CN110024386B - Method and apparatus for encoding/decoding image, recording medium for storing bit stream - Google Patents

Abstract

The present invention relates to a method and device for encoding/decoding images. A method for decoding an image according to the present invention includes the steps of: dividing a current block into one or more sub-blocks; using an intra prediction mode of the current block and an intra prediction mode of a neighboring block adjacent to the current block. to derive an intra prediction mode for each of the one or more sub-blocks; using the derived intra prediction mode to perform a frame prediction on each of the one or more sub-blocks intraprediction.

Description

Methods and devices for encoding/decoding images, storing bitstreams recording medium

Technical field

The present invention relates to a method and device for encoding/decoding images. Specifically, the present invention relates to a method and device for encoding/decoding images using intra prediction and a recording medium that stores a bit stream generated by the image encoding method/device of the present invention.

Background technique

Recently, demand for high-resolution and high-quality images, such as high-definition (HD) images and ultra-high-definition (UHD) images, has increased in various application fields. However, higher resolution and quality image data increase the amount of data compared to traditional image data. Therefore, when image data is transmitted by using media such as conventional wired and wireless broadband networks, or when image data is stored by using conventional storage media, costs of transmission and storage increase. In order to solve these problems that occur as the resolution and quality of image data increase, an efficient image encoding/decoding technology for higher resolution and higher quality images is required.

Image compression technology includes various technologies including: inter prediction technology that predicts pixel values included in the current picture from a previous picture or a subsequent picture of the current picture; Intra-frame prediction techniques include predicting pixel values in the current picture; transformation and quantization techniques for compressing the energy of the residual signal; assigning short codes to values with high frequency of occurrence and long codes to values with high frequency of occurrence. Entropy coding techniques for low-frequency values; etc. Image data can be efficiently compressed by using such image compression technology, and can be transmitted or stored.

Contents of the invention

technical problem

An object of the present invention is to provide a method and device for encoding and decoding images to improve compression efficiency and a recording medium that stores a bit stream generated by the image encoding method/device of the present invention.

Another object of the present invention is to provide a method and device for encoding and decoding images using intra prediction to improve compression efficiency and a recording medium that stores a bit stream generated by the image encoding method/device of the present invention.

Another object of the present invention is to provide a method and device for encoding and decoding images using a transformation model, an isospace model or a bilinear interpolation model to perform intra prediction and to store the images generated by the image encoding method/device of the present invention. Bit stream recording medium.

Technical solutions

An image decoding method according to the present invention may include: partitioning a current block into one or more sub-blocks; by using at least one of an intra prediction mode of the current block and an intra prediction mode of a neighboring block adjacent to the current block. one to derive an intra prediction mode for each of the one or more sub-blocks; and perform frame prediction on each of the one or more sub-blocks using the derived intra prediction mode. intraprediction.

In the image decoding method according to the present invention, the step of deriving the intra prediction mode may include generating an intra prediction mode for the current block by using at least one of an intra prediction mode of the current block and an intra prediction mode of a neighboring block. a prediction direction field (IPDF); and deriving an intra prediction mode for each of the one or more sub-blocks by using the generated IPDF.

In the image decoding method according to the present invention, the IPDF may be generated using a transformation model, and the transformation model may include at least one of rigid body transformation, similarity transformation, affine transformation, homography transformation and 3D transformation.

In the image decoding method according to the present invention, the intra prediction mode of the neighboring block used in the step of generating the IPDF may be a seed point intra prediction mode (SPIPM) of the seed block including the seed point, and may be based on the current block or The size or shape of the sub-block adaptively determines the seed points.

In the image decoding method according to the present invention, a list of SPIPMs may be configured, wherein the list of SPIPMs includes intra prediction modes of adjacent blocks that are SPIPM candidates, and may be selected from the list of SPIPMs in accordance with the number of SPIPMs required to generate the IPDF. Select SPIPM.

In the image decoding method according to the present invention, among neighboring blocks, when there is a neighboring block for which an intra prediction mode is derived using IPDF, the IPDF of the current block may be generated based on the IPDF of the neighboring block.

In the image decoding method according to the present invention, the intra prediction mode of the outermost sub-block located at the current block may be derived using the intra prediction mode of the adjacent block, and the intra prediction mode of the outermost sub-block located at the current block may be derived. Prediction modes are used to derive intra prediction modes of at least one remaining sub-block, and intra prediction modes of two sub-blocks located in outermost sub-blocks of the current block and intra prediction modes of the remaining sub-blocks may be equally spatially derived.

In the image decoding method according to the present invention, the intra prediction mode of the outermost sub-block located at the current block may be derived using the intra prediction mode of the adjacent block, and the intra prediction mode of the outermost sub-block located at the current block may be derived. prediction mode to derive the intra prediction mode of at least one remaining sub-block, and the intra prediction mode of the remaining sub-block may be derived by bilinear interpolation of the intra prediction modes of two sub-blocks located in the outermost sub-block of the current block Prediction mode.

An image decoding device according to the present invention may include an intra prediction unit configured to: partition a current block into one or more sub-blocks; to derive an intra prediction mode for each of the one or more sub-blocks by using at least one of the intra prediction modes of neighboring neighboring blocks; and by using the derived intra prediction modes for the one or more sub-blocks Each of the plurality of sub-blocks performs intra prediction.

An image encoding method according to the present invention may include: partitioning a current block into one or more sub-blocks; by using at least one of an intra prediction mode of the current block and an intra prediction mode of a neighboring block adjacent to the current block. one to determine an intra prediction mode for each of the one or more sub-blocks; and perform intra prediction on each of the one or more sub-blocks by using the determined intra prediction mode. predict.

In the image encoding method according to the present invention, the step of determining the intra prediction mode may include generating an intra prediction mode for the current block by using at least one of an intra prediction mode of the current block and an intra prediction mode of a neighboring block. a prediction direction field (IPDF); and determining an intra prediction mode for each of the one or more sub-blocks by using the generated IPDF.

In the image encoding method according to the present invention, the IPDF may be generated using a transformation model, and the transformation model may include at least one of rigid body transformation, similarity transformation, affine transformation, homography transformation and 3D transformation.

In the image encoding method according to the present invention, the intra prediction mode of the neighboring block used in the step of generating the IPDF may be a seed point intra prediction mode (SPIPM) of the seed block including the seed point, and may be based on the current block or The size or shape of the sub-block adaptively determines the seed points.

In the image encoding method according to the present invention, a list of SPIPMs may be configured, wherein the list of SPIPMs includes intra prediction modes of adjacent blocks that are SPIPM candidates, and may be selected from the list of SPIPMs in accordance with the number of SPIPMs required to generate the IPDF. Select SPIPM.

In the image encoding method according to the present invention, among neighboring blocks, when there is a neighboring block for which an intra prediction mode is derived using IPDF, the IPDF of the current block may be generated based on the IPDF of the neighboring block.

In the image encoding method according to the present invention, the intra prediction mode of the sub-block located at the outermost side of the current block may be determined using the intra prediction mode of the neighboring block, and the intra prediction mode of the sub-block located at the outermost side of the current block may be determined. The prediction mode is used to determine the intra prediction mode of at least one remaining sub-block, and the intra prediction modes of two sub-blocks located in the outermost sub-block of the current block and the intra prediction mode of the remaining sub-block may be equally spatially determined.

In the image encoding method according to the present invention, the intra prediction mode of the sub-block located at the outermost side of the current block may be determined using the intra prediction mode of the neighboring block, and the intra prediction mode of the sub-block located at the outermost side of the current block may be determined. The prediction mode is used to determine the intra prediction mode of at least one remaining sub-block, and the intra prediction mode of the remaining sub-block may be determined by bilinear interpolation of the intra prediction modes of two sub-blocks located in the outermost sub-block of the current block. Prediction mode.

An image encoding device according to the present invention may include an intra prediction unit configured to: partition a current block into one or more sub-blocks; determine the intra prediction mode of each of the one or more sub-blocks by using at least one of the intra prediction modes of adjacent neighboring blocks; and use the determined intra prediction mode to determine the intra prediction mode of the one or more sub-blocks. Each of the plurality of sub-blocks performs intra prediction.

A computer-readable recording medium according to the present invention can store a bit stream generated by the image encoding method of the present invention.

beneficial effects

According to the present invention, it is possible to provide an image encoding/decoding method and device with improved compression efficiency and a recording medium that stores a bit stream generated by the image encoding method/device of the present invention.

And, according to the present invention, it is possible to provide an image encoding/decoding method and device using intra prediction with improved compression efficiency and a recording medium that stores a bit stream generated by the image encoding method/device of the present invention.

And, according to the present invention, it is possible to provide an image encoding/decoding method and apparatus that performs intra prediction using a transformation model, an isospace model, or a bilinear interpolation model and a method for storing a bit stream generated by the image encoding method/apparatus of the present invention. recording media.

Description of the drawings

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

2 is a block diagram showing the configuration of a decoding device according to an embodiment of the present invention.

FIG. 3 is a diagram schematically showing a partition structure of an image when encoding and decoding the image.

FIG. 4 is a diagram showing intra prediction processing.

FIG. 5 is a diagram illustrating a method of performing intra prediction on a current block according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating an embodiment of deriving an intra prediction mode of a current block using SPIPM.

FIG. 7 is a diagram illustrating an embodiment of constructing a SPIPM list including two SPIPMs.

FIG. 8 is an exemplary diagram illustrating an embodiment of constructing a SPIPM list including three SPIPMs.

FIG. 9 is an exemplary diagram illustrating an embodiment of constructing a SPIPM list including four SPIPMs.

FIG. 10 is an exemplary diagram showing the sub-block size in the case where the size of the current block is 16×16.

FIG. 11 is a diagram illustrating an embodiment of allocating an intra prediction mode using a determined IPDF.

FIG. 12 is an exemplary diagram showing reconstructed blocks adjacent to the current block.

FIG. 13 is a diagram illustrating an embodiment of deriving an intra prediction mode using neighboring reconstructed blocks.

FIG. 14 is a diagram illustrating an embodiment of deriving a sub-block based intra prediction mode.

FIG. 15 is a diagram illustrating another embodiment of deriving a sub-block based intra prediction mode.

Figure 16 is an exemplary diagram illustrating adjacent reconstructed sample lines that may be used for intra prediction of the current block.

FIG. 17 is a diagram illustrating an embodiment of constructing reference samples for sub-blocks included in the current block.

FIG. 18 is a diagram illustrating a method of replacing unavailable reconstruction sample points with available reconstruction sample points.

FIG. 19 is an exemplary diagram illustrating intra prediction according to the shape of the current block.

Detailed ways

invention pattern

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

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

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

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

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

Furthermore, some constituent elements may not be indispensable for performing the necessary functions of the present invention, but may be optional constituents that merely enhance its performance. The present invention can be implemented by including only components indispensable for implementing the essence of the present invention and not including components for improving performance. A structure including only the indispensable components and not optional components merely for improving performance is also included in the scope of the present invention.

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

Furthermore, in the following, an image may mean a picture constituting a video, or may mean the video itself. For example, "encode or decode an image, or both," may mean "encode or decode a video, or both," and may mean "encode one of a plurality of images of a video." or decoding or encoding and decoding”. Here, picture and image may have the same meaning.

Terminology description

Encoder: means the device that performs encoding.

Decoder: means the device that performs decoding.

Block: is the sample point of M×N matrix. Here, M and N mean positive integers, and a block may mean a sample matrix in two-dimensional form. Blocks can represent units. The current block may mean an encoding target block that is targeted when encoding or a decoding target block that is targeted when decoding. Furthermore, the current block may be at least one of a coding block, a prediction block, a residual block, and a transformation block.

