Intra-predictive-based video signal processing method and apparatus

Abstract

To provide video signal processing method and apparatus for encoding or decoding video signals.SOLUTION: A video signal processing method includes the steps of determining whether an intra sub-partition (ISP) mode is applied to the current block, dividing the current block into a plurality of horizontal or vertical rectangular transform blocks when the ISP mode is applied to the current block, generating predictive blocks for the transform blocks by performing intra prediction on each of the transform blocks, and reconstructing the current block on the basis of the residual block of the transform block and the predictive block.SELECTED DRAWING: Figure 20

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for processing video signals, and more particularly to a method and apparatus for processing video signals that encode or decode video signals based on intra-prediction. [Background technology]

[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. While compression coding can target various media such as audio, video, and text, the technique specifically for video compression is called video compression. Compression coding of video signals is performed by removing excess information by considering spatial, temporal, and probabilistic correlations. However, with the recent development of diverse media and data transmission systems, there is a growing demand for more efficient video signal processing methods and devices. [Overview of the project] [Problems that the invention aims to solve]

[0003] The objective of this invention is to improve the coding efficiency of video signals. Specifically, this invention proposes a method for performing PDPC (position-dependent intra prediction combination) and LFNST (Low-Frequency Non-Separable Transform) in units where prediction and reconstruction are performed by applying intra sub-partitions. [Means for solving the problem]

[0004] To solve the above-mentioned problems, the present invention provides the following video signal processing device and video signal processing method.

[0005] According to one embodiment of the present invention, a video signal processing method includes the steps of: determining whether or not an intra-sub-partition (ISP) mode is applied to the current block; if the ISP mode is applied to the current block, dividing the current block into a plurality of horizontal or vertical rectangular transformation blocks; generating a prediction block of the transformation block by performing intra-prediction on each of the transformation blocks; and restoring the current block based on the residual block of the transformation block and the prediction block, wherein the step of generating the prediction block may include performing position-dependent intra-prediction sample filtering on a unit of transformation blocks divided from the current block.

[0006] As an embodiment, the step of generating the prediction block may further include a step of determining whether or not the position-dependent intra-predictive sample filtering is applied based on at least one of the width and height of the transformation block.

[0007] As an example, the step of determining whether or not to apply the position-dependent intra predictive sample filtering may be performed by deciding to apply the position-dependent intra predictive sample filtering when the width of the transformation block is greater than or equal to a preset reference value, and the height of the transformation block is greater than or equal to the preset reference value.

[0008] As an example, the residual block of the transformation block may be derived by performing an inverse secondary transform and an inverse primary transform on a unit of the transformation block.

[0009] As an embodiment, the process may include the steps of: determining whether or not a quadratic transformation is applied to the current block; if the quadratic transformation is applied to the current block, deriving a set of quadratic transformation kernels to be applied to the current block from a predefined set of quadratic transformation kernels based on the intra-prediction mode of the current block; determining the quadratic transformation kernel to be applied to the current block within the determined set of quadratic transformation kernels; generating a quadratic inversely transformed block of the transformation block by performing a quadratic inversely transformed block on the transformation block unit; and generating a residual block of the transformation block by performing a linear inversely transformed block on the quadratic inversely transformed block.

[0010] According to one embodiment of the present invention, a video signal processing device is provided, which includes a processor, the processor determines whether or not an intra-sub-partition (ISP) mode is applied to the current block, and if the ISP mode is applied to the current block, divides the current block into a plurality of horizontal or vertical rectangular transformation blocks, generates predicted blocks of the transformation blocks by performing intra-prediction on each of the transformation blocks, restores the current block based on the residual blocks of the transformation blocks and the predicted blocks, and the processor performs position-dependent intra-prediction sample filtering on a unit of transformation blocks divided from the current block.

[0011] As an example, the processor may determine whether or not the position-dependent intra predictive sample filtering is applied based on at least one of the width and height of the conversion block.

[0012] As an example, the processor may decide to apply the position-dependent intra predictive sample filtering if the width of the conversion block is greater than or equal to a preset reference value, and the height of the conversion block is greater than or equal to the preset reference value.

[0013] As an example, the residual block of the transformation block may be derived by performing an inverse secondary transform and an inverse primary transform on a unit of the transformation block.

[0014] As an example, the processor can determine whether or not a quadratic transformation is applied to the current block, and if the quadratic transformation is applied to the current block, it can derive a set of quadratic transformation kernels to be applied to the current block from a predefined set of quadratic transformation kernels based on the intra-prediction mode of the current block, determine a quadratic transformation kernel to be applied to the current block within the determined set of quadratic transformation kernels, generate a quadratic inversely transformed block of the transformation block by performing a quadratic inversely transformed block, and generate a residual block of the transformation block by performing a linear inversely transformed block.

[0015] According to one embodiment of the present invention, a video signal processing method is provided, comprising the steps of: determining whether or not an intra-sub-partition (ISP) mode is applied to the current block; if the ISP mode is applied to the current block, dividing the current block into a plurality of horizontal or vertical rectangular transformation blocks; generating a predicted block of the transformation block by performing intra-prediction on each of the transformation blocks; and generating a residual block of the transformation block by subtracting the predicted block from the original block, wherein the step of generating the predicted block includes performing position-dependent intra-prediction sample filtering on a unit of transformation blocks divided from the current block.

[0016] According to one embodiment of the present invention, a non-transitory computer-executable component is provided, which stores a computer-executable component configured to run on one or more processors of a computing device, wherein the computer-executable component determines whether or not an intra-sub-partition (ISP) mode is applied to the current block, and if the ISP mode is applied to the current block, divides the current block into a plurality of horizontal or vertical rectangular transformation blocks, generates predicted blocks of the transformation blocks by performing intra-prediction on each of the transformation blocks, restores the current block based on the residual blocks of the transformation blocks and the predicted blocks, and the computer-executable component performs position-dependent intra-prediction sample filtering on a unit of transformation blocks divided from the current block. [Effects of the Invention]

[0017] According to an embodiment of the present invention, the coding efficiency of a video signal can be increased. Further, according to an embodiment of the present invention, by performing PDPC (position-dependent intra prediction combination) and LFNST in units of conversion blocks divided by intra sub-partitions, the accuracy of prediction can be increased and the compression performance can be improved.

