WO2020197224A1

WO2020197224A1 - Image coding including forming intra prediction mode candidate list

Info

Publication number: WO2020197224A1
Application number: PCT/KR2020/003956
Authority: WO
Inventors: 최장원; 허진; 김승환; 임재현; 이령
Original assignee: 엘지전자 주식회사
Priority date: 2019-03-24
Filing date: 2020-03-23
Publication date: 2020-10-01

Abstract

An image decoding method performed by a decoding device according to the present document comprises the steps of: acquiring information related to prediction of a current block from a bit stream; deriving an intra prediction type for the current block from among intra prediction types on the basis of the information related to prediction; forming an intra prediction mode candidate list of the current block on the basis of intra prediction modes of peripheral blocks around the current block; deriving an intra prediction mode of the current block on the basis of the intra prediction mode candidate list; deriving reference samples of the current block on the basis of the intra prediction type and the intra prediction mode; and producing prediction samples of the current block on the basis of the reference samples.

Description

Image coding constituting the intra prediction mode candidate list

This document relates to video coding constituting an intra prediction mode candidate list.

Recently, demand for high-resolution and high-quality images such as high definition (HD) images and ultra high definition (UHD) images is increasing in various fields. As the image data becomes high-resolution and high-quality, the amount of information or bits to be transmitted is relatively increased compared to the existing image data. Therefore, the image data is transmitted using a medium such as an existing wired or wireless broadband line, or the image data is stored using an existing storage medium. In the case of storage, the transmission cost and storage cost increase.

Accordingly, high-efficiency image compression technology is required to effectively transmit, store, and reproduce information of high-resolution and high-quality images.

According to an embodiment of the present document, a method and apparatus for increasing video/video coding efficiency is provided.

According to an embodiment of the present document, a method and apparatus for using intra prediction when coding an image is provided.

According to an embodiment of the present document, a method and apparatus for constructing an intra prediction mode candidate list for intra prediction during image coding are provided.

According to an embodiment of the present document, a method and apparatus for determining an intra prediction mode of a neighboring block to which CIIP is applied as a specific intra prediction mode during intra prediction.

According to an embodiment of the present document, a video/video decoding method performed by a decoding apparatus is provided.

According to an embodiment of the present document, a decoding apparatus for performing video/video decoding is provided.

According to an embodiment of the present document, a video/video encoding method performed by an encoding device is provided.

According to an embodiment of the present document, there is provided an encoding device that performs video/video encoding.

According to an embodiment of the present document, a computer-readable digital storage medium in which encoded video/image information generated according to the video/image encoding method disclosed in at least one of the embodiments of the present document is stored is provided.

According to an embodiment of the present document, encoded information causing to perform the video/image decoding method disclosed in at least one of the embodiments of the present document by a decoding device or a computer-readable digital storing encoded video/image information Provide a storage medium.

According to this document, overall video/video compression efficiency can be improved.

According to this document, it is possible to reduce hardware and software implementation complexity by using a unified intra prediction mode list construction process for intra prediction types.

According to this document, the coding efficiency of intra prediction can be improved by reducing the dependency according to the intra prediction type by using a unified intra prediction mode list construction process for intra prediction types.

According to this document, it is possible to improve coding efficiency of intra prediction by deriving a reference sample used when MRL is applied and an intra prediction mode is derived as a DC intra prediction mode based on a reference picture index.

1 schematically shows an example of a video/video coding system to which embodiments of this document can be applied.

2 is a diagram schematically illustrating a configuration of a video/video encoding apparatus to which embodiments of the present document can be applied.

3 is a diagram schematically illustrating a configuration of a video/image decoding apparatus to which embodiments of the present document can be applied.

4 shows an example of an intra prediction-based video encoding method.

5 shows an example of an intra prediction-based video decoding method.

6 exemplarily shows an intra prediction procedure.

7 exemplarily shows intra-directional modes of 65 prediction directions.

8 exemplarily shows multiple reference lines that can be used in the MRL.

9A and 9B illustrate an example in which a block to which an ISP is applied is divided into sub-blocks based on the size of the block.

10 shows an example of deriving an MPM list according to applied intra prediction.

11 shows an example of configuring an MPM list of the current block and deriving an intra prediction mode according to the present embodiment.

12A and 12B exemplarily show reference samples used to derive a DC value when the intra prediction type of the current block is MRL and the intra prediction mode of the current block is the DC intra prediction mode.

13 exemplarily shows reference samples used when the intra prediction type of the current block is MRL and the intra prediction mode of the current block is the planar intra prediction mode.

14A and 14B exemplarily show reference samples used to derive a DC value when the intra prediction type of the current block is MRL and the intra prediction mode of the current block is the DC intra prediction mode.

FIG. 15 exemplarily shows a reference sample used when an intra prediction type of a current block is an MRL and an intra prediction mode of the current block is a planar intra prediction mode.

16 and 17 schematically illustrate an example of a video/video encoding method and related components according to the embodiment(s) of the present document.

18 and 19 schematically illustrate an example of a video/video decoding method and related components according to the embodiment(s) of the present document.

20 illustrates a structural diagram of a content streaming system to which embodiments of the present document are applied.

In this document, various changes may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the embodiments of this document to specific embodiments. Terms commonly used in the present specification are used only to describe specific embodiments, and are not intended to limit the technical idea of this document. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present specification, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other features or It is to be understood that the presence or addition of numbers, steps, actions, components, parts or combinations thereof does not preclude the possibility of preliminary exclusion.

Meanwhile, each of the components in the drawings described in the present document is independently illustrated for convenience of description of different characteristic functions, and does not mean that the components are implemented as separate hardware or separate software. For example, two or more of the configurations may be combined to form one configuration, or one configuration may be divided into a plurality of configurations. Embodiments in which each configuration is integrated and/or separated are also included in the scope of the rights of this document, unless departing from the essence of this document.

This document is about video/image coding. For example, the method/embodiment disclosed in this document may be applied to a method disclosed in the VVC (versatile video coding) standard. In addition, the method/embodiment disclosed in this document is an EVC (essential video coding) standard, AV1 (AOMedia Video 1) standard, AVS2 (2nd generation of audio video coding standard), or next-generation video/image coding standard (ex. H.267). or H.268, etc.).

In this document, various embodiments of video/video coding are presented, and the above embodiments may be performed in combination with each other unless otherwise stated.

In this document, a video may mean a set of a series of images over time. A picture generally refers to a unit representing one image in a specific time period, and a slice/tile is a unit constituting a part of a picture in coding. A slice/tile may include one or more coding tree units (CTU). One picture may be composed of one or more slices/tiles. A tile is a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. The tile column is a rectangular region of CTUs, the rectangular region has a height equal to the height of the picture, and the width may be specified by syntax elements in a picture parameter set (The tile column is a rectangular region of CTUs having a height equal to the height of the picture and a width specified by syntax elements in the picture parameter set). The tile row is a rectangular region of CTUs, the rectangular region has a width specified by syntax elements in a picture parameter set, and a height may be the same as the height of the picture (The tile row is a rectangular region of CTUs having a height specified by syntax elements in the picture parameter set and a width equal to the width of the picture). A tile scan may represent a specific sequential ordering of CTUs that partition a picture, the CTUs may be sequentially arranged in a CTU raster scan in a tile, and tiles in a picture may be sequentially arranged in a raster scan of the tiles of the picture. (A tile scan is a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a tile whereas tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture). A slice may include an integer number of complete tiles, which may be contained exclusively in a single NAL unit, or an integer number of consecutive complete CTU rows in a tile of a picture (A slice includes an integer number of complete tiles or an integer number of consecutive tiles). complete CTU rows within a tile of a picture that may be exclusively contained in a single NAL unit)

Meanwhile, one picture may be divided into two or more subpictures. The subpicture may be an rectangular region of one or more slices within a picture.

A pixel or pel may mean a minimum unit constituting one picture (or image). In addition,'sample' may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luma component, or may represent only a pixel/pixel value of a chroma component.

A unit may represent a basic unit of image processing. The unit may include at least one of a specific area of a picture and information related to the corresponding area. One unit may include one luma block and two chroma (ex. cb, cr) blocks. The unit may be used interchangeably with terms such as a block or an area depending on the case. In general, the MxN block may include samples (or sample arrays) consisting of M columns and N rows, or a set (or array) of transform coefficients.

In this document, "A or B" may mean "only A", "only B" or "both A and B". In other words, in this document, "A or B (A or B)" may be interpreted as "A and/or B (A and/or B)". For example, in this document "A, B or C (A, B or C)" means "only A", "only B", "only C", or "any and all combinations of A, B and C ( It can mean any combination of A, B and C)".

A forward slash (/) or comma (comma) used in this document may mean "and/or". For example, "A/B" can mean "A and/or B". Accordingly, "A/B" may mean "only A", "only B", or "both A and B". For example, "A, B, C" may mean "A, B or C".

In this document, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in this document, the expression "at least one of A or B" or "at least one of A and/or B" means "at least one A and B (at least one of A and B)" can be interpreted the same.

In addition, in this document, "at least one of A, B and C" means "only A", "only B", "only C", or "A, B and C May mean any combination of A, B and C". In addition, "at least one of A, B or C (at least one of A, B or C)" or "at least one of A, B and/or C (at least one of A, B and/or C)" It can mean "at least one of A, B and C".

In addition, parentheses used in this document may mean "for example". Specifically, when indicated as "prediction (intra prediction)", "intra prediction" may be proposed as an example of "prediction". In other words, "prediction" in this document is not limited to "intra prediction", and "intra prediction" may be suggested as an example of "prediction". In addition, even when displayed as "prediction (ie, intra prediction)", "intra prediction" may be proposed as an example of "prediction".

In this document, technical features that are individually described in one drawing may be implemented individually or at the same time.

Hereinafter, exemplary embodiments of the present document will be described with reference to the accompanying drawings. Hereinafter, the same reference numerals may be used for the same constituent elements in the drawings, and duplicate descriptions for the same constituent elements may be omitted.

Hereinafter, exemplary embodiments of the present document will be described in more detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are used for the same components in the drawings, and redundant descriptions for the same components may be omitted.

Referring to FIG. 1, a video/image coding system may include a first device (a source device) and a second device (a receiving device). The source device may transmit the encoded video/image information or data in a file or streaming form to the receiving device through a digital storage medium or a network.

The source device may include a video source, an encoding device, and a transmission unit. The receiving device may include a receiving unit, a decoding device, and a renderer. The encoding device may be referred to as a video/image encoding device, and the decoding device may be referred to as a video/image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be configured as a separate device or an external component.

The video source may acquire a video/image through a process of capturing, synthesizing, or generating a video/image. The video source may include a video/image capturing device and/or a video/image generating device. The video/image capture device may include, for example, one or more cameras, a video/image archive including previously captured video/images, and the like. The video/image generating device may include, for example, a computer, a tablet and a smartphone, and may (electronically) generate a video/image. For example, a virtual video/image may be generated through a computer or the like, and in this case, a video/image capturing process may be substituted as a process of generating related data.

The encoding device may encode the input video/video. The encoding apparatus may perform a series of procedures such as prediction, transformation, and quantization for compression and coding efficiency. The encoded data (encoded video/video information) may be output in the form of a bitstream.

The transmission unit may transmit the encoded video/video information or data output in the form of a bitstream to the reception unit of the receiving device through a digital storage medium or a network in a file or streaming form. Digital storage media may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The transmission unit may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcast/communication network. The receiver may receive/extract the bitstream and transmit it to the decoding device.

The decoding device may decode the video/image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding device.

The renderer can render the decoded video/video. The rendered video/image may be displayed through the display unit.

2 is a diagram schematically illustrating a configuration of a video/video encoding apparatus to which embodiments of the present document can be applied. Hereinafter, the video encoding device may include an image encoding device.

2, the encoding device 200 includes an image partitioner 210, a predictor 220, a residual processor 230, an entropy encoder 240, and It may be configured to include an adder 250, a filter 260, and a memory 270. The prediction unit 220 may include an inter prediction unit 221 and an intra prediction unit 222. The residual processing unit 230 may include a transform unit 232, a quantizer 233, an inverse quantizer 234, and an inverse transformer 235. The residual processing unit 230 may further include a subtractor 231. The addition unit 250 may be referred to as a reconstructor or a recontructged block generator. The image segmentation unit 210, the prediction unit 220, the residual processing unit 230, the entropy encoding unit 240, the addition unit 250, and the filtering unit 260 described above may include one or more hardware components ( For example, it may be configured by an encoder chipset or a processor). In addition, the memory 270 may include a decoded picture buffer (DPB), and may be configured by a digital storage medium. The hardware component may further include the memory 270 as an internal/external component.

The image segmentation unit 210 may divide an input image (or picture, frame) input to the encoding apparatus 200 into one or more processing units. For example, the processing unit may be referred to as a coding unit (CU). In this case, the coding unit is recursively divided according to the QTBTTT (Quad-tree binary-tree ternary-tree) structure from a coding tree unit (CTU) or a largest coding unit (LCU). I can. For example, one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure, a binary tree structure, and/or a ternary structure. In this case, for example, a quad tree structure may be applied first, and a binary tree structure and/or a ternary structure may be applied later. Alternatively, the binary tree structure may be applied first. The coding procedure according to this document may be performed based on the final coding unit that is no longer divided. In this case, based on the coding efficiency according to the image characteristics, the maximum coding unit can be directly used as the final coding unit, or if necessary, the coding unit is recursively divided into coding units of lower depth to be optimal. A coding unit of the size of may be used as the final coding unit. Here, the coding procedure may include a procedure such as prediction, transformation, and restoration described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may be divided or partitioned from the above-described final coding unit, respectively. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for inducing a transform coefficient and/or a unit for inducing a residual signal from the transform coefficient.

The unit may be used interchangeably with terms such as a block or an area depending on the case. In general, the MxN block may represent a set of samples or transform coefficients consisting of M columns and N rows. In general, a sample may represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luminance component, or may represent only a pixel/pixel value of a saturation component. A sample may be used as a term corresponding to one picture (or image) as a pixel or pel.

The encoding apparatus 200 subtracts the prediction signal (predicted block, prediction sample array) output from the inter prediction unit 221 or the intra prediction unit 222 from the input video signal (original block, original sample array) to make a residual. A signal (residual signal, residual block, residual sample array) may be generated, and the generated residual signal is transmitted to the converter 232. In this case, as illustrated, a unit that subtracts the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) in the encoder 200 may be referred to as a subtraction unit 231. The prediction unit may perform prediction on a block to be processed (hereinafter, referred to as a current block) and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied in units of the current block or CU. The prediction unit may generate various information related to prediction, such as prediction mode information, as described later in the description of each prediction mode, and transmit it to the entropy encoding unit 240. The information on prediction may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

The intra prediction unit 222 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the vicinity of the current block or may be located apart according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional mode may include, for example, a DC mode and a planar mode (Planar mode). The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to a detailed degree of the prediction direction. However, this is an example, and more or less directional prediction modes may be used depending on the setting. The intra prediction unit 222 may determine a prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 221 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information may be predicted in units of blocks, subblocks, or samples based on correlation between motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be called a collocated reference block, a co-located CU (colCU), and the like, and a reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). May be. For example, the inter prediction unit 221 constructs a motion information candidate list based on neighboring blocks, and provides information indicating which candidate is used to derive a motion vector and/or a reference picture index of the current block. Can be generated. Inter prediction may be performed based on various prediction modes. For example, in the case of a skip mode and a merge mode, the inter prediction unit 221 may use motion information of a neighboring block as motion information of a current block. In the case of the skip mode, unlike the merge mode, a residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the current block is calculated by using the motion vector of the neighboring block as a motion vector predictor and signaling a motion vector difference. I can instruct.

The prediction unit 220 may generate a prediction signal based on various prediction methods to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, as well as simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode to predict a block. The IBC prediction mode or the palette mode may be used for content image/video coding such as a game, for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction in that it derives a reference block in the current picture. That is, the IBC may use at least one of the inter prediction techniques described in this document. The palette mode can be viewed as an example of intra coding or intra prediction. When the palette mode is applied, a sample value in a picture may be signaled based on information about a palette table and a palette index.

The prediction signal generated through the prediction unit (including the inter prediction unit 221 and/or the intra prediction unit 222) may be used to generate a reconstructed signal or may be used to generate a residual signal. The transform unit 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transformation technique uses at least one of DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT (Karhunen-Loeve Transform), GBT (Graph-Based Transform), or CNT (Conditionally Non-linear Transform). Can include. Here, GBT refers to the transformation obtained from this graph when the relationship information between pixels is expressed in a graph. CNT refers to a transformation obtained based on generating a prediction signal using all previously reconstructed pixels. In addition, the conversion process may be applied to a pixel block having the same size of a square, or may be applied to a block having a variable size other than a square.

The quantization unit 233 quantizes the transform coefficients and transmits it to the entropy encoding unit 240, and the entropy encoding unit 240 encodes the quantized signal (information on quantized transform coefficients) and outputs it as a bitstream. have. The information on the quantized transform coefficients may be called residual information. The quantization unit 233 may rearrange the quantized transform coefficients in the form of blocks into a one-dimensional vector form based on a coefficient scan order, and the quantized transform coefficients in the form of the one-dimensional vector It is also possible to generate information about transform coefficients. The entropy encoding unit 240 may perform various encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit 240 may encode together or separately information necessary for video/image reconstruction (eg, values of syntax elements) in addition to quantized transform coefficients. The encoded information (eg, encoded video/video information) may be transmitted or stored in a bitstream format in units of network abstraction layer (NAL) units. The video/video information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/video information may further include general constraint information. In this document, information and/or syntax elements transmitted/signaled from the encoding device to the decoding device may be included in the video/video information. The video/video information may be encoded through the above-described encoding procedure and included in the bitstream. The bitstream may be transmitted through a network or may be stored in a digital storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. For the signal output from the entropy encoding unit 240, a transmission unit (not shown) for transmitting and/or a storage unit (not shown) for storing may be configured as an internal/external element of the encoding apparatus 200, or the transmission unit It may be included in the entropy encoding unit 240.

