectory of the initial motion vector block and the trajectory of the opposite block may be the same.

For example, as shown in FIG. 20 , when a motion vector existing in the initial motion vector list is MV0, the processing unit 1) in a reference picture opposite to that of MV0, 2) on the same trajectory as that of MV0 3) It is possible to derive MV1, which is a motion vector indicating a block that best matches the block indicated by MV0.

In an embodiment, the processing unit may improve the initial motion vector.

For example, the processing unit may search for blocks adjacent to the block indicated by the derived MV0, and may search for blocks adjacent to the block indicated by the derived MV1. The processing unit may improve the initial motion vector to indicate blocks that most closely match each other among neighboring blocks of the block indicated by MV0 and neighboring blocks of the block indicated by MV1.

In an embodiment, in performing bilateral matching, the processor may derive motion information in units of sub-blocks. The motion information may include a motion vector.

In deriving the motion information in units of sub-blocks, the processing unit may use the same method as the above-described method of deriving an initial motion vector in units of blocks.

For example, a sub-block that is a unit of motion information derivation may be a 4x4 block. Alternatively, the sub-block may be an 8x8 block. That is, in deriving the motion information, the reference block may be divided into sub-blocks of a predefined size such as a 4x4 size or an 8x8 size.

In one embodiment, a sub-block may be a block of a combination of one or more predefined sizes. The sub-block may be blocks of one or more sizes of 4x4 size and 8x8 size. For example, the sub-block may be blocks of 4x4 size and blocks of 8x8 size.

In an embodiment, in performing the bilateral matching, the processing unit may define a degree of matching of blocks. In other words, the processing unit may use one of the specified defined methods in determining the degree of matching of blocks.

For example, when the sum of absolute differences (SAD) between the two blocks is the lowest, the processing unit may determine that the two blocks match the best. In other words, the processing unit may determine that the two blocks match better as the SAD between the two blocks is lower.

For example, when the sum of absolute transformed differences (SATD) between the two blocks is the lowest, the processing unit may determine that the two blocks match the best. In other words, the processing unit may determine that the two blocks match better as the SATD between the two blocks is lower.

21 illustrates prediction of a target block using a template matching mode according to an example.

In operation 1420, the processing unit may perform prediction on the target block using template matching.

In an embodiment, the processing unit may determine whether to perform template matching according to a slice type. The slice may be a slice of the target block. For example, the processing unit may perform template matching only when the slice is a B slice. Alternatively, the processing unit may perform template matching only when the slice is a P slice or a B slice.

In an embodiment, in performing template matching, the processing unit may use a neighboring block of the target block as a template. The size and position of the template may be determined in a predefined manner.

For example, the processing unit may use a neighboring block adjacent to the top of the target block as a template.

For example, the processing unit may use a neighboring block adjacent to the left of the target block as a template.

For example, the processing unit may use a neighboring block adjacent to the top or left side of the target block as a template.

For example, the size of the template may be (width, 4) or (4, height). width may be the horizontal size of the target block. height may be the vertical size of the target block.

For example, the size of the template may be (width, 8) or (8, height).

For example, the size of the template may be determined based on the size of the target block. For example, the size of the template may be 1/2 or 1/4 of the size of the target block.

In an embodiment, in performing template matching, the processor may search for a block in a reference picture using a template. In FIG. 21 , “Ref0” may be a reference picture.

The processing unit may search for a block having the same shape and size as that of the template from the reference picture. The processor may derive the motion vector of the target block by using the motion vector for the found block. The processing unit may determine a motion vector for the found block as a motion vector of the target block.

In this case, the direction of the reference picture in which the block is searched and the direction of the reference picture indicated by the motion vector of the target block may be opposite to each other.

For example, the processing unit may search for a block that best matches the template of the target block from the reference picture in the reference picture list L0.

For example, the processing unit may search for a block that best matches the template of the target block from the reference picture in the reference picture list L1.

For example, the processing unit may search for a block using at least one or more of the suggested reference picture lists.

In an embodiment, the processing unit may perform motion vector improvement.

For example, the processing unit may search for neighboring blocks of the block indicated by the current template and the derived motion vector, and motion information to indicate a block that best matches the template among neighboring blocks for which the motion vector is searched can be improved That is, the improved motion information may be a motion vector for a block that best matches the template among neighboring blocks of the block indicated by the derived motion vector.

