Image decoding methods, image encoding methods, non-transferable computer-readable digital storage media, and data transmission methods for image information.

Abstract

The invention relates to a method for decoding images, a method for encoding images, a digital storage medium readable by a non-transferable computer, and a method for transmitting data for image information. The method for decoding images under the invention comprises the following steps: obtaining the internal MIP syntax element for the first target block; deriving the value of the internal MIP syntax element; setting a variable MIP flag for a specific predefined area, which is the same as the area of ​​the first target block, on the basis of the value of the internal MIP syntax element; deriving the internal prediction mode of the second target block on the basis of the variable MIP flag; and deriving the prediction pattern of the second target block on the basis of the internal prediction mode of the second target block.

Description

Video coding method and device thereof

[0001] This document relates to image coding technology, and more specifically, to an image coding method and device based on intra prediction in an image coding system.

[0002] Demand for high-resolution, high-quality video, such as 4K or 8K Ultra High Definition (UHD) video, is growing across a variety of fields. As video data becomes higher-resolution and higher-quality, the amount of information or bits transmitted increases relative to conventional video data. Therefore, when transmitting video data using existing media, such as wired or wireless broadband lines, or storing video data using existing storage media, transmission and storage costs increase.

[0003] In addition, interest in and demand for immersive media such as VR (Virtual Reality), AR (Artificial Reality) content and holograms have been increasing recently, and broadcasting of images / videos with different image characteristics from reality images, such as game images, is increasing.

[0004] Accordingly, a highly efficient image / video compression technology is required to effectively compress, transmit, store, and play high-resolution, high-quality image / video information having various characteristics as described above.

[0005] The technical task of this document is to provide a method and device for improving video coding efficiency.

[0006] Another technical challenge of this paper is to provide an efficient intra prediction method and device.

[0007] Another technical challenge of this paper is to provide an image coding method and device for matrix-based intra prediction.

[0008] Another technical challenge of this paper is to provide a video coding method and device for ISP-based intra prediction.

[0009] According to one embodiment of the present document, a video decoding method performed by a decoding device is provided. The method comprises the steps of: receiving video information including intra prediction type information from a bitstream, wherein the intra prediction type information includes an intra MIP syntax element for a first target block, and deriving a value of the intra MIP syntax element; setting a variable MIP flag for a predetermined specific region identical to an region of the first target block based on the value of the intra MIP syntax element; deriving an intra prediction mode of a second target block; deriving a prediction sample of the second target block based on the intra prediction mode of the second target block; and generating a reconstructed block based on the prediction sample, wherein the intra prediction mode of the second target block can be derived based on the variable MIP flag of the first target block.

[0010] The first target block is a left peripheral block of the second target block, and the step of deriving an intra prediction mode of the second target block includes: a step of deriving a candidate intra prediction mode based on the variable MIP flag; and a step of deriving the intra prediction mode of the second target block based on the candidate intra prediction mode, wherein the specific region includes a sample position of (xCb - 1, yCb + cbHeight - 1), (xCb, yCb) is an upper left sample position of the second target block, and cbHeight may represent a height of the second target block.

[0011] The first target block is an upper peripheral block of the second target block, and the step of deriving an intra prediction mode of the second target block includes: a step of deriving a candidate intra prediction mode based on the variable MIP flag; and a step of deriving the intra prediction mode of the second target block based on the candidate intra prediction mode, wherein the specific region includes a sample position of (xCb + cbWidth - 1, yCb - 1), (xCb, yCb) is an upper left sample position of the second target block, and cbWidth may represent a width of the second target block.

[0012] The second target block includes a chroma block, the first target block is a luma block related to the chroma block, and the step of deriving an intra prediction mode of the second target block may include: a step of deriving a corresponding luma intra prediction mode based on the variable MIP flag; and a step of deriving the intra prediction mode of the second target block based on the corresponding luma intra prediction mode.

[0013] At this time, based on the tree type of the second target block not being a single tree or the chroma array type not being 3, the specific area may include sample positions of (xCb + cbWidth / 2, yCb + cbHeight / 2), where (xCb, yCb) represents the upper left position of the chroma block in the luma sample unit, cbWidth may represent the width of a corresponding luma block corresponding to the chroma block, and cbWidth may represent the height of the corresponding luma block.

[0014] The variable MIP flag may be set for the specific region based on the tree type of the first target block being not a dual tree chroma.

[0015] According to one embodiment of the present document, a video encoding method performed by an encoding device is provided. The method comprises the steps of: when an intra MIP mode is applied to a first target block, deriving a value of an intra MIP flag for the first target block; setting a variable MIP flag for a predetermined specific region identical to an region of the first target block based on the value of the intra MIP flag; deriving an intra prediction mode of the second target block; deriving a prediction sample of the second target block based on the intra prediction mode of the second target block; deriving residual samples for the second target block based on the prediction sample; and encoding and outputting transform coefficient information generated based on the intra MIP flag and the residual sample, wherein the intra prediction mode of the second target block can be derived based on the variable MIP flag of the first target block.

[0016] According to another embodiment of the present document, a digital storage medium storing image data including encoded image information and / or bitstream generated according to an image encoding method performed by an encoding device may be provided.

[0017] According to another embodiment of the present document, a digital storage medium may be provided in which encoded image information and / or image data including a bitstream that causes a decoding device to perform the image decoding method may be stored.

[0018] According to this document, the overall image / video compression efficiency can be improved.

[0019] According to this document, the efficiency of intra prediction can be improved.

[0020] According to this paper, image coding efficiency for matrix-based intra prediction can be improved.

[0021] According to this paper, the video coding efficiency for ISP-based intra prediction can be improved.

[0022] The effects that can be achieved through specific examples of this specification are not limited to the effects listed above. For example, a person with ordinary skill in the relevant technical field may understand or derive various technical effects from this specification. Accordingly, the specific effects of this specification are not limited to those explicitly described herein, but may include various effects that can be understood or derived from the technical features of this specification.

[0023] Figure 1 schematically illustrates an example of a video / image coding system to which this document can be applied.

[0024] Figure 2 is a drawing schematically illustrating the configuration of a video / image encoding device to which this document can be applied.

[0025] Figure 3 is a drawing schematically illustrating the configuration of a video / image decoding device to which this document can be applied.

[0026] Figure 4 illustrates an exemplary structure of a content streaming system to which this document applies.

[0027] Figure 5 illustrates intra-directional modes of 65 prediction directions.

[0028] Figure 6 is a diagram illustrating a MIP-based prediction sample generation procedure according to an example.

[0029] Figure 7 is a diagram illustrating an example of sub-blocks into which one coding block is divided.

[0030] Figure 8 is a diagram illustrating another example of sub-blocks into which one coding block is divided.

[0031] Figure 9 schematically illustrates a multi-transformation technique according to one embodiment of the present document.

[0032] FIG. 10 is a diagram for explaining RST according to one embodiment of the present document.

[0033] FIG. 11 is a flowchart illustrating the operation of a video decoding device according to one embodiment of the present document.

[0034] FIG. 12a and FIG. 12b illustrate utilizing variable MIP flags of a first target block to derive an intra prediction mode of a second target block according to one embodiment of the present document.

[0035] Figure 13 illustrates the configuration of a sample according to a chroma format according to one embodiment of the present document.

[0036] FIGS. 14a to 14c illustrate utilizing variable MIP flags of a corresponding luma block, which is a first target block, to derive an intra prediction mode of a chroma block, which is a second target block, according to one embodiment of the present document.

[0037] FIG. 15 is a flowchart illustrating the operation of a video encoding device according to one embodiment of the present document.

[0038] This document may have various modifications and embodiments, and thus specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit this document to specific embodiments. The terminology used herein is only used to describe specific embodiments and is not intended to limit the technical idea of ​​this document. The singular expression includes plural expressions unless the context clearly indicates otherwise. It should be understood that the terms "comprises" or "has" in this specification specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0039] Meanwhile, each component in the drawings described in this document is depicted independently for the convenience of explaining their distinct functions. This does not imply that each component is implemented using separate hardware or software. For example, two or more components may be combined to form a single component, or a single component may be divided into multiple components. Embodiments in which each component is integrated and / or separated are also included within the scope of this document, as long as they do not deviate from the essence of this document.

[0040] Hereinafter, with reference to the attached drawings, a preferred embodiment of the present document will be described in more detail. Hereinafter, identical components in the drawings will be designated by the same reference numerals, and redundant descriptions of identical components will be omitted.

[0041] This document relates to video / image coding. For example, the method / embodiment disclosed in this document may be related to the Versatile Video Coding (VVC) standard (ITU-T Rec. H.266), the next-generation video / image coding standard after VVC, or other video coding-related standards (e.g., the High Efficiency Video Coding (HEVC) standard (ITU-T Rec. H.265), the essential video coding (EVC) standard, the AVS2 standard, etc.).

[0042] This document presents various embodiments of video / image coding, and unless otherwise stated, the embodiments may be performed in combination with each other.

[0043] In this document, video can mean a collection of images over time. A picture generally refers to a unit representing a single image at a specific time point, and a slice / tile is a unit that constitutes part of a picture in coding. A slice / tile can include one or more CTUs (coding tree units). A picture can be composed of one or more slices / tiles. A picture can be composed of one or more tile groups. A tile group can include one or more tiles.

[0044] A pixel or pel can mean the smallest unit that constitutes a picture (or image). Additionally, the term "sample" can be used as a counterpart to a pixel. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luma component, or only the pixel / pixel value of the chroma component. Alternatively, a sample can mean a pixel value in the spatial domain, or when such a pixel value is converted to the frequency domain, it can mean a transform coefficient in the frequency domain.

[0045] A unit may represent a basic unit of image processing. A unit may include at least one of a specific region of a picture and information related to the region. One unit may include one luma block and two chroma (e.g., cb, cr) blocks. In some cases, the term "unit" may be used interchangeably with terms such as "block" or "area." In general, an MxN block may include a set (or array) of samples (or sample array) or transform coefficients consisting of M columns and N rows.

[0046] In this document, “ / ” and “,” are interpreted as “and / or.” For example, “A / B” is interpreted as “A and / or B,” and “A, B” is interpreted as “A and / or B.” Additionally, “A / B / C” means “at least one of A, B, and / or C.” Also, “A, B, C” means “at least one of A, B, and / or C.”

[0047] Additionally, in this document, “or” is interpreted as “and / or.” For example, “A or B” can mean 1) “A” only, 2) “B” only, or 3) “A and B.” In other words, “or” in this document can mean “additionally or alternatively.”

[0048] In this specification, “at least one of A and B” may mean “only A,” “only B,” or “both A and B.” Additionally, in this specification, the expressions “at least one of A or B” or “at least one of A and / or B” may be interpreted identically to “at least one of A and B.”

[0049] Additionally, in this specification, “at least one of A, B and C” can mean “only A,” “only B,” “only C,” or “any combination of A, B and C.” Additionally, “at least one of A, B or C” or “at least one of A, B and / or C” can mean “at least one of A, B and C.”

[0050] Additionally, parentheses used herein may mean "for example." Specifically, when "prediction (intra-prediction)" is indicated, "intra-prediction" may be suggested as an example of "prediction." In other words, "prediction" in this specification is not limited to "intra-prediction," and "intra-prediction" may be suggested as an example of "prediction." Furthermore, even when "prediction (i.e., intra-prediction)" is indicated, "intra-prediction" may be suggested as an example of "prediction."

[0051] Technical features individually described in a single drawing in this specification may be implemented individually or simultaneously.

[0052] Figure 1 schematically illustrates an example of a video / image coding system to which this document can be applied.

[0053] Referring to FIG. 1, a video / image coding system may include a source device and a receiving device. The source device may transmit encoded video / image information or data to the receiving device via a digital storage medium or a network in the form of a file or streaming.

[0054] The source device may include a video source, an encoding device, and a transmitter. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be referred to as a video / video encoding device, and the decoding device may be referred to as a video / video 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.