The quantized transform coefficients output from the quantization unit 233 may be used to generate a prediction signal. For example, a residual signal (residual block or residual samples) may be restored by applying inverse quantization and inverse transform to the quantized transform coefficients through the inverse quantization unit 234 and the inverse transform unit 235. The addition unit 250 adds the reconstructed residual signal to the prediction signal output from the inter prediction unit 221 or the intra prediction unit 222 to obtain a reconstructed signal (restored picture, reconstructed block, reconstructed sample array). Can be created. When there is no residual for a block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block. The addition unit 250 may be referred to as a restoration unit or a restoration block generation unit. The generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, and may be used for inter prediction of the next picture through filtering as described later.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied during picture encoding and/or reconstruction.

The filtering unit 260 may improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, the filtering unit 260 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and the modified reconstructed picture may be converted to the memory 270, specifically, the DPB of the memory 270. Can be saved on. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like. The filtering unit 260 may generate a variety of filtering information and transmit it to the entropy encoding unit 240 as described later in the description of each filtering method. The filtering information may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

The modified reconstructed picture transmitted to the memory 270 may be used as a reference picture in the inter prediction unit 221. When inter prediction is applied through this, the encoding device may avoid prediction mismatch between the encoding device 200 and the decoding device 300 and improve encoding efficiency.

The memory 270 DPB may store the modified reconstructed picture for use as a reference picture in the inter prediction unit 221. The memory 270 may store motion information of a block from which motion information in a current picture is derived (or encoded) and/or motion information of blocks in a picture that have already been reconstructed. The stored motion information may be transferred to the inter prediction unit 221 in order to be used as motion information of spatial neighboring blocks or motion information of temporal neighboring blocks. The memory 270 may store reconstructed samples of reconstructed blocks in the current picture, and may be transmitted to the intra prediction unit 222.

Referring to FIG. 3, the decoding apparatus 300 includes an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, and a filtering unit. It may be configured to include (filter, 350) and memory (memory, 360). The prediction unit 330 may include an inter prediction unit 331 and an intra prediction unit 332. The residual processing unit 320 may include a dequantizer 321 and an inverse transformer 322. The entropy decoding unit 310, the residual processing unit 320, the prediction unit 330, the addition unit 340, and the filtering unit 350 described above are one hardware component (for example, a decoder chipset or a processor). ) Can be configured. In addition, the memory 360 may include a decoded picture buffer (DPB), and may be configured by a digital storage medium. The hardware component may further include the memory 360 as an internal/external component.

When a bitstream including video/image information is input, the decoding apparatus 300 may reconstruct an image in response to a process in which the video/image information is processed by the encoding apparatus of FIG. 2. For example, the decoding apparatus 300 may derive units/blocks based on block division related information obtained from the bitstream. The decoding device 300 may perform decoding using a processing unit applied in the encoding device. Thus, the processing unit of decoding may be, for example, a coding unit, and the coding unit may be divided from a coding tree unit or a maximum coding unit along a quad tree structure, a binary tree structure and/or a ternary tree structure. One or more transform units may be derived from the coding unit. In addition, the reconstructed image signal decoded and output through the decoding device 300 may be reproduced through the playback device.

The decoding apparatus 300 may receive a signal output from the encoding apparatus of FIG. 2 in the form of a bitstream, and the received signal may be decoded through the entropy decoding unit 310. For example, the entropy decoding unit 310 may parse the bitstream to derive information (eg, video/video information) necessary for image restoration (or picture restoration). The video/video information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/video information may further include general constraint information. The decoding apparatus may further decode the picture based on the information on the parameter set and/or the general restriction information. Signaled/received information and/or syntax elements described later in this document may be decoded through the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 decodes information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and a value of a syntax element required for image restoration, a quantized value of a transform coefficient related to a residual. Can be printed. In more detail, the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and includes information on a syntax element to be decoded and information on a neighboring and decoding target block or information on a symbol/bin decoded in a previous step. A context model is determined using the context model, and a symbol corresponding to the value of each syntax element can be generated by performing arithmetic decoding of the bin by predicting the probability of occurrence of a bin according to the determined context model. have. In this case, the CABAC entropy decoding method may update the context model using information of the decoded symbol/bin for the context model of the next symbol/bin after the context model is determined. Among the information decoded by the entropy decoding unit 310, information about prediction is provided to a prediction unit (inter prediction unit 332 and intra prediction unit 331), and entropy decoding is performed by the entropy decoding unit 310. The dual value, that is, quantized transform coefficients and related parameter information may be input to the residual processing unit 320. The residual processing unit 320 may derive a residual signal (a residual block, residual samples, and a residual sample array). In addition, information about filtering among information decoded by the entropy decoding unit 310 may be provided to the filtering unit 350. Meanwhile, a receiver (not shown) for receiving a signal output from the encoding device may be further configured as an inner/outer element of the decoding device 300, or the receiver may be a component of the entropy decoding unit 310. Meanwhile, the decoding apparatus according to this document may be called a video/video/picture decoding apparatus, and the decoding apparatus can be divided into an information decoder (video/video/picture information decoder) and a sample decoder (video/video/picture sample decoder). May be. The information decoder may include the entropy decoding unit 310, and the sample decoder includes the inverse quantization unit 321, an inverse transform unit 322, an addition unit 340, a filtering unit 350, and a memory 360. ), an inter prediction unit 332 and an intra prediction unit 331 may be included.

The inverse quantization unit 321 may inverse quantize the quantized transform coefficients and output transform coefficients. The inverse quantization unit 321 may rearrange the quantized transform coefficients in a two-dimensional block shape. In this case, the rearrangement may be performed based on the coefficient scan order performed by the encoding device. The inverse quantization unit 321 may perform inverse quantization on quantized transform coefficients by using a quantization parameter (for example, quantization step size information) and obtain transform coefficients.

The inverse transform unit 322 obtains a residual signal (residual block, residual sample array) by inverse transforming the transform coefficients.

The prediction unit may perform prediction on the current block and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the information about the prediction output from the entropy decoding unit 310, and may determine a specific intra/inter prediction mode.

The prediction unit 320 may generate a prediction signal based on various prediction methods to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, as well as simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode to predict a block. The IBC prediction mode or the palette mode may be used for content image/video coding such as a game, for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction in that it derives a reference block in the current picture. That is, the IBC may use at least one of the inter prediction techniques described in this document. The palette mode can be viewed as an example of intra coding or intra prediction. When the palette mode is applied, information about a palette table and a palette index may be included in the video/video information and signaled.

The intra prediction unit 331 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the vicinity of the current block or may be located apart according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit 331 may determine a prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 332 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information may be predicted in units of blocks, subblocks, or samples based on correlation between motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. For example, the inter prediction unit 332 may construct a motion information candidate list based on neighboring blocks, and derive a motion vector and/or a reference picture index of the current block based on the received candidate selection information. Inter prediction may be performed based on various prediction modes, and the information about the prediction may include information indicating a mode of inter prediction for the current block.

The addition unit 340 is reconstructed by adding the obtained residual signal to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit 332 and/or the intra prediction unit 331). Signals (restored pictures, reconstructed blocks, reconstructed sample arrays) can be generated. When there is no residual for a block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block.

The addition unit 340 may be referred to as a restoration unit or a restoration block generation unit. The generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, may be output through filtering as described later, or may be used for inter prediction of the next picture.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied in the picture decoding process.

The filtering unit 350 may improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, the filtering unit 350 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and the modified reconstructed picture may be converted to the memory 360, specifically, the DPB of the memory 360. Can be transferred to. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360 may be used as a reference picture in the inter prediction unit 332. The memory 360 may store motion information of a block from which motion information in a current picture is derived (or decoded) and/or motion information of blocks in a picture that have already been reconstructed. The stored motion information may be transmitted to the inter prediction unit 260 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 360 may store reconstructed samples of reconstructed blocks in the current picture, and may be transmitted to the intra prediction unit 331.

In this specification, the embodiments described in the filtering unit 260, the inter prediction unit 221, and the intra prediction unit 222 of the encoding apparatus 200 are respectively the filtering unit 350 and the inter prediction of the decoding apparatus 300. The same or corresponding to the unit 332 and the intra prediction unit 331 may be applied.

Meanwhile, as described above, prediction is performed to increase compression efficiency in performing video coding. Through this, a predicted block including prediction samples for a current block as a coding target block may be generated. For example, when the above-described intra prediction is performed, a correlation between samples may be used, and a difference between an original block and a prediction block, that is, a residual may be obtained. Since the above-described transformation and quantization can be applied to the residual, spatial redundancy can be removed through this. Specifically, an encoding method and a decoding method in which intra prediction is used may be described below.

4 shows an example of an intra prediction-based video encoding method.

Referring to FIG. 4, the encoding apparatus performs intra prediction on a current block (S400). The encoding device may derive an intra prediction mode/type for the current block, derive neighboring reference samples of the current block, and generate prediction samples in the current block based on the intra prediction mode/type and the neighboring reference samples. do. Here, the procedure of determining the intra prediction mode/type, deriving neighboring reference samples, and generating prediction samples may be simultaneously performed, or one procedure may be performed before the other procedure. The encoding apparatus may determine a mode/type applied to the current block from among a plurality of intra prediction modes/types. The encoding apparatus may compare RD costs for the intra prediction modes/types and determine an optimal intra prediction mode/type for the current block.

Meanwhile, the encoding apparatus may perform a prediction sample filtering procedure. Predictive sample filtering may be referred to as post filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

The encoding apparatus generates residual samples for the current block based on the (filtered) prediction samples (S410). The encoding apparatus may compare the prediction samples from original samples of the current block based on a phase, and derive the residual samples.

The encoding apparatus may encode image information including information about the intra prediction (prediction information) and residual information about the residual samples (S420). The prediction information may include the intra prediction mode information and the intra prediction type information. The encoding device may output the encoded image information in the form of a bitstream. The output bitstream may be delivered to a decoding device through a storage medium or a network.

The residual information may include a residual coding syntax to be described later. The encoding apparatus may transform/quantize the residual samples to derive quantized transform coefficients. The residual information may include information on the quantized transform coefficients.

Meanwhile, as described above, the encoding apparatus may generate a reconstructed picture (including reconstructed samples and a reconstructed block). To this end, the encoding apparatus may perform inverse quantization/inverse transformation on the quantized transform coefficients again to derive (modified) residual samples. The reason why the residual samples are transformed/quantized and then inverse quantized/inverse transformed is performed again to derive residual samples that are the same as the residual samples derived from the decoding apparatus as described above. The encoding apparatus may generate a reconstructed block including reconstructed samples for the current block based on the prediction samples and the (modified) residual samples. A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering procedure or the like may be further applied to the reconstructed picture.

5 shows an example of an intra prediction-based video decoding method.

The decoding device may perform an operation corresponding to the operation performed by the encoding device.

Prediction information and residual information may be obtained from the bitstream. Residual samples for the current block may be derived based on the residual information. Specifically, based on quantized transform coefficients derived based on the residual information, inverse quantization is performed to derive transform coefficients, and residual samples for the current block are derived by performing inverse transform on the transform coefficients. can do.

In more detail, the decoding apparatus may derive an intra prediction mode/type for the current block based on the received prediction information (intra prediction mode/type information) (S500). The decoding apparatus may derive neighboring reference samples of the current block (S510). The decoding apparatus generates prediction samples in the current block based on the intra prediction mode/type and the neighboring reference samples (S520). In this case, the decoding apparatus may perform a prediction sample filtering procedure. Predictive sample filtering may be referred to as post filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

The decoding apparatus generates residual samples for the current block based on the received residual information (S530). The decoding apparatus may generate reconstructed samples for the current block based on the prediction samples and the residual samples, and derive a reconstructed block including the reconstructed samples (S540). A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering procedure or the like may be further applied to the reconstructed picture.

The intra prediction mode information may include, for example, flag information (ex. intra_luma_mpm_flag) indicating whether a most probable mode (MPM) is applied to the current block or a remaining mode is applied, and the When MPM is applied to the current block, the prediction mode information may further include index information (ex. intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be composed of an MPM candidate list or an MPM list. In addition, when the MPM is not applied to the current block, the intra prediction mode information includes remaining mode information (ex. intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes excluding the intra prediction mode candidates (MPM candidates). It may contain more. The decoding apparatus may determine an intra prediction mode of the current block based on the intra prediction mode information.

In addition, the intra prediction type information may be implemented in various forms. As an example, the intra prediction type information may include intra prediction type index information indicating one of the intra prediction types. As another example, the intra prediction type information includes reference sample line information (ex. intra_luma_ref_idx) indicating whether the MRL is applied to the current block and, if applied, a reference sample line (eg, intra_luma_ref_idx), and the ISP is the current block. ISP flag information indicating whether it is applied to (ex. intra_subpartitions_mode_flag), ISP type information indicating the split type of subpartitions when the ISP is applied (ex. intra_subpartitions_split_flag), flag information indicating whether PDCP is applied, or LIP application It may include at least one of flag information indicating whether or not. In addition, the intra prediction type information may include a MIP flag indicating whether matrix-based intra prediction (MIP) is applied to the current block.

The intra prediction mode information and/or the intra prediction type information may be encoded/decoded through the coding method described in this document. For example, the intra prediction mode information and/or the intra prediction type information may be encoded/decoded through entropy coding (ex. CABAC, CAVLC) coding.

6 exemplarily shows an intra prediction procedure.

Referring to FIG. 6, as described above, the intra prediction procedure may include determining an intra prediction mode/type, deriving neighboring reference samples, and performing intra prediction (generating a prediction sample). The intra prediction procedure may be performed in an encoding device and a decoding device as described above. In this document, the coding device may include an encoding device and/or a decoding device.

Referring to FIG. 6, the coding apparatus determines an intra prediction mode/type (S600).

The encoding apparatus may determine an intra prediction mode/type applied to the current block from among the above-described various intra prediction modes/types and generate prediction related information. The prediction related information may include intra prediction mode information indicating an intra prediction mode applied to the current block and/or intra prediction mode information indicating an intra prediction type applied to the current block. The decoding apparatus may determine an intra prediction mode/type applied to the current block based on the prediction related information.

For example, when intra prediction is applied, an intra prediction mode applied to a current block may be determined using an intra prediction mode of a neighboring block. For example, the coding apparatus is one of the MPM candidates in the most probable mode (MPM) list derived based on the intra prediction mode and/or additional candidate modes of the neighboring block (ex. left and/or upper neighboring block) of the current block. May be selected based on the received MPM index, or one of the remaining intra prediction modes not included in the MPM candidates (and planner mode) is selected based on MPM reminder information (remaining intra prediction mode information) I can. The MPM list may be configured to include or not include a planner mode as a candidate. For example, when the mpm list includes a planner mode as a candidate, the MPM list may have 6 candidates, and when the MPM list does not include a planner mode as a candidate, the mpm list has 5 candidates. I can. When the MPM list does not include a planar mode as a candidate, a not planar flag (ex. intra_luma_not_planar_flag) indicating whether the intra prediction mode of the current block is not a planar mode may be signaled. For example, the MPM flag is signaled first, and the MPM index and the not planner flag may be signaled when the value of the MPM flag is 1. In addition, the MPM index may be signaled when the value of the not planner flag is 1. Here, the MPM list is configured not to include a planar mode as a candidate, rather than that the planar mode is not MPM m, the planar mode is always considered as MPM, so a not planar flag is signaled first. This is to first check whether it is in planner mode.

For example, whether the intra prediction mode applied to the current block is among the MPM candidates (and planner mode) or the remaining mode may be indicated based on the MPM flag (ex. intra_luma_mpm_flag). A value of 1 of the MPM flag may indicate that the intra prediction mode for the current block is within MPM candidates (and planner mode), and a value of 0 of the MPM flag indicates that the intra prediction mode for the current block is MPM candidates (and planner mode). ) Can indicate not within. The not planar flag (ex. intra_luma_not_planar_flag) value 0 may indicate that the intra prediction mode for the current block is a planar mode, and the not planar flag value 1 indicates that the intra prediction mode for the current block is not a planar mode. I can. The MPM index may be signaled in the form of an mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information may be signaled in the form of rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra prediction mode information may indicate one of all intra prediction modes by indexing the remaining intra prediction modes not included in the MPM candidates (and the planar mode) in the order of prediction mode numbers. The intra prediction mode may be an intra prediction mode for a luma component (sample). Hereinafter, the intra prediction mode information includes at least one of the MPM flag (ex. intra_luma_mpm_flag), the not planar flag (ex. intra_luma_not_planar_flag) the MPM index (ex. mpm_idx or intra_luma_mpm_idx) the remapping intra prediction mode information (rem_intra_luma_pred_mpm_rema_mode). It may include. In this document, the MPM list may be referred to in various terms such as an MPM candidate list and candModeList.

When MIP is applied to the current block, a separate mpm flag (ex. intra_mip_mpm_flag) for MIP, an mpm index (ex. intra_mip_mpm_idx), and remaining intra prediction mode information (ex. intra_mip_mpm_remainder) may be signaled, and the not planar The flag may not be signaled.

In other words, in general, when a block is divided for an image, the current block to be coded and the neighboring block have similar image characteristics. Accordingly, it is highly likely that the current block and the neighboring block have the same or similar intra prediction modes. Accordingly, the encoder can use the intra prediction mode of the neighboring block to encode the intra prediction mode of the current block.

A list of most probable modes (MPM) for the current block of the coding device may be configured. The MPM list may also be referred to as an MPM candidate list. Here, MPM may mean a mode used to improve coding efficiency in consideration of similarity between a current block and a neighboring block during intra prediction mode coding. As described above, the MPM list may be configured including a planner mode, or may be configured excluding a planner mode. For example, when the MPM list includes a planner mode, the number of candidates in the MPM list may be six. In addition, when the MPM list does not include the planner mode, the number of candidates in the MPM list may be five.

The encoding apparatus may perform prediction based on various intra prediction modes, and may determine an optimal intra prediction mode based on the RDO (rate-distortion optimization) based thereon. In this case, the encoding apparatus may determine the optimal intra prediction mode using only the MPM candidates and planar mode configured in the MPM list, or further use the MPM candidates and planar mode configured in the MPM list as well as the remaining intra prediction modes. The optimal intra prediction mode may be determined. Specifically, for example, if the intra prediction type of the current block is a specific type other than the normal intra prediction type (for example, LIP, MRL, or ISP), the encoding apparatus may use only the MPM candidates and the planar mode. The optimal intra prediction mode may be determined by considering intra prediction mode candidates for. That is, in this case, the intra prediction mode for the current block may be determined only among the MPM candidates and the planar mode, and in this case, the mpm flag may not be encoded/signaled. In this case, the decoding apparatus may estimate that the mpm flag is 1 without separately signaling the mpm flag.

