KR102402539B1 - Method and apparatus for bi-directional intra prediction - Google Patents

Abstract

A video decoding method, a decoding apparatus, an encoding method, and an encoding apparatus are disclosed. Encoding and decoding are performed on the target block using intra prediction. Intra prediction is intra prediction using bidirectional intra prediction and residual mode. In the bidirectional intra prediction, the prediction value of the target pixel of the target block is determined based on reference pixels according to the bidirectional directions of the bidirectional intra prediction. In intra prediction using the residual mode, the residual mode is the remaining intra prediction mode except for the MPMs in the MPM list.

Description

Bi-directional intra prediction method and apparatus

The following embodiments relate to a video decoding method, a decoding apparatus, an encoding method, and an encoding apparatus, and to a video decoding method, a decoding apparatus, an encoding method, and an encoding apparatus using bi-directional intra prediction.

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 picture 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 apparatus and method for encoding/decoding an image include an inter prediction technology, an intra prediction technology, an entropy encoding technology, etc. to perform encoding/decoding on a high-resolution and high-definition image. can be used The inter prediction technique may be a technique of predicting a value of a pixel included in a target 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 target picture by using information on the pixel in the target 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.

In intra prediction, various detailed techniques have been developed, and accuracy and efficiency of prediction can be improved by applying these detailed techniques.

An embodiment may provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using bidirectional intra prediction.

An embodiment may provide an encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using a residual mode.

In one aspect, the method comprising: determining an intra prediction mode to be applied to decoding of a target block; and performing intra prediction on the target block using the determined intra prediction mode, wherein the intra prediction mode is a bidirectional intra prediction mode, and the intra prediction is bidirectional intra prediction.

The bidirectional intra prediction mode may be determined based on availability of pixels of neighboring blocks located in a specified direction with respect to the target block.

The bidirectional intra prediction mode may be determined based on a prediction mode of a neighboring block of the target block.

The two directions of the bidirectional intra prediction may be two directions in the form of a straight line consisting of directions opposite to each other.

A virtual neighboring pixel may be generated with respect to a specified direction with respect to the target block, and the bidirectional intra prediction may be performed on the target block using the virtual neighboring pixel.

The specified direction may be one or more of a right direction and a bottom direction.

The prediction value of the target pixel of the target block may be derived using pixels of neighboring blocks in both directions of the bidirectional intra prediction.

The prediction value of the target pixel of the target block may be derived using a weight according to a distance between each pixel of the pixels of neighboring blocks of the bidirectional intra prediction and the target pixel.

The prediction value of the target pixel of the target block may be derived using weights of the bidirectional directions of the bidirectional intra prediction.

Whether the bidirectional intra prediction mode is used for the target block may be determined using a unidirectional/bidirectional discrimination indicator and an intra prediction mode indicator.

Two directions of the bidirectional intra prediction may be determined by two directions indicated by two intra prediction mode indicators.

One intra prediction mode indicator may indicate one of a direction of unidirectional intra prediction and directions of the bidirectional intra prediction.

One of unidirectional intra prediction and the bidirectional intra prediction may be selected according to availability of a reference pixel in a direction corresponding to the direction indicated by the intra prediction mode indicator.

It may be determined which one of the unidirectional intra prediction and the bidirectional intra prediction is to be used for the entire target block.

Which of the unidirectional intra prediction and the bidirectional intra prediction is to be used may be determined for each pixel of the pixels of the target block.

For the first direction and the second direction of the bidirectional intra prediction, when the reference pixel for the first direction or the reference pixel for the second direction is not available, the value of the unavailable reference pixel using padding can be created.

The prediction value of the target pixel of the target block may be determined using at least one of reference pixels in the two prediction directions of the bidirectional intra prediction mode.

A weight may be applied to each reference pixel of the reference pixels.

The residual mode indicator may indicate a residual mode used for the intra prediction of the target block among residual modes.

The residual modes may be intra prediction modes other than MPMs in a Most Probable Mode (MPM) list.

The intra prediction mode may be determined based on a plurality of different lists.

In another aspect, the method comprising: determining an intra prediction mode to be applied to decoding of a target block; and performing intra prediction on the target block using the determined intra prediction mode, wherein the intra prediction mode is a bidirectional intra prediction mode, and the intra prediction is bidirectional intra prediction.

In another aspect, in a computer-readable recording medium storing a bitstream for decoding an image, the bitstream includes encoded information on the target block, and an intra prediction mode to be applied to decoding of the target block is determined, and intra prediction is performed on the target block using the encoded information on the target block and the determined intra prediction mode.

An encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using bidirectional intra prediction are provided.

An encoding apparatus, an encoding method, a decoding apparatus, and a decoding method using a residual mode are provided.

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.
3 is a diagram schematically illustrating a structure of an image segmentation when an image is encoded and decoded.
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 illustrates division of a block according to an example.
7 is a diagram for explaining an embodiment of an intra prediction process.
8 is a diagram for explaining a position of a reference sample used in an intra prediction process.
9 is a diagram for explaining an embodiment of an inter prediction process.
10 illustrates spatial candidates according to an example.
11 illustrates an order of adding motion information of spatial candidates to a merge list according to an example.
12 illustrates a process of transformation and quantization according to an example.
13 illustrates diagonal scanning according to an example.
14 illustrates horizontal scanning according to an example.
15 illustrates vertical scanning according to an example.
16 is a structural diagram of an encoding apparatus according to an embodiment.
17 is a structural diagram of a decoding apparatus according to an embodiment.
18 is a flowchart of a bidirectional intra prediction method according to an embodiment.
19 illustrates a unidirectional intra prediction mode according to an example.
20 illustrates a bidirectional intra prediction mode according to an example.
21 illustrates a bidirectional intra prediction mode using virtual neighboring pixels according to an example.
22 illustrates that bidirectional intra prediction is derived and selected from a direction of an intra prediction mode indicator according to an example.
23 illustrates generation of virtual peripheral pixels according to an example.
24 illustrates the creation of another virtual surrounding pixel using virtual surrounding pixels according to an example.
25 illustrates generation of a lower right virtual peripheral pixel and a middle virtual peripheral pixel according to an example.
26 illustrates bidirectional intra prediction according to an example.
27 illustrates bidirectional intra prediction using virtual neighboring pixels according to an example.
28 illustrates bidirectional intra prediction using a distance between a neighboring pixel and a target pixel according to an example.
29 illustrates bidirectional intra prediction using a distance between a virtual neighboring pixel and a target pixel according to an example.
30 illustrates determination of an intra prediction mode using a residual mode according to an embodiment.
31 illustrates the determination of the intra prediction mode using the residual mode and inducing the MPM after determining whether to use the MPM according to an embodiment.
32 shows blocks for derivation of MPM candidates according to an example.
33 illustrates binarization of a residual mode indicator according to an example.
34 is a flowchart of a method of predicting a target block and a method of generating a bitstream according to an embodiment.
35 is a flowchart of a method of predicting a target block using 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, it 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 [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] Reference is made to the accompanying drawings, which illustrate specific embodiments by way of example. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that various embodiments are different, but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein with respect to one embodiment may be 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 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 the other component does not exist between 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. Insofar 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 the exemplary embodiments does not exclude components other than the above specific configuration, and the additional configuration is 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 "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof. That is, the description of "including" a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and it means that additional configurations may also be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings in order to enable those of ordinary skill in the art to easily implement the embodiments. 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 with the same meaning, 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. Also, the target image may be an input image input to the encoding apparatus or 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 target block may be an encoding target block to be encoded and/or a decoding target 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 representing 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. In other words, a unit may be a specified area within one image. One image may be divided into a plurality of units. Alternatively, the unit may refer to the divided part when an image is divided into subdivided parts and encoding or decoding is performed on the divided parts.

- In video encoding and decoding, a predefined process for a 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 mean 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.

- Also, the unit information may include at least one of a unit type, a unit size, a unit depth, an encoding order of the unit, and a decoding order of the unit. For example, the type of unit may indicate one of CU, PU, residual unit and TU, and the like.

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

Depth: The 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 depth related to the depth of the 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 depth. Since the depth indicates the number and/or degree to which the unit is divided, 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.

- QT depth may indicate a depth for quad division. The BT depth may represent the depth for binary segmentation. The TT depth may represent a depth for ternary division.

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 has a quad tree (QT), a binary tree (BT) and a ternary tree (TT) to configure subunits such as a coding unit, a prediction unit, and a transform unit. It may be partitioned using one or more partitioning schemes.

- 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): A 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: A neighboring block may mean a block adjacent to a target block. The neighboring block may mean a reconstructed neighboring block.

- Hereinafter, the terms "adjacent block" and "adjacent block" may be used with the same meaning, and may be used interchangeably.

Spatial neighbor block: A spatial neighbor block may be a block spatially adjacent to a target block. The neighboring blocks may include spatial neighboring blocks.

- The target block and spatial neighboring blocks may be included in the target picture.

- The spatially neighboring block may refer to a block having a boundary contacting the target block or a block located within a predetermined distance from the target block.

- The spatial 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.

Temporal neighbor block: The temporal neighbor block may be a block temporally adjacent to the target block. The neighboring blocks may include temporal neighboring blocks.

- The temporal neighboring block may include a co-located block (col block).

- The collocated block may be a block in an already reconstructed co-located 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 picture. Alternatively, the location of the collocated block in the collocated picture may be the same as the location of the target block in the target picture. The collocated picture may be a picture included in the reference picture list.

- The temporal neighboring block may be a block temporally adjacent to the spatial neighboring block of the target block.

Prediction unit: It 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: may refer to 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 (spatial) neighboring unit or a temporal (temporal) neighboring unit for the target unit.

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

- The reconstructed temporal peripheral 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 target picture or may correspond to the location of the target unit in the target picture.

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

In addition, the parameter set may include slice header information and tile header information.

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: A parameter set may correspond to header information among structures in a 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 for 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 target image and the reference image.

- For example, MV may 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: A 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: A merge candidate may mean 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 prediction type information, 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, the quantization parameter may mean a value used when generating a transform coefficient by scaling a 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 target unit.

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 by performing transformation in the encoding apparatus. 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 quantized level or a quantized transform coefficient level generated by applying quantization to a transform coefficient or a residual signal 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 to be subjected to 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 refer to a matrix used in a quantization process or inverse quantization process to improve subjective image quality 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.

Most Probable Mode (MPM): The MPM may indicate an intra prediction mode that is highly likely to be used for intra prediction of a target block.

The encoding apparatus and the decoding apparatus may determine one or more MPMs based on a coding parameter related to the target block and an attribute of an entity related to the target block.

The encoding apparatus and the decoding apparatus may determine one or more MPMs based on the intra prediction mode of the reference block. The reference block may be plural. The plurality of reference blocks may include a spatial neighboring block adjacent to the left side of the target block and a spatial neighboring block adjacent to an upper end of the target block. That is, one or more different MPMs may be determined according to which intra prediction modes are used for the reference blocks.

One or more MPMs may be determined in the same manner by the encoding apparatus and the decoding apparatus. That is, the encoding apparatus and the decoding apparatus may share the MPM list including the same one or more MPMs.

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

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

Since the MPM list is determined in the same way by the encoding apparatus and the decoding apparatus, the MPM list itself may not need to be transmitted from the encoding apparatus to the decoding apparatus.

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

MPM use indicator: The MPM use indicator may indicate whether the MPM use mode is used for prediction of a target block. The MPM use mode may be a mode in which an MPM to be used for intra prediction for a target block is determined using an MPM list.

The MPM usage indicator may be signaled from the encoding device to the decoding device.

Signaling: Signaling may indicate that information is transmitted from an encoding device to a decoding device. Alternatively, signaling may mean including information in a bitstream or a recording medium. Information signaled by the encoding apparatus may be used by 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, quantizing, or transforming and quantizing a difference between the original signal and the predicted signal. The residual block may be a residual signal for each block.

The transform unit 130 may generate a transform coefficient by performing a transform on the residual block, and may output the generated transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing transform on the residual block.

The conversion unit 130 may use one of a plurality of predefined conversion methods in performing the conversion.

The plurality of predefined transform methods may include a discrete cosine transform (DCT), a discrete sine transform (DST), and a Karhunen-Loeve transform (KLT)-based transform. have.

A transform method used for transforming the residual block may be determined according to at least one of coding parameters for the target block and/or the neighboring block. For example, the transform method may be determined based on at least one of an inter prediction mode for a PU, an intra prediction mode for a PU, a size of a TU, and a shape of the TU. Alternatively, transformation information indicating a transformation method may be signaled from the encoding apparatus 100 to the decoding apparatus 200 .

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.

When entropy encoding is applied, a small number of bits may be allocated to a symbol having a high probability of occurrence, and a large number of bits may be allocated to a symbol having a low probability of occurrence. 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 encoder 150 performs the entropy encoding, such as exponential golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Coding (Context-Adaptive Binary). 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 the quantized 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.

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.

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 or not the tree is split in the form of a binary tree (horizontal or vertical), the splitting form of the binary tree (symmetrical or asymmetrical split), whether a unit/block is split in a ternary tree form Represented information, splitting direction (horizontal direction or vertical direction) in the form of a ternary tree, prediction method (intra prediction or inter prediction), intra prediction mode/direction, reference sample filtering method, prediction block filtering method, prediction block boundary filtering method, filtering filter tap, filter coefficient of filtering, inter prediction mode, motion information, motion vector, reference picture index, inter prediction direction, inter prediction indicator, reference picture list, reference image, motion vector predictor, motion vector prediction candidate, motion vector candidate List, information indicating whether to use merge mode, merge candidate, merge candidate list, information indicating whether to use skip mode, type of interpolation filter, filter tap of interpolation filter, filter coefficient of interpolation filter, motion Vector size, motion vector representation accuracy, transform type, transform size, information indicating whether to use a first-order transformation, information indicating whether to use an additive (second-order) transformation, primary transformation index, secondary transformation index, residual Information indicating the presence or absence of a signal, a coded block pattern, a coded block flag, a quantization parameter, a quantization matrix, information about an intra-loop filter, whether to apply an intra-loop filter information about, intra-loop filter coefficients, intra-loop filter tap, intra-loop filter shape/form, information indicating whether to apply a deblocking filter, deblocking filter coefficients, deblocking filter tap, deblocking filter strength, deblocking filter shape/form Status, information indicating whether to apply adaptive sample offset, adaptive sample offset value, adaptive sample offset category, adaptive sample offset type, whether to apply adaptive in-loop filter, adaptive In-loop filter coefficients, adaptive in-loop filter 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, image display/output order, slice identification information, slice type, slice division information, tile identification information, At least one of a tile type, tile division information, picture type, bit depth, information on a luminance signal, and information on a chrominance signal, a combined form, or statistics may be included in the coding parameter. The prediction method may indicate one of an intra prediction mode and 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. The residual block may be a residual signal for the block.

Here, signaling 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 including, and the decoding apparatus 200 performs entropy decoding on the entropy-coded flag or entropy-encoded index extracted from the bitstream, thereby meaning obtaining 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. When the deblocking filter is applied to the target block, one of a strong filter and a weak filter may be applied to the target block according to the required strength of deblocking filtering.