Brief Description of the Drawings

[0018] <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​This figure illustrates a method for applying PDPC (position-dependent intraprediction combination) according to one embodiment of the present invention. [Figure 12] This figure illustrates a reference sample used in PDPC by intra-prediction mode as one embodiment of the present invention. [Figure 13] This figure illustrates a reference sample used in PDPC by intra-prediction mode as one embodiment of the present invention. [Figure 14] This figure illustrates a method for applying ISP (Intra subpartitions) and PDPC (position-dependent intra prediction combination) to a coding block according to one embodiment to which the present invention is applied. [Figure 15] This figure illustrates a conversion unit splitting process method according to one embodiment of the present invention. [Figure 16] This figure shows the encoding / decoding process via primary and secondary transforms according to one embodiment to which the present invention is applied. [Figure 17] This figure illustrates a method for selecting a conversion kernel used in a secondary conversion according to one embodiment of the present invention. [Figure 18] This figure illustrates an example of a method for applying a secondary conversion to a conversion block unit according to one embodiment of the present invention. [Figure 19] This figure shows a method for applying PDPC to a current coding block to which an intra-predictive mode according to one embodiment to which the present invention is applied is applied. [Figure 20] This is a flowchart showing a video signal processing method according to one embodiment of the present invention. [Modes for carrying out the invention]

[0019] The terminology used herein has been selected as widely used and general terms as possible, taking into account the function of the present invention; however, this may vary depending on the intent of the articulators, conventions, or the emergence of new technologies. In addition, in certain cases, the applicant has arbitrarily selected some terms, in which case their meaning will be described in the section describing the form of implementation of the invention. Therefore, it is important to clarify that the terminology used herein is not merely a set of names, but should be interpreted based on the substantive meaning of the term and the overall content of this specification.

[0020] In this specification, some terms are interpreted as follows: Coding may be interpreted as encoding or coding in some cases. 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 this specification, the term video signal processing device is used as a conceptual term that includes both encoders and decoders. Information is a term that includes values, parameters, coefficients, elements, etc., and may be interpreted differently in some cases, so the present invention is not limited thereto. 'Unit' is used to mean a basic unit of image processing or a specific location in a picture, and refers to an image region that includes at least one of the luma component and chroma component. Also, 'block' refers to an image region that includes a specific component among the luminance component and chrominance component (i.e., Cb and Cr). However, in some embodiments, terms such as 'unit', 'block', 'partition', and 'region' may be used interchangeably. Furthermore, in this specification, the term "unit" is used as a concept that includes coding units, prediction units, and transformation units. "Picture" refers to a field or frame, and in some embodiments, these terms are used interchangeably.

[0021] Figure 1 is a schematic block diagram of a video signal encoding device 100 according to one embodiment of the present invention. Referring to Figure 1, the encoding device 100 according to this specification includes a conversion unit 110, a quantization unit 115, an inverse quantization unit 120, an inverse conversion unit 125, a filtering unit 130, a prediction unit 150, and an entropy coding unit 160.

[0022] The conversion unit 110 converts the residual signal, which is the difference between the input video signal and the predicted signal generated by the prediction unit 150, to obtain conversion coefficient values. For example, discrete cosine transform (DCT), discrete sine transform (DST), or wavelet transform may be used. Discrete cosine transform and discrete sine transform divide the input picture signal into block form and perform the transformation. In the transformation, the coding efficiency may differ depending on the distribution and characteristics of the values ​​within the transformation domain. The quantization unit 115 quantizes the values ​​of the conversion coefficients output in the conversion unit 110.

[0023] To improve coding efficiency, instead of directly coding the picture signal, a method is used in which the picture is predicted using a pre-coded region via the prediction unit 150, and the restored picture is obtained by adding the residual value between the original picture and the predicted picture to the predicted picture. To prevent mismatches between the encoder and decoder, the encoder should use information that is also available to the decoder when performing prediction. For this purpose, the encoder performs a further process of restoring the currently encoded block. The inverse quantization unit 120 inversely quantizes the conversion coefficient value, and the inverse transformation unit 125 restores the residual value using the inversely quantized conversion coefficient value. Meanwhile, the filtering unit 130 performs filtering operations to improve the quality of the restored picture and enhance coding efficiency. For example, this may include a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter. The filtered picture is stored in the Decoded Picture Buffer (DPB) 156 for output or use as a reference picture.

[0024] To improve coding efficiency, instead of directly coding the picture signal, a method is used in which the picture is predicted using an already coded region in the prediction unit 150, and the restored picture is obtained by adding the residual value between the original picture and the predicted picture to the predicted picture. The intra-prediction unit 152 performs in-screen prediction within the current picture, and the inter-prediction unit 154 predicts the current picture using a reference picture stored in the decoded picture buffer 156. The intra-prediction unit 152 performs in-screen prediction from the restored region within the current picture and transmits the in-screen coding information to the entropy coding unit 160. The inter-prediction unit 154 may further include a motion estimation unit 154a and a motion compensation unit 154b. The motion estimation unit 154a obtains the motion vector value of the current region by referring to a specific restored region. The motion estimation unit 154a transmits position information of the reference region (reference frame, motion vector, etc.) to the entropy coding unit 160 so that it can be included in the bitstream. The motion compensation unit 154b performs inter-screen motion compensation using the motion vector values ​​transmitted from the motion estimation unit 154a.