Meanwhile, in general, when the intra prediction mode of the current block is not a planner mode but one of MPM candidates in the MPM list, the encoding apparatus generates an mpm index (mpm idx) indicating one of the MPM candidates. If the intra prediction mode of the current block is not included in the MPM list, an MPM ratio indicating the same mode as the intra prediction mode of the current block among the remaining intra prediction modes not included in the MPM list (and planner mode). Generates maintainer information (remaining intra prediction mode information). The MPM reminder information may include, for example, an intra_luma_mpm_remainder syntax element.

The decoding apparatus acquires intra prediction mode information from the bitstream. As described above, the intra prediction mode information may include at least one of an MPM flag, a not planner flag, an MPM index, and MPM reminder information (remaining intra prediction mode information). The decoding device may construct an MPM list. The MPM list is configured in the same way as the MPM list configured in the encoding device. That is, the MPM list may include intra prediction modes of neighboring blocks, or may further include specific intra prediction modes according to a predetermined method.

The decoding apparatus may determine an intra prediction mode of the current block based on the MPM list and the intra prediction mode information. For example, when the value of the MPM flag is 1, the decoding apparatus derives a planar mode as an intra prediction mode of the current block (based on a not planar flag), or selects a candidate indicated by the MPM index among MPM candidates in the MPM list. It can be derived as the intra prediction mode of the current block. Here, the MPM candidates may indicate only candidates included in the MPM list, or may include not only candidates included in the MPM list, but also a planner mode applicable when the value of the MPM flag is 1.

As another example, when the value of the MPM flag is 0, the decoding apparatus indicates the remaining intra prediction mode information (may be referred to as mpm remainder information) among the remaining intra prediction modes not included in the MPM list and planner mode. An intra prediction mode may be derived as an intra prediction mode of the current block. On the other hand, as another example, when the intra prediction type of the current block is a specific type (ex.LIP, MRL, ISP, etc.), the decoding device may perform the planar mode or the MPM list without parsing/decoding/verifying the MPM flag. A candidate indicated by the MPM flag within the range may be derived as an intra prediction mode of the current block.

The coding apparatus derives neighboring reference samples of the current block (S610). When intra prediction is applied to the current block, surrounding reference samples to be used for intra prediction of the current block may be derived. The neighboring reference samples of the current block are a sample adjacent to the left boundary of the current block of size nWxnH, a total of 2xnH samples adjacent to the bottom-left, and a sample adjacent to the top boundary of the current block. And a total of 2xnW samples adjacent to the top-right side and one sample adjacent to the top-left side of the current block. Alternatively, the peripheral reference samples of the current block may include a plurality of columns of upper peripheral samples and a plurality of rows of left peripheral samples. In addition, the neighboring reference samples of the current block are a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the bottom boundary of the current block, and the lower right side of the current block. It may include one sample adjacent to (bottom-right).

On the other hand, when MRL is applied (that is, when the value of the MRL index is greater than 0), the neighboring reference samples may be located on lines 1 to 2, not on line 0 adjacent to the current block on the left/top side. In this case, the number of neighboring reference samples may be further increased. Meanwhile, when the ISP is applied, the neighboring reference samples may be derived in units of sub-partitions.

The coding apparatus derives prediction samples by performing intra prediction on the current block (S620). The coding apparatus may derive the prediction samples based on the intra prediction mode/type and the surrounding samples. The coding apparatus may derive a reference sample according to the intra prediction mode of the current block from among neighboring reference samples of the current block, and may derive a prediction sample of the current block based on the reference sample.

Meanwhile, when intra prediction is applied to the current block, the encoding device/decoding device may derive an intra prediction mode for the current block as described above, and a prediction sample of the current block based on the intra prediction mode. Can be derived. That is, the encoding device/decoding device may derive the prediction sample of the current block by applying a directional mode or a non-directional mode based on the neighboring reference samples of the current block.

For reference, for example, the intra prediction mode is two non-directional (or non-angular) intra prediction modes and 65 directional (directional, or angular) intra prediction modes. Can include. The non-directional intra prediction modes may include a planar intra prediction mode of No. 0 and a DC intra prediction mode of No. 1, and the directional intra prediction modes may include 65 intra prediction modes of Nos. 2 to 66. . However, this is an example, and this document may be applied even when the number of intra prediction modes is different. Meanwhile, in some cases, the intra prediction mode 67 may be further used, and the intra prediction mode 67 may represent a linear model (LM) mode.

7 exemplarily shows intra-directional modes of 65 prediction directions.

Referring to FIG. 7, an intra prediction mode having horizontal directionality and an intra prediction mode having vertical directionality can be distinguished based on an intra prediction mode 34 having an upward left diagonal prediction direction. H and V in FIG. 6 denote horizontal and vertical directions, respectively, and numbers from -32 to 32 denote a displacement of 1/32 units on a sample grid position. Intra prediction modes 2 to 33 have horizontal directionality, and intra prediction modes 34 to 66 have vertical directionality. The 18th intra prediction mode and the 50th intra prediction mode represent a horizontal intra prediction mode and a vertical intra prediction mode, respectively, and the 2nd intra prediction mode is a left-down diagonal intra prediction mode, The 34th intra prediction mode may be referred to as an upward left diagonal intra prediction mode, and the 66th intra prediction mode may be referred to as an upward right diagonal intra prediction mode.

Meanwhile, as an embodiment of intra prediction, a reference sample line with the highest prediction accuracy is selected from among a plurality of reference sample lines of a current block, and a prediction sample using a reference sample positioned in a prediction direction from the selected reference sample line A method of deriving the can be proposed. The above-described method may be referred to as multi-reference line intra prediction (MRL) or multi-reference line (MRL) based intra prediction.

Specifically, in the conventional intra prediction, only neighboring samples of the upper first line and the neighboring samples of the left first line of the current block may be used as reference samples for intra prediction. However, in the MRL, intra prediction may be performed using neighboring samples located in a sample line separated by a distance of 1, 2, or 3 samples to the upper side and/or the left side of the current block as reference samples.

8 exemplarily shows multiple reference lines that can be used in the MRL.

When the MRL is performed, the decoding apparatus may receive a reference line index. The reference line index may represent one reference line among a plurality of reference lines. The decoding apparatus may perform intra prediction based on reference samples within a reference line indicated by the reference line index. The syntax element of the reference line index may be intra_luma_ref_idx. In addition, the MRL may not be available for blocks on the first line (ie, the first row) in the CTU.

In addition, as an embodiment of intra prediction, a method of dividing a current block in a horizontal direction or a vertical direction and performing intra prediction in units of the divided blocks may be proposed. That is, subblocks may be derived by dividing the current block in a horizontal direction or a vertical direction, and a method of performing intra prediction on each of the subblocks may be proposed. In this case, a reconstructed block may be generated by performing encoding/decoding in units of divided sub-blocks, and the reconstructed block may be used as a reference block of the next divided sub-block. The above-described method may be referred to as Intra Sub-Partitions prediction (ISP prediction), Intra Sub-Partitions mode (ISP), or Intra Sub-Partitions (ISP) based prediction. Alternatively, the above-described method may be referred to as ISP-based intra prediction. In addition, the sub-block may be referred to as an intra sub-partition. In addition, sub-blocks (or sub-partitions) divided according to the ISP may be referred to as TUs (Transform Units).

According to the ISP, the current block may be divided into 2 or 4 sub-partitions in a vertical direction or a horizontal direction based on the size of the current block. For example, when an ISP is performed, the current block size may be divided into sub-blocks equal to the number shown in the following table.

Referring to Table 1, if the size of the current block is 4x4, the ISP may not be available. In addition, when the size of the current block is 4x8 or 8x4, the current block may be divided into two subblocks, and when the size of the current block is other than 4x4, 4x8, and 8x4 size (i.e., If it is larger than 4x8 or 8x4 size), the current block may be divided into four sub-blocks.

Referring to FIG. 9A, when the size of the current block is 4x8 or 8x4, the current block may be divided into two subblocks. In addition, referring to FIG. 9B, when the size of the current block is other than the size of 4x4, 4x8, and 8x4 (that is, when it is larger than the 4x8 or 8x4 size), the current block may be divided into four subblocks. .

Meanwhile, an Mx128 size (M≦64) and a 128xN (N≦64) ISP block (ie, intra sub-partition) may cause a potential problem for a 64x64 VDPU. For example, a CU of Mx128 size in a single tree may have a luma TB of Mx128 size and two chroma TBs of M/2x64 size corresponding to the luma TBs. When an ISP is applied to the CU, the luma TB may be divided into 4 Mx32 TBs, that is, 4 Mx32 sub-blocks (horizontal division only), and each of the TBs is smaller than a 64x64 block. However, in this case, in the design according to the current video standard, the chroma block to which the ISP is applied may not be divided. Accordingly, the size of the TBs of the two chroma components to the TBs of the luma component is larger than a 32x32 block. Likewise, a situation similar to the above-described situation may occur for a CU of 128xN size to which the ISP is applied. Therefore, the above two cases can cause problems in the 64x64 decoder pipeline. For this reason, the maximum size of a CU that can use the ISP may be limited to a 64x64 size.

When the ISP is applied, the encoding device may generate an MPM list according to each division method (eg, horizontal division or vertical division) to reduce coding complexity, and the intra prediction modes in the generated MPM list are bit rate-distorted. It is possible to derive an optimal intra prediction mode by comparing in terms of rate distortion optimization (RDO). On the other hand, when the above-described MRL is used, the ISP cannot be used. That is, the ISP can be applied only when the 0th reference line is used for intra prediction (that is, when the value of intra_luma_ref_idx is 0). In addition, when the ISP is used, PDPC (Position dependent intra prediction, PDPC) cannot be used.

On the other hand, the flag indicating whether the ISP is applied may be transmitted in block units, and when the ISP is applied to the current block, whether the division type is horizontal or vertical, that is, whether the division direction is horizontal or vertical. A flag indicating whether it is a direction may be encoded/decoded. The flag indicating whether the ISP is applied may be called an ISP flag, and the syntax element of the ISP flag may be intra_subpartitions_mode_flag. Also, the flag indicating the split type may be referred to as an ISP split flag, and the syntax element of the ISP split flag may be intra_subpartitions_split_flag.

Syntax elements related to the ISP may be represented as shown in the following table.

The intra_luma_ref_idx shown in Table 2 may be a syntax element of the reference line index. When the ISP is applied, the intra prediction mode for the current block may be equally applied to the subpartitions of the current block, and intra prediction may be performed by deriving neighboring reference samples in units of the sub-partition. Intra prediction performance can be improved. That is, when the ISP is applied, a residual sample processing procedure may be performed in units of sub-partitions. In other words, prediction samples can be derived by performing intra prediction for each sub-partition, and reconstructed samples are derived by adding a residual signal (residual samples) for each sub-partition and prediction samples for each sub-partition. Can be. The residual signal (residual samples) may be derived through an inverse quantization/inverse transform procedure or the like based on residual information (quantized transform coefficient information or residual coding syntax) in the above-described bitstream. Intra prediction for the subpartitions may be performed in the order of the leftmost subpartition to the rightmost subpartition if the partitioning type is vertical partitioning, and if the partitioning type is horizontal partitioning, intra prediction for the subpartitions It can be performed in order from the uppermost subpartition to the lowest subpartition.

For example, prediction samples may be derived by performing intra prediction on the first subpartition of the current block, and residual samples for the first subpartition may be obtained based on residual information on the first subpartition. It may be derived, and reconstructed samples for the first subpartition may be derived based on the prediction samples and the residual samples. Here, when the division type for the current block to which the ISP is applied is vertical division, the first sub-partition may be the leftmost sub-block, and the division type for the current block to which the ISP is applied is horizontal division. , The first sub-partition may be an uppermost sub-block.

Thereafter, in the process of deriving prediction samples for the second sub-partition, some of the reconstructed samples in the first sub-partition are adjacent reference samples for the second sub-partition (e.g., Left or upper peripheral reference samples). Specifically, prediction samples can be derived by performing intra prediction on the second sub-partition of the current block, and residual samples for the second sub-partition are derived based on residual information on the second sub-partition. And reconstructed samples for the second sub-partition may be derived based on the prediction samples and the residual samples. Also, likewise, when the process of deriving prediction samples for the third subpartition is performed, some of the reconstructed samples in the second subpartition are neighboring reference samples for the third subpartition (for example, the May be used as reference samples around the left or upper side of the third subpartition). Also, likewise, when the process of deriving prediction samples for the fourth subpartition is performed, some of the reconstructed samples in the third subpartition are peripheral reference samples for the fourth subpartition (for example, the May be used as reference samples around the left or upper side of the fourth subpartition).

Meanwhile, as another embodiment of intra prediction, a CIIP (Combined Inter and Intra Prediction, CIIP) may be proposed. The CIIP may represent a process of deriving a prediction sample of a current block based on inter prediction and intra prediction. For example, when CIIP is applied to the current block, an intra prediction mode of the current block may be derived, and a first prediction sample of the current block may be derived based on the intra prediction mode. Thereafter, the second prediction sample of the current block may be derived by performing inter prediction on the current block, and the first prediction sample and the second prediction sample are weighted (ie, weighted averaging). Thus, a prediction sample of the current block can be derived. Here, the first prediction sample may be referred to as an intra prediction sample, and the second prediction sample may be referred to as an inter prediction sample. Also, for example, inter prediction for the current block may be inter prediction according to a general merge mode. Specifically, for example, a merge candidate list for the current block may be configured based on motion information of neighboring blocks of the current block, and a merge candidate in the merge candidate list indicated by a merge index for the current block Based on the motion information of the current block, the second prediction sample of the current block may be derived based on the motion information.

Further, for example, a CIIP flag indicating whether the CIIP is applied to the current block may be signaled, and whether to apply the CIIP of the current block may be determined based on the CIIP flag. For example, the CIIP flag is signaled when the current block is coded in merge mode and the current block includes at least 64 luma samples (that is, when the product of the width and height of the current block is 64 or more). I can.

Also, for example, when the CIIP is applied, the intra prediction mode of the current block may be derived based on two syntax elements. For example, one of up to four intra prediction modes may be used as the intra prediction mode. The four intra prediction modes may include a DC intra prediction mode, a planar intra prediction mode, a horizontal intra prediction mode, and/or a vertical intra prediction mode.

For example, in CIIP for the luma component, up to four intra prediction modes including a DC intra prediction mode, a planar intra prediction mode, a horizontal intra prediction mode, and a vertical intra prediction mode may be used. Also, for example, when the width of the current block is more than twice the height, the vertical intra prediction mode may not be available. In this case, only three intra prediction modes are available. In addition, for example, when the height of the current block is more than twice the width, the vertical intra prediction mode may not be available. In this case, only three intra prediction modes are available.

Specifically, for example, when the CIIP of the current block is applied, the intra prediction mode of the current block may be derived as follows. For example, an MPM list including most probable mode (MPM) candidates for the current block may be configured as follows. For example, the MPM list may include three MPM candidates.

For example, the left neighboring block of the current block may be set to A, and the upper neighboring block may be set to B. Thereafter, intra prediction modes of the left neighboring block A and the upper neighboring block B denoted by intraModeA and intraModeB may be derived as follows.

-Set X to A or B

-1) When block X is not available, 2) When block X is not predicted using CIIP or intra prediction mode, 3) When block B is located outside the current CTU, intraModeX is a DC intra prediction mode. Can be set. Here, the current CTU may mean a CTU including the current block.

-If not applicable to the above-described cases, 1) when the intra prediction mode of block X is a DC intra prediction mode or a planar intra prediction mode, intraModeX is an intra prediction mode of the block X, that is, a DC intra prediction mode or a planar intra prediction mode. It may be set as a prediction mode, or 2) if the intra prediction mode of block X is a vertical-like directional intra prediction mode (ie, intra prediction mode 35 to intra prediction mode 66), intraModeX is vertical If the intra prediction mode may be set as the intra prediction mode, or 3) the intra prediction mode of the block X is a horizontal-like directional intra prediction mode (that is, the 2nd intra prediction mode to the 34th intra prediction mode), intraModeX is It may be set to a horizontal intra prediction mode.

Thereafter, MPM candidates may be derived based on the derived intraModeA and intraModeB.

-For example, if intraModeA and intraModeB are the same:

-When intraModeA is a planar intra prediction mode or a DC intra prediction mode, three MPM candidates may be sequentially set to {planar intra prediction mode, DC intra prediction mode, vertical intra prediction mode}.

-Or, if not, that is, when intraModeA is not a planar intra prediction mode and a DC intra prediction mode, three MPM candidates may be sequentially set to {intraModeA, planar intra prediction mode, DC intra prediction mode}.

-Otherwise, that is, if intraModeA and intraModeB are not the same:

-The first two MPM candidates may be set to {intraModeA, intraModeB}.

-Thereafter, it is checked whether the previously derived MPM candidates are included in the order of a planar intra prediction mode, a DC intra prediction mode, and a vertical intra prediction mode, and if it is confirmed as an intra prediction mode other than the derived MPM candidate, the third MPM candidate may be added. have.

On the other hand, for example, when the width of the current block is more than twice the height or the height of the current block is more than twice the width, it may be inferred that the MPM flag is 1 without signaling. Otherwise, the MPM flag for the current block may be signaled.

For example, when the value of the MPM flag is 1, an MPM index indicating one of the MPM candidates in the MPM list may be signaled, and an MPM candidate indicated by the MPM index is derived as an intra prediction mode of the current block. I can. In addition, for example, when the value of the MPM flag is 0, the intra prediction mode of the current block may be set to a "missing" mode. Here, the missing mode may indicate an intra prediction mode that is not included in the MPM list among four intra prediction modes available in CIIP. For example, when a planar intra prediction mode is not included in the MPM list, the missing mode may be the planar intra prediction mode, and when the value of the MPM flag is 0, the intra prediction mode of the current block is the missing mode. The planar intra prediction mode may be derived. Meanwhile, for example, the intra prediction mode of the CU coded with the CIIP may be stored and used for prediction of neighboring CUs coded after the CU.