Sample point: It is the basic unit that constitutes a block. It can be expressed as a value ranging from 0 to 2 ^Bd –1 in terms of bit depth (Bd). In the present invention, sample points can be used as the meaning of pixels.

Unit: means encoding and decoding unit. When encoding and decoding images, cells can be regions produced by partitioning a single image. Furthermore, a unit may mean a sub-split unit when a single image is partitioned into a plurality of sub-split units during encoding or decoding. When encoding and decoding images, predetermined processing for each unit may be performed. A cell can be partitioned into sub-cells that are smaller in size than the size of the cell. Depending on the function, a unit may mean a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding block, a prediction unit, a prediction block, a residual unit, a residual block, a transform unit, a transform block, etc. Furthermore, to distinguish units from blocks, a unit may include a luma component block, a chrominance component block associated with the luma component block, and syntax elements for each color component block. The units may have various sizes and shapes. Specifically, the units may be in the form of two-dimensional geometric figures, such as rectangles, squares, trapezoids, triangles, pentagons, etc. Furthermore, the unit information may include at least one of unit type (indicating coding unit, prediction unit, transformation unit, etc.), unit size, unit depth, order of encoding and decoding the unit, and the like.

Coding tree unit: configured with a single coding tree block of the luminance component Y and two coding tree blocks related to the two components Cb and Cr. Furthermore, it may mean including blocks and syntax elements of each block. Each coding tree unit may be partitioned by using at least one of a quadtree partitioning method and a binary tree partitioning method to configure lower layer units such as coding units, prediction units, transformation units, and the like. Coding tree unit may be used as a term for specifying a pixel block that becomes a processing unit in decoding/encoding an image as an input image.

Coding tree block: may be used as a term for specifying any one of Y coding tree block, Cb coding tree block, and Cr coding tree block.

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

Reconstructed neighboring blocks: means neighboring blocks that are adjacent to the current block and have been encoded or decoded in space/time. Here, reconstructing neighboring blocks may mean reconstructing neighboring units. Reconstructed spatial neighboring blocks may be blocks that are within the current picture and have been reconstructed by encoding or decoding or both encoding and decoding. A reconstruction temporal neighboring block is a block within the reference picture that is at the same position as the current block of the current picture or a neighboring block of that block.

Cell depth: means the degree to which the cell is partitioned. In a tree structure, the root node can be the highest node and the leaf node can be the lowest node. In addition, when the unit is expressed as a tree structure, the level at which the unit is located may mean the unit depth.

Bitstream: means a bitstream containing encoded image information.

Parameter set: corresponds to the header information in the bitstream configuration. At least one parameter set of a video parameter set, a sequence parameter set, a picture parameter set, and an adaptation parameter set may be included in the parameter set. In addition, the parameter set may include slice header and tile header information, etc.

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

Symbol: may mean at least one of syntax elements, encoding parameters, and transform coefficient values of the encoding/decoding target unit. Furthermore, the symbol may mean an entropy encoding target or an entropy decoding result.

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

Prediction unit partitioning: means the form obtained by partitioning the prediction unit.

Transform unit: means a basic unit when performing encoding/decoding such as transform, inverse transform, quantization, inverse quantization, transform coefficient encoding/decoding on the residual signal. A single transformation unit can be partitioned into multiple transformation units with small sizes.

Scaling: means the process of multiplying a factor by the transformation coefficient level. Transform coefficients can be generated by scaling transform coefficient levels. Scaling may also be called inverse quantization.

Quantization parameter: may mean a value used during quantization when generating transform coefficient levels of transform coefficients. The quantization parameter may mean a value used when generating transform coefficients by scaling transform coefficient levels during inverse quantization. The quantization parameter may be a step size value that is mapped to quantization.

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

Scan: Means a method of sorting the coefficients within a block or matrix. For example, an operation of changing the coefficients of a two-dimensional matrix into a one-dimensional matrix may be called a scan, and an operation of changing the coefficients of a one-dimensional matrix into a two-dimensional matrix may be called a scan or inverse scan.

Transform coefficients: May mean the coefficient values produced after performing a transform in the encoder. It may mean coefficient values generated after at least one of entropy decoding and inverse quantization is performed in the decoder. A quantization level obtained by quantizing a transform coefficient or a residual signal or a quantized transform coefficient level may also fall within the meaning of a transform coefficient.

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

Non-zero transform coefficient: means a transform coefficient with a value other than 0 or a transform coefficient level with a value other than 0.

Quantization matrix: means a matrix used in quantization processing and inverse quantization processing to improve subject image quality or object image quality. The quantization matrix may also be called a scaling list.

Quantization matrix coefficient: means quantizing each element in the matrix. Quantized matrix coefficients may also be called matrix coefficients.

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

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

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

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

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

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

When the prediction mode is the intra mode, the intra prediction unit 120 may use pixel values of blocks that have been encoded/decoded and are adjacent to the current block as reference pixels. Intra prediction unit 120 may perform spatial prediction by using reference pixels, or may generate prediction samples of the input block by performing spatial prediction. Here, intra prediction may mean intra-prediction.

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

Motion compensation unit 112 may generate prediction blocks by performing motion compensation using motion vectors. Here, inter prediction may mean inter-prediction or motion compensation.

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

The subtractor 125 may generate a residual block by using the residuals of the input block and the prediction block. The residual block may be called a residual signal. The residual signal may mean the difference between the original signal and the predicted signal. Furthermore, the residual signal may be a signal generated by transforming or quantizing or transforming and quantizing the difference between the original signal and the predicted signal. The residual block may be a block-unit residual signal.

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

Quantization levels can be generated by applying quantization to transform coefficients or residual signals. Hereinafter, in embodiments, the quantized levels may be referred to as transform coefficients.

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

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

When entropy coding is applied, the size of the bit stream for symbols to be encoded can be reduced by allocating a small number of bits to symbols with high probability of occurrence and a large number of bits to symbols with low probability of occurrence to represent symbols. The entropy encoding unit 150 may use an encoding method for entropy encoding, such as Exponential Golomb, Context Adaptive Variable Length Coding (CAVLC), Context Adaptive Binary Arithmetic Coding (CABAC), and the like. For example, the entropy encoding unit 150 may perform entropy encoding by using a variable length coding/coding (VLC) table. In addition, the entropy encoding unit 150 may derive a binarization method of the target symbol and a probability model of the target symbol/bin, and may perform arithmetic coding by using the derived binarization method and the context model.

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

Encoding parameters may include information such as syntax elements (flags, indices, etc.) that are encoded in the encoder and signaled to the decoder and information derived when encoding or decoding is performed. Encoding parameters may mean information necessary when encoding or decoding an image. For example, the encoding parameters may include at least one value or combination of the following items: unit/block size, unit/block depth, unit/block partition information, unit/block partition structure, whether to perform partitioning in the form of a quadtree, whether to perform Partitioning in binary tree form, partitioning direction in binary tree form (horizontal or vertical direction), partitioning form in binary tree form (symmetric partitioning or asymmetric partitioning), intra prediction mode/direction, reference sample filtering method, prediction block filtering method, Prediction block filter tap, prediction block filter coefficient, inter prediction mode, motion information, motion vector, reference picture index, inter prediction angle, inter prediction indicator, reference picture list, reference picture, motion vector predictor candidate , motion vector candidate list, whether to use merge mode, merge candidate, merge candidate list, whether to use skip mode, interpolation filter type, interpolation filter tap, interpolation filter coefficient, motion vector size, accuracy of motion vector representation, Transform type, transform size, information about whether the primary (first) transform is used, information about whether the secondary transform is used, primary transform index, secondary transform index, information about whether the residual signal exists, coding block pattern, coding block Flag (CBF), quantization parameters, quantization matrix, whether to apply intra loop filter, intra loop filter coefficients, intra loop filter taps, intra loop filter shape/form, whether to apply deblocking Filter, deblocking filter coefficients, deblocking filter tap, deblocking filter strength, deblocking filter shape/form, whether to apply adaptive sample offset, adaptive sample offset value, adaptive sample Offset category, adaptive sample offset type, whether to apply adaptive in-loop filter, adaptive in-loop filter coefficients, adaptive in-loop filter taps, adaptive in-loop filter shape/form, binarization /Debinarization method, context model determination method, context model update method, whether to execute normal mode, whether to execute bypass mode, context binary bit, bypass binary bit, transformation coefficient, transformation coefficient level, transformation coefficient level scanning method, Image display/output sequence, slice identification information, slice type, slice partition information, tile identification information, tile type, tile partition information, picture type, bit depth, and luminance signal or chrominance signal information.

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

When the encoding device 100 performs encoding through inter prediction, the encoded current picture may be used as a reference picture for another image to be subsequently processed. Therefore, the encoding device 100 may reconstruct or decode the encoded current picture, or may store the reconstructed or decoded image as a reference picture.

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

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

Deblocking filters remove blocking artifacts produced in the boundaries between blocks. In order to determine whether to apply a deblocking filter, it may be determined based on pixels in several rows or columns included in the block whether to apply the deblocking filter to the current block. When a deblocking filter is applied to a block, another filter can be applied depending on the required deblocking filtering strength.

To compensate for coding errors, appropriate offset values are added to the pixel values using sample adaptive offset. Sample adaptive offset can correct the offset between the deblocked image and the original image in pixel units. A method of applying the offset considering edge information of each pixel may be used, or a method of partitioning the pixels of the image into a predetermined number of areas, determining the areas to which the offset will be applied, and applying the offset to the determined areas.

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

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

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

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

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

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

The decoding device 200 may obtain a reconstructed residual block by decoding the input bit stream, and may generate a prediction block. When the reconstruction residual block and the prediction block are obtained, the decoding device 200 may generate the reconstruction block that becomes the decoding target by adding the reconstruction residual block and the prediction block. The decoding target block may be called the current block.

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

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

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

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

When inter mode is used, motion compensation unit 250 may generate prediction blocks by performing motion compensation using motion vectors and reference pictures stored in reference picture buffer 270 .

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

FIG. 3 is a diagram schematically showing a partition structure of an image when encoding and decoding the image. Figure 3 schematically shows an example of partitioning a single unit into multiple lower level units.

In order to efficiently partition images, Coding Units (CUs) may be used when encoding and decoding. Coding units may be used as basic units when encoding/decoding images. Furthermore, the encoding unit may be used as a unit for distinguishing an intra mode and an inter mode when encoding/decoding an image. The coding unit may be a basic unit used for prediction, transformation, quantization, inverse transformation, inverse quantization, or encoding/decoding processing of transform coefficients.

Referring to FIG. 3 , an image 300 is sequentially partitioned in largest coding units (LCUs), and the LCU units are determined as a partition structure. Here, LCU may be used with the same meaning as Coding Tree Unit (CTU). Cell partitioning may mean partitioning the blocks associated with the cell. The block partition information may include unit depth information. Depth information may represent the number of times a unit is partitioned or the extent to which the unit is partitioned, or both. Individual units may be partitioned according to layers associated with depth information based on the tree structure. Each of the partitioned lower-level units may have depth information. The depth information may be information indicating the size of the CU and may be stored in each CU.

