Video signal processing method and device therefor

Abstract

This video signal decoding device comprises a processor, wherein the processor acquires a luma block vector of a first luma component block of the current block, acquires, on the basis of the luma block vector, a chroma reference block, which is a chroma component block of a reference block, and predicts a first chroma component block of the current block on the basis of the chroma reference block, wherein the first luma component block and the first chroma component block can correspond to each other.

Description

Video signal processing method and device therefor

[0001] The present invention relates to a method and device for processing a video signal, and more particularly, to a method and device for processing a video signal for encoding or decoding a video signal.

[0002] Compression coding refers to a series of signal processing techniques for transmitting digitized information over communication lines or storing it in a format suitable for storage media. Objects subject to compression coding include audio, video, and text, and the technology that performs compression coding on video in particular is called video compression. Compression coding of video signals is achieved by removing redundant information by considering spatial, temporal, and probabilistic correlations. However, with the recent advancements in various media and data transmission media, there is a growing demand for more efficient video signal processing methods and devices.

[0003] The purpose of this specification is to provide a video signal processing method and a device therefor to improve the coding efficiency of a video signal.

[0004] The present specification provides a video signal processing method and a device therefor.

[0005] In the present specification, a video signal decoding device includes a processor, wherein the processor obtains a luma block vector of a first luma component block of a current block, obtains a chroma reference block which is a chroma component block based on the luma block vector, and predicts the first chroma component block of the current block based on the chroma reference block, wherein the first luma component block and the first chroma component block may correspond to each other.

[0006] Additionally, the processor of the video signal decoding device can obtain a linear model for predicting the first chroma component block, obtain a non-linear model for predicting the first chroma component block, and predict the first chroma component block based on the linear model and the non-linear model.

[0007] Additionally, the processor of the video signal decoding device can obtain a first peripheral block of a luma reference block, which is a luma component block of the reference block, obtain a second peripheral block of the chroma reference block, obtain a CCCM (Convolutional cross-component intra prediction model) based on the first peripheral block and the second peripheral block, and predict the first chroma component block based on the CCCM.

[0008] In addition, in the present specification, a video signal encoding device includes a processor, wherein the processor can obtain a bitstream decoded by a decoding method. In addition, the bitstream can be stored in a computer-readable, non-transitory storage medium.

[0009] In addition, in the present specification, a decoding method includes the steps of: obtaining a luma block vector of a first luma component block of a current block; obtaining a chroma reference block, which is a chroma component block, based on the luma block vector; and predicting a first chroma component block of the current block based on the chroma reference block, wherein the first luma component block and the first chroma component block may correspond to each other.

[0010] In addition, the decoding method may further include: a step of obtaining a linear model for predicting the first chroma component block; a step of obtaining a non-linear model for predicting the first chroma component block; and a step of predicting the first chroma component block based on the linear model and the non-linear model.

[0011] In addition, the decoding method may further include the steps of: obtaining a first neighboring block of a luma reference block, which is a luma component block of the reference block; obtaining a second neighboring block of the chroma reference block; obtaining a CCCM (Convolutional cross-component intra prediction model) based on the first neighboring block and the second neighboring block; and predicting the first chroma component block based on the CCCM.

[0012] Additionally, in the present specification, the chroma reference block is a chroma component block of a reference block indicated by a scaled block vector, and the scaled block vector can be obtained by scaling the luma block vector based on the chroma format of the current block.

[0013] Additionally, in the present specification, the first chroma component block can be obtained based on a first prediction block obtained by applying the linear model to the chroma reference block, and a second prediction block obtained by applying the non-linear model to the chroma reference block.

[0014] Additionally, in the present specification, the second prediction block obtained by applying the non-linear model may be a block predicted by the DBV (Direct block vector) method.

[0015] Additionally, in the present specification, the second prediction block may be a block predicted based on any one of MTS (multiple transform selection), LFNST (Low Frequency Non-separable Transform), and NSPT (Non-Separable Primary Transform).

[0016] Additionally, in the present specification, the first luma component block may be applied with an IBC (Intra block copy) mode or an intra template matching mode.

[0017] This specification provides a method for efficiently processing a video signal.

[0018] The effects that can be obtained from this specification are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention pertains from the description below.

[0019] FIG. 1 is a schematic block diagram of a video signal encoding device according to one embodiment of the present invention.

[0020] FIG. 2 is a schematic block diagram of a video signal decoding device according to one embodiment of the present invention.

[0021] Figure 3 illustrates an embodiment in which a coding tree unit within a picture is divided into coding units.

[0022] Figure 4 illustrates one embodiment of a method for signaling the splitting of a quad tree and a multi-type tree.

[0023] Figures 5 and 6 illustrate the intra prediction method according to an embodiment of the present invention in more detail.

[0024] Figure 7 is a diagram showing the locations of surrounding blocks used to construct a motion candidate list in inter prediction.

[0025] FIG. 8 is a diagram showing the relationship between a luma sample and a chroma sample according to one embodiment of the present invention.

[0026] FIG. 9 is a diagram showing a reference sample required for Cross-component Linear Model (CCLM) prediction according to one embodiment of the present invention.

[0027] FIG. 10 is a diagram showing a mode in which CCLM is applied according to one embodiment of the present invention.

[0028] FIG. 11 is a diagram illustrating a CCLM mode using two linear models according to one embodiment of the present specification.

[0029] Fig. 12 is a drawing showing a division structure of a block according to one embodiment of the present invention.

[0030] FIG. 13 is a diagram illustrating a method for optimizing a linear model for CCLM according to one embodiment of the present invention.

[0031] FIG. 14 is a diagram illustrating a gradient linear model (GLM) according to one embodiment of the present invention.

[0032] Figure 15 is a diagram showing a filter for obtaining a slope value used in GLM.

[0033] FIG. 16 illustrates an example of a reference region and filter shape used to derive CCCM parameters according to one embodiment of the present invention.

[0034] Figures 17 and 18 illustrate luminance samples before downsampling used to derive chrominance samples in CCCM-ND mode according to one embodiment of the present invention.

[0035] FIG. 19 shows a downsampling filter and sample positions applied to a luminance block according to one embodiment of the present invention.

[0036] FIG. 20 is a diagram illustrating a direct block vector according to one embodiment of the present invention.

[0037] Figures 21 and 22 show additional locations for application of DBV according to one embodiment of the present invention.

[0038] FIG. 23 is a diagram showing a type of conversion kernel according to one embodiment of the present invention.

[0039] FIG. 24 is a diagram showing the 0th (lowest frequency component of the corresponding transform kernel) basis function of DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII transforms according to one embodiment of the present invention.

[0040] FIG. 25 and FIG. 26 are diagrams showing a set of transformation kernels according to one embodiment of the present invention.

[0041] FIG. 27 is a diagram illustrating a process for restoring a residual signal according to one embodiment of the present invention.

[0042] FIG. 28 is a diagram showing a region-of-interest (ROI) of a block to which a secondary transformation is applied according to one embodiment of the present invention.

[0043] FIG. 29 is a diagram showing a method of applying a second-order transform (LFNST) according to one embodiment of the present invention.

[0044] FIG. 30 is a diagram showing a mapping relationship between an intra prediction mode and a set of transformation kernels for secondary transformation according to one embodiment of the present invention.

[0045] FIG. 31 is a diagram showing the relationship between the input vector of the secondary transformation and the intra prediction mode according to one embodiment of the present invention.

[0046] Figure 32 shows the application block and kernel size of NSPT (Non-Separable Primary Transform) according to one embodiment of the present invention.

[0047] Fig. 33 illustrates an intra prediction mode derivation method for applying MTS / LFNST / NSPT according to one embodiment of the present invention.

[0048] Figure 34 illustrates syntax elements related to DBV according to one embodiment of the present invention.

[0049] Figure 35 illustrates the operation of BVG-CCCM (Block Vector Guided CCCM) according to one embodiment of the present invention.

[0050] Figure 36 illustrates syntax elements related to BVC-CCCM according to one embodiment of the present invention.

[0051] FIG. 37 illustrates a method for determining a reference pixel line based on a template according to one embodiment of the present invention.

[0052] Fig. 38 shows a block vector related to an IBC encoding method according to one embodiment of the present invention.

[0053] FIG. 39 illustrates a method for predicting a current block using RRIBC in a horizontal direction according to one embodiment of the present invention.

[0054] FIG. 40 illustrates a method for predicting a current block using RRIBC in the vertical direction according to one embodiment of the present invention.

[0055] Fig. 41 shows a block vector of a block encoded in Intra TMP mode according to one embodiment of the present invention.

[0056] Figure 42 illustrates a case where a current block is divided by GPM mode according to one embodiment of the present invention and the divided area is encoded in IBC mode.

[0057] Figure 43 illustrates how a current block is encoded in IBC-CIIP mode according to one embodiment of the present invention.

[0058] FIG. 44 illustrates a method for deriving a multi-transform set and a LFNST / NSPT set according to one embodiment of the present invention.

[0059] Figure 45 shows a mapping table according to one embodiment of the present invention.

[0060] Figure 46 illustrates a conversion type set table according to one embodiment of the present invention.

[0061] Figure 47 shows a conversion type combination table according to one embodiment of the present invention.

[0062] Figure 48 shows a threshold value table for an IDT conversion type according to one embodiment of the present invention.

[0063] Figure 49 shows block boundaries and samples around the boundaries in a deblocking filtering process according to one embodiment of the present invention.

[0064] FIG. 50 shows generating a prediction block by applying a filter model to IBC block prediction according to an embodiment of the present invention.

[0065] FIGS. 51 to 54 are diagrams illustrating a method for generating a prediction block according to one embodiment of the present invention.

[0066] Figure 55 shows the form of a template required for a CCCM model for applying a filter model to a current block according to an embodiment of the present invention.

[0067] Figure 56 shows a preset location for referencing a CCCM series model for filtering a current block according to an embodiment of the present invention.

[0068] FIG. 57 shows an operation of applying CCCM-ND to current luma sample prediction according to an embodiment of the present invention.

[0069] FIG. 58 is a flowchart of a method for predicting a chroma block based on a template according to one embodiment of the present invention.

[0070] The terms used in this specification have been selected from widely used and current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, customs, or the emergence of new technologies. Furthermore, in certain cases, the applicant may arbitrarily select terms, in which case their meanings will be described in the description of the relevant invention. Therefore, it should be noted that the terms used in this specification should be interpreted based on their substantive meaning and the overall content of this specification, rather than simply their names.

[0071] In this specification, 'A and / or B' may be interpreted to mean 'comprising at least one of A or B'.

[0072] In this specification, some terms may be interpreted as follows. Coding may be interpreted as encoding or decoding, depending on the case. In this specification, a device that encodes a video signal to generate a video signal bitstream is referred to as an encoding device or encoder, and a device that decodes a video signal bitstream to restore a video signal is referred to as a decoding device or decoder. In addition, in this specification, a video signal processing device is used as a term that includes both an encoder and a decoder. Information is a term that includes values, parameters, coefficients, elements, etc., and since the meaning may be interpreted differently depending on the case, the present invention is not limited thereto. 'Unit' is used to mean a basic unit of image processing or a specific location of a picture, and refers to an image area that includes at least one of a luminance component and a chroma component. In addition, 'block' refers to an image area including specific components among luminance components and chrominance components (i.e., Cb and Cr). However, depending on the embodiment, terms such as 'unit', 'block', 'partition', 'signal', and 'region' may be used interchangeably. In addition, in this specification, 'current block' means a block that is currently scheduled to be encoded, and 'reference block' means a block that has already been encoded or decoded and is used as a reference in the current block. In addition, in this specification, terms such as 'luma', 'luminance', and 'Y' may be used interchangeably. In addition, in this specification, terms such as 'chroma', 'chroma', 'color difference', and 'Cb or Cr' may be used interchangeably, and since chrominance components are divided into two, Cb and Cr, each chrominance component may be used separately. In addition, in this specification, a unit may be used as a concept including all of a coding unit, a prediction unit, and a transformation unit.A picture refers to a field or a frame, and depending on the embodiment, the terms may be used interchangeably. Specifically, if the captured image is an interlace image, one frame is divided into an odd (or odd, top) field and an even (or even, bottom) field, and each field is configured as one picture unit and can be encoded or decoded. If the captured image is a progressive image, one frame is configured as a picture and can be encoded or decoded. In addition, in this specification, the terms 'error signal', 'residual signal', 'residual signal', 'residual signal', and 'differential signal' may be used interchangeably. In addition, in this specification, the terms 'intra prediction mode', 'intra prediction directional mode', 'intra-screen prediction mode', and 'intra-screen prediction directional mode' may be used interchangeably. In addition, in this specification, the terms 'motion', 'movement', and the like may be used interchangeably. In addition, in this specification, 'left', 'upper left', 'upper left', 'upper right', 'right', 'lower right', 'lower left', and 'lower left' can be used interchangeably with 'left', 'upper left', 'top', 'upper right', 'right', 'lower right', 'bottom', and 'lower left'. In addition, element and member can be used interchangeably with each other. POC (Picture Order Count) indicates the temporal position information of a picture (or frame), can be the playback order displayed on the screen, and can have a unique POC for each picture.

[0073] FIG. 1 is a schematic block diagram of a video signal encoding device (100) according to one embodiment of the present invention. Referring to FIG. 1, the encoding device (100) of the present invention includes a transformation unit (110), a quantization unit (115), an inverse quantization unit (120), an inverse transformation unit (125), a filtering unit (130), a prediction unit (150), and an entropy coding unit (160).

[0074] The transform unit (110) obtains a transform coefficient value by transforming the residual signal, which is the difference between the input video signal and the prediction signal generated by the prediction unit (150). For example, a discrete cosine transform (DCT), a discrete sine transform (DST), or a wavelet transform may be used. The discrete cosine transform and the discrete sine transform divide the input picture signal into blocks and perform the transformation. The coding efficiency may vary depending on the distribution and characteristics of the values ​​within the transform domain during the transformation. The transform kernel used for the transformation on the residual block may be a transform kernel having separable characteristics of vertical transformation and horizontal transformation. In this case, the transformation on the residual block may be performed separately as vertical transformation and horizontal transformation. For example, the encoder may perform vertical transformation by applying the transform kernel in the vertical direction of the residual block. Additionally, the encoder can perform horizontal transformation by applying a transformation kernel in the horizontal direction of the residual block. In the present disclosure, the transformation kernel may be used as a term referring to a set of parameters used for transformation of the residual signal, such as a transformation matrix, a transformation array, a transformation function, or a transformation. For example, the transformation kernel may be any one of a plurality of available kernels. Additionally, transformation kernels based on different transformation types may be used for each of the vertical transformation and the horizontal transformation.

[0075] The transformation coefficients are distributed in a way that increases toward the upper left corner of the block, and decreases toward 0 toward the lower right corner. As the current block size increases, there is a high probability of a significant number of 0 coefficients in the lower right corner. To reduce the transformation complexity of large blocks, the remaining regions can be reset to 0, leaving only the upper left corner as an arbitrary region.

[0076] Additionally, error signals may exist only in some regions of a coding block. In this case, the conversion process may be performed only on some arbitrary regions. For example, in a block of size 2Nx2N, an error signal may exist only in the first 2NxN block, and the conversion process may be performed only on the first 2NxN block, but the conversion process may not be performed on the second 2NxN block and may not be encoded or decoded. Here, N can be any positive integer.

[0077] The encoder may perform an additional transform before the transform coefficients are quantized. The aforementioned transform method may be referred to as a primary transform, and the additional transform may be referred to as a secondary transform. The secondary transform may be optional for each residual block. In one embodiment, the encoder may improve coding efficiency by performing the secondary transform on areas where it is difficult to concentrate energy in the low-frequency region using only the primary transform. For example, the secondary transform may be additionally performed on blocks where residual values ​​appear large in directions other than the horizontal or vertical direction of the residual block. Unlike the primary transform, the secondary transform may not be performed separately into a vertical transform and a horizontal transform. Such a secondary transform may be referred to as a Low Frequency Non-Separable Transform (LFNST).

[0078] The quantization unit (115) quantizes the transformation coefficient value output from the transformation unit (110).

[0079] In order to increase coding efficiency, rather than coding the picture signal as it is, a method is used to predict a picture using an already coded area through a prediction unit (150), and to obtain a restored picture by adding the residual value between the original picture and the predicted picture to the predicted picture. In order to prevent mismatches from occurring in the encoder and decoder, when the encoder performs prediction, information that is also available to the decoder must be used. To this end, the encoder performs a process of restoring the encoded current block. The inverse quantization unit (120) inversely quantizes the transform coefficient value, and the inverse transform unit (125) restores the residual value using the inverse quantized transform coefficient value. Meanwhile, the filtering unit (130) performs a filtering operation to improve the quality of the restored picture and enhance the coding efficiency. For example, a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter may be included. The filtered picture is stored in the Decoded Picture Buffer (DPB, 156) to be output or used as a reference picture.

[0080] A deblocking filter is a filter that removes distortion within blocks generated at the boundaries between blocks in a reconstructed picture. The encoder can determine whether to apply a deblocking filter to a certain boundary based on the distribution of pixels in several columns or rows based on an arbitrary boundary (edge) within the block. When applying a deblocking filter to a block, the encoder can apply a long filter, a strong filter, or a weak filter depending on the deblocking filtering strength. Additionally, horizontal and vertical filtering can be processed in parallel. Sample adaptive offset (SAO) can be used to correct the offset from the original image on a pixel-by-pixel basis for the residual block to which the deblocking filter has been applied. To correct the offset for a specific picture, the encoder can divide the pixels contained in the image into a certain number of regions, determine the regions to perform offset correction, and apply the offset to those regions (Band Offset). Alternatively, the encoder can use a method (Edge Offset) that applies an offset by considering the edge information of each pixel. An adaptive loop filter (ALF) is a method that divides pixels included in an image into a predetermined group, determines a filter to be applied to each group, and performs filtering differently for each group. Information regarding whether to apply ALF can be signaled on a coding unit basis, and the shape and filter coefficients of the ALF filter to be applied can vary depending on each block. In addition, an ALF filter of the same shape (fixed shape) can be applied regardless of the characteristics of the target block to which it is applied.

[0081] The prediction unit (150) includes an intra prediction unit (152) and an inter prediction unit (154). The intra prediction unit (152) performs intra prediction within a current picture, and the inter prediction unit (154) performs inter prediction to predict the current picture using a reference picture stored in a decoded picture buffer (156). The intra prediction unit (152) performs intra prediction from reconstructed regions within the current picture and transfers intra encoding information to the entropy coding unit (160). The intra encoding information may include at least one of an intra prediction mode, an MPM (Most Probable Mode) flag, an MPM index, and information about a reference sample. The inter prediction unit (154) may be configured to include a motion estimation unit (154a) and a motion compensation unit (154b). The motion estimation unit (154a) refers to a specific area of ​​the restored reference picture to find the part most similar to the current area and obtains a motion vector value, which is the distance between the areas. The motion information (reference direction indication information (L0 prediction, L1 prediction, bidirectional prediction), reference picture index, motion vector information, etc.) for the reference area obtained by the motion estimation unit (154a) is transferred to the entropy coding unit (160) so that it can be included in the bitstream. Using the motion information transferred from the motion estimation unit (154a), the motion compensation unit (154b) performs inter-motion compensation to generate a prediction block for the current block. The inter-prediction unit (154) transfers inter-encoding information including motion information for the reference area to the entropy coding unit (160).

[0082] According to an additional embodiment, the prediction unit (150) may include an intra block copy (IBC) prediction unit (not shown). The IBC prediction unit performs IBC prediction on reconstructed samples in the current picture and transfers IBC encoding information to the entropy coding unit (160). The IBC prediction unit obtains a block vector value indicating a reference region used for prediction of the current region by referring to a specific region in the current picture. The IBC prediction unit may perform IBC prediction using the obtained block vector value. The IBC prediction unit transfers the IBC encoding information to the entropy coding unit (160). The IBC encoding information may include at least one of size information of the reference region, block vector information (index information for block vector prediction of the current block within a motion candidate list, and block vector difference information).

[0083] When the picture prediction as above is performed, the transformation unit (110) obtains a transformation coefficient value by transforming the residual value between the original picture and the predicted picture. At this time, the transformation can be performed in units of specific blocks within the picture, and the size of the specific block can be varied within a preset range. The quantization unit (115) quantizes the transformation coefficient value generated by the transformation unit (110) and transfers the quantized transformation coefficient to the entropy coding unit (160).

[0084] The quantized transform coefficients in the form of a two-dimensional array can be rearranged into a one-dimensional array for entropy coding. The method of scanning the quantized transform coefficients can be determined by which scanning method is used depending on the size of the transform block and the prediction mode within the screen. For example, diagonal, vertical, and horizontal scanning can be applied. This scanning information can be signaled on a block-by-block basis and can be derived according to predetermined rules.

[0085] The entropy coding unit (160) entropy-codes information representing quantized transform coefficients, intra-coding information, inter-coding information, etc. to generate a video signal bitstream. The entropy coding unit (160) may use a variable length coding (VLC) method and an arithmetic coding method. The variable length coding (VLC) method converts input symbols into continuous codewords, and the length of the codewords may be variable. For example, frequently occurring symbols are expressed as short codewords, and infrequently occurring symbols are expressed as long codewords. A context-based adaptive variable length coding (CAVLC) method may be used as a variable length coding method. Arithmetic coding converts continuous data symbols into a single prime number by using the probability distribution of each data symbol, and arithmetic coding can obtain the optimal prime number bits required to express each symbol. Context-based Adaptive Binary Arithmetic Code (CABAC) can be used as an arithmetic coding.

[0086] CABAC is a binary arithmetic coding method that uses multiple context models generated based on experimentally obtained probabilities. The context models can also be referred to as context models. First, if the symbols are not in binary form, the encoder binarizes each symbol using exp-Golomb, etc. The binarized 0 or 1 can be described as a bin. The CABAC initialization process is divided into context initialization and arithmetic coding initialization. Context initialization is the process of initializing the occurrence probability of each symbol, and is determined by the symbol type, quantization parameter (QP), and slice type (I, P, B). A context model with this initialization information can use probability-based values ​​obtained through experiments. The context model provides the occurrence probability of the Least Probable Symbol (LPS) or Most Probable Symbol (MPS) for the symbol to be currently encoded, as well as information (valMPS) on which bin value corresponds to the MPS between 0 and 1. One of several context models is selected through the context index (ctxIdx), and the context index can be derived from information about the current block to be encoded or information about the surrounding blocks. Initialization for binary arithmetic coding is performed based on the probability model selected from the context model. Binary arithmetic coding is performed by dividing the data into probability intervals based on the occurrence probabilities of 0 and 1, and then encoding is performed through a process in which the probability interval corresponding to the bin to be processed becomes the entire probability interval for the bin to be processed next. The location information within the probability interval in which the last bin has been processed is output. However, since the probability interval cannot be divided infinitely, if it is reduced to a certain size, a renormalization process is performed to expand the probability interval and output the corresponding location information. In addition, after each bin is processed, a probability update process can be performed in which the probability for the next bin to be processed is newly set based on the information of the processed bin.

[0087] The above generated bitstream is encapsulated into NAL (Network Abstraction Layer) units as basic units. NAL units are divided into VCL (Video Coding Layer) NAL units containing video data and non-VCL NAL units containing parameter information for decoding video data, and there are various types of VCL or non-VCL NAL units. A NAL unit consists of NAL header information and RBSP (Raw Byte Sequence Payload) data, and the NAL header information includes summary information about the RBSP. The RBSP of a VCL NAL unit includes an integer number of encoded coding tree units. In order for a video decoder to decode a bitstream, the bitstream must first be divided into NAL unit units, and then each divided NAL unit must be decoded. Meanwhile, information necessary for decoding a video signal bitstream can be transmitted by being included in a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), a Video Parameter Set (VPS), etc.

[0088] Meanwhile, the block diagram of FIG. 1 illustrates an encoding device (100) according to one embodiment of the present invention, and the blocks shown separately logically distinguish elements of the encoding device (100). Accordingly, the elements of the encoding device (100) described above may be mounted as one chip or as multiple chips depending on the design of the device. According to one embodiment, the operations of each element of the encoding device (100) described above may be performed by a processor (not shown).

[0089] Fig. 2 is a schematic block diagram of a video signal decoding device (200) according to one embodiment of the present invention. Referring to Fig. 2, the decoding device (200) of the present invention includes an entropy decoding unit (210), an inverse quantization unit (220), an inverse transformation unit (225), a filtering unit (230), and a prediction unit (250).

[0090] The entropy decoding unit (210) entropy decodes the video signal bitstream to extract transform coefficient information, intra-coding information, inter-coding information, etc. for each region. For example, the entropy decoding unit (210) can obtain a binarization code for transform coefficient information of a specific region from the video signal bitstream. In addition, the entropy decoding unit (210) inversely binarizes the binarization code to obtain a quantized transform coefficient. The inverse quantization unit (220) inversely quantizes the quantized transform coefficient, and the inverse transform unit (225) restores the residual value using the inverse quantized transform coefficient. The video signal processing device (200) restores the original pixel value by adding the residual value obtained by the inverse transform unit (225) and the prediction value obtained by the prediction unit (250).

[0091] Meanwhile, the filtering unit (230) performs filtering on the picture to improve the image quality. This may include a deblocking filter to reduce block distortion and / or an adaptive loop filter to remove distortion from the entire picture. The filtered picture is output or stored in the decoded picture buffer (DPB, 256) to be used as a reference picture for the next picture.