[0055] A video source may obtain video / images through a process of capturing, synthesizing, or generating video / images. The video source may include a video / image capture device and / or a video / image generation device. A video / image capture device may include, for example, one or more cameras, a video / image archive containing previously captured video / images, etc. A video / image generation device may include, for example, a computer, a tablet, a smartphone, etc., and may (electronically) generate video / images. For example, a virtual video / image may be generated through a computer, etc., in which case the video / image capture process may be replaced by a process of generating related data.

[0056] An encoding device can encode input video / images. The encoding device can perform a series of procedures, such as prediction, transformation, and quantization, to improve compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0057] The transmission unit can transmit encoded video / image information or data output in the form of a bitstream to the receiving unit of a receiving device via a digital storage medium or network in the form of a file or streaming. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmission unit can include an element for generating a media file using a predetermined file format and an element for transmission via a broadcasting / communication network. The receiving unit can receive / extract the bitstream and transmit it to a decoding device.

[0058] The decoding device can 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.

[0059] The renderer can render decoded video / images. The rendered video / images can be displayed through the display unit.

[0060] Figure 2 is a drawing schematically illustrating the configuration of a video / image encoding device to which this document may be applied. The term "video encoding device" hereinafter may include an image encoding device.

[0061] Referring to FIG. 2, the encoding device (200) may be configured to include an image partitioner (210), a prediction unit (predictor) 220, a residual processor (residual processor) 230, an entropy encoder (entropy encoder) 240, an adder (adder) 250, a filter (filter) 260, and a memory (memory) 270. The prediction unit (220) may include an inter prediction unit (221) and an intra prediction unit (222). The residual processor (230) may include a transformer (transformer) 232, a quantizer (quantizer) 233, a dequantizer (dequantizer) 234, and an inverse transformer (inverse transformer) 235. The residual processing unit (230) may further include a subtractor (231). The addition unit (250) may be called a reconstructor or a recontructed 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 be configured by one or more hardware components (e.g., an encoder chipset or a processor) according to an embodiment. 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.

[0062] The image segmentation unit (210) can segment an input image (or picture, frame) input to the encoding device (200) into one or more processing units. For example, the processing unit may be called a coding unit (CU). In this case, the coding unit may be recursively segmented from a coding tree unit (CTU) or a largest coding unit (LCU) according to a QTBTTT (Quad-tree binary-tree ternary-tree) structure. For example, one coding unit may be segmented into a plurality of coding units of deeper depth based on a quad-tree structure, a binary tree structure, and / or a ternary structure. In this case, for example, the quad-tree structure may be applied first, and the binary tree structure and / or the ternary structure may be applied later. Alternatively, the binary tree structure may be applied first. The coding procedure according to the present document may be performed based on the final coding unit that is no longer segmented. In this case, based on coding efficiency according to image characteristics, etc., the maximum coding unit can be used as the final coding unit, or, if necessary, the coding unit can be recursively divided into coding units of lower depths, and the coding unit of the optimal size can be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration described below. As another example, the processing unit may further include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may each be divided or partitioned from the final coding unit described above.The above prediction unit may be a unit of sample prediction, and the above transformation unit may be a unit for deriving a transformation coefficient and / or a unit for deriving a residual signal from a transformation coefficient.

[0063] The term "unit" may be used interchangeably with terms such as "block" or "area" depending on the case. In general, an MxN block can represent a set of samples or transform coefficients consisting of M columns and N rows. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luminance component, or only the pixel / pixel value of the chroma component. A sample can be used as a term corresponding to a pixel or pel in a picture (or image).

[0064] The subtraction unit (231) can subtract the prediction signal (predicted block, prediction samples, or prediction sample array) output from the prediction unit (220) from the input image signal (original block, original samples, or original sample array) to generate a residual signal (residual block, residual samples, or residual sample array), and the generated residual signal is transmitted to the conversion unit (232). The prediction unit (220) can 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 (220) can determine whether intra prediction or inter prediction is applied to the current block or CU unit. The prediction unit can generate various information regarding prediction, such as prediction mode information, as described later in the description of each prediction mode, and transmit the information to the entropy encoding unit (240). Information about the prediction can be encoded in the entropy encoding unit (240) and output in the form of a bitstream.

[0065] The intra prediction unit (222) can predict the current block by referring to samples within the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from it depending on the prediction mode. In intra prediction, the prediction modes may include multiple non-directional modes and multiple directional modes. The non-directional modes may include, for example, a DC mode and a planar mode. The directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes depending on the degree of detail in the prediction direction. However, this is merely an example, and a greater or lesser number of directional prediction modes may be used depending on the settings. The intra prediction unit (222) may also determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0066] The inter prediction unit (221) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring block can 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 above temporal neighboring blocks may be called collocated reference blocks, collocated CUs (colCUs), etc., and the reference pictures including the temporal neighboring blocks may be called collocated pictures (colPic). For example, the inter prediction unit (221) may construct a motion information candidate list based on the neighboring blocks, and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the inter prediction unit (221) may use the motion information of the neighboring blocks as the motion information of the current block. In the case of skip mode, unlike the merge mode, a residual signal may not be transmitted.In the motion vector prediction (MVP) mode, the motion vector of the surrounding blocks is used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling the motion vector difference.

[0067] The prediction unit (220) can generate a prediction signal based on various prediction methods described below. For example, the prediction unit can apply intra prediction or inter prediction to predict a single block, and can also apply intra prediction and inter prediction simultaneously. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit can perform intra block copy (IBC) to predict a block. The intra block copy can be used for content image / video coding such as games, such as screen content coding (SCC). IBC basically performs prediction within the current picture, but can be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in this document.

[0068] The prediction signal generated through the inter prediction unit (221) and / or the intra prediction unit (222) can be used to generate a reconstructed signal or a residual signal. The transform unit (232) can apply a transform technique to the residual signal to generate transform coefficients. For example, the transform technique can include a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), a Graph-Based Transform (GBT), or a Conditionally Non-linear Transform (CNT). Here, GBT refers to a transform obtained from a graph when the relationship information between pixels is expressed as a graph. CNT refers to a transform obtained based on generating a prediction signal using all previously reconstructed pixels. In addition, the transform process can be applied to a pixel block having a square equal size, or can be applied to a block of a non-square variable size.

[0069] The quantization unit (233) quantizes the transform coefficients and transmits them to the entropy encoding unit (240), and the entropy encoding unit (240) can encode the quantized signal (information about the quantized transform coefficients) and output it as a bitstream. The information about the quantized transform coefficients may be called residual information. The quantization unit (233) can rearrange the quantized transform coefficients in a block form into a one-dimensional vector form based on a coefficient scan order, and can also generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. The entropy encoding unit (240) can perform various encoding methods, such as, for example, exponential Golomb, context-adaptive variable length coding (CAVLC), context-adaptive binary arithmetic coding (CABAC), etc. The entropy encoding unit (240) may encode, together or separately, information necessary for video / image restoration (e.g., values ​​of syntax elements, etc.) in addition to the quantized transform coefficients. The encoded information (e.g., encoded video / image information) may be transmitted or stored in the form of a bitstream in the form of a network abstraction layer (NAL) unit. The video / image 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 / image information may further include general constraint information. The signaling / transmitted information and / or syntax elements described later in this document may be encoded through the above-described encoding procedure and included in the bitstream.The above bitstream may be transmitted through a network or 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, SSD, etc. The signal output from the entropy encoding unit (240) may be configured as an internal / external element of the encoding device (200) by a transmitting unit (not shown) and / or a storing unit (not shown), or the transmitting unit may be included in the entropy encoding unit (240).

[0070] The quantized transform coefficients output from the quantization unit (233) can be used to generate a prediction signal. For example, by applying inverse quantization and inverse transformation to the quantized transform coefficients through the inverse quantization unit (234) and the inverse transform unit (235), a residual signal (residual block or residual samples) can be reconstructed. The addition unit (250) can add the reconstructed residual signal to the prediction signal output from the prediction unit (220), thereby generating a reconstructed signal (reconstructed picture, reconstructed block, reconstructed samples, or reconstructed sample array). When there is no residual for the target block to be processed, such as when skip mode is applied, the predicted block can be used as the reconstructed block. The generated reconstructed signal can be used for intra prediction of the next target block to be processed within the current picture, and can also be used for inter prediction of the next picture after filtering as described below.

[0071] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture encoding and / or restoration process.

[0072] The filtering unit (260) can improve subjective / objective picture quality by applying filtering to the restoration signal. For example, the filtering unit (260) can apply various filtering methods to the restoration picture to generate a modified restoration picture, and store the modified restoration picture in the memory (270), specifically, in the DPB of the memory (270). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset (SAO), adaptive loop filter, bilateral filter, etc. The filtering unit (260) can generate various information regarding filtering and transmit it to the entropy encoding unit (290), as described later in the description of each filtering method. The information regarding filtering can be encoded by the entropy encoding unit (290) and output in the form of a bitstream.

[0073] The modified restored picture transmitted to the memory (270) can be used as a reference picture in the inter prediction unit (280). Through this, when inter prediction is applied, the encoding device can avoid prediction mismatch between the encoding device (200) and the decoding device, and can also improve encoding efficiency.

[0074] The DPB of the memory (270) can store the modified restored picture to be used as a reference picture in the inter prediction unit (221). The memory (270) can store motion information of a block from which motion information is derived (or encoded) within the current picture and / or motion information of blocks within a picture that has already been restored. The stored motion information can be transferred to the inter prediction unit (221) to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory (270) can store restored samples of restored blocks within the current picture and transfer them to the intra prediction unit (222).

[0075] Figure 3 is a drawing schematically illustrating the configuration of a video / image decoding device to which this document can be applied.

[0076] Referring to FIG. 3, the decoding device (300) may be configured to include an entropy decoder (310), a residual processor (320), a predictor (330), an adder (340), a filter (350), and a memory (360). The predictor (330) may include an inter-prediction unit (331) and an intra-prediction unit (332). The residual processor (320) may include a dequantizer (321) and an inverse transformer (321). The entropy decoding unit (310), residual processing unit (320), prediction unit (330), addition unit (340), and filtering unit (350) described above may be configured by a single hardware component (e.g., decoder chipset or processor) depending on the embodiment. 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.

[0077] When a bitstream including video / image information is input, the decoding device (300) can restore the image corresponding to the process in which the video / image information is processed in the encoding device of FIG. 2. For example, the decoding device (300) can derive units / blocks based on block division-related information obtained from the bitstream. The decoding device (300) can perform decoding using a processing unit applied in the encoding device. Therefore, 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 according to 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. Then, the restored image signal decoded and output through the decoding device (300) can be reproduced through a reproduction device.

[0078] The decoding device (300) can receive a signal output from the encoding device of FIG. 2 in the form of a bitstream, and the received signal can be decoded through the entropy decoding unit (310). For example, the entropy decoding unit (310) can parse the bitstream to derive information (e.g., video / image information) necessary for image restoration (or picture restoration). The video / image 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 / image information may further include general constraint information. The decoding device can decode the picture further based on the information on the parameter set and / or the general constraint information. The signaling / received information and / or syntax elements described later in this document can be decoded and obtained from the bitstream through the decoding procedure. For example, the entropy decoding unit (310) can decode information in a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the values ​​of syntax elements required for image restoration and the quantized values ​​of transform coefficients for residuals. More specifically, the CABAC entropy decoding method receives a bin corresponding to each syntax element in the bitstream, determines a context model using information of a syntax element to be decoded and decoding information of surrounding and decoding target blocks or information of symbols / bins decoded in the previous step, and predicts the occurrence probability of a bin according to the determined context model to perform arithmetic decoding of the bin to generate a symbol corresponding to the value of each syntax element.At this time, the CABAC entropy decoding method can update the context model using the information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model. Information about prediction among the information decoded by the entropy decoding unit (310) is provided to the prediction unit (330), and information about the residual on which entropy decoding is performed by the entropy decoding unit (310), that is, quantized transform coefficients and related parameter information, can be input to the inverse quantization unit (321). In addition, information about filtering among the information decoded by the entropy decoding unit (310) can be provided to the filtering unit (350). Meanwhile, a receiving unit (not shown) that receives a signal output from an encoding device may be further configured as an internal / external element of the decoding device (300), or the receiving unit may be a component of the entropy decoding unit (310). Meanwhile, the decoding device according to the present document may be called a video / video / picture decoding device, and the decoding device may be divided into an information decoder (video / video / picture information decoder) and a sample decoder (video / video / picture sample decoder). The information decoder may include the entropy decoding unit (310), and the sample decoder may include at least one of the inverse quantization unit (321), the inverse transformation unit (322), the prediction unit (330), the addition unit (340), the filtering unit (350), and the memory (360).