[0025] 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 the current picture, and the inter-prediction unit 154 performs inter-prediction, predicting the current picture using a reference buffer stored in the decoded picture buffer 156. The intra-prediction unit 152 performs intra-prediction from the restored samples in the current picture and transmits intra-coded information to the entropy coding unit 160. The intra-coded information includes at least one of the following: intra-prediction mode, MPM (Most Probable Mode) flag, and MPM index. The intra-coded information may include information about the reference sample. The inter-prediction unit 154 includes a motion estimation unit 154a and a motion compensation unit 154b. The motion estimation unit 154a obtains motion vector values ​​for the current region by referring to a specific region of the restored reference signal picture. The motion estimation unit 154a transmits a set of motion information (reference picture index, motion vector information) for the reference region to the entropy coding unit 160. The motion compensation unit 154b performs motion compensation using the motion vector values ​​transmitted from the motion compensation unit 154a. The inter-prediction unit 154 transmits inter-coded information, including motion information for the reference region, to the entropy coding unit 160.

[0026] In a further embodiment, the prediction unit 150 includes an intrablock copy (BC) prediction unit (not shown). The intraBC prediction unit performs intraBC prediction from the restored samples in the current picture and transmits the intraBC encoded information to the entropy coding unit 160. The intraBC 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 intraBC prediction unit performs intraBC prediction using the obtained block vector value. The intraBC prediction unit transmits the intraBC encoded information to the entropy coding unit 160. The intraBC prediction unit includes block vector information.

[0027] Once the picture prediction described above is performed, the conversion unit 110 converts the residual values ​​between the original picture and the predicted picture to obtain conversion coefficient values. In this case, the conversion is performed in units of specific blocks within the picture, but the size of the specific block is variable within a preset range. The quantization unit 115 quantizes the values ​​of the conversion coefficients generated by the conversion unit 110 and transmits them to the entropy coding unit 160.

[0028] The entropy coding unit 160 generates a video signal bitstream by entropy coding information indicating quantized conversion coefficients, intra-coded information, and inter-coded information. The entropy coding unit 160 uses methods such as variable length coding (VLC) and arithmetic coding. Variable length coding (VLC) converts input symbols into a sequence of codewords, but the length of the codewords is variable. For example, frequently occurring symbols are represented by short codewords, and less frequently occurring symbols are represented by long codewords. Context-based Adaptive Variable Length Coding (CAVLC) is used as the variable length coding method. Arithmetic coding converts a sequence of data symbols into a single prime number, but arithmetic coding obtains the optimal number of prime bits necessary to represent each symbol. Context-based Adaptive Binary Arithmetic Coding (CABAC) is used as the arithmetic coding method. For example, the entropy coding unit 160 can binary-code information indicating quantized transformation coefficients. Furthermore, the entropy coding unit 160 can arithmetically encode the binary-coded information to generate a bitstream.

[0029] The generated bitstream is encapsulated in Network Abstraction Layer (NAL) units as its basic units. Each NAL unit contains an encoded integer number of coding tree units. To decode the bitstream with a video decoder, the bitstream must first be separated into NAL units, and then each separated NAL unit must be decoded. Meanwhile, the information necessary for decoding the video signal bitstream is transmitted via Raw Byte Sequence Payloads (RBSPs) of higher-level sets such as Picture Parameter Set (PPS), Sequence Parameter Set (SPS), and Video Parameter Set (VPS).

[0030] On the other hand, the block diagram in Figure 1 shows an encoding device 100 according to one embodiment of the present invention, and the separated blocks show the elements of the encoding device 100 in a logically distinguishable manner. Therefore, the elements of the encoding device 100 described above are mounted on one chip or multiple chips depending on the device design. According to one embodiment, the operation of each element of the encoding device 100 described above is performed by a processor (not shown).

[0031] Figure 2 is a schematic block diagram of a video signal decoding apparatus 200 according to an embodiment of the present invention. Referring to Figure 2, the decoding apparatus 200 according to this specification 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.

[0032] The entropy decoding unit 210 entropy decodes the video signal bitstream and extracts conversion coefficient information, intra-encoded information, inter-encoded information, etc., for each region. For example, the entropy decoding unit 210 can obtain binary-coded conversion coefficient information for a specific region from the video signal bitstream. The entropy decoding unit 210 also performs inverse binary-coded conversion of the binary-coded conversion coefficient to obtain quantized conversion coefficients. The inverse quantization unit 220 inverse quantizes the quantized conversion coefficients, and the inverse conversion unit 225 restores the residual value using the inverse quantized conversion coefficient. The video signal processing device 200 adds the residual value obtained from the inverse conversion unit 225 with the predicted value obtained from the prediction unit 250 to restore the original pixel value.

[0033] Meanwhile, the filtering unit 230 improves image quality by filtering the picture. This includes a deblocking filter to reduce block distortion and / or an adaptive loop filter to remove distortion from the entire picture. The filtered picture is either output or stored in the decoded picture buffer (DPB) 256 to be used as a reference picture for the next picture.

[0034] 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 aforementioned entropy decoding unit 210, the conversion coefficients for each region, intra / inter-encoded information, etc. To restore the current block from which decoding is performed, the current picture containing the current block or the decoded region of another picture can 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 intra-prediction, inter-prediction, and intra-BC prediction is called an inter-picture (or tile / slice). Among interpictures (or tiles / slice), a picture (or tile / slice) that uses up to one motion vector and a reference picture index to predict the sample value of each block is called a predictive picture or P-picture (or tile / slice), and a picture (or tile / slice) that uses up to two motion vectors and a reference picture index is called a bi-predictive picture or B-picture (or tile / slice). In other words, a P-picture (or tile / slice) uses up to one motion information set to predict each block, and a B-picture (or tile / slice) uses up to two motion information sets to predict each block. Here, a motion information set includes one or more motion vectors and one reference picture index.