Also, when vertical filtering and horizontal filtering are performed on the target block, horizontal filtering and vertical filtering may be performed in parallel.

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. In order to perform offset correction on an image, a method of dividing pixels included in an image into a certain number of regions, determining a region to be offset among the divided regions, and applying the offset to the determined region may be used. Also, a method of applying an offset in consideration of edge information of each pixel of an image may be used.

The ALF may perform filtering based on a value obtained by comparing the reconstructed image and the original image. After dividing pixels included in an image into predetermined groups, a filter to be applied to each divided group may be determined, and filtering may be performed differentially for each group. With respect to the luminance signal, 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. Alternatively, irrespective of the characteristics of the block, a fixed form of ALF may be applied to the 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 a switch 245 . , an adder 255 , a filter unit 260 , and a reference picture buffer 270 .

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 the intra mode or the inter mode according to the prediction mode used for decoding may be performed by the switch 245 . When the prediction mode used for decoding is the intra mode, the switch 245 may be switched to the intra mode. When the prediction mode used for decoding is the inter mode, the switch 245 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 transform coefficient 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 entropy encoding method described above.

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

For example, the coefficients may be changed into a two-dimensional block form by scanning the coefficients of the block using the upper right diagonal scan. Alternatively, according to the size of the block and/or the intra prediction mode, which scan among the upper right diagonal scan, the vertical scan, and the horizontal scan is to be used may be determined.

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 an 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 quantizer 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 according to

The reconstructed residual block and the prediction block may be added via 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 image. The reconstructed image may be a picture including the reconstructed block.

The reconstructed image passing through the filter unit 260 may be output by the encoding apparatus 100 and may be used by the encoding apparatus 100 .

The reconstructed image passing through the filter unit 260 may be stored as a reference picture 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 picture may be an image composed of reconstructed blocks that have passed through the filter unit 260 . The stored reference picture may be used for inter prediction later.

3 is a diagram schematically illustrating a structure of an image segmentation when an image is encoded and decoded.

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 into units of a largest coding unit (LCU). For each LCU, a partition structure may be determined. 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. When a CU is split, CUs generated by splitting may have a depth increased by 1 from the depth of the split CU.

The division structure may mean a distribution of CUs for efficiently encoding an image in the LCU 310 . This 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, 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 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.

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, a value of partition information of a CU that is not split may be 0, and a value of partition information of a CU that is 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 a CU having a size of 32x32 is horizontally divided into two CUs, the sizes of the divided two CUs may be 32x16. When one CU is split into two CUs, it can be said that the CU is split in a binary-tree form.

Both the quad-tree type division and the binary-tree type division are applied to the LCU 310 of FIG. 3 .

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.

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

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 basic 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 a PU.

A CU may not be split into PUs. When the CU is not divided into PUs, the size of the CU and the size of the PU may be the same.

In skip mode, there may not be a split in a CU. In the skip mode, the 2Nx2N mode 410 in which PU and CU sizes are the same without division may be supported.

In the inter mode, eight 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 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 that 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.

Which mode of the 2Nx2N mode 410 and the NxN mode 425 the PU is coded by 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 an NxN-sized PU 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 .

The encoding apparatus 100 may determine which of the 2Nx2N PU and the NxN PUs to be encoded based on a comparison of the rate-distortion cost of the 2Nx2N PU and the rate-distortion costs of the NxN PUs.

One CU may be divided into one or more PUs, and a PU may also be divided into a plurality of PUs.

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

For example, when one PU is divided into two PUs, the horizontal size or vertical size of each PU of the two PUs generated by the division is half the horizontal size or half the vertical size of the PU before the division, respectively can When a PU of a size of 32x32 is vertically split into two PUs, the sizes of the split two PUs may be 16x32. When a PU of a size of 32x32 is horizontally divided into two PUs, the sizes of the two PUs divided may be 32x16. When one PU is split into two PUs, it can be said that the PU is split in a binary-tree form.

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 basic unit used for transform, quantization, inverse transform, inverse quantization, entropy encoding, and entropy decoding processes within a CU.

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

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 configured with TUs of various sizes.

When one CU is split two or more times, the CU can be considered to be split recursively. Through division, one CU may be composed of TUs having various sizes.

Alternatively, one CU may be divided into one or more TUs based on the number of vertical and/or horizontal lines dividing the CU.

A CU may be divided into symmetrical TUs and may be divided into asymmetrical TUs. For splitting into asymmetric TUs, information on the size and/or shape of a TU may be signaled from the encoding apparatus 100 to the decoding apparatus 200 . Alternatively, the size and/or shape of the TU may be derived from information on the size and/or shape of the CU.

A CU may not be split into TUs. When a CU is not divided into TUs, the size of the CU and the size of the TU may be the same.

One CU may be divided into one or more TUs, and a TU may also be divided into a plurality of TUs.

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

For example, when one TU is divided into two TUs, the horizontal size or vertical size of each TU of the two TUs generated by the division is half the horizontal size or half the vertical size of the TU before division, respectively. can When a TU having a size of 32x32 is vertically split into two TUs, the sizes of the split two TUs may be 16x32. When a TU having a size of 32x32 is horizontally divided into two TUs, the sizes of the divided two TUs may be 32x16. When one TU is split into two TUs, it can be said that the TU is split in a binary-tree form.

6 illustrates division of a block according to an example.

In the process of encoding and/or decoding an image, a target block may be divided as shown in FIG. 6 .

For segmentation of the target block, an indicator indicating segmentation information may be signaled from the encoding apparatus 100 to the decoding apparatus 200 . The division information may be information indicating how the target block is divided.

Split information includes a split flag (hereinafter referred to as "split_flag"), a quad-binary flag (hereinafter referred to as "QB_flag"), a quad tree flag (hereinafter referred to as "quadtree_flag"), a binary tree flag (hereinafter referred to as "binarytree_flag"). It may be at least one of ") and a binary type flag (hereinafter, indicated as "Btype_flag").

split_flag may be a flag indicating whether a block is split. For example, a value of 1 of split_flag may indicate that a block is split. A value of 0 of split_flag may indicate that a block is not split.

QB_flag may be a flag indicating in which form the block is divided among a quad tree form and a binary tree form. For example, a value of 0 of QB_flag may indicate that the block is divided in a quad tree form. A value of 1 of QB_flag may indicate that the block is divided in a binary tree form. Alternatively, a value of 0 of QB_flag may indicate that the block is divided in the form of a binary tree. A value of 1 of QB_flag may indicate that the block is divided in a quad tree form.

quadtree_flag may be a flag indicating whether a block is divided in a quad tree form. For example, a value of 1 of quadtree_flag may indicate that a block is divided in a quadtree form. A value of 0 of quadtree_flag may indicate that the block is not divided in a quadtree form.

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

Btype_flag may be a flag indicating whether a block is divided into vertical division or horizontal division when the block is divided in a binary tree form. For example, a value of 0 of Btype_flag may indicate that the block is divided in the horizontal direction. A value of 1 of Btype_flag may indicate that the block is divided in the vertical direction. Alternatively, a value of 0 of Btype_flag may indicate that the block is partitioned in the vertical direction. A value of 1 of Btype_flag may indicate that the block is divided in the horizontal direction.

For example, partition information for the block of FIG. 6 may be derived by signaling at least one of quadtree_flag, binarytree_flag, and Btype_flag as shown in Table 1 below.

[Table 1]

For example, split information for the block of FIG. 6 may be derived by signaling at least one of split_flag, QB_flag, and Btype_flag as shown in Table 2 below.

[Table 2]

The partitioning method may be limited only to a quad tree, or only to a binary tree, depending on the size and/or shape of the block. When this restriction is applied, split_flag may be a flag indicating whether to split in a quad tree form or a flag indicating whether to split in a binary tree form. The size and shape of the block may be derived according to the depth information of the block, and the depth information may be signaled from the encoding apparatus 100 to the decoding apparatus 200 .

When the size of the block falls within a specified range, only the quad tree type division may be possible. For example, the specified range may be defined by at least one of a maximum block size and a minimum block size that can only be partitioned in the form of a quad tree.

Information indicating the maximum block size and/or the minimum block size that can be split only in the form of a quote tree may be signaled from the encoding apparatus 100 to the decoding apparatus 200 through a bitstream. In addition, such information may be signaled with respect to at least one unit of a video, a sequence, a picture, and a slice (or segment).

Alternatively, the maximum block size and/or the minimum block size may be fixed sizes predefined in the encoding apparatus 100 and the decoding apparatus 200 . For example, when the size of a block is greater than or equal to 64x64 and less than or equal to 256x256, only quad tree division may be possible. In this case, split_flag may be a flag indicating whether to split into a quad tree form.

When the size of a block falls within a specified range, only binary tree-type partitioning may be possible. Here, for example, the specified range may be defined by at least one of a maximum block size and a minimum block size in which only binary tree-type partitioning is possible.

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

Alternatively, the maximum block size and/or the minimum block size may be fixed sizes predefined in the encoding apparatus 100 and the decoding apparatus 200 . For example, when the size of a block is greater than or equal to 8x8 and less than or equal to 16x16, only binary tree partitioning may be possible. In this case, split_flag may be a flag indicating whether to split into a binary tree form.

The division of a block may be limited by the previous division. For example, when a block is divided in the form of a binary tree to generate a plurality of divided blocks, each divided block may be further divided only in the form of a binary tree.

When the horizontal size or vertical size of the divided block corresponds to a size that cannot be further divided, the above-described indicator may not be signaled.

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

Arrows outward from the center of the graph of FIG. 7 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 target block based on information on samples in the target 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 square-shaped block having a size such as 2x2, 4x4, 8x8, 16x16, 32x32 or 64x64, or a rectangular block having a size such as 2x8, 4x8, 2x16, 4x16 and 8x16. have.

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 may have may be a predefined fixed value, or may be 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. 7 .

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

The directional modes may be prediction modes having a specific direction or a specific angle.

The intra prediction mode may be expressed by at least one of a mode number, a mode value, 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. For example, the number of intra prediction modes may be fixed to either 35 or 67 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, as the size of a block increases, the number of intra prediction modes may increase. Alternatively, as the size of the block increases, the number of intra prediction modes may decrease. When the block size is 4x4 or 8x8, the number of intra prediction modes may be 67. When the size of the block is 16x16, the number of intra prediction modes may be 35. When the block size is 32x32, the number of intra prediction modes may be 19. When the size of the block is 64x64, the number of intra prediction modes may be 7.

For example, the number of intra prediction modes may be different depending on whether the color component is a luma signal or a chroma signal. 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. For example, in the case of a horizontal mode having a mode value of 10, prediction may be performed in a horizontal 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. 7 , 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 in which the mode value is one of 2, 3, 4, 5, 6, 7, 8, and 9 may be horizontal bottom modes 616 .

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 mode may include an angular mode. Modes other than the DC mode and the planar mode among the plurality of intra prediction modes may be a directional mode.

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

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. When there is a sample that cannot be used as a reference sample of the target 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 a value generated by copying and/or interpolation is replaced with a sample value of a sample, the sample can be used as a reference sample 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.

The type of filter applied to at least one of the reference sample and the prediction sample may vary according to at least one of an intra prediction mode of the target block, the size of the target block, and the shape of the target block. The types of filters may be classified according to at least one of the number of filter taps, values of filter coefficients, and filter strengths.

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. In addition, filtering using values of reference samples may be performed on specified rows or specified columns in the target block. The specified rows may be one or more top rows adjacent to the reference sample. The specified columns may be one or more left columns adjacent to the reference sample.

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 the intra prediction mode 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 blocks are different from each other, information on the intra prediction mode of the target block may be encoded and/or decoded using entropy encoding and/or decoding.

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

8 illustrates a position of a reference sample used for intra prediction of a target block. Referring to FIG. 8 , the reconstructed reference samples used for intra prediction of a target block include lower-left reference samples 831 , left reference samples 833 , and upper-left reference samples 833 , left) a corner reference sample 835 , above reference samples 837 , and above-right reference samples 839 , and the like.

For example, the left reference samples 833 may mean a reconstructed reference pixel adjacent to the left side of the target block. The upper reference samples 837 may mean a reconstructed reference pixel adjacent to the upper end of the target block. The upper left corner reference sample 835 may mean a reconstructed reference pixel located in the upper left corner of the target block. Also, the lower left reference samples 831 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 833 . The upper right reference samples 839 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 837 .

When the size of the target block is NxN, there may be N number of lower left reference samples 831 , left reference samples 833 , upper reference samples 837 , and upper right reference samples 839 , respectively.

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 with respect to 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 837 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, top reference samples 837 adjacent to the top of the target block may be used for intra prediction. Also, values of pixels in one row of the prediction block may be the same as values of the upper reference samples 837 .

For example, when the intra prediction mode of the target block is a horizontal mode having a mode value of 10, left reference samples 833 may be used for intra prediction. When the intra prediction mode is the horizontal mode, the value of the pixel of the prediction block may be the value of the reference sample located horizontally to the left with respect to the pixel. Accordingly, left reference samples 833 adjacent to the left of the target block may be used for intra prediction. Also, values of pixels in one column of the prediction block may be the same as values of left reference samples 833 .

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 833, the upper left corner reference sample 835, and at least some of the upper reference samples 837. 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 diagonally with respect to the pixel.

In addition, when an intra prediction mode having a mode value of 27, 28, 29, 30, 31, 32, 33, or 34 is used, at least some of the upper right reference samples 839 may be used for intra prediction.

Also, when an intra prediction mode having a mode value of 2, 3, 4, 5, 6, 7, 8, or 9 is used, at least some of the lower left reference samples 831 may be used for intra prediction.

Also, when an intra prediction mode having a mode value of one of 11 to 25 is used, the upper left corner reference sample 835 may be used for intra prediction.

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 pixel position 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 the distance between a pixel of a prediction block and a reference sample is greater. Discontinuity may occur between a prediction block generated by such a prediction error and the like and a neighboring block.

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.

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

The rectangle shown in FIG. 9 may represent an image (or a picture). Also, an arrow in FIG. 9 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 and/or decoded 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.

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.

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

A 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, spatial candidates include 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 location 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. Below, 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 spatial candidate, a motion vector of a temporal candidate, and a zero vector may be determined and used as a prediction 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.

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

Hereinafter, the terms “prediction motion vector candidate list” and “AMVP candidate list” may be used interchangeably and may be used interchangeably.

The spatial 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.

Temporal candidates 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 prediction of a motion vector. 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 for the target block from among 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.

Hereinafter, the terms “prediction motion vector index” and “AMVP index” may be used with the same meaning, and may be used interchangeably.

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 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. An MVD may be used to indicate a difference between a motion vector to be actually used for inter prediction of a target block and a prediction motion vector. 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. In other words, 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 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 of the reconstructed neighboring units motion information 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. The spatial neighboring block may include a left neighboring block and an upper neighboring 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.

Merge candidates may be specified modes for deriving inter prediction information. The merge candidate may be information indicating a specified mode for deriving inter prediction information. Inter prediction information of the target block may be derived according to the specified mode indicated by the merge candidate. In this case, the specified mode may include a process of deriving a series of inter prediction information. This specified mode may be an inter prediction information derivation mode or a motion information derivation mode.