[0092] The prediction unit (250) includes an intra prediction unit (252) and an inter prediction unit (254). The prediction unit (250) generates a prediction picture by utilizing the encoding type decoded through the entropy decoding unit (210) described above, the transform coefficients for each region, intra / inter encoding information, etc. In order to restore the current block on which decoding is performed, the decoded region of the current picture or other pictures including the current block may be used. A picture (or tile / slice) that uses only the current picture for restoration, i.e., performs intra prediction or intra BC prediction, is called an intra picture or I picture (or tile / slice), and a picture (or tile / slice) that can perform all of intra prediction, inter prediction, and intra BC prediction is called an inter picture (or tile / slice). A picture (or tile / slice) that uses at most one motion vector and reference picture index to predict sample values ​​of each block among inter-pictures (or tiles / slices) is called a predictive picture or P-picture (or tile / slice), and a picture (or tile / slice) that uses at most two motion vectors and reference picture indices is called a bi-predictive picture or B-picture (or tile / slice). In other words, a P-picture (or tile / slice) uses at most one motion information set to predict each block, and a B-picture (or tile / slice) uses at most two motion information sets to predict each block. Here, a motion information set includes one or more motion vectors and one reference picture index.

[0093] The intra prediction unit (252) generates a prediction block using intra encoding information and reconstructed samples within the current picture. As described above, the intra encoding information may include at least one of an intra prediction mode, a Most Probable Mode (MPM) flag, and an MPM index. The intra prediction unit (252) predicts sample values ​​of the current block using reconstructed samples located on the left and / or above the current block as reference samples. In the present disclosure, the reconstructed samples, the reference samples, and the samples of the current block may represent pixels. Additionally, the sample values ​​may represent pixel values.

[0094] According to one embodiment, the reference samples may be samples included in a neighboring block of the current block. For example, the reference samples may be samples adjacent to a left boundary of the current block and / or samples adjacent to an upper boundary. In addition, the reference samples may be samples located on a line within a preset distance from a left boundary of the current block and / or samples located on a line within a preset distance from an upper boundary of the current block among samples of neighboring blocks of the current block. In this case, the neighboring blocks of the current block may include at least one of a left (L) block, an upper (A) block, a lower left (BL) block, an above right (AR) block, or an above left (AL) block adjacent to the current block.

[0095] The inter prediction unit (254) generates a prediction block using the reference picture and inter encoding information stored in the decoded picture buffer (256). The inter encoding information may include a set of motion information (reference picture index, motion vector information, etc.) of the current block with respect to the reference block. Inter prediction may include L0 prediction, L1 prediction, and bi-prediction. L0 prediction is prediction using one reference picture included in the L0 picture list, and L1 prediction means prediction using one reference picture included in the L1 picture list. For this, one set of motion information (e.g., motion vector and reference picture index) may be required. In the bi-prediction method, up to two reference areas can be used, and these two reference areas may exist in the same reference picture or may exist in different pictures, respectively. That is, in the bi-prediction method, up to two sets of motion information (e.g., motion vectors and reference picture indices) can be used, and the two motion vectors may correspond to the same reference picture index or may correspond to different reference picture indices. In this case, the reference pictures are pictures that are located temporally before or after the current picture, and may be completed pictures that have already been restored. According to one embodiment, the two reference areas used in the bi-prediction method may be areas selected from each of the L0 picture list and the L1 picture list.

[0096] The inter prediction unit (254) can obtain a reference block of the current block using a motion vector and a reference picture index. The reference block exists in a reference picture corresponding to the reference picture index. In addition, a sample value of a block specified by the motion vector or an interpolated value thereof can be used as a predictor of the current block. For motion prediction with sub-pel unit pixel accuracy, for example, an 8-tap interpolation filter can be used for a luminance signal and a 4-tap interpolation filter can be used for a chrominance signal. However, the interpolation filter for sub-pel unit motion prediction is not limited thereto. In this way, the inter prediction unit (254) performs motion compensation to predict the texture of the current unit from a previously restored picture. At this time, the inter prediction unit can use a motion information set.

[0097] According to an additional embodiment, the prediction unit (250) may include an IBC prediction unit (not shown). The IBC prediction unit may reconstruct the current region by referring to a specific region including reconstructed samples within the current picture. The IBC prediction unit may perform IBC prediction using IBC encoding information obtained from the entropy decoding unit (210). The IBC encoding information may include block vector information.

[0098] A restored video picture is generated by adding the predicted value output from the intra prediction unit (252) or inter prediction unit (254) and the residual value output from the inverse transformation unit (225). That is, the video signal decoding device (200) restores the current block using the predicted block generated from the prediction unit (250) and the residual obtained from the inverse transformation unit (225).

[0099] Meanwhile, the block diagram of FIG. 2 illustrates a decoding device (200) according to one embodiment of the present invention, and the blocks shown separately logically distinguish the elements of the decoding device (200). Accordingly, the elements of the aforementioned decoding device (200) may be mounted as one chip or as multiple chips depending on the design of the device. According to one embodiment, the operations of each element of the aforementioned decoding device (200) may be performed by a processor (not shown).

[0100] Meanwhile, the technology proposed in this specification is applicable to both the methods and devices of the encoder and decoder, and the parts described as signaling and parsing may be described for convenience of explanation. In general, signaling can be described as encoding each syntax from the encoder's perspective, and parsing can be described as interpreting each syntax from the decoder's perspective. That is, each syntax can be included in the bitstream from the encoder and signaled, and the decoder can parse the syntax and use it in the restoration process. At this time, the sequence of bits for each syntax listed in the prescribed hierarchical structure can be referred to as a bitstream.

[0101] A picture can be encoded by dividing it into sub-pictures, slices, tiles, etc. A sub-picture can include one or more slices or tiles. When a picture is encoded by dividing it into multiple slices or tiles, all slices or tiles within the picture must be decoded before it can be displayed on the screen. On the other hand, when a picture is encoded into multiple sub-pictures, only any sub-picture can be decoded and displayed on the screen. A slice can include multiple tiles or sub-pictures, or a tile can include multiple sub-pictures or slices. Sub-pictures, slices, and tiles can be encoded or decoded independently, which is effective for parallel processing and improving processing speed. However, there is a disadvantage in that the amount of bits increases because the encoded information of adjacent sub-pictures, slices, and tiles cannot be used. Sub-pictures, slices, and tiles can be encoded by dividing them into multiple coding tree units (CTUs).

[0102] FIG. 3 illustrates an embodiment in which a Coding Tree Unit (CTU) within a picture is divided into Coding Units (CUs). In the process of coding a video signal, a picture may be divided into a sequence of Coding Tree Units (CTUs). A Coding Tree Unit may be composed of a luminance (luma) Coding Tree Block (CTB), two chroma (chroma) Coding Tree Blocks, and their encoded syntax information. One Coding Tree Unit may be composed of one Coding Unit, or one Coding Tree Unit may be split into multiple Coding Units. One Coding Unit may be composed of a luminance Coding Block (CB), two chroma Coding Blocks, and their encoded syntax information. One Coding Block may be split into multiple Sub-Coding Blocks. One Coding Unit may be composed of one Transform Unit (TU), or one Coding Unit may be split into multiple Transform Units. A single transform unit may consist of a luminance transform block (TB), two chrominance transform blocks, and their encoded syntax information. A coding tree unit may be divided into multiple coding units. A coding tree unit may not be divided and may also be a leaf node. In this case, the coding tree unit itself may be a coding unit.

[0103] A coding unit refers to a basic unit for processing a picture in the video signal processing described above, such as intra / inter prediction, transformation, quantization, and / or entropy coding. The size and shape of a coding unit within a picture may not be constant. A coding unit may have a square or rectangular shape. A rectangular coding unit (or rectangular block) includes a vertical coding unit (or vertical block) and a horizontal coding unit (or horizontal block). In the present specification, a vertical block is a block whose height is greater than its width, and a horizontal block is a block whose width is greater than its height. In addition, a non-square block in the present specification may refer to a rectangular block, but the present invention is not limited thereto.

[0104] Referring to Fig. 3, the coding tree unit is first partitioned into a Quad Tree (QT) structure. That is, in the Quad Tree structure, one node with a size of 2NX2N can be partitioned into four nodes with a size of NXN. In this specification, the Quad Tree may also be referred to as a quaternary tree. The Quad Tree partitioning can be performed recursively, and not all nodes need to be partitioned to the same depth.

[0105] Meanwhile, the leaf node of the aforementioned quad tree can be further split into a multi-type tree (MTT) structure. According to an embodiment of the present invention, in the multi-type tree structure, one node can be split into a binary or ternary tree structure of horizontal or vertical split. That is, the multi-type tree structure has four split structures: vertical binary split, horizontal binary split, vertical ternary split, and horizontal ternary split. According to an embodiment of the present invention, in each of the above tree structures, the width and height of the node can both have a power of 2 value. For example, in the binary tree (BT) structure, a node of size 2NX2N can be split into two NX2N nodes by vertical binary split, and can be split into two 2NXN nodes by horizontal binary split. Also, in a Ternary Tree (TT) structure, a node of size 2NX2N can be split into nodes of size (N / 2)X2N, NX2N, and (N / 2)X2N by vertical ternary splitting, and into nodes of size 2NX(N / 2), 2NXN, and 2NX(N / 2) by horizontal ternary splitting. This multi-type tree splitting can be performed recursively.

[0106] A leaf node of a multi-type tree can be a coding unit. If the coding unit is not larger than the maximum transformation length, the coding unit can be used as a unit of prediction and / or transformation without further splitting. In one embodiment, if the width or height of the current coding unit is larger than the maximum transformation length, the current coding unit can be split into multiple transformation units without explicit signaling regarding the splitting. Meanwhile, in the quad tree and multi-type tree described above, at least one of the following parameters can be predefined or transmitted through an RBSP of a higher-level set, such as a PPS, an SPS, or a VPS. 1) CTU size: The size of the root node of the quad tree, 2) MinQtSize: The minimum allowed QT leaf node size, 3) MaxBtSize: The maximum allowed BT root node size, 4) MaxTT size (MaxTtSize): The maximum allowed TT root node size, 5) MaxMttDepth: The maximum allowed depth of an MTT split from a leaf node of a QT, 6) MinBT size (MinBtSize): The minimum allowed BT leaf node size, 7) MinTT size (MinTtSize): The minimum allowed TT leaf node size.

[0107] Fig. 4 illustrates one embodiment of a method for signaling splitting of a quad tree and a multi-type tree. Pre-configured flags may be used to signal splitting of the quad tree and the multi-type tree described above. Referring to Fig. 4, at least one of a flag 'split_cu_flag' indicating whether a node is split, a flag 'split_qt_flag' indicating whether a quad tree node is split, a flag 'mtt_split_cu_vertical_flag' indicating a splitting direction of a multi-type tree node, or a flag 'mtt_split_cu_binary_flag' indicating a splitting shape of a multi-type tree node may be used.

[0108] According to an embodiment of the present invention, a flag 'split_cu_flag' indicating whether a current node is split may be signaled first. If the value of 'split_cu_flag' is 0, it indicates that the current node is not split, and the current node becomes a coding unit. If the current node is a coding tree unit, the coding tree unit includes one coding unit that is not split. If the current node is a quad tree node 'QT node', the current node is a leaf node 'QT leaf node' of the quad tree and becomes a coding unit. If the current node is a multi-type tree node 'MTT node', the current node is a leaf node 'MTT leaf node' of the multi-type tree and becomes a coding unit.

[0109] When the value of 'split_cu_flag' is 1, the current node can be split into nodes of a quad tree or a multi-type tree depending on the value of 'split_qt_flag'. The coding tree unit is the root node of the quad tree and can be first split into a quad tree structure. In the quad tree structure, 'split_qt_flag' is signaled for each node 'QT node'. When the value of 'split_qt_flag' is 1, the node is split into four square nodes, and when the value of 'split_qt_flag' is 0, the node becomes a leaf node 'QT leaf node' of the quad tree, and the node is split into multi-type nodes. According to an embodiment of the present invention, quad tree splitting can be limited depending on the type of the current node. Quad tree splitting may be allowed if the current node is a coding tree unit (root node of a quad tree) or a quad tree node, and quad tree splitting may not be allowed if the current node is a multi-type tree node. Each quad tree leaf node 'QT leaf node' may be further split into a multi-type tree structure. As described above, if 'split_qt_flag' is 0, the current node may be split into multi-type nodes. To indicate the splitting direction and splitting shape, 'mtt_split_cu_vertical_flag' and 'mtt_split_cu_binary_flag' may be signaled. If the value of 'mtt_split_cu_vertical_flag' is 1, a vertical split of the node 'MTT node' is indicated, and if the value of 'mtt_split_cu_vertical_flag' is 0, a horizontal split of the node 'MTT node' is indicated.Additionally, if the value of 'mtt_split_cu_binary_flag' is 1, the node 'MTT node' is split into two rectangular nodes, and if the value of 'mtt_split_cu_binary_flag' is 0, the node 'MTT node' is split into three rectangular nodes.

[0110] The tree partitioning structure allows luminance blocks and chrominance blocks to be partitioned in the same manner. That is, the chrominance blocks can be partitioned by referring to the partitioning form of the luminance blocks. If the current chrominance block is smaller than a predetermined size, the chrominance block may not be partitioned even if the luminance block is partitioned.

[0111] The tree partitioning structure may have different forms for luminance blocks and chrominance blocks. In this case, partitioning information for the luminance block and partitioning information for the chrominance block may be signaled separately. Furthermore, not only the partitioning information but also the encoding information for the luminance block and chrominance block may differ. For example, at least one of the intra-coding modes of the luminance block and the chrominance block, and the encoding information for motion information, may differ.

[0112] A node to be divided into the smallest unit can be processed as a single coding block. If the current block is a coding block, the coding block can be divided into multiple sub-blocks (sub-coding blocks), and the prediction information of each sub-block can be the same or different. For example, if the coding unit is an intra mode, the intra prediction modes of each sub-block can be the same or different. Furthermore, if the coding unit is an inter mode, the motion information of each sub-block can be the same or different. Furthermore, each sub-block can be encoded or decoded independently. Each sub-block can be distinguished through a sub-block index (sbIdx). Furthermore, when a coding unit is divided into sub-blocks, it can be divided horizontally, vertically, or diagonally. In intra mode, the mode that divides the current coding unit into two or four sub-blocks horizontally or vertically is called ISP (Intra Sub-Partitions). In inter mode, the mode that divides the current coding block diagonally is called GPM (Geometric partitioning mode). In GPM mode, the position and direction of the diagonal line are derived using a predefined angle table, and the index information of the angle table is signaled.

[0113] Picture prediction (motion compensation) for coding is performed on coding units that are no longer divisible (i.e., leaf nodes of a coding tree unit). The basic unit performing this prediction is referred to below as a prediction unit or prediction block.

[0114] Hereinafter, the term "unit" used in this specification may be used as a replacement for the prediction unit, which is the basic unit for performing prediction. However, the present invention is not limited thereto, and can be understood more broadly as a concept that includes the coding unit.

[0115] Figures 5 and 6 illustrate an intra prediction method according to an embodiment of the present invention in more detail. As described above, the intra prediction unit predicts sample values ​​of the current block using restored samples located to the left and / or above the current block as reference samples.

[0116] First, FIG. 5 illustrates an embodiment of reference samples used for prediction of a current block in an intra prediction mode. According to an embodiment, the reference samples may be samples adjacent to a left boundary of the current block and / or samples adjacent to an upper boundary. As illustrated in FIG. 5, when the size of the current block is WXH and samples of a single reference line adjacent to the current block are used for intra prediction, reference samples may be set using at most 2W+2H+1 surrounding samples located on the left and / or upper sides of the current block.

[0117] Meanwhile, pixels of multiple reference lines may be used for intra prediction of the current block. The multiple reference lines may be composed of n lines located within a preset range from the current block. According to one embodiment, when pixels of multiple reference lines are used for intra prediction, separate index information indicating the lines to be set as reference pixels may be signaled, and this may be referred to as a reference line index.

[0118] In addition, if at least some of the samples to be used as reference samples have not yet been restored, the intra prediction unit may perform a reference sample padding process to obtain a reference sample. In addition, the intra prediction unit may perform a reference sample filtering process to reduce an error in intra prediction. That is, filtering may be performed on the surrounding samples and / or the reference samples obtained by the reference sample padding process to obtain filtered reference samples. The intra prediction unit predicts samples of the current block using the reference samples obtained in this manner. The intra prediction unit predicts samples of the current block using unfiltered reference samples or filtered reference samples. In the present disclosure, the surrounding samples may include samples on at least one reference line. For example, the surrounding samples may include adjacent samples on a line adjacent to a boundary of the current block.

[0119] Next, FIG. 6 illustrates an embodiment of prediction modes used for intra prediction. For intra prediction, intra prediction mode information indicating an intra prediction direction may be signaled. The intra prediction mode information indicates any one of a plurality of intra prediction modes constituting an intra prediction mode set. If the current block is an intra prediction block, the decoder receives intra prediction mode information of the current block from the bitstream. The intra prediction unit of the decoder performs intra prediction on the current block based on the extracted intra prediction mode information.

[0120] According to an embodiment of the present invention, an intra prediction mode set may include all intra prediction modes used for intra prediction (e.g., a total of 67 intra prediction modes). More specifically, the intra prediction mode set may include a planar mode, a DC mode, and a plurality of (e.g., 65) angular modes (i.e., directional modes). Each intra prediction mode may be indicated by a preset index (i.e., an intra prediction mode index). For example, as illustrated in FIG. 6, an intra prediction mode index 0 indicates a planar mode, and an intra prediction mode index 1 indicates a DC mode. In addition, intra prediction mode indices 2 to 66 may each indicate different angular modes. The angular modes each indicate different angles within a preset angular range. For example, an angular mode may indicate an angle within an angular range from 45 degrees to -135 degrees clockwise (i.e., a first angular range). The angular mode may be defined based on the 12 o'clock direction. At this time, intra prediction mode index 2 indicates horizontal diagonal (HDIA) mode, intra prediction mode index 18 indicates horizontal (HOR) mode, intra prediction mode index 34 indicates diagonal (DIA) mode, intra prediction mode index 50 indicates vertical (VER) mode, and intra prediction mode index 66 indicates vertical diagonal (VDIA) mode.

[0121] Meanwhile, the preset angle range may be set differently depending on the shape of the current block. For example, if the current block is a rectangular block, a wide-angle mode indicating an angle exceeding 45 degrees or less than -135 degrees in a clockwise direction may be additionally used. If the current block is a horizontal block, the angle mode may indicate an angle within an angle range (i.e., a second angle range) between (45+offset1) degrees and (-135+offset1) degrees in a clockwise direction. At this time, angle modes 67 to 76 that are outside the first angle range may be additionally used. In addition, if the current block is a vertical block, the angle mode may indicate an angle within an angle range (i.e., a third angle range) between (45-offset2) degrees and (-135-offset2) degrees in a clockwise direction. At this time, angle modes -10 to -1 that are outside the first angle range may be additionally used. According to an embodiment of the present invention, the values ​​of offset1 and offset2 may be determined differently depending on the ratio between the width and height of the rectangular block. Also, offset1 and offset2 can be positive.

[0122] According to an additional embodiment of the present invention, the plurality of angular modes constituting the intra prediction mode set may include a basic angular mode and an extended angular mode. In this case, the extended angular mode may be determined based on the basic angular mode.

[0123] According to one embodiment, the basic angle mode may be a mode corresponding to an angle used in intra prediction of the existing HEVC (High Efficiency Video Coding) standard, and the extended angle mode may be a mode corresponding to an angle newly added in intra prediction of the next-generation video codec standard. More specifically, the basic angle mode may be an angle mode corresponding to any one of the intra prediction modes {2, 4, 6, … , 66}, and the extended angle mode may be an angle mode corresponding to any one of the intra prediction modes {3, 5, 7, … , 65}. That is, the extended angle mode may be an angle mode between the basic angle modes within the first angle range. Therefore, the angle indicated by the extended angle mode may be determined based on the angle indicated by the basic angle mode.

[0124] According to another embodiment, the basic angle mode may be a mode corresponding to an angle within a preset first angle range, and the extended angle mode may be a wide-angle mode outside the first angle range. That is, the basic angle mode may be an angle mode corresponding to any one of the intra prediction modes {2, 3, 4, … , 66}, and the extended angle mode may be an angle mode corresponding to any one of the intra prediction modes {-14, –13, –12, … , –1} and {67, 68, … , 80}. The angle indicated by the extended angle mode may be determined as an opposite angle to the angle indicated by the corresponding basic angle mode. Accordingly, the angle indicated by the extended angle mode may be determined based on the angle indicated by the basic angle mode. Meanwhile, the number of extended angle modes is not limited thereto, and additional extended angles may be defined according to the size and / or shape of the current block. Meanwhile, the total number of intra prediction modes included in the intra prediction mode set may vary depending on the configuration of the basic angle mode and the extended angle mode described above.

[0125] In the above embodiment, the spacing between the extended angular modes may be set based on the spacing between the corresponding basic angular modes. For example, the spacing between the extended angular modes {3, 5, 7, … , 65} may be determined based on the spacing between the corresponding basic angular modes {2, 4, 6, … , 66}. In addition, the spacing between the extended angular modes {-14, -13, … , -1} may be determined based on the spacing between the corresponding opposite basic angular modes {53, 53, … , 66}, and the spacing between the extended angular modes {67, 68, … , 80} may be determined based on the spacing between the corresponding opposite basic angular modes {2, 3, 4, … , 15}. The angular spacing between the extended angular modes may be set to be equal to the angular spacing between the corresponding basic angular modes. In addition, the number of the extended angular modes in the intra prediction mode set may be set to be less than or equal to the number of the basic angular modes.

[0126] According to an embodiment of the present invention, an extended angular mode may be signaled based on a base angular mode. For example, a wide-angle mode (i.e., an extended angular mode) may replace at least one angular mode (i.e., a base angular mode) within a first angular range. The replaced base angular mode may be an angular mode corresponding to an opposite side of the wide-angle mode. That is, the replaced base angular mode is an angular mode corresponding to an angle in an opposite direction to an angle indicated by the wide-angle mode or an angle that is different from the angle in the opposite direction by a preset offset index. According to an embodiment of the present invention, the preset offset index is 1. An intra prediction mode index corresponding to the replaced base angular mode may be remapped to the wide-angle mode to signal the corresponding wide-angle mode. For example, the wide-angle modes {-14, -13, … , -1} may be signaled by intra prediction mode indices {52, 53, … , 66}, and the wide-angle modes {67, 68, … , 69} may be signaled by intra prediction mode indices {52, 53, … , 66}, respectively. , 80} can be signaled by intra prediction mode indices {2, 3, … , 15}, respectively. By having the intra prediction mode index for the basic angular mode signal the extended angular mode in this way, even if the configurations of the angular modes used for intra prediction of each block are different, the same set of intra prediction mode indices can be used to signal the intra prediction mode. Therefore, the signaling overhead due to changes in the intra prediction mode configuration can be minimized.

[0127] Meanwhile, whether to use the extended angle mode may be determined based on at least one of the shape and size of the current block. In one embodiment, if the size of the current block is larger than a preset size, the extended angle mode may be used for intra prediction of the current block, and otherwise, only the default angle mode may be used for intra prediction of the current block. In another embodiment, if the current block is a non-square block, the extended angle mode may be used for intra prediction of the current block, and if the current block is a square block, only the default angle mode may be used for intra prediction of the current block.

[0128] The intra prediction unit determines reference samples and / or interpolated reference samples to be used for intra prediction of the current block based on intra prediction mode information of the current block. If the intra prediction mode index indicates a specific angular mode, the reference sample or interpolated reference sample corresponding to the specific angle from the current sample of the current block is used for prediction of the current pixel. Therefore, different sets of reference samples and / or interpolated reference samples can be used for intra prediction depending on the intra prediction mode. After intra prediction of the current block is performed using the reference samples and intra prediction mode information, the decoder restores the sample values ​​of the current block by adding the residual signal of the current block obtained from the inverse transform unit to the intra prediction value of the current block.

[0129] Motion information used for inter prediction may include reference direction indication information (inter_pred_idc), reference picture indexes (ref_idx_l0, ref_idx_l1), and motion vectors (mvL0, mvL1). Reference picture list utilization information (predFlagL0, predFlagL1) may be set according to the reference direction indication information. As an example, in case of unidirectional prediction using an L0 reference picture, predFlagL0=1, predFlagL1=0 may be set. In case of unidirectional prediction using an L1 reference picture, predFlagL0=0, predFlagL1=1 may be set. In case of bidirectional prediction using both L0 and L1 reference pictures, predFlagL0=1, predFlagL1=1 may be set.

[0130] If the current block is a coding unit, the coding unit can be divided into multiple sub-blocks, and the prediction information of each sub-block can be the same or different. For example, if the coding unit is an intra mode, the intra prediction modes of each sub-block can be the same or different. In addition, if the coding unit is an inter mode, the motion information of each sub-block can be the same or different. In addition, each sub-block can be encoded or decoded independently. Each sub-block can be distinguished through a sub-block index (sbIdx).

[0131] The motion vector of the current block is likely to be similar to that of the surrounding blocks. Therefore, the motion vectors of the surrounding blocks can be used as motion vector predictors (mvp), and the motion vector of the current block can be derived using the motion vectors of the surrounding blocks. Furthermore, to improve the accuracy of the motion vector, the difference in motion vectors (mvd) between the optimal motion vector of the current block, found from the original image by the encoder, and the motion predictor can be signaled.

[0132] Motion vectors can have various resolutions, and the resolution of motion vectors can vary on a block-by-block basis. Motion vector resolution can be expressed in integer units, half-pixel units, quarter-pixel units, sixteenth-pixel units, and integer-4 pixel units. Since images such as screen content are in simple graphical forms such as characters, interpolation filters do not need to be applied, integer units and integer-4 pixel units can be selectively applied on a block-by-block basis. Blocks encoded in affine mode, which can express rotation and scale, have significant shape changes, so integer units, quarter-pixel units, and sixteenth-pixel units can be selectively applied on a block-by-block basis. Information on whether to selectively apply motion vector resolution on a block-by-block basis is signaled with amvr_flag. If applicable, which motion vector resolution to apply to the current block is signaled with amvr_precision_idx.

[0133] For blocks to which bidirectional prediction is applied, the weights between the two prediction blocks can be applied equally or differently when applying weighted average, and information about the weights is signaled through bcw_idx.