Meanwhile, as described above, the first prediction sample and the second prediction sample may be weighted averaged. Here, for example, the weights for the first prediction sample and the second prediction sample may be derived based on an intra prediction mode of the current block and/or a location of a current sample in the current block.

Specifically, for example, when the intra prediction mode of the current block is a DC intra prediction mode or a planar intra prediction mode, or the width or height of the current block is less than 4, the same weight is equal to the first prediction sample and the first prediction sample. 2 Can be applied to prediction samples. That is, in other words, when the intra prediction mode of the current block is a DC intra prediction mode or a planar intra prediction mode, or the width or height of the current block is less than 4, the first prediction sample and the second prediction sample are The weights can be derived with the same value.

In addition, in cases other than the above-described case, weights for the first prediction sample and the second prediction sample may be derived based on an intra prediction mode of the current block and a current sample position in the current block. For example, when the intra prediction mode of the current block is a horizontal intra prediction mode, the current block may be divided into partitions of (W/4)xH size, and the current sample is an intra prediction reference sample of the current block. If located in the nearest partition of, the weight for the first prediction sample of the current sample may be set to 6, and the weight for the second prediction sample may be set to 2, and the current sample is the second in the intra prediction reference sample of the current block. If located in a partition close to, the weight for the first prediction sample of the current sample may be set to 5, and the weight for the second prediction sample may be set to 3, and the current sample is the third in the intra prediction reference sample of the current block. If located in the nearest partition, the weight for the first prediction sample of the current sample may be set to 3, and the weight for the second prediction sample may be set to 5, and the current sample is the partition farthest from the intra prediction reference sample of the current block. If positioned at, the weight of the current sample for the first prediction sample may be set to 2, and the weight for the second prediction sample may be set to 6. Here, the size of the current block may be WxH, where W may indicate the width of the current block, and H may indicate the height of the current block.

In addition, for example, when the intra prediction mode of the current block is a vertical intra prediction mode, the current block may be divided into partitions having a size of Wx(H/4), and the current sample is intra prediction of the current block. If located in the partition closest to the reference sample, the weight for the first prediction sample of the current sample may be set to 6 and the weight for the second prediction sample may be set to 2, and the current sample is an intra prediction reference sample of the current block. When located in the second nearest partition in, the weight for the first prediction sample of the current sample may be set to 5, and the weight for the second prediction sample may be set to 3, and the current sample is in the intra prediction reference sample of the current block. When located in the third nearest partition, the weight for the first prediction sample of the current sample may be set to 3, and the weight for the second prediction sample may be set to 5, and the current sample is the most in the intra prediction reference sample of the current block. If located in a distant partition, a weight for the first prediction sample of the current sample may be set to 2, and a weight for the second prediction sample may be set to 6.

Thereafter, a prediction sample of the current sample may be derived by a weighted average of the first prediction sample and the second prediction sample based on the weights. For example, the prediction sample may be derived as the following equation.

Here, P _CIIP is a prediction sample, P _intra is a first prediction sample, P _inter is a second prediction sample, wt is a weight for the first prediction sample, and (8-wt) is a weight for the second prediction sample. Can be indicated.

Meanwhile, when intra prediction is performed as described above, general intra prediction, MRL, and/or ISP may be applied. Here, general intra prediction, MRL, and MPM list generation methods in each of the ISP may be different. In the general intra prediction, 67 intra prediction modes may be used, and in the MRL-based intra prediction, 65 intra prediction modes excluding a planar intra prediction mode and a DC intra prediction mode are used. In the ISP, 66 intra prediction modes excluding a DC intra prediction mode may be used. Since the three intra predictions (general intra prediction, MRL-based intra prediction, and ISP) are all encoded/decoded by intra prediction using different numbers of intra prediction modes, all methods of generating MPM lists for each intra prediction are performed. can be different.

Specifically, when general intra prediction is performed, an MPM list including 6 MPM candidates may be constructed using all 67 intra prediction modes. In addition, when MRL-based intra prediction is performed, an MPM list including 6 MPM candidates may be constructed using 65 intra prediction modes excluding a planar intra prediction mode and a DC intra prediction mode. In addition, when the ISP is performed, an MPM list including 6 MPM candidates may be constructed using 66 intra prediction modes excluding the DC intra prediction mode. Here, the MPM list may be configured in different ways depending on whether the ISP division type is horizontal division or vertical division.

Referring to FIG. 10, the decoding apparatus may determine whether MRL or ISP is applied to the current block (S1005). When the MRL or the ISP is applied to the current block, the decoding apparatus may determine whether the MRL is applied to the current block (S1010). When the MRL is applied to the current block, the decoding apparatus may generate an MRL MPM list for the current block (S1015). Here, the MRL MPM list may represent an MPM list generated according to the MPM list generation method applied to the above-described MRL. Thereafter, the decoding apparatus may parse the MPM index (S1020). The MPM index may indicate an MPM candidate derived as an intra prediction mode of the current block among the MPM candidates. The decoding apparatus may derive an MPM candidate indicated by the MPM index among MPM candidates of the MRL MPM list as an intra prediction mode of the current block.

In addition, when the MRL is not applied to the current block and the ISP is applied, the decoding apparatus may generate an ISP MPM list for the current block (S1025). Here, the ISP MPM list may represent an MPM list generated according to the MPM list generation method applied to the above-described ISP. Thereafter, the decoding apparatus may parse the MPM index (S1020). The decoding apparatus may derive an MPM candidate indicated by the MPM index among MPM candidates of the ISP MPM list as an intra prediction mode of the current block.

Meanwhile, when the MRL and ISP are not applied to the current block, the decoding apparatus may parse the MPM flag for the current block (S1030). Thereafter, the decoding apparatus may determine whether the intra prediction mode for the current block is an MPM mode based on the MPM flag, that is, whether the intra prediction mode for the current block is an MPM candidate included in the MPM list based on the MPM flag. Yes (S1035). Here, the MPM flag may indicate whether the intra prediction mode of the current block is included in the MPM list.

When the intra prediction mode of the current block is the MPM mode, the decoding apparatus may generate an MPM list for general intra prediction (S1040) and parse the MPM index for the current block (S1020). The decoding apparatus may derive an MPM candidate indicated by the MPM index among MPM candidates of the MPM list as an intra prediction mode of the current block.

On the other hand, when the intra prediction mode of the current block is not the MPM mode, when the intra prediction mode of the current block does not belong to MPM candidates, the decoding apparatus is among the remaining intra prediction modes not included in the MPM candidates of the MPM list. Remaining intra prediction mode information indicating one intra prediction mode may be parsed (S1045). The decoding apparatus may derive an intra prediction mode indicated by remaining intra prediction mode information among the remaining intra prediction modes as the intra prediction mode for the current block.

As described above, an MPM list including six MPM candidates may be constructed using different methods according to intra prediction. However, if the method of generating the MPM list is different according to the intra prediction method, coding complexity may be increased and coding efficiency may be reduced.

Accordingly, this document proposes a method of changing the conventional general intra prediction, MRL-based intra prediction, and MPM list generation method used in the ISP into one generalized method. That is, this document proposes a method of generating an MPM list using a generalized method. By using the generalized MPM list generation method, the intra prediction encoding/decoding structure can be simplified, and the video coding efficiency can be improved by increasing the efficiency of encoding/decoding using the intra prediction mode.

In an embodiment, after generating an MPM list using a generalized method, a method of applying an MPM candidate in the MPM list as an intra prediction mode in conventional general intra prediction, MRL-based intra prediction, and ISP intra prediction. Suggest.

For example, an MPM list generation method including six MPM candidates used in conventional general intra prediction may be equally applied as an MPM list generation method of MRL-based intra prediction and ISP-based intra prediction. Here, the MPM list generation method may be a conventional MPM list generation method, or may be an improved method of the conventional MPM list generation method. The MPM list generation method including 6 MPM candidates used in the conventional intra prediction described above is a method of generating an MPM list in consideration of all 67 intra prediction modes, and the MPM list is a planar intra prediction mode as MPM candidates, and / Or may include a DC intra prediction mode. However, since the MRL-based intra prediction does not use a planar intra prediction mode and a DC intra prediction mode, and the ISP-based intra prediction does not use a DC intra prediction mode, a different MPM list construction method may be required.

Referring to FIG. 11, the decoding apparatus may determine whether MRL or ISP is applied to the current block (S1110). When the MRL or ISP is applied to the current block, the decoding apparatus may generate an MPM list of the current block (S1120) and parse the MPM index for the current block (S1130). The decoding apparatus may derive an MPM candidate indicated by the MPM index among MPM candidates of the MPM list as an intra prediction mode of the current block.

In addition, when MRL and ISP are not applied to the current block, the decoding apparatus may parse the MPM flag for the current block (S1140), and the intra prediction mode of the current block is an MPM list based on the MPM flag. It may be determined whether or not included in (S1150). The MPM flag may indicate whether the intra prediction mode of the current block is included in the MPM candidates of the MPM list.

When the intra prediction mode of the current block is an MPM mode, that is, when the MPM flag indicates that the intra prediction mode of the current block is included in the MPM candidates of the MPM list (for example, the value of the MPM flag is 1), the decoding apparatus may generate the MPM list of the current block (S1120). Here, the MPM list may be generated in the same manner as the MPM list generated when MRL or ISP is applied to the current block. Thereafter, the decoding apparatus may parse the MPM index for the current block (S1130), and may derive an MPM candidate indicated by the MPM index among MPM candidates of the MPM list as an intra prediction mode of the current block.

Meanwhile, when the intra prediction mode of the current block is not an MPM mode, that is, when the MPM flag indicates that the intra prediction mode of the current block is not included in the MPM candidates of the MPM list (e.g., the When the value of the MPM flag is 0), the decoding apparatus may parse the remaining intra prediction mode information of the current block (S1160). The decoding apparatus may derive an intra prediction mode indicated by remaining intra prediction mode information among the remaining intra prediction modes as the intra prediction mode for the current block.

Meanwhile, this document proposes a more efficient way of performing intra prediction performed based on the DC intra prediction mode when MRL is applied. For example, in the present embodiment, when the DC intra prediction mode is applied in MRL-based intra prediction (that is, when the intra prediction type of the current block is MRL and the intra prediction mode of the current block is the DC intra prediction mode) We propose a method of calculating the DC value.

12A illustrates a reference sample used to derive a DC value when the current block is a square block. For example, when the reference line indicated by the reference line index is a reference line 0, a reference line 1, a reference line 2, or a reference line 3, the DC value is derived based on reference samples in the area 1200 shown in FIG. 12A. Can be. That is, the DC value is derived based on the number of reference samples equal to the width from the left end reference sample in the upper reference line of the current block and the reference sample equal to the width from the upper reference sample in the left reference line of the current block Can be. In other words, when the size of the current block is WxH and the x and y components of the upper left position of the current block are 0, reference the coordinates in the upper reference line indicated by the reference line index (0, -refIdx-1) A sample to a reference sample of (W-1, -refIdx-1) coordinates, and a reference sample of (-refIdx-1, 0) coordinates in the left reference line indicated by the reference line index to (-refIdx-1, H-1 ) The DC value may be derived based on the reference sample of the coordinates.

For example, the DC value may be derived as the following equation.

Here, dcVal may be a DC value, nTbW may be the width of the current block, and refIdx may indicate a reference line indicated by the reference line index.

In addition, FIG. 12B may represent a reference sample used to derive a DC value when the current block is a non-square block. In the present embodiment, when the current block is an amorphous block, the DC value may be derived based on reference samples in a reference line at the longer of the width and height of the current block. For example, if the reference line indicated by the reference line index is a reference line 0, a reference line 1, a reference line 2, or a reference line 3, a reference in the region 1210 of the longer reference line among the width and height of the current block The DC value may be derived based on samples. For example, when the width of the current block is greater than the height, the DC value may be derived based on the same number of reference samples as the width from the left end reference sample in the upper reference line of the current block. In other words, when the size of the current block is WxH and the x and y components of the upper left position of the current block are 0, reference the coordinates in the upper reference line indicated by the reference line index (0, -refIdx-1) The DC value may be derived based on the sample to the reference sample of the coordinates (W-1, -refIdx-1). The DC value can be derived by the following equation.

Further, for example, when the width of the current block is smaller than the height, the DC value may be derived based on the same number of reference samples as the height from the upper reference sample in the left reference line of the current block. In other words, when the size of the current block is WxH and the x and y components of the upper left position of the current block are 0, reference the coordinates in the left reference line indicated by the reference line index (-refIdx-1, 0) The DC value may be derived based on the sample to the reference sample of the coordinates (-refIdx-1, H-1). The DC value can be derived by the following equation.

Here, dcVal may be a DC value, nTbH may be the height of the current block, and refIdx may indicate a reference line indicated by the reference line index.

Thereafter, a prediction sample of the current block may be derived as the DC value.

Meanwhile, this document proposes a more efficient method of performing intra prediction performed based on the planar intra prediction mode when MRL is applied. For example, in the present embodiment, when the planar intra prediction mode is applied in the MRL-based intra prediction (that is, when the intra prediction type of the current block is MRL and the intra prediction mode of the current block is the planar intra prediction mode) We propose a method of determining reference samples for planar prediction.

Referring to FIG. 13, when a reference line indicated by a reference line index is a reference line 0, a reference line 1, a reference line 2, or a reference line 3, a planner based on reference samples in an area 1300 of the reference line shown in FIG. 13 Prediction can be performed. According to the present embodiment, regardless of the reference line index, planar prediction may be performed based on a sample of +1 at the end of the width/height of the current block. That is, according to the present embodiment, when the x and y components of the upper left position of the current block are 0, the intra prediction type of the current block is MRL, and the intra prediction mode of the current block is the planar intra prediction mode, the upper reference line Planner prediction for the current block may be performed based on a reference sample of the (W, -refIdx-1) coordinate and a reference sample of the (-refIdx-1, H) coordinate of the left reference line.

Referring to this embodiment, the PLANAR intra prediction is performed using reference samples of a reference line indicated by a reference line index, but among reference samples of the reference line, the current sample position in the current block and the same row (i.e., the same y-coordinate ) Of the left reference sample, the reference sample of the upper reference sample in the same column (i.e., the same x-coordinate) as the current sample position and the (W, -refIdx-1) coordinate in the upper reference line, and in the left reference line (-refIdx- 1, H) It may be performed based on a reference sample of coordinates. In this case, a predicted sample value of the current sample may be derived by performing bidirectional linear interpolation based on the values of the above-described four reference samples. Here, the bidirectional linear interpolation may be performed by assuming that the lower left reference sample is positioned below the current sample, and the upper right reference sample is positioned to the right of the current sample.

Meanwhile, an embodiment different from the above-described general intra prediction, MRL, and MPM list generation methods commonly used in ISPs may be used. That is, this document proposes another example of a method of generating an MPM list commonly used in general intra prediction, MRL, and ISP. Another example of the method for generating the MPM list may be shown in the following table.

According to an example of the method for generating an MPM list shown in Table 3, the encoding device/decoding device may derive an intra prediction mode of a left neighboring block of the current block and an intra prediction mode of an upper neighboring block. The intra prediction mode of the left neighboring block may be expressed as leftIntraDir, and the intra prediction mode of the left neighboring block may be expressed as aboveIntraDir.

For example, when generating the MPM list, the intra mode of the surrounding CIIP may not be referenced. In other words, when constructing an MPM list, an intra prediction mode for a neighboring block (left neighboring block or upper neighboring block) may be derived as described above, and the intra prediction mode (leftIntraDir or aboveIntraDir) can be used as a candidate mode of the MPM list. have. However, when the neighboring block is coded with CIIP, the neighboring block is an intra prediction mode, but the intra prediction mode may perform a role for smoothing an inter prediction result rather than indicating the direction/trend of an image. . That is, the intra prediction mode of the neighboring block coded with the CIIP may have a low correlation with the intra prediction mode of the non-CIIP block. Therefore, according to the present embodiment, the intra prediction mode of the neighboring block coded with CIIP is not derived as a candidate mode for constructing the MPM list, and the intra prediction mode of the neighboring block coded with the CIIP is A defined specific mode (planner mode or DC mode) may be used as a candidate mode for configuring the MPM list of the current block.

Also, for example, the encoding device/decoding device may derive a default MPM list. For example, the encoding device/decoding device may derive MPM candidate 0 in the default MPM list as a planar intra prediction mode, MPM candidate 1 may be derived as a DC intra prediction mode, and MPM candidate 2 may be used for vertical intra prediction. Can be derived as a mode, and MPM candidate 3 can be derived as a horizontal intra prediction mode, and MPM candidate 4 is an intra prediction mode of the mode number subtracting 4 from the mode number of the vertical intra prediction mode, i.e., intra prediction mode 46 The MPM candidate 5 may be derived as an intra prediction mode of a mode number obtained by adding 4 to the mode number of the vertical intra prediction mode, that is, the 54th intra prediction mode.

Thereafter, in the encoding/decoding device, the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are the same, and the mode number of the intra prediction mode of the left neighboring block is the mode number of the DC intra prediction mode. You can determine if it is greater than.

For example, when the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block are the same, and the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode, the encoding device/ The decoding apparatus may derive an MPM list of the current block including MPM candidate 0 to MPM candidate 5 derived as described below.

-mpm[0] = PLANAR_IDX

-mpm[1] = leftIntraDir

-mpm[2] = 2 + ((leftIntraDir + 61)% 64)

-mpm[3] = 2 + ((leftIntraDir-1)% 64)

-mpm[4] = DC_IDX

-mpm[5] = 2 + ((leftIntraDir + 60)% 64)

That is, MPM candidate 0 of the MPM list may be derived as a planar intra prediction mode, MPM candidate 1 of the MPM list may be derived as an intra prediction mode of a left neighboring block, and MPM candidate 2 of the MPM list is a mode. Intra prediction mode with a number of 2 + ((leftIntraDir + 61)% 64), i.e., a modulo arithmetic operation of 64 by adding 61 to the mode number of the intra prediction mode of the left neighboring block and adding 2 to the mode number The MPM candidate 3 of the MPM list is an intra prediction mode having a mode number of 2 + ((leftIntraDir-1)% 64), that is, a mode of the intra prediction mode of the left neighboring block. A value obtained by subtracting 1 from the number can be derived as an intra prediction mode having a modulo arithmetic operation of 64 and a value obtained by adding 2 as a mode number, and the MPM candidate 4 of the MPM list can be derived as a DC intra prediction mode. MPM candidate 5 of the MPM list is an intra prediction mode with a mode number of 2 + ((leftIntraDir + 60)% 64), that is, a value obtained by adding 60 to the mode number of the intra prediction mode of the left neighboring block to 64 It can be derived as an intra prediction mode having a value of plus 2 as a mode number.