[0079] The inverse quantization unit (321) can inverse quantize the quantized transform coefficients and output the transform coefficients. The inverse quantization unit (321) can rearrange the quantized transform coefficients into a two-dimensional block form. In this case, the rearrangement can be performed based on the coefficient scanning order performed in the encoding device. The inverse quantization unit (321) can perform inverse quantization on the quantized transform coefficients using quantization parameters (e.g., quantization step size information) and obtain transform coefficients.

[0080] In the inverse transform unit (322), the transform coefficients are inversely transformed to obtain a residual signal (residual block, residual sample array).

[0081] The prediction unit can perform a prediction on the current block and generate a predicted block containing prediction samples for the current block. Based on the information regarding the prediction output from the entropy decoding unit (310), the prediction unit can determine whether intra-prediction or inter-prediction is applied to the current block, and can determine a specific intra / inter-prediction mode.

[0082] The prediction unit can generate a prediction signal based on various prediction methods described below. For example, the prediction unit can apply intra prediction or inter prediction to predict a single block, and can also apply intra prediction and inter prediction simultaneously. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit can perform intra block copy (IBC) to predict a block. The intra block copy can be used for content image / video coding such as games, such as screen content coding (SCC). IBC basically performs prediction within the current picture, but can be performed similarly to inter prediction in that it derives a reference block within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in this document.

[0083] The intra prediction unit (332) can predict the current block by referring to samples within the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from it, depending on the prediction mode. In intra prediction, the prediction modes may include multiple non-directional modes and multiple directional modes. The intra prediction unit (332) can also determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0084] The inter prediction unit (331) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring blocks can include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter prediction unit (331) can construct a motion information candidate list based on the neighboring blocks, and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter prediction can be performed based on various prediction modes, and the information about the prediction can include information indicating the mode of inter prediction for the current block.

[0085] The addition unit (340) can generate a restoration signal (restored picture, restoration block, restoration sample array) by adding the acquired residual signal to the prediction signal (predicted block, prediction sample array) output from the prediction unit (330). In cases where there is no residual for the block to be processed, such as when skip mode is applied, the predicted block can be used as the restoration block.

[0086] The addition unit (340) may be referred to as a restoration unit or restoration block generation unit. The generated restoration signal may be used for intra prediction of the next processing target block within the current picture, may be output after filtering as described below, or may be used for inter prediction of the next picture.

[0087] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture decoding process.

[0088] The filtering unit (350) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (350) can apply various filtering methods to the restored picture to generate a modified restored picture, and transmit the modified restored picture to the memory (60), specifically, the DPB of the memory (360). The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0089] The (modified) reconstructed picture stored in the DPB of the memory (360) can be used as a reference picture in the inter prediction unit (331). The memory (360) can store motion information of a block from which motion information is derived (or decoded) in the current picture and / or motion information of blocks in a picture that has already been reconstructed. The stored motion information can be transferred to the inter prediction unit (331) to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory (360) can store reconstructed samples of reconstructed blocks in the current picture and transfer them to the intra prediction unit (332).

[0090] In this specification, the embodiments described in the prediction unit (330), inverse quantization unit (321), inverse transformation unit (322), and filtering unit (350) of the decoding device (300) can be applied to the prediction unit (220), inverse quantization unit (234), inverse transformation unit (235), and filtering unit (260) of the encoding device (200) in the same manner or correspondingly.

[0091] As described above, prediction is performed to increase compression efficiency when performing video coding. Through this, a predicted block including prediction samples for a current block, which is a coding target block, can be generated. Here, the predicted block includes prediction samples in a spatial domain (or pixel domain). The predicted block is derived identically from an encoding device and a decoding device, and the encoding device can increase video coding efficiency by signaling information (residual information) about the residual between the original block and the predicted block, rather than the original sample value of the original block itself, to a decoding device. The decoding device can derive a residual block including residual samples based on the residual information, and generate a reconstructed block including reconstructed samples by combining the residual block and the predicted block, and can generate a reconstructed picture including the reconstructed blocks.

[0092] The residual information may be generated through a transformation and quantization procedure. For example, the encoding device may derive a residual block between the original block and the predicted block, perform a transformation procedure on residual samples (a residual sample array) included in the residual block to derive transform coefficients, and perform a quantization procedure on the transform coefficients to derive quantized transform coefficients, thereby signaling the related residual information to a decoding device (via a bitstream). Here, the residual information may include information such as value information, position information, a transformation technique, a transformation kernel, and quantization parameters of the quantized transform coefficients. The decoding device may perform an inverse quantization / inverse transformation procedure based on the residual information to derive residual samples (or residual blocks). The decoding device may generate a reconstructed picture based on the predicted block and the residual block. The encoding device can also inversely quantize / inversely transform the quantized transform coefficients to derive a residual block for reference in inter prediction of a subsequent picture, and generate a restored picture based on the residual block.

[0093] Figure 4 illustrates an exemplary structure of a content streaming system to which this document applies.

[0094] Additionally, the content streaming system to which this document applies may broadly include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0095] The encoding server compresses content input from multimedia input devices such as smartphones, cameras, camcorders, etc. into digital data to generate a bitstream and transmits it to the streaming server. As another example, if multimedia input devices such as smartphones, cameras, camcorders, etc. directly generate a bitstream, the encoding server may be omitted. The bitstream may be generated by an encoding method or a bitstream generation method to which this document applies, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0096] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server acts as an intermediary to inform the user of available services. When a user requests a desired service from the web server, the web server transmits the request to the streaming server, and the streaming server transmits the multimedia data to the user. At this time, the content streaming system may include a separate control server, in which case the control server controls commands / responses between each device within the content streaming system.

[0097] The streaming server can receive content from a media repository and / or an encoding server. For example, when receiving content from the encoding server, the content can be received in real time. In this case, to provide a smooth streaming service, the streaming server can store the bitstream for a certain period of time.

[0098] Examples of the user devices include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, head mounted displays (HMDs), digital TVs, desktop computers, digital signage, etc.). Each server in the content streaming system may be operated as a distributed server, in which case data received from each server may be distributedly processed.

[0099] Meanwhile, when intra prediction is performed, correlations between samples can be utilized, and the difference between the original block and the predicted block, i.e., the residual, can be obtained. The aforementioned transformation and quantization can be applied to the residual, thereby removing spatial redundancy. Below, encoding and decoding methods using intra prediction are described in detail.

[0100] Intra prediction refers to prediction that generates prediction samples for the current block based on reference samples outside the current block within the picture containing the current block (hereinafter, "current picture"). Here, reference samples outside the current block refer to samples located around the current block. When intra prediction is applied to the current block, neighboring reference samples can be derived to be used for intra prediction of the current block.

[0101] For example, when the size (width x height) of the current block is nWxnH, the surrounding reference samples of the current block may include a total of 2xnH samples adjacent to the left boundary and the bottom-left neighboring samples of the current block, a total of 2xnW samples adjacent to the top boundary and the top-right neighboring samples of the current block, and one sample adjacent to the top-left of the current block. Alternatively, the surrounding reference samples of the current block may include upper surrounding samples of multiple columns and left surrounding samples of multiple rows. In addition, the surrounding reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of nWxnH size, a total of nW samples adjacent to the bottom boundary of the current block, and one sample adjacent to the bottom-right of the current block.

[0102] However, some of the surrounding reference samples of the current block may not yet be decoded or available. In this case, the decoding device can construct the surrounding reference samples to be used for prediction by replacing the unavailable samples with available samples. Alternatively, the decoding device can construct the surrounding reference samples to be used for prediction by interpolating the available samples.

[0103] When peripheral reference samples are derived, (i) a prediction sample can be derived based on an average or interpolation of peripheral reference samples of the current block, and (ii) a prediction sample can be derived based on a reference sample existing in a specific (prediction) direction with respect to the prediction sample among peripheral reference samples of the current block. Case (i) can be applied when the intra prediction mode is a non-directional mode or a non-angular mode, and case (ii) can be applied when the intra prediction mode is a directional mode or an angular mode.

[0104] Meanwhile, the intra prediction mode may include non-directional (or non-angular) intra prediction modes and directional (or angular) intra prediction modes. For example, the HEVC standard uses intra prediction modes including two non-directional prediction modes and 33 directional prediction modes. The non-directional prediction modes may include a planar intra prediction mode numbered 0 and a DC intra prediction mode numbered 1, and the directional prediction modes may include intra prediction modes numbered 2 to 34. The planar intra prediction mode may be referred to as a planar mode, and the DC intra prediction mode may be referred to as a DC mode.

[0105] Alternatively, in order to capture arbitrary edge directions presented in natural video, the directional intra prediction modes can be extended from the existing 33 to 65, as shown in FIG. 10, which will be described later. In this case, the intra prediction modes can include two non-directional intra prediction modes and 65 directional intra prediction modes. The non-directional intra prediction modes can include a planar intra prediction mode numbered 0 and a DC intra prediction mode numbered 1, and the directional intra prediction modes can include intra prediction modes numbered 2 to 66. The extended directional intra prediction modes can be applied to blocks of all sizes and to both luma components and chroma components. However, this is an example, and the embodiments of the present document can also be applied when the number of intra prediction modes is different. In some cases, intra prediction mode 67 may be used more, and intra prediction mode 67 may represent LM (linear model) mode.

[0106] Figure 5 shows an example of intra prediction modes to which embodiments of the present document can be applied.

[0107] Referring to Fig. 5, intra prediction modes with horizontal directionality and intra prediction modes with vertical directionality can be distinguished centered on intra prediction mode number 34 having an upward left diagonal prediction direction. H and V in Fig. 10 represent horizontal directionality and vertical directionality, respectively, and numbers -32 to 32 represent displacements in units of 1 / 32 on the sample grid position. Intra prediction modes numbered 2 to 33 have horizontal directionality, and intra prediction modes numbered 34 to 66 have vertical directionality. The 18th intra prediction mode and the 50th intra prediction mode represent the horizontal intra prediction mode and the vertical intra prediction mode, respectively. The 2nd intra prediction mode can be called the left-downward diagonal intra prediction mode, the 34th intra prediction mode can be called the left-upward diagonal intra prediction mode, and the 66th intra prediction mode can be called the right-upward diagonal intra prediction mode.

[0108] Meanwhile, matrix-based intra prediction (MIP) can be used as one method for intra prediction. MIP can be referred to as affine linear weighted intra prediction (ALWIP) or matrix weighted intra prediction (MWIP).

[0109] When MIP is applied to a current block, prediction samples for the current block can be derived by i) performing a matrix-vector-multiplication procedure using surrounding reference samples on which an averaging procedure has been performed, ii) and further performing a horizontal / vertical interpolation procedure as needed. The intra prediction modes used for the MIP can be configured differently from the intra prediction modes used in the above-described LIP, PDPC, MRL, ISP intra prediction, or normal intra prediction.

[0110] The intra prediction mode for MIP may be called “affine linear weighted intra prediction mode” or matrix-based intra prediction mode. For example, the matrix and offset used in matrix vector multiplication may be set differently depending on the intra prediction mode for the MIP. Here, the matrix may be called an (affine) weight matrix, and the offset may be called an (affine) offset vector or an (affine) bias vector. In this document, the intra prediction mode for MIP may be called MIP intra prediction mode, affine linear weighted intra prediction mode (ALWIP), matrix weighted intra prediction mode (MWI), matrix-based intra prediction mode, etc.