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

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

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

That is, 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 the merge for each block partition, 2) which block among blocks that are spatial and/or temporal candidates for the 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 a residual block for encoding of a 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. A 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.

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

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

The decoding apparatus 200 may perform prediction on the target block by using a merge candidate indicated by a merge index among 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 directly applied to a target block. 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 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 “merge/skip candidate list”.

Alternatively, the skip mode may use a different candidate list 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 a 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 above-described merge index.

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) Skip mode inter prediction using inter prediction information

The decoding apparatus 200 may perform prediction on the target block by using a merge candidate indicated by a skip index among 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 target picture to which the target block belongs.

A motion vector for specifying the pre-reconstructed region may be used. 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 target picture may exist 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 value of the reference picture index is 0 or the last position.

When the target picture exists at 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 a 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-described 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.

10 illustrates spatial candidates according to an example.

In Fig. 10, 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 upper end 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.

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

11 , 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.

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

Step 1) Available spatial candidates among 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, when motion information of an available spatial candidate overlaps with other motion information already present 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, when 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 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 more than one 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 video encoding/decoding fields.

In this case, if 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 pieces of zero vector motion information may be different from each other. For example, the value of the reference picture index of the first zero vector motion information may be 0. The value of the reference picture index of the second zero vector motion information may be 1.

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 indicated 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) Available spatial candidates among 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 predicted motion vector candidate list, the motion information may not be added to the predicted 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 pieces of 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.

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

As shown in FIG. 12 , a quantized level may be generated by performing a transform 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 residual signal may be transformed into the frequency domain through a transform process that is part of the quantization process.

The transform kernel used for the transform may include various DCT kernels such as Discrete Cosine Transform (DCT) type 2 (DCT-II) and a Discrete Sine Transform (DST) kernel. .

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

DCT type and DST type adaptively used for 1D conversion may include DCT-V, DCT-VIII, DST-I and DST-VII in addition to DCT-II as shown in Table 3 below.

[Table 3]

As shown in Table 3, a transform set may be used in deriving a DCT type or a DST type to be used for transformation. Each transform set may include a plurality of transform candidates. Each transformation candidate may be a DCT type or a DST type.

Table 4 below shows an example of a transform set applied in a horizontal direction according to an intra prediction mode.

[Table 4]

In Table 4, the numbers of transform sets applied to the horizontal direction of the residual signal according to the intra prediction mode of the target block are indicated.

Table 5 below shows an example of a transform set applied in a vertical direction according to an intra prediction mode.

[Table 5]

As illustrated in Tables 4 and 5, transform sets applied in the horizontal direction and the vertical direction may be predefined according to the intra prediction mode of the target block. The encoding apparatus 100 may perform transform and inverse transform on the residual signal by using a transform included in a transform set corresponding to the intra prediction mode of the target block. Also, the decoding apparatus 200 may perform inverse transform on the residual signal by using a transform included in a transform set corresponding to the intra prediction mode of the target block.

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

The method using various transforms as described above may be applied to a residual signal 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.

The primary transformation may be referred to as a primary transformation. Also, the first-order transform may be referred to as an adaptive multiple transform (AMT). AMT may mean that different transforms are applied to each of 1D directions (ie, a vertical direction and a horizontal direction) as described above.

The secondary transformation may be a transformation for improving the energy concentration of the transform coefficients generated by the primary transformation. The quadratic transform, like the first transform, may be a separable transform or a non-separable transform. The non-separable transform may be a Non-Separable Secondary Transform (NSST).

The first-order transformation may be performed using at least one of a plurality of predefined transformation methods. For example, a plurality of predefined transform methods include a discrete cosine transform (DCT), a discrete sine transform (DST), and a Karhunen-Loeve transform (KLT)-based transform. may include

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

The first-order transform and the second-order transform may be applied to one or more signal components of a luminance component and a chrominance component. Whether to apply the primary transform and/or the secondary transform may be determined according to at least one of coding parameters for the target block and/or the neighboring block. For example, whether the primary transform and/or the secondary transform is applied may be determined by the size and/or shape of the target block.

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. The determined transform method may indicate that a first-order transform and/or a quadratic transform is not used.

Alternatively, transformation information indicating a transformation method may be signaled from the encoding apparatus 100 to the decoding apparatus 200 . For example, the transform information may include an index of a transform to be used for a primary transform and/or a secondary transform.

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.

13 illustrates diagonal scanning according to an example.

14 illustrates horizontal scanning according to an example.

15 illustrates vertical scanning according to an example.

The quantized transform coefficients may be scanned according to at least one of (up-right) diagonal scanning, vertical scanning, and horizontal scanning according to at least one of an intra prediction mode, a block size, and a block shape. A block may be a transform unit.

Each scan may start at a specified start point and end at a specified end point.

For example, the quantized transform coefficients may be changed into a one-dimensional vector form by scanning the coefficients of the block using the diagonal scanning of FIG. 13 . Alternatively, the horizontal scanning of FIG. 14 or the vertical scanning of FIG. 15 may be used instead of the diagonal scanning according to the size of the block and/or the intra prediction mode.

The vertical scanning may be to scan the two-dimensional block shape coefficient in the column direction. Horizontal scanning may be a row-wise scanning of two-dimensional block shape coefficients.

That is, according to the size of the block and/or the inter prediction mode, it may be determined which scanning among diagonal scanning, vertical scanning, and horizontal scanning will be used.

13, 14 and 15 , the quantized transform coefficients may be scanned according to a diagonal direction, a horizontal direction, or a vertical direction.

The quantized transform coefficients may be expressed in a block form. A block may include a plurality of sub-blocks. Each sub-block may be defined according to a minimum block size or a minimum block shape.

In scanning, a scanning order according to a type or direction of scanning may be applied to sub-blocks first. Also, a scanning order according to a scanning direction may be applied to the quantized transform coefficients in the sub-block.

For example, as shown in FIGS. 13, 14 and 15 , when the size of the target block is 8x8, transform coefficients quantized by primary transform, secondary transform, and quantization for the residual signal of the target block are can be created Thereafter, one of three scanning orders may be applied to the four 4x4 subblocks, and quantized transform coefficients may be scanned for each 4x4 subblock according to the scanning order.

The scanned quantized transform coefficients may be entropy coded, and the bitstream may include entropy coded quantized transform coefficients.

The decoding apparatus 200 may generate quantized transform coefficients through entropy decoding of the bitstream. The quantized transform coefficients may be arranged 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 transform coefficients. 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.

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

The encoding apparatus 1600 may correspond to the above-described encoding apparatus 100 .

The encoding apparatus 1600 includes a processing unit 1610 , a memory 1630 , a user interface (UI) input device 1650 , a UI output device 1660 , and storage that communicate with each other through a bus 1690 . (1640) may be included. Also, the encoding apparatus 1600 may further include a communication unit 1620 connected to the network 1699 .

The processing unit 1610 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), the memory 1630 , or the storage 1640 . The processing unit 1610 may be at least one hardware processor.

The processing unit 1610 may generate and process a signal, data, or information input to the encoding apparatus 1600 , output from the encoding apparatus 1600 , or used inside the encoding apparatus 1600 , the signal, Inspection, comparison, and judgment related to data or information may be performed. In other words, 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 1610 .

The processing unit 1610 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 device 1600 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 1600 .

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 1600 .

The processing unit 1610 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 1630 and/or storage 1640 . Memory 1630 and storage 1640 may be various types of volatile or non-volatile storage media. For example, the memory 1630 may include at least one of a ROM 1631 and a RAM 1632 .

The storage unit may store data or information used for the operation of the encoding apparatus 1600 . In an embodiment, data or information included in the encoding apparatus 1600 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 1600 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 1600 to operate. The memory 1630 may store at least one module, and the at least one module may be configured to be executed by the processing unit 1610 .

A function related to communication of data or information of the encoding apparatus 1600 may be performed through the communication unit 1620 .

For example, the communication unit 1620 may transmit the bitstream to a decoding apparatus 1700 to be described later.

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

The decoding apparatus 1700 may correspond to the above-described decoding apparatus 200 .

The decryption apparatus 1700 includes a processing unit 1710 that communicates with each other through a bus 1790 , a memory 1730 , a user interface (UI) input device 1750 , a UI output device 1760 , and storage. (1740). Also, the decryption apparatus 1700 may further include a communication unit 1720 connected to the network 1799 .

The processing unit 1710 may be a semiconductor device that executes processing instructions stored in a central processing unit (CPU), the memory 1730 , or the storage 1740 . The processing unit 1710 may be at least one hardware processor.

The processing unit 1710 may generate and process a signal, data, or information input to the decoding device 1700, output from the decoding device 1700, or used inside the decoding device 1700, and 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 1710 .

The processing unit 1710 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 , a switch 245 , an adder 255 , and a filter. It may include a sub 260 and a reference picture buffer 270 .

Entropy decoding unit 210, inverse quantization unit 220, inverse transform unit 230, intra prediction unit 240, inter prediction unit 250, switch 245, adder 255, filter unit 260 and At least some of the 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 1700 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 1700 .

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 decryption apparatus 1700 .

The processing unit 1710 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 , a switch 245 , an adder 255 , and a filter. It can execute instructions or codes of the sub 260 and the reference picture buffer 270 .

Storage may represent memory 1730 and/or storage 1740 . Memory 1730 and storage 1740 may be various types of volatile or non-volatile storage media. For example, the memory 1730 may include at least one of a ROM 1731 and a RAM 1732 .

The storage unit may store data or information used for the operation of the decryption apparatus 1700 . In an embodiment, data or information included in the decryption apparatus 1700 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 1700 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 1700 to operate. The memory 1730 may store at least one module, and the at least one module may be configured to be executed by the processing unit 1710 .

A function related to communication of data or information of the decryption apparatus 1700 may be performed through the communication unit 1720 .

For example, the communication unit 1720 may receive a bitstream from the encoding apparatus 1600 .

Method and apparatus for bidirectional intra prediction

18 is a flowchart of a bidirectional intra prediction method according to an embodiment.

The bidirectional intra prediction method may be performed by the encoding apparatus 1600 and/or the decoding apparatus 1700 .

For example, the encoding apparatus 1600 may perform the prediction method of the embodiment in order to compare efficiencies of a plurality of prediction methods with respect to the target block and/or a plurality of divided blocks, and may perform the reconstructed method for the target block. The prediction method of the embodiment may be performed to generate a block.

In an embodiment, the target block may be a PU, or the target block may be at least one of a CTB, a CU, a PU, a TU, a sub-block, a block with a specified size, and a block within a predefined range of sizes. Alternatively, the target block may indicate a unit of coding.

For example, the decoding apparatus 1700 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 1610 of the encoding apparatus 1600 and/or the processing unit 1710 of the decoding apparatus 1700 .

In operation 1810, the processor may determine a bidirectional intra prediction mode to be applied to encoding and/or decoding of the target block.

The processing unit is at least one of 1) intra prediction mode indicator, 2) unidirectional/bidirectional discrimination indicator, 3) MPM, 4) availability of pixels in a neighboring block located in a direction specified with respect to the target block, and 5) prediction mode of the neighboring block. Based on this, a bidirectional intra prediction mode may be determined and derived.

In operation 1820 , the processor may determine a prediction value of the prediction block for the object block by performing bidirectional intra prediction on the object block using the determined bidirectional intra prediction mode.

In an embodiment, the two directions of the bidirectional intra prediction may be two directions in the form of a straight line consisting of directions opposite to each other. For example, the directions may be a 45 degree direction and a 225 degree direction.

In one embodiment, the directions of bidirectional intra prediction may be two different directions that are not in a straight line. For example, the directions may be a 45 degree direction and a 90 degree direction.

The processing unit may generate at least one virtual neighboring pixel with respect to a specified direction with respect to the target block, and may perform bidirectional intra prediction on the target block using the at least one virtual neighboring pixel. The processor may derive a prediction value of a target pixel of the prediction block based on at least one virtual neighboring pixel. The specified direction may be one or more of a right direction and a bottom direction.

The target pixel may be a pixel to be encoded and/or decoded.

The processing unit uses at least one of 1) pixels of neighboring blocks in both directions of bidirectional intra prediction, 2) weights according to a distance between each pixel of pixels of neighboring blocks in both directions and a target pixel, and 3) weights in both directions to use at least one of the weights of the target block It is possible to derive the predicted value of the target pixel of .

The prediction value of the target pixel of the target block may be a pixel value of the prediction block.

The processor may perform encoding and/or decoding of intra prediction using the derived prediction value.

The processing unit includes coding parameters related to the target block, information on the target picture, information on the target slice, quantization parameters, a coded block flag (CBF), the size of the target block, the shape of the target block, and entropy encoding applied to the target block. The bidirectional intra prediction mode of operation 1810 may be derived based on at least one of a method, an intra prediction mode of a neighboring block of the target block, and a temporal layer level of the target block.

Alternatively, the processing unit may include a coding parameter related to a target block, information on a target picture, information on a target slice, a quantization parameter, a coded block flag (CBF), a size of a target block, a shape of the target block, and applied to the target block. The prediction value of the target pixel of the target block in operation 1820 may be derived based on at least one of an entropy encoding method, an intra prediction mode of a neighboring block of the target block, and a temporal layer level of the target block.

Determination of bidirectional intra prediction mode

Hereinafter, the bidirectional intra prediction mode may indicate directions of bidirectional intra prediction. The terms “bidirectional intra prediction mode” and “directions of bidirectional intra prediction” may be used interchangeably and may be used interchangeably.

19 illustrates a unidirectional intra prediction mode according to an example.

20 illustrates a bidirectional intra prediction mode according to an example.

21 illustrates a bidirectional intra prediction mode using virtual neighboring pixels according to an example.

The processing unit is at least one of 1) intra prediction mode indicator, 2) unidirectional/bidirectional discrimination indicator, 3) MPM, 4) availability of pixels in a neighboring block located in a direction specified with respect to the target block, and 5) prediction mode of the neighboring block. Based on this, a bidirectional intra prediction mode may be determined and derived.

As shown in FIG. 19 , the unidirectional intra prediction mode may be an intra prediction mode referring to pixels located in one specified direction.

As shown in FIG. 20 , the bidirectional intra prediction mode may be an intra prediction mode referring to pixels located in two specified directions.

Here, the referenced pixels may be pixels adjacent to the target block. Pixels referenced for intra prediction may also be referred to as “samples”.

Here, "pixels located in two specified directions" may mean "pixels located in a specified first direction and pixels located in a specified second direction".

As shown in FIG. 21 , the bidirectional intra prediction mode may generate at least one virtual neighboring pixel located on the right or lower side of the target block using the reconstructed pixels of the neighboring block. In other words, at least one respective virtual neighboring pixel may be located at the right or bottom of the target block. The bi-directional intra prediction mode may be an intra prediction mode that refers to pixels located in two specified directions using a pixel of a reconstructed neighboring block and a virtual neighboring pixel.