The partition structure may mean the distribution of coding units (CUs) in the LCU 310. Such a distribution may be determined based on whether a single CU is partitioned into multiple (positive integers equal to or greater than 2, including 2, 4, 8, 16, etc.) CUs. The horizontal size and vertical size of the CU generated by partitioning may be half of the horizontal size and vertical size, respectively, of the CU before partitioning, or may have sizes smaller than the horizontal size and vertical size, respectively, depending on the number of partitions. A CU can be recursively partitioned into multiple CUs. Partitioning of a CU may be performed recursively up to a predefined depth or a predefined size. For example, the depth of the LCU may be 0, and the depth of the minimum coding unit (SCU) may be a predefined maximum depth. Here, as described above, the LCU may be the coding unit with the largest coding unit size, and the SCU may be the coding unit with the smallest coding unit size. Beginning with partitioning at LCU 310, the CU depth increases by one as the horizontal size or vertical size, or both the horizontal size and the vertical size, of the CU decreases through the partitioning operation.

In addition, the information of whether the CU is partitioned may be expressed by using the partition information of the CU. Partition information may be 1-bit information. All CUs except SCU may include partition information. For example, when the value of the partition information is 1, the CU may not be partitioned, and when the value of the partition information is 2, the CU may be partitioned.

Referring to Figure 3, an LCU with depth 0 may be a 64×64 block. 0 can be the minimum depth. An SCU with depth 3 can be an 8×8 block. 3 can be the maximum depth. CUs of 32×32 blocks and 16×16 blocks may be represented as depth 1 and depth 2 respectively.

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

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

FIG. 4 is a diagram showing intra prediction processing.

Intra prediction mode can be non-angle mode or angle mode. The non-angular mode can be a DC mode or a planar mode, and the angular mode can be a prediction mode with a specific direction or angle. The intra prediction mode may be expressed by at least one of a mode number, a mode value, a mode number, and a mode angle. The number of intra prediction modes may be M including 1, as well as non-directional modes and directional modes.

The number of intra prediction modes may be fixed to N regardless of block size. Alternatively, the number of intra prediction modes may vary depending on block size or color component type, or both block size and color component type. For example, as the block size becomes larger, the number of intra prediction modes may increase. Alternatively, the number of intra prediction modes for luma component blocks may be greater than the number of intra prediction modes for chroma component blocks.

For intra prediction of a current block, a step of determining whether samples included in reconstructed neighboring blocks can be used as reference samples for the current block may be performed. Obtained by copying or performing interpolation or both copying and performing interpolation of at least one sample value among the samples included in the reconstructed adjacent block when there are samples that cannot be used as reference samples for the current block. Values can be used to replace unavailable sample values for samples, whereby the replaced sample values are used as reference samples for the current block.

When intra-predicting, a filter may be applied to at least one of the reference sample and the prediction sample based on the intra-prediction mode and the current block size.

In the case of planar mode, when generating the prediction block of the current block, according to the position of the prediction target sample within the prediction block, the upper left reference sample of the current sample and the upper right and lower left sides of the current sample can be used A weighted sum of reference samples is used to generate sample values for predicting target samples. Furthermore, in the case of DC mode, when generating a prediction block of the current block, the average value of the upper and left reference samples of the current block may be used. Furthermore, in the case of angle mode, the prediction block may be generated by using upper, left, upper right and/or lower left reference samples of the current block. To produce predicted sample values, interpolation in real units can be performed.

The intra prediction mode of the current block may be entropy encoded/entropy decoded by predicting the intra prediction mode of a block adjacent to the current block. When the intra prediction modes of the current block and the neighboring block are the same, information that the intra prediction modes of the current block and the neighboring block are the same may be signaled by using predetermined flag information. In addition, indicator information of an intra prediction mode that is the same as the intra prediction mode of the current block among the intra prediction modes of a plurality of neighboring blocks may be signaled. When the intra prediction modes of the current block and the neighboring block are different, the intra prediction mode information of the current block may be entropy encoded/entropy decoded by performing entropy encoding/entropy decoding based on the intra prediction mode of the neighboring block.

FIG. 5 is a diagram illustrating a method of performing intra prediction on a current block according to an embodiment of the present invention.

As shown in FIG. 5 , intra prediction may include an intra prediction mode derivation step S510 , a reference sample configuration step S520 , and/or an intra prediction execution step S530 .

In the intra prediction mode derivation step S510, at least one of the following methods may be used to derive the intra prediction mode of the current block: a method using the intra prediction mode of a neighboring block, decoding the intra prediction mode of the current block (eg, entropy decoding), a method using coding parameters of neighboring blocks, a method using intra prediction mode of color components, and/or a method using intra prediction mode using a transform model.

In the method of using the intra prediction mode of the neighboring block, the intra prediction mode may be derived by using the intra prediction mode of the neighboring block, a combination of one or more intra prediction modes of the neighboring block, and/or by using the MPM. At least one of them is used to derive the intra prediction mode of the current block.

In the method of using the intra prediction mode using a transformation model, at least one of rigid body transformation, similarity transformation, affine transformation, and homography transformation may be used to determine the intra prediction mode of the sub-block in the current block.

Alternatively, in the method of using the intra prediction mode using the transform model, at least one of the isospace model and the bilinear filter mode may be used to determine the intra prediction mode of the sub-block in the current block.

In the reference sample configuration step S520, a reference sample selection step and/or a reference sample filtering step may be performed, so that the reference sample may be configured.

In the reference sample point selection step, in the step of configuring the reference sample points of the sub-blocks in the current block, the reference sample points may be selected differently according to the sub-block scanning method (raster scan, zigzag scan, vertical scan, etc.).

In the intra prediction execution step S530, at least one method of non-directional prediction, directional prediction, prediction based on position information, and/or prediction between color components may be used to perform intra prediction of the current block. In intra prediction execution step S530, filtering for prediction samples may be performed.

In the following, the intra prediction mode derivation step S510 will be described in detail.

The neighboring blocks of the current block may be at least one of lower left, left, upper left and upper right neighboring blocks of the current block. Among the neighboring blocks, neighboring blocks in which only intra prediction mode can be used may be used.

Among the neighboring blocks of the current block, the intra prediction mode of the neighboring block at a specific position may be derived as the intra prediction mode of the current block.

Alternatively, two or more neighboring blocks are selected, and the statistical value of the intra prediction mode of the selected neighboring blocks can be derived as the intra prediction mode of the current block. The intra prediction mode may be indicated by at least one of a mode number, a mode value, and a mode angle. In the specification, the statistical value may be at least one of a minimum value, a maximum value, an average value, a weighted average value, a mode, and a median value.

Neighboring blocks at specific locations and/or selected neighboring blocks may be blocks at predefined fixed locations. Alternatively, the blocks may be specified based on information signaled through the bitstream.

When at least two intra prediction modes are used, it may be considered whether the intra prediction mode is directional or non-directional. For example, among two or more intra prediction modes, a directional intra prediction mode may be used to derive the intra prediction mode of the current block. Alternatively, a non-directional intra prediction mode may be used to derive the intra prediction mode of the current block.

When a weighted average is used as a statistical value, a relatively high weight can be assigned to a specific intra prediction mode. The specific intra prediction mode may be, for example, at least one of a vertical mode, a horizontal mode, a diagonal mode, and a non-directional mode. Alternatively, information about a specific intra prediction mode may be signaled through the bitstream. The individual weights of a particular intra prediction mode may be the same as or different from each other. Alternatively, weights may be determined based on the size of neighboring blocks. For example, a relatively high weight may be assigned to an intra prediction mode of a relatively large neighboring block.

The intra prediction mode of the current block can be derived using MPM (Most Likely Mode).

When using MPM, the MPM list can be configured with N intra prediction modes derived using the intra prediction modes of neighboring blocks. N is a positive integer and can have different values depending on the size and/or shape of the current block. Alternatively, information about N may be signaled via a bitstream.

The intra prediction modes that may be included in the MPM list may be the intra prediction modes of lower left, left, upper left, upper, and/or upper right neighboring blocks of the current block. Additionally, non-directional modes may be included in the MPM list. Intra prediction modes may be included in the MPM list in a predetermined order. The predetermined order may be, for example, the order of the mode of the lower left block, the mode of the upper block, the plane mode, the DC mode, the mode of the lower left block, the mode of the upper right block, and the mode of the upper left block. Alternatively, the predetermined order may be the order of the mode of the left block, the mode of the upper block, the plane mode, the DC mode, the mode of the lower left block, the mode of the upper right block, and the mode of the upper left block.

The MPM list can be configured not to include replication mode. When the number of intra prediction modes included in the MPM list is less than N, additional intra prediction modes may be included in the MPM list. The additional intra prediction mode may be a mode corresponding to +k, -k of the directional intra prediction modes included in the MPM list. An integer equal to or greater than one can be specified by k. Alternatively, at least one of horizontal mode, vertical mode, and diagonal mode (45-degree angle mode, 135-degree angle mode, and 225-degree angle mode) may be included in the MPM list. Alternatively, statistical values of at least one intra prediction mode of neighboring blocks may be used to derive the intra prediction mode to be included in the MPM list.

Several MPM lists can exist and can be configured in different ways. Intra prediction modes included in each MPM list may not be repeated.

Information (eg, flag information) indicating whether the intra prediction mode of the current block is included in the MPM list may be signaled through the bitstream. When there are N MPM lists, there can be N pieces of flag information. Determining whether the intra prediction mode of the current block exists in the MPM list may be performed in order for the N MPM lists. Alternatively, information indicating an MPM list including the intra prediction mode of the current block among the N MPM lists may be signaled.

When the intra prediction mode of the current block is included in the MPM list, index information for specifying which mode among the modes included in the MPM list may be signaled through a bit stream. Alternatively, the mode at a specific position (eg, first) of the MPM list may be derived as the intra prediction mode of the current block.

In the step of configuring the MPM list, one MPM list may be configured for a predetermined size block. When a predetermined size block is partitioned into several sub-blocks, each of the several sub-blocks may use a configured MPM list.

Alternatively, the intra prediction mode of the current block may be derived using at least one of the intra prediction mode of the neighboring block and the intra prediction mode of the current block derived using the MPM.

For example, when the intra prediction mode of the current block derived using MPM is Pred_mpm, Pred_mpm is changed to a predetermined mode by using at least one intra prediction mode of a neighboring block so that the intra prediction mode of the current block can be derived. For example, Pred_mpm may be increased or decreased by N by comparing Pred_mpm with the size of the intra prediction mode of a neighboring block. Here, N may be a predetermined integer, such as +1, +2, +3, 0, -1, -2, -3, etc.

Alternatively, when one of Pred_mpm and the mode of the neighboring block is a non-directional mode and the other is a directional mode, the non-directional mode may be derived as the intra prediction mode of the current block, or the directional mode may be derived is the intra prediction mode of the current block.

The intra prediction mode of the current block may be derived using the intra prediction mode of another color component. For example, when the current block is a chroma block, the intra prediction mode of at least one related luma block corresponding to the chroma target block may be used to derive the intra prediction mode of the chroma block. Here, the relevant luma block may be determined based on at least one of a position, a size, a shape, or an encoding parameter of the chroma block. Alternatively, the relevant luma block may be determined based on at least one of a size, a shape, or an encoding parameter of the luma block.

The relevant luma block may be determined using a luma block including a sample point corresponding to a center position of the chroma block, or using at least two luma blocks each including a sample point corresponding to at least two positions of the chroma block. The at least two positions may include an upper left sample position and a center sample position.

When there are several related luma blocks, the statistical value of the intra prediction mode of at least two related luma blocks may be derived as the intra prediction mode of the chroma block. Alternatively, the intra prediction mode of the relatively large correlated luma block can be derived as the intra prediction mode of the chroma block. Alternatively, when the size of the luma block corresponding to the predetermined position of the chroma block is equal to or larger than the size of the chroma block, the intra prediction mode of the relevant luma block may be used to derive the intra prediction mode of the chroma block.