[0111] To predict a sample of a rectangular block with width (W) and height (H), MIP uses as input an H line of one of the reconstructed left-side boundary samples of the block and a W line of one of the reconstructed upper-side boundary samples of the block. If reconstructed samples are not available, reference samples can be generated using the interpolation method applied in conventional intra prediction.

[0112] FIG. 6 is a drawing illustrating a MIP-based prediction sample generation procedure according to an example. The MIP procedure is described below with reference to FIG. 6.

[0113] 1. Averaging process

[0114] Among the boundary samples, 4 samples are extracted by the averaging procedure when W = H = 4, and 8 samples in all other cases.

[0115] 2. Matrix vector multiplication process

[0116] A matrix-vector multiplication is performed on the averaged samples as input, followed by an offset. This operation yields reduced prediction samples for a sub-sampled set of samples within the original block.

[0117] 3. Interpolation process (linear)

[0118] Prediction samples at the remaining locations are generated from prediction samples of the subsampled sample set by linear interpolation, which is a single step linear interpolation in each direction.

[0119] The matrices and offset vectors required to generate prediction blocks or prediction samples can be selected from three sets S0, S1, S2 for matrices.

[0120] The set S0 can be composed of 16 matrices A0i, i∈{0,…,15}, each matrix can be composed of 16 rows and 4 columns and 16 offset vectors b0i, i∈{0,…,15}. The matrices and offset vectors of the set S0 can be used in blocks of size 4 × 4. As another example, the set S0 can also contain 18 matrices.

[0121] The set S1 consists of eight matrices A1i, i∈{0,…, 7}, each matrix can have 16 rows and 8 columns and eight offset vectors b1i, i∈{0,…, 7}. In another example, the set S1 can also contain six matrices. The matrices and offset vectors of the set S1 can be used for blocks of size 4 × 8, 8 × 4 and 8 × 8. Alternatively, the matrices and offset vectors of the set S1 can be used for blocks of size 4 × H or W × 4.

[0122] Finally, the set S2 consists of six matrices A2i, i∈{0,…,5}, each of which can be composed of 64 rows and 8 columns and six offset vectors b2i, i∈{0,…,5}. The matrices and offset vectors of the set S2, or part of them, can be used in block shapes of any size not covered by the sets S0 and S1. For example, the matrices and offset vectors of the set S2 can be used in operations on blocks with height and width greater than 8.

[0123] The total number of multiplications required to compute a matrix-vector product is always less than or equal to 4 X W X H. That is, MIP mode requires at most 4 multiplications per sample.

[0124] Additionally, the current block can be divided into vertical or horizontal subpartitions, and intra prediction can be performed based on the same intra prediction mode, while extracting and utilizing surrounding reference samples for each subpartition. In other words, in this case, the intra prediction mode for the current block is applied equally to the subpartitions, but by extracting and utilizing surrounding reference samples for each subpartition, intra prediction performance can be improved in some cases. This prediction method can be called intra subpartitions (ISP) or ISP-based intra prediction.

[0125] ISP (Intra Sub-Partitions) coding means performing intra prediction coding by dividing the block to be encoded horizontally or vertically. At this time, encoding / decoding is performed on each divided block to generate a reconstructed block, and the reconstructed block can be used as a reference block for the next divided block. For example, in ISP coding, one coding block can be divided into two or four sub-blocks and coded, and in ISP, one sub-block performs intra prediction by referencing the reconstructed pixel value of the adjacent left or adjacent upper sub-block. Hereinafter, the term “coding” may be used as a concept including both coding performed in an encoding device and decoding performed in a decoding device.

[0126] Table 1 shows the number of sub-blocks divided according to the block size when applying ISP, and the sub-partitions divided according to ISP can be called transform blocks (TUs).

[0127]

[0128] ISP divides a block predicted by luma intra into two or four sub-partitions vertically or horizontally, depending on the block size. For example, the minimum block size for which ISP can be applied is 4 x 8 or 8 x 4. If the block size is larger than 4 x 8 or 8 x 4, the block is divided into four sub-partitions.

[0129] FIG. 7 and FIG. 8 illustrate examples of sub-blocks into which one coding block is divided. More specifically, FIG. 7 illustrates an example of division when the coding block (width (W) X height (H)) is a 4 x 8 block or an 8 x 4 block, and FIG. 8 illustrates an example of division when the coding block is not a 4 x 8 block, an 8 x 4 block, or a 4 x 4 block.

[0130] When applying ISP, sub-blocks are sequentially coded according to the partitioning form, for example, horizontally or vertically, from left to right or from top to bottom, and after performing inverse transformation and intra prediction on one sub-block and a restoration process, coding can proceed for the next sub-block. For the leftmost or topmost sub-block, the restored pixels of the already coded coding block are referenced as in a typical intra prediction method. In addition, for each side of the subsequent internal sub-block, if it is not adjacent to the previous sub-block, the restored pixels of the already coded adjacent coding block are referenced as in a typical intra prediction method to derive reference pixels adjacent to the corresponding side.

[0131] In ISP coding mode, all sub-blocks can be coded with the same intra prediction mode, and flags indicating whether to use ISP coding and flags indicating in which direction (horizontal or vertical) to split can be signaled. As shown in FIGS. 7 and 8, the number of sub-blocks can be adjusted to 2 or 4 depending on the block shape, and if the size (width x height) of one sub-block is less than 16, splitting into that sub-block can be disallowed, or ISP coding itself can be restricted from being applied.

[0132] Meanwhile, in the case of ISP prediction mode, one coding unit is divided into two or four partition blocks, i.e., sub-blocks, and predicted, and the same intra prediction mode is applied to the two or four divided partition blocks.

[0133] Figure 9 schematically illustrates a multiple transformation technique according to this document.

[0134] Referring to FIG. 9, the conversion unit may correspond to the conversion unit in the encoding device of FIG. 2 described above, and the inverse conversion unit may correspond to the inverse conversion unit in the encoding device of FIG. 2 described above or the inverse conversion unit in the decoding device of FIG. 3.

[0135] The transformation unit can derive (primary) transformation coefficients by performing a primary transformation based on residual samples (residual sample array) within the residual block (S910). This primary transformation may be referred to as a core transformation. Here, the primary transformation may be based on multiple transform selection (MTS), and when multiple transformations are applied as the primary transformation, it may be referred to as a multiple core transformation.

[0136] The multi-core transform may indicate a method of transforming by additionally using Discrete Cosine Transform (DCT) Type 2 and Discrete Sine Transform (DST) Type 7, DCT Type 8, and / or DST Type 1. That is, the multi-core transform may indicate a transform method of transforming a residual signal (or residual block) of a spatial domain into transform coefficients (or primary transform coefficients) of a frequency domain based on a plurality of transform kernels selected from among the DCT Type 2, the DST Type 7, the DCT Type 8, and the DST Type 1. Here, the primary transform coefficients may be called temporary transform coefficients from the perspective of a transform unit.

[0137] In other words, when the conventional transform method is applied, a transformation from the spatial domain to the frequency domain can be applied to the residual signal (or residual block) based on DCT type 2, so that transform coefficients can be generated. In contrast, when the multi-core transform is applied, a transformation from the spatial domain to the frequency domain can be applied to the residual signal (or residual block) based on DCT type 2, DST type 7, DCT type 8, and / or DST type 1, so that transform coefficients (or first-order transform coefficients) can be generated. Here, DCT type 2, DST type 7, DCT type 8, and DST type 1, etc. may be called a transform type, a transform kernel, or a transform core. These DCT / DST transform types can be defined based on basis functions.

[0138] When the above multi-core transform is performed, a vertical transform kernel and a horizontal transform kernel for a target block may be selected from among the transform kernels, and a vertical transform may be performed for the target block based on the vertical transform kernel, and a horizontal transform may be performed for the target block based on the horizontal transform kernel. Here, the horizontal transform may represent a transform for horizontal components of the target block, and the vertical transform may represent a transform for vertical components of the target block. The vertical transform kernel / horizontal transform kernel may be adaptively determined based on a prediction mode and / or a transform index of a target block (CU or sub-block) including a residual block.

[0139] In addition, according to an example, when performing a first transformation by applying MTS, specific basis functions can be set to predetermined values, and a mapping relationship for the transformation kernel can be set by combining which basis functions are applied when performing a vertical transformation or a horizontal transformation. For example, when a horizontal transformation kernel is represented as trTypeHor and a vertical transformation kernel is represented as trTypeVer, a trTypeHor or trTypeVer value of 0 can be set to DCT2, a trTypeHor or trTypeVer value of 1 can be set to DST7, and a trTypeHor or trTypeVer value of 2 can be set to DCT8.

[0140] In this case, MTS index information may be encoded and signaled to the decoding device to indicate which of a plurality of sets of transform kernels. For example, an MTS index of 0 may indicate that both trTypeHor and trTypeVer values ​​are 0, an MTS index of 1 may indicate that both trTypeHor and trTypeVer values ​​are 1, an MTS index of 2 may indicate that trTypeHor values ​​are 2 and trTypeVer values ​​are 1, an MTS index of 3 may indicate that trTypeHor values ​​are 1 and trTypeVer values ​​are 2, and an MTS index of 4 may indicate that both trTypeHor and trTypeVer values ​​are 2.

[0141] As an example, the set of transformation kernels according to MTS index information is presented in the following table.

[0142]

[0143] The transform unit can derive modified (secondary) transform coefficients by performing a secondary transform based on the (first) transform coefficients (S920). The first transform is a transform from a spatial domain to a frequency domain, and the second transform means a transform to a more compact representation by utilizing a correlation existing between the (first) transform coefficients. The second transform may include a non-separable transform. In this case, the second transform may be called a non-separable secondary transform (NSST) or a mode-dependent non-separable secondary transform (MDNSST). The non-separable secondary transform may represent a transform that generates modified transform coefficients (or secondary transform coefficients) for a residual signal by performing a secondary transform on the (first) transform coefficients derived through the first transform based on a non-separable transform matrix. Here, based on the non-separable transformation matrix, the vertical transformation and horizontal transformation (or the horizontal-vertical transformation independently) can be applied to the (primary) transformation coefficients at once without being applied separately. In other words, the non-separable secondary transformation is not applied separately to the vertical and horizontal directions for the (primary) transformation coefficients, but, for example, a transformation method can be represented in which two-dimensional signals (transform coefficients) are rearranged into one-dimensional signals in a specific predetermined direction (e.g., row-first direction or column-first direction), and then modified transformation coefficients (or secondary transformation coefficients) are generated based on the non-separable transformation matrix. For example, the row-first order is to arrange them in a row in the order of the 1st row, the 2nd row, ..., the Nth row for an MxN block, and the column-first order is to arrange them in the order of the 1st column, the 2nd column, ... for an MxN block., and arrange them in a row in the order of the Mth column. The non-separable secondary transform can be applied to the top-left region of a block composed of (primary) transform coefficients (hereinafter, referred to as a transform coefficient block). For example, if both the width (W) and the height (H) of the transform coefficient block are 8 or more, an 8×8 non-separable secondary transform can be applied to the top-left 8×8 region of the transform coefficient block. In addition, if both the width (W) and the height (H) of the transform coefficient block are 4 or more, and either the width (W) or the height (H) of the transform coefficient block is less than 8, a 4×4 non-separable secondary transform can be applied to the top-left min(8,W)×min(8,H) region of the transform coefficient block. However, the embodiment is not limited thereto, and for example, even if only the condition that both the width (W) or the height (H) of the transform coefficient block is 4 or greater is satisfied, a 4×4 non-separable second-order transform may be applied to the upper left min(8,W)×min(8,H) region of the transform coefficient block.

[0144] At this time, for selecting the transformation kernel, two non-separable second-order transform kernels may be configured per transformation set for both the 8×8 transformation and the 4×4 transformation, and the number of transformation sets may be four. That is, four transformation sets may be configured for the 8×8 transformation, and four transformation sets may be configured for the 4×4 transformation. In this case, each of the four transformation sets for the 8×8 transformation may include two 8×8 transformation kernels, and each of the four transformation sets for the 4×4 transformation may include two 4×4 transformation kernels.