On the other hand, when the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are not the same, the encoding device/decoding device determines that the mode number of the intra prediction mode of the left neighboring block is the DC intra prediction mode. It may be determined whether the mode number of the intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode.

When the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode, and the mode number of the intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode, encoding device/decoding device May derive the planar intra prediction mode as MPM candidate 0 of the MPM list, the intra prediction mode of the left neighboring block as the MPM candidate 1 of the MPM list, and the intra prediction mode of the upper neighboring block It can be derived as MPM candidate 2 of the MPM list, and the DC intra prediction mode can be derived as MPM candidate 3 of the MPM list. In addition, the encoding device/decoding device may derive maxCandModeIdx as 1 when the mode number of the MPM candidate 1 is greater than the mode number of the MPM candidate 2, and the mode number of the MPM candidate 1 is greater than the mode number of the MPM candidate 2. If it is not large, maxCandModeIdx can be derived as 2. In addition, the encoding device/decoding device may derive minCandModeidx as 2 when the mode number of the MPM candidate 1 is greater than the mode number of the MPM candidate 2, and the mode number of the MPM candidate 1 is greater than the mode number of the MPM candidate 2 If not, maxCandModeIdx can be derived as 1.

Thereafter, if the value obtained by subtracting the mode number of mpm[minCandModeidx] from the mode number of mpm[maxCandModeIdx] is less than 63 and greater than 1, the encoding device/decoding device has a mode number of 2 + ((maxAB + 61)% 64) An intra prediction mode may be derived as MPM candidate 4 of the MPM list, and an intra prediction mode with a mode number of 2 + ((maxAB-1)% 64) may be derived as MPM candidate 5 of the MPM list. Here, when the maxCandModeIdx is 1, mpm[maxCandModeIdx] is an MPM candidate 1, when the maxCandModeIdx is 2, mpm[maxCandModeIdx] is an MPM candidate 2, and when the minCandModeidx is 1, mpm[minCandModeidx] is an MPM candidate 1, and when the minCandModeidx is 2, mpm [minCandModeidx] may be MPM candidate 2. Here, maxAB may be a larger value of a mode number of an intra prediction mode of the left neighboring block and an intra prediction mode of the upper neighboring block.

Alternatively, if the value obtained by subtracting the mode number of mpm[minCandModeidx] from the mode number of mpm[maxCandModeIdx] is 63 or more or 1 or less, the encoding device/decoding device has a mode number of 2 + ((maxAB + 60)% 64). An intra prediction mode may be derived as MPM candidate 4 of the MPM list, and an intra prediction mode having a mode number of 2 + (maxAB% 64) may be derived as MPM candidate 5 of the MPM list.

Meanwhile, the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block of the current block are not the same, or at least one of the mode numbers of the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block is DC If it is smaller than the mode number of the intra prediction mode, the encoding device/decoding device may determine that the sum of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block is equal to or greater than the mode number of the DC intra prediction mode. Can judge whether it is.

When the sum of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block is greater than or equal to the mode number of the DC intra prediction mode, the encoding device/decoding device is the MPM candidate derived as described below. An MPM list of the current block including 0 to MPM candidate 5 may be derived.

-mpm[0] = PLANAR_IDX

-mpm[1] = (leftIntraDir <aboveIntraDir)? aboveIntraDir: leftIntraDir

-mpm[2] = DC_IDX

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

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

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

That is, MPM candidate 0 of the MPM list may be derived as a planar intra prediction mode, and MPM candidate 1 is less than a mode number of an intra prediction mode of the upper neighboring block. If the mode number of the intra prediction mode of the upper neighboring block and the intra prediction mode of the left neighboring block is greater than or equal to the mode number of the intra prediction mode of the upper neighboring block, the intra prediction mode of the left neighboring block may be derived, and the MPM MPM candidate 2 of the list may be derived as a DC intra prediction mode, and MPM candidate 3 of the MPM list is an intra prediction mode having a mode number of 2 + ((maxAB + 61)% 64), that is, of the left neighboring block. It can be derived as an intra prediction mode in which a value obtained by adding 61 to a larger value of the mode number of the intra prediction mode and the mode number of the intra prediction mode of the upper neighboring block is subjected to a modular arithmetic operation to 64 and a value obtained by adding 2 as the mode number. , MPM candidate 4 of the MPM list is an intra prediction mode having a mode number of 2 + ((maxAB-1)% 64), that is, a mode number of an intra prediction mode of the left neighboring block and an intra prediction mode of the upper neighboring block It can be derived as an intra prediction mode having a modulo arithmetic operation by subtracting 1 from the larger of the mode numbers by 64 and adding 2 as the mode number, and the MPM candidate 5 of the MPM list has a mode number of 2 + ( (maxAB + 60)% 64), that is, a value obtained by adding 60 to the larger of the mode number of the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block to 64 It can be derived as an intra prediction mode having an arithmetic operation and a sum of 2 as a mode number.

On the other hand, if the embodiment of the above-described MPM list generation method is expressed in source code, it may be as shown in the following table.

Tables 4 to 5 may be an embodiment represented by one continuous source code.

In addition, if the embodiment of the MPM list generation method described above is expressed in a standard format, it may be as shown in the following table.

Tables 6 to 8 may be examples shown in one continuous standard format.

Meanwhile, when intra prediction according to the intra prediction mode of the current block is expressed in a standard format, it may be as shown in the following table.

In addition, in the above-described present document, an embodiment of intra prediction based on a planar intra prediction mode performed when MRL is applied may be shown in the following table in a standard format.

In addition, in the above-described present document, an example of intra prediction based on DC intra prediction mode performed when MRL is applied may be shown in the following table in a standard format.

In addition, the horizontal transform kernel and the vertical transform kernel derived according to the intra prediction mode may be as follows.

For example, when the intra prediction mode of the current block is determined as the DC intra prediction mode, DCT2 may be used as a vertical direction transform kernel for transform/inverse transform for the residual of the current block, and DCT2 may be used as the horizontal direction transform kernel. Can be used.

Meanwhile, according to this document, among the bins of the bin string of the syntax element of the MPM index, the first bin may be context-based regular coding, and the remaining bins of the bin string are bypass-coded. Can be.

In this case, the context index increment ctxInc for indicating the context model of the first bin is a value of an ISP flag for the current block and/or a value of a reference line index for the current block, as follows: It may be set differently based on at least one of them.

For example, referring to Table 13, when the value of the reference line index is not 0, the ctxInc may be derived as 2, and when the value of the reference line index is 0, the value of the ISP flag is 1 The ctxInc may be derived as 0, and if the value of the ISP flag is not 1, the ctxInc may be derived as 1.

Meanwhile, this document proposes another embodiment of more efficiently performing intra prediction performed based on a DC intra prediction mode when MRL is applied.

14A may show a reference sample used to derive a DC value when the current block is a square block. For example, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2, or reference line 3, the DC value is derived based on reference samples in the region 1400 shown in FIG. 14A. Can be. That is, when the x component and the y component of the upper left position of the current block are 0, the number of reference samples equal to the width from the reference sample of the coordinates (-refIdx, -refIdx-1) in the upper reference line of the current block, and The DC value may be derived based on the number of reference samples equal to the width from reference samples of coordinates (-refIdx-1, -refIdx) in the left reference line of the current block. For example, if the value of the reference line index is 0, the number of reference samples equal to the width from the reference sample of the (0, -1) coordinate in the upper reference line 0 of the current block and the left reference line of the current block The DC value may be derived based on the number of reference samples equal to the width from the reference sample of the (-1, 0) coordinate within 0, and when the value of the reference line index is 1, the upper reference line 1 of the current block The number of reference samples equal to the width from the reference sample of the (-1, -2) coordinate and the number of reference samples equal to the width from the reference sample of the (-2, -1) coordinate in the left reference line 1 of the current block The DC value can be derived based on the values, and if the value of the reference line index is 2, the number of reference samples equal to the width from the reference samples of the coordinates (-2, -3) in the upper reference line 2 of the current block The DC value can be derived based on the number of reference samples equal to the width from reference samples of (-3, -2) coordinates in the left reference line 2 of the current block, and the reference line index value is 3 In this case, the number of reference samples equal to the width from the reference samples of the (-3, -4) coordinate in the upper reference line 3 of the current block and the (-4, -3) coordinate of the left reference line 3 of the current block The DC value may be derived based on the number of reference samples equal to the width from the reference sample.

In addition, FIG. 14B may show a reference sample used to derive a DC value when the current block is a non-square block. In the present embodiment, when the current block is an amorphous block, the DC value may be derived based on reference samples in a reference line at the longer of the width and height of the current block. For example, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2, or reference line 3, the reference line area 1410 of the longer one of the width and height of the current block is referenced. The DC value may be derived based on samples. For example, when the width of the current block is greater than the height, the DC value is based on the same number of reference samples as the width from the reference samples of the coordinates in the upper reference line of the current block (-refIdx, -refIdx-1) Can be derived. For example, when the value of the reference line index is 0, the DC value will be derived based on the number of reference samples equal to the width from the reference sample of the (0, -1) coordinate in the upper reference line 0 of the current block. And, when the value of the reference line index is 1, the DC value will be derived based on the same number of reference samples as the width from the reference sample of the (-1, -2) coordinate in the upper reference line 1 of the current block. If the value of the reference line index is 2, the DC value is derived based on the number of reference samples equal to the width from the reference samples of the coordinates (-2, -3) in the upper reference line 2 of the current block. If the value of the reference line index is 3, the DC value will be derived based on the number of reference samples equal to the width from the reference sample of the (-3, -4) coordinate in the upper reference line 3 of the current block. I can.

In addition, for example, if the width of the current block is smaller than the height, the reference sample is the same number as the height from the reference sample of the (-refIdx-1, -refIdx) coordinate in the left reference line of the current block. DC values can be derived. For example, if the value of the reference line index is 0, the DC value will be derived based on the number of reference samples equal to the height from the reference sample of the (-1, 0) coordinate in the left reference line 0 of the current block. If the value of the reference line index is 1, the DC value will be derived based on the number of reference samples equal to the height from the reference sample of the (-2, -1) coordinate in the left reference line 1 of the current block. If the value of the reference line index is 2, the DC value will be derived based on the number of reference samples equal to the height from the reference sample of the (-3, -2) coordinate in the left reference line 2 of the current block. And, when the value of the reference line index is 3, the DC value will be derived based on the same number of reference samples as the height from the reference sample of the (-4, -3) coordinate in the left reference line 3 of the current block. I can.

Meanwhile, this document proposes another embodiment of more efficiently performing intra prediction performed based on a planar intra prediction mode when MRL is applied.

15 exemplarily shows reference samples used when the intra prediction type of the current block is MRL and the intra prediction mode of the current block is the planar intra prediction mode.

Referring to FIG. 15, when a reference line indicated by a reference line index is a reference line 0, a reference line 1, a reference line 2, or a reference line 3, a planner based on reference samples in an area 1500 of the reference line shown in FIG. 15 Prediction can be performed. According to the present embodiment, regardless of the reference line index, planar prediction may be performed based on samples of +1-refIdx at the end of the width/height of the current block. That is, according to the present embodiment, when the x and y components of the upper left position of the current block are 0, the intra prediction type of the current block is MRL, and the intra prediction mode of the current block is the planar intra prediction mode, the upper reference line Planner prediction for the current block may be performed based on a reference sample of the coordinates within (W-refIdx, -refIdx-1) and a reference sample of coordinates within the left reference line (-refIdx-1, H-refIdx).

Referring to this embodiment, the PLANAR intra prediction is performed using reference samples of a reference line indicated by a reference line index, but among reference samples of the reference line, the current sample position in the current block and the same row (i.e., the same y-coordinate ) Of the left reference sample, the upper reference sample of the same column (i.e., the same x coordinate) as the current sample position and the reference sample of the upper reference line (W-refIdx, -refIdx-1) and the left reference line (- refIdx-1, H-refIdx) may be performed based on a reference sample of coordinates. In this case, a predicted sample value of the current sample may be derived by performing bidirectional linear interpolation based on the values of the above-described four reference samples. Here, the bidirectional linear interpolation may be performed by assuming that the lower left reference sample is positioned below the current sample, and the upper right reference sample is positioned to the right of the current sample.

According to an example of the method for generating an MPM list shown in Table 14, the encoding device/decoding device may derive an intra prediction mode of a left neighboring block of the current block and an intra prediction mode of an upper neighboring block. The intra prediction mode of the left neighboring block may be expressed as leftIntraDir, and the intra prediction mode of the left neighboring block may be expressed as aboveIntraDir.

-mpm[0] = PLANAR_IDX

-mpm[1] = leftIntraDir

-mpm[2] = 2 + ((leftIntraDir + 61)% 64)

-mpm[3] = 2 + ((leftIntraDir-1)% 64)

-mpm[4] = DC_IDX

-mpm[5] = 2 + ((leftIntraDir + 60)% 64)

-mpm[0] = PLANAR_IDX

-mpm[1] = (leftIntraDir <aboveIntraDir)? aboveIntraDir: leftIntraDir

-mpm[2] = DC_IDX

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

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

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

Tables 15 to 16 may be an embodiment represented by one continuous source code.

Tables 17 to 19 may be examples shown in one continuous standard format.

16 and 17 schematically illustrate an example of a video/video encoding method and related components according to the embodiment(s) of this document.

The method disclosed in FIG. 16 may be performed by the encoding apparatus disclosed in FIG. 2 or 17. Specifically, for example, S1600 to S1640 of FIG. 16 may be performed by the prediction unit 220 of the encoding device of FIG. 17, and S1650 of FIG. 16 is performed by the subtraction unit 231 of the encoding device of FIG. 17. It may be performed by, and S1660 of FIG. 16 may be performed by the entropy encoding unit 240 of the encoding device of FIG. 17. Also, although not shown in FIG. 16, prediction samples or prediction-related information may be derived by the prediction unit 220 of the encoding device in FIG. 17, and original samples may be derived by the subtraction unit 231 of the encoding device. Alternatively, residual samples may be derived from predicted samples, and residual information may be derived based on the residual samples by the residual processing unit 230 of the encoding apparatus, and the entropy encoding unit 240 of the encoding apparatus ), a bitstream may be generated from residual information or prediction related information. The method disclosed in FIG. 16 may include the embodiments described above in this document.

The encoding apparatus may determine an intra prediction type for the current block among intra prediction types (S1600). Also, for example, the encoding device may generate information on an intra prediction type based on the intra prediction type. For example, the encoding apparatus may determine the intra prediction type for the current block in consideration of a rate distortion (RD) cost. The intra prediction types are a first intra prediction type using an intra prediction reference line adjacent to the current block, a second intra prediction type using an intra prediction reference line not adjacent to the current block, and Intra Sub-Partitions mode (ISP). ) May be applied to the third intra prediction type. The first intra prediction type may indicate the above-described general intra prediction, the second intra prediction type may indicate the above-described MRL, and the third intra prediction type may indicate the above-described ISP.

For example, the encoding apparatus may generate and encode a reference line index indicating an intra prediction reference line of the current block. It may be determined whether the intra prediction type for the current block is the second intra prediction type based on the reference line index. In addition, for example, when the intra prediction type for the current block is not the second intra prediction type, the encoding apparatus generates and encodes an ISP flag indicating whether the third intra prediction type is applied to the current block. can do. It may be determined whether the intra prediction type for the current block is the third intra prediction type based on the ISP flag. When the ISP flag indicates that the third intra prediction type is applied to the current block, an intra prediction type for the current block may be derived as the third intra prediction type, and the ISP flag is applied to the current block. When it is indicated that the third intra prediction type is not applied, an intra prediction type for the current block may be derived as the first intra prediction type. For example, the information on the intra prediction type may include the reference line index, the ISP flag, and/or the ISP index. The information on the intra prediction type may include the reference line index, and when a value of the reference line index is 0, the prediction related information may further include the ISP flag. In addition, when the value of the ISP flag is 1, the information on the intra prediction type may further include the ISP index. For example, the prediction related information may include information on the intra prediction type.

The encoding apparatus may construct an intra prediction mode candidate list of the current block based on intra prediction modes of neighboring blocks of the current block (S1610). For example, the encoding apparatus may configure an intra prediction mode candidate list based on at least some of the above tables, and the intra prediction mode candidate list may represent the above-described most probable mode (MPM) list.

For example, the encoding apparatus may configure the intra prediction mode candidate list based on the first candidate intra prediction mode and the second candidate intra prediction mode. The encoding apparatus determines whether the first candidate intra prediction mode (mode number of) and the second candidate intra prediction mode (mode number of) are the same and/or the mode number of the first candidate intra prediction mode and/or the second candidate intra prediction mode. The intra prediction mode candidate list may be configured based on whether the mode number of the 2 candidate intra prediction mode is greater than that of the DC intra prediction mode. Here, the first candidate intra prediction mode may be derived based on an intra prediction mode of a left neighboring block of the current block, and the second candidate intra prediction mode based on an intra prediction mode of an upper neighboring block of the current block Can be derived. For example, an intra prediction mode of an adjacent block to the left of the current block may be derived as the first candidate intra prediction mode, and an intra prediction mode of an upper adjacent block of the current block is derived as the second candidate intra prediction mode Can be. Here, the first candidate intra prediction mode may be referred to as a first intra prediction mode, and the second candidate intra prediction mode may be referred to as a second intra prediction mode. That is, the intra prediction mode candidate list may be configured based on a first intra prediction mode for a left neighboring block of the current block and a second intra prediction mode for an upper neighboring block of the current block.