In an embodiment, in performing template matching, the processor may derive motion information in units of sub-blocks. The motion information may include a motion vector.

In deriving the motion information in units of sub-blocks, the processing unit may use the same method as the method of deriving motion vectors in units of blocks.

For example, a sub-block that is a unit of motion information derivation may be a 4x4 block. Alternatively, the sub-block may be an 8x8 block. That is, in deriving motion information, a block may be divided into sub-blocks of a predefined size, such as a 4x4 size or an 8x8 size.

In one embodiment, a sub-block may be a block of a combination of one or more predefined sizes. The sub-block may be blocks of one or more sizes of 4x4 size and 8x8 size. For example, the sub-block may be blocks of 4x4 size and blocks of 8x8 size.

In an embodiment, in performing template matching, the processing unit may define a degree of matching of blocks. In other words, the processing unit may use one of the specified defined methods in determining the degree of matching of blocks. One of the blocks may be a template.

For example, when the sum of absolute differences (SAD) between the two blocks is the lowest, the processing unit may determine that the two blocks match the best. In other words, the processing unit may determine that the two blocks match better as the SAD between the two blocks is lower.

For example, when the sum of absolute transformed differences (SATD) between the two blocks is the lowest, the processor may determine that the two blocks match the best. In other words, the processing unit may determine that the two blocks match better as the SATD between the two blocks is lower.

22 is a flowchart of a method of predicting a target block and a method of generating a bitstream according to an embodiment.

The method of predicting the target block and the method of generating a bitstream according to the embodiment may be performed by the encoding apparatus 1200 . The embodiment may be a part of a method for encoding a target block or a method for encoding a video.

In operation 2210, the processor 1210 may select a prediction mode. Step 2210 may correspond to step 1410 described above with reference to FIG. 14 .

In operation 2220, the processing unit 1210 may perform prediction using the selected prediction mode. Step 2220 may correspond to step 1420 described above with reference to FIG. 14 .

In operation 2230, the processor 1210 may generate prediction mode determination information. The prediction mode determination information may be generated at least partially in operation 2210 or 2220 .

In operation 2240, the processor 1210 may generate a bitstream.

The bitstream may include information on the encoded target block. For example, the encoded information on the object block may include transform and quantized coefficients of the object block, and may include a coding parameter of the object block. The bitstream may include prediction mode determination information.

The processing unit 1210 may perform entropy encoding on the prediction mode determination information and may generate a bitstream including the entropy-encoded prediction mode determination information.

The processing unit 1210 may store the generated bitstream in the storage 1240 . Alternatively, the communication unit 1220 may transmit the bitstream to the decoding apparatus 1300 .

23 is a flowchart of a method of predicting a target block using a bitstream according to an embodiment.

The method of predicting the target block using the bitstream of the embodiment may be performed by the decoding apparatus 1300 . The embodiment may be a part of a method for decoding a target block or a method for decoding a video.

In operation 2310, the communication unit 1320 may obtain a bitstream. The communication unit 1320 may receive a bitstream from the encoding apparatus 1200 .

The bitstream may include information on the encoded target block. For example, the encoded information on the object block may include transform and quantized coefficients of the object block, and may include a coding parameter of the object block. The bitstream may include prediction mode determination information.

The processing unit 1310 may store the obtained bitstream in the storage 1240 .

In operation 2320, the processing unit 1310 may obtain prediction mode determination information from the bitstream.

The processor 1310 may obtain prediction mode determination information by performing entropy decoding on the entropy-encoded prediction mode determination information of the bitstream.

In operation 2330 , the processor 1310 may select a prediction mode based on the prediction mode determination mode. Step 2330 may correspond to step 1410 described above with reference to FIG. 14 .

In operation 2340, the processing unit 1310 may perform prediction using the selected prediction mode. Step 2340 may correspond to step 1420 described above with reference to FIG. 14 .

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 at the same time as 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 of the flowchart may be deleted without affecting the scope of the present invention. You will understand.