[0134] To improve the accuracy of the motion prediction value, Merge or advanced motion vector prediction (AMVP) methods can be selectively used on a block-by-block basis. The Merge method configures the motion information of the current block to be identical to the motion information of the adjacent blocks to the current block, and has the advantage of increasing the encoding efficiency of the motion information by spatially propagating the motion information without change in the homogeneous motion region. On the other hand, the AMVP method predicts motion information in the L0 and L1 prediction directions respectively to express accurate motion information and signals the most optimal motion information. After the decoder derives the motion information for the current block through the AMVP or Merge method, it uses the reference block located in the motion information derived from the reference picture as the prediction block for the current block.

[0135] A method for deriving motion information in Merge or AMVP may be to construct a motion candidate list using motion prediction values ​​derived from neighboring blocks of the current block, and then signal the index information for the optimal motion candidate. In the case of AMVP, since motion candidate lists are derived for each of L0 and L1, the optimal motion candidate indices (mvp_l0_flag, mvp_l1_flag) for each of L0 and L1 are signaled. In the case of Merge, since one motion candidate list is derived, one merge index (merge_idx) is signaled. The motion candidate lists derived from one coding unit may vary, and a motion candidate index or merge index may be signaled for each motion candidate list. In this case, a mode in which there is no information about the remaining blocks in a block encoded in Merge mode can be referred to as MergeSkip mode.

[0136] The motion candidates and motion information candidates in this specification may have the same meaning. Furthermore, the motion candidate list and motion information candidate list in this specification may have the same meaning.

[0137] SMVD (Symmetric MVD) is a method for reducing the bit volume of transmitted motion information by ensuring that the MVD (Motion Vector Difference) values ​​in the L0 and L1 directions are symmetrical in the case of bidirectional prediction. The MVD information in the L1 direction, which is symmetrical to the L0 direction, is not transmitted, and reference picture information in the L0 and L1 directions is also not transmitted and can be derived during the decoding process.

[0138] OBMC (Overlapped Block Motion Compensation) is a method that generates prediction blocks for the current block using motion information from surrounding blocks when the motion information between blocks differs. It then weights and averages these prediction blocks to generate a final prediction block for the current block. This method effectively reduces blocking artifacts that occur at block boundaries in motion-compensated images.

[0139] Typically, merge motion candidates have low motion accuracy. To improve the accuracy of these merge motion candidates, the MMVD (Merge mode with MVD) method can be used. The MMVD method is a method of compensating motion information using one candidate selected from several motion difference value candidates. Information about the compensation value of the motion information obtained through the MMVD method (e.g., an index indicating one candidate selected from among the motion difference value candidates) can be included in the bitstream and transmitted to the decoder. Compared to the conventional method of including the motion information difference value in the bitstream, the inclusion of information about the compensation value of the motion information in the bitstream can save bits.

[0140] The TM (Template Matching) method constructs a template using the surrounding pixels of the current block, finds the matching area with the highest similarity to the template, and then compensates for motion information. TM (Template Matching) is a method that performs motion prediction in the decoder without including motion information in the bitstream to reduce the size of the encoded bitstream. Since the decoder does not have the original image, it can roughly derive motion information for the current block using already reconstructed surrounding blocks.

[0141] The DMVR (Decoder-side Motion Vector Refinement) method is a method of compensating motion information through the correlation of already restored reference images to find slightly more accurate motion information. It is a method of using the bidirectional motion information of the current block to use the best matching point between reference blocks within an arbitrary set area of ​​two reference pictures as a new bidirectional motion. When this DMVR is performed, the encoder performs DMVR on a block basis to compensate for the motion information, and then divides the block into sub-blocks and performs DMVR on each sub-block basis to compensate for the motion information of the sub-block again. This can be called MP-DMVR (Multi-pass DMVR).

[0142] The LIC (Local Illumination Compensation) method is a method of compensating for luminance changes between blocks. It is a method of deriving a linear model using neighboring pixels adjacent to the current block, and then compensating for the luminance information of the current block through the linear model.

[0143] Existing video encoding methods perform motion compensation that only considers parallel translation in all directions, which reduces encoding efficiency when encoding videos containing motions commonly encountered in the real world, such as zooming in, zooming out, and rotation. To express such motions, an affine model-based motion prediction technique utilizing a four-parameter (rotation) or six-parameter (zoom in, zoom out, rotation) model can be applied.

[0144] Bi-Directional Optical Flow (BDOF) is used to compensate for predicted blocks by estimating pixel changes based on optical flow from a reference block of a block composed of bidirectional motion. The motion information derived from BDOF in VVC can be used to compensate for the motion of the current block.

[0145] PROF (Prediction Refinement with Optical Flow) is a technique for improving the accuracy of sub-block-level affine motion prediction to be similar to that of pixel-level motion prediction. Similar to BDOF, PROF calculates a correction value on a pixel-by-pixel basis for affine motion-compensated pixel values ​​on a sub-block-by-subblock basis based on optical flow to obtain a final prediction signal.

[0146] The CIIP (Combined Inter- / Intra-picture Prediction) method is a method of generating a final prediction block by weighting and averaging prediction blocks generated by the intra-picture prediction method and prediction blocks generated by the inter-picture prediction method when generating a prediction block for the current block.

[0147] The Intra Block Copy (IBC) method finds the most similar part to the current block in a previously restored area within the current picture and uses that reference block as a prediction block for the current block. At this time, information related to the block vector, which represents the distance between the current block and the reference block, can be included in the bitstream. The decoder can parse the block vector information contained in the BeastStream to calculate or set the block vector for the current block.

[0148] The BCW (Bi-prediction with CU-level Weights) method is a method that performs a weighted average on two motion-compensated prediction blocks by adaptively applying weights on a block-by-block basis, rather than generating a prediction block by averaging two motion-compensated prediction blocks from different reference pictures.

[0149] The Intra TMP (Template Matching Prediction) method is a method in which a video signal processing device constructs a reference template using pixel values ​​of neighboring blocks adjacent to the current block, finds the part most similar to the constructed reference template in an already restored area within the current picture, and then uses the reference block (the part found in the already restored area) as a prediction block for the current block.

[0150] The MHP (Multi-hypothesis prediction) method is a method of performing weight prediction using various prediction signals by transmitting additional motion information to unidirectional and bidirectional motion information during inter-screen prediction.

[0151] CCLM (Cross-component linear model) is a method of predicting chrominance signals by constructing a linear model using the high correlation between a luminance signal and the chrominance signals located at the same location as the luminance signal. A template is constructed using blocks adjacent to the current block that have been reconstructed, and the parameters for the linear model are derived from the template. Next, the reconstructed current luminance block is selectively downsampled to match the size of the chrominance block depending on the image format. Finally, the chrominance block of the current block is predicted using the downsampled luminance block and the linear model. At this time, a method using two or more linear models is called MMLM (Multi-model Linear mode). In addition, a prediction method that utilizes the correlation between different signals, such as CCLM and MMLM, can be called CCP (Cross-Component Prediction).

[0152] The CCP merge method is a method of predicting the chrominance block of the current block using the CCP model (models such as CCLM, MMLM, and CCCM) used in the surrounding blocks.

[0153] In independent scalar quantization, the input coefficient t k Restored coefficients t' for k is the associated quantization index q k depends only on t'. That is, the quantization index for any restored coefficient has a different value from the quantization indices for other restored coefficients. In this case, t' k is t k may be a value that includes quantization error, and may be different or the same depending on the quantization parameter. Here, t' kcan be named restored transform coefficients or inverse quantized transform coefficients, and the quantization indices can also be named quantized transform coefficients.

[0154] In Uniform Reconstruction Quantizers (URQ), the reconstructed coefficients are spaced at equal intervals. The distance between two adjacent reconstructed values ​​is referred to as the quantization step size. Reconstructed values ​​can include zeros, and the entire set of available reconstructed values ​​can be uniquely defined by the quantization step size. The quantization step size can vary depending on the quantization parameter.

[0155] In conventional methods, quantization reduces the set of acceptable reconstructed transform coefficients, and the number of elements in this set can be finite. This limits the ability to minimize the average error between the original and reconstructed images. Vector quantization can be used as a method to minimize this average error.

[0156] A simple form of vector quantization used in video encoding is sign data hiding. This is a method in which the encoder does not encode the sign of a non-zero coefficient, and the decoder determines the sign of the coefficient based on whether the sum of the absolute values ​​of all coefficients is even or odd. To achieve this, the encoder may increase or decrease the value of at least one coefficient, and at least one coefficient may be selected and adjusted to be optimal in terms of rate-distortion cost. In one implementation, a coefficient having a value close to the boundary of the quantization interval may be selected.

[0157] Another vector quantization method is trellis-coded quantization, which is used in video coding as an optimal path search technique to obtain optimized quantization values ​​in dependent quantization. Block-wise, quantization candidates for all coefficients in the block are arranged in a trellis graph, and the optimal trellis path between the optimized quantization candidates is searched for by considering the cost for rate-distortion. Specifically, dependent quantization applied to video coding can be designed so that the set of allowable reconstructed transform coefficients for a transform coefficient depends on the value of the transform coefficient preceding the current transform coefficient in the restoration order. At this time, by selectively using multiple quantizers according to the transform coefficients, the average error between the original image and the reconstructed image can be minimized, thereby increasing the encoding efficiency.

[0158] Among intra prediction encoding techniques, the Matrix Intra Prediction (MIP) method is a matrix-based intra prediction method. Unlike prediction methods that have directionality from pixels in neighboring blocks adjacent to the current block, it is a method of obtaining a prediction signal using a predefined matrix and offset values ​​for pixels on the left and top of neighboring blocks. In the MIP method, the matrix can be a matrix vector.

[0159] To derive the intra-prediction mode of the current block, a template, which is a random region adjacent to the current block and reconstructed, is used. The intra-prediction mode derived from the template's surrounding pixels can be used to reconstruct the current block. First, the decoder generates a prediction template for the template using the surrounding pixels (reference) adjacent to the template. The intra-prediction mode that generates the prediction template most similar to the already reconstructed template can then be used to reconstruct the current block. This method is called TIMD (Template intra-mode derivation).

[0160] Typically, an encoder can determine a prediction mode for generating a prediction block and generate a bitstream containing information about the determined prediction mode. A decoder can parse the received bitstream to set an intra-prediction mode. At this time, the bit amount of information about the prediction mode may be about 10% of the total bitstream size. To reduce the bit amount of information about the prediction mode, the encoder may not include information about the intra-prediction mode in the bitstream. Accordingly, the decoder can derive (determine) an intra-prediction mode for restoring the current block using the characteristics of the surrounding blocks, and can restore the current block using the derived intra-prediction mode. At this time, the decoder can use a method of applying a Sobel filter in the horizontal and vertical directions to each neighboring pixel (pixel) of the current block to infer directional information, and then mapping the directional information to the intra-prediction mode to derive the intra-prediction mode. The method by which the decoder derives the intra prediction mode using surrounding blocks can be described as Decoder side intra mode derivation (DIMD).

[0161] If the current block is a luminance block, the video signal processing device can derive an intra prediction mode through the DIMD and TIMD methods. If the current block is a chroma block, since a corresponding reconstructed luminance block exists, the video signal processing device can derive an intra prediction mode by applying the DIMD and TIMD methods using the reconstructed luminance block, and then use the intra prediction mode as an intra prediction mode of the chroma block. That is, the video signal processing device can derive directional information if the current block is a luminance block, and can not derive directional information if the current block is a chroma block, and can apply the directional information found in the luminance block to the chroma block. This mode can be referred to as a "DIMD Chroma" mode or a "TIMD Chroma" mode.

[0162] CCLM (Cross-component linear model) is a method of constructing a linear model by utilizing the high correlation between a luminance signal and a chrominance signal located at the same location as the luminance signal, and then predicting the chrominance signal through the linear model.

[0163] CCCM (Convolutional cross-component model) is a method of constructing a nonlinear model by utilizing the high correlation between a luminance signal and a chrominance signal located at the same location as the luminance signal, and then predicting the chrominance signal through the nonlinear model.

[0164] GLM (Gradient Linear Model) is a method of constructing a model by additionally reflecting the slope of luminance samples in a linear model such as CCLM, and then predicting the color difference signal through the model.

[0165] Figure 7 is a diagram showing the locations of surrounding blocks used to construct a motion candidate list in inter prediction.

[0166] The neighboring blocks can be blocks of spatial position or blocks of temporal position. The neighboring block spatially adjacent to the current block can be at least one of a left (A1) block, a left below (A0) block, an above (B1) block, an above right (B0) block, and an above left (B2) block. The neighboring block temporally adjacent to the current block can be a block that includes an upper left pixel position of a bottom right (BR) block of the current block in a corresponding picture (Collocated picture). If the neighboring block temporally adjacent to the current block is encoded in intra mode or the neighboring block temporally adjacent to the current block exists in an unusable position, a block that includes a horizontal and vertical center (Center, Ctr) pixel position of the current block in the picture corresponding to the current picture (Collocated picture) can be used as the temporal neighboring block. Motion candidate information derived from corresponding pictures can be referred to as a Temporal Motion Vector Predictor (TMVP). Only one TMVP can be derived from a single block, or a block can be divided into multiple sub-blocks, and then a separate TMVP candidate can be derived for each sub-block. The method for deriving TMVPs at the sub-block level can be referred to as a sub-block Temporal Motion Vector Predictor (sbTMVP).

[0167] Whether the methods described in this specification are applied can be determined based on at least one of information about the slice type (e.g., whether it is an I slice, a P slice, or a B slice), whether it is a tile, whether it is a subpicture, the size of the current block, the depth of the coding unit, whether the current block is a luminance block or a chrominance block, whether it is a reference frame or a non-reference frame, the temporal hierarchy according to the reference order and layer, etc. The information used to determine whether the methods described in this specification are applied can be information agreed upon in advance between the decoder and the encoder. In addition, such information can be determined according to a profile and a level. Such information can be expressed as a variable value, and information about the variable value can be included in the bitstream. That is, the decoder can determine whether the above-described methods are applied by parsing information about the variable value included in the bitstream. For example, whether the above-described methods are applied can be determined based on the horizontal length or the vertical length of the coding unit. The above-described methods can be applied if the horizontal or vertical length is 32 or more (e.g., 32, 64, 128, etc.). In addition, the above-described methods can be applied if the horizontal or vertical length is less than 32 (e.g., 2, 4, 8, 16). In addition, the above-described methods can be applied if the horizontal or vertical length is 4 or 8.

[0168] In this specification, the term "block" may be used interchangeably with "sample." Furthermore, the methods (examples) described herein may be applied at least at one of the CU, PU, ​​or TU levels, and the level at which the methods are applied and whether they are used may be indicated by separate information (e.g., syntax elements within a bitstream).

[0169] FIG. 8 is a diagram showing the relationship between a luma sample and a chroma sample according to one embodiment of the present invention.

[0170] Fig. 8 shows the positional relationship between luma samples and chroma samples in the horizontal and vertical directions. In addition, Fig. 8 shows the ratio relationship between luma samples and chroma samples. X in Fig. 8 may mean a luma sample, and O may mean a chroma sample.

[0171] Fig. 8(a) shows the positions of luma samples and chroma samples when the chroma format (relationship between luma samples and chroma samples) is 4:2:0 (or 4:1:1). There can be one corresponding chroma sample (Cb, Cr) for every four luma samples. Fig. 8(b) shows the positions of luma samples and chroma samples when the chroma format is 4:2:2. There can be two corresponding chroma samples for every four luma samples. Fig. 8(c) shows the positions of luma samples and chroma samples when the chroma format is 4:4:4. There can be four corresponding chroma samples for every four luma samples. One chroma sample can be located at the same position for each luma sample.

[0172] FIG. 9 is a diagram showing a reference sample required for Cross-component Linear Model (CCLM) prediction according to one embodiment of the present invention.

[0173] When a first color component and a second color component corresponding to a current block exist, the second color component can be predicted and / or restored based on the first color component. At this time, a model for the relationship between the first color component and the second color component can be used. That is, the second color component can be predicted and / or restored through the first color component based on the model for the relationship between the first color component and the second color component. The model for the relationship between the first color component and the second color component can be modeled from samples of the first color component that have already been restored and samples of the second color component that have already been restored. At this time, the samples of the first color component that have already been restored and the samples of the second color component that have already been restored can be samples around the current block. The second color component can be predicted and / or restored using the first color component that has already been restored based on the model for the relationship between the first color component and the second color component. At this time, the first color component can be a luma component, and the second color component can be a chroma component. Additionally, depending on the decoding and encoding order, the first color component may be a chroma component and the second color component may be a luma component. Additionally, the first color component and the second color component may be any one of the Y, U, and V components. Additionally, the first color component may refer to multiple color components.

[0174] CCLM prediction can be used for chroma intra prediction. Video compression performance can be more efficient if cross-component correlations existing in YUV 4:2:0 sequences are utilized. To reduce cross-component redundancy, in CCLM prediction, the chroma sample(s) of the current block can be predicted and / or reconstructed based on the reconstructed luma sample(s) of the current block. In this case, a linear model described below can be used. The linear model of this specification can be expressed by a linear equation, a linear equation, etc.

[0175]

[0176] Mathematical expression 1 represents a linear model used when restoring chroma samples based on already restored luma samples.

[0177] In mathematical expression 1, predC(i, j) may refer to the predicted value of the chroma sample at position (i, j) of the current block, and recL(i, j) may refer to the value of the already restored luma sample at position (i, j) of the current block. The upper left position of the current block may be (0, 0).

[0178] If the chroma sample density is lower than the luma sample density (e.g., YUV 4:2:0 image), the already restored luma sample may be a downsampled luma sample. Downsampling may mean the process of matching the number of luma samples to the number of chroma samples when the number of luma samples and chroma samples is not 1:1, as shown in Fig. 8(c). The value of the downsampled luma sample may be obtained by performing a weighted average according to a 6-tap filter (see Fig. 15). Parameters of Equation 1 and can be a value to minimize the regression error between the reconstructed luma sample (or downsampled luma sample) and the chroma sample around the current block. Parameter is a parameter based on mathematical expression 2 can be obtained based on mathematical formula 3.

[0179]

[0180]

[0181] In Equations 2 and 3, L(n) and C(n) can be reference samples of CCLM. In addition, L(n) in the above equation can be modeled (e.g., parameter Come on Here, L(n) denotes the reconstructed luma sample used in the process of acquiring the current block, and C(n) may denote the reconstructed chroma sample used in modeling. If the number of luma samples and the number of chroma samples are different, the luma sample may be downsampled and used. L(n) and C(n) may be samples around the current block (neighborhood). N may be the number of L(n) and C(n) pairs. Specifically, L(n) denotes the downsampled reconstructed luma samples on the top and left of the current block, C(n) denotes the chroma samples on the top and left of the current block, and N may denote twice the minimum value among the width and height of the coding block of the current chroma coding block. A video signal processing device (e.g., an encoder or decoder) may downsample neighboring samples on a longer boundary to have the same value as the sample value on a shorter boundary for a non-square compressed block. Equations 2 and 3 are parameters. and This is just an example to obtain the parameter and can be obtained by other methods than the above-described mathematical formulas 2 and 3.

[0182] FIG. 10 is a diagram showing a mode in which CCLM is applied according to one embodiment of the present invention.

[0183] CCLM can be classified into various modes (Fig. 10(a) to Fig. 10(c)) depending on how the three reference samples are configured. At this time, CCLM can have a mode that basically uses one linear model (Mode 1 to Mode 3). Additionally, CCLM can have a mode that uses two linear models (Mode 4 to Mode 6). Including the mode that uses two linear models, CCLM can be classified into six modes. Referring to Fig. 10(a), the reference sample for CCLM can be the reference block (sample) above and the reference block to the left of the current block. Referring to Fig. 10(b), the reference sample for CCLM can be the reference block above the current block. Referring to Fig. 10(c), the reference sample for CCLM can be the block to the left of the current block. In the CCLM mode using the reference sample configured as in Fig. 10(a) to Fig. 10(c), one or two linear models can be used. The CCLM mode (mode 1) using the reference sample according to Fig. 10(a) and using one linear model can be indicated whether to use it by a syntax element included in the bitstream, and at this time, the syntax element can be expressed as LM_CHROMA_IDX. The CCLM mode (mode 2) using the reference sample according to Fig. 10(b) and using one linear model can be indicated whether to use it by a syntax element included in the bitstream, and at this time, the syntax element can be expressed as MDLM_T_IDX. The CCLM mode (mode 3) using the reference sample according to Fig. 10(c) and using two linear models can be indicated whether to use it by a syntax element included in the bitstream, and at this time, the syntax element can be expressed as MDLM_L_IDX.In addition, the CCLM mode (mode 4) using a reference sample according to Fig. 10(a) and using two linear models can be indicated whether to be used by a syntax element included in the bitstream, and the syntax element can be expressed as MMLM_CHROMA_IDX. The CCLM mode (mode 5) using a reference sample according to Fig. 10(b) and using two linear models can be indicated whether to be used by a syntax element included in the bitstream, and the syntax element can be expressed as MMLM_T_IDX. The CCLM mode (mode 6) using a reference sample according to Fig. 10(c) and using two linear models can be indicated whether to be used by a syntax element included in the bitstream, and the syntax element can be expressed as MMLM_L_IDX. When two linear models are used, each linear model can be a linear model for each group, when the two groups are divided according to the average value of the (downsampled) luma component reference sample values. In the present specification, when the chroma format is not 4:4:4, the luma component reference sample for CCLM can be a downsampled sample to match the ratio of chroma samples to luma samples to 1:1.

[0184] In addition, the configuration of the reference block used for CCLM described through FIG. 10 (e.g., when using the left block of the current block, when using the upper block of the current block, when using both the left and upper blocks of the current block, etc.) can also be applied to CCCM. For example, it can be divided into three modes depending on the reference block used for CCCM. The reference block for CCCM can be described in i) CCCM-LT mode if it is the left block and upper block of the current block, ii) CCCLM-L mode if it is the left block of the current block, and iii) CCCM-T mode if it is the upper block of the current block. At this time, the reference block can also be expressed as a template. For example, the upper block of the reference block can be described as an upper template, and the left block of the reference block can be described as a left template.

[0185] FIG. 11 is a diagram illustrating a CCLM mode using two linear models according to one embodiment of the present specification.

[0186] The average value of reference samples (luma component or chroma component) for CCLM can be a threshold value for obtaining a linear model. At this time, there can be more than one threshold value. Referring to Fig. 11, reference samples can be divided into multiple groups based on the threshold value, and a video signal processing device can obtain a linear model for each group. The threshold value can also be applied to an already restored luma component block of the current block. Using Equation 4, which is a linear model obtained based on the threshold value, predC(i, j), which is a predicted value of a chroma block, can be obtained.

[0187]

[0188] Referring to Fig. 11 and mathematical expression 4, a first linear model can be obtained based on luma component reference samples having values ​​less than the average value, and a second linear model can be obtained based on luma component reference samples having values ​​greater than the average value. At this time, the parameters of the first linear model is 2, can be 1. The parameters of the second linear model is 1 / 2, can be 1.

[0189] The method of using two linear models can also be applied to CCCM. The video signal processing device can obtain the average value of the luminance sample based on the reference region sample values ​​of the CCCM, derive two CCCM models based on the average value, and then predict the chrominance block. The method of using two linear models in CCCM can be described as MM-CCCM (Multi-Model CCCM). MM-CCCM (Multi-Model CCCM) is a method of deriving two CCCM parameters based on the average value of the reference region (or the restored current luminance block).

[0190] GL-CCCM (Gradient and location based convolutional cross-component model) is an additional CCCM mode that uses gradient and location information. In the case of the existing CCCM mode, the video signal processing device can derive the chrominance sample for the current block using the luminance sample at the corresponding position from the predicted chrominance sample position, four samples around the luminance sample, and coefficient information. At this time, in the case of the GL-CCCM mode, the video signal processing device can derive the chrominance sample for the current block by reflecting the vertical and horizontal differences for the luminance sample at the corresponding position from the predicted chrominance sample position and eight samples around the luminance sample, and also using the position value of the current luminance sample and its coefficient information.

[0191] When CCCM mode is applied, the video signal processing device can apply a downsampling filter to match the resolution difference between the luminance block and the chrominance block. This is to reduce the resolution of the luminance block to that of the chrominance block. The mode that applies the downsampling filter can be described as CCCM-MDF (CCCM with multiple downsampling filters).

[0192] When the inter-coding mode is applied to the current block, the video signal processing device can derive linear and nonlinear models between the luminance prediction block (Y') derived using the motion information of the current block and the first chrominance prediction block (Cb', Cr') derived using the motion information of the current block (Derive filter), and then generate a reconstructed luminance block of the current block using the luminance residual block of the current block, and apply the derived linear and nonlinear models to the reconstructed luminance block of the current block (Apply filter) to generate a second chrominance prediction block of the current block. Thereafter, the video signal processing device can add the chrominance residual block to the second chrominance prediction block of the current block predicted using the linear and nonlinear models to finally generate the chrominance block (Cb, Cr) of the current block. This method can be described as a cross-component residual model (CCRM).

[0193] Fig. 12 is a drawing showing a division structure of a block according to one embodiment of the present invention.

[0194] Fig. 12(a) shows the QTBT partition structure of a luma component block in an I slice which is YUV 4:2:0, and Fig. 12(b) shows the chroma QTBT partition structure in an I slice which is YUV 4:2:0. The luma component block and the chroma component block can be partitioned into different structures depending on the partitioning form. If the partitioning form is a single tree, the luma component block and the chroma component block can be partitioned into the same structure, and in this case, the chroma component block and the luma component block can correspond 1:1. If the partitioning form is a separate tree, the luma component block and the chroma component block can be partitioned into different structures, as shown in Fig. 12, and in this case, the chroma component block and the luma component block may not correspond 1:1. The chroma block (gray shaded part) of Fig. 12(b) and the corresponding luma block (gray shaded part) of Fig. 12(a) have different partitioning structures.

[0195] In predicting a chroma component block using a luma component block, if the splitting form is a single tree, the prediction mode of the luma component block stored in the upper left position (TL) of Fig. 12(a) can be used, and if it is a separate tree, the prediction mode of the luma component block stored in the center position (CR) of the luma component block corresponding to the left block (recovery shaded portion) of the chroma component block of Fig. 12(b) can be used.