Here, the virtual neighboring pixels located on the right side of the target block may be adjacent to the right side of the target block. A virtual neighboring pixel located at the bottom of the target block may be adjacent to the bottom of the target block.

The processing unit may determine whether to use the bidirectional intra prediction mode for the target block by using at least one of the unidirectional/bidirectional discrimination indicator and the intra prediction mode indicator, and may induce the bidirectional intra prediction mode.

The unidirectional/bidirectional discrimination indicator may indicate whether to use the bidirectional intra prediction mode for the target block. The unidirectional/bidirectional discrimination indicator may have one of a first value and a second value. The first value may indicate that unidirectional intra prediction is used. For example, the first value may be “0”. The second value may indicate that bi-directional intra prediction is used. For example, the second value may be “1”.

The unidirectional/bidirectional discrimination indicator is a video, sequence, picture, slice, tile, CTU, CU, target block, sub-block of the target block, and a block of a specified size, such as a specified coding and / or decoding unit level to be signaled at the level can That is, the specified unit of encoding and/or decoding may include a unidirectional/bidirectional discrimination indicator indicating whether to use the bidirectional intra prediction mode for objects in the unit.

The bidirectional intra prediction mode may indicate two directions for bidirectional intra prediction. The two directions may be indicated by methods such as 1) to 4) below.

1) There are two intra prediction mode indicators, and two directions of bidirectional intra prediction may be indicated by the two intra prediction mode indicators, respectively.

Each intra prediction mode indicator of the two intra prediction mode indicators may indicate a direction of a unidirectional intra prediction mode. Two directions of bi-directional intra prediction may be determined by two directions indicated by two intra prediction mode indicators.

In this case, one intra prediction mode indicator may indicate one direction for the intra prediction mode without distinguishing between unidirectional and bidirectional. Here, the direction may be an angle such as 45 degrees, 80 degrees and 135 degrees.

2) One intra prediction mode indicator may indicate one of the directions of the unidirectional intra prediction and the directions of the bidirectional intra prediction.

For example, the value “3” of the intra prediction mode indicator may indicate unidirectional intra prediction of 45 degrees, and the value “70” of the intra prediction mode indicator may indicate bidirectional intra prediction of 45 degrees and 225 degrees.

3) To indicate the direction of intra prediction, a unidirectional/bidirectional discrimination indicator and an intra prediction mode indicator may be used together.

The unidirectional/bidirectional distinction indicator may indicate which one of unidirectional intra prediction and bidirectional intra prediction is used, and the intra prediction mode indicator may indicate a direction.

For example, when the value of the unidirectional/bidirectional distinction indicator is the second value and the value of the intra prediction mode indicator is 7, bidirectional intra prediction of 45 degrees and 255 degrees opposite to the 45 degrees may be used.

For example, when the value of the unidirectional/bidirectional discrimination indicator is the first value and the value of the intra prediction mode indicator is 7, unidirectional intra prediction of 45 degrees may be used.

4) When one intra prediction mode indicator indicates a specified unidirectional intra prediction direction, bidirectional intra prediction may be performed.

For example, when the intra prediction mode indicator indicates unidirectional prediction of 45 degrees, bidirectional intra prediction of 45 degrees and 255 degrees opposite to the 45 degrees may be performed.

22 illustrates that bidirectional intra prediction is derived and selected from a direction of an intra prediction mode indicator according to an example.

The processing unit may adaptively determine and induce the bidirectional intra prediction mode based on 1) the intra prediction mode indicator and 2) the availability of pixels of a neighboring block of the target block.

22 , the intra prediction mode indicator may indicate one direction of the intra prediction mode, and another direction corresponding to the direction of the intra prediction mode may be determined. Here, the other direction may be a direction for bidirectional intra prediction determined according to the direction of the intra prediction mode.

The other direction may be a direction opposite to the intra prediction direction.

One of unidirectional intra prediction and bidirectional intra prediction may be selected and derived according to availability of a reference pixel in a direction corresponding to the direction indicated by the intra prediction mode indicator.

For example, one of unidirectional intra prediction and bidirectional intra prediction may be selected and derived according to availability of a reference pixel in a direction opposite to the direction indicated by the intra prediction mode indicator.

Here, when the reference pixel in the corresponding direction is available, bidirectional intra prediction may be selected, and when the reference pixel in the corresponding direction is not available, unidirectional intra prediction may be selected.

Hereinafter, "a (reference) pixel in a specific direction" may mean "a (reference) pixel located in a specific direction".

Here, that the reference pixel is available may mean that the value of the reference pixel is determined. Alternatively, that the reference pixel is available may mean that reconstruction of the reference pixel has been performed before intra prediction for the target block. That the reference pixel is not available may mean that the value of the reference pixel has not been determined. Alternatively, the fact that the reference pixel is not available may mean that the reference pixel has not been reconstructed prior to intra prediction for the target block, and thus the value of the reference pixel has not been determined.

For example, if the intra-prediction mode indicator indicates a right-up (for example, 45 degrees) direction, and pixels of a neighboring block of a left-down (for example, 225 degrees) opposite direction to the right-upward direction are available, the processing unit The intra prediction to be used for the block may be determined as bi-directional intra prediction in two directions, upward and leftward.

For example, if the intra-prediction mode indicator indicates a direction of upward-facing (eg, 45 degrees), and pixels of neighboring blocks in a downward-left direction (eg, 225 degrees) opposite to the right-upward direction are not available, the processing unit An intra prediction to be used for the target block may be determined as an upward unidirectional intra prediction.

A unit of determination and derivation of the intra prediction mode may be a target block. Here, the selection of the intra prediction mode may determine which one of unidirectional intra prediction and bidirectional intra prediction is to be used. That is, which one of the unidirectional intra prediction and the bidirectional intra prediction is to be used for the entire object block may be adaptively determined.

Hereinafter, the intra prediction direction indicated by the intra prediction mode indicator is referred to as a first direction, and the second direction refers to a direction corresponding to the first direction or a direction opposite to the first direction.

For example, for all pixels of a target block, if all reference pixels for the first direction and all reference pixels for the second direction are available, bi-directional intra prediction in the first direction and the second direction may be used. . For all pixels of the target block, when at least one reference pixel that is not available among all reference pixels in the second direction exists, unidirectional intra prediction in the first direction may be used.

A unit of determination and derivation of the intra prediction mode may be a pixel of a target block. That is, which one of the unidirectional intra prediction and the bidirectional intra prediction is to be used for each pixel of the pixels of the target block may be adaptively determined.

For example, for a specified pixel of the target block, if the reference pixel for the first direction and the reference pixel for the second direction are available, the bidirectional intra prediction in the first direction and the second direction may be used. For a specified pixel of the target block, if a reference pixel for the second direction is not available, unidirectional intra prediction in the first direction may be used.

When the reference pixel for the first direction or the reference pixel for the second direction is not available, the processing unit may generate a value of the unavailable reference pixel by using padding. In this case, a value used for padding for an unavailable reference pixel may be a value of an available reference pixel closest to the unavailable reference pixel. In the case of a plurality of nearest available reference pixels, a value to be padded with an unavailable reference pixel may be an average of values of the plurality of nearest available reference pixels.

An unavailable reference pixel may be made available by padding, and unidirectional intra prediction or bidirectional intra prediction using the available reference pixel may be performed.

The second direction may be in a straight line opposite to the first direction indicated by the intra prediction mode indicator. That is, the second direction may be a direction in which 180 degrees are added to the first direction. Alternatively, the second direction may be a direction in which a predefined angle α is added to the first direction indicated by the intra prediction mode indicator. The predefined angle α may be equally set in the encoding apparatus 1600 and the decoding apparatus 1700 , and may be signaled from the encoding apparatus 1600 to the decoding apparatus 1700 .

As described above, the intra prediction mode indicator in the embodiment may not distinguish between unidirectional and bidirectional, and may indicate the direction of intra prediction.

The processing unit may select a bidirectional intra prediction mode for the target block based on at least one of 1) MPM, 2) unidirectional/bidirectional discrimination indicator, 3) intra prediction mode of neighboring blocks, and 4) availability of reference pixels in a specified direction. have.

The processor may determine the bidirectional intra prediction mode for the target block by using the intra prediction mode and the MPM of the neighboring block.

The processing unit may determine the bidirectional intra prediction mode for the target block by using the MPM and the intra prediction mode of a neighboring block of the target block.

For example, when bidirectional intra prediction is used for at least one of the neighboring blocks and at least one of the MPMs of the target block matches the bidirectional intra prediction mode of the neighboring block, the processing unit uses the matching MPM for bidirectional intra prediction The mode may be determined as the bidirectional intra prediction mode of the target block.

For example, the processor may determine the bidirectional intra prediction mode for the object block by using two directional MPMs among the N MPMs of the object block. N may be an integer of 2 or more. For example, N may be 6.

The processor may determine the bidirectional intra prediction mode for the target block by using the intra prediction mode, the MPM, and the unidirectional/bidirectional discrimination indicator of the neighboring blocks of the target block.

For example, when the unidirectional/bidirectional distinction indicator indicates that bidirectional intra prediction is used, the processing unit may determine the bidirectional intra prediction mode for the target block by using one of the MPMs of the target block. For example, the MPM used may be the first MPM in the MPM list.

The processing unit may select the bidirectional intra prediction mode for the target block based on the intra prediction mode and MPM of the neighboring block, and availability of reference pixels in a direction opposite to the intra prediction direction of the neighboring block.

For example, the processing unit may derive an intra prediction direction for the target block from one of the MPMs of the target block, and if a reference pixel in a direction corresponding to the derived direction is available, the derived direction and the A bidirectional intra prediction mode in a corresponding direction may be used for intra prediction of a target block.

Intra prediction using bidirectional intra prediction mode

When the intra prediction mode of the target block is derived and selected as the bidirectional intra prediction mode, the processing unit may determine the prediction value of the target pixel by referring to at least one of pixels of neighboring blocks in two prediction directions of the bidirectional intra prediction mode. .

Here, the target pixel may be a pixel that is a target of prediction, and may be a pixel of the target block or a pixel of a prediction block with respect to the target block. That is, the prediction value of the target block may be determined by the bidirectional intra prediction according to the bidirectional intra prediction mode.

In such bidirectional intra prediction, the processor may obtain reference pixels in each prediction direction by filtering pixels of neighboring blocks in each prediction direction of the prediction directions of the bidirectional intra prediction. The processor may derive a predicted value of the target pixel by using at least one of the obtained reference pixels.

In other words, the reference pixel may be a pixel of a neighboring block, and may be a pixel at a position designated by a specified prediction direction from a pixel of the target block. Alternatively, the reference pixel may be a value obtained by applying filtering to pixels in the vicinity of a position designated by a specified prediction direction from a pixel of the target block.

The processor may determine the prediction value of the target pixel by using at least one of reference pixels in two prediction directions of the bidirectional intra prediction mode.

In using at least one of the reference pixels of the two prediction directions of the bidirectional intra prediction mode, a weight may be applied to each reference pixel of the reference pixels. The weight may be predefined. Alternatively, the weight may be determined by calculation.

For example, the weight may be determined based on a distance between the target pixel and the reference pixel. The weight may be inversely proportional to the distance between the target pixel and the reference pixel. Alternatively, the weight may be proportional to the distance between the target pixel and the reference pixel. The ratio of the weights of the reference pixels may be the inverse of the ratio of the distances between each reference pixel and the target pixel of the reference pixels.

A weight for a reference pixel may be different according to prediction directions.

The weight for the reference pixel may be different depending on whether the reference pixel is a reference pixel for a direction indicated by the intra prediction mode indicator. For example, the weight of the direction indicated by the intra prediction mode indicator may be α, and the weight of the direction corresponding to the indicated direction may be 1-α. α can be a real number greater than 0 and less than 1. For example, α may be 2/3.

Alternatively, the weight for the reference pixel may be determined based on a distance between the target pixel and the reference pixel and whether the reference pixel is a reference pixel in a direction indicated by the intra prediction mode indicator.

The weight may be determined by the encoding apparatus 1600, and the determined weight may be signaled from the encoding apparatus 1600 to the decoding apparatus 1700 through a bitstream.

When the weight of one of the two prediction directions of the bidirectional intra prediction mode is signaled, the weight of the other prediction direction may be determined based on the signaled weight.

The weight may be signaled at the level of a specified unit of encoding and/or decoding, such as a video, sequence, picture, slice, tile, CTU, CU, object block, sub-block of the object block, and a block of a specified size. In other words, a specified unit of encoding and/or decoding may include a weight used for objects in the unit or information used for deriving a weight.

Bidirectional intra prediction using virtual pixels

23 illustrates generation of virtual peripheral pixels according to an example.

Some of the pixels of the two prediction directions of the bidirectional intra prediction mode may not be used for bidirectional intra prediction because some of the pixels above have not been reconstructed before of bidirectional intra prediction. The processing unit may generate virtual neighboring pixels corresponding to non-reconstructed pixels, and may perform bidirectional intra prediction using the virtual neighboring pixels.

The neighboring pixels may be reconstructed pixels of the reconstructed neighboring blocks. The virtual surrounding pixel may be a pixel created using one or more reconstructed pixels. In other words, the value of the virtual surrounding pixel may be generated based on values of one or more reconstructed pixels.

For example, the virtual neighboring pixel may be a pixel adjacent to the top or left side of the target block. The virtual neighboring pixel may be a pixel adjacent to the bottom or right side of the target block.

The virtual surrounding pixels for the target block may be pixels within the virtual surrounding block for the target block. The virtual neighboring block may be a non-reconstructed block adjacent to the target block. For example, the virtual neighboring block may be a block adjacent to the bottom or right side of the target block.

When the intra-prediction mode of the target block is derived and determined as the bidirectional intra prediction mode, the processing unit refers to at least one of surrounding pixels and virtual surrounding pixels in two prediction directions of the bi-directional intra prediction mode to obtain a prediction value of the target pixel can decide

In such prediction, the processing unit may obtain reference pixels in each prediction direction by filtering neighboring pixels in each prediction direction. Also, the processor may obtain reference pixels in each prediction direction by filtering virtual neighboring pixels in each prediction direction. The processor may derive a predicted value of the target pixel by using at least one of the obtained reference pixels.

In other words, the reference pixel may be a neighboring pixel or a virtual neighboring pixel, and may be a pixel at a position designated by a specified prediction direction from a pixel of the target block. Alternatively, the reference pixel may be a value obtained by applying filtering to neighboring pixels and/or virtual neighboring pixels in the vicinity of a position designated by a specified prediction direction from a pixel of the target block.

The processor may determine the prediction value of the target pixel by using at least one of reference pixels in two prediction directions of the bidirectional intra prediction mode. Reference pixels may include surrounding pixels and virtual surrounding pixels.

The description of the above-described weights may be applied to virtual neighboring pixels as well. In using at least one of the reference pixels in the two prediction directions of the bi-directional intra prediction mode, a weight may be applied to each of the reference pixels, the neighboring pixel and the virtual neighboring pixel.

In the following, exemplary methods for generating a virtual surrounding pixel are described.

The upper-left coordinates of the target block may be (Cx, Cy). W may be the horizontal size of the target block. H may be the height or vertical size of the target block.