For example, when the current block is partitioned into sub-blocks, at least one method of deriving the intra-prediction mode of the current block may be used to derive the intra-prediction mode of each of the partitioned sub-blocks.

In the step of deriving the intra prediction mode, the current block may be divided into a plurality of sub-blocks that are smaller than the current block, and then the intra prediction mode of each sub-block may be derived. Here, the intra prediction mode may represent an intra prediction direction. The intra prediction mode may be included in a set of intra prediction modes predefined in the encoder and decoder.

For example, the intra prediction of the current block may be generated using at least one of the intra prediction modes of the block that has been encoded/decoded by using intra prediction in the reconstructed block adjacent to the current block and the intra prediction mode of the current block. Direction field (IPDF). Predetermined transformation models can be used to generate IPDFs. After the IPDF is generated, the IPDF can be used to determine the intra prediction mode for each sub-block of the current block.

Furthermore, similar to the above example, if the current block is divided from a larger or lower depth block than the current block, the current block may be a sub-block of the larger or lower depth block. In this case, the current block may be derived using at least one of the intra prediction modes of blocks that have been encoded/decoded by intra prediction in reconstructed blocks adjacent to larger or lower depth blocks than the current block. Intra prediction mode. The intra prediction mode of the current block can be derived by generating an IPDF.

As the predetermined transformation model, at least one of rigid body transformation, similarity transformation, affine transformation, homography transformation, 3D transformation and other transformations may be used. The homography transformation can be a perspective transformation.

Since each sub-block divided from the current block can be derived using at least one of the intra prediction modes of the block that has been encoded/decoded by using intra prediction in the reconstructed block adjacent to the current block and the intra prediction mode of the current block. The intra prediction mode of the block can therefore reduce the number of bits required for entropy encoding/entropy decoding of the intra prediction mode of each sub-block.

The size (granularity) of the sub-block may be less than or equal to the size of the current block. For example, if the size of the current block is M×N (M and N are positive integers), the size of the sub-block may be M/K×N/L. K and M can be positive integers, and L can be a positive factor of N. Additionally, M/K or N/L may be a positive integer.

Furthermore, P sub-blocks may exist in the current block. P can be 0 or a positive integer. For example, 1, 2, 4 or 16 sub-blocks may be present in the current block.

Furthermore, when the current block is divided into sub-blocks, the information indicating whether the current block has been divided into sub-blocks may not be entropy encoded/decoded separately. Whether the current block has been divided into sub-blocks may be determined based on information indicating whether the intra prediction mode of the current block is derived based on sub-blocks.

Furthermore, since the intra prediction of the sub-block is derived using at least one of the intra prediction modes of the block that has been encoded/decoded by using intra prediction in the reconstructed block adjacent to the current block and the intra prediction mode of the current block mode, so the intra prediction mode of the sub-block may not be entropy encoded/decoded. However, the intra prediction mode of the current block may be entropy encoded/decoded. In particular, if the current block is constructed from one sub-block, the intra prediction mode of the current block may not be entropy encoded/decoded, and the intra prediction mode in the reconstructed block adjacent to the current block may be used to be encoded/decoded by intra prediction The intra prediction mode of the current block is derived from at least one of the intra prediction modes of the block.

A block among the reconstructed blocks adjacent to the current block that has been encoded/decoded by using intra prediction (for IPDF generation) may be called a seed block. The location of the seed block may be called a seed point. The intra prediction mode that the seed block including the seed point has may be called a seed point intra prediction mode (SPIPM).

FIG. 6 is a diagram illustrating an embodiment of deriving an intra prediction mode of a current block using SPIPM.

In the example shown in FIG. 6 , the size of the current block may be 16×16, and the size of each sub-block may be (16/4)×(16/4). Here, the seed block may be at least one of a plurality of neighboring blocks that have been encoded/decoded through intra prediction. The seed block or seed point can be a fixed position relative to the current block. Alternatively, at least one of upper, left, upper left, lower left, and upper right blocks or locations may be determined as a seed block or seed point.

For example, the intra prediction mode of at least one of the upper neighboring blocks c, d, e, f, and g of the current block may be used as the SPIPM. Alternatively, the intra prediction mode of the upper right block h adjacent to the current block may be used as SPIPM. Alternatively, the intra prediction mode of at least one of the upper left blocks a and b adjacent to the current block may be used as the SPIPM. Alternatively, the intra prediction mode of at least one of the left blocks i, j, k, and l adjacent to the current block may be used as SPIPM. Alternatively, the intra prediction mode of the lower left block m adjacent to the current block may be used as SPIPM. For example, the intra prediction mode of the current block may also be used as SPIPM.

IPDF can be generated using SPIPM of one or more seed points.

For example, if the coordinates of the plurality of seed points used to determine parameters of the predetermined transformation model are (x_sp, y_sp) (sp=1, 2, 3, ...), and the SPIPM of the seed block including the seed points is mode_sp (sp= 1, 2, 3,...), then the coordinates (x_sp', y_sp') of the seed point after transformation can be determined as (x_sp', y_sp')=(x_sp+dx, y_sp+dy). Here, dx can represent the displacement in the x-axis direction, and dy can represent the displacement in the y-axis direction. Furthermore, it can be determined that dx=D_sub*cosΘ and dy=D_sub*sinΘ.

Here, Θ can be determined based on SPIPM. For example, if the intra prediction mode is a directional mode as shown in Figure 6, each SPIPM may have a unique direction, and the positive angle with respect to the x-axis may be determined as Θ.

For example, for vertical intra prediction mode, Θ=270°. For example, for horizontal intra prediction mode, Θ=0°. For example, for the lower left diagonal intra prediction mode, Θ=225°. For example, for the upper right diagonal intra prediction mode, Θ=45°. For example, for the lower right diagonal intra prediction mode, Θ=135°.

Here, for an intra prediction mode without directionality, such as DC mode or planar mode, Θ may be determined as a specific value. Specific values may be, for example, 0, 90, 180 or 270 degrees.

SPIPM can represent the directionality relative to the seed point, and D_sub can represent the size of the vector with directionality. The size of D_sub may be determined according to the size and/or shape of the seed block to which the seed point belongs. Furthermore, D_sub may have a fixed value P for each intra prediction mode. Here, P can be 0 or an integer. For example, if the size of the current block is M×N (M and N are positive integers) and D_cur=S (S is a positive integer), then D_sub (sub=1, 2, 3, ...) is determined as D_sub=S*(K×L)/(M×N). For example, if the size of the current block is 16×16 in FIG. 6 , then D_cur=S and D_sub of the seed block can be determined according to at least one of the following methods.

For example, for seed block d or e, it can be determined that D_sub=S*(4×8)/(16×16)=S/8. For example, for seed block g or j, it can be determined that D_sub=S*(8×8)/(16×16)=S/4. For example, for seed block k or l, it can be determined that D_sub=S*(8×4)/(16×16)=S/8. For example, for seed block m or h, it can be determined that D_sub=S*(16×16)/(16×16)=S. For example, D_sub may be determined as S for each seed block.

Candidates can be configured by constructing a SPIPM list for generation of the IPDF of the current block. The SPIPM list may be generated using the intra prediction mode of at least one of the neighboring blocks of the current block. For example, the SPIPM may be a set of one or more of the upper left (SPIPM_TL), upper right (SPIPM_TR), lower left (SPIPM_BL), and lower right (SPIPM_BR) SPIPM of the current block. For a W×H current block, SPIPM_TL may have at least one of intra prediction modes for upper, upper left, and left neighboring blocks of the position (0,0) of the current block as candidates. SPIPM_TR may have at least one of intra prediction modes for upper and upper right neighboring blocks of the position (W-1,0) of the current block as candidates. SPIPM_BL may have at least one of intra prediction modes for left and lower left neighboring blocks of the position (0, H-1) of the current block as candidates. SPIPM_BR may represent the intra prediction mode of neighboring blocks of the current block. Or SPIPM_BR can be used to indicate the intra prediction mode of the current block.

In the example shown in FIG. 6 , SPIPM_TL may have at least one of the intra prediction modes of neighboring blocks d, b, and j. In addition, SPIPM_TR may have at least one of intra prediction modes of adjacent blocks g and h. Furthermore, SPIPM_BL may have at least one of intra prediction modes of neighboring blocks i and m. Furthermore, SPIPM_BR may have at least one of the intra prediction modes of the current block.

Additionally, seed blocks or seed points can be searched in a predetermined order. For example, the SPIPM list may be constructed from the intra prediction modes of the corresponding seed blocks or seed points by searching the seed blocks or seed points in the order of left side, upper side, lower left side, upper right side, and upper side.

In order to construct the SPIPM list, a process of excluding intra prediction modes having different directions from other modes based on similarity between intra prediction modes may be performed for at least one of the candidates for each of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR. . Here, intra prediction mode difference (IPMD) may be used as a criterion for measuring similarity. Non-directional modes (eg, DC_MODE and PLANAR_MODE) can be excluded when constructing the SPIPM list.

For example, if in the comparison between each of the three candidate modes of SPIPM_TL_mode and the candidate mode of SPIPM_neighbor (neighbor=TR or BL or BR), IPMD=abs(SPIPM_TL_mode-SPIPM_neighbor)>Th1 (Th1 is a positive integer) , the corresponding pattern can be excluded from the candidate set of SPIPM_TL.

For example, if in a comparison between each of the two candidate modes of SPIPM_TR_SPIPM_TR_mode and the candidate mode of SPIPM_neighbor (neighbor=TL or BL or BR), IPMD=abs(SPIPM_TR_mode-SPIPM_neighbor)>Th2 (Th2 is a positive integer) , the corresponding pattern can be excluded from the candidate set of SPIPM_TR.

For example, if in the comparison between each of the two candidate modes of SPIPM_BL_mode SPIPM_BL_mode and the candidate mode of SPIPM_neighbor (neighbor=TL or TR or BR), IPMD=abs(SPIPM_BL_mode-SPIPM_neighbor)>Th3 (Th3 is a positive integer) , the corresponding pattern can be excluded from the candidate set of SPIPM_BL.

For example, if in the comparison between each of the candidate modes of SPIPM_BR_mode and the candidate mode of SPIPM_neighbor (neighbor=TL or TR or BL), IPMD=abs(SPIPM_BR_mode-SPIPM_neighbor)>Th4 (Th4 is a positive integer), then The corresponding pattern can be excluded from the candidate set of SPIPM_BR.

For example, if at least one of the candidates for each of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR is a non-directional intra prediction mode, such as DC mode or planar mode, the corresponding candidate may be excluded from the candidate set.

After candidates with small similarities among the candidates used to construct the SPIPM list are eliminated, the number of SPIPM required for IPDF generation can be determined based on the specific 2D transformation model used. For example, the 2D transformation model may include rigid body transformation, similarity transformation, affine transformation, and homography transformation. Furthermore, the number of SPIPM can be determined as a variable value of 1, 2, 3, 4, or N (N is a positive integer) according to the 2D transformation model.

For example, if the transformation model used for IPDF generation is a rigid body transformation, at least two SPIPM may be required.

Rigid body transformations can have 3 degrees of freedom (3-DoF), as described in [Equation 1]. Here, (x, y) may be the coordinates of the seed point before transformation, and (x’, y’) may be the coordinates of the seed point after transformation. Θ, tx and ty are the model parameters to be determined, which can be the rotation angle, x-axis displacement and y-axis displacement respectively.

[Equation 1]

The (x, y)-(x', y') pair can be obtained using Θ determined from a SPIPM, and can be obtained by substituting the (x, y)-(x', y') pair into [Eq. 1] Determine the two equations related to Θ, tx, and ty. Furthermore, four equations related to Θ, tx, and ty can be determined from the two SPIPMs, and three of the four equations can be used to determine the rigid body transformation model.