[0196] Additionally, the video signal device can determine whether a block vector exists at a preset position of a luma block corresponding to a chroma block. A block vector may exist for a block coded in IBC mode or Intra TMP mode.

[0197] If there is a block coded with Intra Block Copy (IBC) or Intra Template Matching (Intra TMP), a block vector may exist. The video signal processing device can search for a template matching block based on a template cost within a preset region based on a template composed of neighboring samples of the current block, for a current block coded with the Intra TMP mode. The video signal processing device can use the luma block of the matching block as a prediction value. The video signal processing device can derive a block vector based on the positional relationship between the matching block position and the current block. The video signal processing device can predict a chroma block using a reference block at a position indicated by the block vector and the template of the reference block. At this time, the video signal processing device can use a method such as CCCM / MM-CCCM / CCLM / GLM / GL-CCCM / CCP merge / CCCM-ND / CCCM-MDF to predict the chroma block.

[0198] FIG. 13 is a diagram illustrating a method for optimizing a linear model for CCLM according to one embodiment of the present invention.

[0199] Figure 12(a) is the mathematical expression 1 described above. and , and Fig. 12(b) is a drawing obtained to optimize the linear model. and This is a drawing showing the obtained for optimization. and are each in mathematical formula 1 and can be replaced, and the linear model can be as shown in Equation 5.

[0200]

[0201] Is + can be obtained with u, Is -u *yr can be obtained. At this time, u is an integer value between -4 and 4, which may be a value signaled by a syntax element included in the bitstream. In addition, the u value may be a preset value. y r may be the mean (or median, mode) of the (downsampled) luma component reference sample.

[0202] FIG. 14 is a diagram illustrating a gradient linear model (GLM) according to one embodiment of the present invention.

[0203] Fig. 14(a) shows the weight values ​​of the downsampling filter used when the chroma format is not 4:4:4. As shown in the right drawing of Fig. 14(c), the size of the current block may be 8x8, and the chroma format may be 4:2:0. The video signal processing device may multiply the values ​​of six reference samples (151) located above the current coding block of Fig. 14(c) by the filter weight values ​​corresponding to each of the six values, and obtain an average value thereof. At this time, the downsampled luma samples may be the left block of Fig. 14(c). One chroma sample may be located per position of each downsampled luma sample, and may correspond 1:1. Through the above-described method, the video signal processing device may obtain downsampled luma samples.

[0204] Below, a method is described for obtaining a GLM linear model based on the gradient value of a luma sample and obtaining a predicted value (C(i, j)) of a chroma sample of the current block using the GLM linear model.

[0205] The GLM linear model can be set to Equation 6 or Equation 7 for each current block depending on the condition. The condition may be a condition based on a cost value.

[0206]

[0207]

[0208] Mathematical formulas 6 and 7 and is the same as the value of the CCLM linear model of the above-described mathematical expression 1, and G(i, j) may be a gradient value corresponding to the already restored luma samples. recL(i, j) may be a value of the downsampled luma sample.

[0209] Mathematical expression 6 can be replaced with mathematical expression 8, and mathematical expression 7 can be replaced with mathematical expression 9.

[0210]

[0211]

[0212] B in mathematical expression 8 is the median value of the bit depth of the content, and chromaMean may be the average value of the chroma component reference samples. midValue in mathematical expression 9 is the median value of the bit depth of the content, and may be 512 when the bit depth is 10-bit. In addition, midValue may be the average value of each chroma component reference sample. In mathematical expressions 8 and 9, may be a coefficient corresponding to the i-th already restored downsampled luma sample value located around the chroma component sample to be predicted.

[0213] A filter for obtaining a gradient value can be described as a Sobel-based gradient pattern. There may be multiple filters for obtaining a gradient value. Fig. 14(b) illustrates one of multiple filters for obtaining a gradient value. The GLM linear model can be independently applied to chroma component Cb and Cr samples, respectively. In this case, whether the GLM linear model is applied to each chroma component can be signaled by a syntax element (flag) included in the bitstream. In addition, when the GLM linear model is applied to each chroma component sample, a syntax element indicating one of the filters (multiple Sobel-based gradient patterns) for the GLM linear model can be included in the bitstream and signaled. The syntax element indicating one filter can be described by a glm index.

[0214] GLM can operate in the six modes described above of CCLM or can be restricted to operate in only specific modes. In this case, the specific modes can be LM_CHROMA_IDX, MDLM_L_IDX, MDLM_T_IDX. In addition, GLM may not be applied to some of specific intra luma prediction modes. For example, GLM may not be applied to all or some of the non-directional DC mode and the planar mode. In addition, GLM may not be applied when the intra luma prediction mode is any one of the non-directional DC mode, the planar mode, and the MIP mode. In this case, the value of the syntax element (flag) indicating whether GLM is applied can be set to 0. Two linear models can also be used in GLM. The following describes the GLM operation method and operating conditions.

[0215] The conditions for GLM to be applied are as follows.

[0216] (Condition) Chroma mode==MMLM_CHROMA_IDX || Chroma mode==MMLM_L_IDX || Chroma mode==MMLM_T_IDX) && (Luma block width * Luma block height >= Reference value 1)

[0217] Reference value 1 is a positive integer, such as 16, 32, 64, or 128. In the above condition 1, the horizontal size of the luma block can be replaced with the horizontal size of the chroma block, and the vertical size of the luma block can be replaced with the vertical size of the chroma block. In addition, reference value 1 is a value determined based on the chroma format, such as 8, 16, 32, 64, or 128.

[0218] There may be multiple filters for obtaining a slope value, and the glm index may be signaled to indicate one of the multiple filters. The video signal processing device may determine the filter for obtaining the slope value by parsing the glm index included in the bitstream. At this time, there may be 4, 8, or 16 filters for obtaining the slope value, and the glm index may indicate any one of the 4, 8, or 16 filters. The glm index may be signaled with a fixed bit size. In addition, in order to reduce signaling complexity, the glm index may be configured in a method described below rather than with a fixed bit size.

[0219] i) A video signal processing device can rearrange filter candidates that can be used as filters for obtaining a gradient value based on a reference element, and signal / parse a glm index based on the rearranged filter candidates. The reference element may be a luma prediction mode or a coding mode (e.g., Decoder-side intra mode derivation (DIMD), Template-based intra mode derivation (TIMD)) of a current block. For example, the video signal processing device can classify luma prediction modes into a plurality of groups, and rearrange filter candidates for obtaining a gradient value for each group using frequently used filter candidates. Among the rearranged candidates, a candidate with the highest frequency of use may be mapped to a lowest glm index, and the glm index may be signaled with a size of 1 bit. The luma prediction modes may be classified into a plurality of groups based on the indexes of the luma prediction modes. At this time, the luma prediction modes may be classified into groups evenly (i.e., the same number per group) or unequally (i.e., unequal number per group). The indices of luma prediction modes included in each group may be continuous. In addition, luma prediction modes may be classified based on specific indices. For example, luma prediction modes may be classified into luma prediction modes corresponding to indices that are equal to or less than (or less than) a specific index and luma prediction modes corresponding to indices that are greater than (or equal to or greater than) the specific index. At this time, the specific indices may be multiple. That is, if there is one specific index, luma prediction modes may be classified into two groups, if there are two specific indices, luma prediction modes may be classified into three groups, and if there are three specific indices, luma prediction modes may be classified into four groups. At this time, the specific indices may be 18 (horizontal direction), 34 (diagonal direction), and 50 (vertical direction).In addition, non-directional prediction modes (e.g., DC mode, planar mode) can be classified into a separate group. The glm index can be signaled using a variable length code scheme. The variable length code scheme can be a truncated unary binarization scheme. There is a problem that the amount of information increases as the value of the glm index increases. However, if the occurrence frequency of a relatively low index is high, the glm index can be signaled with a small amount of information. Table 1 shows the structure of truncated unary binarization. Referring to Table 1, as the value of the index (v) increases, the amount of information can also increase.

[0220]

[0221] ii) The video signal processing device can calculate a cost value for each of the filters for obtaining a plurality of slope values, and reorder the filters based on the cost value. The video signal processing device can sort the filters in ascending order of the cost values ​​corresponding to the filters. A filter with the smallest cost value can be mapped to the smallest glm index. The video signal processing device can signal / parse a glm index indicating any one of the reordered filters. The cost value can be calculated based on chroma component reference samples and chroma component prediction samples located at the boundary of the current block. The chroma component prediction samples located at the boundary of the current block can be samples at specific locations.

[0222] Figure 15 is a diagram showing a filter for obtaining a slope value used in GLM.

[0223] Specifically, Fig. 15 is a diagram illustrating four Sobel-based gradient patterns that can be used in GLM. The circle located at the center of each filter may be the result of the filtering.

[0224] Table 2 shows the filter values ​​of 16 Sobel-based gradient patterns that can be used in GLM.

[0225]

[0226] FIG. 16 illustrates an example of a reference region and filter shape used to derive CCCM parameters according to one embodiment of the present invention.

[0227] CCCM (Convolutional cross-component intra prediction model) is a method for predicting chroma blocks using a nonlinear model that utilizes the high correlation between a luma block (luma component block, luma component sample, luma sample) and a chroma block located in the same location as the luma block. In other words, a video signal processing device can predict a chroma component sample corresponding to a luma component sample of the current block using a luma component sample of the current block. Then, the video signal processing device can restore the current block using the value of the predicted chroma component sample.

[0228] FIG. 16(a) shows the positional relationship between reference samples (vertical hatching, 161) for applying CCCM to a current prediction block (diagonal hatching, 162) according to one embodiment of the present invention and side samples (horizontal hatching) required when applying a cross-shaped filter. When the size of the current prediction block (162) is M (width) x N (height) and the number of luma component samples and chroma component samples is 1:1, the reference samples (161) may be configured as a reference sample area (161-1) of 2M x 6 size in the upper 6 rows with a size twice that of the width of the current prediction block (162), a reference sample area (161-2) of 6 x 2N size in the left 6 rows with a size twice that of the height of the current prediction block (162), and a reference sample area (161-3) of 6 x 6 size in the upper left of the current prediction block (162). That is, when the coordinates of the upper left sample of the current prediction block (162) are (0, 0), 161-1 may be (X1, Y1), 161-2 may be (X2, Y2), and 161-3 may be (X3, Y3). At this time, X1 may be a value from 0 to 2M-1, Y1 may be a value from -1 to -6, X2 may be a value from -1 to -6, Y2 may be a value from 0 to 2N-1, and X3 and Y3 may be values ​​from -1 to -6.

[0229] Fig. 16(b) illustrates a sample of a cross-shaped pattern according to an embodiment of the present invention. In the present specification, a sample of any shape pattern can be expressed as a sample filter. When the sample filter of the cross-shaped pattern of Fig. 16(b) is used for CCCM, the area where the filter is applied may be outside the reference sample area. In this case, an additionally required sample may be a side sample. Depending on the position of the C sample of Fig. 16(b), an area other than the reference sample may be required when the sample filter of the cross-shaped pattern is applied. In this case, if the area other than the reference sample is not available, the value of the area other than the reference sample may be padded with the value of the C sample and used. The sample at the C (Center) position of Fig. 16(b) may be a luma sample corresponding to the Cb and Cr chroma samples, and N (North), E (East), S (South), and W (West) may be luma samples adjacent to the luma sample at the C position. CCCM can be applied to each chroma component (i.e., Cb component, Cr component). Side samples may require one additional sample for areas other than the reference sample, depending on the location of the C sample. If the sample value existing at the location of the side sample is not available, the sample value at the unavailable location may be padded with the C sample value.

[0230] When a cross-shaped pattern sample filter for CCCM is applied, the predicted value (predChromaVal) of the chroma component sample can be calculated as in Equation 10.

[0231]

[0232] The P value in Equation 10 is a nonlinear term and can be calculated as ( C * C + midVal ) >> bitDepth . midValue can be the median value of the content bitdepth or the average value of each chroma component. bidDepth can represent the bit depth. In content with a bitDepth of 10 bits, the P value can be calculated as ( C * C + 512 ) >> 10 . The B value represents a bias term, an integer offset value, and can be the median value of the bitDepth content. In the case of 10-bit content, the B value can be 512. In addition, the B value can be the average value of the chroma component reference sample. In addition, the B value can be the (absolute value) difference between the average value of the luma component reference samples and the average value of each chroma component reference sample. C, N, S, E, and W can represent sample values ​​according to the positions in Fig. 16(b). The coefficients (C0, C1, ..., C6) of Equation 10 may be values ​​that minimize the MSE (Mean Square Error) value of the autocorrelation matrix for the luma component sample values ​​of the reference sample area and the cross-correlation vector for the chroma component sample values. The autocorrelation matrix may be obtained using LDL decomposition or Cholesky decomposition. In addition, the coefficients (C0, C1, ..., C6) of Equation 10 may be obtained using back-substitution.

[0233] C, N, S, E, W, P in Equation 10 can be replaced with C', N', S', E', W', P', respectively. C', N', S', E', W', P' can be calculated as follows.

[0234] C' = C - meanY, N' = N - meanY, S' = S - meanY, E' = E - meanY, W' = W - meanY, P' = P - meanNonlinY

[0235] meanY can be the average value of the luma component reference samples. meanNonlinY can be calculated as follows.

[0236] meanNonlinY = (meanY * meanY) >> bitdepth or meanNonlinY = (meanY * meanY + bitdepth>>1) >> bitdepth

[0237] Mathematical expression 10 can be changed to mathematical expression 11.

[0238]

[0239] Mathematical expression 11 may be in the form where C, N, S, E, W, P, and B in Mathematical expression 10 are replaced with C', N', S', E', W', P', and B', and meanChroma is added. meanChroma may be the average value of chroma component reference samples. B' in Mathematical expression 11 may be the (absolute value) difference between the average value of the luma component reference sample and the average value of each chroma component reference sample.

[0240] Depending on the luma samples used for CCCM, Equation 11 can be modified. For example, if only C, N, S, and E are used among C, N, S, E, and W, Equation 11 can be modified to a form that excludes the term corresponding to W (c4W'). Furthermore, Equation 11 can be modified to a form that excludes B'.

[0241] In addition, C', N', S', E', and W' in Equation 11 may be result values ​​according to any one pattern (filter) among multiple Sobel-based gradient patterns. That is, C', N', S', E', and W' in Equation 11 may be replaced with gradient values.

[0242] Additionally, the P value in Equation 10 can be changed as follows.

[0243] i) The P value can be obtained according to ( Cg * Cg + midVal ) >> bitDepth. Cg can be the gradient value of the sample at position C in Fig. 16(b). midVal can be the middle value of bitDepth, and in content with bitDepth of 10 bits, midVal can be 512. ii) The P value can be the average value of the gradient values ​​of the reference samples. iii) The P value can be the average value of the gradient values ​​at positions (C, N, E, S, W) in Fig. 16(b). iv) The P value can be obtained according to (meanG * meanG + bitDepth >> 1) >> bitdepth. meanG can be the average value of the gradient values ​​of the reference samples.

[0244] In addition, Fig. 16(c) shows the positional relationship of samples for the GL-CCCM mode. The video signal processing device can apply the GL-CCCM mode using the sample positional relationship of Fig. 16(c). The sample corresponding to each position in Fig. 16(c) is a down-sampled value according to the luma and chroma composition ratio, and the luma sample at position C can be a sample corresponding to the chroma to be predicted. The GL-CCCM (Gradient and location based convolutional cross-component model) mode can be a CCCM mode using gradient and position information. Mathematical expression 12 is a mathematical expression used in GL-CCCM.

[0245]

[0246] The video signal processing device can derive coefficients using the CCCM method using the luminance sample value at the C position in Fig. 16(c) and Gx (horizontal slope, horizontal difference), Gy (vertical slope, vertical difference), Y (value based on the vertical coordinate of C), X (value based on the horizontal coordinate of C), P, and B as input values, and generate a chroma prediction sample value. If the upper left position of the reference template used to derive the CCCM model, the upper left position of the current block, and the upper left position of the current block are (0,0), the position value of the current luminance sample corresponding to the values ​​of Y and X can be a value recalculated through the relative position of the current pixel, an arbitrary offset value, and an arbitrary shift value. At this time, the position value of the current luminance sample can be calculated through the relative position value of the current pixel + the difference value between the upper left position of the reference template used to derive the CCCM model at the upper left position of the current block + an arbitrary offset value) << an arbitrary shift value). At this time, the arbitrary offset value can be an integer and can be '8'. Additionally, the arbitrary shift value can be an integer, and can be '3'. In addition, Gx and Gy can be calculated using Equation 13 using the samples of Fig. 16(c).

[0247]

[0248] Below, when the chroma format is 4:2:2, the downward sampling process to match the number of chroma samples to the number of luma samples to 1:1 is described.

[0249] As explained through Figure 14, luma samples can be converted by applying a downsampling filter (Figure 14(a)) to the same number as the number of chroma samples.

[0250] Mathematical expression 13 is a filter-based linear model (FLM) used for downsampling.

[0251]

[0252] C in mathematical expression 14 is the value of the chroma component sample to be predicted, L i is the value of the i-th restored downsampled luma component sample located around the chroma component sample to be predicted, is L i The coefficient values ​​corresponding to can be obtained by using the method of calculating the coefficients (C0, C1, ..., C6) of the above-described mathematical expression 10. is an offset, N can be the number of luma component samples required to calculate the value of the chroma component sample to be predicted. The value of N can be an integer between 2 and 6, and can be 2 or 6. In mathematical expression 14, it can be replaced with a gradient value which is a result value for one of the multiple Sobel-based gradient patterns.

[0253] Figures 17 and 18 illustrate luminance samples before downsampling used to derive chrominance samples in CCCM-ND mode according to one embodiment of the present invention.

[0254] CCCM-ND (CCCM using non-downsampled luma samples) mode may be a method of predicting a chrominance block using samples of a luminance block before downsampling. Fig. 17 shows a chrominance sample position C to be predicted by a video signal in CCCM-ND mode and six luminance sample positions corresponding to the chrominance sample positions. At this time, the luminance samples may be samples before downsampling. The chrominance sample may be calculated using Equation 15. The chrominance sample may be calculated using a linear model using six luminance samples (L0, L1, L2, L3, L4, L5 samples of Fig. 17) and a non-linear model using four luminance samples (L0, L3, L2, L1 samples of Fig. 17). In Equation 15, offsetLuma and offsetchroma have the same meaning as the difference value described above. B can be calculated as '1 << (bitDepth - 1)'. The LDL decomposition method used in CCCM can be used to derive the coefficients (a0 ~ a10).

[0255]

[0256] The encoder can signal whether CCCM-ND is applied to the current block by including information in the bitstream. The decoder can parse this information to determine whether CCCM-ND is applied to the current block.

[0257] If CCCM-ND is applied to the current block, the encoder may not include information about GL-CCCM in the bitstream. If CCCM-ND is applied to the current block, the decoder may not parse information related to GL-CCCM and may set GL-CCCM not to be applied to the current block.

[0258] When GL-CCCM is applied to the current block, the video signal processing device derives a model for GL-CCCM using the downsampled luminance samples, and predicts chrominance samples for the current block using the downsampled luminance samples of the current block. At this time, in GL-CCCM, as in CCCM-ND, luminance samples before downsampling can be used to derive a model or predict chrominance samples.

[0259]

[0260] A chrominance sample can be predicted (calculated) through mathematical expression 16. The video signal processing device can derive a chrominance sample for the current block by reflecting a linear model using six luminance samples (luminance samples L0, L1, L2, L3, L4, L5 of FIG. 17) and a non-linear model using four luminance samples (luminance samples L0, L3, L2, L1 of FIG. 17), a luminance sample at a corresponding position at the chrominance sample position to be predicted, and vertical and horizontal differences (Gx, Gy in mathematical expression 16) for samples around the luminance sample (luminance samples L1 to L8 of FIG. 17), and also using the position value (X, Y in mathematical expression 16) of the current luminance sample and coefficient information. At this time, the video signal processing device can calculate Gx and Gy through mathematical expression 17. Mathematical expression 17 can be used for the samples of FIG. 17. In Equation 17, offsetLuma and offsetchroma have the same meanings as the difference values ​​described above. B can be calculated as '1 << (bitDepth - 1)'. The LDL decomposition method used in CCCM can be used to derive the coefficients (a0 ~ a14).

[0261]

[0262] To predict a chrominance sample, the video signal processing device can use the luminance samples of FIG. 18 (e.g., L6, L7, L8 located below the current chrominance sample) instead of the luminance samples of FIG. 17.

[0263] The video signal processing device can use luminance samples located at a specific distance (sample) away from the luminance sample corresponding to the current chrominance sample in addition to the surrounding luminance samples for CCCM-ND. For example, when the specific distance is 1, the video signal processing device can use samples located at L0 to L8 of FIG. 18, and when the specific distance is 2, the video signal processing device can use at least one of the luminance samples located at L0 to L8 and I0 to I15 of FIG. 18.

[0264] FIG. 19 shows a downsampling filter and sample positions applied to a luminance block according to one embodiment of the present invention.

[0265] In the CCCM method of predicting a chrominance block based on a luminance block, a video signal processing device can apply various downsampling filters to reduce the resolution of the luminance block to that of the chrominance block to match the resolution difference between the luminance block and the chrominance block. The CCCM mode that applies the downsampling filters can be described as CCCM-MDF (CCCM with multiple downsampling filters).

[0266] Fig. 19(a) shows multiple downsampling filters that can be applied to a luminance block. Filtering using the H filter in Fig. 19(a) is filtering that considers the value of the current luminance sample position more important than the surrounding samples. Filtering using the G1, G2, and G3 filters in Fig. 19(a) may be filtering methods designed according to the gradient between adjacent samples. Filtering using the G1 filter may be filtering based on changes in the horizontal direction. Filtering using the G2 filter may be filtering based on changes in the vertical direction. Filtering using the G3 filter may be filtering based on changes in the diagonal direction. C in Fig. 19(b) represents the position of the current chrominance sample, and W, E, N, S, NW, NE, SW, and SE represent the positions of samples surrounding C.

[0267]

[0268] Mathematical expression 18 represents a calculation formula for deriving a chrominance sample using at least one of the down-sampled luminance samples obtained based on filtering using the H, G1, G2, and G3 filters of FIG. 19.

[0269] In Equation 18, P represents a nonlinear model and can be the square of the sample value at the corresponding location. In Equation 18, B can be half the maximum value of the current sample or an intermediate bit depth value. For 10-bit content, the value of B can be 512.

[0270] Model 1 of Equation 18 may be a mathematical formula for deriving a chrominance sample using a down-sampled luminance block obtained using four filters (using the H, G1, G2, and G3 filters of FIG. 19). Model 2 of Equation 18 may be a mathematical formula for deriving a chrominance sample using a down-sampled luminance block obtained using the H, G1 filters of FIG. 19. Model 3 of Equation 18 may be a mathematical formula for deriving a chrominance sample using a down-sampled luminance block obtained using the H, G3 filters of FIG. 19.

[0271] The encoder can select the optimal model among the three chrominance prediction blocks derived using Equation 18, and then signal information about which model is used to predict the current chrominance block by including it in the bitstream. At this time, the information about which model is used can be applied to the chrominance signal Cb and the chrominance signal Cr, respectively, on a block-by-block basis. The decoder can predict each chrominance block using the model determined by parsing the information about which model is used for each chrominance signal (Cb, Cr).

[0272] Alternatively, the encoder can select the optimal model among the three chrominance prediction blocks derived through Equation 18, and then comprehensively signal information on which model to use when predicting the current chrominance blocks for the chrominance signals (Cb, Cr) and include it in the bitstream on a block-by-block basis. The decoder can parse the information on which model to use to generate the current chrominance prediction block and apply it equally to the current Cb chrominance block and the current Cr chrominance block to generate the chrominance prediction block.

[0273] When two CCCM models are used in the current block, the video signal processing device can derive the two models based on the average value of the down-sampled luminance block generated through filtering using the H filter of Fig. 19(a).

[0274] FIG. 20 is a diagram illustrating a direct block vector according to one embodiment of the present invention.

[0275] Referring to FIG. 20, a video signal processing device can use a direct block vector (DBV) for prediction of a chroma block.

[0276] Fig. 20(a) shows the relationship between luma and chroma described through Fig. 12. Fig. 20(a) shows a chroma block and a luma block corresponding to the chroma block. At this time, the luma block may include an upper left (TL), upper right (TR), center (C), lower left (BL), and lower right (BR) region. If the luma block is coded in IBC mode or Intra TMP mode, a block vector (BV) related to the luma block may exist. The vector related to the luma block may be adjusted according to the luma and chroma sampling ratio. The video signal processing device may check whether a block vector exists at a preset position of the luma block. At this time, the preset position may be located inside the luma block or outside the luma block. For example, if the preset position is located inside the luma block, the preset position may be TL, TR, C, BL, and BR. If a block vector exists at a preset position, the video signal processing device can use the chroma reference block indicated by the block vector at the preset position as a prediction value of the current chroma coding unit (block). Referring to Fig. 20(b), the upper left position of the current block may be (xCb, yCb), and the block vector at the upper left position may be (bvC[0], bvC[1]). At this time, the position in the reference block indicated by the block vector may be (xCb+bvC[0], yCb+bvC[1]). If multiple block vectors exist, the video signal processing device can use the optimal block vector based on the TM cost. Alternatively, the video signal processing device can use only the block vector that is searched first. At this time, the order of the area that the video signal processing device searches to determine whether a block vector exists may be predetermined.

[0277] Describes the chroma fusion prediction mode.

[0278] A video signal processing device can predict a final chroma prediction sample value corresponding to a luma block by combining a weighted average of an LM mode (e.g., MM-CCLM or MM-CCCM) and a non-LM mode. At this time, the final chroma prediction sample value can be predicted using mathematical expression 19.