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 computer software field. Examples of the computer-readable recording medium include a hard disk, a magnetic medium such as a floppy disk and a magnetic tape, an optical recording medium such as a CD-ROM, a DVD, and a magneto-optical medium such as a floppy disk. 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 devise 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 (20)

generating a merge list for the target block; and
performing inter prediction on the target block using the merge list
A decryption method comprising The method of claim 1,
The merge list is generated based on information of a plurality of adjacent blocks spatially adjacent to the target block,
The plurality of adjacent blocks includes a first block, a second block, a third block, and a fourth block,
The first block is a leftmost block among a plurality of blocks adjacent to an upper end of the target block,
The second block is a rightmost block among a plurality of blocks adjacent to an upper end of the target block,
The third block is an uppermost block among a plurality of blocks adjacent to the left side of the target block,
The fourth block is a lowermost block among a plurality of blocks adjacent to the left of the target block. 3. The method of claim 2,
The motion vector for the inter prediction is derived based on information on four reference blocks,
The x-coordinate of the rightmost pixels of the four reference blocks is smaller than the x-coordinate of the leftmost pixel of the target block. 3. The method of claim 2,
The merge list is a decoding method commonly used to derive motion information for sub-blocks of a target block. 3. The method of claim 2,
Improvement of motion information of the target block is performed,
The improvement is the decoding method, wherein the motion information is changed to indicate a block adjacent to the block indicated by the motion information. According to claim 1,
The inter prediction is performed based on a plurality of motion vectors of a plurality of reference blocks. According to claim 1,
Two merge candidates of the merge list are used for the inter prediction,
A decoding method in which a merge index indicating each of the two merge candidates is obtained from a bitstream. generating a merge list for the target block; and
Steps to create a merge index
including,
The merge index indicates a merge candidate used for decoding the target block using inter prediction among the merge candidates of the merge list. 9. The method of claim 8,
generating a merge identifier indicating whether a merge mode is used in the decoding;
further comprising,
The merge list is generated based on information of a plurality of adjacent blocks spatially adjacent to the target block,
The plurality of adjacent blocks includes a first block, a second block, a third block, and a fourth block,
The first block is a leftmost block among a plurality of blocks adjacent to an upper end of the target block,
The second block is a rightmost block among a plurality of blocks adjacent to an upper end of the target block,
The third block is an uppermost block among a plurality of blocks adjacent to the left side of the target block,
The fourth block is a lowermost block among a plurality of blocks adjacent to the left of the target block. 10. The method of claim 9,
The motion vector for the inter prediction is derived based on information on four reference blocks,
The x-coordinate of the rightmost pixels of the four reference blocks is smaller than the x-coordinate of the leftmost pixel of the target block. 9. The method of claim 8,
generating a merge identifier indicating whether a merge mode is used in the decoding;
further comprising,
In the decoding, improvement of motion information of the target block is performed,
The improvement is that the motion information is changed to indicate a block adjacent to the block indicated by the motion information. 9. The method of claim 8,
In the decoding, the inter prediction is performed based on a plurality of motion vectors of a plurality of reference blocks. 9. The method of claim 8,
In the decoding, two merge candidates of the merge list are used for the inter prediction,
A bitstream encoding method including a merge index indicating each of the two merge candidates. A recording medium for recording a bitstream generated by the encoding method according to claim 8. A computer-readable recording medium for storing a bitstream, comprising:
The bitstream is
Merge identifier indicating whether merge mode is used for the target block
including,
When the merge identifier indicates that the merge mode is used, a merge list for the target block is generated,
A computer-readable recording medium on which inter prediction is performed on the target block using the merge list. 16. The method of claim 15,
The merge list is generated based on information of a plurality of adjacent blocks spatially adjacent to the target block,
The plurality of adjacent blocks includes a first block, a second block, a third block, and a fourth block,
The first block is a leftmost block among a plurality of blocks adjacent to an upper end of the target block,
The second block is a rightmost block among a plurality of blocks adjacent to an upper end of the target block,
The third block is an uppermost block among a plurality of blocks adjacent to the left side of the target block,
The fourth block is a lowermost block among a plurality of blocks adjacent to the left side of the target block. 17. The method of claim 16,
The motion vector for the inter prediction is derived based on information on four reference blocks,
The x-coordinate of the rightmost pixels of the four reference blocks is smaller than the x-coordinate of the leftmost pixel of the target block. 16. The method of claim 15,
Improvement of motion information of the target block is performed,
The improvement is that the motion information is changed to point to a block adjacent to the block pointed to by the motion information. 16. The method of claim 15,
The inter prediction is performed based on a plurality of motion vectors of a plurality of reference blocks. 16. The method of claim 15,
Two merge candidates of the merge list are used for the inter prediction,
A merge index indicating each of the two merge candidates is obtained from a bitstream.

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