For example, the first intra prediction mode or the second intra prediction mode for a neighboring block to which a CIIP (Combined Inter and Intra Prediction) mode is applied among the left neighboring blocks or the upper neighboring blocks may be determined as a specific intra prediction mode. have. Here, the specific intra prediction mode may be a planar mode. Alternatively, the specific intra prediction mode may be a DC mode. For example, when the CIIP mode is applied to the left neighboring block, the first candidate intra prediction mode may be derived as a specific intra prediction mode. Alternatively, for example, when the CIIP mode is applied to the upper neighboring block, the second candidate intra prediction mode may be derived as a specific intra prediction mode.

For example, the encoding apparatus may configure the intra prediction mode candidate list based on an intra prediction mode of a left neighboring block of the current block and an intra prediction mode of an upper neighboring block of the current block. The encoding apparatus may determine whether the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are the same, and the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode. have. The encoding apparatus determines whether the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are the same and/or whether the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode. The intra prediction mode candidate list may be configured based on whether or not.

When the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block of the current block are the same, and the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode, the encoding apparatus will be described later. As described above, the intra prediction mode candidate list of the current block including intra prediction mode candidates may be derived.

-mpm[0] = PLANAR_IDX

-mpm[1] = leftIntraDir

-mpm[2] = 2 + ((leftIntraDir + 61)% 64)

-mpm[3] = 2 + ((leftIntraDir-1)% 64)

-mpm[4] = DC_IDX

-mpm[5] = 2 + ((leftIntraDir + 60)% 64)

Here, mpm[0], mpm[1], mpm[2], mpm[3], mpm[4] and mpm[5] are intra prediction mode candidate 0, intra prediction mode candidate 1, and intra prediction mode candidate 2, respectively. , Intra prediction mode candidate 3, intra prediction mode candidate 4, and intra prediction mode candidate 5, leftIntraDir indicates the first candidate intra prediction mode, PLANAR_IDX indicates a planar intra prediction mode, and DC_IDX indicates a DC intra prediction mode. I can.

That is, intra prediction mode candidate 0 of the intra prediction mode candidate list may be derived as a planar intra prediction mode, and intra prediction mode candidate 1 of the intra prediction mode candidate list may be derived as an intra prediction mode of a left neighboring block. , Intra prediction mode candidate 2 of the intra prediction mode candidate list is an intra prediction mode having a mode number of 2 + ((leftIntraDir + 61)% 64), that is, a mode number of an intra prediction mode of the left neighboring block plus 61 It can be derived as an intra prediction mode having a modulo arithmetic operation on a value of 64 and adding 2 as a mode number, and the intra prediction mode candidate 3 of the intra prediction mode candidate list has a mode number of 2 + ((leftIntraDir-1) % 64), i.e., an intra prediction mode in which a value obtained by subtracting 1 from the mode number of the intra prediction mode of the left neighboring block is subjected to a modular arithmetic operation to 64 and a value obtained by adding 2 as the mode number. , Intra prediction mode candidate 4 of the intra prediction mode candidate list may be derived as a DC intra prediction mode, and intra prediction mode candidate 5 of the intra prediction mode candidate list has a mode number of 2 + ((leftIntraDir + 60)% 64 ), that is, an intra prediction mode in which a value obtained by adding 60 to the mode number of the intra prediction mode of the left neighboring block is subjected to a modular arithmetic operation to 64 and a value obtained by adding 2 as the mode number. That is, for example, when the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block are the same, and the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode , The intra prediction mode candidate list is the intra prediction mode of the left neighboring block, an intra prediction mode having a mode number of 2 + ((leftIntraDir + 61)% 64), and a mode number of 2 + ((leftIntraDir-1)% 64 ) And an intra prediction mode having a mode number of 2 + ((leftIntraDir + 60)% 64) as intra prediction mode candidates. Here, leftIntraDir may indicate a mode number of an intra prediction mode of the left neighboring block of the current block.

On the other hand, when the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are not the same, for example, the encoding apparatus may determine the mode number of the intra prediction intra prediction mode of the left neighboring block and the upper side. Intra prediction of the neighboring block It may be determined whether at least one of the mode numbers of the intra prediction mode is greater than the mode number of the DC intra prediction mode. When at least one of the mode number of the intra prediction intra prediction mode of the left neighboring block and the mode number of the intra prediction intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode, variable minAB and variable maxAB Can be derived as follows.

-minAB = Min(candIntraPredModeA, candIntraPredModeB)

-maxAB = Max(candIntraPredModeA, candIntraPredModeB)

Here, candIntraPredModeA may indicate a mode number of an intra prediction mode of the left neighboring block of the current block, and candIntraPredModeB may indicate a mode number of an intra prediction mode of the upper neighboring block of the current block. That is, minAB may represent a smaller value of a mode number of an intra prediction mode of the left neighboring block and a mode number of an intra prediction mode of the upper neighboring block, and maxAB is a mode number of an intra prediction mode of the left neighboring block and the It may represent a larger value among the mode numbers of the intra prediction mode of the upper neighboring block.

In addition, when the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are not the same, the encoding apparatus may have a mode number of the intra prediction mode of the left neighboring block than the mode number of the DC intra prediction mode. It is large, and it may be determined whether the mode number of the intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode.

For example, when the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode, and the mode number of the intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode, encoding The apparatus may derive intra prediction mode candidate 0 to intra prediction mode candidate 3 as described later.

mpm[0] = PLANAR_IDX

mpm[1] = leftIntraDir

mpm[2] = aboveIntraDir

mpm[3] = DC_IDX

Here, leftIntraDir may indicate the first candidate intra prediction mode, and aboveIntraDir may indicate the second candidate intra prediction mode.

That is, intra prediction mode candidate 0 of the intra prediction mode candidate list may be derived as a planar intra prediction mode, and intra prediction mode candidate 1 of the intra prediction mode candidate list may be derived as an intra prediction mode of a left neighboring block. , Intra prediction mode candidate 2 of the intra prediction mode candidate list may be derived as an intra prediction mode of an upper neighboring block, and intra prediction mode candidate 3 of the intra prediction mode candidate list may be derived as a DC intra prediction mode. That is, for example, the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block are not the same, and the mode number of the intra prediction mode of the left neighboring block and the mode of the intra prediction mode of the upper neighboring block When the number is greater than the mode number of the DC intra prediction mode, the intra prediction mode candidate list may include the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block as intra prediction mode candidates.

Thereafter, the remaining intra prediction mode candidates (intra prediction mode candidate 4 and intra prediction mode candidate 5) may be derived based on the maxAB and the minAB. Specifically, the remaining intra prediction mode candidates are derived based on a difference between a larger value and a smaller value of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block Can be. Alternatively, the remaining intra prediction mode candidates may be derived based on a difference between the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block.

For example, if the maxAB minAB minAB is less than 63 and greater than 1 (that is, maxAB minAB minAB is one of 2 to 62), the encoding device is Prediction mode candidate 4 and intra prediction mode candidate 5 may be derived.

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

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

That is, the intra prediction mode candidate 4 of the intra prediction mode candidate list is an intra prediction mode having a mode number of 2 + ((maxAB + 61)% 64), that is, a value obtained by adding 61 to the maxAB is subjected to a modular arithmetic operation with 64 It can be derived as an intra prediction mode having a value summed of 2 as a mode number, and the intra prediction mode candidate 5 of the intra prediction mode candidate list is an intra prediction mode having a mode number of 2 + ((maxAB-1)% 64), That is, a value obtained by subtracting 1 from maxAB may be subjected to a modular arithmetic operation by 64, and a value obtained by adding 2 may be derived as an intra prediction mode. Here, maxAB may represent a larger value of a mode number of an intra prediction mode of the left neighboring block and a mode number of an intra prediction mode of the upper neighboring block.

Alternatively, when a value obtained by subtracting the minAB from the maxAB is 63 or more or 1 or less, the encoding apparatus may derive intra prediction mode candidate 4 and intra prediction mode candidate 5 as described later.

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

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

That is, the intra prediction mode candidate 4 of the intra prediction mode candidate list is an intra prediction mode having a mode number of 2 + ((maxAB + 60)% 64), that is, a value obtained by adding 60 to the maxAB is subjected to a modular arithmetic operation by 64. It can be derived as an intra prediction mode having a value summed of 2 as a mode number, and the intra prediction mode candidate 5 of the intra prediction mode candidate list is an intra prediction mode having a mode number of 2 + (maxAB% 64), that is, the maxAB It can be derived as an intra prediction mode having a modulo arithmetic operation of 64 and adding 2 as a mode number. Here, maxAB may represent a larger value of a mode number of an intra prediction mode of the left neighboring block and a mode number of an intra prediction mode of the upper neighboring block.

Meanwhile, the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block of the current block are not the same, or at least one of the mode numbers of the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block is DC If it is smaller than the mode number of the intra prediction mode, the encoding apparatus determines whether the sum of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block is greater than or equal to the mode number of the DC intra prediction mode. I can.

For example, when the sum of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block is greater than or equal to the mode number of the DC intra prediction mode, the encoding apparatus is used as described below. The intra prediction mode candidate list of the current block including candidates may be derived.

-mpm[0] = PLANAR_IDX

-mpm[1] = maxAB

-mpm[2] = DC_IDX

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

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

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

Where maxAB is (leftIntraDir <aboveIntraDir)? It can also be expressed as aboveIntraDir: leftIntraDir. That is, the intra prediction mode candidate 0 of the intra prediction mode candidate list may be derived as a planar intra prediction mode, and the intra prediction mode candidate 1 is maxAB, that is, the intra prediction mode candidate 1 is the intra prediction mode of the left neighboring block. If the mode number is smaller than the mode number of the intra prediction mode of the upper neighboring block, the intra prediction mode of the upper neighboring block and the mode number of the intra prediction mode of the left neighboring block are greater than or equal to the mode number of the intra prediction mode of the upper neighboring block. In this case, it may be derived as an intra prediction mode of the left neighboring block, and intra prediction mode candidate 2 of the intra prediction mode candidate list may be derived as a DC intra prediction mode, and intra prediction mode candidate 3 of the intra prediction mode candidate list Is an intra prediction mode with a mode number of 2 + ((maxAB + 61)% 64), that is, a modulo arithmetic operation of the maxAB plus 61 to 64 and the plus of 2 as an intra prediction mode In the intra prediction mode candidate 4 of the intra prediction mode candidate list, the intra prediction mode having a mode number of 2 + ((maxAB-1)% 64), that is, a value subtracting 1 from the maxAB is modulated by 64 It can be derived as an intra prediction mode having a value obtained by calculating and adding 2 as a mode number, and intra prediction mode candidate 5 of the intra prediction mode candidate list has an intra prediction of 2 + ((maxAB + 60)% 64) A mode, that is, a value obtained by adding 60 to the maxAB may be subjected to a modular arithmetic operation of 64 and an intra prediction mode having a value obtained by adding 2 as a mode number.

Alternatively, for example, when the above-described conditions are not met, the encoding apparatus may derive the intra prediction mode candidate list of the current block including intra prediction mode candidates, as described later.

-mpm[0] = PLANAR_IDX

-mpm[1] = DC_IDX

-mpm[2] = VER_IDX

-mpm[3] = HOR_IDX

-mpm[4] = VER_IDX-4

-mpm[5] = VER_IDX+4

Here, VER_IDX may indicate an intra prediction mode having a mode number of 50 (INTRA_ANGULAR50), HOR_IDX may indicate an intra prediction mode having a mode number of 18 (INTRA_ANGULAR18), and VER_IDX-4 may indicate an intra prediction mode having a mode number of 46 (INTRA_ANGULAR46) may be indicated, and VER_IDX+4 may indicate an intra prediction mode (INTRA_ANGULAR54) having a mode number of 54.

That is, the intra prediction mode candidate 0 of the intra prediction mode candidate list may be derived as a planar intra prediction mode, the intra prediction mode candidate 1 of the intra prediction mode candidate list may be derived as a DC intra prediction mode, and Intra prediction mode candidate 2 of the prediction mode candidate list may be derived as a vertical intra prediction mode (ie, intra prediction mode 50), and intra prediction mode candidate 3 of the intra prediction mode candidate list is a horizontal intra prediction mode (i.e., 18th intra prediction mode), and the intra prediction mode candidate 4 of the intra prediction mode candidate list is an intra prediction mode of a mode number obtained by subtracting 4 from the mode number of the vertical intra prediction mode, that is, the 46th intra prediction mode. The intra prediction mode candidate 5 of the intra prediction mode candidate list may be derived as an intra prediction mode of a mode number obtained by adding 4 to the mode number of the vertical intra prediction mode, that is, the 54th intra prediction mode. That is, for example, if the above-described conditions do not correspond, the intra prediction mode candidate list is a DC intra prediction mode, a 50th intra prediction mode, an 18th intra prediction mode, a 46th intra prediction mode, and a 54th intra prediction. The mode may be included as intra prediction mode candidates.

Meanwhile, the intra prediction mode candidate list generated when the intra prediction type is the first intra prediction type, the intra prediction mode candidate list generated when the intra prediction type is the second intra prediction type, and the intra The intra prediction mode candidate list generated when the prediction type is the third intra prediction type may be the same. That is, the same intra prediction mode candidate list may be configured regardless of the intra prediction type for the current block. The intra prediction mode candidate list may be configured through the same intra prediction mode configuration process regardless of the intra prediction type for the current block. The process of configuring the intra prediction mode may be the same as in one of the above-described embodiments.

The encoding apparatus may determine an intra prediction mode of the current block based on the intra prediction mode candidate list (S1620). Also, for example, the encoding device may generate information on an intra prediction mode based on the intra prediction mode. For example, the encoding apparatus may perform various intra prediction modes to derive an intra prediction mode having an optimal RD cost as an intra prediction mode for the current block. For example, the encoding apparatus may derive an intra prediction mode having an optimal RD cost among intra prediction mode candidates in the intra prediction mode candidate list as an intra prediction mode for the current block. The intra prediction mode may be one of two non-directional intra prediction modes and 65 intra-directional prediction modes. As described above, the two non-directional intra prediction modes may include an intra DC mode and an intra planner mode.

For example, the encoding apparatus may generate an MPM flag indicating whether the determined intra prediction mode is included in the intra prediction mode candidates of the intra prediction mode candidate list. The MPM flag may be indicated as an intra prediction mode candidate flag. When the determined intra prediction mode is included in the intra prediction mode candidates of the intra prediction mode candidate list, the encoding apparatus may generate an MPM index indicating the determined intra prediction mode among the intra prediction mode candidates. The MPM index may be indicated as an intra prediction mode candidate index. If the determined intra prediction mode is not included in the intra prediction mode candidates of the intra prediction mode candidate list, the encoding apparatus re-means indicating the determined intra prediction mode among the remaining intra prediction modes not included in the intra prediction mode candidates. Remaining intra prediction mode information may be generated. Meanwhile, when the determined intra prediction mode is included in the intra prediction mode candidates of the intra prediction mode candidate list, the encoding device may not signal the MPM flag, and the value of the MPM flag may be derived as 1. . The prediction related information on the current block may include the MPM flag, the MPM index, and/or the remaining intra prediction mode information.

The encoding apparatus may derive reference samples of the current block based on the intra prediction type and the intra prediction mode (S1630). For example, when the intra prediction type is derived as the first intra prediction type, the encoding apparatus may select at least one reference sample among reference samples in an intra prediction reference line adjacent to the current block based on the intra prediction mode. It can be derived, and a prediction sample of the current block can be generated based on the reference sample. The reference samples may include an upper left corner reference sample, upper reference samples, and left reference samples of the current block. For example, if the size of the current block is WxH and the x component of the top-left sample position of the current block is xN and the y component is yN, the left reference samples are p[xN-1][ yN] to p[xN-1][2H+yN-1], the upper left corner reference sample is p[xN-1][yN-1], the upper reference sample is p[xN][yN-1] To p[2W+xN-1][yN-1].

Or, for example, when the intra prediction type is derived as the second intra prediction type, the encoding apparatus includes at least one of reference samples in an intra prediction reference line not adjacent to the current block based on the intra prediction mode. A reference sample of may be derived, and a prediction sample of the current block may be generated based on the reference sample. Here, the intra prediction reference line may be a reference line separated by 1, 2, or 3 sample distances from an upper boundary and/or a left boundary of the current block.

Or, for example, when the intra prediction type is derived as the third intra prediction type, the encoding apparatus may determine the ISP partition type of the current block, and divide the current block according to the ISP partition type to serve as a sub Blocks can be derived. The split type may be a horizontal split type or a vertical split type. For example, when the size of the current block is 4x4, the current block may not be divided. Also, for example, when the size of the current block is a 4x8 size and the division type is a horizontal division type, the current block may be divided into two 4x4 sized subblocks. Also, for example, when the size of the current block is a 4x8 size and the division type is a vertical division type, the current block may be divided into two 2x8 sized subblocks. Also, for example, when the size of the current block is 8x4 and the division type is a horizontal division type, the current block may be divided into two 8x2 sized subblocks. Also, for example, when the size of the current block is 8x4 and the division type is a vertical division type, the current block may be divided into two 4x4 sized subblocks. Further, for example, if the size of the current block is WxH size (here, the size of the current block is a size other than 4x8 size, 8x4 size, or 4x4 size), and the division type is a horizontal division type, the current The block may be divided into 4 WxH/4 sized sub-blocks. Also, for example, when the size of the current block is WxH size and the division type is a vertical division type, the current block may be divided into four W/4xH size subblocks. Thereafter, the encoding apparatus may generate a prediction sample by performing intra prediction on each of the subblocks. That is, the encoding apparatus may derive at least one reference sample among reference samples in an intra prediction reference line of each subblock of the current block based on the intra prediction mode, and calculate the prediction sample based on the reference sample. Can be generated. The intra prediction reference line of each sub-block may be a reference line adjacent to each sub-block. Meanwhile, the encoding apparatus may generate and encode an ISP segmentation flag indicating the ISP segmentation type. The prediction related information may include the ISP segmentation flag.

Alternatively, for example, based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples may be derived based on a DC value. For example, if the current block is a square block, and the x and y components of the upper left position of the current block are 0, the DC value is within the intra prediction reference line indicated by the reference line index of the current block. (0, -refIdx-1) coordinate reference sample to (W-1, -refIdx-1) coordinate reference sample and the intra prediction reference line (-refIdx-1, 0) coordinate reference sample to (-refIdx -1, H-1) can be derived based on the reference sample of the coordinates. Alternatively, the DC value is a reference sample of coordinates (-refIdx, -refIdx-1) in an intra prediction reference line indicated by a reference line index of the current block to a reference sample of coordinates (W-1-refIdx, -refIdx-1), and It may be derived based on a reference sample of (-refIdx-1, -refIdx) coordinates or a reference sample of (-refIdx-1, H-1-refIdx) coordinates in the intra prediction reference line. Here, W and H may indicate the width and height of the current block, and refIdx may indicate a value of the reference line index.