[0279]

[0280] Pred0(i,j) in Equation 19 may be a sample value of a block (sample, pixel) at position (i, j) in a chroma block predicted by a non-LM mode. The non-LM mode may be at least one of a DM mode, a DIMD chroma mode, and four chroma basic modes. In this case, the four chroma basic modes may be a planar mode, a DC mode, a vertical direction mode (index 18 of the angular mode), and a horizontal direction mode (index 50 of the angular mode). pred1(i,j) may be a sample value of a block at position (i, j) in a chroma block predicted by the LM mode. predC(i,j) may be a final prediction value at position (I, j) in the current chroma block. w0 and w1 may be weight values, and the shift value may be 2. The weights w0 and w1 may be determined based on a fixed ratio. The fixed ratio can be any one of 3:1, 1:3, and 2:2. For example, if both the upper and left neighboring blocks of the current coding block are coded in the LM mode, {w0, w1} can be {1, 3}, if only one of the two is coded in the LM mode, {w0, w1} can be {3, 1}, and if neither of them uses the LM mode, {w0, w1} can be {2, 2}. If there are multiple available LM modes, the video signal processing device can compare the cost values ​​of each template and use the LM mode with a lower cost value. In the non-LM mode, chroma sample(s) predicted using DBV can be used. Pred0(i,j) can be a chroma sample value predicted using DBV. The LM mode can be at least one of CCLM, CCCM, CCP merge mode, CCCM-ND, GL-CCCM, and CCCM-MDF. Alternatively, the video signal processing device can configure a new set by combining MM-CCLM and MM-CCCM, and use the mode determined based on the TM cost as the LM mode.

[0281] A video signal processing device can predict a final chroma prediction sample value using a weighted average combination of a downsampled reconstructed luma sample in an LM mode (e.g., MMLM or CCLM) and a chroma sample in the same location. At this time, the final chroma prediction sample value can be predicted using Equation 20.

[0282]

[0283] Pred0(i,j) in Equation 20 may be the value at position (i, j) of the chroma block predicted in non-LM mode, or may be the value predicted in the LM mode. rec' L (i,j) may be the downsampled restored luma sample value at the same location as the chroma and pred C (i,j) can be the final predicted value of the current chroma block. The ß value can be an intermediate value of the image bit depth. The bit depth can be 512 for 10-bit images. a0, a1, and a2 can be derived using the LDL decomposition method used in CCCM. Pred0(i,j) can be chroma samples / blocks predicted using the DBV method. rec' L (i,j) may be the value of a downsampled restored luma sample at the same location as the chroma sample within the reference block pointed to by DBV. Or, rec' L (i,j) may be a down-sampled restored luma sample value within a luma block corresponding to the current coding chroma block.

[0284] The method for predicting chroma samples derived from DBV described herein, the prediction method using a weighted average combination of samples predicted by a linear / nonlinear (LM / non-LM) model, and the method using coefficients of the CCCM method can also be applied to I(intra) slices. The sizes of coding units / coding blocks / prediction blocks / transform blocks for which these methods are applied can be determined based on a reference value.

[0285] Figures 21 and 22 show additional locations for application of DBV according to one embodiment of the present invention.

[0286] Referring to Fig. 21, a basic block vector position may be added for applying DBV to a chroma block. That is, a position for a video signal processing device to check whether a block vector exists may be added. The position of the added block vector may be determined based on the size of a Luma A block (including TL, TR, BR, and BL), which is a luma block corresponding to a Chroma A block, referring to Fig. 21. The position indicated by x in Fig. 21 may be an added position for applying DBV. If the width of the Luma A block is W1, the height is H1, and the coordinates of the upper left corner of Luma A are (0, 0), the added positions may be (-W1, 0), (-W1, -H1), (0, -H1), (-W1 / 2, H1+H1 / 2), (-W1-W1 / 2, H1+H1 / 2), (-W1-W1 / 2, H1 / 2). The block vector at the added location can be scaled according to the chroma format. If the luma-chroma sample ratio is not 1:1 (e.g., the chroma format is 4:4:4), the block vector needs to be converted. For example, if the chroma format is 4:2:2 or 4:2:0, the block vector must be resized to match the ratio.

[0287] Fig. 22 shows the positions added for searching block vectors in the chroma current block and the restored chroma sample area. If the width of the current chroma current block is W and the height is H, positions corresponding to (-W, 0), (-W, -H), (0, -H), (-W / 2, -HH / 2), (-WW / 2, -HH / 2), (-WW / 2, -H / 2) can be added. The block vectors of the added positions can be used as positions set in the restored chroma area without separate block vector conversion. In addition to the positions described through Figs. 21 and 22, positions for searching block vectors in the restored area and the search area can be set.

[0288] FIG. 23 is a diagram showing a type of conversion kernel according to one embodiment of the present invention.

[0289] Specifically, Fig. 23 shows the definition of the transform kernel used in MTS, and shows the formulas (basis functions) of the DCT-II, DCT-V, DCT-VIII, DST-I, DST-VII, and DST-IV kernels. In this specification, DCT-II can be described as DCT-2 (DCT2), DCT-V as DCT-5 (DCT5), DCT-VIII as DCT-8 (DCT8), DST-I as DST-1 (DST1), DST-VII as DST-7 (DST7), and DST-IV as DST-4 (DST4).

[0290] DCT and DST can be expressed as functions of cosine and sine, respectively, and when the basis function of the transform kernel for the number of samples N is expressed as Ti(j), the index i represents the index in the frequency domain, and the index j represents the index within the basis function. That is, as i becomes smaller, it represents a low-frequency basis function, and as i becomes larger, it represents a high-frequency basis function. When the basis function Ti(j) is expressed as a two-dimensional matrix, it can represent the j-th element of the i-th row, and since the transform kernels illustrated in Fig. 23 all have separable characteristics, they can perform transformations in the horizontal and vertical directions for the residual signal X, respectively. That is, when the residual signal block is X and the transform kernel matrix is ​​T, the transformation for the residual signal X can be expressed as TXT'. At this time, T' means the transpose matrix of the transform kernel matrix T.

[0291] The values ​​of the transform matrix defined by the basis functions illustrated in Fig. 23 may be in decimal form rather than integer form. Therefore, it may be difficult to implement decimal form values ​​in hardware in a video encoding device and a decoding device. Therefore, an integer-approximated transform kernel from an original transform kernel containing decimal form values ​​may be used for encoding and decoding a video signal. The approximated transform kernel containing integer values ​​may be generated through scaling and rounding of the original transform kernel. The integer values ​​contained in the approximated transform kernel may be values ​​within a range that can be expressed by a preset number of bits. The preset number of bits may be 8 or 10 bits. Depending on the approximation, the orthonormal properties of the DCT and DST may not be maintained. However, since the loss in encoding efficiency resulting from this is not significant, approximating the transform kernel to an integer form may be advantageous in terms of hardware implementation.

[0292] IDTR (Identity Transform) is a transformation whose result is the original original. It's called an identity transformation. Typically, an identity transformation constructs a transformation matrix by setting "1" in positions where rows and columns have the same value. However, here, the identity transformation uses a fixed, arbitrary value, not "1," to uniformly increase or decrease the value of the input residual signal.

[0293] FIG. 24 is a diagram showing the 0th (lowest frequency component of the corresponding transform kernel) basis function of DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII transforms according to one embodiment of the present invention.

[0294] Specifically, FIG. 24 is a graph of Ti(j), which is a transformation basis function of DCT / DST defined in FIG. 23, when N is 8 and i is 0. The horizontal axis represents the index j (j=0, 1, …, N-1) within the transformation basis function, and the vertical axis represents the magnitude value of the signal.

[0295] As shown in Fig. 24, DST-VII shows a tendency for the signal to increase as the index j increases, so it can be effective for a pattern of residual signals in which the energy of the residual signal increases as the distance in the horizontal and vertical directions from the upper left coordinate of the block within the residual signal block increases, as in the prediction within the screen.

[0296] On the other hand, in the case of DCT-VIII, since the signal size shows a pattern in which the size of the signal decreases as the index j increases, it can be efficient for the pattern of the residual signal in which the energy of the residual signal decreases as the distance in the horizontal and vertical directions from the upper left coordinate of the block within the residual signal block increases.

[0297] In the case of DST-I, the signal increases as the index j within the basis function increases, and then decreases in magnitude after a certain index. Therefore, it can be effective for residual signal patterns in which the energy of the residual signal increases as one moves toward the center of the residual block.

[0298] For DCT-II, the 0th basis function represents DC, and it can be efficient for patterns of residual signals with uniform pixel value distribution within the residual block, such as inter-screen prediction.

[0299] For DCT-V, it is similar to DCT-II, but since the value when j is 0 is smaller than the value when j is not 0, it has a signal model in the form of a straight line that is broken when j is 1.

[0300] Conventional video codecs that primarily use only DCT-II cannot adaptively perform transformation on the pattern of the residual signal that varies depending on the prediction mode and the characteristics of the original signal, and thus cannot achieve optimal encoding efficiency. However, adaptive multiple transform (AMT) performs transform encoding by selecting a transform kernel optimized for the pattern of the residual signal by using various transform kernels differently depending on the prediction mode, and high compression efficiency can be expected. Similar to AMT, multiple transform selection (MTS) technology is a transform encoding method that can improve encoding efficiency by adaptively selecting a transform kernel according to the prediction mode.

[0301] Below, a combination of transformation kernels according to one embodiment of the present specification is described.

[0302] DCT2 can be used as the basic transform kernel for restoring the current block. Meanwhile, if DCT2 is not used, the remaining kernels (e.g., DCT8, DST7, DCT5, DST4, DST1) can be used. If DCT2 is not used, some of the preset combinations for the remaining kernels can be used. Table 3 shows combinations of kernels excluding DCT2 and IDTR among the transform kernels disclosed in FIG. 23. That is, Table 3 shows combinations of five types of kernels (DCT8, DST7, DCT5, DST4, DST1). Specifically, Table 3 shows 25 combinations that can be configured by making one pair (combination) of two transform kernels. A video signal processing device (e.g., decoder, encoder) can use any one of the 25 combinations in Table 3 as a transform kernel for the horizontal or vertical direction of the current block. Meanwhile, IDTR can only be used when certain conditions are met.

[0303]

[0304] FIG. 25 and FIG. 26 are diagrams showing a set of transformation kernels according to one embodiment of the present invention.

[0305] Referring to FIG. 25, a set of transformation kernels determined based on the intra prediction mode of the current block and the size of the current block is described.

[0306] Referring to FIG. 25, the transform kernel used in the intra prediction mode can be determined based on the intra prediction mode and the size of the current block (e.g., coding block, transform block). In addition, FIG. 25 can represent a transform kernel set for MIP. 2501 of FIG. 25 represents the type of intra prediction mode (i.e., an index indicating the intra prediction mode), and 2502 represents the size (i.e., width x height) of the current block (e.g., coding block, transform block). For example, when the size of the current block is 4x4 and the type of intra prediction mode is 1, the transform kernel for the current block can be determined based on the transform kernel set corresponding to index 0. The transform kernel set corresponding to index 0 can be T0 {18, 24, 17, 23, 8, 12} with reference to FIG. 26. And, the video signal processing device can restore the current block based on the transformation kernel (sub-transform kernel set) included in the transformation kernel set corresponding to any one index of T0. There are six indices corresponding to the transformation kernel (sub-transform kernel set) included in the transformation kernel set of Fig. 26, but this is only an example and there may be four.

[0307] Fig. 26(a) shows a transform kernel set composed of indices corresponding to six transform kernels. Fig. 26(a) is a diagram showing some of 80 transform kernel sets composed of indices corresponding to six transform kernels. Similarly, each index constituting the transform kernel set of Fig. 26(a) may correspond to any one of the transform kernel combinations (sub-transform kernel sets) of Table 3. For example, the 25 combinations of Table 3 may be indexed from 0 to 24, respectively, and an index included in any one of the transform kernel sets of Fig. 26 may correspond to a combination of Table 3. The transform kernel set of Fig. 26(a) may be determined based on the size of the current block (coding block, transform block) and the intra prediction mode of the current block. Fig. 26(b) is a diagram showing the first transform kernel set (T0) among the transform kernel sets of Fig. 26(a). The indices of the transformation kernel set can be grouped into multiple groups based on a preset convention. That is, the number of indices of the transformation kernel set to be grouped can be adaptively set. At this time, the group can be composed of three or more. Referring to Fig. 26(b), the indices of the transformation kernel set can be grouped based on multiple reference values ​​(e.g., a first reference value, a second reference value). For example, if the grouping value is less than or equal to the first reference value, a group including one index (18) is selected. If the grouping value is greater than the first reference value and less than or equal to the second reference value, a group including four indices (18, 2, 17, 23) is selected. If the grouping value is greater than the second reference value, a group including six indices (18, 24, 17, 23, 8, 12) can be selected. If the grouping value is compared to the reference value and the corresponding group is selected as per the pre-promised settings, there may be an effect of reducing complexity compared to signaling / parsing one of the six indices (transformation kernels) for the current block.At this time, the reference value may be the sum of the conversion coefficients, and the first reference value and the second reference value may be determined based on the sum of the conversion coefficients. For example, the first reference value may be 6, and the second reference value may be 32.

[0308] Separate signaling may be required to indicate the indices included in the group selected by comparing the reference value and the grouping value. For example, as shown in Fig. 26(b), if the grouping value is greater than the first reference value and less than or equal to the second reference value, the selected group may be the group consisting of indices (18, 24, 17, 23). In this case, separate signaling may be required to indicate each of the four indices. Similarly, if the grouping value is greater than the second reference value, the selected group may be the group consisting of indices (18, 24, 17, 23, 8, 12). In this case, separate signaling (mts_idx) may be required to indicate each of the six indices. The indices within the transform kernel set may be indicated by the mts_idx described above. In this case, mts_idx may have a fixed bit size. For example, mts_idx for six indices may have a 3-bit size. Alternatively, mts_idx can be signaled using the Truncated Unary Binarization (TB) method. mts_idx can be coded using the TB method, with context-model-based CABAC coding applied to the first bin and TB-based CABAC coding applied to the remaining bins.

[0309] Meanwhile, if the grouping value is equal to or less than the first reference value, the selected group may be a group composed of the indices of (18). In this case, since the group is composed of only one index, separate signaling to indicate one index may not be necessary.

[0310] FIG. 27 is a diagram illustrating a process for restoring a residual signal according to one embodiment of the present invention.

[0311] The residual signal, which is the difference between the original signal and the predicted signal, has the characteristic that the energy distribution of the signal changes depending on the prediction method. Therefore, if the transform kernel is adaptively selected according to the prediction method, such as MTS, the encoding efficiency can be improved. In addition, if the transform using only MTS or DCT2 kernels is called a first transform, the video signal processing device can also improve the encoding efficiency by additionally performing a second transform on the first-transformed coefficient block. The second transform is particularly effective in terms of energy compaction for predicted residual signal blocks within the screen, where strong energy is likely to exist in directions other than the horizontal or vertical directions of the residual signal block.

[0312] Referring to FIG. 27, a video signal processing device can parse syntax elements related to a residual signal included in a bitstream and restore quantization coefficients through inverse binarization based on the parsing result. The video signal processing device can obtain transform coefficients by performing inverse quantization on the restored quantization coefficients. The video signal processing device can restore a residual signal block by performing inverse transform on the transform coefficients. At this time, the inverse transform can be applied to a block to which transform skip (TS) is not applied. The video signal processing device can perform inverse transform in the order of a second inverse transform and a first inverse transform. At this time, the second inverse transform may be omitted. For example, if the current block is encoded in an inter prediction mode, the second inverse transform may be omitted. In addition, the second inverse transform may be omitted depending on the size of the current block. The restored residual signal includes a quantization error, and the second transform can reduce the quantization error compared to when only the first transform is performed by changing the energy distribution of the residual signal.

[0313] FIG. 28 is a diagram showing a region-of-interest (ROI) of a block to which a secondary transformation is applied according to one embodiment of the present invention.

[0314] According to one embodiment of the present specification, the numbers indicated in the sub-blocks in FIG. 28 may be sub-block indexes, and the sub-block indexes may be scanned in order from small numbers to large numbers.

[0315] Fig. 28(a) shows the ROI of LFNST4. The ROI of LFNST4 can be an ROI for a transform block of size 4 x N or N x 4. In this case, N can be an integer between 4 and 128. Referring to Fig. 28(a), the ROI of LFNST4 can be an ROI in a 16 x 4 block composed of 4 subblocks (subblocks 0 to 3). In this case, the ROI is one subblock of size 4 x 4, and referring to Fig. 28(a), the ROI corresponds to subblock 0. The number of input samples of the ROI can be 16. The forward transform matrix of LFNST4 can be R x 16. In this case, R can be 4, 8, 16, etc. For example, if R is 16, the number of transform coefficients generated after transformation can be 16.

[0316] Fig. 28(b) shows the ROI of LFNST8. The ROI of LFNST8 can be an ROI for a transform block of size 8 x N or N x 8. In this case, N can be an integer between 8 and 128. Referring to Fig. 28(b), the ROI of LFNST8 can be an ROI in a 16 x 8 block composed of 8 subblocks (subblocks 0 to 7). In this case, the ROI can be an area corresponding to 4 subblocks of size 4 x 4, and referring to Fig. 28(b), the ROI corresponds to subblocks 0, 1, 2, and 3. The number of input samples of the ROI can be 64. The forward transform matrix of LFNST8 can be R x 64. In this case, R can be 8, 16, 32, 64, etc. For example, if R is 32, the number of conversion coefficients generated after conversion can be 32.

[0317] Fig. 28(c) shows the ROI of LFNST16. The ROI of LFNST8 can be an ROI for a transform block of size 16 x N or N x 16. In this case, N can be an integer between 16 and 128. Referring to Fig. 28(c), the ROI of LFNST16 can be an ROI in a 16 x 16 block composed of 16 subblocks (subblocks 0 to 15). In this case, the ROI can be an area corresponding to six subblocks of size 4 x 4, and referring to Fig. 28(b), the ROI corresponds to subblocks 0, 1, 2, 3, 4, and 5. The number of input samples of the ROI can be 96. The forward transform matrix of LFNST16 can be R x 96. In this case, R can be 8, 16, 32, 64, 96, etc. For example, if R is 32, the number of conversion coefficients generated after conversion can be 32.

[0318] FIG. 29 is a diagram showing a method of applying a second-order transform (LFNST) according to one embodiment of the present invention.

[0319] The secondary transform can be expressed as the product of the matrix of the secondary transform kernel and the coefficient vector of the primary transform. In other words, it can be interpreted as mapping the primary transformed coefficients to another space. At this time, if the number of coefficients subjected to the secondary transform is reduced, that is, the number of basis vectors constituting the secondary transform kernel is reduced, the amount of computation required for the secondary transform and the memory capacity required to store the transform kernel can be reduced. For example, when a video signal processing device performs the secondary transform for an area corresponding to the upper left ROI of the transform block, if the number of coefficients subjected to the secondary transform is reduced to 32, a secondary transform kernel of size 32 x 96 can be applied, and an inverse secondary transform kernel of size 96x32 can be applied.

[0320] Referring to FIG. 29, the encoder can perform a forward primary transform on a residual signal block to obtain a primary transformed coefficient block. At this time, the residual signal may be a signal obtained by intra prediction. The size of the primary transformed coefficient block may be M x N. The encoder can perform a forward primary transform on a residual signal block where the value of min(M,N) is 16 to obtain a primary transformed coefficient block. Then, the encoder can perform a 32 x 96 secondary transform (LFNST) on samples of the upper left ROI area of ​​the primary transformed coefficient block. In addition, the encoder can perform a forward primary transform on a residual signal block where the value of min(M,N) is 8 to obtain a primary transformed coefficient block. And, the encoder can perform a secondary transformation on samples in the upper left ROI area of ​​the first transformed coefficient block.

[0321] Referring to FIG. 29, the transform coefficients of the entire transform block size including the secondary transform coefficients can be quantized, and information about the quantized transform coefficients can be included in the bitstream. In addition, the bitstream can include a syntax element (lfnst_idx) related to the secondary transform. Specifically, the bitstream can include information indicating whether the secondary transform is applied to the current block and the transform kernel.

[0322] Referring to FIG. 29, the decoder can parse quantized transform coefficients from a bitstream and obtain transform coefficients through de-quantization. The decoder can determine whether to perform an inverse secondary transform (Inverse LFNST) on the current transform block based on syntax elements related to the secondary transform. If the inverse secondary transform is applied to the current transform block, 16 or 32 transform coefficients can be input to the inverse secondary transform depending on the size of the transform block. The number of transform coefficients that become the input of the inverse secondary transform can be the same as the number of transform coefficients obtained by the encoder performing the secondary transform. The decoder can obtain the first-transformed coefficients through the product of the vectorized transform coefficients and the inverse secondary transform kernel matrix. The inverse secondary transform kernel can be determined based on the size of the transform block, the intra prediction mode, and the syntax elements indicating the transform kernel. The inverse secondary transform kernel matrix can be a transpose matrix of the secondary transform kernel matrix, and considering the complexity of the implementation, the elements of the kernel matrix can be integers expressed in 10-bit or 8-bit precision. The primary transform coefficients obtained through the inverse secondary transform are in the form of vectors, so they can be expressed as two-dimensional data. The primary transform coefficients can depend on the intra prediction mode. The mapping relationship based on the intra prediction mode applied by the encoder can be applied in the same manner. The decoder can obtain a residual signal by performing an inverse primary transform on a transform coefficient block of the entire transform block size including the transform coefficients obtained by performing the inverse secondary transform. The process described through Fig. 29 may include a scaling process using a bit shift operation.

[0323] FIG. 30 is a diagram showing a mapping relationship between an intra prediction mode and a set of transformation kernels for secondary transformation according to one embodiment of the present invention.

[0324] A set of transform kernels for LFNST applied to a transform block can be determined for each intra prediction mode of the transform block. One set of transform kernels can be composed of multiple LFNST kernels. For example, one set of transform kernels can be composed of three or four LFNST kernels. There can be 35 sets of transform kernels, and each set of transform kernels can be indexed with an index from 0 to 34. Intra prediction mode indices -14 to -1 and 67 to 80 corresponding to the extended angle mode can be mapped to the set of transform kernels with index 2.

[0325] FIG. 31 is a diagram showing the relationship between the input vector of the secondary transformation and the intra prediction mode according to one embodiment of the present invention.

[0326] The secondary transform can be calculated by multiplying the secondary transform kernel matrix by the input vector. The video signal processing device can organize the coefficients in the upper left sub-block of the first transformed coefficient block in the form of a vector. The vector can be organized depending on the intra prediction mode. For example, if the intra prediction mode is a prediction mode corresponding to an index less than or equal to index 34 of FIG. 6, or an INTRA_LT_CCLM, INTRA_T_CCLM, or INTRA_L_CCLM mode that predicts chroma samples using the linear relationship of chroma, the video signal processing device can organize the coefficients in the form of a vector by horizontally scanning the upper left sub-block of the first transformed coefficient block. The element of the i-th row and j-th column of the upper left nxn block of the first transformed coefficient block can be described as x_ij. At this time, the vectorized coefficients are [x_00, x_01, ..., x_0n-1, x_10, x_11, …]. , x_1n-1, ..., x_n-10, x_n-11, ..., x_n-1n-1]. On the other hand, if the intra prediction mode is a prediction mode corresponding to an index greater than index 34 of Fig. 6, the video signal processing device can vertically scan the upper left sub-block of the first transformed coefficient block to configure the coefficients in vector form. The vectorized coefficients can be expressed as [x_00, x_10, ..., x_n-10, x_01, x_11, ..., x_n-11, ..., x_0n-1, x_1n-1, ..., x_n-1n-1].

[0327] Since the secondary transformed coefficients are in vector form, they can be expressed as two-dimensional data. The secondary transformed coefficients can be assigned to the upper-left sub-block of the transform block according to a preset scanning order. The preset scanning order may be an up-right diagonal scanning order.

[0328] Figure 32 shows the application block and kernel size of NSPT (Non-Separable Primary Transform) according to one embodiment of the present invention.

[0329] NSPT is a method that transforms the transformation that previously applied DCT-II and LFNST separately to a block of a specific size in a single step. Similar to LFNST, NSPT is a non-separable transformation. For NSPT, 35 transformation sets based on intra prediction modes can be set, and each transformation set can be composed of three kernel candidates. The encoder can derive a transformation kernel set according to the intra prediction mode, and generate and signal a bitstream that includes an index indicating the optimal candidate among the three candidates in the derived transformation kernel set. The decoder can inversely transform the current transformation coefficients based on the optimal candidate determined by parsing the index, and obtain a residual block. Referring to Figure 32, NSPT WxH can mean a case where NSPT is applied to a block of size WxH. NSPT 4x4 has a 16x16 kernel size, NSPT 4x8 / NSPT 8x4 has a 32x20 kernel size, NSPT 4x16 / NSPT 16x4 has a 64x24 kernel size, NSPT 8x8 has a 64x32 kernel size, NSPT 8x16 / NSPT 16x8 has a 128x40 kernel size, NSPT 4x32 / NSPT 32x4 has a 128x20 kernel size, and NSPT 8x32 / NSPT 32x8 can have a 256x24 kernel size.

[0330] The coefficients of a 4x4 block to which NSPT is applied may not be zeroed out. 12 coefficients of a 4x8 or 8x4 block may be zeroed out, 32 coefficients of an 8x8 block may be zeroed out, 40 coefficients of a 4x16 or 16x4 block may be zeroed out, and 88 coefficients of an 8x16 or 16x8 block may be zeroed out. The number of coefficients that are zeroed out may vary depending on the size of the NSPT kernel. Zeroing out coefficients may mean that the values ​​of the coefficients are set to 0.

[0331] Fig. 33 illustrates an intra prediction mode derivation method for applying MTS / LFNST / NSPT according to one embodiment of the present invention.

[0332] At least one of MTS / LFNST / NSPT can be applied to a chroma block to which DBV is applied. Intra prediction mode information may be required for the transformation method of MTS / LFNST / NSPT to be applied. A video signal processing device can determine a transformation kernel set based on the intra prediction mode information, select (decide) a transformation kernel within the transformation kernel set, and perform transformation based on the selected kernel. At this time, the transformation kernel within the transformation kernel set can be indicated by information (syntax element) within the bitstream. The following describes a method for determining the intra prediction mode of a chroma block to which DBV is applied.