[0145] However, the size of the above transformation, i.e., the size of the area to which the transformation is applied, may be a size other than 8×8 or 4×4, for example, and the number of sets may be n, and the number of transformation kernels in each set may be k.

[0146] The above transform set may be referred to as an NSST set or an LFNST set. The selection of a particular set among the above transform sets may be performed based on, for example, the intra prediction mode of the current block (CU or sub-block). The LFNST (Low-Frequency Non-Separable Transform) may be an example of a reduced non-separable transform described below, and represents a non-separable transform for low-frequency components.

[0147] As an example, the mapping of four sets of transformations depending on the intra prediction mode can be represented, for example, as shown in the following table.

[0148]

[0149] As shown in Table 3, depending on the intra prediction mode, any one of the four transformation sets, i.e., lfnstTrSetIdx can be mapped to any one of the four sets, from 0 to 3.

[0150] Meanwhile, if it is determined that a specific set is used for the non-separable transform, one of the k transform kernels within the specific set can be selected through a non-separable secondary transform index. The encoding device can derive a non-separable secondary transform index indicating a specific transform kernel based on a rate-distortion (RD) check, and signal the non-separable secondary transform index to a decoding device. The decoding device can select one of the k transform kernels within the specific set based on the non-separable secondary transform index. For example, an lfnst index value of 0 can indicate a first non-separable secondary transform kernel, an lfnst index value of 1 can indicate a second non-separable secondary transform kernel, and an lfnst index value of 2 can indicate a third non-separable secondary transform kernel. Alternatively, the lfnst index value 0 may indicate that the first non-separable second transform is not applied to the target block, and the lfnst index values ​​1 to 3 may indicate the three transform kernels.

[0151] The transform unit can perform the non-separable second-order transform based on the selected transform kernels and obtain modified (second-order) transform coefficients. The modified transform coefficients can be derived as quantized transform coefficients through the quantization unit as described above, and can be encoded and transmitted to the decoding device and the inverse quantization / inverse transform unit within the signaling and encoding device.

[0152] Meanwhile, when the secondary transformation is omitted as described above, the (primary) transformation coefficients, which are the output of the primary (separation) transformation, can be derived as quantized transformation coefficients through the quantization unit as described above, and can be encoded and transmitted to the decoding device and the inverse quantization / inverse transformation unit in the signaling and encoding device.

[0153] The inverse transform unit can perform a series of procedures in the reverse order of the procedures performed in the above-described transform unit. The inverse transform unit can receive (inverse quantized) transform coefficients, perform a secondary (inverse) transform to derive (primary) transform coefficients (S950), and perform a primary (inverse) transform on the (primary) transform coefficients to obtain a residual block (residual samples) (S960). Here, the primary transform coefficients can be called modified transform coefficients from the inverse transform unit's perspective. As described above, the encoding device and the decoding device can generate a reconstructed block based on the residual block and the predicted block, and generate a reconstructed picture based on the reconstructed block.

[0154] Meanwhile, the decoding device may further include a second inverse transform application decision unit (or an element that determines whether to apply the second inverse transform) and a second inverse transform decision unit (or an element that determines the second inverse transform). The second inverse transform application decision unit may determine whether to apply the second inverse transform. For example, the second inverse transform may be NSST, RST, or LFNST, and the second inverse transform application decision unit may determine whether to apply the second inverse transform based on a second transform flag parsed from the bitstream. As another example, the second inverse transform application decision unit may determine whether to apply the second inverse transform based on a transform coefficient of a residual block.

[0155] The secondary inverse transform decision unit can determine the secondary inverse transform. At this time, the secondary inverse transform decision unit can determine the secondary inverse transform to be applied to the current block based on a set of LFNST (NSST or RST) transforms specified according to the intra prediction mode. In addition, as an embodiment, the secondary transform decision method can be determined depending on the primary transform decision method. Various combinations of the primary transform and the secondary transform can be determined according to the intra prediction mode. In addition, as an example, the secondary inverse transform decision unit can determine the area to which the secondary inverse transform is applied based on the size of the current block.

[0156] Meanwhile, as described above, when the second (inverse) transformation is omitted, the (inverse quantized) transformation coefficients can be received and the first (separate) inverse transformation can be performed to obtain a residual block (residual samples). As described above, the encoding device and the decoding device can generate a restoration block based on the residual block and the predicted block, and can generate a restoration picture based on the same.

[0157] Meanwhile, in this paper, to reduce the amount of computation and memory required for non-separable secondary transforms, a reduced secondary transform (RST) with a reduced transform matrix (kernel) size can be applied based on the concept of NSST. In addition, since RST is mainly performed in the low-frequency region containing non-zero coefficients in the transform block, it can also be referred to as a low-frequency non-separable transform (LFNST). The above transform index can be named an LFNST index.

[0158] In this specification, LFNST may refer to a transformation performed on residual samples of a target block based on a reduced-size transformation matrix. When performing a simplified transformation, the amount of computation required during the transformation may be reduced due to the reduced size of the transformation matrix. In other words, LFNST may be used to resolve computational complexity issues that arise when transforming large blocks or performing non-separable transformations.

[0159] Meanwhile, when the secondary inverse transform is performed based on LFNST, the inverse transform unit (235) of the encoding device (200) and the inverse transform unit (322) of the decoding device (300) may include an inverse RST unit that derives modified transform coefficients based on the inverse RST for the transform coefficients, and an inverse first transform unit that derives residual samples for the target block based on the inverse first transform for the modified transform coefficients. The inverse first transform means the inverse transform of the first transform applied to the residual. In this document, deriving transform coefficients based on the transform may mean deriving transform coefficients by applying the transform.

[0160] FIG. 10 is a diagram for explaining RST according to one embodiment of the present document.

[0161] In this specification, “target block” may mean a current block, a residual block, or a transformation block on which coding is performed.

[0162] In an RST according to one embodiment, an N-dimensional vector may be mapped to an R-dimensional vector located in another space to determine a reduced transformation matrix, where R is smaller than N. N may mean the square of the length of one side of a block to which the transformation is applied or the total number of transformation coefficients corresponding to the block to which the transformation is applied, and the simplification factor may mean an R / N value. The simplification factor may be referred to by various terms such as reduced factor, reduced factor, reduction factor, simplified factor, simple factor, etc. Meanwhile, R may be referred to as a reduced coefficient, but in some cases, the simplification factor may mean R. In addition, in some cases, the simplification factor may mean an N / R value.

[0163] In one embodiment, the simplification factor or simplification coefficient may be signaled via the bitstream, but the embodiment is not limited thereto. For example, predefined values ​​for the simplification factor or simplification coefficient may be stored in each encoding device (200) and decoding device (300), in which case the simplification factor or simplification coefficient may not be signaled separately.

[0164] The size of the simplified transformation matrix according to one embodiment is RxN, which is smaller than the size NxN of the normal transformation matrix, and can be defined as in the following mathematical expression 1.

[0165] [Mathematical Formula 1]

[0166]

[0167] The matrix T in the Reduced Transform block shown in (a) of Fig. 10 is the matrix T of mathematical expression 1. RxNIt can mean. As in (a) of Fig. 10, a simplified transformation matrix T for residual samples for the target block RxN When multiplied, the transformation coefficients for the target block can be derived.

[0168] In one embodiment, when the size of the block to which the transformation is applied is 8x8 and R=16 (i.e., R / N=16 / 64=1 / 4), the RST according to (a) of FIG. 10 can be expressed by a matrix operation as in mathematical expression 2 below. In this case, the memory and multiplication operations can be reduced to approximately 1 / 4 by the simplification factor.

[0169] In this document, matrix operations can be understood as operations that place a matrix on the left side of a column vector and multiply the matrix and the column vector to obtain a column vector.

[0170] [Equation 2]

[0171]

[0172] In mathematical expression 2, r1 to r 64 can represent residual samples for the target block, and more specifically, can be transform coefficients generated by applying a primary transform. The transform coefficients c for the target block as a result of the operation of mathematical expression 2 i can be derived, and c i The derivation process can be as shown in mathematical formula 3.

[0173] [Mathematical formula 3]]

[0174]

[0175] As a result of the operation of mathematical expression 3, the transformation coefficients c1 to c for the target block R This can be derived. That is, when R=16, the transformation coefficients c1 to c for the target block 16This can be derived. If a regular transformation instead of RST were applied and a transformation matrix of size 64x64 (NxN) were multiplied by residual samples of size 64x1 (Nx1), 64 (N) transformation coefficients for the target block would have been derived, but since RST was applied, only 16 (R) transformation coefficients for the target block are derived. Since the total number of transformation coefficients for the target block is reduced from N to R, the amount of data transmitted from the encoding device (200) to the decoding device (300) is reduced, so that the transmission efficiency between the encoding device (200) and the decoding device (300) can be increased.

[0176] In terms of the size of the transformation matrix, the size of a normal transformation matrix is ​​64x64 (NxN), but the size of a simplified transformation matrix is ​​reduced to 16x64 (RxN), so compared to performing a normal transformation, the memory usage when performing LFNST can be reduced by the R / N ratio. In addition, compared to the number of multiplication operations (NxN) when using a normal transformation matrix, the number of multiplication operations can be reduced by the R / N ratio (RxN) when using a simplified transformation matrix.

[0177] In one embodiment, the transform unit (232) of the encoding device (200) can derive transform coefficients for the target block by performing a primary transform and a secondary transform based on an RST on residual samples for the target block. These transform coefficients can be transmitted to the inverse transform unit of the decoding device (300), and the inverse transform unit (322) of the decoding device (300) can derive modified transform coefficients based on an inverse RST (reduced secondary transform) on the transform coefficients, and derive residual samples for the target block based on an inverse primary transform on the modified transform coefficients.

[0178] Inverse RST matrix T according to one embodiment NxRThe size of is NxR, which is smaller than the size of the normal inverse transformation matrix NxN, and is the simplified transformation matrix T shown in mathematical expression 1. RxN and is in a transpose relationship.

[0179] Matrix T in the Reduced Inv. Transform block shown in (b) of Fig. 10 t is the inverse RST matrix T RxN T can mean (superscript T means transpose). As in (b) of Fig. 10, the inverse RST matrix T for the transform coefficients for the target block RxN T When multiplied, modified transform coefficients for the target block or residual samples for the target block can be derived. Inverse RST matrix T RxN T is (T RxN ) T NxR It can also be expressed as

[0180] More specifically, when the inverse RST is applied as a second-order inverse transform, the inverse RST matrix T is applied to the transform coefficients for the target block. RxN T When the transform coefficients for the target block are multiplied, the modified transform coefficients for the target block can be derived. Meanwhile, the inverse RST can be applied as the inverse first-order transform, in which case the inverse RST matrix T is applied to the transform coefficients for the target block. RxN T When multiplied, residual samples for the target block can be derived.

[0181] In one embodiment, when the size of the block to which the inverse transformation is applied is 8x8 and R=16 (i.e., R / N=16 / 64=1 / 4), the RST according to (b) of FIG. 10 can be expressed by a matrix operation as in mathematical expression 4 below.

[0182] [Equation 4]

[0183]

[0184] In mathematical formula 4, c1 to c 16 can represent the transform coefficients for the target block. The result of the operation of Equation 4 represents the modified transform coefficients for the target block or the residual samples for the target block. i can be derived, and r i The derivation process can be as shown in mathematical formula 5.

[0185] [Equation 5]

[0186]

[0187] As a result of the operation of mathematical expression 5, r1 to r represent modified transform coefficients for the target block or residual samples for the target block. N This can be derived. In terms of the size of the inverse transform matrix, the size of the normal inverse transform matrix is ​​64x64 (NxN), but the size of the simplified inverse transform matrix is ​​reduced to 64x16 (NxR), so compared to performing the normal inverse transform, the memory usage when performing the inverse RST can be reduced by the R / N ratio. In addition, compared to the number of multiplication operations NxN when using the normal inverse transform matrix, the number of multiplication operations can be reduced by the R / N ratio (NxR) when using the simplified inverse transform matrix.