Hereinafter, “pixel (α, β)” may refer to a pixel whose coordinates are (α, β).

1) The processing unit may generate a virtual neighboring pixel based on the pixels of the reconstructed neighboring blocks.

The virtual neighboring pixels may include right virtual neighboring pixels adjacent to the right side of the target block and lower virtual neighboring pixels adjacent to the bottom of the target block.

The positions of the right virtual neighboring pixels may be as in Equation 2 below.

[Equation 2]

N(Cx+W, y) where (y ∈ {Cy, Cy+1, Cy+2, …, Cy+H})

The positions of the lower virtual surrounding pixels may be as in Equation 3 below.

[Equation 3]

N(x, Cy+H) where (x ∈ {Cx, Cx+1, Cx+2, …, Cx+W})

2) The processing unit may generate virtual neighboring pixels (Cx+W, Cy) based on one or more of the restored neighboring pixels adjacent to the top of the target block.

For example, in FIG. 23 , the virtual neighboring pixel R may be generated using one or more of the reconstructed neighboring pixels adjacent to the top of the target block. The virtual neighboring pixel R may be an uppermost virtual neighboring pixel among the right virtual neighboring pixels.

3) The processing unit may generate virtual neighboring pixels (Cx+W, Cy) based on the neighboring pixels (Cx+W, Cy-1).

For example, in FIG. 23 , the virtual surrounding pixel R may be created using the surrounding pixel b. The virtual neighboring pixel R may be an uppermost virtual neighboring pixel among the right virtual neighboring pixels. The peripheral pixel b may be a pixel adjacent to the top of the virtual peripheral pixel R.

For example, the relationship between the virtual neighboring pixel R and the neighboring pixel b may be expressed as Equation 4 below.

[Equation 4]

R = b

4) the processing unit is virtual based on one or more of the surrounding pixels (Cx+W-1, Cy-1), the surrounding pixels (Cx+W, Cy-1), and the surrounding pixels (Cx+W+1, Cy-1) You can create surrounding pixels (Cx+W, Cy).

For example, in FIG. 23 , the virtual surrounding pixel R may be generated using the surrounding pixel a, the surrounding pixel b, and the surrounding pixel c. The virtual neighboring pixel R may be an uppermost virtual neighboring pixel among the right virtual neighboring pixels.

Coordinates of the neighboring pixel a, the neighboring pixel b, and the neighboring pixel c may be as shown in Equations 5, 6, and 7 below, respectively.

[Equation 5]

(Cx+W-1, Cy-1)

[Equation 6]

(Cx+W, Cy-1)

[Equation 7]

(Cx+W+1, Cy-1)

In other words, the peripheral pixel b may be a pixel adjacent to the top of the virtual peripheral pixel R. The neighboring pixel a may be a pixel adjacent to the left of the neighboring pixel b. The neighboring pixel c may be a pixel adjacent to the right of the neighboring pixel b.

For example, in FIG. 23 , the virtual neighboring pixel R may be a weighted-sum of the neighboring pixel a, the neighboring pixel b, and the neighboring pixel c. In generating the virtual neighboring pixel R, weights may be assigned to the neighboring pixel a, the neighboring pixel b, and the neighboring pixel c, respectively.

For example, the relationship between the virtual neighboring pixel R, the neighboring pixel a, the neighboring pixel b, and the neighboring pixel c may be expressed as Equation 8 below.

[Equation 8]

R = 1/4*a + 2/4*b + 1/4*c = 1/4*a + 1/2*b + 1/4*c = (a + b << 1 + c) >> 2

Here, "<<" may be a left shift operator. ">>" may be a right shift operator.

5) Similar to 2) to 4) described above, the processing unit may generate virtual neighboring pixels (Cx, Cy+H) based on one or more of the reconstructed neighboring pixels adjacent to the left side of the target block.

For example, in FIG. 23 , the virtual neighboring pixel L may be generated using one or more of the reconstructed neighboring pixels adjacent to the left side of the target block. The virtual peripheral pixel L may be a leftmost virtual peripheral pixel among the lower virtual peripheral pixels.

6) The processing unit may generate virtual neighboring pixels (Cx, Cy+H) based on the neighboring pixels (Cx-1, Cy+H).

For example, in FIG. 23 , a virtual surrounding pixel L may be created using the surrounding pixel q. The virtual peripheral pixel L may be a leftmost virtual peripheral pixel among the lower virtual peripheral pixels. The peripheral pixel q may be a pixel adjacent to the left of the virtual peripheral pixel L.

For example, the relationship between the virtual neighboring pixel L and the neighboring pixel q may be expressed as Equation 9 below.

[Equation 9]

L = q

7) the processing unit is virtual based on one or more of a peripheral pixel (Cx-1, Cy+H-1), a peripheral pixel (Cx-1, Cy+H), and a peripheral pixel (Cx-1, Cy+H+1) You can create surrounding pixels (Cx, Cy+H).

For example, in FIG. 23 , a virtual surrounding pixel L may be created using the surrounding pixel p, the surrounding pixel q, and the surrounding pixel r. The virtual peripheral pixel L may be a leftmost virtual peripheral pixel among the lower virtual peripheral pixels.

Coordinates of the neighboring pixel p, the neighboring pixel q, and the neighboring pixel r may be as shown in Equations 10, 11, and 12 below, respectively.

[Equation 10]

(Cx-1, Cy+H-1)

[Equation 11]

(Cx-1, Cy+H)

[Equation 12]

(Cx-1, Cy+H+1)

In other words, the peripheral pixel q may be a pixel adjacent to the left of the virtual peripheral pixel L. The neighboring pixel p may be a pixel adjacent to the top of the neighboring pixel q. The neighboring pixel r may be a pixel adjacent to the bottom of the neighboring pixel q.

For example, in FIG. 23 , the virtual neighboring pixel L may be a weighted-sum of the neighboring pixel p, the neighboring pixel q, and the neighboring pixel r. In generating the virtual neighboring pixel L, weights may be assigned to the neighboring pixel p, the neighboring pixel q, and the neighboring pixel r, respectively.

For example, the relationship between the virtual neighboring pixel L, the neighboring pixel p, the neighboring pixel q, and the neighboring pixel r may be expressed as Equation 13 below.

[Equation 13]

L = 1/4*p + 2/4*q + 1/4*r = 1/4*p + 1/2*q + 1/4*r = (p + q << 1 + r) >> 2

8) The processing unit may generate another virtual neighboring pixel based on a plurality of virtual neighboring pixels generated using the neighboring pixels.

For example, in FIG. 23 , the virtual surrounding pixel N _i may be generated based on the virtual surrounding pixel R and the virtual surrounding pixel L . The virtual peripheral pixel N _i may be a virtual peripheral pixel between the virtual peripheral pixel R and the virtual peripheral pixel L.

24 illustrates the creation of another virtual surrounding pixel using virtual surrounding pixels according to an example.

As shown in FIG. 24 , the virtual neighboring pixels for the target block may be arranged in a line according to the distance from the virtual neighboring pixel L and the distance from the virtual neighboring pixel R.

The specified distance between the virtual neighboring pixel N _i and the virtual neighboring pixel L may be expressed as in Equation 14 below.

[Equation 14]

(N _It's the absolute value of the difference between the x-coordinate of and the x-coordinate of L) + (N _It's the absolute value of the difference between the y-coordinate of and the y-coordinate of L)

The specified distance between the virtual neighboring pixel N _i and the virtual neighboring pixel R may be expressed as in Equation 15 below.

[Equation 15]

(N _It's the absolute value of the difference between the x-coordinate of and the x-coordinate of R) + (N _It's absolute value of the difference between the y-coordinate of and the y-coordinate of R)

In other words, the distance between pixels may be the sum of the absolute value of the difference between the x coordinates of the pixels and the absolute value of the difference between the y coordinates of the pixels.

9) the processing unit may generate a virtual surrounding pixel L and a virtual surrounding pixel R based on the surrounding pixels of the restored surrounding block, and the virtual surrounding pixel L and the virtual surrounding pixel R based on the virtual surrounding pixel L and the virtual surrounding pixel R It is possible to create a virtual surrounding pixel N _i between .

In generating the virtual surrounding pixel N _i , weights for distance may be used. The distance weights may include a weight according to the distance between the virtual neighboring pixel N _i and the virtual neighboring pixel L and a weight according to the distance between the virtual neighboring pixel N _i and the virtual neighboring pixel R.

For example, the relationship between the virtual neighboring pixel N _i , the virtual neighboring pixel L and the virtual neighboring pixel R may be expressed as Equation 16 below.

[Equation 16]

d _R may be the distance between the virtual surrounding pixel N _i and the virtual surrounding pixel R .

d _L may be the distance between the virtual neighboring pixel N _i and the virtual neighboring pixel L .

25 illustrates generation of a lower right virtual peripheral pixel and a middle virtual peripheral pixel according to an example.

The upper-left coordinates of the target block may be (Cx, Cy). W may be the horizontal size of the target block. H may be the height or vertical size of the target block.

10) The processing unit may generate virtual neighboring pixels (Cx+W, Cy+H) based on one or more of the reconstructed neighboring pixels adjacent to the top of the target block and one or more of the reconstructed neighboring pixels adjacent to the left of the target block.

For example, in FIG. 25 , the virtual neighboring pixel G may be generated using one or more of the reconstructed neighboring pixels adjacent to the top of the target block and the reconstructed neighboring pixels adjacent to the left of the target block. The virtual peripheral pixel G may be a lower right virtual peripheral pixel. In other words, the virtual peripheral pixel G may be a pixel adjacent to the right of the lower virtual peripheral pixels, and may be a pixel adjacent to the bottom of the right virtual peripheral pixels.

11) The processing unit may generate virtual neighboring pixels (Cx+W, Cy+H) based on the neighboring pixels (Cx+W, Cy-1) and the neighboring pixels (Cx-1, Cy+H).

For example, in FIG. 25 , a virtual surrounding pixel G may be created using the surrounding pixel b and the surrounding pixel q. The virtual peripheral pixel G may be a lower right virtual peripheral pixel. The neighboring pixel b may be a pixel adjacent to the upper right corner of the target block. The neighboring pixel q may be a pixel adjacent to the lower left corner of the target block.

For example, the relationship between the virtual neighboring pixel G, the neighboring pixel b, and the neighboring pixel q may be expressed as Equation 17 below.

[Equation 17]

G = 1/2 * (b + q) = (b + q) >> 1

12) The processor may generate virtual peripheral pixels (Cx+W, Cy+H) based on the virtual peripheral pixels (Cx+W, Cy) and the virtual peripheral pixels (Cx, Cy+H).

For example, in FIG. 25 , a virtual surrounding pixel G may be created using a virtual surrounding pixel R and a virtual surrounding pixel L. The virtual peripheral pixel G may be a lower right virtual peripheral pixel. The virtual neighboring pixel R may be an uppermost virtual neighboring pixel among the right virtual neighboring pixels. The virtual peripheral pixel L may be a leftmost virtual peripheral pixel among the lower virtual peripheral pixels.

For example, the relationship between the virtual peripheral pixel G, the virtual peripheral pixel R, and the virtual peripheral pixel L may be as in Equation 18 below.

[Equation 18]

G = 1/2 * (R + L) = (R + L) >> 1

13) The processing unit may generate a third virtual peripheral pixel based on the first virtual peripheral pixel and the second virtual peripheral pixel, and generate a fourth virtual peripheral pixel based on the first virtual peripheral pixel and the third virtual peripheral pixel can do.

The processing unit generates virtual peripheral pixels (Cx+W, Cy) and virtual peripheral pixels (Cx+W, Cy) and It is possible to create virtual peripheral pixels between the virtual peripheral pixels (Cx+W, Cy+H). In addition, the processing unit is based on the virtual peripheral pixel (Cx+W, Cy), the virtual peripheral pixel (Cx, Cy+H) and the virtual peripheral pixel (Cx+W, Cy+H) based on the virtual peripheral pixel (Cx, Cy+H) ) and virtual peripheral pixels (Cx+W, Cy+H).

For example, in FIG. 25 , a virtual surrounding pixel M _i may be created using a virtual surrounding pixel R, a virtual surrounding pixel L, and a virtual surrounding pixel G. The virtual peripheral pixel M _i may be a pixel between the virtual peripheral pixel R and the virtual peripheral pixel G.

For example, in FIG. 25 , a virtual surrounding pixel N _i may be created using a virtual surrounding pixel R, a virtual surrounding pixel L, and a virtual surrounding pixel G. The virtual peripheral pixel N _i may be a pixel between the virtual peripheral pixel L and the virtual peripheral pixel G.

14) The processing unit may generate a third virtual peripheral pixel based on the first virtual peripheral pixel and the second virtual peripheral pixel, and generate a fourth virtual peripheral pixel based on the first virtual peripheral pixel and the third virtual peripheral pixel can do. In this case, the processing unit may use weights for other virtual neighboring pixels when generating the fourth virtual neighboring pixels. The other virtual peripheral pixels may include a first virtual peripheral pixel and a third virtual peripheral pixel. A weight for the other virtual neighboring pixel may be determined based on a distance between the fourth virtual neighboring pixel and the other virtual neighboring pixel.

For example, in FIG. 25 , a virtual surrounding pixel M _i may be created using a virtual surrounding pixel R, a virtual surrounding pixel L, and a virtual surrounding pixel G. The virtual peripheral pixel M _i may be a pixel between the virtual peripheral pixel R and the virtual peripheral pixel G.

In the generation of the virtual peripheral pixel M _i , one or more of a weight for the virtual peripheral pixel R and a weight for the virtual peripheral pixel L and a weight for the virtual peripheral pixel G may be used.

A weight for the virtual surrounding pixel R may be determined based on a distance between the virtual surrounding pixel R and the virtual surrounding pixel M _i .

A weight for the virtual surrounding pixel L may be determined based on a distance between the virtual surrounding pixel L and the virtual surrounding pixel M _i .

A weight for the virtual surrounding pixel G may be determined based on a distance between the virtual surrounding pixel G and the virtual surrounding pixel M _i .

For example, in FIG. 25 , a virtual surrounding pixel N _i may be created using a virtual surrounding pixel R, a virtual surrounding pixel L, and a virtual surrounding pixel G. The virtual peripheral pixel N _i may be a pixel between the virtual peripheral pixel L and the virtual peripheral pixel G.

In the generation of the virtual peripheral pixel N _i , one or more of a weight for the virtual peripheral pixel R and a weight for the virtual peripheral pixel L and a weight for the virtual peripheral pixel G may be used.

A weight for the virtual neighboring pixel R may be determined based on a distance between the virtual neighboring pixel R and the virtual neighboring pixel N _i .

A weight for the virtual neighboring pixel L may be determined based on a distance between the virtual neighboring pixel L and the virtual neighboring pixel N _i .

A weight for the virtual surrounding pixel G may be determined based on a distance between the virtual surrounding pixel G and the virtual surrounding pixel N _i .