[0035] The intra-prediction unit 252 generates a prediction block using intra-encoded information and the recovered sample in the current picture. As described above, the intra-encoded information includes at least one of the intra-prediction mode, the MPM (MOST Probable Mode) flag, and the MPM index. The intra-prediction unit 252 predicts the sample value of the current block using the recovered sample located to the left and / or above the current block as a reference sample. In this disclosure, the recovered sample, the reference sample, and the sample of the current block represent pixels. The sample value also represents the pixel value.

[0036] In one embodiment, the reference sample is a sample included in the surrounding blocks of the current block. For example, the reference sample is a sample adjacent to the left boundary and / or the upper boundary of the current block. Alternatively, the reference sample is a sample located in the surrounding blocks of the current block that lies on a line within a predetermined distance from the left boundary and / or on a line within a predetermined distance from the upper boundary of the current block. In this case, the surrounding blocks of the current block include at least one of the following blocks adjacent to the current block: the left (L) block, the upper (A) block, the lower left (BL) block, the upper right (AR) block, or the upper left (AL) block.

[0037] The interprediction unit 254 generates a prediction block using the reference picture and intercoded information stored in the decoded picture buffer 256. The intercoded information includes a set of motion information for the current block relative to the reference block (reference picture index, motion vector, etc.). Interpretation includes L0 prediction, L1 prediction, and bi-prediction. L0 prediction is a prediction that uses one reference picture included in the L0 picture list, and L1 prediction means a prediction that uses one reference picture included in the L1 picture list. For this, one set of motion information (e.g., motion vector and reference picture index) is required. In the bi-prediction method, up to two reference regions are used, but these two reference regions may reside in the same reference picture or in different pictures. In other words, in the bi-prediction method, up to two sets of motion information (e.g., motion vector and reference picture index) are used, but the two motion vectors may correspond to the same reference picture index or to different reference picture indices. In this case, the reference picture is displayed (or output) either before or after the current picture in terms of time. In one embodiment, the two reference regions used in the dual prediction method may be regions selected from the L0 picture list and the L1 picture list, respectively.

[0038] The interpretation unit 254 obtains the current reference block using the motion vector and the reference picture index. The reference block resides within the reference picture corresponding to the reference picture index. The sample value of the block identified by the motion vector, or an interpolated value thereof, is used as the predictor for the current block. For motion prediction with sub-pel pixel accuracy, for example, an 8-tab interpolation filter is used for the luminance signal and a 4-tab interpolation filter is used for the chrominance signal. However, the interpolation filter for sub-pel motion prediction is not limited to these. In this way, the interpretation unit 254 performs motion compensation, predicting the texture of the current unit from the previously restored picture. In this process, the interpretation unit utilizes a motion information set.

[0039] In a further embodiment, the prediction unit 250 may include an intra-BC prediction unit (not shown). The intra-BC prediction unit can reconstruct the current region by referring to a specific region containing the reconstructed sample in the current picture. The intra-BC prediction unit obtains intra-BC encoded information for the current region from the entropy decoding unit 210. The intra-BC prediction unit obtains a block vector value of the current region that points to a specific region in the current picture. The intra-BC prediction unit can perform intra-BC prediction using the obtained block vector value. The intra-BC encoded information may include block vector information.

[0040] A video picture is generated by summing the predicted values ​​output from the intra-prediction unit 252 or the inter-prediction unit 254 and the residual values ​​output from the inverse conversion unit 225. In other words, the video signal decoding device 200 restores the current block using the predicted block generated by the prediction unit 250 and the residual obtained from the inverse conversion unit 225.

[0041] On the other hand, the block diagram in Figure 2 shows a decoding device 200 according to one embodiment of the present invention, and the separated blocks show the elements of the decoding device 200 in a logically distinguishable manner. Thus, the elements of the decoding device 200 described above are mounted on one chip or multiple chips depending on the device design. According to one embodiment, the operation of each element of the decoding device 200 described above is performed by a processor (not shown).

[0042] Figure 3 shows an example in which a Coding Tree Unit (CTU) is divided into Coding Units (CUs) within a picture. In the coding process of a video signal, the picture is divided into a sequence of Coding Tree Units (CTUs). A Coding Tree Unit consists of two blocks: an NXN block of luminance samples and its corresponding chrominance samples. A Coding Tree Unit is divided into multiple Coding Units. A Coding Tree Unit may also become a leaf node without being divided. In this case, the Coding Tree Unit itself can become a Coding Unit. A Coding Unit refers to a basic unit for processing a picture in the video signal processing processes described above, i.e., intra / inter prediction, transformation, quantization, and / or entropy coding. Within a single picture, the size and pattern of the Coding Units are not constant. Coding Units have a square or rectangular pattern. A rectangular Coding Unit (or rectangular block) includes vertical Coding Units (or vertical blocks) and horizontal Coding Units (or horizontal blocks). In this 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. Furthermore, in this specification, a non-square block refers to a rectangular block, but the present invention is not limited to this.

[0043] Referring to Figure 3, the coding tree unit is first divided into a quad tree (QT) structure. That is, in the quad tree structure, one node with a size of 2N × 2N is divided into four nodes with a size of N × N. In this specification, the quad tree is also referred to as a quaternary tree. The quad tree division is performed recursively, and it is not necessary for all nodes to be divided to the same depth.

[0044] On the other hand, the leaf nodes of the quad tree described above are further divided into a multi-type tree (MTT) structure. According to embodiments of the present invention, in a multi-type tree structure, one node is divided into a binary or ternary tree structure with horizontal or vertical division. In other words, there are four division structures in a multi-type tree structure: vertical binary division, horizontal binary division, vertical ternary division, and horizontal ternary division. According to embodiments of the present invention, in each of the tree structures, the width and height of the node are both powers of 2. For example, in a binary tree (BT) structure, a node of size 2N×2N is divided into two N×2N nodes by vertical binary division and into two 2N×N nodes by horizontal binary division. Furthermore, in a Ternary Tree (TT) structure, a node of size 2N×2N is divided into (N / 2)×2N, N×2N, and (N / 2)×2N nodes by vertical ternary decomposition, and into 2N×(N / 2), 2N×N, and 2N×(N / 2) nodes by horizontal ternary decomposition. Such multi-type tree decomposition is performed recursively.