[0333] i) The intra prediction mode of the chroma block may be a preset intra prediction mode. For example, the preset intra prediction mode may be a planar mode or a DC mode.

[0334] ii) The intra prediction mode of the chroma block may be an intra prediction mode set in a reference block indicated by a block vector at a specific position of a luma block corresponding to the chroma block. At this time, the intra prediction mode of the chroma block may be an intra prediction mode stored at a specific position of the reference block. For example, the luma block corresponding to the chroma A block of FIG. 33(b) may be the luma A block of FIG. 33(a). The reference block indicated by the block vector at the TL position of the luma A block may be the block of FIG. 33(c). At this time, the intra prediction mode of the chroma block may be an intra prediction mode stored at one of {TL, TR, C, BL, BR, 1, 2, 3, 4} of the preset positions of the reference block. The search order in which the video signal searches for the preset positions may be TL-TR-C-BL-BR-1-2-3-4. In Fig. 33, the block vector of the TL position of the luma A block is used, but the present invention is not limited thereto, and a block vector determined based on a cost among the block vector list may be used. Alternatively, the block vector of the position where the block vector is first stored among C-TR-TL-BL-BR of the luma A block may be used. Alternatively, the block vector of the position to which the basic position and the basic position-based distance offset are applied among C-TR-TL-BL-BR of the luma A block may be used. The video signal processing device may determine and apply a set of MTS / LFNST / NSPT kernels based on the intra prediction mode of the chroma block.

[0335] iii) The intra prediction mode of the chroma block can be determined based on intra prediction mode information of a preset position of a luma block corresponding to the chroma block. The preset position may be a position for searching a block vector within the luma block. An intra prediction mode may not exist in a position where a block vector is stored, and if the block vector is not stored, an intra prediction mode may be stored. For example, referring to FIG. 33(a), the preset positions may be C, TL, TR, BL, and BR of FIG. 33(a). The video signal processing device may perform a search for only one of the preset positions, and if there is no intra prediction mode in the searched position, the default intra prediction mode may be used. The default intra prediction mode may be a planar mode or a DC mode. Alternatively, the video signal processing device may search for a plurality of positions among the preset positions and use the intra prediction mode of the first searched position. Meanwhile, if the video signal processing device searches multiple locations and no intra prediction mode exists, the default intra prediction mode can be used.

[0336] Figure 34 illustrates syntax elements related to DBV according to one embodiment of the present invention.

[0337] Figure 34 illustrates syntax elements related to DBV included in the SPS RBSP syntax. sps_chroma_format_idc may be a syntax element indicating the relationship between chroma sampling and luma sampling. The relationship between chroma sampling and luma sampling may be as shown in Table 4. If the value of sps_chroma_format_idc is 0, it may indicate that the current block only has a luma component without a chroma component.

[0338]

[0339] sps_ibc_enabled_flag can indicate whether IBC mode is enabled at the sequence level. A value of sps_ibc_enabled_flag of 1 indicates that IBC mode is enabled, while a value of 0 indicates that IBC mode is not enabled. If sps_ibc_enabled_flag is not present in the syntax, the value of sps_ibc_enabled_flag is inferred to be 0. (sps_ibc_enabled_flag equal to 1 specifies that the IBC prediction mode is enabled for the CLVS. sps_ibc_enabled_flag equal to 0 specifies that the IBC prediction mode is disabled for the CLVS. When sps_ibc_enabled_flag is not present, it is inferred to be equal to 0.)

[0340] sps_intra_tmp_enabled_flag can indicate whether Intra TMP is enabled or not at the sequence level. If the value of sps_intra_tmp_enabled_flag is 1, it indicates that Intra TMP is enabled, and if the value of sps_intra_tmp_enabled_flag is 0, it indicates that Intra TMP is not enabled. If sps_intra_tmp_enabled_flag does not exist in the syntax, the value of sps_intra_tmp_enabled_flag can be inferred to be 0. ( sps_intra_tmp_enabled_flag equal to 1 specifies that the Intra TMP prediction mode is enabled for the CLVS. sps_intra_tmp_enabled_flag equal to 0 specifies that the Intra TMP prediction mode is disabled for the CLVS. When sps_intra_tmp_enabled_flag is not present, it is inferred to be equal to 0.)

[0341] sps_dbv_chroma_enabled_flag can indicate whether DBV of a chroma block is enabled at the sequence level. If the value of sps_dbv_chroma_enabled_flag is 1, it can indicate that DBV of a chroma block is enabled, and if the value of sps_dbv_chroma_enabled_flag is 0, it can indicate that DBV of a chroma block is not enabled. If sps_dbv_chroma_enabled_flag does not exist in the syntax, the value of sps_dbv_chroma_enabled_flag can be inferred to be 0. (sps_dbv_chroma_enabled_flag equal to 1 specifies that the Direct Block Vector for Chroma prediction mode is enabled for the CLVS. sps_dbv_chroma_enabled_flag equal to 0 specifies that the Direct Block Vector for Chroma prediction mode is disabled for the CLVS. When sps_dbv_chroma_enabled_flag is not present, it is inferred to be equal to 0.)

[0342] sps_dbv_chroma_enabled_flag can be signaled / parsed (3401) if i) sps_chroma_format_idc value is not equal to 0, and ii) sps_ibc_enabled_flag value is true (equal to 1) or sps_intra_tmp_enabled_flag value is true (equal to 1). In order for DBV to be applied to a chroma block, a block vector must exist in the luma block corresponding to the chroma block. Therefore, IBC mode or Intra TMP must be enabled, and the current block must also contain a chroma component.

[0343] There may be a syntax element for each of the CCCM-related modes (e.g., CCCM / MM-CCCM / CCLM / GLM / GL-CCCM / CCCM-ND / CCCM-MDF). That is, a flag (syntax element) for each of the CCCM-related modes in the SPS RBSP syntax may be defined, or whether the CCCM-related mode is enabled or disabled may be indicated based on each flag. At this time, in order for the flag for each of the CCCM-related modes to be signaled (parsed), the value of sps_chroma_format_idc may not be 0. In addition, a flag for whether the SPS level is enabled or disabled for the CCP merge mode may be defined, and in order for the flag for the CCP merge mode to be signaled (parsed), the value of any one of the flags for each of the CCCM-related modes may have to be 1 (true) or the value of sps_cclm_enabled_flag may have to be 1 (true).

[0344] Figure 35 illustrates the operation of BVG-CCCM (Block Vector Guided CCCM) according to one embodiment of the present invention.

[0345] The current chroma block can be predicted using the CCCM method (see Fig. 16). At this time, if the corresponding luma block is coded in Intra TMP or IBC mode, the video signal processing device can obtain adjacent surrounding luma samples of a reference luma block indicated by a block vector of a luma block (co-located luma block) corresponding to the current chroma block, and the video signal processing device can obtain adjacent surrounding chroma samples of the reference chroma block indicated by the block vector of the current chroma block. The video signal processing device can derive CCCM parameters based on the obtained surrounding luma samples and luma chroma samples. The video signal processing device can perform chroma prediction using the luma sample corresponding to the current chroma block as an input value based on the derived CCCM parameters. BVG-CCCM can be applied when i) the chroma prediction mode index indicates LM_CHROMA_IDX or MMLM_CHROMA_IDX, ii) the luma block corresponding to the chroma block is coded in Intra TMP or IBC mode, iii) the partitioning methods of the luma and chroma blocks are different, iv) BVG-CCCM is enabled, the CCLM mode is enabled, and the CCCM mode is enabled, and v) a single model for CCCM or a multi-model is applicable. Whether BVG-CCCM in iv) is enabled can be indicated by the higher-level syntax (SPS level syntax) sps_bvg_cccm_enabled_flag, whether the CCLM mode is enabled can be indicated by the higher-level syntax sps_cclm_enabled_flag, and whether the CCCM mode is enabled can be indicated by the higher-level syntax sps_cccm_enabled_flag.ii) LM_CHROMA_IDX may be an index indicating whether a single model of CCLM is applied, and MMLM_CHROMA_IDX may be an index indicating whether a multi-model of CCLM is applied.

[0346] MTS, NSPT, or LFNST can also be applied to chroma blocks predicted using BVG-CCCM. Kernel sets for NSPT and LFNST can be defined based on intra prediction modes and block sizes, and a video signal processing device can perform transformation using specific kernels within the kernel set. The intra prediction mode for determining the transformation kernel can be determined using the method described above in FIG. 33.

[0347] Figure 36 illustrates syntax elements related to BVC-CCCM according to one embodiment of the present invention.

[0348] Figure 36 shows syntax elements related to BVC-CCCM included within the SPS RBSP syntax.

[0349] sps_bvg_cccm_enabled_flag can indicate whether BVG-CCCM is enabled. If the value of sps_bvg_cccm_enabled_flag is 1, it indicates that BVG-CCCM is enabled, and if the value of sps_bvg_cccm_enabled_flag is 0, it indicates that BVG-CCCM is not enabled. If sps_bvg_cccm_enabled_flag does not exist in the syntax, the value of sps_bvg_cccm_enabled_flag can be inferred to be 0. (sps_bvg_cccm_enabled_flag equal to 1 specifies that the Block Vector Guided CCCM prediction mode is enabled for the CLVS. sps_bvg_cccm_enabled_flag equal to 0 specifies that the Block Vector Guided CCCM prediction mode is disabled for the CLVS. When sps_bvg_cccm_enabled_flag is not present, it is inferred to be equal to 0.)

[0350] The conditions for sps_bvg_cccm_enabled_flag to be signaled (parsed) are as follows:

[0351] When i) the value of sps_chroma_format_idc is not 0, ii) the value of sps_cclm_enabled_flag is 1, and iii) the value of sps_ibc_enabled_flag is 1 or the value of sps_intra_tmp_enabled_flag is 1, sps_bvg_cccm_enabled_flag can be signaled (3601).

[0352] In addition, the conditions described below may be added to the above-described 3601 conditions. For example, a condition in which the value of sps_cccm_enabled_flag is 1 may be added. Or, a condition in which the value of the non-inter tool control enabled flag is 1 may be added. The non-inter tool control enabled flag may be a flag that controls on a per-tool basis.

[0353] FIG. 37 illustrates a method for determining a reference pixel line based on a template according to one embodiment of the present invention.

[0354] Below, we describe a method for determining the optimal reference pixel line for the current block (for restoration of the current block) based on the template.

[0355] Referring to FIG. 37, a video signal processing device can construct a reference template using reference pixel lines adjacent to a current block. The video signal processing device can generate prediction samples for the positions of the reference templates using reference pixel lines 1, 2, 3, etc. The video signal processing device can calculate a cost between the generated prediction samples and samples of the reference template. At this time, the cost can be calculated using a method such as SAD (Sum of Absolute Differences) or MRSAD (Mean-Removed SAD). The reference pixel corresponding to the minimum cost may be the optimal reference pixel. In addition, the encoder can rearrange the calculated costs in ascending order, construct a list for reference pixel lines, and then generate and signal a bitstream including information on an index for the optimal reference pixel line. The decoder can construct a list for reference pixel lines using the above-described method, parse the index for the optimal reference pixel line included in the bitstream, and generate a prediction sample using the reference pixel line indicated by the index. As described herein, a method for a video signal processing device to determine a reference pixel line based on a template can be described as a Template-based Multiple Reference Line (TMRL) method or a TMRL intra prediction method.

[0356] In order to reduce the complexity of determining the optimal reference pixel line, the optimal reference pixel line may not be used for all intra prediction modes, but may be used only for the intra prediction modes included in the MPM list. That is, the encoder can construct a list of reference pixel lines by combining intra prediction modes included in the MPM list with multiple reference pixel lines, and calculate the cost between the prediction sample generated using each candidate in the list for the reference pixel line and the reference template. Then, the encoder can reconstruct the list in ascending order based on the cost and use only a few combinations with low costs. The encoder can generate and signal a bitstream that includes information about an index for the optimal combination information among the combination information (any intra prediction mode and any reference pixel lines) in the reconstructed list. The decoder can construct a list for the same reference pixel lines using the above-described method, parse the index for the optimal combination information included in the bitstream, and generate a prediction sample using the optimal combination information indicated by the index.

[0357] When prediction samples are generated using multiple reference pixel lines, different weights may be applied to each prediction sample generated through each reference pixel line. At this time, a template-based method may be used to derive optimal weights. That is, the encoder may construct a list for reference pixel lines by combining intra prediction modes included in the MPM list, multiple reference pixel lines, and weights (for example, one of 3:1 and 2:2) for samples predicted by each reference pixel line, and may calculate the cost between the prediction sample generated using each candidate in the list for the reference pixel line and the reference template. Then, the video signal processing device may rearrange the MPM list in ascending order based on the cost, and then reconstruct the MPM list using only a few combinations with low costs. The encoder can generate and signal a bitstream including information about an index for optimal combination information among combination information within the reconstructed list (any intra prediction mode, any reference pixel lines, and weights (e.g., one of 3:1 and 2:2) for samples predicted by each reference pixel line). The decoder can construct a list for the same reference pixel lines using the above-described method, and then parse the index for optimal combination information included in the bitstream to generate a prediction sample using the optimal combination information indicated by the index.

[0358] In the method for determining a reference pixel line based on a template described through Fig. 37, reference pixel lines adjacent to the current block can be used to construct the template. Accordingly, reference pixel lines determined based on the template can be determined using reference pixel lines not adjacent to the current block.

[0359] Fig. 38 shows a block vector related to an IBC encoding method according to one embodiment of the present invention.

[0360] The IBC coding method (IBC mode) is a method of finding the part (reference block) that is most similar to the current block in an already reconstructed area within the current picture and using the reference block as a prediction block for the current block. At this time, the encoder can generate a bitstream that includes information related to a block vector, which is the distance between the current block and the reference block. The decoder can parse information related to the block vector included in the BeastStream to calculate or set the block vector for the current block. The IBC coding method can be applied to chrominance blocks. In the chrominance block, the block vector of the luminance block corresponding to the chrominance block can be used as the block vector of the chrominance block without finding a new block vector, and this coding method can be called DBV (Direct Block Vector) mode.

[0361] The RRIBC (Reconstruction-Reordered IBC) encoding mode can be used in IBC blocks (blocks to which the IBC encoding method is applied). RRIBC can be composed of vertical flips and horizontal flips. The reconstructed block of a block to which RRIBC is applied is flipped according to the RRIBC type of the current block. The encoder can flip the original block to be encoded before finding the most similar part to the current block from the reference picture. That is, the most similar part from the reference picture is found using the flipped original block. Therefore, the prediction block uses a block that has not been flipped, and the residual block can also be a block that has not been flipped. The decoder can flip the final reconstructed block according to the RRIBC type of the current block.

[0362] FIG. 39 illustrates a method for predicting a current block using RRIBC in a horizontal direction according to one embodiment of the present invention.

[0363] FIG. 40 illustrates a method for predicting a current block using RRIBC in the vertical direction according to one embodiment of the present invention.

[0364] In Figures 39 and 40, (Xn, Yn) represents the central position of the surrounding blocks, and (Xc, Yc) represents the central position of the current block. BV n h , BV n v represents the horizontal block vector and vertical block vector of the surrounding blocks, respectively, and BV C h , BV C v represent the horizontal block vector and the vertical block vector of the current block, respectively. As shown in Fig. 39, if the RRIBC type of the current block is horizontal, BV C h is 2 * (Xn - Xc) + BV n h It can be calculated as, and as in Fig. 40, if the RRIBC type of the current block is in the vertical direction, BV C v is 2 * (yn - yc) + BV n v can be calculated as . At this time, BV n h , BV n v Since it uses restored blocks, BV n h , BV n v The sign of can only be negative.

[0365] When the current block is encoded with RRIBC, the video signal processing device can determine an optimal block vector by constructing a block vector candidate list. At this time, the video signal processing device can construct the block vector candidate list according to the RRIBC type of the current block. For example, when the RRIBC type of the current block is horizontal, the video signal processing device can construct the block vector candidate list using only the neighboring blocks of the current block encoded with RRIBC in the horizontal direction. In addition, the video signal processing device can construct the block vector candidate list regardless of the RRIBC type of the current block. For example, when the RRIBC type of the current block is horizontal, the block vector candidate list can be constructed using not only the neighboring blocks of the current block encoded with RRIBC in the horizontal direction, but also the neighboring blocks of the current block encoded with RRIBC in the vertical direction, and / or blocks encoded with general motion, and / or blocks encoded with block vectors.

[0366] When a video signal processing device predicts a current block using general motion, the video signal processing device can construct a motion candidate list depending on whether the neighboring blocks of the current block are encoded in the IBC mode or the RRIBC mode. At this time, if the neighboring blocks of the current block are encoded in the RRIBC mode, the video signal processing device can construct the motion candidate list by additionally considering the RRIBC type. For example, when the video signal processing device constructs a motion candidate list for the current block, if the encoding mode of the neighboring blocks of the current block is the RRIBC mode and the RRIBC type is the vertical direction or the horizontal direction, the block vector of the neighboring blocks may not be included in the motion candidate list. Alternatively, when the video signal processing device predicts the current block using general motion, the video signal processing device can construct a motion candidate list regardless of the encoding mode of the neighboring blocks of the current block. In other words, the video signal processing device can construct a motion candidate list regardless of whether the neighboring blocks of the current block are encoded in the IBC mode or the RRIBC mode. For example, when a video signal processing device constructs a motion candidate list for a current block, the video signal processing device may include block vectors of the surrounding blocks in the motion candidate list even if the encoding mode of the surrounding blocks of the current block is the IBC mode and the RRIBC type is the vertical direction or the horizontal direction.

[0367] The RRIBC encoding method is effective for images with symmetrical characteristics. Symmetry can mean perfect horizontal (or vertical) symmetry with equal distances between the current block and the reference block around a central axis. The vertical (or horizontal) direction (symmetry axis) of the current block can be colinear with the vertical (or horizontal) direction (symmetry axis) of the reference block. In this case, the block vector in the vertical (or horizontal) direction can be set to '0', and the block vector in the horizontal direction can be set to any negative value other than '0'. The current block and the reference block can be configured to be symmetric with different distances apart from one central axis between the current block and the reference block, and the current block and the reference block can be located on different vertical lines. In this case, the block vector in the vertical direction can be set to any negative value other than '0'. That is, the video signal processing device can encode or decode the current block using a symmetric block having a block vector value of an arbitrary negative value other than '0' in both the horizontal and vertical directions.

[0368] Fig. 41 shows a block vector of a block encoded in Intra TMP mode according to one embodiment of the present invention.

[0369] Referring to FIG. 41, the Intra TMP method (Intra TMP encoding mode) is a method in which a video signal processing device constructs a reference template using pixel values ​​of neighboring blocks adjacent to a current block, then finds the most similar part to the reference template in an already reconstructed area (reference block) within the current picture, and then uses the reference block (Ref. luma block of FIG. 41) as a prediction block for the current block. At this time, there may be more than one block vector used to generate a prediction block for the current luminance block, and FIG. 41 shows a case in which there are two block vectors. The video signal processing device can generate a prediction block for the luminance block by weighting and averaging the reference blocks predicted from the two block vectors of the current luminance block. In the case of a chrominance block, the video signal processing device can derive a block vector from a luminance block corresponding to the chrominance block, and then generate a chrominance prediction block using the block vector. There may be more than one block vector used to generate a prediction block for the current chrominance block, and Fig. 41 shows a case where there are two block vectors for the chrominance block. In this case, the block vector of the chrominance block may be the same as or different from the block vector derived from the luminance block.

[0370] Figure 42 illustrates a case where a current block is divided by GPM mode according to one embodiment of the present invention and the divided area is encoded in IBC mode.

[0371] The current block can be encoded or decoded in IBC-GPM mode. IBC-GPM mode may mean a mode in which the current block is divided using GPM mode, and the divided region is encoded in intra prediction mode or IBC prediction mode. Referring to Fig. 42, the current block can be divided into two regions based on a dotted line. At this time, one of the divided regions can be encoded in intra prediction mode, and the other can be encoded in IBC prediction mode. For example, the left region among the divided regions can be encoded in intra prediction mode, and the right region can be encoded in IBC prediction mode. At this time, the region encoded in IBC prediction mode can be encoded in Intra TMP prediction mode, and this can be described as IntraTMP-GPM mode.

[0372] Figure 43 illustrates how a current block is encoded in IBC-CIIP mode according to one embodiment of the present invention.

[0373] A video signal processing device can predict the current block using a weighted average between a block predicted in Intra mode and a block predicted in IBC mode, which can be referred to as IBC-CIIP mode. In this case, a block predicted in Intra TMP mode can be used instead of a block predicted in IBC mode, which can be referred to as Intra TMP-CIIP mode.

[0374] A video signal processing device can obtain a reconstructed luminance block by adding a residual signal for a luminance prediction block of a current block and a luminance block, and can configure a CCP model by using a correlation between the reconstructed luminance block and the luminance prediction block. At this time, the CCP model can be one of CCLM, MMLM, GLM, CCCM, MM-CCCM, GL-CCCM, CCCM-ND, and CCCM-MDF. The CCP model derived from the luminance block can be applied to a chrominance prediction block to generate a first chrominance prediction block to which the CCP model is applied. A final chrominance block can be generated by adding an error signal for the first chrominance prediction block and the chrominance block.

[0375] FIG. 44 illustrates a method for deriving a multi-transform set and a LFNST / NSPT set according to one embodiment of the present invention.

[0376] Referring to Fig. 44(a), the encoder can select which one of MTS, DCT2 + LFNST, and NSPT to apply to the residual block, and can transform the residual block and obtain transform coefficients based on the selected transform method. At this time, the encoder can signal information on which transform method was applied by including it in the bitstream. If the MTS transform is applied to the residual block, the transform coefficients of the residual block can be obtained by applying the MTS transform, and LFNST and NSPT transforms may not be applied. If the DCT2 + LFNST transform is applied to the residual block, the encoder can apply the DCT2 transform to the residual block to obtain the first transform coefficients, and apply the LFNST transform to the first transform coefficients to obtain the second transform coefficients. At this time, the MTS and NSPT transforms may not be applied. When the NSPT transform is applied to the residual block, the video encoder can output transform coefficients by applying the NSPT transform to the residual block, and at this time, the MTS and DCT2 + LFNST transforms may not be applied to the residual block.

[0377] Referring to Fig. 44(b), the decoder can parse information on which transform method was applied from the bitstream, and determine whether to apply one of the inverse transform methods among MTS, DCT2 + LFNST, and NSPT to the current transform coefficient based on the parsed information. Then, the decoder can perform an inverse transform on the transform coefficient based on the determined transform method and obtain a residual block. If the MTS transform is applied to the current transform coefficient, the decoder can perform an inverse MTS transform on the transform coefficient to obtain a residual block, and at this time, the LFNST and NSPT inverse transforms may not be applied. If the DCT2 + LFNST transform is applied to the secondary transform coefficient, the decoder can perform an inverse LFNST transform on the secondary transform coefficient to output a primary transform coefficient, and perform an inverse DCT2 transform on the primary transform coefficient to obtain a residual block, and at this time, the MTS and NSPT transforms may not be applied. If the NSPT transform is applied to the current transform coefficients, the decoder can obtain a residual block by performing the NSPT inverse transform on the current transform coefficients, and at this time, the MTS and DCT2 + LFNST transforms may not be applied.

[0378] A video signal processing device can derive a transform kernel for each of MTS, LFNST, and NSPT transforms (or inverse transforms) using an intra prediction mode. In addition, the video signal processing device can determine which transform (or inverse transform) is applied among MTS, DCT2 + LFNST, and NSPT. At this time, in order to determine the transform, at least one or more of the horizontal and vertical sizes of the current block, whether the components of the current block are luminance components or chrominance components, whether the current block is a single tree or a dual tree, information on whether the current block is encoded in intra mode or inter mode, information on the encoding mode of the current block (e.g., IBC, Intra TMP, Merge, AMVP, GPM, SGPM, CCLM, CCCM), and information on the quantization parameters of the current block may be used.

[0379] Figure 45 shows a mapping table according to one embodiment of the present invention.

[0380] Figure 46 illustrates a conversion type set table according to one embodiment of the present invention.

[0381] Figure 47 shows a conversion type combination table according to one embodiment of the present invention.

[0382] Figure 48 shows a threshold value table for an IDT conversion type according to one embodiment of the present invention.

[0383] A method for selecting a set of multiple transforms available for a current block in a video signal processing device is described when a prediction block of a current block is generated using a vertical planar mode, a horizontal planar mode, or a conventional planar mode.

[0384] 1) First, the video signal processing device can derive the nSzIdxW and nSzIdxH values ​​based on the size of the current block to map the horizontal and vertical sizes of the current block into a single variable. nSzIdxW can be the minimum value among the logarithm of 2 calculated for the width of the current block, the difference of 2 with the decimal places discarded, and the three. nSzIdxH can be the minimum value among the logarithm of 2 calculated for the height of the current block, the difference of 2 with the decimal places discarded, and the three.

[0385] 2) Next, the video signal processing device can derive the intra-directional mode (predMode) of the current block. In the case of TIMD mode, the number of intra-prediction modes expanded from the existing 67 to 131 can be used, reducing the precision of the existing 67 modes.

[0386] 3) Next, the video signal processing device can derive the ucMode, nMdIdx, and isTrTransposed values.

[0387] A. If the current block is encoded in MIP mode, ucMode can be set to '0', nMdIdx can be set to '35', and isTrTransposed can be set to a value derived from MIP.