Alternatively, for example, based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples may be derived based on a DC value. For example, the current block is a non-square block whose width is greater than its height, x and y components of the upper left position of the current block are 0, and the DC value is a reference line index of the current block It may be derived based on a reference sample of (0, -refIdx-1) coordinates or a reference sample of (W-1, -refIdx-1) coordinates in the prediction reference line indicated by. Alternatively, the DC value is based on a reference sample of (-refIdx, -refIdx-1) coordinates or a reference sample of (W-1-refIdx, -refIdx-1) coordinates in the prediction reference line indicated by the reference line index of the current block. It can also be derived as. For example, if the current block is a non-square block whose height is greater than the width, and the x and y components of the upper left position of the current block are 0, the DC value is a reference line of the current block It may be derived based on a reference sample of the coordinates of (-refIdx-1, 0) in the prediction reference line indicated by the index or a reference sample of the coordinates of (-refIdx-1, H-1). Alternatively, the DC value is based on a reference sample of (-refIdx-1, -refIdx) coordinates or a reference sample of (-refIdx-1, H-1-refIdx) coordinates in the prediction reference line indicated by the reference line index of the current block. It can also be derived as. Here, W and H may indicate the width and height of the current block, and refIdx may indicate a value of the reference line index.

Alternatively, for example, based on that the intra prediction mode of the current block is a planar intra prediction mode, the prediction samples may be derived based on reference samples. For example, if the current block is a square block, and the x and y components of the upper left position of the current block are 0, the reference samples are an intra prediction reference line indicated by a reference line index of the current block. A reference sample of the (-refIdx-1, H) coordinate and a reference sample of the (W, -refIdx-1) coordinate of the intra prediction reference line may be included. Alternatively, the reference samples are reference samples of coordinates in the intra prediction reference line (-refIdx-1, H-refIdx) indicated by the reference line index of the current block and in the intra prediction reference line (W-refIdx, -refIdx-1) It may also include a reference sample of the coordinates. Here, W and H may indicate the width and height of the current block, and refIdx may indicate a value of the reference line index.

The encoding apparatus may derive prediction samples of the current block based on the reference samples (S1640). For example, when the intra prediction mode of the current block is a DC intra prediction mode, the encoding apparatus may derive a DC value based on reference samples and may derive the prediction samples based on the DC value. Or, for example, when the intra prediction mode of the current block is a planar intra prediction mode, the encoding apparatus may derive prediction samples by performing interpolation based on reference samples. Alternatively, for example, when the intra prediction mode of the current block is a directional intra prediction mode, the encoding apparatus may derive prediction samples based on reference samples indicated by the directional intra prediction mode.

The encoding apparatus may derive residual samples of the current block based on the prediction samples (S1650). Also, for example, the encoding device may generate information on the residual samples. For example, the encoding apparatus may derive residual samples for the current block based on original samples and predicted samples for the current block, or a residual sample for the current block based on the residual samples. You can create information about them. Here, the information on the residual samples may be expressed as information on the residual or information on the residual.

The encoding apparatus may encode image information including prediction related information including information about an intra prediction type, information about an intra prediction mode, and information about residual samples (S1660). For example, the encoding device may encode image information including the prediction-related information on the current block, and may output it in the form of a bitstream. The prediction related information may include information about the intra prediction type, information about the intra prediction mode, and/or information about residual samples. For example, the information on the intra prediction type may include the reference line index, the ISP flag, and/or the ISP index. In addition, for example, the information on the intra prediction mode may include the MPM flag, the MPM index, and/or the remaining intra prediction mode information. Also, for example, the information on the residual samples may include a transform coefficient on the residual sample.

Meanwhile, the bitstream may be transmitted to a decoding device through a network or a (digital) storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

For example, the encoding apparatus may generate a bitstream or encoded information by encoding image information including all or part of the above-described information (or syntax elements). Alternatively, it can be output in the form of a bitstream. In addition, the bitstream or encoded information may be transmitted to a decoding device through a network or a storage medium. Alternatively, the bitstream or the encoded information may be stored in a computer-readable storage medium, and the bitstream or the encoded information may be generated by the above-described video encoding method.

The method disclosed in FIG. 18 may be performed by the decoding apparatus disclosed in FIG. 3 or 19. Specifically, for example, S1800 of FIG. 18 may be performed by the entropy decoding unit 310 of the decoding apparatus in FIG. 19, and S1810 to S1850 of FIG. 18 are predictive units 330 of the decoding apparatus in FIG. 19. It can be done by Further, although not shown in FIG. 18, prediction related information or residual information may be derived from the bitstream by the entropy decoding unit 310 of the decoding device in FIG. 19, and the residual processing unit 320 of the decoding device Residual samples may be derived from residual information according to, and prediction samples may be derived from prediction-related information by the prediction unit 330 of the decoding device, and residual samples may be derived from the addition unit 340 of the decoding device. A reconstructed block or a reconstructed picture may be derived from dual samples or prediction samples. The method disclosed in FIG. 18 may include the embodiments described above in this document.

The decoding apparatus may obtain prediction related information on the current block from the bitstream (S1800). For example, the decoding apparatus may obtain image information including prediction related information from the bitstream. For example, the decoding apparatus may receive a bitstream, and may obtain the image information by decoding or parsing the bitstream. For example, the prediction related information may include information about an intra prediction type, information about an intra prediction mode, and/or information about residual samples.

The decoding apparatus may derive an intra prediction type for a current block from among intra prediction types based on the prediction related information (S1810). For example, the decoding apparatus may derive the intra prediction type for the current block based on the prediction related information. Alternatively, for example, the decoding apparatus may derive the intra prediction type for the current block based on information on the intra prediction type. Here, the intra prediction types are a first intra prediction type using an intra prediction reference line adjacent to the current block, a second intra prediction type using an intra prediction reference line not adjacent to the current block, and Intra Sub- Partitions mode) may be applied to the third intra prediction type. The first intra prediction type may indicate the above-described general intra prediction, the second intra prediction type may indicate the above-described MRL, and the third intra prediction type may indicate the above-described ISP.

For example, the decoding apparatus may derive the intra prediction type for the current block based on the information on the intra prediction type shown in at least some of the above tables. For example, the decoding apparatus may determine whether the intra prediction type for the current block is the second intra prediction type based on the reference line index of the current block. The information on the intra prediction type may include the reference line index. The reference line index may indicate an intra prediction reference line of the current block. For example, when the value of the reference line index is 0, the reference line index may indicate a reference line adjacent to the upper boundary and/or the left boundary of the current block, and when the value of the reference line index is 1 , The reference line index may indicate a reference line separated by 1 sample distance from an upper boundary and/or a left boundary of the current block, and when the value of the reference line index is 2, the reference line index is It may refer to a reference line that is 2 samples away from the upper boundary and/or the left boundary, and when the value of the reference line index is 3, the reference line index is 3 samples from the upper boundary and/or left boundary of the current block. It can point to a reference line a distance apart. When the reference line index indicates a reference line adjacent to the current block, the decoding apparatus may derive the reference line adjacent to the current block as an intra prediction reference line of the current block, and the intra prediction for the current block It may be determined that the type is not the second intra prediction type. In addition, when the reference line index indicates a reference line not adjacent to the current block, the decoding apparatus may derive the reference line not adjacent to the current block as an intra prediction reference line of the current block. 2 An intra prediction type may be derived as the intra prediction type for the current block. Here, the reference line not adjacent to the current block may be a reference line separated by a distance of 1, 2 or 3 samples from the upper boundary and/or the left boundary of the current block.

In addition, when the reference line index indicates a reference line adjacent to the current block, that is, when the intra prediction type for the current block is not the second intra prediction type, the decoding apparatus may perform an Intra Sub-Partitions mode (ISP). ) It may be determined whether the intra prediction type for the current block is the third intra prediction type based on a flag. The information on the intra prediction type may include the ISP flag. The ISP flag may indicate whether a third intra prediction type to which the ISP is applied is applied to the current block. That is, the ISP flag may indicate whether the ISP is applied to the current block. For example, when the value of the IPS flag is 1, the ISP flag may indicate that the third intra prediction type is applied to the current block. When the value of the IPS flag is 0, the ISP flag is It may be indicated that the third intra prediction type is not applied to the current block. When the ISP flag indicates that the third intra prediction type is applied, the decoding apparatus may derive the third intra prediction type as the intra prediction type for the current block, and the ISP flag is the third intra prediction type. If it is indicated that the type is not applied, the decoding apparatus may derive the first intra prediction type as the intra prediction type for the current block.

The decoding apparatus constructs an intra prediction mode candidate list of the current block based on intra prediction modes of neighboring blocks of the current block (S1820). For example, the decoding apparatus may configure an intra prediction mode candidate list based on at least some of the above tables, and the intra prediction mode candidate list may represent the above-described MPM (most probable mode) list.

For example, the decoding apparatus may configure the intra prediction mode candidate list based on the first candidate intra prediction mode and the second candidate intra prediction mode. The decoding apparatus includes whether the first candidate intra prediction mode and the second candidate intra prediction mode are the same and/or the mode number of the first candidate intra prediction mode and/or the mode number of the second candidate intra prediction mode is DC The intra prediction mode candidate list may be configured based on whether it is greater than the intra prediction mode. Here, the first candidate intra prediction mode may be derived based on an intra prediction mode of a left neighboring block of the current block, and the second candidate intra prediction mode based on an intra prediction mode of an upper neighboring block of the current block Can be derived. For example, an intra prediction mode of an adjacent block to the left of the current block may be derived as the first candidate intra prediction mode, and an intra prediction mode of an upper adjacent block of the current block is derived as the second candidate intra prediction mode Can be. Here, the first candidate intra prediction mode may be referred to as a first intra prediction mode, and the second candidate intra prediction mode may be referred to as a second intra prediction mode. That is, the intra prediction mode candidate list may be configured based on a first intra prediction mode for a left neighboring block of the current block and a second intra prediction mode for an upper neighboring block of the current block.

For example, the decoding apparatus may configure the intra prediction mode candidate list based on the intra prediction mode of the neighboring block on the left side of the current block and the intra prediction mode of the neighboring block above the current block. The decoding apparatus may determine whether the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are the same, and the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode. have. The decoding apparatus determines whether the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are the same and/or whether the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode. The intra prediction mode candidate list may be configured based on whether or not.

When the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are the same, and the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode, the decoding apparatus will be described later. As described above, the intra prediction mode candidate list of the current block including intra prediction mode candidates may be derived.

-mpm[0] = PLANAR_IDX

-mpm[1] = leftIntraDir

-mpm[2] = 2 + ((leftIntraDir + 61)% 64)

-mpm[3] = 2 + ((leftIntraDir-1)% 64)

-mpm[4] = DC_IDX

-mpm[5] = 2 + ((leftIntraDir + 60)% 64)

On the other hand, when the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are not the same, for example, the decoding apparatus may determine the mode number of the intra prediction intra prediction mode of the left neighboring block and the upper side. Intra prediction of the neighboring block It may be determined whether at least one of the mode numbers of the intra prediction mode is greater than the mode number of the DC intra prediction mode. When at least one of the mode number of the intra prediction intra prediction mode of the left neighboring block and the mode number of the intra prediction intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode, variable minAB and variable maxAB Can be derived as follows.

-minAB = Min(candIntraPredModeA, candIntraPredModeB)

-maxAB = Max(candIntraPredModeA, candIntraPredModeB)

In addition, when the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block are not the same, the decoding apparatus has a mode number of the intra prediction mode of the left neighboring block than the mode number of the DC intra prediction mode. It may be determined whether the mode number of the intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode.

For example, when the mode number of the intra prediction mode of the left neighboring block is greater than the mode number of the DC intra prediction mode, and the mode number of the intra prediction mode of the upper neighboring block is greater than the mode number of the DC intra prediction mode, decoding The apparatus may derive intra prediction mode candidate 0 to intra prediction mode candidate 3 as described later.

mpm[0] = PLANAR_IDX

mpm[1] = leftIntraDir

mpm[2] = aboveIntraDir

mpm[3] = DC_IDX

For example, if the maxAB minAB minAB is less than 63 and greater than 1 (that is, maxAB minAB minAB is one of 2 to 62), the decoding device will be Prediction mode candidate 4 and intra prediction mode candidate 5 may be derived.

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

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

Alternatively, when a value obtained by subtracting the minAB from the maxAB is 63 or more or 1 or less, the decoding apparatus may derive the intra prediction mode candidate 4 and the intra prediction mode candidate 5 as described later.

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

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

Meanwhile, the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block of the current block are not the same, or at least one of the mode numbers of the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block is DC If it is smaller than the mode number of the intra prediction mode, the decoding apparatus determines whether the sum of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block is greater than or equal to the mode number of the DC intra prediction mode. I can.

For example, when the sum of the mode number of the intra prediction mode of the left neighboring block and the mode number of the intra prediction mode of the upper neighboring block is greater than or equal to the mode number of the DC intra prediction mode, the decoding apparatus may perform an intra prediction mode as described later. The intra prediction mode candidate list of the current block including candidates may be derived.

-mpm[0] = PLANAR_IDX

-mpm[1] = maxAB

-mpm[2] = DC_IDX

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

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

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

Where maxAB is (leftIntraDir <aboveIntraDir)? It can also be expressed as aboveIntraDir: leftIntraDir. That is, the intra prediction mode candidate 0 of the intra prediction mode candidate list may be derived as a planar intra prediction mode, and the intra prediction mode candidate 1 is maxAB, that is, the intra prediction mode candidate 1 is the intra prediction mode of the left neighboring block. If the mode number is smaller than the mode number of the intra prediction mode of the upper neighboring block, the intra prediction mode of the upper neighboring block and the mode number of the intra prediction mode of the left neighboring block are greater than or equal to the mode number of the intra prediction mode of the upper neighboring block. In this case, it may be derived as an intra prediction mode of the left neighboring block, and intra prediction mode candidate 2 of the intra prediction mode candidate list may be derived as a DC intra prediction mode, and intra prediction mode candidate 3 of the intra prediction mode candidate list Is an intra prediction mode with a mode number of 2 + ((maxAB + 61)% 64), that is, a modulo arithmetic operation of the maxAB plus 61 to 64 and the plus of 2 as an intra prediction mode The intra prediction mode candidate 4 of the intra prediction mode candidate list is an intra prediction mode having a mode number of 2 + ((maxAB-1)% 64), that is, a value obtained by subtracting 1 from the maxAB is modulated by 64 It can be derived as an intra prediction mode having a value obtained by calculating and adding 2 as a mode number, and intra prediction mode candidate 5 of the intra prediction mode candidate list has an intra prediction of 2 + ((maxAB + 60)% 64) A mode, that is, a value obtained by adding 60 to maxAB may be subjected to a modular arithmetic operation to 64 and an intra prediction mode having a value obtained by adding 2 as a mode number.

Alternatively, for example, if the above-described conditions are not met, the decoding apparatus may derive the intra prediction mode candidate list of the current block including intra prediction mode candidates, as described later.

-mpm[0] = PLANAR_IDX

-mpm[1] = DC_IDX

-mpm[2] = VER_IDX

-mpm[3] = HOR_IDX

-mpm[4] = VER_IDX-4

-mpm[5] = VER_IDX+4

The decoding apparatus derives an intra prediction mode of the current block based on the intra prediction mode candidate list (S1830). For example, the decoding apparatus may derive an MPM flag for the current block. The information on the intra prediction mode may include the MPM flag. For example, the decoding apparatus may receive information on an intra prediction mode for the current block, and the information on the intra prediction mode may include an MPM flag for the current block. Alternatively, the information on the intra prediction mode may not include the MPM flag, and in this case, the decoding apparatus may derive the value of the MPM flag as 1. The MPM flag may indicate whether the intra prediction mode of the current block is one of intra prediction mode candidates of the intra prediction mode candidate list. The MPM flag may be indicated as an intra prediction mode candidate flag.

When the value of the MPM flag is 1, the decoding apparatus may derive an intra prediction mode candidate indicated by an MPM index among intra prediction mode candidates in the intra prediction mode candidate list as the intra prediction mode for the current block. The prediction related information may include the MPM index. The MPM index may be signaled in the form of an mpm_idx or intra_luma_mpm_idx syntax element. The MPM index may be indicated as an intra prediction mode candidate index.

When the value of the MPM flag is 0, the decoding apparatus may derive an intra prediction mode indicated by remaining intra prediction mode information among the remaining intra prediction modes as the intra prediction mode for the current block. The remaining intra prediction modes may represent remaining intra prediction modes that are not included in the intra prediction mode candidates of the intra prediction mode candidate list. The prediction-related information may include the remaining intra prediction mode information. The remaining intra prediction mode information may be signaled in the form of rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element.

The decoding apparatus may derive reference samples of the current block based on the intra prediction type and the intra prediction mode (S1840). For example, when the intra prediction type is derived as the first intra prediction type, the decoding apparatus selects at least one reference sample among reference samples in an intra prediction reference line adjacent to the current block based on the intra prediction mode. Can be derived, and a prediction sample of the current block can be generated based on the reference sample. The reference samples may include an upper left corner reference sample, upper reference samples, and left reference samples of the current block. For example, if the size of the current block is WxH and the x component of the top-left sample position of the current block is xN and the y component is yN, the left reference samples are p[xN-1][ yN] to p[xN-1][2H+yN-1], the upper left corner reference sample is p[xN-1][yN-1], the upper reference sample is p[xN][yN-1] To p[2W+xN-1][yN-1].

Or, for example, when the intra prediction type is derived as the second intra prediction type, the decoding apparatus includes at least one of reference samples in an intra prediction reference line not adjacent to the current block based on the intra prediction mode. A reference sample of may be derived, and a prediction sample of the current block may be generated based on the reference sample. Here, the intra prediction reference line may be a reference line separated by 1, 2, or 3 sample distances from an upper boundary and/or a left boundary of the current block.