[0045] Leaf nodes in a multi-type tree can be coding units. If no splitting is instructed for a coding unit, or if the coding unit is not larger than the maximum transformation length, the coding unit is used as the unit for prediction and transformation without further splitting. On the other hand, in the quad tree and multi-type tree described above, at least one of the following parameters is predefined or transmitted via RBSP of a higher-level set such as PPS, SPS, VPS, etc.: 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) MaxTtSize: the maximum allowed TT root node size, 5) MaxMttDepth: the maximum allowed depth of MTT splitting from the leaf nodes of the QT, 6) MinBtSize: the minimum allowed BT leaf node size, 7) MinTT size: the minimum allowed TT leaf node size.

[0046] Figure 4 illustrates one embodiment of a method for signaling the splitting of quad trees and multi-type trees. The flags previously set to signal the splitting of quad trees and multi-type trees can be used. Referring to Figure 4, at least one of the following can be used: 'qt_split_flag' which indicates whether or not to split a quad tree node, 'mtt_split_flag' which indicates whether or not to split a multi-type tree node, 'mtt_split_vertical_flag' which indicates the splitting direction of a multi-type tree node, or 'mtt_split_binary_flag' which indicates the splitting form of a multi-type tree node.

[0047] According to an embodiment of the present invention, the coding tree unit is the root node of a quad tree and can be divided into a quad tree structure beforehand. In the quad tree structure, each node 'QT_node' is signaled with 'qt_split_flag'. If the value of 'qt_split_flag' is 1, the node is divided into four square nodes, and if the value of 'qt_split_flag' is 0, the node becomes a leaf node 'QT_leaf_node' of the quad tree.

[0048] Each quadtree leaf node 'QT_leaf_node' can be further divided into a multi-type tree structure. In the multi-type tree structure, each node 'MTT_node' is signaled with 'mtt_split_flag'. If the value of 'mtt_split_flag' is 1, the node is divided into multiple rectangular nodes, and if the value of 'mtt_split_flag' is 0, the node becomes a leaf node 'MTT_leaf_node' in the multi-type tree. When a multi-type tree node 'MTT_node' is divided into multiple rectangular nodes (i.e., when the value of 'mtt_split_flag' is 1), additional 'mtt_split_vertical_flag' and 'mtt_split_binary_flag' can be signaled for the node 'MTT_node'. If the value of 'mtt_split_vertical_flag' is 1, the node 'MTT_node' is instructed to be split vertically. If the value of 'mtt_split_vertical_flag' is 0, the node 'MTT_node' is instructed to be split horizontally. Also, if the value of 'mtt_split_binary_flag' is 1, the node 'MTT_node' is split into two rectangular nodes. If the value of 'mtt_split_binary_flag' is 0, the node 'MTT_node' is split into three rectangular nodes.

[0049] Picture prediction (motion compensation) for coding is performed on coding units that cannot be further divided (i.e., leaf nodes in the coding unit tree). The basic unit for performing such predictions is referred to below as a prediction unit or prediction block.

[0050] Hereinafter, the term "unit" as used herein is used as a substitute for the prediction unit, which is the basic unit for making predictions. However, the present invention is not limited thereto and is understood in a broader sense as a concept that includes the coding unit.

[0051] Figures 5 and 6 illustrate in more detail the intra-prediction method according to an embodiment of the present invention. As described above, the intra-prediction unit predicts the sample value of the current block by using the restored sample located to the left and / or above the current block as a reference sample.

[0052] First, Figure 5 shows an example of a reference sample used to predict the current block in intra-prediction mode. In this example, the reference sample is a sample adjacent to the left boundary and / or the upper boundary of the current block. As shown in Figure 5, if the size of the current block is W×H and a single reference line sample adjacent to the current block is used for intra-prediction, the reference sample is set using up to 2W+2H+1 peripheral samples located to the left and / or above the current block.

[0053] Furthermore, if at least some of the samples to be used as reference samples have not yet been recovered, the intra-prediction unit performs a reference sample padding process to acquire reference samples. The intra-prediction unit also performs a reference sample filtering process to reduce the error of the intra-prediction. That is, it filters the peripheral samples and / or the reference samples acquired by the reference sample padding process to acquire filtered reference samples. The intra-prediction unit uses the reference samples thus acquired to predict the samples of the current block. The intra-prediction unit predicts the samples of the current block using either the unfiltered or filtered reference samples. In this disclosure, peripheral samples may include samples on at least one reference line. For example, peripheral samples may include adjacent samples on lines adjacent to the boundary of the current block.

[0054] Next, Figure 6 illustrates one embodiment of a prediction mode used for intra-prediction. For intra-prediction, intra-prediction mode information indicating the direction of intra-prediction can be signaled. The intra-prediction mode information indicates one of several intra-prediction modes that constitute an intra-prediction mode set. If the current block is an intra-predicted block, the decoder receives the intra-prediction mode information for the current block from the bitstream. The intra-prediction unit of the decoder performs intra-prediction for the current block based on the extracted intra-prediction mode information.

[0055] According to an embodiment of the present invention, the intra-prediction mode set includes all intra-prediction modes used for intra-prediction (e.g., a total of 67 intra-prediction modes). More specifically, the intra-prediction mode set includes planar modes, DC modes, and a plurality of (e.g., 65) angular modes (i.e., direction modes). Each intra-prediction mode is indicated by a preset index (i.e., an intra-prediction mode index). For example, as shown in Figure 6, intra-prediction mode index 0 indicates the planar mode, and intra-prediction mode index 1 indicates the DC mode. Intra-prediction mode indices 2 through 66 each indicate different angular modes. Each angular mode indicates a different angle within a pre-set angular range. For example, an angular mode can indicate an angle within an angular range of 45° to -135° in a clockwise direction (i.e., a first angular range). The angular modes may be defined relative to the 12 o'clock direction. In this case, 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.