[0388] B. If the current block is not encoded in MIP mode, ucMode may be set to the intra directional mode (predMode) of the current block. predMode may mean an index value of the intra directional mode. predMode may be determined through an extended angle mode according to the aspect ratio of the current block. The video signal processing device may clip predMode to a value between 2 and 66. If the prediction block of the current block is generated using the vertical plane mode, the video signal processing device may reset predMode to the horizontal prediction mode (angle mode 18 in FIG. 6). If the prediction block of the current block is generated using the horizontal plane mode, the video signal processing device may reset predMode to the vertical prediction mode (angle mode 50 in FIG. 6). When predMode is greater than the 34th angular mode, which is a diagonal mode, the isTrTransposed value can be set to 1, and when predMode is equal to or less than 34, the isTrTransposed value can be set to 0. When predMode is greater than 34, the video signal processing device resets the value of predMode to a value that is a difference of 67 (the maximum value of the intra directional mode index) plus 1. For example, when predMode is 35, the video signal processing device can reset the 35th angular mode to the 33rd angular mode (67+1-35(predMode)). When predMode is 66, the video signal processing device can reset the 66th angular mode to the 2nd angular mode (67+1-66(predMode)). That is, by making it symmetrical with respect to the 34th angular mode, which is a diagonal mode, the size of the transformation mapping table of FIG. 45 is reduced by about half.

[0389] 4) The video signal processing device can derive the nSzIdx value through nSzIdxW, nSzIdxH, and isTrTransposed values. If the isTrTransposed value is '1', the value obtained by multiplying nSzIdxH by 4 and then adding nSzIdxW can be set to nSzIdx. If the isTrTransposed value is '0', the value obtained by multiplying nSzIdxW by 4 and then adding nSzIdxH can be set to nSzIdx.

[0390] 5) The video signal processing device can derive nTrSet, which is an index of an available transformation type set, according to the predefined table of FIG. 45 using nSzIdx, which is the size information of the current block, and nMdIdx, which is the intra-directional mode information of the current block. FIG. 45 defines an index of a transformation type set according to the intra-screen directional mode (0 to 34 and MIP) of the current block and the size index (0 to 15) of the current block. Referring to FIG. 45, nTrSet can be 80, and if the size of the current block is 4x8 and the intra-screen directional mode of the current block is 13, nTrSet can be '7'.

[0391] 6) The video signal processing device can derive a set of transformation types corresponding to nTrSet from the table of FIG. 46 by parsing mts_idx included in the bitstream. The transformation types in the vertical and horizontal directions are set differently depending on whether predMode is a value greater than the 34th angle mode, which is a diagonal mode. 0 to 79 in the gray-shaded vertical columns of FIG. 46 may correspond to nTrSet, and 0 to 3 in the gray-shaded horizontal columns may correspond to mts_idx. Referring to FIG. 46, if nTrSet is 7 and the value of mts_idx is 3, 22 may be selected from (2, 17, 18, 22). In addition, DST1 and DCT5 corresponding to index 22 of the transformation type combination table of FIG. 47 are selected, and the vertical transformation type of the current block may be set to DST1 and the horizontal transformation type may be set to DCT5. The gray-shaded horizontal rows 0 to 24 in Fig. 47 represent indices selected through Fig. 46, and the gray-shaded vertical rows 0 to 1 may represent vertical and horizontal transformation types, respectively. If the predicted directionality mode within the screen of the current block is greater than 34, which is a diagonal mode, the vertical and horizontal transformation types may be interchanged.

[0392] If the mts_idx value is '3' and the width and height of the current block are both 16 or less, the vertical or horizontal transformation type can be reset to the IDT transformation type through the process described below.

[0393] If the absolute difference between the index of the predicted directionality mode within the screen of the current block and the index of the horizontal direction mode, 18, is less than a predetermined value, the vertical transformation type may be reset to the IDT transformation type. If the absolute difference between the index of the predicted directionality mode within the screen of the current block and the index of the horizontal direction mode, 50, is less than a predetermined value, the horizontal transformation type may be reset to the IDT transformation type. In this case, the predetermined value may be an integer and may be determined based on the horizontal or vertical size of the current block. For example, the predetermined value may be determined through the table of Fig. 45. The table of Fig. 48(a) represents a case where the threshold value is set differently whenever the horizontal or vertical size differs by 4, and the table of Fig. 48(b) represents a case where the threshold value is set differently whenever the horizontal or vertical size differs by 2 times. If the size of the current block is 16x16, the vertical transformation type may not be reset to the IDT transformation type, but the existing transformation type may be maintained as is.

[0394] To reduce the bit count for encoding mts_idx, the number of transform type sets can be adaptively changed for each block. The number of transform type sets can be adaptively determined based on the sum of the absolute values ​​of the transform coefficients of the current transform block. For example, the number of transform type sets can be adaptively determined to be 1, 4, or 6. When the number of transform type sets is different, the maximum number of bins for signaling mts_idx may be different. If the sum of the absolute values ​​of the transform coefficients is less than or equal to 6, the number of transform type sets may be one. Therefore, if the sum of the absolute values ​​of the transform coefficients is less than or equal to 6, the encoder may not include (i.e., may not signal) mts_idx in the bitstream, and the decoder may not parse mts_idx. If the sum of the absolute values ​​of the transform coefficients is greater than 6 and less than or equal to 32, the number of transform type sets may be four, and if the sum of the absolute values ​​of the transform coefficients is greater than 32, the number of transform type sets may be six. Transform Kernel In this case, when the number of transform type sets is multiple (e.g., 4 or 6), the encoder may generate and signal a bitstream including mts_idx based on the maximum number of transform type sets, The decoder can parse mts_idx based on the maximum number of transformation type sets, where the transformation type sets can be used in the same sense as transformation kernel candidates.

[0395] If the current block is encoded in inter mode, the transform kernel set for the current block can be any one of four combinations of transform kernel sets. The four combinations can be {(DST7, DST7), (DST7, DCT8), (DCT8, DST7), (DCT8, DCT8)}. The encoder can signal an index indicating the transform kernel set used among the four combinations by including it in the bitstream. The decoder can parse the index to determine the transform kernel set for the current block. For example, if the determined transform kernel set is (DST7, DCT8), DST7 can be applied to the current block in the horizontal direction and DCT8 can be applied to the vertical direction to perform transform / inverse transform. In addition, for complexity optimization, for images larger than 1920x1080 resolution, the maximum CU size to which inter MTS can be applied can be set to 32x32. For resolutions other than 1920x1080, the maximum CU size for which inter-MTS can be applied can be 16x16. Therefore, if the current block size is larger than 32x32 or 16x16, inter-MTS may not be applied to the current block, and DCT2 transform may be applied in the horizontal and vertical directions. In addition, the transform kernels DST7 and DCT8 for the current block size equal to or smaller than 16x16 may be replaced with a separable KLT (Karhunen-Loeve Transform).

[0396] Figure 49 shows block boundaries and samples around the boundaries in a deblocking filtering process according to one embodiment of the present invention.

[0397] Referring to Figure 49(a), the part indicated by the dotted line between the P block and the Q block may denote a block boundary. The block boundary may exist at any fixed size, and a block boundary may exist at every size of 4.

[0398] Figure 49(b) shows samples for which filtering is performed based on block boundaries. The video signal processing device may perform a process of alleviating blocking artifacts occurring at block boundaries by performing deblocking filtering on the currently restored block. The deblocking filtering process may include a process of determining a transform block boundary, determining a sub-block boundary, determining a length of a filter to perform filtering, determining a filtering strength (bS), determining a filtering parameter, determining whether to perform filtering, and determining a filtering type.

[0399] FIG. 50 shows generating a prediction block by applying a filter model to IBC block prediction according to an embodiment of the present invention.

[0400] In IBC, a video signal processing device can use a reference block corresponding to a block vector as a prediction block. At this time, the video signal processing device can apply the filter model described through FIG. 50 to the reference block to generate a prediction block. Specifically, the video signal processing device can derive a filter model using the relationship between the sample of the template of the reference block and the sample of the template of the current block. The video signal processing device can apply the derived filter model to the sample of the reference block to generate a prediction sample of the current block. The video signal processing device can derive a filter model for each component (Y, Cb, Cr) of the IBC block and apply the filter model for each component. In another specific embodiment, the video signal processing device can apply the filter model only to the luma component. The video signal processing device can obtain a filter model using the luma component and apply the obtained filter model to all components. In another specific embodiment, the filter model can be derived only from one of the luma and chroma components and applied only to the corresponding component.

[0401] The prediction mode of a prediction block to which IBC is applied may be set to MODE_IBC. When IBC is applied to a prediction block, the bitstream may include a flag indicating whether the filter model described above is applied to the prediction block. For convenience of explanation, the flag is referred to as IBCFilterFlag. The number of IBCFilterFlags per prediction block may vary depending on the filter model application method. The bitstream may include IBCFilterFlags indicating whether a filter model is applied to all components for one prediction block. In another specific embodiment, the bitstream may include multiple IBCFilterFlags indicating whether a filtering model is indicated for each component for one prediction block. In this case, the IBCFilterFlags may be parsed for each component. In addition, the bitstream may include IBCFilterFlags for each of Y, Cb, and Cr. In another specific embodiment, the bitstream may include a flag indicating whether a filter model is applied to a luma component of a prediction block and a flag indicating whether a filter model is applied to a chroma component of the prediction block. In this case, the video signal processing device may parse each of the IBCFilterFlag for the luma component of the prediction block and the IBCFilterFlag for the chroma component of the prediction block.

[0402] Additionally, the bitstream may not include the IBCFilterFlag for blocks to which IBCCIIP or IBCGPM is applied. In this case, the video signal processing device may infer the value of the IBCFilterFlag for blocks to which IBCCIIP or IBCGPM is applied as a predefined value. In this case, the predefined value indicates that the filter model is not applied. In addition, the predefined value may be 0.

[0403] In another specific embodiment, a video signal processing device may predict an intra prediction block used in CIIP in IBCCIIP prediction using an IBC filter model. The video signal processing device may predict an intra prediction block used in IBCGPM prediction using an IBC filter model. If IBCFilterFlag indicates that a filter model is used for a prediction block, the bitstream may not include a flag indicating whether LIC is applied to the prediction block. For convenience of explanation, the flag is referred to as IbcLicFlag. If IBCFilterFlag indicates that a filter model is used for a prediction block, the video signal processing device may infer a value of IbcLicFlag as a predetermined value. In this case, the predetermined value may indicate that LIC is not applied to the prediction block. In addition, the predetermined value may be 0.

[0404] In another specific embodiment, when IBC is used to predict a prediction block, a filter model may always be applied to predict the prediction block.

[0405] Even for general inter prediction blocks, a filter model can be applied and an indicator indicating whether or not it is applied can be signaled / parsed.

[0406] FIGS. 51 to 54 are diagrams illustrating a method for generating a prediction block according to one embodiment of the present invention.

[0407] Figure 51 illustrates a method for applying changes to and using prediction weight values ​​and offset values ​​when the current block is predicted using bidirectional prediction. The template of Figure 51 may have the same form as the template for CCCM described in Figure 50. As described in Figure 52, the template form may include an L-shaped template, an upper template, and a left template. For convenience of explanation, the following description will be based on the L-shaped template.

[0408] When the BCW method is applied and the final prediction sample is generated using different predictors in the inter prediction mode, the video signal processing device can derive the final prediction value through a weighted average of the samples of the second reference block and the samples of the third reference block. The BCW value (weight value) can be used as follows: {1, 2, 3, 4, 5, 6, 7}. In the merge mode where the merge candidate is used, the video signal processing device can use the weight value, and if it is not the merge mode, only {1, 7} can be used. The weight value can be signaled / parsed in the form of a BCW index. The weight value can be a value that minimizes the Template Matching (TM) cost. This method can be used in general merge, TM, adaptive DMVR, and MMVD modes in addition to BCW. Even when bi-predictive prediction is performed in the IBC mode, the video signal processing device can signal / parse the BCW index.

[0409] A template composed of surrounding samples of the current block is referred to as the first template. If bidirectional prediction is used, there can be two types of motion information. Among them, the template based on surrounding samples of the reference block (the second reference block) found with motion information MV0 becomes the second template, and the template based on surrounding samples of the reference block (the third reference block) found with motion information MV1 becomes the third template. At this time, the video signal processing device can generate a prediction block of the current block using two reference blocks based on two pieces of motion information. At this time, the video signal processing device can generate a final prediction block by applying a weighted average to the two reference blocks. The weights may be different for each reference block on a sample-by-sample or block-by-block basis, but the same value may be applied within a block. A filter relation using three templates may be required to derive the weight values. The relation may be predSample (final prediction sample value of the current block) = a0*P1+a1*P2+a2*offset. In the relation, a0, a1, a2 can be filter coefficients, and P1 can be a sample value of the second template or a sample value of the second reference block. In addition, the relation can be predSample (final predicted sample value of the current block) = a0*P1+a1*P2+offset. In addition, the relation can be predSample (final predicted sample value of the current block) = a0*P1+a1*P2+a2. P2 can be a sample value of the third template or a sample value of the third reference block. The offset can be a median value of the bit depth values ​​of the image, and can be 512 in the case of 10-bit depth. In addition, the offset can be an average value of templates of a specific reference block or an average value of two of the reference blocks. In addition, the offset can be any fixed value. When three templates are used, the sample value of the first template of the current block can be predSample, P1 can be the sample value of the second template, and P2 can be the sample value of the third template.a0, a1, and a2 can be derived based on the method of deriving filter coefficients from CCCM described in Equation 10. Alternatively, instead of using the BCW index described above, if the BCW flag is true, an additional 1-bit flag may be used to indicate whether bidirectional prediction using the above-described relation is performed. The BCW index may not be signaled / parsed. If the final predicted sample value of the current block is calculated through unidirectional prediction, the method used when bidirectional prediction is used, excluding the weighted average, may be applied. The filter coefficients may be reused in subsequent unidirectional / bidirectional blocks. The method of indicating whether bidirectional prediction using the above-described relation using an additional 1-bit flag may also be applied when bi-predictive prediction is performed in IBC mode.

[0410] Figure 52 is a diagram illustrating a process for generating a final predicted block by combining a weighted average of a current block predicted using unidirectional prediction and a block predicted using MHP mode. One or more additional motion-compensated prediction signals may be added for blocks predicted using MHP mode.

[0411] The final predicted block by combining the weighted average of the current block predicted by unidirectional prediction and the block predicted by MHP mode can be obtained by the following relationship.

[0412]

[0413] p in the relation n is a signal indicating inter-unidirectional or bidirectional prediction, and h n+1 may be an additional motion compensation prediction signal added. Weight can be determined as shown in the table below, and the weight can be indicated by a separate index (add_hyp_weight_idx).

[0414]

[0415] A template composed of surrounding samples of the current block is the first template. Motion information MV0 can indicate a reference block found by unidirectional prediction (a second reference block), and a template by surrounding samples of the reference block pointed to by MV0 becomes the second template, and a reference block found by motion information MV1 (a fourth reference block) can be an additional reference block of MHP, and a template by surrounding samples of the additional reference block of MHP becomes the third template. When a video signal processing device generates a prediction block of the current block using two reference blocks by motion information used for unidirectional prediction and an additional prediction block of MHP, a final prediction block can be generated by weighting and averaging the two reference blocks. The weights are different for each reference block in units of samples or blocks, but the same value can be applied within a block. Three templates are used to derive the weights. The relationship can be used. , , can be filter coefficients, and p n can be the final predicted sample value of the current block, and p n+1 can be a sample value of the first template, and p n may be a sample value of the second template or a sample value of the second reference block. h n+1 can be a sample value of the third template added by MHP or a sample value of the fourth reference block. The offset is the middle value of the bit depth value of the image, which can be 512 in the case of 10-bit depth. Alternatively, the offset can be the average value of the template of a specific reference block or the average value of two of the reference blocks. Alternatively, the offset can be any fixed value. , , can be derived based on the method of deriving filter coefficients in CCCM described through mathematical expression 10. Alternatively, three templates are used for weight derivation. The relationship can be used. Alternatively, three templates can be used to derive the weights. The relationship of can be used. The method described through Fig. 52 can replace the method using the weight flag of MHP and can operate as a sub-mode of the method using the weight flag of MHP. If the indicator indicating whether MHP of CU unit is true, the indicator indicating whether prediction method using the filter relationship derived by the CCCM method of the proposed method can be signaled / parsed. If the indicator indicating whether MHP of CU unit is true, the weight index of MHP may not be signaled / parsed.

[0416] Fig. 53 is a diagram illustrating a process of generating a final prediction block by weighting the bidirectionally predicted current block and the MHP reference block. A template composed of neighboring samples of the current block is set as a first template. Motion information (MV0 and MV1) can indicate reference blocks found by bidirectional prediction, and the template by neighboring samples of the reference block pointed to by MV0 becomes the second template, the template by neighboring samples of the reference block pointed to by MV1 becomes the third template, and the reference block found by the MV2 motion information (fourth reference block) can be an additional reference block of the MHP, and the template by neighboring samples of the additional reference block of the MHP becomes the fourth template. When the prediction block of the current block is generated by using the reference blocks by the three motion information (MV0, MV1, MV2) used for bidirectional prediction and the additional prediction block of the MHP, the video signal processing device can generate the final prediction block by applying a weighted average to the three reference blocks. The weighted average method can apply different weight values ​​for each reference block on a sample or block basis, but the same weight value can be applied within the block. Four templates are used to derive the weights. The relationship can be used. , , , can be filter coefficients, and p n+1 can be the final predicted sample value of the current block, and p n can be a sample value of the second template or a sample value of the second reference block, and p n1 may be a sample value of the third template or a sample value of the third reference block. h n+1The offset may be a sample value of the fourth template added by MHP or a sample value of the fourth reference block. The offset is a median value of the bit depth value of the image, which may be 512 in the case of 10-bit depth. Alternatively, the offset may be an average value of the template of a specific reference block or an average value of three of the reference blocks. Alternatively, the offset may be an arbitrary fixed value. , , , can be derived based on the method of deriving filter coefficients in CCCM described through mathematical expression 10. Alternatively, four templates are used to derive weights. The relationship can be used. Alternatively, four templates can be used to derive the weights. A relational expression can be used. The method described through Fig. 60 can replace the method using the weight flag of MHP and can operate as a sub-mode of the method using the weight flag of MHP. The filter coefficients in Figs. 52 and 53 can be reused in subsequent MHP prediction blocks or unidirectional / bidirectional prediction blocks. Alternatively, the used filter coefficients in Figs. 51, 52, and 53 can be stored in a separate memory and used in subsequent prediction blocks.

[0417] Figure 54 illustrates a method for generating a final prediction block when the current block is generated by inter-bidirectional prediction.

[0418] The template of the current prediction block is set as the first template. The motion compensation block generated based on the motion information MV0 is set as the first reference block, and the template of the first reference block is set as the second template. The motion compensation block generated based on the motion information MV1 is set as the second reference block, and the template of the second reference block is set as the second template. First filter values ​​can be derived based on the first template, the second template, and the CCCM filter relationship of Equation 10. Second filter values ​​can be derived based on the first template, the third template, and the CCCM filter relationship of Equation 10. The video signal processing device can generate first final samples using the derived first filter values ​​and samples of the first reference block, and can generate second final samples using the derived second filter values ​​and samples of the second reference block. The final prediction samples of the current block can be generated by weighting the first final samples and the second final samples. The BCW-related methods described with reference to FIG. 51 can be applied to the weights. Reference blocks added using the MHP method can be generated as weighted average values ​​by generating final samples of the added reference blocks described through the above-described Figure 54. The first filter values ​​and the second filter values ​​can be reused in other inter-unidirectional / bidirectional prediction blocks or stored in a separate memory for update management and reuse.

[0419] The methods described through FIGS. 51 to 54 can be applied to each color component (i.e., Y, Cb, Cr) or can be applied only to the Y component.

[0420] Figure 55 shows the form of a template required for a CCCM model for applying a filter model to a current block according to an embodiment of the present invention.

[0421] The current block of Fig. 55 may be a block to which at least one of the IBC mode, inter mode, and IntraTMP mode is applied.

[0422] CCCM (convolutional cross-component model) is a method in which a video signal processing device constructs a nonlinear model using the high correlation between a luminance signal and a chrominance signal located at the same location as the luminance signal, and then predicts a chrominance signal through the constructed nonlinear model. The template used by the CCCM model can be L-shaped or L-shaped. This is called an LT template. Figure 68(a) shows various combinations of templates used in the CCCM model. Depending on the template used by the CCCM model, the coefficient values ​​may vary, and the values ​​of the chrominance components predicted by the CCCM model may also vary. For example, a video signal processing device can generate a chrominance block by inducing each CCCM model using three types of templates. At this time, the video signal processing device can use the CCCM model with the highest performance. When the video signal processing device uses the CCCM model, the video signal processing device can use the CCCM-LT mode that uses an LT template, the CCCM-L mode that uses only the left template, and the CCCM-T mode that uses only the upper template, similar to the CCLM mode. At this time, the video signal processing device can signal a mode with high prediction performance. When the CCCM-LT model is used, the video signal processing device can use all template areas of A, B, and C in FIG. 55(a). When the CCCM-L model is used, the video signal processing device can use the A area template in FIG. 55(a) or the A+B area template. When the video signal processing device uses A+B as a template, the prediction performance of CCCM can increase as the template size increases. When the CCCM-T model is used, the video signal processing device can use the C area template in FIG. 55(a) or the C+B template.

[0423] When a CCCM model is used, a video signal processing device derives filter coefficients for a single model using the values ​​of samples within a preset template. Alternatively, the video signal processing device can obtain multiple CCCM models by grouping average values ​​of samples within preset templates. At this time, the video signal processing device can predict a chrominance block using the obtained multiple CCCM models. This method is referred to as MM-CCCM (multi-model CCCM). The video signal processing device can obtain an average value of a luminance component and use it to obtain the MM-CCCM. At this time, the luminance component may be a sample within a preset template. In another specific embodiment, the luminance component may be a luminance sample within a reference block CU / PU / TU that is not a template. The video signal processing device can selectively use either an average value of luminance samples within a template or an average value of luminance samples within a reference block, or a weighted average value.

[0424] In addition, the video signal processing device can expand the application of MM-CCCM to multiple modes according to the template format. Three modes, such as MM-CCCM-LT, MM-CCCM-L, and MM-CCCM-T, can be applied, and the bitstream can include information indicating a template applied to MM-CCCM among the three modes. When MM-CCCM-L is used, the video signal processing device can use the A region template in FIG. 55(a) or the A+B region template. In addition, when the video signal processing device uses the A+B region template, the prediction performance of MM-CCCM can increase as the template size increases. When MM-CCCM-T is used, the video signal processing device can use the C region template in FIG. 55(a) or the C+B template. In FIG. 55, the template size is described as 6, but the template size can vary. When a video signal processing device uses a partial template in MM-CCCM, the video signal processing device can use side samples by padding them with the nearest sample value, as in an LT template. At this time, if there are restored samples in the area of ​​the side samples, the video signal processing device can also use the values ​​of the restored samples.

[0425] Figure 56 shows a preset location for referencing a CCCM series model for filtering a current block according to an embodiment of the present invention.

[0426] The current block for filtering in Fig. 56 may be a block to which at least one of the IBC mode, inter mode, and IntraTMP mode is applied.

[0427] Fig. 56 shows adjacent positions 1, 2, 3, 4, and 5 based on the current block, and non-adjacent positions 6 to 23. When a filter model is applied to the current block, the CCCM model, mode information, and filter coefficients of the model and mode may be stored in memory or a decoding buffer. For example, when the number of filters of the CCCM model is 7, information indicating the 7 coefficients may be stored in the memory or a decoding buffer. Information about the filter coefficients of the CCCM model may be stored according to a preset block size. The preset block size may be any one of 2x2, 4x4, and the minimum luma / luminance prediction block size. At least one of the used filter model, the prediction mode filter coefficient value, the difference in the mean value, the difference based on the median value, and the difference in the minimum / maximum values ​​may be stored in the memory or the decoding buffer.

[0428] Information about the preset positions can be used for filtering the current block. Specifically, the video signal processing device can use previously used coefficients as is instead of deriving new filter coefficients for filtering the current block. The video signal processing device can search multiple preset positions in a preset order to obtain a preset number of final candidates. For example, the video signal processing device can search the preset positions from 1 to 23 of FIG. 56 in ascending order to obtain six final candidates. In addition, the video signal processing device can calculate a cost for each of the obtained final candidates to obtain an optimal candidate. The video signal processing device can include information indicating the obtained optimal candidate in the bitstream. Alternatively, the video signal processing device can calculate the SAD / SATD cost between a template composed of neighboring samples of the current prediction block and a template composed of neighboring samples of a position including a template / list predicted for each mode in the candidate list, and reorder each mode. The video signal processing device can include information about the index of each reordered mode in the bitstream. In the embodiments described above, the search position may be set based on a reference block instead of the current block.

[0429] At least one of CCCM, MM-CCCM, GLM, GL-CCCM, CCCM-ND, and CCCM-MDF can be applied to the current block filtering. At this time, multiple template types can be applied. GLM (Gradient Linear Model) is a method of constructing a model by additionally reflecting the slope of a luminance sample in a linear model such as CCLM, and predicting a chrominance signal through the constructed model. In GL-CCCM, a video signal processing device reflects a luminance sample of a position of a reference block corresponding to a sample position of a current block to be predicted, and vertical and horizontal differences (Gx, Gy) for eight samples around the luminance sample. In addition, the video signal processing device can derive a luminance sample for the current block by using the position (X, Y) and coefficient information of the current luminance sample. At this time, the position of the current luminance sample may be the upper left position of the reference template used to derive the CCCM model, the upper left position of the current block (or reference block), the relative position of the current pixel when the upper left position of the current block is (0,0), and a position recalculated based on an arbitrary offset value and an arbitrary shift value.

[0430] At this time, the position of the current luminance sample can be calculated through (relative position of the current pixel when the upper left position of the current block is (0,0) + difference between the upper left position of the reference template used to derive the CCCM model from the upper left position of the current block + pre-specified offset value) << pre-specified shift value). At this time, the pre-specified offset value can be an integer. For example, the pre-specified offset value can be 8. In addition, the pre-specified shift value can be an integer. For example, the pre-specified shift value can be 3. Specifically, the predicted value can be obtained through the following mathematical formula.

[0431] predIBCVal = c0C + c1Gy + c2Gx + c3Y + c4X + c5P + c6B

[0432] Gx and Gy can be obtained through the mathematical formulas below.