[0188] Meanwhile, according to one embodiment of the present document, in the transformation of the encoding process, instead of the 16 x 64 transformation kernel matrix for the 64 data constituting the 8 x 8 region, only 48 data can be selected and a maximum 16 x 48 transformation kernel matrix can be applied. Here, “maximum” means that the maximum value of m is 16 for the m x 48 transformation kernel matrix that can generate m coefficients. That is, when RST is performed by applying the m x 48 transformation kernel matrix (m ≤ 16) to the 8 x 8 region, 48 data can be input and m coefficients can be generated. When m is 16, 48 data are input and 16 coefficients are generated. That is, when 48 data form a 48 x 1 vector, a 16 x 1 vector can be generated by sequentially multiplying the 16 x 48 matrix and the 48 x 1 vector. At this time, a 48 x 1 vector can be constructed by appropriately arranging the 48 data that make up the 8 x 8 area. For example, a 48 x 1 vector can be constructed based on the 48 data that make up the area excluding the 4 x 4 area at the bottom right among the 8 x 8 areas. At this time, if a matrix operation is performed by applying a maximum 16 x 48 transformation kernel matrix, 16 modified transformation coefficients are generated. The 16 modified transformation coefficients can be arranged in the upper left 4 x 4 area according to the scanning order, and the upper right 4 x 4 area and the lower left 4 x 4 area can be filled with 0.

[0189] The inverse transform of the decoding process can use the transposed matrix of the transform kernel matrix described above. That is, when the inverse RST or LFNST is performed as the inverse transform process performed in the decoding device, the input coefficient data to which the inverse RST is to be applied is configured as a one-dimensional vector according to a predetermined arrangement order, and the modified coefficient vector obtained by multiplying the one-dimensional vector by the corresponding inverse RST matrix from the left can be arranged in a two-dimensional block according to a predetermined arrangement order.

[0190] In summary, during the transformation process, when RST or LFNST is applied to an 8x8 region, a matrix operation is performed between the 48 transformation coefficients in the upper left, upper right, and lower left regions of the 8x8 region, excluding the lower right region, and the 16x48 transformation kernel matrix. For the matrix operation, the 48 transformation coefficients are input as a one-dimensional array. When this matrix operation is performed, 16 modified transformation coefficients are derived, and the modified transformation coefficients can be arranged in the upper left region of the 8x8 region.

[0191] Conversely, in the inverse transformation process, when inverse RST or LFNST is applied to the 8x8 region, the 16 transform coefficients corresponding to the upper left of the 8x8 region among the transform coefficients of the 8x8 region can be input in the form of a one-dimensional array according to the scanning order and can be subjected to matrix operation with the 48 x 16 transform kernel matrix. That is, the matrix operation in this case can be expressed as (48 x 16 matrix) * (16x1 transform coefficient vector) = (48 x 1 modified transform coefficient vector). Here, since an nx1 vector can be interpreted as having the same meaning as an nx1 matrix, it can also be expressed as an nx1 column vector. In addition, * indicates a matrix multiplication operation. When this matrix operation is performed, 48 modified transform coefficients can be derived, and the 48 modified transform coefficients can be arranged in the upper left, upper right, and lower left regions, excluding the lower right region of the 8x8 region.

[0192] For example, syntax elements for MIP can be signaled in the coding unit syntax table as shown in Table 4.

[0193]

[0194]

[0195]

[0196] The intra_mip_flag[ x0 ][ y0 ] signaled in the coding unit syntax table of Table 4 is flag information indicating whether the MIP intra mode is applied to the coding unit.

[0197] This intra_mip_flag[ x0 ][ y0 ] is referenced in several places in the spec text, as shown in Table 4 and Table 5, in particular, intra_mip_flag values ​​for locations other than (x0, y0) are referenced, such as intra_mip_flag[ xCb + cbWidth / 2 ][ yCb + cbHeight / 2 ].

[0198] Here, x0 and y0 represent the x-coordinate and y-coordinate, respectively, relative to the luma picture. The x-coordinate increases in luma sample units from left to right when the leftmost position of the luma picture is defined as 0, and the y-coordinate increases in luma sample units from top to bottom when the topmost position of the luma picture is defined as 0. The x-coordinate and y-coordinate can be expressed in a two-dimensional coordinate format such as (x, y).

[0199] However, intra_mip_flag[ x0 ][ y0 ] can be considered valid only for the position (x0, y0), which corresponds to the upper left position of the coding unit (CU) where intra_mip_flag[ x0 ][ y0 ] is signaled. In other words, it can be considered that intra_mip_flag[ x0 ][ y0 ] is signaled only for the upper left position (x0, y0), which is the representative position within the coding unit for each coding unit.

[0200] Meanwhile, in Table 5, since the intra_mip_flag values ​​for other locations as well as the upper left location (x0, y0) within the coding unit are referenced (underlined part), it is necessary to fill in the information of the intra_mip_flag values ​​for locations other than the upper left location.

[0201]

[0202]

[0203]

[0204]

[0205] As shown in Tables 4 and 5, intra_mip_flag is defined as a syntax element, and as in the semantics of intra_mip_flag presented in Table 5 (7.4.11.5 Coding unit semantics), if intra_mip_flag does not exist, it is inferred to be 0.

[0206] The values ​​of these intra_mip_flag can be used when deriving the intra prediction mode (8.4.1, 8.4.2), for example, intra_mip_flag values ​​for neighboring blocks or specific locations within neighboring blocks can be used as described in 8.4.2 (intra_mip_flag[ xNbX ][ yNbX ] is equal to 1).

[0207] Additionally, as described in 8.4.3, when deriving the intra prediction mode of a chroma block, the intra_mip_flag value for the position of the corresponding luma block can be used (- The chroma intra prediction mode IntraPredModeC[ xCb ][ yCb ] is set equal to IntraPredModeY[ xCb + cbWidth / 2 ][ yCb + cbHeight / 2 ]).

[0208] In addition, these intra_mip_flag values ​​are utilized not only in intra prediction but also in the transformation process (8.7.4.1 - When intra_mip_flag[ xTbY ][ yTbY ] is equal to 1 and cIdx is equal to 0, predModeIntra is set equal to INTRA_PLANAR), and the intra_mip_flag values ​​for the surrounding blocks can be used in the process of deriving the context index of the target block to be coded (Table 132 Specification of ctxInc using left and above syntax elements).

[0209] Therefore, there may be ambiguity in how to fill in the intra_mip_flag array variable values ​​for positions other than (x0, y0) by considering intra_mip_flag itself as a two-dimensional array variable. That is, since the semantics state that if intra_mip_flag[ x0 ][ y0 ] does not exist, it is inferred to be 0, so it may be ambiguous, that is, uncertain, whether any non-zero value can be filled in positions in the intra_mip_flag array that are not yet filled with values.

[0210] Therefore, as an example, it may be proposed to define a separate two-dimensional array such as IntraLumaMipFlag[ x ][ y ] as described in Table 6 and utilize it in the subsequent image coding process.

[0211]

[0212] In Table 6, (x0, y0) represents the upper left position of the currently coded coding unit (CU), and cbWidth and cbHeight represent the horizontal and vertical lengths of the coding unit, respectively. In addition, “x = x0..x0 + cbWidth - 1” means that the x-coordinate value changes from x0 to x0 + cbWidth - 1, and “y = y0..y0 + cbHeight - 1” means that the y-coordinate value changes from y0 to y0 + cbHeight - 1. Therefore, in the IntraLumaMipFlag[ x ][ y ] array in Table 6, the region corresponding to the coding unit is filled with the intra_mip_flag[ x0 ][ y0 ] value.

[0213] As an example, all parts of the current VVC specification text that reference intra_mip_flag information (underlined parts) can be replaced or modified with the IntraLumaMipFlag variable as shown in Table 7.

[0214]

[0215]

[0216]

[0217]

[0218] In cases where it is certain that the IntraLumaMipFlag information for the upper-left position within a coding unit is referenced in Table 7, the existing intra_mip_flag can be used as is. Extracting only the portions of Table 7 where the existing intra_mip_flag can be used as is, the result is as shown in Table 8.

[0219]

[0220] Meanwhile, the same problem can occur in the current VVC specification text for intra_subpartitions_mode_flag in addition to intra_mip_flag in Table 4. That is, it refers to intra_subpartitions_mode_flag information for locations other than (x0, y0), which is the upper left position within the coding unit, as shown in Table 9 (underlined portion).

[0221] Therefore, in a similar way to the IntraLumaMipFlag variable, we can define a two-dimensional array variable called IntraSubPartitionsModeFlag[ x ][ y ], which can be configured to fill in the necessary information for all positions within a coding unit and then reference an appropriate value for any position. That is, we can fill in the value of intra_subpartitions_mode_flag[ x0 ][ y0 ] for all positions within a coding unit.

[0222] Table 10 shows that the parts that reference intra_subpartitions_mode_flag (underlined) using the IntraSubPartitionsModeFlag variable have been replaced with the IntraSubPartitionsModeFlag variable. In the case of IntraSubPartitionsModeFlag, if it also refers to information about the upper-left position within a coding unit, it can be configured to refer to intra_subpartitions_mode_flag as is.

[0223] In another example, the variable IntraLumaMipFlag or the variable IntraSubPartitionModeFlag presented in this embodiment may have different variable names, i.e., they may be represented or named as different variables, for example, they may be represented as variable MipFlag instead of variable IntraLumaMipFlag.

[0224]

[0225]

[0226] The following drawings are intended to illustrate specific examples of the present specification. The names of specific devices and the names of specific signals, messages, and fields depicted in the drawings are provided for illustrative purposes only, and the technical features of this specification are not limited to the specific names used in the drawings.

[0227] FIG. 11 is a flowchart illustrating the operation of a video decoding device according to one embodiment of the present document.

[0228] Each step disclosed in Fig. 11 is based on some of the contents described above in Figs. 5 to 10. Therefore, specific details that overlap with the contents described above in Figs. 3, 5 to 10 will be omitted or briefly explained.

[0229] A decoding device (300) according to one embodiment can receive information about an intra prediction mode, residual information, etc. from a bitstream, and can receive image information including intra prediction type information including, for example, an intra MIP syntax element (intra_mip_flag) for a first target block (S1110).

[0230] More specifically, the decoding device (300) can decode information about quantized transform coefficients for a current block from a bitstream, and can derive quantized transform coefficients for a target block based on the information about the quantized transform coefficients for the current block. The information about the quantized transform coefficients for the target block can be included in a Sequence Parameter Set (SPS) or a slice header, and can include at least one of information about whether a simplification transform (RST) is applied, information about a simplification factor, information about a minimum transform size for applying a simplification transform, information about a maximum transform size for applying a simplification transform, a simplification inverse transform size, and information about a transform index indicating one of the transform kernel matrices included in the transform set.

[0231] Additionally, the decoding device can further receive information about the intra prediction mode for the current block and whether ISP is applied to the current block. The decoding device can derive whether the current block is divided into a predetermined number of sub-partition transform blocks by receiving and parsing flag information indicating whether ISP coding or ISP mode is applied. Here, the current block may be a coding block. Furthermore, the decoding device can derive the size and number of sub-partition blocks into which the current block is divided through flag information indicating the direction in which the current block is divided.

[0232] The decoding device (300) can decode the intra MIP syntax element for the first target block to derive the value of the intra MIP syntax element (S1120).

[0233] The decoding device can set a variable MIP flag for a predetermined specific area identical to the area of ​​the first target block based on the value of the intra MIP syntax element (S1130).

[0234] As described with reference to Table 6, in the semantics for the intra MIP syntax element, a variable MIP flag (IntraLumaMipFlag[ x ][ y ]) is set, and the variable MIP flag can be utilized during the subsequent decoding process for the image.

[0235] The specific area can be set to be the same as the area where the sample is located within the first target block (x = x0..x0 + cbWidth and -1, y = y0..y0 + cbHeight - 1), where cbWidth and cbHeight represent the width and height of the first target block.

[0236] Meanwhile, such variable MIP flags may be set for a specific region based on whether the tree type of the first target block is not dual tree chroma. That is, the variable MIP flags may be set to the value of the received intra MIP syntax element for a specific region only when the tree type of the first target block is not dual tree chroma but single tree or dual tree luma.