[0056] The interpretation method according to an embodiment of the present invention will be described below with reference to Figure 7. In the present invention, the interpretation method can include a general interpretation method optimized for translation motion and an affine model-based interpretation method. Furthermore, the motion vector can typically include at least one of a general motion vector for motion compensation and a control point motion vector for affine motion compensation, based on the interpretation method.

[0057] Figure 7 illustrates an interpretation method according to one embodiment of the present invention. As previously described, the decoder can predict the current block by referring to a restored sample of another decoded picture. Referring to Figure 7, the decoder obtains a reference block 702 in reference picture 720 based on a motion information set of the current block 701. The motion information set may include a reference picture index and a motion vector 703. The reference picture index points to a reference picture 720 containing a reference block for interpretation of the current block in a reference picture list. According to one embodiment, the reference picture list may include at least one of the L0 picture list or L1 picture list described above. The motion vector indicates the offset between the coordinate values ​​of the current block 701 in the current picture 710 and the coordinate values ​​of the reference block 702 in reference picture 720. The decoder obtains a predictor of the current block 701 based on the sample values ​​of the reference block 702 and uses the predictor to restore the current block 701.

[0058] Specifically, the encoder can find a reference block by searching for a block similar to the current block using the picture with the earliest restoration order. For example, the encoder can search for a reference block within a pre-configured search area that minimizes the sum of the differences between the current block and the sample values. In this process, at least one of either SAD (Sum of Absolute Difference) or SATD (Sum of Hadamard Transformed Difference) can be used to measure the similarity between the samples in the current block and the reference block. Here, SAD can be the sum of all the absolute values ​​of the differences between the sample values ​​contained in the two blocks. SATD can be the sum of all the absolute values ​​of the Hadamard Transform coefficients obtained by performing a Hadamard Transform on the differences between the sample values ​​contained in the two blocks.

[0059] On the other hand, the current block can also be predicted using one or more reference regions. As mentioned above, the current block can be interpreted using a biprediction scheme with two or more reference regions. According to one embodiment, the decoder can acquire two reference blocks based on two motion information sets of the current block. The decoder can also acquire a first predictor and a second predictor of the current block based on the sample values ​​of each of the two acquired reference blocks. The decoder can then reconstruct the current block using the first and second predictors. For example, the decoder can reconstruct the current block based on the sample-by-sample average of the first and second predictors.

[0060] As mentioned above, one or more motion information sets can signal for motion compensation of the current block. In this case, the similarity between the motion information sets for each of the multiple blocks' motion compensations can be utilized. For example, the motion information set used for predicting the current block can be derived from the motion information set used for predicting any one of the other samples that have already been restored. Through this, the encoder and decoder can reduce signaling overhead. Various embodiments in which the motion information set of the current block is signaled will be described below.

[0061] For example, there may be multiple candidate blocks that could have been predicted based on motion information sets identical or similar to the motion information set of the current block. The decoder can generate a merge candidate list based on these multiple candidate blocks. Here, the merge candidate list may include candidates corresponding to samples that were restored before the current block and could have been predicted based on motion information sets associated with the motion information set of the current block. The encoder and decoder can construct the merge candidate list of the current block based on predefined rules. In this case, the merge candidate lists constructed by the encoder and decoder may be identical to each other. For example, the encoder and decoder can construct the merge candidate list of the current block based on the position of the current block in the current picture. The method by which the encoder and decoder construct the merge candidate list of the current block will be described later in Figure 9. In this disclosure, the position of a particular block represents the relative position of the top-left sample of the particular block in the picture containing the particular block.

[0062] On the other hand, to improve coding efficiency, instead of directly coding the residual signal as described above, a method can be used in which the transformed residual signal is converted, the resulting conversion coefficient value is quantized, and the quantized conversion coefficient is coded. As mentioned above, the conversion unit can convert the residual signal to obtain the conversion coefficient value. In this case, the residual signal of a particular block may be distributed throughout the entire area of ​​the current block. This allows for the concentration of energy in the low-frequency region using frequency domain conversion on the residual signal, thereby improving coding efficiency. The following describes in detail how the residual signal is converted or inversely converted.

[0063] Figure 8 is a diagram illustrating how the encoder converts a resistive signal. As previously mentioned, the resistive signal in the spatial domain may be converted to the frequency domain. The encoder can convert the acquired resistive signal to obtain conversion coefficients. First, the encoder can acquire at least one resistive block containing the resistive signal for the current block. The resistive block may be either the current block or a block divided from the current block. In this disclosure, a resistive block may be referred to as a resistive array or resistive matrix containing resistive samples of the current block. Also in this disclosure, a resistive block represents a block the same size as the conversion unit or conversion block.

[0064] Next, the encoder can transform the residual block using a transformation kernel. The transformation kernel used for the transformation of the residual block may be a transformation kernel having separable characteristics for vertical and horizontal transformations. In this case, the transformation of the residual block may be performed separately as a vertical and horizontal transformation. For example, the encoder can perform a vertical transformation by applying the transformation kernel to the vertical direction of the residual block. The encoder can also perform a horizontal transformation by applying the transformation kernel to the horizontal direction of the residual block. In this disclosure, the term "transformation kernel" may be used to represent a set of parameters used for the transformation of a residual signal, such as a transformation matrix, transformation array, transformation function, or transformation. In one embodiment, the transformation kernel may be one of several available kernels. Furthermore, different transformation types based on transformation kernels may be used for the vertical and horizontal transformations, respectively. A method for selecting one of several available transformation kernels will be described later in Figures 12 to 26.