[0433]

[0434] CCCM-MDF (CCCM with multiple downsampling filters) is a method that utilizes multiple CCCM models using multiple downsampling filters. The filters can be as follows.

[0435]

[0436]

[0437] The embodiments described above with respect to color difference prediction can be applied to the embodiments described through FIG. 50.

[0438] Figure 56(b) shows information about a history-based filtering model. The history-based filtering model can be a filtering model applied to IBC, Inter mode, and IntraTMP mode. The size of the history-based filtering model can be 6. Information recently used for filtering can be stored in a FIFO (First In First Out) manner, and when using the information, it can be used in the order of the most recently stored information. The mode that performs filtering using the stored information in this way is referred to as filtering merge mode. The mode that performs filtering for IBC mode, Inter mode, and IntraTMP mode, respectively, can be referred to as IBC filtering merge mode, Inter filtering merge mode, and IntraTMP merge mode. Each of the IBC / Inter / IntraTMP filtering merge modes can be referred to as filtered IBC / Inter / IntraTMP merge mode.

[0439] The video signal processing device searches for final candidates from a plurality of pre-specified locations according to the method described above, and if the number of final candidates obtained is less than the pre-specified number, the video signal processing device can add final candidates based on information from the history-based IBC filtering model. For example, if the video signal processing device does not obtain six final candidates from Fig. 56(a), the video signal processing device can obtain as many final candidates as the number of final candidates that were not obtained from Fig. 56(b).

[0440] In another specific embodiment, the video signal processing device obtains final candidates from information of a history-based IBC filtering model, and if the number of obtained final candidates does not reach a predetermined number, the video signal processing device may add final candidates from a plurality of predetermined locations. In these embodiments, if duplicate final candidates are obtained, the duplicate candidates may be considered as a single final candidate.

[0441] Each filtered IBC / Inter / IntraTMP merge mode list may be composed of spatially adjacent candidates, non-adjacent candidates, temporal and shifted temporal candidates, and history-based candidates. Temporal candidates may be derived from frames or pictures at the same or preset positions in different frames or pictures in time. Shifted temporal candidates may be derived from positions shifted from the temporal candidates by a selected motion vector derived from the motion vectors of neighboring blocks of the current block. A flag indicating whether to apply each of the three merge modes (IBC / Inter / IntraTMP merge modes) may be included in the bitstream. A video signal processing device may signal / parse the flag. At this time, the flag may be signaled / parsed in units of CUs or PUs. If the value of the flag is 1 (or true), the video signal processing device can derive the filter mode and filter coefficients for the prediction block from the merge mode list instead of directly deriving them. Information regarding which candidate in the merge mode list is used can be additionally signaled / parsed. Alternatively, the three merge mode lists can be configured in an integrated manner. For example, the Filtered IBC / Inter / IntraTMP merge mode list can be integrated, and some of the merge mode lists (Filtered IBC / Inter or Filtered IBC / IntraTMP or Filtered Inter / IntraTMP) can be integrated. Alternatively, the history-based candidate of FIG. 56(b) can also be configured in an integrated manner. The video signal processing device can configure a single integrated filtered merge mode list based on the filter model and coefficient information used in Filtered IBC / Inter / IntraTMP.There may be a flag indicating whether a filtered merge mode is applied to a prediction block in which filtered IBC / Inter / IntraTMP is used. A video signal processing device may signal / parse the flag indicating whether the filtered merge mode is applied. If the value of the flag indicating whether the filtered merge mode is applied is 1 (or true), the video signal processing device may derive the filter mode and filter coefficients for the prediction block from the filtered merge mode list instead of directly deriving them. Alternatively, information may be present regarding which candidate is used in the filtered merge mode list, and the bitstream may signal / parse information regarding which candidate is used in the filtered merge mode list.

[0442] FIG. 57 shows an operation of applying CCCM-ND to current luma sample prediction according to an embodiment of the present invention.

[0443] The current luma sample of Fig. 57 may be a luma sample of the current block, and the current block may be a block to which at least one of the IBC mode, the Inter mode, and the IntraTMP mode is applied.

[0444] CCCM-ND, which is used for chroma sample prediction, is a method that uses luma samples before downsampling. A video signal processing device can apply CCCM-ND to the current luma sample prediction. The video signal processing device can derive filter coefficients by applying the sample of the reference block corresponding to the luma sample of the current block to be predicted, L0 in the embodiment of FIG. 57, and the surrounding five samples to the mathematical formula below. At this time, the video signal processing device can derive the filter coefficients using the LDL decomposition used in CCCM. Instead of FIG. 57(b) used in FIG. 57(a), the luminance sample position relationship of FIG. 57(c) can also be used.

[0445]

[0446] Here, offsetLuma can be a preset value or the value of a luma sample at a preset location. bitDepth can be the bit depth used to represent the sample. If the bit depth is 10 bits, bitDepth can be 512, which is half the bit depth, but it can also be another preset value.

[0447] In another embodiment, the video signal processing device can apply the luminance sample position relationship of FIG. 57(d). The video signal processing device can derive filter coefficients by applying the sample of the reference block corresponding to the luma sample of the current block to be predicted, L0 in the embodiment of FIG. 57(d) and 8 surrounding samples to the mathematical equation below. At this time, the video signal processing device can use a total of 14 filter coefficients.

[0448]

[0449] Whether filtered IBC / Inter / IntraTMP merge is enabled on a per-sequence basis can be signaled. The following describes syntax elements (flags) that indicate whether filtered IBC / Inter / IntraTMP merge is enabled on a per-sequence basis. The syntax elements (flags) that indicate whether filtered IBC / Inter / IntraTMP merge is enabled on a per-sequence basis can be described as filtered IBC / Inter / IntraTMP related flags, and there can be constraint information related flags that constrain each of the filtered IBC / Inter / IntraTMP related flags. The filtered IBC / Inter / IntraTMP related flags can be included in the Sequence parameter set RBSP syntax, and the constraint information related flags can be included in the General constraints information syntax. In addition, there can be a filtered merge related syntax element (flag) that indicates whether filtered merge is enabled on a per-sequence basis. Additionally, there may be constraint information-related flags that constrain the values ​​of syntax elements related to filtered merges. The syntax elements related to filtered merges may be included in the Sequence parameter set RBSP syntax, and the constraint information-related flags may be included in the General constraints information syntax.

[0450] Filtered IBC related flags:

[0451] When the value of sps_filtered_ibc_merge_enabled_flag is 1, sps_filtered_ibc_merge_enabled_flag can indicate that filtered IBC merge is enabled in the sequence. When the value of sps_filtered_ibc_merge_enabled_flag is 0, sps_filtered_ibc_merge_enabled_flag can indicate that filtered IBC merge is disabled in the sequence. sps_filtered_ibc_enabled_flag can indicate whether filtered IBC is enabled or not at the sequence level. When the value of sps_filtered_ibc_enabled_flag is 1, sps_filtered_ibc_enabled_flag can indicate that filtered IBC is enabled in the sequence. If the value of sps_filtered_ibc_enabled_flag is 0, sps_filtered_ibc_enabled_flag may indicate that filtered IBC is disabled in that sequence.

[0452] If the value of sps_filtered_ibc_enabled_flag is 1, the bitstream may include sps_filtered_ibc_merge_enabled_flag for the corresponding sequence. If the value of sps_filtered_ibc_enabled_flag is 1, the video signal processing device may parse sps_filtered_ibc_merge_enabled_flag for the corresponding sequence. If the value of sps_filtered_ibc_enabled_flag is 0, the bitstream may not include sps_filtered_ibc_merge_enabled_flag for the corresponding sequence. If the value of sps_filtered_ibc_enabled_flag is 0, the video signal processing device may infer sps_filtered_ibc_merge_enabled_flag for the corresponding sequence as 0 without parsing.

[0453] When the value of gci_no_filtered_ibc_constraint_flag is 1, the value of sps_filtered_ibc_enabled_flag can be constrained to 0. Also, when the value of gci_no_filtered_ibc_merge_constraint_flag is 0, the value of sps_filtered_ibc_enabled_flag can be unconstrained. When the value of gci_no_filtered_ibc_merge_constraint_flag is 1, the value of sps_filtered_ibc_merge_enabled_flag can be constrained to 0. When the value of gci_no_filtered_ibc_merge_constraint_flag is 0, the value of sps_filtered_ibc_merge_enabled_flag can be unconstrained.

[0454] Filtered Inter-related flags:

[0455] If the value of sps_filtered_Inter_merge_enabled_flag is 1, sps_filtered_Inter_merge_enabled_flag can indicate that filtered inter merge is enabled in the corresponding sequence. If the value of sps_filtered_Inter_merge_enabled_flag is 0, sps_filtered_Inter_merge_enabled_flag can indicate that filtered inter merge is disabled in the corresponding sequence.

[0456] sps_filtered_Inter_enabled_flag can indicate whether the filtered interface is enabled or disabled on a sequence basis. If the value of sps_filtered_Inter_enabled_flag is 1, it means that the filtered interface is enabled, and if the value of sps_filtered_Inter_enabled_flag is 0, it means that the filtered interface is disabled.

[0457] sps_filtered_Inter_merge_enabled_flag can be signaled / parsed if sps_filtered_Inter_enabled_flag has a value of 1 (true). If sps_filtered_Inter_enabled_flag has a value of 0 (false), sps_filtered_Inter_merge_enabled_flag is not signaled / parsed and the value of sps_filtered_Inter_merge_enabled_flag can be inferred to be a value indicating that inter-merge is disabled (e.g., 0).

[0458] If the value of gci_no_filtered_Inter_constraint_flag is 1, the value of sps_filtered_Inter_enabled_flag is constrained to 0, and if the value of gci_no_filtered_Inter_constraint_flag is 0, the value of sps_filtered_Inter_enabled_flag may not be constrained. If the value of gci_no_filtered_Inter_merge_constraint_flag is 1, the value of sps_filtered_Inter_merge_enabled_flag may be constrained to 0, and if the value of gci_no_filtered_Inter_merge_constraint_flag is 0, the value of sps_filtered_Inter_merge_enabled_flag may not be constrained.

[0459] Filtered IntraTMP related flags:

[0460] sps_filtered_IntraTMP_merge_enabled_flag can indicate whether Filtered IntraTMP is enabled or not on a sequence basis. If the value of sps_filtered_IntraTMP_merge_enabled_flag is 1, it can mean that Filtered IntraTMP merge mode is enabled. If the value of sps_filtered_IntraTMP_merge_enabled_flag is 0, it can mean that Filtered IntraTMP merge mode is not enabled.

[0461] sps_filtered_IntraTMP_enabled_flag can indicate whether Filtered IntraTMP is enabled or not on a sequence basis. If the value of sps_filtered_IntraTMP_enabled_flag is 1, it means Filtered IntraTMP is enabled. If the value of sps_filtered_IntraTMP_enabled_flag is 0, it means Filtered IntraTMP is not enabled. sps_filtered_IntraTMP_merge_enabled_flag can be signaled / parsed if the value of sps_filtered_IntraTMP_enabled_flag is 1 (true). If the value of sps_filtered_IntraTMP_enabled_flag is 0 (false), sps_filtered_IntraTMP_merge_enabled_flag is not signaled / parsed, and the value of sps_filtered_IntraTMP_merge_enabled_flag can be inferred to be 0.

[0462] If the value of gci_no_filtered_IntraTMP_constraint_flag is 1, the value of sps_filtered_IntraTMP_enabled_flag can be constrained to 0. If the value of gci_no_filtered_IntraTMP_constraint_flag is 0, the value of sps_filtered_IntraTMP_enabled_flag can be unconstrained. If the value of gci_no_filtered_IntraTMP_merge_constraint_flag is 1, the value of sps_filtered_IntraTMP_merge_enabled_flag can be constrained to 0, and if the value of gci_no_filtered_IntraTMP_merge_constraint_flag is 0, the value of sps_filtered_IntraTMP_merge_enabled_flag can be unconstrained.

[0463] Filtered merge related flags:

[0464] sps_filtered_merge_enabled_flag can indicate whether filtered merge is enabled or disabled on a sequence basis. If the value of sps_filtered_merge_enabled_flag is 1, it can mean that filtered merge is enabled. If the value of sps_filtered_merge_enabled_flag is 0, it can mean that filtered merge is not enabled.

[0465] sps_filtered_prediction_enabled_flag can indicate whether filtered prediction is enabled or not at the sequence level. If the value of sps_filtered_prediction_enabled_flag is 1, it can mean that filtered prediction is enabled. If the value of sps_filtered_prediction_enabled_flag is 0, it can mean that filtered prediction is not enabled. sps_filtered_merge_enabled_flag can be signaled / parsed when the value of sps_filtered_prediction_enabled_flag is 1 (true). In addition, when the value of sps_filtered_prediction_enabled_flag is 1 (true), sps_filtered_IBC_enabled_flag, sps_filtered_Inter_enabled_flag, and sps_filtered_IntraTMP_enabled_flag can be signaled / parsed. If the value of sps_filtered_prediction_enabled_flag is 0 (false), sps_filtered_merge_enabled_flag, sps_filtered_IBC_enabled_flag, sps_filtered_Inter_enabled_flag, and sps_filtered_IntraTMP_enabled_flag are not signaled / parsed, and the values ​​of sps_filtered_merge_enabled_flag, sps_filtered_IBC_enabled_flag, sps_filtered_Inter_enabled_flag, and sps_filtered_IntraTMP_enabled_flag can be inferred to be 0.

[0466] If the value of gci_no_filtered_merge_constraint_flag is 1, the value of sps_filtered_merge_enabled_flag may be constrained to 0. If the value of gci_no_filtered_merge_constraint_flag is 0, the value of sps_filtered_merge_enabled_flag may not be constrained. It may be equal to , and if it is 1, there may be no constraints.

[0467] If the value of gci_no_filtered_prediction_constraint_flag is 1, the value of sps_filtered_prediction_enabled_flag may be constrained to 0. If the value of gci_no_filtered_prediction_constraint_flag is 0, the value of sps_filtered_prediction_enabled_flag may not be constrained.

[0468] The bitstream may include a flag indicating whether CCCM, GL-CCCM, CCCM-ND, and CCCM-MDF, each used for chrominance component prediction, is active at the sequence level.

[0469] When the value of sps_cccm_enabled_flag is 1, sps_cccm_enabled_flag can indicate that CCCM is enabled at the sequence level. When the value of sps_cccm_enabled_flag is 0, sps_cccm_enabled_flag can indicate that CCCM is disabled at the sequence level. When the value of sps_gl_cccm_enabled_flag is 1, sps_gl_cccm_enabled_flag can indicate that GL-CCCM is enabled at the sequence level. When the value of sps_gl_cccm_enabled_flag is 0, sps_gl_cccm_enabled_flag can indicate that GL-CCCM is disabled. When the value of sps_cccm-nd_enabled_flag is 1, sps_cccm-nd_enabled_flag can indicate that CCCM-ND is enabled at the sequence level. When the value of sps_cccm-nd_enabled_flag is 0, sps_cccm-nd_enabled_flag can indicate that CCCM-ND is disabled at the sequence level. When the value of sps_cccm-mdf_enabled_flag is 1, sps_cccm-mdf_enabled_flag can indicate that CCCM-MDF is enabled at the sequence level. When the value of sps_cccm-mdf_enabled_flag is 0, sps_cccm-mdf_enabled_flag can indicate that CCCM-MDF is disabled at the sequence level.

[0470] In another specific embodiment, GL-CCCM, CCCM-ND, and CCCM-MDF based on CCCM may be enabled or disabled by a single sps_cccm_enabled_flag. If the value of sps_ccp_merge_enabled_flag is 1, sps_ccp_merge_enabled_flag may indicate that CCP merge mode is enabled at the sequence level. If the value of sps_ccp_merge_enabled_flag is 0, sps_ccp_merge_enabled_flag may indicate that CCP merge mode is disabled at the sequence level.

[0471] The flags described above are applicable when there are luminance samples and chrominance samples, which are the same conditions as CCLM. Therefore, if the value of the chroma format index is not 0, the bitstream may include the flags described above. In addition, if the value of the chroma format index is not 0, the video signal processing device may parse the flags described above from the bitstream. If the value of the chroma format index is 0, the bitstream may not include the flags described above. In addition, if the value of the chroma format index is 0, the video signal processing device may infer the values ​​of the flags described above as 0.

[0472] Additionally, the bitstream may include sps_ccp_merge_enabled_flag only if at least one of sps_cclm_enabled_flag or sps_cccm_enabled_flag is true. If at least one of sps_cclm_enabled_flag or sps_cccm_enabled_flag is true, the video signal processing device may parse sps_ccp_merge_enabled_flag from the bitstream. If both sps_cclm_enabled_flag and sps_cccm_enabled_flag are false, the bitstream may not include sps_ccp_merge_enabled_flag. If both sps_cclm_enabled_flag and sps_cccm_enabled_flag are false, the video signal processing device may infer the value of sps_ccp_merge_enabled_flag as 0 without parsing sps_ccp_merge_enabled_flag from the bitstream.

[0473] If at least one of sps_cclm_enabled_flag and sps_cccm_enabled_flag is true, the bitstream may include a flag indicating whether a CCCM-based other mode is enabled. If at least one of sps_cclm_enabled_flag and sps_cccm_enabled_flag is true, the video signal processing device may parse the flag indicating whether a CCCM-based other mode is enabled in the bitstream. The CCCM-based other mode may include at least one of GL-CCCM, CCCM-ND, and CCCM-MD.

[0474] Fig. 59 is a flowchart illustrating a method for predicting a chroma component block of a current block according to one embodiment of the present invention.

[0475] Referring to FIG. 59, the video signal processing device can predict the chroma component block of the current block based on the methods described above through FIGS. 1 to 58.

[0476] The video signal processing device can obtain a luma block vector of a first luma component block of the current block (S5810).

[0477] The video signal processing device can obtain a chroma reference block, which is a chroma component block, based on the luma block vector (S5820).

[0478] The video signal processing device can predict the first chroma component block of the current block based on the chroma reference block (S5830).

[0479] The first luma component block and the first chroma component block may correspond to each other.

[0480] The above chroma reference block is a chroma component block of a reference block indicated by a scaled block vector, and the scaled block vector can be obtained by scaling the luma block vector based on a chroma format of the current block.

[0481] The video signal processing device can obtain a linear model for predicting the first chroma component block, obtain a non-linear model for predicting the first chroma component block, and predict the first chroma component block based on the linear model and the non-linear model.

[0482] The first chroma component block may be obtained based on a first prediction block obtained by applying the linear model to the chroma reference block, and a second prediction block obtained by applying the non-linear model to the chroma reference block.

[0483] The second prediction block obtained by applying the above non-linear model may be a block predicted by the DBV (Direct block vector) method.

[0484] The second prediction block may be a block predicted based on any one of MTS (multiple transform selection), LFNST (Low Frequency Non-separable Transform), and NSPT (Non-Separable Primary Transform).

[0485] A video signal processing device can obtain a first neighboring block of a luma reference block, which is a luma component block of the reference block, obtain a second neighboring block of the chroma reference block, obtain a CCCM (Convolutional cross-component intra prediction model) based on the first neighboring block and the second neighboring block, and predict the first chroma component block based on the CCCM.

[0486] The above first luma component block can be applied with IBC (Intra block copy) mode or Intra template matching mode.

[0487] The methods described herein can be performed by a processor of a video signal processing device (decoder or encoder). Furthermore, the encoder can generate a bitstream decoded by the methods described above. Furthermore, the bitstream generated by the encoder can be stored on a computer-readable, non-transitory storage medium (recording medium).

[0488] While this specification primarily addresses the decoder's perspective, the same principles apply to encoders. While the term "parsing" in this specification focuses on the process of obtaining information from a bitstream, it can also be interpreted as configuring that information into a bitstream from an encoder's perspective. Therefore, the term "parsing" is not limited to decoder operations; it can also be interpreted as the act of configuring a bitstream in an encoder. Furthermore, such a bitstream can be stored and configured on a computer-readable recording medium.

[0489] The embodiments of the present invention described above may be implemented through various means. For example, the embodiments of the present invention may be implemented through hardware, firmware, software, or a combination thereof.

[0490] In the case of hardware implementation, the method according to embodiments of the present invention may be implemented by one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, etc.

[0491] When implemented via firmware or software, the methods according to embodiments of the present invention may be implemented in the form of modules, procedures, or functions that perform the functions or operations described above. The software code may be stored in memory and executed by the processor. The memory may be located internally or externally to the processor and may exchange data with the processor via various known means.

[0492] Some embodiments may also be implemented in the form of a recording medium containing computer-executable instructions, such as program modules, executed by a computer. Computer-readable media can be any available media that can be accessed by a computer, and includes both volatile and nonvolatile media, removable and non-removable media. Furthermore, computer-readable media can include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. Communication media typically contains computer-readable instructions, data structures, or other data in a modulated data signal, such as program modules, or other transport mechanisms, and includes any information delivery media.

[0493] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be construed as illustrative and not restrictive in all respects. For example, components described as being single may be implemented in a distributed manner, and similarly, components described as being distributed may be implemented in a combined manner.

[0494] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. In a video signal decoding device, Includes a processor, The above processor, Obtain the luma block vector of the first luma component block of the current block, Obtain a chroma reference block, which is a chroma component block, based on the above luma block vector, Predicting a first chroma component block of the current block based on the chroma reference block, A video signal decoding device, wherein the first luma component block and the first chroma component block correspond to each other.

2. In paragraph 1, The above chroma reference block is a chroma component block of a reference block indicated by a scaled block vector, A video signal decoding device, wherein the scaled block vector is obtained by scaling the luma block vector based on the chroma format of the current block.

3. In paragraph 1, The above processor, Obtain a linear model for prediction of the first chroma component block, Obtain a non-linear model for prediction of the first chroma component block, A video signal decoding device that predicts the first chroma component block based on the linear model and the non-linear model.

4. In paragraph 3, The above first chroma component block, A first prediction block obtained by applying the linear model to the chroma reference block, A video signal decoding device, obtained based on a second prediction block obtained by applying the non-linear model to the chroma reference block.

5. In paragraph 4, A video signal decoding device, wherein the second prediction block obtained by applying the above non-linear model is a block predicted by a DBV (Direct block vector) method.

6. In paragraph 5, The second prediction block is, A video signal decoding device, wherein the block is predicted based on any one of MTS (multiple transform selection), LFNST (Low Frequency Non-separable Transform), and NSPT (Non-Separable Primary Transform).

7. In paragraph 1, The above processor, Obtain the first surrounding block of the luma reference block, which is the luma component block of the above reference block, Obtaining a second surrounding block of the above chroma reference block, Obtain a CCCM (Convolutional cross-component intra prediction model) based on the first peripheral block and the second peripheral block, A video signal decoding device that predicts the first chroma component block based on the CCCM.

8. In paragraph 6, A video signal decoding device, wherein the first luma component block is applied with an intra block copy (IBC) mode or an intra template matching mode.

9. In a video signal encoding device, Includes a processor, The above processor, Obtain a bitstream decoded by a decoding method, The above decoding method is, A step of obtaining a luma block vector of a first luma component block of the current block; A step of obtaining a chroma reference block, which is a chroma component block, based on the luma block vector; and A step of predicting a first chroma component block of the current block based on the chroma reference block, A video signal encoding device, wherein the first luma component block and the first chroma component block correspond to each other.

10. In paragraph 9, The above chroma reference block is a chroma component block of a reference block indicated by a scaled block vector, A video signal encoding device, wherein the scaled block vector is obtained by scaling the luma block vector based on the chroma format of the current block.

11. In paragraph 9, The above decoding method is, A step of obtaining a linear model for prediction of the first chroma component block; A step of obtaining a non-linear model for prediction of the first chroma component block; A video signal encoding device further comprising a step of predicting the first chroma component block based on the linear model and the non-linear model.

12. In paragraph 11, The above first chroma component block, A first prediction block obtained by applying the linear model to the chroma reference block, A video signal encoding device, obtained based on a second prediction block obtained by applying the non-linear model to the chroma reference block.

13. In Article 12, A video signal encoding device, wherein the second prediction block obtained by applying the non-linear model is a block predicted by the DBV (Direct block vector) method.

14. In paragraph 13, The second prediction block is, A video signal encoding device, wherein the block is predicted based on any one of MTS (multiple transform selection), LFNST (Low Frequency Non-separable Transform), and NSPT (Non-Separable Primary Transform).

15. In paragraph 9, The above decoding method is, A step of obtaining a first surrounding block of a luma reference block, which is a luma component block of the above reference block; A step of obtaining a second surrounding block of the above chroma reference block; A step of obtaining a CCCM (Convolutional cross-component intra prediction model) based on the first peripheral block and the second peripheral block; A video signal encoding device further comprising a step of predicting the first chroma component block based on the CCCM.

16. In paragraph 15, A video signal decoding device, wherein the first luma component block is applied with an intra block copy (IBC) mode or an intra template matching mode.

17. In a computer-readable non-transitory storage medium storing a bitstream, the bitstream is decoded by a decoding method, The above decoding method is, A step of obtaining a block vector of a first luma component block of the current block; A step of obtaining a chroma reference block which is a chroma component block of a reference block indicated by the above block vector; and A step of predicting a first chroma component block of the current block based on the chroma reference block, A non-transitory storage medium in which the first luma component block and the first chroma component block correspond to each other.

18. In paragraph 17, The above chroma reference block is a chroma component block of a reference block indicated by a scaled block vector, A non-transitory storage medium, wherein the scaled block vector is obtained by scaling the luma block vector based on the chroma format of the current block.

19. In paragraph 17, The above decoding method is, A step of obtaining a linear model for prediction of the first chroma component block; A step of obtaining a non-linear model for prediction of the first chroma component block; A non-transitory storage medium further comprising a step of predicting the first chroma component block based on the linear model and the non-linear model.

20. In paragraph 19, The above first chroma component block, A first prediction block obtained by applying the linear model to the chroma reference block, A non-transitory storage medium obtained based on a second prediction block obtained by applying the non-linear model to the chroma reference block.

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