A weight for the virtual surrounding pixel L may be determined based on a distance between the virtual surrounding pixel G and the virtual surrounding pixel N _i . The weight for the virtual surrounding pixel L may be proportional to the distance between the virtual surrounding pixel G and the virtual surrounding pixel N _i . The weight for the virtual surrounding pixel L may be inversely proportional to the sum of the distances of the virtual surrounding pixel L and the virtual surrounding pixel G from the virtual surrounding pixel N _i .

A weight for the virtual surrounding pixel G may be determined based on a distance between the virtual surrounding pixel L and the virtual surrounding pixel N _i . The weight for the virtual surrounding pixel G may be proportional to the distance between the virtual surrounding pixel L and the virtual surrounding pixel N _i . The weight for the virtual surrounding pixel G may be inversely proportional to the sum of the distances of the virtual surrounding pixel L and the virtual surrounding pixel G from the virtual surrounding pixel N _i .

For example, a relationship between the virtual neighboring pixel N _i , the virtual neighboring pixel L and the virtual neighboring pixel G may be expressed as Equation 19 below.

[Equation 19]

d _G may be the distance between the virtual surrounding pixel N _i and the virtual surrounding pixel G .

d _L may be the distance between the virtual neighboring pixel N _i and the virtual neighboring pixel L .

For example, the relationship between the virtual neighboring pixel M _i , the virtual neighboring pixel R and the virtual neighboring pixel G may be expressed as Equation 20 below.

[Equation 20]

d _G may be the distance between the virtual surrounding pixel M _i and the virtual surrounding pixel G.

d _R may be the distance between the virtual surrounding pixel M _i and the virtual surrounding pixel R .

26 illustrates bidirectional intra prediction according to an example.

The processor may derive the prediction value of the target pixel by using at least one of the reconstructed neighboring pixel and the virtual neighboring pixel with respect to two prediction directions of the bidirectional intra prediction mode.

The processing unit may derive the prediction value of the target pixel X by using one or more of the two reference pixels for the two prediction directions of the bidirectional intra prediction mode.

The two reference pixels may include a reference pixel Ref_A and a reference pixel Ref_B.

Ref_A and Ref_B may be pixels located in two prediction directions derived and selected by bi-directional intra prediction with respect to the target pixel, respectively.

The two reference pixels may be reconstructed surrounding pixels. For example, as shown in FIG. 26 , both Ref_A and Ref_B may be neighboring pixels.

27 illustrates bidirectional intra prediction using virtual neighboring pixels according to an example.

The processing unit may derive the prediction value of the target pixel X by using one or more of the two reference pixels for the two prediction directions of the bidirectional intra prediction mode.

The two reference pixels may include a reference pixel Ref_A and a reference pixel Ref_B.

Ref_A and Ref_B may be pixels located in two prediction directions derived and selected by bi-directional intra prediction with respect to the target pixel, respectively.

At least one of the two reference pixels may be a virtual peripheral pixel. For example, as shown in FIG. 27 , Ref_A may be a neighboring pixel, and Ref_B may be a virtual neighboring pixel.

The reference pixel may be a pixel at a specified position along each prediction direction of the two prediction directions of the bidirectional intra prediction. The processing unit may obtain the reference pixel by performing filtering on one or more of surrounding pixels and/or virtual surrounding pixels of the specified location.

For example, when the specified position is not a coordinate of integers, the processing unit may obtain a reference pixel by performing filtering on one or more of surrounding pixels and/or virtual surrounding pixels surrounding the specified position. can

For example, if the pixel at the specified location is not available, the processing unit may obtain a reference pixel by performing filtering on one or more of surrounding pixels and/or virtual surrounding pixels surrounding the specified location. can

The surrounding pixels of the specified position may be neighboring pixels of the specified position. The virtual surrounding pixels surrounding the specified location may be virtual surrounding pixels adjacent to the specified location.

The derived prediction value Pred_X of the target pixel may be a statistical value related to one or more of Ref_A and Ref_B, and may be derived based on the statistical value. Hereinafter, the statistical value of the embodiments may mean at least one of an average value, a weighted average value, a maximum value, a minimum value, a mode value, a median value, and an interpolation value.

As illustrated in Equation 21 below, the prediction value Pred_X of the target pixel may be derived using Ref_A and Ref_B.

[Equation 21]

Pred_X = F(Ref_A, Ref_B)

F() may be a specified function.

As described above, the processing unit may derive the prediction value of the target pixel X by using one or more of the two reference pixels for the two prediction directions of the bidirectional intra prediction mode. In this case, in deriving the prediction value of the target pixel X, the processor may apply weights to the two reference pixels in the two prediction directions, respectively.

For example, the sum of the weights may be 1.

The two reference pixels may include a reference pixel Ref_A and a reference pixel Ref_B.

Ref_A and Ref_B may be pixels located in two prediction directions derived and selected by bi-directional intra prediction with respect to the target pixel, respectively.

For example, as shown in FIG. 26 , Ref_A and Ref_B may be reconstructed neighboring pixels.

Alternatively, for example, as shown in FIG. 27 , Ref_A may be a reconstructed neighboring pixel, and Ref_B may be a virtual neighboring pixel.

As illustrated in Equation 22 below, the predicted value Pred_X of the target pixel may be derived using a weight for Ref_A and a weight for Ref_B.

[Equation 22]

Pred_X = Dir_A * Ref_A + Dir_B * Ref_B

Dir_A may be a weight for Ref_A. Dir_B may be a weight for Ref_B.

The sum of Dir_A and Dir_B may be 1.

In generating the derived prediction value Pred_X of the target block, the processing unit may use the aforementioned filtering for obtaining the reference pixel and a weight for the reference pixel together.

The reference pixel may be a pixel at a specified position along each prediction direction of the two prediction directions of the bidirectional intra prediction. The processing unit may obtain the reference pixel by performing filtering on one or more of surrounding pixels and/or virtual surrounding pixels of the specified location. Also, the processor may apply a weight to the generated reference pixel.

28 illustrates bidirectional intra prediction using a distance between a neighboring pixel and a target pixel according to an example.

29 illustrates bidirectional intra prediction using a distance between a virtual neighboring pixel and a target pixel according to an example.

As described above, the processing unit may derive the prediction value of the target pixel X by using one or more of the two reference pixels for the two prediction directions of the bidirectional intra prediction mode. In this case, the processor may use a weight according to the distance between the reference pixel and the target pixel for each reference pixel of the two reference pixels in the two prediction directions.

The two reference pixels may include a reference pixel Ref_A and a reference pixel Ref_B.

Ref_A and Ref_B may be pixels located in two prediction directions derived and selected by bi-directional intra prediction with respect to the target pixel, respectively.

For example, as shown in FIG. 28 , Ref_A and Ref_B may be reconstructed neighboring pixels.

Alternatively, for example, as shown in FIG. 29 , Ref_A may be a reconstructed neighboring pixel, and Ref_B may be a virtual neighboring pixel.

In generating the derived prediction value Pred_X of the target block, the processing unit may use the aforementioned filtering for obtaining the reference pixel and a weight according to a distance between the reference pixel and the target pixel together.

The reference pixel may be a pixel at a specified position along each prediction direction of the two prediction directions of the bidirectional intra prediction. The processing unit may obtain the reference pixel by performing filtering on one or more of surrounding pixels and/or virtual surrounding pixels of the specified location. Also, the processor may apply a weight to the generated reference pixel.

As illustrated in Equation 23 below, the predicted value Pred_X of the target pixel may be derived using one or more of Ref_A, Dis_A, Ref_B, and Dis_B.

[Equation 23]

Pred_X = F(Ref_A, Dis_A, Ref_B, Dis_B)

F() may be a specified function.

Dis_A may be the distance between the target pixel and Ref_A. Dis_B may be the distance between the target pixel and Ref_B.

The derived prediction value Pred_X of the target pixel may be a statistical value related to one or more of Ref_A, Dis_A, Ref_B, and Dis_B, and may be derived based on the statistical value.

As illustrated in Equation 24 below, the prediction value Pred_X of the target pixel may be derived based on a weight according to the distance between the target pixel and the reference pixel.

[Equation 24]

A weight for one of the two reference pixels may be proportional to a distance between the target pixel and the other of the two reference pixels.

A weight for one of the two reference pixels may be inversely proportional to the sum of distances of the two reference pixels from the target pixel.

For example, the weight for Ref_B may be as in Equation 25 below.

[Equation 25]

For example, the weight for Ref_A may be as in Equation 26 below.

[Equation 26]

As described above, the processing unit may derive the prediction value of the target pixel X by using one or more of the two reference pixels for the two prediction directions of the bidirectional intra prediction mode. In this case, the processor may use at least one of a distance weight and a direction weight for each reference pixel of the two reference pixels in the two prediction directions.

The distance weight may be a weight according to the distance between the reference pixel and the target pixel. The direction weight may be a weight according to a direction from the target pixel to the reference pixel.

In generating the derived prediction value Pred_X of the target block, the processing unit may use the aforementioned filtering for obtaining the reference pixel, and a distance weight and a direction weight together.

The reference pixel may be a pixel at a specified position along each prediction direction of the two prediction directions of the bi-directional intra prediction. The processing unit may obtain the reference pixel by performing filtering on one or more of surrounding pixels and/or virtual surrounding pixels of the specified location. Also, the processor may apply one or more of a distance weight and a direction weight to the generated reference pixel.

As illustrated in Equation 27 below, the prediction value Pred_X of the target pixel may be derived using one or more of Ref_A, Dis_A, Dir_A, Ref_B, Dis_B, and Dir_B.

[Equation 27]

Pred_X = F(Ref_A, Dis_A, Dir_A, Ref_B, Dis_B, Dir_B)

F() may be a specified function.

Dis_A may be the distance between the target pixel and Ref_A. Dir_A may be a direction for Ref_A. Dir_A may be the direction from the target pixel to Ref_A. Dis_B may be the distance between the target pixel and Ref_B. Dir_B may be a direction for Ref_B. Dir_B may be the direction from the target pixel to Ref_B.

The derived prediction value Pred_X of the target pixel may be a statistical value related to one or more of Ref_A, Dis_A, Dir_A, Ref_B, Dis_B, and Dir_B, and may be derived based on the statistical value.

As illustrated in Equation 28 below, the predicted value Pred_X of the target pixel may be derived based on distances of reference pixels from the target pixel and direction weights of the reference pixels.

[Equation 28]

A weight for one of the two reference pixels may be proportional to a distance between the target pixel and the other of the two reference pixels.

Also, a weight for one reference pixel among the two reference pixels may be proportional to a directional weight for the one reference pixel.

A weight for one of the two reference pixels may be inversely proportional to the sum of distances of the two reference pixels from the target pixel.

For example, the weight for Ref_B may be as in Equation 29 below.

[Equation 29]

For example, the weight for Ref_A may be as in Equation 30 below.

[Equation 30]

Derivation of intra prediction mode using MPM

In determining the intra prediction mode of the object block, the possibility that the intra prediction mode specified according to the coding parameter related to the object block is used for intra prediction of the object block may be high or low. Reflecting this possibility, the MPM list may be used.

The remaining modes may be intra prediction modes other than the MPMs in the MPM list. In other words, the residual modes may be intra prediction modes remaining except for one or more MPMs in the MPM list among all intra prediction modes.

The residual modes may be classified into a first residual mode set and a second residual mode set according to the probability of being used for intra prediction of a target block.

Residual modes that are more likely to be used for intra prediction of the target block may be defined as the first residual mode set. The first residual mode set may be referred to as a probabilistic residual mode. In other words, the probable residual mode may be intra prediction modes having a relatively high probability of being used as the intra prediction mode of the target block among the remaining intra prediction modes from which MPMs are excluded among all intra prediction modes.

Among all residual modes, residual modes not included in the first residual mode set may be defined as the second residual mode set. The second residual mode set may be referred to as a pure residual mode.

The residual mode indicator may indicate a residual mode used for intra prediction of a target block among residual modes. Alternatively, the residual mode indicator may indicate a residual mode used for intra prediction of a target block among residual modes of the probable residual mode.

30 illustrates determination of an intra prediction mode using a residual mode according to an embodiment.

In operation 3010, the processing unit may derive one or more MPMs for the target block.

The processing unit may derive one or more MPMs of the MPM list for the target block.

In operation 3020, the processor may determine whether the intra prediction mode of the target block is one of the MPMs.

The processor may determine whether the intra prediction mode of the target block is one of the MPMs by using the MPM use indicator. The processing unit may obtain the MPM usage indicator from the bitstream.

For example, the MPM usage indicator may have the same name as the prev_intra_pred_mode flag.

When the value of the MPM use indicator is a first value (eg, “1”), the processing unit may determine that the intra prediction mode of the target block is one of the MPMs.

When the value of the MPM use indicator is a second value (eg, “0”), the processing unit may determine that the intra prediction mode of the target block is not one of the MPMs.

When it is determined that the intra prediction mode of the target block is one of the MPMs, operation 3030 may be performed.

When it is determined that the intra prediction mode of the target block is not one of the MPMs, operation 3040 may be performed.

In operation 3030, the processor may determine an intra prediction mode for the target block using the MPM indicator.

The processing unit may obtain the MPM indicator from the bitstream.

The processing unit may determine an MPM indicated by the MPM indicator among one or more MPMs in the MPM list as the intra prediction mode for the target block.

For example, the MPM indicator may be an index to the MPM list.

In operation 3040 , the processing unit may derive one or more probable residual modes for the target block.

The processing unit may derive one or more probable residual modes of the list of probable residual modes for the target block.

In operation 3050, the processor may determine an intra prediction mode for the target block using the residual mode indicator.

The processing unit may obtain the residual mode indicator from the bitstream.

The processor may determine a probable residual mode indicated by the residual mode indicator among one or more probable residual modes of the probable residual mode list as the intra prediction mode for the target block.

For example, the residual mode indicator may be an index of the probable residual mode list.

As described above, the intra prediction mode for the target block may be determined based on a plurality of different lists of the MPM list and the probable residual mode list.

31 illustrates the determination of the intra prediction mode using the residual mode and inducing the MPM after determining whether to use the MPM according to an embodiment.

The order of steps 3010 and 3020 described above using FIG. 30 may be interchanged.

In operation 3110, the processing unit may determine whether the MPM is used for intra prediction of the target block.

Here, the use of the MPM for intra prediction of the target block means that 1) the intra prediction mode of the target block is one of the MPMs, 2) the intra prediction mode of the target block is one of the residual modes, and the residual mode It may mean a case where the MPM list is used for

The processing unit may determine whether the MPM is used for intra prediction of the target block by using the MPM use indicator. The processing unit may obtain the MPM usage indicator from the bitstream.

For example, the MPM usage indicator may have the same name as the prev_intra_pred_mode flag.

When the value of the MPM use indicator is a first value (eg, “1”), the processing unit may determine that the MPM is used for intra prediction of the target block.

When the value of the MPM use indicator is a second value (eg, “0”), the processing unit may determine that the MPM is not used for intra prediction of the target block.

The processing unit may determine whether the MPM is used for intra prediction of the target block by using the MPM indicator. The processing unit may determine that the MPM is used for intra prediction of the target block when the MPM indicator indicates one of the MPMs and the probable residual modes. If the MPM indicator does not indicate one of the MPMs and the probable residual modes, the processing unit may determine that the MPM is not used for intra prediction of the target block.