[0065] The encoder can quantize a transformed block obtained from a residual block by transmitting it to a quantization unit. The transformed block may contain multiple transformation coefficients. Specifically, the transformed block may consist of multiple transformation coefficients arranged in a two-dimensional array. The size of the transformed block may be the same as that of the residual block, either the current block or a block divided from the current block. The transformation coefficients transmitted to the quantization unit may be represented by their quantized values.

[0066] Furthermore, the encoder can perform additional transformations before the transformation coefficients are quantized. As shown in Figure 8, the transformation method described above can be called a primary transform, and the additional transformation can be called a secondary transform. The secondary transform may be selective for each resistive block. In one embodiment, the encoder can improve coding efficiency by performing a secondary transform on regions where it is difficult to concentrate energy in the low-frequency region with only a primary transform. For example, a secondary transform may be added to blocks where the resistive value appears large in directions other than the horizontal or vertical direction of the resistive block. The resistive value of an intra-predicted block may have a higher probability of changing in directions other than the horizontal or vertical direction compared to the resistive value of an inter-predicted block. This allows the encoder to perform a further secondary transform on the resistive signal of an intra-predicted block. Alternatively, the encoder may omit the secondary transform on the resistive signal of an inter-predicted block.

[0067] As another example, the size of the current block or residual block may determine whether or not a quadratic transformation is performed. Also, differently sized transformation kernels may be used depending on the size of the current block or residual block. For example, an 8x8 quadratic transformation may be applied to blocks where the length of the shorter side of the width or height is greater than or equal to a first preset length. Also, a 4x4 quadratic transformation may be applied to blocks where the length of the shorter side of the width or height is greater than or equal to a second preset length, and less than the first preset length. In this case, the first preset length may be greater than the second preset length, but this disclosure is not limited thereto. Furthermore, unlike a linear transformation, a quadratic transformation does not have to be performed in separate vertical and horizontal transformations. Such a quadratic transformation can be called a Low Frequency Non-Separable Transform (LFNST).

[0068] Furthermore, in the case of video signals in a specific region, abrupt brightness changes may prevent the reduction of high-frequency bandwidth energy even after frequency conversion. This can lead to a decrease in compression performance due to quantization. Also, when performing conversion on a region where residual values ​​rarely exist, encoding and decoding times may increase unnecessarily. For this reason, conversion of residual signals in a specific region may be omitted. Whether or not to perform conversion on residual signals in a specific region may be determined by a syntax element associated with the conversion of that region. For example, the syntax element may include transform skip information. Transform skip information may be a transform skip flag. If the transform skip information for a residual block indicates a transform skip, the conversion of that residual block is not performed. In this case, the encoder can immediately quantize the residual signal in that region that is not converted. The operation of the encoder described with reference to Figure 8 can be performed by the conversion unit in Figure 1.

[0069] The aforementioned conversion-related syntax elements may be information parsed from the video signal bitstream. A decoder can obtain the conversion-related syntax elements by entropy decoding the video signal bitstream. An encoder can generate the video signal bitstream by entropy coding the conversion-related syntax elements.

[0070] Figure 9 is a diagram illustrating in detail how an encoder and decoder obtain a residual signal by inversely transforming the conversion coefficients. For the sake of explanation, it will be assumed that the inverse transformation operation is performed in each inverse transformation section of the encoder and decoder. The inverse transformation section can obtain a residual signal by inversely transforming the inversely quantized conversion coefficients. First, the inverse transformation section can detect whether or not an inverse transformation is performed for a particular region from the conversion-related syntax elements of that region. In one embodiment, if the conversion-related syntax elements for a particular conversion block indicate a conversion skip, the transformation for that conversion block may be omitted. In this case, the aforementioned first-order and second-order inverse transformations may all be omitted for the conversion block. Furthermore, the inversely quantized conversion coefficients may be used as a residual signal. For example, the decoder can use the inversely quantized conversion coefficients as a residual signal to reconstruct the current block.

[0071] In other embodiments, the transformation-related syntax elements for a particular transformation block do not necessarily have to represent a transformation skip. In this case, the inverse transformation unit can decide whether or not to perform a quadratic inverse transformation on a quadratic transformation. For example, if the transformation block is a transformation block of an intra-predicted block, a quadratic inverse transformation may be performed on the transformation block. Alternatively, the quadratic transformation kernel used for the transformation block may be determined based on the intra-prediction mode corresponding to the transformation block. As another example, the decision to perform a quadratic inverse transformation may be made based on the size of the transformation block. The quadratic inverse transformation may be performed after the inverse quantization process and before the linear inverse transformation is performed.

[0072] The inverse transformer can perform a linear inverse transform on the inversely quantized transform coefficients or the quadratic inversely transformed transform coefficients. In the case of a linear inverse transform, it may be separated into a vertical transform and a horizontal transform, similar to the linear transform. For example, the inverse transformer can obtain a residual block by performing a vertical inverse transform and a horizontal inverse transform on the transform block. The inverse transformer can inverse the transform block based on the transform kernel used to transform the transform block. For example, the encoder can explicitly or implicitly signal information indicating which transform kernel is currently applied to the transform block from among several available transform kernels. The decoder can use the signaled transform kernel information to select the transform kernel to be used for the inverse transform of the transform block from among several available transform kernels. The inverse transformer can reconstruct the current block using the residual signal obtained by the inverse transform on the transform coefficients.

[0073] Figure 10 is a diagram illustrating how to apply the intra-prediction mode when a coding block according to one embodiment of the present invention is divided into a plurality of conversion blocks. According to one embodiment of the present invention, the intra-prediction mode may be determined on a coding unit (or coding block) basis (hereinafter, it may be abbreviated as "block"). The coding unit may be divided into a plurality of conversion blocks. In one embodiment, the intra-prediction mode may be modified (or analyzed, determined, and improved) based on the configuration of the coding block.