The two SPIPMs may be determined by selecting at least two of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR. The selected SPIPM can be added to the SPIPM list.

FIG. 7 is a diagram illustrating an embodiment of constructing a SPIPM list including two SPIPMs.

As shown in Figure 7, the SPIPM list may be populated in ascending order of the IPMD sum of the two SPIPM candidate modes.

For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_TR may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_BL may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_BR may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BL may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BR may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_BL and one of the candidate modes of SPIPM_BR may be used as two SPIPMs.

If both SPIPMs are not populated, the available SPIPMs can be used to populate the SPIPM list. For example, SPIPM±delta can be used to populate the SPIPM list. Here, delta can be any positive integer, for example, 1, 2, 3,….

Once the two SPIPMs (SPIPM1, SPIPM2) are determined, four equations related to Θ, tx and ty can be generated by [Equation 1]. Three of the four equations can be used to determine the parameters of the rigid body transformation model. The determined model can be used for IPDF generation.

For example, the rigid body transformation may be determined using at least one of the two equations calculated by SPIPM1 and the two equations calculated by SPIPM2. For example, the rigid body transformation may be determined using at least one of the two equations calculated by SPIPM1 and the two equations calculated by SPIPM2.

For example, if similarity transformation is used as the transformation model for IPDF generation, at least two SPIPM may be required.

The similarity transformation can have 4-DoF as described in [Equation 2]. Here, (x, y) may be the coordinates of the seed point before transformation, and (x’, y’) may be the coordinates of the seed point after transformation. a, b, c and d may be model parameters to be determined.

[Equation 2]

The (x, y)-(x', y') pair can be obtained using Θ determined from a SPIPM, and can be obtained by substituting the (x, y)-(x', y') pair into [Eq. 2] Identify the two equations related to a, b, c, and d. Furthermore, four equations related to a, b, c, and d can be determined from the two SPIPMs, and the similarity transformation model can be obtained using the four equations.

The two SPIPMs may be determined by selecting at least two of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR. The selected SPIPM can be added to the SPIPM list. Here, as shown in FIG. 7, the SPIPM list may be populated in ascending order of the sum of the IPMD values of the two SPIPM candidate patterns.

For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_TR may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_BL may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TL and one of the candidate modes of SPIPM_BR may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BL may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_TR and one of the candidate modes of SPIPM_BR may be used as two SPIPMs. For example, one of the candidate modes of SPIPM_BL and one of the candidate modes of SPIPM_BR may be used as two SPIPMs.

If both SPIPMs are not populated, the available SPIPMs can be used to populate the SPIPM list. For example, SPIPM±delta can be used to populate the SPIPM list. Here, delta can be any positive integer, for example, 1, 2, 3,….

Once the two SPIPMs (SPIPM1, SPIPM2) are determined, four equations related to a, b, c and d can be generated by [Equation 2] to determine the parameters of the similarity transformation model. The determined model can be used for IPDF generation.

For example, if affine transformation is used as the transformation model for IPDF generation, at least three SPIPM may be required.

Affine transformations can have 6-DoF as described in [Equation 3]. Here, (x, y) may be the coordinates of the seed point before transformation, and (x’, y’) may be the coordinates of the seed point after transformation. a, b, c, d, e and f may be model parameters to be determined.

[Equation 3]

The (x, y)-(x', y') pair can be obtained using Θ determined from a SPIPM, and can be obtained by substituting the (x, y)-(x', y') pair into [Eq. 3] Identify the two equations related to a, b, c, d, e, and f. In addition, six equations related to a, b, c, d, e, and f can be determined from the three SPIPMs, and the affine transformation model can be obtained using the six equations.

Three SPIPMs may be determined by selecting at least three of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR. The selected SPIPM can be added to the SPIPM list.

FIG. 8 is an exemplary diagram illustrating an embodiment of constructing a SPIPM list including three SPIPMs.

As shown in Figure 8, the SPIPM list can be populated using SPIPM in ascending order of the sum of the IPMD values of the three SPIPM candidate patterns.

For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BL may be used as three SPIPMs. For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as three SPIPMs. For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR may be used as three SPIPMs. For example, one of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR may be used as three SPIPMs.

If three SPIPMs are not populated, the available SPIPMs can be used to populate the SPIPM list. For example, SPIPM±delta can be used to populate the SPIPM list. Here, delta can be any positive integer, for example, 1, 2, 3,….

Once the three SPIPMs (SPIPM1, SPIPM2, SPIPM3) are determined, the parameters of the affine transformation model can be determined by generating six equations related to a, b, c, d, e and f through [Equation 3]. The determined model can be used for IPDF generation.

For example, if a homography transformation (or perspective transformation) is used as the transformation model for IPDF generation, at least four SPIPM may be required.

Affine transformations can have 8-DoF as described in [Equation 4]. Here, (x, y) may be the coordinates of the seed point before transformation, and (x’, y’) may be the coordinates of the seed point after transformation. h1, h2, h3, h4, h5, h6, h7 and h8 may be model parameters to be determined.

[Equation 4]

The (x, y)-(x', y') pair can be obtained using Θ determined from a SPIPM, and can be obtained by substituting the (x, y)-(x', y') pair into [Eq. 4] Identify the two equations related to h1, h2, h3, h4, h5, h6, h7, and h8. In addition, eight equations related to h1, h2, h3, h4, h5, h6, h7, and h8 can be determined from the four SPIPMs, and the homography transformation model can be obtained using the eight equations.

The four SPIPMs may be determined by selecting at least four of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR. The selected SPIPM can be added to the SPIPM list.

FIG. 9 is an exemplary diagram illustrating an embodiment of constructing a SPIPM list including four SPIPMs.

As shown in Figure 9, the SPIPM list can be populated sequentially using SPIPM in ascending order of the sum of the IPMD values of the four SPIPM candidate patterns.

For example, two of the candidate patterns of SPIPM_TL and two of the candidate patterns of SPIPM_TR may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_TL and two of the candidate patterns of SPIPM_BL may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_TL and two of the candidate patterns of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_BL and two of the candidate patterns of SPIPM_TR may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_BL and two of the candidate patterns of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_TL, one of the candidate patterns of SPIPM_TR, and one of the candidate patterns of SPIPM_BL may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_TL, one of the candidate patterns of SPIPM_BL, and one of the candidate patterns of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_BL, one of the candidate patterns of SPIPM_TL, and one of the candidate patterns of SPIPM_TR may be used as four SPIPMs. For example, two of the candidate patterns of SPIPM_BL, one of the candidate patterns of SPIPM_TL, and one of the candidate patterns of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_BL, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_TR may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TL, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs. For example, two of the candidate modes of SPIPM_BR, one of the candidate modes of SPIPM_TR, and one of the candidate modes of SPIPM_BL may be used as four SPIPMs. For example, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR may be used as four SPIPMs.

If the four SPIPMs are not populated, the available SPIPMs can be used to populate the SPIPM list. For example, SPIPM±delta can be used to populate the SPIPM list. Here, delta can be any positive integer, for example, 1, 2, 3,….

Once the four SPIPMs (SPIPM1, SPIPM2, SPIPM3, SPIPM4) are determined, the homography can be determined by [Equation 4] generating eight equations related to h1, h2, h3, h4, h5, h6, h7 and h8 Parameters of the sex transformation model. The determined model can be used for IPDF generation.

After generating an IPDF using a predetermined transform model, the generated IPDF may be used to assign an intra prediction mode to a K×L sub-block within a W×H current block. Here, the size K×L of each sub-block (K is a positive integer equal to or smaller than M, and L is a positive integer equal to or smaller than H) may be a fixed size equal to or smaller than the size of the current block. Alternatively, the sub-block size may be determined adaptively using the size of the current block and/or IPMD. Or the sub-block can be equal to the size of the current block.

FIG. 10 is an exemplary diagram showing the sub-block size in the case where the size of the current block is 16×16.

As shown in (a) of Figure 10, the size of the sub-block can be fixed at 8×8. Alternatively, as shown in (b) of FIG. 10 , the size of the sub-block may be fixed to 4×4. Alternatively, as shown in (c) of FIG. 10 , the size of the sub-block may be fixed to 2×2. Alternatively, as shown in (d) of FIG. 10 , the size of the sub-block may be fixed to 1×1. The fixed size 1×1 can be the size of the sample unit.

For example, the size of the sub-block may be determined based on the size of the current block. For example, the size of the sub-block may be determined based on at least one of the IPMDs of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR of the current block. For example, the size of the sub-block may be determined based on at least one of the IPMDs of SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR of the current block and the size of the current block.

Information on the size (granularity) of sub-blocks may be entropy encoded/decoded in the bitstream. Here, the information may be entropy encoded/decoded in at least one of VPS, SPS, PPS, APS, slice header, parallel block header, CTU, CU, PU, TU, block and sub-block.

Information about the sub-block size can be adaptively derived based on the size of the current block and/or the IPMD without sending this information.

Furthermore, the sub-block size may be determined based on at least one of a coding parameter of the current block and a coding parameter of a neighboring block of the current block.

The determined IPDF may be used to assign the intra prediction mode of the sub-block. The intra prediction mode at a specific position in each sub-block can be implemented as a vector by substituting the coordinates of the specific position into the determined IPDF model. The specific location may be determined as the location of the pixel in the sub-block or adjacent to a boundary of the sub-block. For example, at least one of the upper left side, upper right side, lower left side, lower right side, and middle position of the sub-block may be determined as a specific position. If the coordinates of a specific position in the sub-block are (x, y) and the transformation coefficient of the position calculated by IPDF is (x', y'), then θ _SB =atan[(y'-y)/(x '-x)] to determine the direction of the vector θ _SB .

FIG. 11 is a diagram illustrating an embodiment of allocating an intra prediction mode using a determined IPDF.

As shown in FIG. 11 , θ _SB can be mapped to the intra prediction mode oriented in the most similar direction among the directional modes. Theta _SB to intra prediction mode mapping may be performed using a look-up table (LUT).

Furthermore, when the IPDF is used to allocate the intra prediction mode of the sub-block, the IPDF may be allocated as the intra prediction mode of the sub-block based on the nearest neighbor method. Furthermore, when an intra prediction mode is assigned to a sub-block using IPDF, the intra prediction mode may be assigned to the sub-block by quantizing the IPDF into an integer. Furthermore, when an intra prediction mode is assigned to a sub-block using IPDF, the intra prediction mode may be assigned to the sub-block by rounding the IPDF to the nearest integer.

For sub-block-based intra prediction based on the transform model, information to be additionally entropy encoded/entropy decoded in the bitstream may include at least one of the following.

Information indicating whether transform model-based per-subblock intra prediction has been performed for the current block: TBIP_flag

TBIP_flag may be a value indicating whether to derive each sub-block using at least one of an intra prediction mode of a block that has been encoded/decoded by using intra prediction in a reconstructed block adjacent to the current block and an intra prediction mode of the current block. Intra prediction mode information.

Index indicating the SPIPM collection used: SPIPM_idx

Now, another embodiment of deriving a sub-block based intra prediction mode using a transform model will be given. For example, in the case where there is a block that has been encoded/decoded by sub-block-based intra prediction based on the transform model in the neighboring reconstructed block, the intra prediction mode can be derived for each sub-block using the IPDF model of the neighboring block instead Directly generate the IPDF of the current block.

In order to determine whether there are any blocks that have been encoded/decoded by transform model-based per-sub-block intra prediction among the neighboring reconstructed blocks of the current block, a predefined scan order may be used. The scan order can be at least one of the following orders.