When it is determined that the MPM is used for intra prediction of the target block, operation 3120 may be performed.

When it is determined that the MPM is not used for intra prediction of the target block, the procedure may be terminated, and intra prediction may be performed by another method.

In operation 3120, the processing unit may derive one or more MPMs for the target block.

The processing unit may derive one or more MPMs of the MPM list for the target block.

In operation 3130, the processor may determine whether the probable residual mode is used for intra prediction of the target block.

Alternatively, the processor may determine which one of the MPM and the probable residual mode is used for intra prediction of the target block.

For example, when the MPM indicator indicates one of the probable residual modes, the processor may determine that the probabilistic residual mode is used for intra prediction of the target block.

For example, if the MPM indicator does not indicate one of the probable residual modes, the processor may determine that the probabilistic residual mode is not used for intra prediction of the target block.

For example, when the MPM indicator indicates one of the MPMs, the processing unit may determine that the MPM is used for intra prediction of the target block.

For example, when it is determined that the probable residual mode is used for intra prediction of the target block, operation 3150 may be performed.

For example, when it is determined that the MPM is used for intra prediction of the target block, operation 3140 may be performed.

For example, when it is determined that the intra prediction mode of the target block is one of the MPMs, operation 3140 may be performed.

For example, when it is determined that the intra prediction mode of the target block is one of the probable residual modes, operation 3150 may be performed.

Step 3140 may correspond to step 3030 . A duplicate description will be omitted.

Step 3150 may correspond to step 3040 . A duplicate description will be omitted.

Probable residual modes may be derived based on the MPMs derived in step 3120 . The relationship between the MPMs and the probabilistic residual modes and the derivation of the probabilistic residual modes under this relationship are described in detail below.

Step 3160 may correspond to step 3050 . A duplicate description will be omitted.

Steps 3040 and 3150 may be selectively performed. For example, the processor may determine whether the intra prediction mode of the target block is one of the probable residual modes by using the residual mode use indicator. The processing unit may obtain the residual mode usage indicator from the bitstream. When the value of the residual mode use indicator is a first value (eg, “1”), the processor may determine that the intra prediction mode of the target block is one of the probable residual modes. When the value of the residual mode use indicator is a second value (eg, “0”), the processor may determine that the intra prediction mode of the target block is not one of the probable residual modes. When it is determined that the intra prediction mode of the target block is one of the probable residual modes, operation 3040 or operation 3150 may be performed. When it is determined that the intra prediction mode of the target block is not one of the probable residual modes, the procedure ends, and another intra prediction that does not use the MPM and the probabilistic residual mode may be processed.

Induction of the probable residual mode

32 shows blocks for derivation of MPM candidates according to an example.

The processor may induce one or more of the remaining intra prediction modes except for the MPMs among all intra prediction modes as the probable residual mode.

The number of probable residual modes may be predefined. For example, the number of probable residual modes may be two or three.

For example, when the total intra prediction modes are 67 and MPMs are 6, the probable residual modes may be 2.

For example, when the total intra prediction modes are 67 and MPMs are 6, the probable residual modes may be 3.

These six MPM candidates (ie, candModeList[0] to candModeList[5]) may be derived as described below.

1) Code 1 below when the intra prediction mode (candIntraPredModeA) of the neighboring block A of the target block and the intra prediction mode (candIntraPredModeB) of the neighboring block B are the same and the intra prediction mode (candIntraPredModeA) of the neighboring block A is greater than INTRA_DC 6 MPM candidates can be derived as

[Code 1]

candModeList[0] = Intra prediction mode of neighboring block A (candIntraPredModeA)

candModeList[1] = INTRA_PLANAR

candModeList[2] = INTRA_DC

candModeList[3] = 2 + ((candIntraPredModeA + 61) % 64)

candModeList[4] = 2 + ((candIntraPredModeA - 1) % 64)

candModeList[5] = 2 + ((candIntraPredModeA + 60) % 64)

2) When the condition of 1) is not satisfied (that is, the intra prediction mode (candIntraPredModeA) of the neighboring block A and the intra prediction mode (candIntraPredModeB) of the neighboring block B) are not the same, and the intra prediction mode of the neighboring block A ( candIntraPredModeA) or the intra prediction mode (candIntraPredModeB) of the neighboring block B is greater than INTRA_DC), MPM candidates may be derived as shown in Codes 2 to 7 below.

[Code 2]

minAB = candModeList[(candModeList[0] > candModeList[1]) ? 1: 0]

maxAB = candModeList[(candModeList[0] > candModeList[1]) ? 0 : 1]

2-1) When both the intra prediction mode (candIntraPredModeA) of the neighboring block A and the intra prediction mode (candIntraPredModeB) of the neighboring block B are greater than INTRA_DC, MPM candidates may be derived as shown in Code 3 below.

[Code 3]

candModeList[0] = candIntraPredModeA

candModeList[1] = candIntraPredModeB

candModeList[2] = INTRA_PLANAR

candModeList[3] = INTRA_DC

If the derived difference value between MaxAB and MinAB falls within the range of 2 to 62, the 5th and 6th MPM candidates may be derived as shown in Code 4 below.

[Code 4]

candModeList[4] = 2 + ((maxAB + 61) % 64)

candModeList[5] = 2 + ((maxAB - 1 ) % 64)

If the derived difference value between MaxAB and MinAB does not fall within the range of 2 to 62, the 5th and 6th MPM candidates may be derived as shown in Code 5 below.

[Code 5]

candModeList[4] = 2 + ((maxAB + 60) % 64)

candModeList[5] = 2 + ((maxAB) % 64)

2-2) When the condition of 2-1) is not satisfied (that is, when at least one of the intra prediction mode (candIntraPredModeA) of the neighboring block A or the intra prediction mode (candIntraPredModeB) of the neighboring block B is greater than INTRA_DC), 6 MPM candidates can be derived as shown in Code 6 below.

[Code 6]

candModeList[0] = candIntraPredModeA

candModeList[1] = candIntraPredModeB

candModeList[2] = 1 - minAB

candModeList[3] = 2 + ((maxAB + 61) % 64 )

candModeList[4] = 2 + ((maxAB - 1 ) % 64)

candModeList[5] = 2 + ((maxAB + 60 ) % 64)

3) When the conditions of 1) and 2) are not satisfied, six MPM candidates may be derived as shown in code 7 below.

[Code 7]

candModeList[0] = candIntraPredModeA

candModeList[1] = (candModeList[0] == INTRA_PLANAR) ? INTRA_DC : INTRA_PLANAR

candModeList[2] = INTRA_ANGULAR50

candModeList[3] = INTRA_ANGULAR18

candModeList[4] = INTRA_ANGULAR46

candModeList[5] = INTRA_ANGULAR54

The processor may derive the probable residual mode based on the spatial neighboring block and the temporal neighboring block of the target block.

The processor may induce at least one intra prediction mode that does not belong to the MPMs among the intra prediction mode of the spatial neighboring block of the object block and the intra prediction mode of the temporal neighboring block of the object block as the probable residual mode.

For example, among neighboring blocks of the target block, the number of the intra prediction mode of one neighboring block is 30, the number of the other intra prediction mode is 40, and the intra prediction mode of No. 30 belongs to MPMs, If the intra-prediction mode No. 40 does not belong to the MPM, the intra-prediction mode No. 40 may be derived as a probable residual mode.

The processor may derive a probable residual mode based on selected MPMs among all MPMs.

The selected MPM may be a predefined number of MPMs preceding in order. Here, the MPM preceding in order may mean an intra prediction mode defined by a small number of bins. Alternatively, the MPM preceding in order may be the MPM having the smallest index in the MPM list.

In one embodiment, the predefined number of selected MPMs may be one.

The number of the derived probable residual mode may be the sum of the number of the first MPM and the offset. For example, when the number of the first MPM is 30, as the sum of the number 30 and the offset 1 is 31, the intra-prediction mode No. 31 may be derived as the probable residual mode.

The number of derived probable residual modes may be the difference between the number and offset of the first MPM. For example, when the number of the first MPM is 30, as the difference between the number 30 and the offset 1 is 29, the intra-prediction mode No. 29 may be derived as the probable residual mode.

The number of derived probable residual modes may be 1) the sum of the number and offset of the first MPM and 2) the difference between the number and the offset of the first MPM. For example, when the number of the first MPM is 30, the intra prediction mode No. 29 and the intra prediction mode No. 31 can be derived as probabilistic residual modes.

The number of derived probable residual modes may be 1) the sum of the number of the first MPM and the first offset and 2) the difference between the number of the first MPM and the first offset. For example, the first offset may be 1.

If 1) the number of the sum of the number of the MPM of the first and the number of the first offset or 2) the number of the difference between the number of the number of the MPM of the first and the number of the difference between the first offset is already one of the MPMs, 1) the number of the first An intra prediction mode having the number of the sum of the number of the MPM and the second offset or 2) the intra prediction mode having the number of the difference between the number of the first MPM and the second offset may be derived as the probabilistic residual mode. For example, the second offset may be two. Alternatively, the second offset may be different from the first offset. Alternatively, the second offset may be a value obtained by adding 1 to the first offset or a value obtained by adding a predefined number to the first offset.

For example, if the intra prediction mode having the number of the first MPM and the sum number of the first offset is already one of the MPMs, the intra prediction mode having the number of the sum of the number of the first MPM and the second offset is probable It can be derived as a residual mode.

For example, if the intra-prediction mode with the number of the difference between the number of the first MPM and the first offset is already one of the MPMs, the intra-prediction mode with the number of the difference between the number of the first MPM and the number of the second offset is already one of the MPMs. can be derived as a probabilistic residual mode.

In one embodiment, the predefined number of selected MPMs may be three.

For example, the processing unit adds an offset to the numbers of the first MPM, the second MPM, and the third MPM among the one or more MPMs in the MPM list, or subtracts the offset from the numbers in the probable residual mode. can determine their numbers.

For example, if the numbers of the first MPM, the second MPM and the third MPM are 30, 40 and 50, the numbers of the derived probable residual modes may be 31, 41 and 51.

When the specified mode is not included in the MPMs, the processing unit may derive the specified mode as a probable residual mode. For example, the specified mode may be a non-directional mode. The non-directional mode may be a DC mode and/or a Planar mode.

For example, when the DC mode is not included in the MPMs, the DC mode may be the first probable residual mode or the second probabilistic residual mode.

For example, when the planar mode is not included in the MPMs, the planar mode may be the first probable residual mode or the second probabilistic residual mode.

The processing unit may derive the probabilistic residual mode based on the directions of the MPMs.

For example, the processing unit may derive the intra prediction mode of the specified direction as the probabilistic residual mode based on the directions of the MPMs.

For example, the processing unit may derive an intra prediction mode having a direction not belonging to the directions of the MPMs as the probable residual mode according to the directions of the MPMs.

For example, when the MPMs are all intra prediction modes of the horizontal direction, the intra prediction mode of the vertical direction may be derived as the probable residual mode. The horizontal directional intra prediction mode may be an intra prediction mode in which a change in a horizontal component is greater than a change in a vertical component. The vertical direction intra prediction mode may be an intra prediction mode in which a change in a vertical component is greater than a change in a horizontal component.

For example, when the MPMs are all vertical directional intra prediction modes, the horizontal directional intra prediction mode or the horizontal intra prediction mode may be derived as the probable residual mode.

For example, when the MPMs are all horizontal intra prediction modes, a vertical intra prediction mode or a vertical intra prediction mode may be derived as a probable residual mode.

The processing unit may derive a probable residual mode based on statistical values of the selected MPMs. The selected MPM may be a predefined number of MPMs preceding in order.

In other words, an intra prediction mode with a number of statistical values can be derived as a probabilistic residual mode.

For example, an intra prediction mode having a number of the average value of the number of the first MPM and the number of the second MPM may be derived as the probabilistic residual mode. When the number of the first MPM is 30 and the number of the second MPM is 40, the intra prediction mode of No. 35 may be derived as the probable residual mode.

The processing unit may exclude a DC mode and a planar mode, which are non-directional modes, in deriving the probable residual mode based on the statistical values of the selected MPMs. Alternatively, when the processing unit selects an earlier predefined number of MPMs from among all MPMs, if there is an MPM of the non-directional mode among the predefined number of MPMs preceding in the order, the MPM of the non-directional mode is not selected, and the MPM of the following directional mode can be selected.

For example, the processing unit may calculate an average value of two MPMs preceding in order among all six MPMs, and derive an intra prediction mode having the number of the average value as the probable residual mode. When the 6 MPMs are DC mode, mode 30, planar mode, mode 10, mode 50, and mode 52, the MPM of the DC mode and the MPM of the planar mode may be excluded from selection. According to the above exclusion, MPM of No. 30 and MPM of No. 10, which are the two MPMs preceding in order, may be selected, and since the average of 30 and 10 is 20, the intra prediction mode of No. 20 can be derived as a probable residual mode.

The processing unit may derive the probable residual mode based on the statistical values of all MPMs. The number of intra prediction modes derived as probabilistic residual modes may be statistical values. For example, the total number of MPMs may be 6, and the statistical value may be an average value.

The processing unit may exclude a DC mode and a planar mode, which are non-directional modes, in deriving the probable residual mode based on the statistical values of the selected MPMs.

For example, the processor may derive the probable residual mode based on statistical values of the remaining MPMs except for the DC mode and the planar mode among all MPMs. An intra prediction mode with a number of statistical values may be derived as a probabilistic residual mode.

The processor may derive the probable residual mode by using the probable residual mode candidate list.

The probable residual mode candidate list may include one or more probabilistic residual mode candidates. The probable residual mode candidate list may be equally defined in the encoding apparatus 1600 and the decoding apparatus 1700 .

The processor may sequentially search the probable residual mode candidates in the probable residual mode candidate list, and may induce a probabilistic residual mode candidate that does not belong to the MPMs as the probabilistic residual mode.

Searching the probable residual mode candidates in order may mean that a probable residual mode candidate having a smaller index in the probabilistic residual mode candidate list is searched before a probable residual mode candidate having a larger index.

The number of probable residual mode candidates derived to the probable residual mode among the probable residual mode candidates in the probable residual mode candidate list may be predefined.

For example, probable residual mode candidates are defined in the order of 30 intra prediction modes, 40 intra prediction modes, 50 intra prediction modes, 20 intra prediction modes, and 10 intra prediction modes, and 30 intra prediction modes and when the intra prediction mode No. 40 belongs to the MPMs, if the number of probable residual mode candidates derived from the probable residual mode is 1, the intra prediction mode No. 50 may be derived as the probable residual mode.

Alternatively, when the probable residual mode candidates are defined as described above, and when the 30 intra prediction mode and the 40 intra prediction mode belong to the MPMs, if the number of probable residual mode candidates derived from the probable residual mode is 3, 50 times The intra-prediction mode, the intra-prediction mode of 20 times, and the intra-prediction mode of No. 10 may be derived as the first probable residual mode, the second probable residual mode, and the third probable residual mode, respectively.