[0237] The intra MIP syntax element intra_mip_flag is signaled only when the tree type of the corresponding coding block is single tree and dual tree luma, and is not signaled when it is dual tree chroma, so it is inferred to be 0. Therefore, if the tree type of the first target block is dual tree chroma, the intra_mip_flag value is 0. In intra prediction or transformation, when deriving the intra prediction mode for the chroma block, the intra prediction mode of the luma block is borrowed and used, and the newly set variable MIP flag can be used at this time. If the setting condition of the variable MIP flag does not include a condition that it is set only for 'single tree and dual tree luma', the variable MIP flag can be set even in dual tree chroma. In this case, since the intra_mip_flag value is 0, the variable MIP flag does not include information about the luma component, so the luma information cannot be utilized when deriving the intra prediction mode for the chroma block. To avoid this problem, the variable MIP flag can be set only when the corresponding coding block, i.e. the first target block, is not a dual tree chroma.

[0238] The decoding device can derive the intra prediction mode of the second target block based on the variable MIP flag of the first target block (S1140).

[0239] Figures 12a and 12b illustrate utilizing the variable MIP flag of the first target block to derive the intra prediction mode of the second target block.

[0240] As shown in Fig. 12a, the first target block may be a left peripheral block of the second target block, and the specific region may include a sample position of (xCb - 1, yCb + cbHeight - 1). In this case, (xCb, yCb) is the upper left sample position of the second target block, and cbHeight represents the height of the second target block.

[0241] That is, a candidate intra prediction mode for a second target block can be derived based on a variable MIP flag of a sample position of ( xCb - 1, yCb + cbHeight - 1 ) included in a specific region of a first target block, and an intra prediction mode of the second target block can be derived based on the candidate intra prediction mode.

[0242] As another example, as in FIG. 12b, the first target block may be an upper peripheral block of the second target block, and the specific region may include a sample position of (xCb + cbWidth - 1, yCb - 1). In this case, (xCb, yCb) is the upper left sample position of the second target block, and cbWidth represents the width of the second target block.

[0243] That is, a candidate intra prediction mode for a second target block can be derived based on a variable MIP flag of a sample position of (xCb + cbWidth - 1, yCb -1) included in a specific region of a first target block, and an intra prediction mode of the second target block can be derived based on the candidate intra prediction mode.

[0244] Additionally, according to another example, the second target block may include a chroma block, and the first target block may be a luma block related to the chroma block. As described above, an intra prediction mode for the corresponding chroma block may be derived based on the variable MIP flag value for the luma block.

[0245] In this document, a picture / video may include a luma component array, and in some cases, may further include two chroma component (cb, cr) arrays. That is, one pixel of a picture / video may include a luma sample and a chroma sample (cb, cr).

[0246] A color format can indicate the composition format of luma components and chroma components (cb, cr), and may also be called a chroma format or chroma array type. The color format (or chroma format) can be predetermined or signaled adaptively. For example, a chroma format can be signaled based on at least one of chroma_format_idc and separate_color_plane_flag, as shown in Table 11.

[0247]

[0248] Figure 13 shows the composition of samples according to the chroma format of Table 11.

[0249] 4:2:0 sampling with a chroma format index of 1, i.e., a chroma array type of 1, indicates that the height and width of the two chroma arrays are each half the height and width of the luma array, and 4:2:2 sampling with a chroma format index of 2, i.e., a chroma array type of 2, indicates that the height of the two chroma arrays is the same as the height of the luma array, and the width is half the width of the luma array.

[0250] 4:4:4 sampling with a chroma format index of 3, i.e. a chroma array type of 3, means that the height and width of the chroma array are the same as the height and width of the luma array.

[0251] For example, based on the tree type of the second target block not being a single tree or the chroma array type not being 3, the specific region may include sample positions of (xCb + cbWidth / 2, yCb + cbHeight / 2), where (xCb, yCb) represents the upper left position of the chroma block in luma sample units, cbWidth represents the width of a corresponding luma block corresponding to the chroma block, and cbHeight represents the height of the corresponding luma block.

[0252] Figures 14a to 14c illustrate utilizing the variable MIP flag of the corresponding luma block, which is the first target block, to derive the intra prediction mode of the chroma block, which is the second target block. Figures 14a to 14c illustrate sample locations (xCb + cbWidth / 2, yCb + cbHeight / 2) included in a specific region according to the tree type and color format of the luma block and the chroma block.

[0253] Figure 14a illustrates a luma block and a chroma block of single tree type and a color format of 4:2:0. That is, it represents a case where the condition that the chroma array type is not 3 is satisfied among the conditions that “the tree type of the second target block is not a single tree or the chroma array type is not 3.”

[0254] The first sample position (Ⅰ) of the chroma block indicates the upper left position of the chroma block, and the second sample position (Ⅱ(xCb, yCb)) of the luma block indicates the upper left position of the chroma block in luma sample units. cbWidth is the width of the corresponding luma block corresponding to the chroma block, and cbHeight indicates the height of the corresponding luma block. Since the color format is 4:2:0, the width and height (cbWidth and cbHeight) of the corresponding luma block corresponding to the chroma block are twice the width and height (cbWidth / 2 and cbHeight / 2) of the chroma block.

[0255] The variable MIP flag value of the third sample position (Ⅲ) indicated by (xCb + cbWidth / 2, yCb + cbHeight / 2) in the luma block can be used to derive the intra prediction mode of the chroma block. That is, a candidate intra prediction mode for the chroma block, which is the second target block, can be derived based on the variable MIP flag of the sample position of (xCb + cbWidth / 2, yCb + cbHeight / 2) included in the luma block, which is the first target block, and the intra prediction mode of the chroma block can be derived based on the candidate intra prediction mode.

[0256] Figure 14b illustrates a luma block and a chroma block of dual tree type and a color format of 4:4:4. That is, it shows a case where the condition that the tree type is not a single tree is satisfied among the conditions that “the tree type of the second target block is not a single tree or the chroma array type is not 3”.

[0257] As shown, the chroma block for the luma block is indicated by a dotted line, and since the color format is 4:4:4, the width and height of the luma array and the chroma array are the same. The luma block is not split, but the chroma block is split and coded.

[0258] If the lower right block among the divided chroma blocks is the second target block to be predicted, the first sample position (Ⅰ) indicates the upper left position of the second target block as shown, and the second sample position (Ⅱ(xCb, yCb)) indicates the upper left position of the chroma block in luma sample units.

[0259] Additionally, since the color format is 4:4:4, the third sample location (Ⅲ) indicated by (xCb + cbWidth / 2, yCb + cbHeight / 2) within the luma block is located within the corresponding luma block located at the lower right of the luma block.

[0260] The decoding device can derive the intra prediction mode of the chroma block based on the variable MIP flag value of the third sample position (Ⅲ). That is, a candidate intra prediction mode for the chroma block, which is the second target block, can be derived based on the variable MIP flag of the sample position of (xCb + cbWidth / 2, yCb + cbHeight / 2) included in the luma block, which is the first target block, and an intra prediction mode of the chroma block can be derived based on the candidate intra prediction mode.

[0261] Fig. 14c illustrates a luma block and a chroma block of dual tree type and a color format of 4:2:0. That is, it represents a case where both of the conditions of “the tree type of the second target block is not a single tree or the chroma array type is not 3” are satisfied. In other words, Fig. 14c illustrates a case where the tree type of the second target block is not a single tree and the chroma array type is not 3.

[0262] The first sample position (Ⅰ) of the chroma block indicates the upper left position of the chroma block, and the second sample position (Ⅱ(xCb, yCb)) of the luma block indicates the upper left position of the chroma block in luma sample units. cbWidth is the width of the corresponding luma block corresponding to the chroma block, and cbHeight indicates the height of the corresponding luma block.

[0263] Therefore, the variable MIP flag value of the third sample position (Ⅲ) indicated by (xCb + cbWidth / 2, yCb + cbHeight / 2) in the luma block can be used to derive the intra prediction mode of the chroma block. That is, a candidate intra prediction mode for the chroma block, which is the second target block, can be derived based on the variable MIP flag of the sample position of (xCb + cbWidth / 2, yCb + cbHeight / 2) included in the luma block, which is the first target block, and the intra prediction mode of the chroma block can be derived based on the candidate intra prediction mode.

[0264] The decoding device can derive a prediction sample of the second target block based on the intra prediction mode of the second target block (S1150) and generate a restoration block based on the prediction sample (S1160).

[0265] The decoding device can generate a reconstructed block based on the received residual information and prediction samples. The decoding device can derive transform coefficients through a transformation process based on the residual information, and if the intra prediction mode of the second target block is required during the transformation process, the variable MIP flag value of the first target block can be utilized.

[0266] Additionally, according to another example, if the intra prediction type information includes a flag syntax element (intra_subpartitions_mode_flag) for an intra sub-partition (ISP) mode for the first target block, the decoding device can utilize a variable value set based on the intra_subpartitions_mode_flag value to derive the intra prediction mode of the second target block.

[0267] That is, the decoding device can derive the value of the flag syntax element (intra_subpartitions_mode_flag), set the variable ISP flag (IntraSubPartitionsModeFlag) for a preset specific region identical to the region of the first target block based on the value of the flag syntax element, and derive the intra prediction mode of the second target block based on the variable ISP flag value.

[0268] The variable ISP flag may also be set for a specific region based on whether the tree type of the first target block is not dual tree chroma. That is, the variable ISP flag may be set to the value of the received flag syntax element for a specific region only when the tree type of the first target block is not dual tree chroma but single tree or dual tree luma.

[0269] The following drawings are intended to illustrate specific examples of the present specification. The names of specific devices and the names of specific signals, messages, and fields depicted in the drawings are provided for illustrative purposes only, and the technical features of this specification are not limited to the specific names used in the drawings.

[0270] FIG. 15 is a flowchart illustrating the operation of a video encoding device according to one embodiment of the present document.

[0271] Each step disclosed in Fig. 15 is based on some of the contents described above in Figs. 5 to 10. Therefore, specific details that overlap with the contents described above in Figs. 2 and 5 to 10 will be omitted or briefly explained.

[0272] An encoding device (200) according to one embodiment can derive a prediction sample for the first target block and derive a value of an intra MIP flag for the first target block when an intra MIP mode is applied to the first target block (S1510).

[0273] The encoding device can perform prediction on a per-subpartition transform block basis when ISP is applied to the current block.

[0274] The encoding device can determine whether to apply ISP coding or ISP mode to the current block, i.e., the coding block, and, based on the determination result, determine in which direction the current block is to be divided and derive the size and number of sub-blocks into which the current block is to be divided.

[0275] The same intra prediction mode is applied to the sub-partition transform blocks divided from the current block, and the encoding device can derive prediction samples for each sub-partition transform block. That is, the encoding device sequentially performs intra prediction according to the division shape of the sub-partition transform blocks, for example, horizontally or vertically, from left to right, or from top to bottom. For the leftmost or topmost sub-block, the reconstructed pixels of the already coded coding block are referenced as in a conventional intra prediction method. In addition, for each side of the subsequent internal sub-partition transform block, if it is not adjacent to the previous sub-partition transform block, the reconstructed pixels of the already coded adjacent coding block are referenced as in a conventional intra prediction method in order to derive reference pixels adjacent to the corresponding side.

[0276] The encoding device can set a variable MIP flag for a predetermined specific area identical to the area of ​​the first target block based on the value of the intra MIP flag (S1520).

[0277] As described with reference to Table 6, in the semantics for the intra MIP syntax element, a variable MIP flag (IntraLumaMipFlag[ x ][ y ]) is set, and the variable MIP flag can be utilized during the subsequent decoding process for the image.

[0278] The specific area can be set to be the same as the area where the sample is located within the first target block (x = x0..x0 + cbWidth and -1, y = y0..y0 + cbHeight - 1), where cbWidth and cbHeight represent the width and height of the first target block.