Or, for example, when the intra prediction type is derived as the third intra prediction type, the decoding apparatus may derive the ISP partition type of the current block based on the ISP partition flag indicating the ISP partition type, Subblocks may be derived by dividing the current block according to the ISP division type. The split type may be a horizontal split type or a vertical split type. For example, when the size of the current block is 4x4, the current block may not be divided. Also, for example, when the size of the current block is a 4x8 size and the division type is a horizontal division type, the current block may be divided into two 4x4 sized subblocks. Also, for example, when the size of the current block is a 4x8 size and the division type is a vertical division type, the current block may be divided into two 2x8 sized subblocks. Also, for example, when the size of the current block is 8x4 and the division type is a horizontal division type, the current block may be divided into two 8x2 sized subblocks. Also, for example, when the size of the current block is 8x4 and the division type is a vertical division type, the current block may be divided into two 4x4 sized subblocks. Further, for example, if the size of the current block is WxH size (here, the size of the current block is a size other than 4x8 size, 8x4 size, or 4x4 size), and the division type is a horizontal division type, the current The block may be divided into 4 WxH/4 sized sub-blocks. Also, for example, when the size of the current block is WxH size and the division type is a vertical division type, the current block may be divided into four W/4xH size subblocks. Thereafter, the decoding apparatus may generate a prediction sample by performing intra prediction on each of the subblocks. That is, the decoding apparatus may derive at least one reference sample among reference samples in an intra prediction reference line of each subblock of the current block based on the intra prediction mode, and calculate the prediction sample based on the reference sample. Can be generated. The intra prediction reference line of each sub-block may be a reference line adjacent to each sub-block.

The decoding apparatus may generate prediction samples of the current block based on the reference samples (S1850). For example, when the intra prediction mode of the current block is a DC intra prediction mode, the decoding apparatus may derive a DC value based on reference samples and may derive the prediction samples based on the DC value. Or, for example, when the intra prediction mode of the current block is a planar intra prediction mode, the decoding apparatus may derive prediction samples by performing interpolation based on reference samples. Alternatively, for example, when the intra prediction mode of the current block is a directional intra prediction mode, the decoding apparatus may derive prediction samples based on reference samples indicated by the directional intra prediction mode.

Meanwhile, although not shown in the drawing, the decoding apparatus may directly use the prediction samples as reconstructed samples according to a prediction mode, or may generate reconstructed samples by adding residual samples to the prediction samples. When there are residual samples for the current block, the decoding apparatus may receive residual information for the current block, and the residual information may include a transform coefficient for the residual sample. The decoding apparatus may derive the residual samples (or residual sample array) for the current block based on the residual information. For example, the residual information may be expressed as information about residual samples or residual related information. For example, the prediction related information may include information on residual samples. The decoding apparatus may generate reconstructed samples based on the prediction samples and the residual samples, and derive a reconstructed block or a reconstructed picture based on the reconstructed samples. Thereafter, as described above, the decoding apparatus may apply an in-loop filtering procedure such as deblocking filtering and/or SAO procedure to the reconstructed picture in order to improve subjective/objective image quality as needed.

For example, the decoding apparatus may obtain image information including all or part of the above-described information (or syntax elements) by decoding the bitstream or the encoded information. Also, the bitstream or encoded information may be stored in a computer-readable storage medium, and may cause the above-described decoding method to be performed.

According to the above-described document, it is possible to reduce hardware and software implementation complexity by using a unified intra prediction mode list construction process for intra prediction types.

In addition, according to this document, the coding efficiency of intra prediction can be improved by reducing the dependency according to the intra prediction type by using a unified intra prediction mode list construction process for intra prediction types.

Further, according to this document, a reference sample used when MRL is applied and an intra prediction mode is derived as a DC intra prediction mode can be derived based on a reference picture index, thereby improving coding efficiency of intra prediction.

In the above-described embodiment, the methods are described on the basis of a flowchart as a series of steps or blocks, but this document is not limited to the order of the steps, and certain steps may occur in a different order or concurrently with the steps described above. have. Further, those skilled in the art will appreciate that the steps shown in the flowchart are not exclusive, other steps may be included, or one or more steps in the flowchart may be deleted without affecting the scope of this document.

The embodiments described in this document may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units illustrated in each drawing may be implemented and executed on a computer, processor, microprocessor, controller, or chip. In this case, information for implementation (ex. information on instructions) or an algorithm may be stored in a digital storage medium.

In addition, the decoding device and the encoding device to which the embodiments of the present document are applied include a multimedia broadcasting transmission/reception device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video chat device, a real-time communication device such as video communication. , Mobile streaming device, storage medium, camcorder, video-on-demand (VoD) service provider, OTT video (Over the top video) device, Internet streaming service provider, three-dimensional (3D) video device, video telephony video device, vehicle It may be included in a terminal (ex. a vehicle terminal, an airplane terminal, a ship terminal, etc.) and a medical video device, and may be used to process a video signal or a data signal. For example, an OTT video (Over the top video) device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smartphone, a tablet PC, and a digital video recorder (DVR).

Further, the processing method to which the embodiments of the present document are applied may be produced in the form of a program executed by a computer, and may be stored in a computer-readable recording medium. Multimedia data having the data structure according to this document can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all kinds of storage devices and distributed storage devices in which computer-readable data is stored. The computer-readable recording medium includes, for example, Blu-ray disk (BD), universal serial bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical It may include a data storage device. Further, the computer-readable recording medium includes media implemented in the form of a carrier wave (for example, transmission through the Internet). In addition, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or transmitted through a wired or wireless communication network.

Further, an embodiment of this document may be implemented as a computer program product using a program code, and the program code may be executed in a computer according to the embodiment of this document. The program code may be stored on a carrier readable by a computer.

The content streaming system to which the embodiments of this document are applied may largely include an encoding server, a streaming server, a web server, a media storage device, a user device, and a multimedia input device.

The encoding server serves to generate a bitstream by compressing content input from multimedia input devices such as smartphones, cameras, camcorders, etc. into digital data, and transmits it to the streaming server. As another example, when multimedia input devices such as smartphones, cameras, camcorders, etc. directly generate bitstreams, the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstream generation method to which the embodiments of the present document are applied, and the streaming server may temporarily store the bitstream while transmitting or receiving the bitstream.

The streaming server transmits multimedia data to a user device based on a user request through a web server, and the web server serves as an intermediary for notifying the user of a service. When a user requests a desired service from the web server, the web server transmits it to the streaming server, and the streaming server transmits multimedia data to the user. In this case, the content streaming system may include a separate control server, and in this case, the control server serves to control commands/responses between devices in the content streaming system.

The streaming server may receive content from a media storage and/or encoding server. For example, when content is received from the encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined time.

Examples of the user device include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, and Tablet PC, ultrabook, wearable device, for example, smartwatch, smart glass, head mounted display (HMD)), digital TV, desktop There may be computers, digital signage, etc. Each server in the content streaming system may be operated as a distributed server, and in this case, data received from each server may be distributedly processed.

The claims set forth herein may be combined in a variety of ways. For example, the technical features of the method claims of the present specification may be combined to be implemented as a device, and the technical features of the device claims of the present specification may be combined to be implemented by a method. In addition, the technical characteristics of the method claim of the present specification and the technical characteristics of the device claim may be combined to be implemented as a device, and the technical characteristics of the method claim of the present specification and the technical characteristics of the device claim may be combined to be implemented by a method.

Claims

In the video decoding method performed by the decoding device,

Obtaining prediction related information for the current block from the bitstream;

Deriving an intra prediction type for the current block from among intra prediction types based on the prediction related information;

Constructing an intra prediction mode candidate list of the current block based on intra prediction modes of neighboring blocks of the current block;

Deriving an intra prediction mode of the current block based on the intra prediction mode candidate list;

Deriving reference samples of the current block based on the intra prediction type and the intra prediction mode; And

Generating prediction samples of the current block based on the reference samples,

The intra prediction types are a first intra prediction type using an intra prediction reference line adjacent to the current block, a second intra prediction type using an intra prediction reference line not adjacent to the current block, and an Intra Sub-Partitions mode (ISP). ) Includes a third intra prediction type to which is applied,

The intra prediction mode candidate list configured on the basis that the intra prediction type is the first intra prediction type, the intra prediction mode candidate list configured on the basis that the intra prediction type is the second intra prediction type, and the intra prediction type The intra prediction mode candidate list configured on the basis that this is the third intra prediction type is the same,

The neighboring blocks include a left neighboring block and an upper neighboring block of the current block,

The intra prediction mode candidate list is configured based on a first intra prediction mode for the left neighboring block and a second intra prediction mode for the upper neighboring block,

The first intra prediction mode or the second intra prediction mode for a neighboring block to which a CIIP (Combined Inter and Intra Prediction) mode is applied among the left neighboring blocks or the upper neighboring blocks is determined as a planar mode. That, video decoding method.
The method of claim 1,

The first intra prediction mode and the second intra prediction mode are the same, and the mode number of the first intra prediction mode is greater than the mode number of the DC intra prediction mode,

The intra prediction mode candidate list includes the first intra prediction mode, an intra prediction mode having a mode number of 2 + ((candIntraPredModeA + 61)% 64), an intra prediction mode having a mode number of 2 + ((candIntraPredModeA-1)% 64) An intra prediction mode having a mode and a mode number of 2 + ((candIntraPredModeA + 60)% 64) is included as intra prediction mode candidates, and the candIntraPredModeA indicates the mode number of the first intra prediction mode. Decoding method.
The method of claim 1,

The first intra prediction mode and the second intra prediction mode are not the same, and the mode number of the first intra prediction mode and the mode number of the second intra prediction mode are greater than the mode number of the DC intra prediction mode. ,

The intra prediction mode candidate list includes the first intra prediction mode and the second intra prediction mode as intra prediction mode candidates,

The remaining intra prediction mode candidates of the intra prediction mode candidate list are derived based on a difference between the mode number of the first intra prediction mode and the mode number of the second intra prediction mode.
The method of claim 1,

Based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples are derived based on a DC value,

The DC value is a reference sample of (0, -refIdx-1) coordinates in an intra prediction reference line indicated by a reference line index of the current block to a reference sample of coordinates (W-1, -refIdx-1) and the intra prediction reference It is derived based on a reference sample of (-refIdx-1, 0) coordinates or a reference sample of (-refIdx-1, H-1) coordinates in the line,

The current block is a square block, x and y components of the upper left position of the current block are 0, the W and H represent the width and height of the current block, and the refIdx is the reference line index Characterized in that representing the value of, video decoding method.
The method of claim 1,

Based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples are derived based on a DC value,

The DC value is derived based on a reference sample of (0, -refIdx-1) coordinates or a reference sample of (W-1, -refIdx-1) coordinates in the prediction reference line indicated by the reference line index of the current block,

The current block is a non-square block whose width is greater than the height, x and y components of the upper left position of the current block are 0, and W and H represent the width and height of the current block. , Wherein refIdx represents a value of the reference line index.
The method of claim 1,

Based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples are derived based on a DC value,

The DC value is derived based on a reference sample of coordinates (-refIdx-1, 0) or a reference sample of coordinates (-refIdx-1, H-1) in a prediction reference line indicated by the reference line index of the current block,

The current block is a non-square block whose height is greater than the width, x and y components of the upper left position of the current block are 0, and W and H represent the width and height of the current block. , Wherein refIdx represents a value of the reference line index.
The method of claim 1,

Based on that the intra prediction mode of the current block is a planar intra prediction mode, the reference samples are reference samples of coordinates in the intra prediction reference line (-refIdx-1, H) indicated by the reference line index of the current block and the intra prediction mode. Contains a reference sample of the (W, -refIdx-1) coordinates in the prediction line,

The current block is a square block, x and y components of the upper left position of the current block are 0, the W and H represent the width and height of the current block, and the refIdx is the reference line index Characterized in that representing the value of, video decoding method.
The method of claim 1,

Based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples are derived based on a DC value,

The DC value is from a reference sample of coordinates (-refIdx, -refIdx-1) in an intra prediction reference line indicated by a reference line index of the current block to a reference sample of coordinates of (W-1-refIdx, -refIdx-1) and the It is derived based on a reference sample of (-refIdx-1, -refIdx) coordinates or a reference sample of (-refIdx-1, H-1-refIdx) coordinates in the intra prediction reference line,

The current block is a square block, x and y components of the upper left position of the current block are 0, the W and H represent the width and height of the current block, and the refIdx is the reference line index Characterized in that representing the value of, video decoding method.
The method of claim 1,

Based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples are derived based on a DC value,

The DC value is based on a reference sample of (-refIdx, -refIdx-1) coordinates in a prediction reference line indicated by the reference line index of the current block to a reference sample of coordinates (W-1-refIdx, -refIdx-1) Derived,

The current block is a non-square block whose width is greater than the height, x and y components of the upper left position of the current block are 0, and W and H represent the width and height of the current block. , Wherein refIdx represents a value of the reference line index.
The method of claim 1,

Based on that the intra prediction mode of the current block is a DC intra prediction mode, the prediction samples are derived based on a DC value,

The DC value is based on a reference sample of (-refIdx-1, -refIdx) coordinates or a reference sample of (-refIdx-1, H-1-refIdx) coordinates in the prediction reference line indicated by the reference line index of the current block. Derived,

The current block is a non-square block whose height is greater than the width, x and y components of the upper left position of the current block are 0, and W and H represent the width and height of the current block. , Wherein refIdx represents a value of the reference line index.
The method of claim 1,

Based on that the intra prediction mode of the current block is a planar intra prediction mode, the reference samples are reference samples of coordinates (-refIdx-1, H-refIdx) in the intra prediction reference line indicated by the reference line index of the current block, and Including a reference sample of the coordinates (W-refIdx, -refIdx-1) in the intra prediction reference line,

The current block is a square block, x and y components of the upper left position of the current block are 0, the W and H represent the width and height of the current block, and the refIdx is the reference line index Characterized in that representing the value of, video decoding method.
In the video encoding method performed by the encoding device,

Determining an intra prediction type for a current block from among intra prediction types, and generating information on an intra prediction type based on the intra prediction type;

Constructing an intra prediction mode candidate list of the current block based on intra prediction modes of neighboring blocks of the current block;

Determining an intra prediction mode of the current block based on the intra prediction mode candidate list, and generating information on an intra prediction mode based on the intra prediction mode;

Deriving reference samples of the current block based on the intra prediction type and the intra prediction mode;

Deriving prediction samples of the current block based on the reference samples;

Deriving residual samples of the current block based on the prediction samples, and generating information on the residual samples; And

Encoding image information including prediction-related information including information on the intra prediction type, information on the intra prediction mode, and information on the residual samples,

The intra prediction types are a first intra prediction type using an intra prediction reference line adjacent to the current block, a second intra prediction type using an intra prediction reference line not adjacent to the current block, and an Intra Sub-Partitions mode (ISP). ) Includes a third intra prediction type to which is applied,

The intra prediction mode candidate list configured on the basis that the intra prediction type is the first intra prediction type, the intra prediction mode candidate list configured on the basis that the intra prediction type is the second intra prediction type, and the intra prediction type The intra prediction mode candidate list configured on the basis that this is the third intra prediction type is the same,

The neighboring blocks include a left neighboring block and an upper neighboring block of the current block,

The intra prediction mode candidate list is configured based on a first intra prediction mode for the left neighboring block and a second intra prediction mode for the upper neighboring block,

The first intra prediction mode or the second intra prediction mode for a neighboring block to which a CIIP (Combined Inter and Intra Prediction) mode is applied among the left neighboring blocks or the upper neighboring blocks is determined as a planar mode. That, video encoding method.
The method of claim 12,

The first intra prediction mode and the second intra prediction mode are the same, and the mode number of the first intra prediction mode is greater than the mode number of the DC intra prediction mode,

The intra prediction mode candidate list includes the first intra prediction mode, an intra prediction mode having a mode number of 2 + ((candIntraPredModeA + 61)% 64), an intra prediction mode having a mode number of 2 + ((candIntraPredModeA-1)% 64) An intra prediction mode having a mode and a mode number of 2 + ((candIntraPredModeA + 60)% 64) is included as intra prediction mode candidates, and the candIntraPredModeA indicates the mode number of the first intra prediction mode. Encoding method.
The method of claim 12,

The first intra prediction mode and the second intra prediction mode are not the same, and the mode number of the first intra prediction mode and the mode number of the second intra prediction mode are greater than the mode number of the DC intra prediction mode,

The intra prediction mode candidate list includes the first intra prediction mode and the second intra prediction mode as intra prediction mode candidates,

The remaining intra prediction mode candidates of the intra prediction mode candidate list are derived based on a difference between the mode number of the first intra prediction mode and the mode number of the second intra prediction mode.
A computer-readable digital storage medium storing encoded information causing an image decoding apparatus to perform an image decoding method, the image decoding method comprising:

Obtaining prediction related information for a current block from the encoded information;

Deriving an intra prediction type for the current block from among intra prediction types based on the prediction related information;

Constructing an intra prediction mode candidate list of the current block based on intra prediction modes of neighboring blocks of the current block;

Deriving an intra prediction mode of the current block based on the intra prediction mode candidate list;

Deriving reference samples of the current block based on the intra prediction type and the intra prediction mode; And

Generating prediction samples of the current block based on the reference samples,

The intra prediction types are a first intra prediction type using an intra prediction reference line adjacent to the current block, a second intra prediction type using an intra prediction reference line not adjacent to the current block, and an Intra Sub-Partitions mode (ISP). ) Includes a third intra prediction type to which is applied,

The intra prediction mode candidate list configured on the basis that the intra prediction type is the first intra prediction type, the intra prediction mode candidate list configured on the basis that the intra prediction type is the second intra prediction type, and the intra prediction type The intra prediction mode candidate list configured on the basis that this is the third intra prediction type is the same,

The neighboring blocks include a left neighboring block and an upper neighboring block of the current block,

The intra prediction mode candidate list is configured based on a first intra prediction mode for the left neighboring block and a second intra prediction mode for the upper neighboring block,

The first intra prediction mode or the second intra prediction mode for a neighboring block to which a CIIP (Combined Inter and Intra Prediction) mode is applied among the left neighboring blocks or the upper neighboring blocks is determined as a planar mode. A computer-readable digital storage medium.