The processor may induce at least one intra prediction mode as a probable residual mode based on an intra prediction mode number among residual mode candidates.

For example, in ascending order from the mode having the lowest intra prediction mode number among 61 residual mode candidates from which 6 MPM candidate modes are excluded among 67 intra prediction modes, the first probable residual mode, the second probable residual mode, and the second probable residual mode Three probable residual modes can each be derived. For example, when the number of intra prediction modes is 67 and the MPMs are 6 of (20, 30, 0, 1, 31, 32), the first residual mode is the residual mode (2, 3, 4, ... , 19, 21, 22 ..., 29, 33, 34, ..., 66) to be defined as residual modes (2, 3, 4) which are three residual modes having the lowest intra prediction mode number among can

For example, the first probabilistic residual mode, the second probable residual mode, and the second probable residual mode in descending order from the mode having the largest intra prediction mode number among the 61 residual mode candidates from which 6 MPM candidate modes are excluded among the 67 intra prediction modes Three probable residual modes can each be derived.

Determination of intra prediction mode using residual mode indicator

33 illustrates binarization of a residual mode indicator according to an example.

In FIG. 33 , a symbol of the residual mode indicator and a truncated binary are shown, and a residual mode indicated by the symbol and the truncated binary is shown.

The processor may determine the intra prediction mode of the target block by using the residual mode indicator.

The intra prediction mode indicated by the residual mode indicator may include both the probabilistic residual mode and the pure residual mode. In other words, the residual mode indicator may indicate one residual mode among the probabilistic residual modes and the pure residual modes as the intra prediction mode of the object block.

The residual mode indicator may be a value binarized by a truncated binary coding method.

33 , the number of bins in the probable residual mode and the number of bins in the pure residual mode may be different from each other.

For example, the probable residual modes may be two.

For example, when the total number of intra prediction modes is 67 and MPMs are 6, the number of probable residual modes may be 2 and the number of pure residual modes may be 59. That is, among all intra prediction modes, intra prediction modes that do not belong to the MPM may be classified into two probabilistic residual modes and 59 pure residual modes.

Probable residual modes may have 5 bins, and pure residual modes may have 6 bins.

In one embodiment, the bins for the two probable residual modes may be defined as “00000” and “00001”. “00000” may indicate the first probable residual mode. “00001” may indicate the second probable residual mode.

The bins for the 59 pure residual modes may be defined as 6 bins excluding “000000”, “000001”, “000010” and “000011”. For example, bins for the pure residual mode may include “000100” and “000101”, and the like.

The processor may encode and/or decode the residual mode indicator using the binarized value as described above.

In another embodiment, the bins for the two probable residual modes may be defined as “11110” and “11111”. “11110” may indicate the first probable residual mode. “11111” may indicate the second probable residual mode.

The bins for the 59 pure residual modes may be defined as 6 bins excluding “111100”, “111101”, “111110” and “111111”. For example, bins for the pure residual mode may include “111000” and “111001”, and the like.

The processing unit may encode and/or decode the residual mode indicator using the binarized value as described above.

When the total number of intra prediction modes is 67 and MPMs are 6, the number of probable residual modes may be 3 and the number of pure residual modes may be 58. That is, among all intra prediction modes, intra prediction modes that do not belong to the MPM may be classified into 3 probabilistic residual modes and 58 pure residual modes.

Probable residual modes may have 5 bins, and pure residual modes may have 6 bins.

In one embodiment, the bins for the three probable residual modes may be defined as “00000”, “00001” and “00010”. “00000” may indicate the first probable residual mode. “00001” may indicate the second probable residual mode. “00010” may indicate the third probable residual mode.

The bins for the 58 pure residual modes may be defined as the sum of a binary value and an offset of 3. For example, bins for a pure residual mode would include "000110" (= "000011" + "000011"), "000111" (= "000100" + "000011"), "001000" and "001001", etc. can

The processor may encode and/or decode the residual mode indicator using the binarized value as described above.

34 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 1600 . The embodiment may be a part of a method for encoding a target block or a method for encoding a video.

In operation 3410 , the processor 1610 may determine an intra prediction mode to be applied to encoding the target block.

Step 3410 may correspond to step 1810 described above with reference to FIG. 18 . Also, step 3410 may correspond to steps 3010 , 3020 , 3030 , 3040 and 3050 described above with reference to FIG. 30 . Also, step 3410 may correspond to steps 3110 , 3120 , 3130 , 3140 , and 3150 described above with reference to FIG. 31 .

The determined intra prediction mode may be 1) an intra prediction mode using a bidirectional intra prediction mode and/or 2) a residual mode.

Intra prediction may be 1) bi-directional intra prediction and/or 2) intra prediction using residual mode.

The processor 1610 may determine the intra prediction mode of the target block in consideration of rate-distortion costs for intra prediction modes among available intra prediction modes for the target block.

In operation 3420 , the processor 1610 may perform intra prediction on the target block using the determined intra prediction mode.

Step 3420 may correspond to step 1820 described above with reference to FIG. 18 .

Information on the encoded object block may be generated by performing intra prediction on the object block using the intra prediction mode.

A prediction block may be generated by intra prediction of the target block using the intra prediction mode, and a residual block that is a difference between the target block and the prediction block may be generated. By applying transform and quantization to the residual block, information on the encoded target block may be generated.

The encoded information on the object block may include transform and quantized coefficients for the object block. The encoded information on the target block may include coding parameters for the target block.

In operation 3430 , the processing unit 1610 may generate a bitstream.

The bitstream may include information on the encoded target block.

The bitstream may include prediction information. The prediction information may be information for bi-directional intra prediction and/or intra prediction using residual mode. In other words, the prediction information may include coding parameters related to the target block for intra prediction described in the embodiment.

For example, prediction information, for bidirectional intra prediction, 1) unidirectional/bidirectional discrimination indicator, 2) intra prediction mode indicator, 3) weight for reference pixel, 4) MPM use indicator, 5) MPM indicator, 6) It may include a predefined angle α and the like.

For example, the prediction information may include 1) an MPM use indicator, 2) an MPM indicator, 3) a residual mode indicator, and 4) a residual mode use indicator for intra prediction using the residual mode.

Prediction information may be generated at step 3430 , or at least partially generated at steps 3410 and 3420 .

The processing unit 1610 may store the generated bitstream in the storage 1640 . Alternatively, the communication unit 1620 may transmit the bitstream to the decoding apparatus 1700 .

The processing unit 1610 may perform entropy encoding on the prediction information and may generate a bitstream including the entropy-encoded prediction information.

The embodiment may be combined with the operation of the encoding apparatus 100 described above with reference to FIG. 1 . For example, the operations of steps 3410 and 3420 may be performed by the intra prediction unit 120 . The operations of step 3430 may be performed by the entropy encoder 150 . Also, operations performed in other components of the encoding apparatus 100 before, after, and between steps 3410 , 3420 , and 3430 may be performed.

35 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 1700 . The embodiment may be a part of a method for decoding a target block or a method for decoding a video.

In operation 3510, the communication unit 1720 may obtain a bitstream. The communication unit 1720 may receive a bitstream from the encoding apparatus 1600 .

The bitstream may include information on the encoded target block.

The encoded information on the object block may include transform and quantized coefficients for the object block. The encoded information on the target block may include coding parameters for the target block.

The bitstream may include prediction information. The prediction information may be information for bi-directional intra prediction and/or intra prediction using residual mode. In other words, the prediction information may include coding parameters related to the target block for intra prediction described in the embodiment.

For example, prediction information, for bidirectional intra prediction, 1) unidirectional/bidirectional discrimination indicator, 2) intra prediction mode indicator, 3) weight for reference pixel, 4) MPM use indicator, 5) MPM indicator, 6) It may include a predefined angle α and the like.

For example, the prediction information may include 1) an MPM use indicator, 2) an MPM indicator, 3) a residual mode indicator, and 4) a residual mode use indicator for intra prediction using the residual mode.

The processing unit 1710 may store the obtained bitstream in the storage 1740 .

The processing unit 1710 may obtain prediction information from the bitstream. The processing unit 1710 may obtain prediction information by performing entropy decoding on the entropy-encoded prediction information of the bitstream.

In operation 3520 , the processor 1710 may determine an intra prediction mode to be applied to decoding of the target block.

Step 3520 may correspond to step 1810 described above with reference to FIG. 18 . Also, step 3520 may correspond to steps 3010 , 3020 , 3030 , 3040 and 3050 described above with reference to FIG. 30 . Also, step 3520 may correspond to steps 3110 , 3120 , 3130 , 3140 , and 3150 described above with reference to FIG. 31 .

The determined intra prediction mode may be 1) an intra prediction mode using a bidirectional intra prediction mode and/or 2) a residual mode.

Intra prediction may be 1) bi-directional intra prediction and/or 2) intra prediction using residual mode.

The processor 1710 may determine the intra prediction mode of the target block based on the prediction information.

In operation 3530 , the processor 1710 may perform intra prediction on the object block using the encoded information on the object block and the determined intra prediction mode.

Step 3530 may correspond to step 1820 described above with reference to FIG. 18 . Also, in operation 3530 , a prediction block may be generated by performing intra prediction on the target block using the intra prediction mode, and a reconstructed block that is the sum of the prediction block and the reconstructed residual block may be generated.

The embodiment may be combined with the operation of the decoding apparatus 200 described above with reference to FIG. 2 . For example, the operations of step 3510 may be performed by the entropy decoding unit 210 . The operations of steps 3520 and 3530 may be performed by the intra prediction unit 240 . In addition, operations performed in other components of the decryption apparatus 200 before, after, and between steps 3510 , 3520 , and 3530 may be performed.

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 in 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.

A computer-readable recording medium may contain information used in embodiments according to the present invention. For example, the computer-readable recording medium may include a bitstream, and the bitstream may include the information described in the embodiments according to the present invention.

The computer-readable recording medium may include a non-transitory computer-readable medium.

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 and 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 for carrying out the 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. , various modifications and variations can be devised from these descriptions by those of ordinary skill in the art to which the present invention pertains.

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 (21)

determining a prediction mode for the target block; and
performing prediction on the target block using the reference pixel determined by the prediction mode
including
the reference pixel comprises a first reference pixel and a second reference pixel;
the first reference pixel and the second reference pixel are not adjacent to the target block;
the x-coordinate of the first reference pixel and the x-coordinate of the second reference pixel are different from each other;
The y-coordinate of the first reference pixel and the y-coordinate of the second reference pixel are different from each other. According to claim 1,
and the first reference pixel and the second reference pixel are determined by the direction of the prediction mode. 3. The method of claim 2,
and the prediction is performed using a first weight for a first reference value determined by the first reference pixel and a second weight for a second reference value determined by the second reference pixel. 4. The method of claim 3,
The first weight is determined based on a distance between a target pixel of the target block and the first reference pixel,
and the second weight is determined based on a distance between the target pixel and the second reference pixel. 5. The method of claim 4,
and the first weight and the second weight are determined based on the direction. 3. The method of claim 2,
wherein the direction is a diagonal direction. The method of claim 1,
The prediction is performed by a plurality of different prediction methods. delete determining a prediction mode for the target block; and
performing prediction on the target block using the reference pixel determined by the prediction mode
including
It is determined whether at least one first prediction mode is used as the prediction mode for the target block,
when the at least one first prediction mode is not used as the prediction mode, a list with one or more second prediction modes is used as the prediction mode for the target block,
The at least one first prediction mode is not included in the list,
At least some of the one or more second prediction modes are intra prediction modes of a spatial neighboring block of the target block. delete 10. The method of claim 9,
It is determined whether to perform the prediction using the list including one or more MPMs,
When the prediction is not performed using the list, the prediction is performed using the selected residual mode indicated by the residual mode indicator among the residual modes,
the remaining modes do not include the one or more MPMs,
A decoding method in which the value of the residual mode indicator is binarized using a truncated binary coding method. 12. The method of claim 11,
The remaining modes are 61,
The bins for the residual modes are “00000”, “00001”, “00010”, “000110”, “000111”, “001000”, “001001”, “001010”, “001011”, “001100”, “001101” ", "001110", "001111", "010000", "010001", "010010", "010011", "010100", "010101", "010110", "010111", "011000", "011001", "011010", "011011", "011100", "011101", "011110", "011111", "100000", "100001", "100010", "100011", "100100", "100101", "100110"","100111","101000","101001","101010","101011","101100","101101","101110","101111","110000","110001","110010","110011","110100","110101","110110","110111","111000","111001","111010","111011","111100","111101","111110" and "111111""In the decryption method. determining a prediction mode for the target block; and
performing prediction on the target block using the reference pixel determined by the prediction mode
including
the reference pixel comprises a first reference pixel and a second reference pixel;
the first reference pixel and the second reference pixel are not adjacent to the target block;
the x-coordinate of the first reference pixel and the x-coordinate of the second reference pixel are different from each other;
The y-coordinate of the first reference pixel and the y-coordinate of the second reference pixel are different from each other. 14. The method of claim 13,
and the first reference pixel and the second reference pixel are determined by the direction of the prediction mode. 15. The method of claim 14,
the prediction is performed using a first weight for a first reference value determined by the first reference pixel and a second weight for a second reference value determined by the second reference pixel;
The first weight is determined based on a distance between a target pixel of the target block and the first reference pixel,
and the second weight is determined based on a distance between the target pixel and the second reference pixel. 14. The method of claim 13,
The prediction is performed by a plurality of different prediction methods. delete determining a prediction mode for the target block; and
performing prediction on the target block using the reference pixel determined by the prediction mode
including
It is determined whether the prediction mode for the target block is at least one first prediction mode,
If the prediction mode is not the at least one first prediction mode, the prediction mode for the target block is one prediction mode in a list having one or more second prediction modes,
The at least one first prediction mode is not included in the list,
At least some of the one or more second prediction modes are intra prediction modes of a spatial neighboring block of the target block. A recording medium for recording a bitstream generated by the encoding method according to claim 18. A computer-readable recording medium for storing a bitstream, comprising:
The bitstream is
Encoded information about the target block
including,
Decoding is performed on the target block using the encoded information,
A prediction mode for the target block is determined,
Prediction is performed on the target block using the reference pixel determined by the prediction mode,
the reference pixel comprises a first reference pixel and a second reference pixel;
the first reference pixel and the second reference pixel are not adjacent to the target block;
the x-coordinate of the first reference pixel and the x-coordinate of the second reference pixel are different from each other;
The y-coordinate of the first reference pixel and the y-coordinate of the second reference pixel are different from each other. A computer-readable recording medium for storing a bitstream, comprising:
The bitstream is
Encoded information about the target block
including,
Decoding is performed on the target block using the encoded information,
A prediction mode for the target block is determined,
Prediction is performed on the target block using the reference pixel determined by the prediction mode,
It is determined whether the prediction mode for the target block is at least one first prediction mode,
If the prediction mode is not the at least one first prediction mode, the prediction mode for the target block is one prediction mode in a list having one or more second prediction modes,
The at least one first prediction mode is not included in the list,
At least some of the one or more second prediction modes are intra prediction modes of a spatial neighboring block of the target block.

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