[0279] Meanwhile, such variable MIP flags may be set for a specific region based on whether the tree type of the first target block is not dual tree chroma. That is, the variable MIP flags may be set to the value of the received intra MIP syntax element for a specific region only when the tree type of the first target block is not dual tree chroma but single tree or dual tree luma.

[0280] The intra MIP syntax element intra_mip_flag is signaled only when the tree type of the corresponding coding block is single tree and dual tree luma, and is not signaled when it is dual tree chroma, so it is inferred to be 0. Therefore, if the tree type of the first target block is dual tree chroma, the intra_mip_flag value is 0. In intra prediction or transformation, when deriving the intra prediction mode for the chroma block, the intra prediction mode of the luma block is borrowed and used, and the newly set variable MIP flag can be used at this time. If the setting condition of the variable MIP flag does not include a condition that it is set only for 'single tree and dual tree luma', the variable MIP flag can be set even in dual tree chroma. In this case, since the intra_mip_flag value is 0, the variable MIP flag does not include information about the luma component, so the luma information cannot be utilized when deriving the intra prediction mode for the chroma block. To avoid this problem, the variable MIP flag can be set only when the corresponding coding block, i.e. the first target block, is not a dual tree chroma.

[0281] The encoding device can derive the intra prediction mode of the second target block based on the variable MIP flag of the first target block (S1530).

[0282] The parts described with reference to FIGS. 12a to 14c can be applied to the intra prediction mode derivation process performed in the encoding device.

[0283] The encoding device can derive prediction samples of the second target block based on the intra prediction mode of the second target block derived in this way (S1540), and can derive residual samples for the second target block based on these prediction samples (S1550).

[0284] Additionally, as described above, if the intra prediction type information for the first target block is the intra sub-partition (ISP) mode, a variable ISP flag value may be set for the first target block based on a flag value indicating whether the first target block is in the intra sub-partition (ISP) mode. The intra prediction mode of the second target block may be derived based on the variable ISP flag value.

[0285] The encoding device can encode and output transform coefficient information generated based on the intra MIP flag and residual sample (S1560).

[0286] Quantization can be performed based on the modified transform coefficients for the current block to derive quantized transform coefficients, and image information including an intra MIP flag can be generated and output.

[0287] An encoding device can generate residual information including information about quantized transform coefficients. The residual information can include the aforementioned transform-related information / syntax elements. The encoding device can encode image / video information including the residual information and output it in the form of a bitstream.

[0288] More specifically, the encoding device (200) can generate information about quantized transform coefficients and encode information about the generated quantized transform coefficients.

[0289] In this document, at least one of quantization / dequantization and / or transformation / inverse transformation may be omitted. If the quantization / dequantization is omitted, the quantized transform coefficient may be called a transform coefficient. If the transformation / inverse transformation is omitted, the transform coefficient may be called a coefficient or a residual coefficient, or may still be called a transform coefficient for the sake of consistency of expression.

[0290] In addition, in this document, the quantized transform coefficients and transform coefficients may be referred to as transform coefficients and scaled transform coefficients, respectively. In this case, the residual information may include information about the transform coefficient(s), and the information about the transform coefficient(s) may be signaled via residual coding syntax. Transform coefficients may be derived based on the residual information (or information about the transform coefficient(s)), and scaled transform coefficients may be derived through inverse transformation (scaling) of the transform coefficients. Residual samples may be derived based on inverse transformation (transformation) of the scaled transform coefficients. This may be similarly applied / expressed in other parts of this document.

[0291] While the methods described in the above-described embodiments are described based on a flowchart as a series of steps or blocks, this document is not limited to the order of the steps, and some steps may occur in a different order or simultaneously with other steps described above. Furthermore, those skilled in the art will appreciate that the steps depicted in the flowchart are not exclusive, and that other steps may be included, or one or more steps in the flowchart may be deleted, without affecting the scope of this document.

[0292] The method according to the present document described above can be implemented in the form of software, and the encoding device and / or decoding device according to the present document can be included in a device that performs image processing, such as a TV, a computer, a smartphone, a set-top box, a display device, etc.

[0293] When the embodiments in this document are implemented as software, the above-described method can be implemented as a module (process, function, etc.) that performs the above-described function. The module can be stored in memory and executed by a processor. The memory can be internal or external to the processor and can be connected to the processor by various well-known means. The processor can include an application-specific integrated circuit (ASIC), another chipset, logic circuit, and / or data processing device. The memory can include a read-only memory (ROM), a random access memory (RAM), flash memory, a memory card, a storage medium, and / or other storage devices. That is, the embodiments described in this document can be implemented and performed on a processor, a microprocessor, a controller, or a chip. For example, the functional units illustrated in each drawing can be implemented and performed on a computer, a processor, a microprocessor, a controller, or a chip.

[0294] In addition, the decoding device and encoding device to which this document applies may be included in a multimedia broadcasting transmitting and receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video conversation device, a real-time communication device such as a video communication, a mobile streaming device, a storage medium, a camcorder, a video-on-demand (VoD) service providing device, an OTT video (Over the top video) device, an Internet streaming service providing device, a three-dimensional (3D) video device, a video phone video device, and a medical video device, and may be used to process a video signal or a data signal. For example, the 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, a DVR (Digital Video Recorder), and the like.

[0295] In addition, the processing method to which this document applies can be produced in the form of a computer-executable program and stored in a computer-readable recording medium. Multimedia data having a data structure according to this document can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices that store computer-readable data. The computer-readable recording medium can include, for example, Blu-ray Disc (BD), Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. In addition, the computer-readable recording medium includes media implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, a bitstream generated by an encoding method can be stored in a computer-readable recording medium or transmitted via a wired or wireless communication network. In addition, the embodiments of the present document can be implemented as a computer program product by program code, and the program code can be executed on a computer by the embodiments of the present document. The above program code can be stored on a computer-readable carrier.

[0296] The claims set forth in this specification may be combined in various ways. For example, the technical features of the method claims of this specification may be combined and implemented as a device, and the technical features of the device claims of this specification may be combined and implemented as a method. Furthermore, the technical features of the method claims and the technical features of the device claims of this specification may be combined and implemented as a device, and the technical features of the method claims and the technical features of the device claims of this specification may be combined and implemented as a method.

Claims

1. In a video decoding method performed by a decoding device, Receiving image information including intra prediction type information from a bitstream, wherein the intra prediction type information includes an intra MIP syntax element for a first target block, A step of deriving a value of the above intra MIP syntax element; A step of setting a variable MIP flag for a predetermined specific area identical to an area of ​​the first target block based on the value of the intra MIP syntax element; A step of deriving an intra prediction mode of a second target block; A step of deriving a prediction sample of the second target block based on the intra prediction mode of the second target block; A step of generating a restoration block based on the above prediction sample, An image decoding method, characterized in that the intra prediction mode of the second target block is derived based on the variable MIP flag of the first target block.

2. In paragraph 1, The above first target block is a left peripheral block of the above second target block, The step of deriving the intra prediction mode of the second target block is: A step of deriving a candidate intra prediction mode based on the above variable MIP flag; An image decoding method, characterized by comprising a step of deriving the intra prediction mode of the second target block based on the candidate intra prediction mode.

3. In paragraph 2, The above specific region contains the sample locations of ( xCb - 1, yCb + cbHeight - 1 ), An image decoding method, characterized in that (xCb, yCb) is an upper left sample position of the second target block, and cbHeight represents the height of the second target block.

4. In paragraph 1, The above first target block is an upper peripheral block of the above second target block, The step of deriving the intra prediction mode of the second target block is: A step of deriving a candidate intra prediction mode based on the above variable MIP flag; An image decoding method, characterized by comprising a step of deriving the intra prediction mode of the second target block based on the candidate intra prediction mode.

5. In paragraph 4, The above specific region contains sample locations of (xCb + cbWidth - 1, yCb - 1), An image decoding method, characterized in that (xCb, yCb) is an upper left sample position of the second target block, and cbWidth represents the width of the second target block.

6. In paragraph 1, The second target block includes a chroma block, and the first target block is a luma block related to the chroma block. The step of deriving the intra prediction mode of the second target block is: A step of deriving a corresponding luma intra prediction mode based on the above variable MIP flag; An image decoding method, characterized by comprising a step of deriving the intra prediction mode of the second target block based on the corresponding luma intra prediction mode.

7. In paragraph 6, Based on the tree type of the second target block being not a single tree or the chroma array type being not 3, the specific region includes sample positions of (xCb + cbWidth / 2, yCb + cbHeight / 2), A video decoding method, characterized in that (xCb, yCb) represents the upper left position of the chroma block in the luma sample unit, cbWidth represents the width of a corresponding luma block corresponding to the chroma block, and cbHeight represents the height of the corresponding luma block.

8. In paragraph 1, An image decoding method, characterized in that the variable MIP flag is set for the specific region based on the tree type of the first target block being not a dual tree chroma.

9. In a video encoding method performed by a video encoding device, When the intra MIP mode is applied to the first target block, a step of deriving a value of the intra MIP flag for the first target block; A step of setting a variable MIP flag for a predetermined specific area identical to an area of ​​the first target block based on the value of the intra MIP flag; A step of deriving an intra prediction mode of the second target block; A step of deriving a prediction sample of the second target block based on the intra prediction mode of the second target block; A step of deriving residual samples for the second target block based on the above prediction sample; Including a step of encoding and outputting transform coefficient information generated based on the intra MIP flag and the residual sample, A video encoding method, characterized in that the intra prediction mode of the second target block is derived based on the variable MIP flag of the first target block.

10. In paragraph 9, The above first target block is a left peripheral block of the above second target block, The step of deriving the intra prediction mode of the second target block is: A step of deriving a candidate intra prediction mode based on the above variable MIP flag; A step of deriving the intra prediction mode of the second target block based on the candidate intra prediction mode, The above specific region contains the sample locations of ( xCb - 1, yCb + cbHeight - 1 ), An image encoding method, characterized in that (xCb, yCb) is the upper left sample position of the second target block, and cbHeight represents the height of the second target block.

11. In paragraph 9, The above first target block is an upper peripheral block of the above second target block, The step of deriving the intra prediction mode of the second target block is: A step of deriving a candidate intra prediction mode based on the above variable MIP flag; A step of deriving the intra prediction mode of the second target block based on the candidate intra prediction mode, The above specific region contains sample locations of (xCb + cbWidth - 1, yCb - 1), An image encoding method, characterized in that (xCb, yCb) is an upper left sample position of the second target block, and cbWidth represents the width of the second target block.

12. In paragraph 9, The second target block includes a chroma block, and the first target block is a luma block related to the chroma block. The step of deriving the intra prediction mode of the second target block is: A step of deriving a corresponding luma intra prediction mode based on the above variable MIP flag; A video encoding method, characterized by comprising a step of deriving the intra prediction mode of the second target block based on the corresponding luma intra prediction mode.

13. In paragraph 12, Based on the tree type of the second target block being not a single tree or the chroma array type being not 3, the specific region includes sample positions of (xCb + cbWidth / 2, yCb + cbHeight / 2), A video encoding method, characterized in that (xCb, yCb) represents the upper left position of the chroma block in the luma sample unit, cbWidth represents the width of the corresponding luma block corresponding to the chroma block, and cbHeight represents the height of the corresponding luma block.

14. In paragraph 9, A video encoding method characterized in that the variable MIP flag is set for the specific region based on the tree type of the first target block being not a dual tree chroma.

15. A computer-readable digital storage medium storing instruction information causing an image decoding method to be performed, wherein the image decoding method comprises: Receiving image information including intra prediction type information from a bitstream, wherein the intra prediction type information includes an intra MIP syntax element for a first target block, A step of deriving a value of the above intra MIP syntax element; A step of setting a variable MIP flag for a predetermined specific area identical to an area of ​​the first target block based on the value of the intra MIP syntax element; A step of deriving an intra prediction mode of a second target block; A step of deriving a prediction sample of the second target block based on the intra prediction mode of the second target block; A step of generating a restoration block based on the above prediction sample, A digital storage medium, characterized in that the intra prediction mode of the second target block is derived based on the variable MIP flag of the first target block.

Images