FIG. 12 is an exemplary diagram showing reconstructed blocks adjacent to the current block.

For example, in FIG. 12, scanning may be performed in the order A→B→C→D→E. Alternatively, the scan can be performed in the order A→B→D→C→E. Alternatively, the scan can be performed in the order B→A→D→C→E. Alternatively, the scan can be performed in the order E→A→B→C→D. Alternatively, the scans can be performed in any other order.

Alternatively, part of blocks A, B, C, D and C can be excluded from scanning. Alternatively, blocks other than blocks A, B, C, D, and C can be scanned. The neighboring reconstruction blocks to be scanned may be determined based on at least one of size, shape, and coding parameters as described herein of at least one of the neighboring reconstruction blocks and the current block.

FIG. 13 is a diagram illustrating an embodiment of deriving an intra prediction mode using neighboring reconstructed blocks.

In the example shown in FIG. 13 , in the case where block A, which is a neighboring block of the current block, is encoded/decoded by sub-block unit intra prediction using the transform model, SPIPM_A_TL, SPIPM_A_TR of block A may be used , SPIPM_A_BL and at least one of SPIPM_A_BR to generate the IPDF of block A.

The IPDF of block A may be used to derive at least one of SPIPM_Cur_TL, SPIPM_Cur_TR, SPIPM_Cur_BL, and SPIPM_Cur_BR of the current block, and the derived at least one of SPIPM_Cur_TL, SPIPM_Cur_TR, SPIPM_Cur_BL, and SPIPM_Cur_BR may be used to generate the IPDF of the current block, thereby Perform sub-block-wise intra prediction.

If at least one of the neighboring reconstruction blocks of the current block is a block that was encoded/decoded using IPDF, the IPDF of the corresponding neighboring reconstruction block may be used to derive the IPDF of the current block. In addition, entropy encoding/entropy decoding can be performed on the information of TBIP_flag.

Another embodiment of deriving a sub-block based intra prediction mode using an iso-spatial model will be described.

FIG. 14 is a diagram illustrating an embodiment of deriving a sub-block based intra prediction mode.

Where equal spatial models are used, at least two SPIPM may be required. For example, as shown in (a) of FIG. 14 , four candidate modes may be selected in total, namely, one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_BL, and the candidate mode of SPIPM_BR. one of the. As shown in Figure 9, the selected four SPIPM candidate modes may be populated into the SPIPM list in ascending order of the sum of IPMD values.

The intra prediction mode of the outermost sub-block of the current block may be first determined using SPIPM_TL, SPIPM_TR, SPIPM_BL and/or SPIPM_BR. Determining the intra prediction modes equally spatially may mean dividing the values of the intra prediction modes at equal intervals using at least two intra prediction modes and assigning the divided intra prediction mode values to the subblocks.

For example, in the example shown in (a) of FIG. 14 , if SPIPM_TL is 24 and SPIPM_TR is 21, the intra prediction modes of sub-blocks A, B, C, and D may be spatially determined using the values of SPIPM_TL and SPIPM_TR, etc. . For example, as shown in (b) of FIG. 14 , A=24, B=23, C=22, and D=21 can be determined. For example, in the example shown in (a) of FIG. 14 , if SPIPM_TL is 25 and SPIPM_BL is 38, the intra prediction modes of sub-blocks A, E, I, and M may be spatially determined using the values of SPIPM_TL and SPIPM_BL, etc. . For example, as shown in (b) of FIG. 14 , A=24, E=29, I=34, and M=38 can be determined. For example, in the example shown in (a) of FIG. 14 , if SPIPM_BL is 38 and SPIPM_BR is 35, the intra prediction modes of sub-blocks M, N, O, and P may be spatially determined using the values of SPIPM_BL and SPIPM_BR, etc. . For example, as shown in (b) of FIG. 14 , it can be determined that M=38, N=37, O=36, and P=35. For example, in the example shown in (a) of FIG. 14 , if SPIPM_TR is 21 and SPIPM_BR is 35, the intra prediction modes of sub-blocks D, H, I, and P may be spatially determined using the values of SPIPM_TR and SPIPM_BR, etc. . For example, as shown in (b) of FIG. 14 , D=21, H=26, I=31, and P=35 can be determined.

After all the intra prediction modes of the outermost sub-block of the current block are determined, the intra prediction mode of the next outermost sub-block may be determined. In the example shown in FIG. 14, the second outer sub-blocks may be sub-blocks F, G, J, and K. Here, SPIPM_TL may be reset to the pattern of the upper left position of the upper left subblock (subblock F in FIG. 14(a) ) among the second outer subblocks (subblock A in FIG. 14(a) ). mode) value. In addition, SPIPM_TR may be reset to the pattern of the upper right position of the upper right subblock (subblock G in FIG. 14(a) ) among the second outer subblocks (subblock D in FIG. 14(a) ). mode) value. In addition, SPIPM_BL may be reset to the pattern of the lower left position of the lower left subblock (subblock J in FIG. 14(a) ) among the second outer subblocks (subblock M in FIG. 14(a) ). mode) value. In addition, SPIPM_BR may be reset to the mode (subblock K in FIG. 14(a) ) of the lower right side position of the lower right subblock (subblock K in FIG. 14(a) ) among the second outer subblocks. mode of P). This operation can be repeated recursively until the modes of all sub-blocks of the current block are determined.

For example, in the example shown in (b) of FIG. 14 , if SPIPM_TL is 24 and SPIPM_TR is 21, the intra prediction modes of sub-blocks F and G may be spatially determined using the values of SPIPM_TL and SPIPM_TR, etc. For example, as shown in (c) of FIG. 14 , it can be determined that F=24 and G=21. For example, in the example shown in (b) of FIG. 14 , if SPIPM_BL is 38 and SPIPM_BR is 35, the intra prediction modes of sub-blocks J and K may be spatially determined using the values of SPIPM_BL and SPIPM_BR, etc. For example, as shown in (c) of FIG. 14 , it can be determined that J=38 and K=35.

Information to be additionally entropy encoded/entropy decoded for sub-block-wise intra prediction based on the equal spatial model may be at least one of the following.

Information indicating whether equal-space model-based per-subblock intra prediction has been performed for the current block: ES_flag

Index indicating the SPIPM collection used: SPIPM_idx

Now, a description will be given of another embodiment of deriving a sub-block based intra prediction mode using a bilinear filter model.

FIG. 15 is a diagram illustrating another embodiment of deriving a sub-block based intra prediction mode.

In order to determine the sub-block based intra prediction mode using a bilinear filter model, at least two SPIPM may be required. For example, as shown in (a) of FIG. 15 , a total of four candidate modes may be selected by selecting one of the candidate modes of SPIPM_TL, one of the candidate modes of SPIPM_TR, one of the candidate modes of SPIPM_BL, and one of the candidate modes of SPIPM_BR. candidate mode. As shown in FIG. 9 , the selected four SPIPM candidate modes may be sequentially populated into the SPIPM list in ascending order of the sum of IPMD values.

The mode of the upper left sub-block (sub-block A in (a) of FIG. 15 ) in the current block may be determined as SPIPM_TL. Furthermore, the mode of the upper right sub-block (sub-block D in (a) of FIG. 15 ) in the current block may be determined as SPIPM_TR. Furthermore, the mode of the lower left sub-block (sub-block M in (a) of FIG. 15 ) in the current block may be determined as SPIPM_BL. Furthermore, the mode of the lower right sub-block (sub-block P in (a) of FIG. 15 ) in the current block may be determined as SPIPM_BR. As shown in (b) of FIG. 15 , the intra prediction modes of the upper left, upper right, lower left and lower right sub-blocks in the current block can be determined as SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR respectively. However, the intra prediction modes of the upper left, upper right, lower left, and lower right sub-blocks in the current block are not limited to SPIPM_TL, SPIPM_TR, SPIPM_BL, and SPIPM_BR, and the upper left, upper right, lower left sub-blocks in the current block may be and at least one of the intra prediction modes of the lower right sub-block is determined to be at least one of SPIPM_TL, SPIPM_TR, SPIPM_BL and SPIPM_BR.

A bilinear filter scheme may be used to determine intra prediction modes for other sub-blocks. For example, the following [Equation 5] can be used. In [Equation 5], function() may be at least one of floor() or ceil() or round(). In the example shown in Figure 15, function() may be round(). Furthermore, in [Equation 5], #of SubBlk in wdt may represent the number of horizontal sub-blocks in the current block. Similarly, #of SubBlk in hgt can represent the number of vertical sub-blocks in the current block.

[Equation 5]

For example, as shown in (c) of FIG. 15 , [Equation 5] may be used to determine the intra prediction mode of the remaining sub-block.

Information to be additionally entropy encoded/entropy decoded for sub-block-wise intra prediction based on the bilinear filter model may be at least one of the following.

Information indicating whether per-subblock intra prediction based on the bilinear filter model has been performed for the current block: BF_flag

Index indicating the SPIPM collection used: SPIPM_idx

The intra prediction mode may be derived based on the sub-block using at least one of the intra prediction modes of the block that has been encoded/decoded by intra prediction among the reconstructed blocks adjacent to the current block and the intra prediction mode of the current block, and The derived intra prediction mode may be used to perform intra prediction on a sub-block basis. Here, samples included in a sub-block previously encoded/decoded on a sub-block basis may be used as reference samples for subsequent sub-block-by-sub-block intra prediction.

The encoder may generate the transform coefficient by performing at least one of a first transform, a second transform, and quantization on a residual block generated after sub-block intra prediction. The resulting transform coefficients may be entropy coded. First transform, second transform and quantization can be performed on the current block or on a sub-block basis. For example, at least one of the first transform, the second transform, and the quantization may be performed for the entire current block, or at least one of the first transform, the second transform, and the quantization may be performed for each subblock. Here, the first transform, the second transform, and the quantization may not be performed for the current block or sub-block.

The transform coefficients can be entropy decoded in the decoder. The reconstructed residual block may be generated by performing at least one of inverse quantization, first inverse transform, and second inverse transform on the entropy-decoded transform coefficients. First transform, second transform and quantization can be performed on the current block or on a sub-block basis. For example, at least one of the first transform, the second transform, and the quantization may be performed for the entire current block, and at least one of the first transform, the second transform, and the quantization may be performed for each subblock. Here, the first transform, the second transform, and the quantization may not be performed for the current block or sub-block.

Intra prediction information can be entropy encoded/entropy decoded from the bitstream. Here, the intra prediction information may be signaled in at least one of VPS, SPS, PPS, APS, slice header, and parallel block header.

Flag indicating whether the MPM matches: e.g. prev_intra_luma_pred_flag

Index indicating position in the MPM list: for example, mpm_idx

Intra-frame luma prediction mode information: for example, rem_intra_luma_pred_mode

Intra chroma prediction mode information: for example, intra_chroma_pred_mode

Flag indicating that the intra prediction modes of neighboring blocks are used to derive the intra prediction modes of the current block and sub-blocks: for example, NDIP_flag

When deriving the intra prediction mode of the current block using N MPM lists or entropy encoding/entropy decoding the intra prediction mode of the current block, indicating for each of the N MPM lists the same as the intra prediction mode of the current block Indicator (MPM flag) whether the intra prediction mode is included in the intra prediction mode of the MPM list: for example, MPM_FLAG_1, MPM_FLAG_2, ..., MPM_FLAG_N

When the same intra prediction mode as the intra prediction mode of the current block is included in the intra prediction mode of a specific one of the N MPM lists, the position or order of the intra prediction mode in the MPM list is indicated. Index information: for example, MPM_IDX_1, MPM_IDX_2, ..., MPM_IDX_N

Information indicating whether transform model-based sub-block intra prediction has been performed for the current block and an index indicating the SPIPM set used: e.g., TBIP_flag and SPIPM_idx

Information indicating whether the intra prediction mode has been derived based on sub-blocks using an equal spatial model for the current block and an index indicating the SPIPM set used: ES_flag and SPIPM_idx

Information indicating whether the intra prediction mode has been derived based on sub-blocks using a bilinear filter model for the current block and an index indicating the SPIPM set used: BF_flag and SPIPM_idx

When the MPM (Most Likely Mode) flag is 1, the intra prediction mode of the luma component may be derived from candidate modes including the intra modes of neighboring units that have been encoded/decoded by using the MPM index mpm_idx.

When the MPM (Most Likely Mode) flag is 0, the intra prediction mode of the luma component may be encoded/decoded by using the intra prediction mode information rem_intra_luma_pred_mode on the luma component.

The intra prediction mode of the chroma component may be encoded/decoded by using the intra prediction mode information intra_chroma_pred_mode on the chroma component and/or the corresponding intra prediction mode of the chroma component block.

The intra prediction information may be entropy encoded/entropy decoded from the bitstream based on at least one of the encoding parameters. For example, NDIP_flag may be encoded/decoded based on block partition information.

For example, if at least one of split_flag, quadtree_flag, and binarytree_flag is "0", and therefore the block is no longer divided, NDIP_flag may be encoded/decoded. For example, if binarytree_flag is 1, NDIP_flag may not be encoded/decoded.

At least one of the plurality of pieces of intra prediction information may not be signaled based on at least one of a size and a shape of the block.

For example, if the size of the current block is a predetermined size, at least one piece of the intra prediction information about the current block may not be signaled, and information about the intra prediction corresponding to the size of the previously encoded/decoded upper layer block may be used. At least one message in the message. For example, if the shape of the current block is a rectangle, at least one piece of the intra prediction information about the current block may not be signaled, and the information about the intra prediction corresponding to the size of the previously encoded/decoded upper layer block may be used at least one piece of information in .

When entropy encoding/entropy decoding is performed on at least one piece of intra prediction information, at least one of the following binarization methods may be used.

-Truncated Rice binarization method

-K-order exponential Columbus binarization method

-Finite K-order exponential Columbus binarization method

-Fixed length binarization method

-Union binarization method

-Truncated unary binarization method

Now, a detailed description of the reference sample point construction step S520 will be given.

In the step of intra-predicting a current block or a sub-block having a smaller size and/or shape than the current block based on the derived intra-prediction mode, reference samples for prediction may be constructed. The following description is given in the context of the current block, and the current block may be meant as a sub-block. The reference sample can be constructed using one or more reconstructed samples or combinations of samples adjacent to the current block. Additionally, filtering can be applied during the step of constructing the reference samples. Here, each reconstructed sample point on the multiple reconstructed sample point lines can be used as is to construct the reference sample point. Alternatively, the reference samples can be constructed after filtering between samples on the same reconstructed sample line. Alternatively, the reference samples can be constructed after filtering between samples on different reconstructed sample lines. The constructed reference sample point can be represented by ref[m,n], and the reconstructed neighboring sample point or the sample point obtained by filtering the reconstructed neighboring sample point can be represented by rec[m,n]. Here, m or n may be a predetermined integer value. In the case where the size of the current block is W (horizontal) × H (vertical), if the uppermost sample point position of the current block is (0, 0), the upper leftmost side reference that is closest to the sample point position can be The relative position of the sample point is set to (-1,-1).

Figure 16 is an exemplary diagram illustrating adjacent reconstructed sample lines that may be used for intra prediction of the current block.

As shown in Figure 16, one or more reconstructed sample lines adjacent to the current block may be used to construct the reference sample.

For example, one of the plurality of reconstructed splines shown in Figure 16 may be selected, and the reference samples may be constructed using the selected reconstructed splines. A predetermined one of the plurality of reconstruction splines may be fixedly selected as the selected reconstruction spline. Alternatively, a specific one of the plurality of reconstruction splines may be adaptively selected as the selected reconstruction spline. In this case, an indicator for the selected reconstructed sample line may be signaled.

For example, one or more of the plurality of reconstructed sample lines shown in Figure 16 may be used in combination to construct the reference sample. For example, the reference sample may be constructed as a weighted sum (or weighted average) of one or more reconstructed samples. The weights used for the weighted sum may be assigned based on distance from the current block. Here, shorter distances from the current block may be assigned greater weight. For example, the following [Equation 6] can be used.

[Equation 6]

ref[-1,-1]＝(rec[-2,-1]+2*rec[-1,-1]+rec[-1,-2]+2)>>2

ref[x,-1]＝(rec[x,-2]+3*rec[x,-1]+2)>>2, (x＝0～W+H-1)

ref[-1,y]＝(rec[-2,y]+3*rec[-1,y]+2)>>2, (y＝0～W+H-1)

Alternatively, the reference sample may be constructed using at least one of the average, maximum, minimum, median and most frequent values of a plurality of reconstructed samples based on at least one of distance from the current block or intra prediction mode .

Alternatively, the reference sample points may be constructed based on changes (variations) in the values of a plurality of consecutive reconstructed sample points. For example, the reference sample point may be constructed based on at least one of whether the difference between the values of two consecutive reconstructed sample points is equal to or greater than a threshold, whether the values of two consecutive reconstructed sample points change continuously or discontinuously, and the like. For example, if the difference between rec[-1,-1] and rec[-2,-1] is equal to or greater than the threshold, ref[-1,-1] can be determined as rec[-1,-1] Or the value obtained by applying a weighted average using predetermined weights assigned to rec[-1,-1]. For example, if the values of multiple consecutive reconstructed sample points change n each time as they get closer to the current block, then the reference sample point ref[-1,-1] can be determined as rec[-1 ,-1]-n.

The number and position of the reconstructed sample lines and used for construction may be determined differently depending on whether the upper or left boundary of the current block corresponds to the boundary of at least one of a picture, a slice, a parallel block, and a coding tree block (CTB). At least one of the construction methods of the reference sample point.

For example, in the step of constructing reference samples using reconstructed sample lines 1 and 2, when the upper side boundary of the current block corresponds to the CTB boundary, reconstructed sample line 1 is available for the upper side and reconstructed sample lines 1 and 2 are available on the left.

For example, in the step of constructing reference samples using reconstructed sample lines 1 to 4, when the upper side boundary of the current block corresponds to the CTB boundary, reconstructed sample lines 1 and 2 can be used for the upper side and reconstructed sample lines 1 to 4 available for left side.

For example, in the step of constructing reference samples using reconstructed sample line 2, when the upper side boundary of the current block corresponds to the CTB boundary, reconstructed sample line 1 may be used for the upper side and reconstructed sample line 2 may be used for the left side.

One or more reference sample lines can be constructed through the above processing.

The reference sample construction method for the upper side of the current block may be different from the reference sample construction method for the left side of the current block.

Information indicating that the reference sample has been constructed using at least one of the above methods may be encoded/decoded. For example, information indicating whether multiple reconstructed sample lines were used may be encoded/decoded.

If the current block is divided into multiple sub-blocks, and each sub-block has an independent intra prediction mode, a reference sample can be constructed for each sub-block.

FIG. 17 is a diagram illustrating an embodiment of constructing reference samples for sub-blocks included in the current block.

As shown in Figure 17, if the size of the current block is 16×16 and the 16 4×4 sub-blocks have independent intra prediction modes, the following method can be used according to the scanning scheme used to predict the sub-blocks. At least one to construct reference samples for each sub-block.

For example, the reference samples can be constructed for each sub-block using N reconstructed sample lines adjacent to the current block. In the example shown in Figure 17, N is 1.

For example, in the case of predicting multiple sub-blocks in the raster scanning order of 1→2→3→…→15→16, the left, upper, upper right and lower left sub-blocks that have been encoded/decoded can be used The reference sample points for the K-th sub-block are constructed from at least one sample point in .

For example, in the case of predicting multiple sub-blocks in the Z scanning order of 1→2→5→6→3→4→7→…→12→15→16, the encoded/decoded left and right sides can be used. Sample points of at least one of the upper, upper right and lower left sub-blocks are used to construct a reference sample for the K-th sub-block.

For example, in the case of predicting multiple sub-blocks in a sawtooth scanning order of 1→2→5→9→6→3→4→...→12→15→16, the encoded/decoded left, Sample points of at least one of the upper, upper right and lower left sub-blocks are used to construct a reference sample for the K-th sub-block.

For example, in the case of predicting multiple sub-blocks in the vertical scanning order of 1→5→9→13→2→6→...→8→12→16, the left and upper sides that have been encoded/decoded can be used. , the sample point of at least one of the upper right side and the lower left sub-block is used to construct the reference sample point for the K-th sub-block.

In the case where multiple sub-blocks are predicted in a scanning order other than the above scanning order, samples of at least one of the left, upper, upper right and lower left sub-blocks that have been encoded/decoded may be used. Construct reference samples for the Kth sub-block.

In the step of selecting the reference samples, determination and/or filling of the availability of blocks including the reference samples may be performed. For example, if a block containing the reference samples is available, the reference samples can be used. At the same time, if a block containing a reference sample is unavailable, padding can be used to replace the unavailable reference sample with one or more available neighboring reference samples.

If the reference sample exists outside at least one of a picture boundary, a tile boundary, a slice boundary, a CTB boundary, and a predetermined boundary, it may be determined that the reference sample is unavailable.

In the case where the current block is encoded by CIP (Constrained Intra Prediction), if the block including the reference samples is encoded/decoded in the inter prediction mode, it may be determined that the reference samples are not available.

FIG. 18 is a diagram illustrating a method of replacing unavailable reconstruction sample points with available reconstruction sample points.

If a nearby reconstructed sample point is determined to be unavailable, the unavailable sample point can be replaced with a nearby available reconstructed sample point. For example, as shown in Figure 18, where there are available and unavailable sample points, one or more available sample points may be used to replace the unavailable sample points.

The sample values of unavailable sample points can be replaced with the sample values of available sample points in a predetermined order. Unavailable sample points can be replaced with available sample points adjacent to the unavailable sample points. In the absence of adjacent available samples, the first available sample or the closest available sample may be used. The replacement order of unavailable sample points can be from the lower left side to the upper right side. Or the replacement order of unavailable sample points can be from the uppermost right side to the lower leftmost side. Or the replacement order of unavailable sample points may be the order from the upper left side to the lower right side and/or the lower left side. Or the replacement order of unavailable sample points may be the order from the uppermost right side and/or the lowermost left side to the uppermost left side.

As shown in Figure 18, unavailable sample points can be replaced in order from the lower left sample point position 0 to the upper right sample point. In this case, the values of the first four unavailable samples can be replaced with the value of the first or closest available sample a. The value of the last available sample point b can be used to replace the values of the next 13 unavailable sample points.

Alternatively, a combination of available sample points can be used to replace unavailable sample points. For example, the unavailable sample points can be replaced with the median value of the available samples adjacent to either end of the unavailable sample point. For example, in Figure 18, the first four unavailable samples can be filled using the value of available sample a, and the next 13 unavailable samples can be filled using the median value of available sample b and available sample c. Alternatively, the 13 unavailable samples can be filled with any value between the values of available sample b and available sample c. In this case, the unavailable sample points can be replaced with different values. For example, when the unavailable sample point is closer to the available sample point a, the value of the unavailable sample point can be replaced with a value close to the value of the available sample point a. Similarly, when the unavailable sample point is closer to the available sample point b, the value of the unavailable sample point can be replaced with a value that is close to the value of the available sample point b. That is, the value of the unavailable sample point may be determined based on the distance from the unavailable sample point to the available sample points a and/or b.

To replace unavailable sample points, one or more of a plurality of methods including the above methods may be selectively applied. The method for replacing unavailable samples may be signaled by information included in the bitstream, or a method predetermined by the encoder and decoder may be used. Or a method for replacing unusable sample points can be derived through a predetermined scheme. For example, the method for replacing unusable samples may be selected based on the difference between the values of available samples a and b and/or the number of unusable samples. For example, the method for replacing unusable samples may be selected based on a comparison between the difference between the values of two available samples and a threshold and/or a comparison of the number of unusable samples and a threshold. For example, if the difference between the values of two available samples is greater than a threshold and/or if the number of unavailable samples is greater than a threshold, the values of the unavailable samples may be replaced with different values.

For the constructed one or more reference samples, it may be determined whether to apply filtering according to at least one of an intra prediction mode, a size, and a shape of the current block. If filtering is applied, different filter types may be used depending on at least one of intra prediction mode, size and shape of the current block.

For example, whether to apply filtering and/or the filter type may be determined differently for each of a plurality of reference sample lines. For example, filtering may be applied to a first adjacent line, but filtering may not be applied to a second adjacent line. For example, both filtered and unfiltered values may be used for the reference samples. For example, among the 3-tap filter, the 5-tap filter, and the 7-tap filter, at least one filter may be selected and applied according to at least one of the intra prediction mode, size, and shape of the block.

Hereinafter, the step of performing intra prediction (S530) will be described in detail.

Intra prediction may be performed on the current block or sub-block based on the derived intra prediction mode and reference samples. In the following description, the current block may be meant as a sub-block.

For example, non-directional intra prediction may be performed. The non-directional intra prediction mode may be at least one of DC mode and planar mode.

Intra prediction of DC mode may be performed using the median of one or more of the constructed reference samples. Filtering may be applied to one or more prediction samples at the boundaries of the current block. DC mode intra prediction may be adaptively performed according to at least one of a size and a shape of a current block.

FIG. 19 is an exemplary diagram illustrating intra prediction according to the shape of the current block.

For example, as shown in (a) of FIG. 19 , if the shape of the current block is a square, the current block can be predicted using the median value of the reference samples on the upper and left sides of the current block.

For example, as shown in (b) of FIG. 19 , if the shape of the current block is a rectangle, the current block can be predicted using the median value of the reference sample points adjacent to the longer side among the width and length of the current block. .

For example, if the size of the current block is within a predetermined range, predetermined samples are selected from upper or left reference samples of the current block, and prediction may be performed using a median value of the selected samples.

Planar mode intra prediction may be performed by calculating a weighted sum considering the distance of the target intra prediction sample of the current block from one or more constructed reference samples.

For example, the prediction block can be calculated as a weighted sum of N reference samples based on the position (x, y) of the target prediction sample. N can be a positive integer, for example, 4.

For example, directional intra prediction may be performed. The directional prediction mode may be at least one of a horizontal mode, a vertical mode, and a mode with a predetermined angle.

Horizontal/vertical mode intra prediction may be performed using one or more reference samples on a horizontal/vertical line at the location of the target intra prediction sample.

Intra prediction in a mode with a predetermined angle may be performed using one or more reference samples on a line with a predetermined angle relative to the location of a target intra prediction sample. Here, N sample points can be used. N can be a positive integer, such as 2, 3, 4, 5, or 6. Furthermore, prediction may be performed by applying an N-tap filter such as a 2-tap, 3-tap, 4-tap, 5-tap, or 6-tap filter, for example.

For example, intra prediction may be performed based on location information. The location information can be encoded/decoded, and the reconstructed sample block at that location can be derived as an intra prediction block for the current block. Alternatively, blocks detected by the decoder that are similar to the current block may be derived as intra-predicted blocks for the current block.

For example, intra color component prediction may be performed. For example, intra prediction may be performed for the chrominance component using the reconstructed luma component of the current block. Alternatively, intra prediction may be performed for another chroma component Cr using one reconstructed chroma component Cb of the current block.

Intra prediction may be performed by using one or more of the various intra prediction methods described above in combination. For example, an intra prediction block may be constructed for the current block by a weighted sum of blocks predicted using a predetermined non-directional intra prediction mode and blocks predicted using a predetermined directional intra prediction mode. Here, different weights may be applied according to at least one of intra prediction mode, block size, shape and/or sample location of the current block.

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

The order applied to the above embodiments may differ between encoders and decoders, or the order applied to the above embodiments may be the same between encoders and decoders.

The above embodiment may be performed on each of the luminance signal and the chrominance signal, or may be performed equally on the luminance signal and the chrominance signal.

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

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

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

The above embodiments of the present invention can be applied according to time layers. In order to identify the time layer to which the above embodiments may be applied, a corresponding identifier may be signaled, and the above embodiment may be applied to a specific time layer indicated by the corresponding identifier. Here, the identifier may be defined as the lowest layer or the highest layer or both the lowest layer and the highest layer to which the above embodiments may be applied, or may be defined to indicate a specific layer to which the embodiments are applied. Furthermore, a fixed time layer to which the embodiments are applied may be defined.

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

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

In the above embodiments, the method is described based on a flow chart having a series of steps or units, but the present invention is not limited to the order of the steps, but some steps may be performed simultaneously with other steps, or may be performed with other steps. Steps are performed in different orders. Furthermore, those of ordinary skill in the art will understand that the steps in the flowcharts are not mutually exclusive and that other steps may be added to the flowcharts or some steps may be removed from the flowcharts without affecting the scope of the present invention. delete.

The embodiments include examples of various aspects. It is not possible to describe all possible combinations of various aspects, but those skilled in the art will be able to recognize different combinations. Therefore, the present invention may include all substitutions, modifications and changes within the scope of the claims.

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

Although the present invention has been described in terms of specific terms, such as detailed elements, and limited embodiments and drawings, they are provided only to aid in a more general understanding of the present invention, and the present invention is not limited to the above embodiments. It will be understood by those skilled in the art that various modifications and changes can be made from the above description.

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

Industrial availability

The present invention can be used to encode/decode video.

Claims (14)

1. An image decoding method, comprising: Derive the intra prediction mode of the current block; Derive reference samples that will be used for intra prediction of the current block; Generate a prediction block for the current block by performing intra prediction for the current block based on the intra prediction mode and the reference sample; and reconstruct the current block based on the predicted block, wherein the intra prediction mode of the current block is derived using statistical values of the intra prediction modes of two or more neighboring blocks of the current block, wherein the intra prediction mode of the chroma block is derived as the intra prediction mode of the corresponding luma block, the corresponding luma block being a luma block including a sample point corresponding to the center position of the chroma block, wherein reference samples to be used for intra prediction of the current block are derived based on one reconstruction reference sample line selected from a plurality of reconstruction reference sample lines, Wherein, in the case that the one reconstruction reference sample line is the first reconstruction reference sample line adjacent to the current block, the filter to be used for the current block is derived by applying filtering to the one reconstruction reference sample line. Intra-predicted reference sample points, and in the case where the one reconstructed reference sample line is a second reconstructed reference sample line adjacent to the current block, the one reconstructed reference sample line is not filtered to derive the Reference samples used for intra prediction of the current block. 2. The method of claim 1, Wherein, the minimum value and the maximum value of the intra prediction modes of the two or more neighboring blocks are used as the statistical values of the intra prediction modes of the two or more neighboring blocks. 3. The method of claim 1, Among them, the current block is divided into multiple sub-blocks of the same size, performing intra prediction for each of the plurality of sub-blocks, and The size and number of the plurality of sub-blocks are determined based on the size of the current block. 4. The method of claim 1, wherein said one reconstruction reference sample line is selected based on an identifier included in the bitstream. 5. The method of claim 1, Wherein, the one reconstruction reference sample line is selected based on whether the upper boundary of the current block corresponds to the boundary of the predetermined area. 6. The method of claim 5, Wherein, the predetermined area is a coding tree block. 7. The method of claim 1, Wherein, when the intra prediction mode of the current block is the DC mode, intra prediction is performed using an average value of a plurality of reference sample points adjacent to the longer side of the width and height of the current block. 8. An image coding method, comprising: Determine the intra prediction mode of the current block; Derive reference samples that will be used for intra prediction of the current block; Generate a prediction block for the current block by performing intra prediction for the current block based on the intra prediction mode and the reference sample; and encode the current block based on the predicted block, wherein the intra prediction mode of the current block is encoded using statistical values of the intra prediction modes of two or more neighboring blocks of the current block, wherein the intra prediction mode of the chroma block is derived as the intra prediction mode of the corresponding luma block, the corresponding luma block being a luma block including a sample point corresponding to the center position of the chroma block, wherein reference samples to be used for intra prediction of the current block are derived based on one reconstruction reference sample line selected from a plurality of reconstruction reference sample lines, Wherein, in the case that the one reconstruction reference sample line is the first reconstruction reference sample line adjacent to the current block, the filter to be used for the current block is derived by applying filtering to the one reconstruction reference sample line. Intra-predicted reference sample points, and in the case where the one reconstructed reference sample line is a second reconstructed reference sample line adjacent to the current block, the one reconstructed reference sample line is not filtered to derive the Reference samples used for intra prediction of the current block. 9. The method of claim 8, Wherein, the minimum value and the maximum value of the intra prediction modes of the two or more neighboring blocks are used as the statistical values of the intra prediction modes of the two or more neighboring blocks. 10. The method of claim 8, Among them, the current block is divided into multiple sub-blocks of the same size, performing intra prediction for each of the plurality of sub-blocks, and The size and number of the plurality of sub-blocks are determined based on the size of the current block. 11. The method of claim 8, Wherein, an identifier used to select the one reconstruction reference sample line is encoded into the bit stream. 12. The method of claim 8, Wherein, the one reconstruction reference sample line is selected based on whether the upper boundary of the current block corresponds to the boundary of the coding tree block. 13. The method of claim 8, Wherein, when the intra prediction mode of the current block is the DC mode, intra prediction is performed using an average value of a plurality of reference sample points adjacent to the longer side of the width and height of the current block. 14. A method of transmitting data comprising a bitstream for an image, the method comprising: Obtaining said bitstream for an image; and sending the bitstream of data, Wherein, the bitstream is generated by performing the following steps: Determine the intra prediction mode of the current block; Derive reference samples that will be used for intra prediction of the current block; Generate a prediction block for the current block by performing intra prediction for the current block based on the intra prediction mode and the reference sample; and encode the current block based on the predicted block, wherein the intra prediction mode of the current block is encoded using statistical values of the intra prediction modes of two or more neighboring blocks of the current block, wherein the intra prediction mode of the chroma block is derived as the intra prediction mode of the corresponding luma block, the corresponding luma block being a luma block including a sample point corresponding to the center position of the chroma block, wherein reference samples to be used for intra prediction of the current block are derived based on one reconstruction reference sample line selected from a plurality of reconstruction reference sample lines, Wherein, in the case that the one reconstruction reference sample line is the first reconstruction reference sample line adjacent to the current block, the filter to be used for the current block is derived by applying filtering to the one reconstruction reference sample line. Intra-predicted reference sample points, and in the case where the one reconstructed reference sample line is a second reconstructed reference sample line adjacent to the current block, the one reconstructed reference sample line is not filtered to derive the Reference samples used for intra prediction of the current block.