[0074] In one embodiment, a method for reanalyzing the intra prediction mode when the block is not a square (or regular quadrilateral) will be described. Referring to Figure 10, nTbW may be a variable indicating the width of the transformation block and nTbH may be a variable indicating the height of the transformation block. Alternatively, nTbW may be a variable indicating the width of the coding block and nTbH may be a variable indicating the height of the coding block. Alternatively, in a block to which ISP (Intra subpartitions) is applied, nTbW may be a variable indicating the width of the coding block and nTbH may be a variable indicating the height of the coding block. Furthermore, in this invention, whRatio is a variable indicating the ratio of width to height. As an example, whRatio may be set (or defined) as Abs(Log2(nTbW / nTbH)). Hereinafter, the intra-prediction mode signaled from the encoder to the decoder will be referred to as the first prediction mode (or first intra-prediction mode), and the modified (or re-analyzed, determined, improved) mode may be referred to as the second prediction mode (or second intra-prediction mode). In the following, abs() represents an operator (or function) that takes the absolute value. The modified intra-prediction mode may be derived based on the following conditions.

[0075] - First condition: nTbW > nTbH

[0076] - Second condition: Is the first prediction mode greater than or equal to 2?

[0077] - Third condition: If the first prediction mode is whRatio > 1, it is less than (8 + 2 * whRatio), and if whRatio < 1, it is less than 8.

[0078] When the decoder satisfies the three conditions described above (the first to the third conditions), it can set wideAngle to 1 and the second prediction mode to (first prediction mode + 65). Here, wideAngle is a variable that indicates whether or not the wide-angle mode is used.

[0079] - Fourth condition: nTbH > nTbW

[0080] - Fifth condition: Is the first prediction mode less than or equal to 66?

[0081] - Sixth condition: If the first prediction mode is whRatio > 1, it is greater than (60 - 2 * whRatio), and if whRatio < 1, it is greater than 60.

[0082] If all of the above conditions 4 through 6 are met, the decoder can set the variable wideAngle to 1 and set the second prediction mode to (first prediction mode - 67).

[0083] According to one embodiment of the present invention, the intra-prediction mode can be distinguished into a basic angle mode and an extended angle mode. The basic angle mode may be an angle mode within a range of ±45° relative to the vertical mode / horizontal mode, and the extended angle mode may be an angle mode exceeding ±45° relative to the vertical mode / horizontal mode. Therefore, the signaled mode information may use either the basic angle mode or the extended angle mode depending on the form of the coding block. The number of usable modes in the extended angle mode may be defined by the ratio of width to height (or the ratio of height to width) based on the form of the coding block. As an example, the ratio may be defined (or set) as 2:1, 4:1, 8:1, 16:1, etc.

[0084] For example, as shown in Figure 10(a), a cbWidth × cbHeight coding block determined as intra-prediction mode 2 may be divided into two horizontal transformation blocks, as shown in Figure 10(b). Assuming that tbWidth_1 is greater than tbHeight_1, the first transformation block having a size of tbWidth_1 × tbHeight_1 can have a vertical rectangular block shape. Here, cbWidth is a variable indicating the width of the coding block, and cbHeight is a variable indicating the height of the coding block.

[0085] In this case, the signaled intra-prediction mode 2 may be re-analyzed based on the configuration of the first transformation block and modified into an extended angular mode, which becomes (2+65) by the analysis method described above, and the second prediction mode may be derived (or determined) as 67. That is, the intra-prediction mode determined at the coding block level does not have to be used identically at the transformation block level. In this case, a change in performance may occur.

[0086] Therefore, according to an embodiment of the present invention, we propose the following method for determining the wide-angle mode in order to apply the intra-prediction mode determined for the coding block to the conversion block as well. In an embodiment, when the encoder / decoder derives the second prediction mode, nTbW and nTbH can be set to the cbWidth and cbHeight of the coding block. The encoder / decoder can then determine (or decide) whether or not to use the wide-angle mode using the height and width of the coding block containing the conversion block. Figure 10 shows the case where the conversion block is divided into a horizontal rectangular shape, but the present invention is not limited thereto. That is, the proposed embodiment may be similarly applied when the block is divided into a vertical rectangle, a square, or various combined shapes.

[0087] Figure 11 is a diagram illustrating a method for applying PDPC (position-dependent intraprediction combination) according to one embodiment of the present invention. PDPC may be applied to intrablocks when all of the following conditions are met.

[0088] Condition 1. IntraSubPartitionsSplitType (ISP splitting type) is either ISP_NO_SPLIT or cIdx (component index) is not equal to 0.

[0089] Condition 2. refIdx (reference sample line index) is equal to 0, or cIdx is not equal to 0.

[0090] Condition 3. If any one of the following conditions is met:

[0091] - predModeIntra (Intra prediction mode) is INTRA_PLANAR

[0092] - predModeIntra (Intra Prediction Mode) is INTRA_DC

[0093] - predModeIntra (Intra Prediction Mode) is INTRA_ANGULAR18

[0094] - predModeIntra (Intra prediction mode) is INTRA_ANGULAR50

[0095] - If predModeIntra (intra prediction mode) is less than or equal to INTRA_ANGULAR10

[0096] - If predModeIntra (intra prediction mode) is equal to or greater than INTRA_ANGULAR58

[0097] According to one embodiment of the present invention, the PDPC operation may be applied by the method described below. The PDPC described in the present invention is not limited to its name and may also be called position-dependent intra prediction sample filtering.

[0098] As one embodiment, the predicted sample pred(x,y) at position (x,y) may be predicted using a linear combination of an intra-prediction mode (e.g., DC, planar, directional mode) and a reference sample by PDPC, as shown in Equation 1 below.

[0099] [Mathematics 1] pred(x,y) = ( wL × R -1,y + wT × Rx,-1 - wTL × R -1,-1 + (64 - wL - wT + wTL) × pred(x,y) + 32 ) >> 6

[0100] Here, R x,-1 and R -1,y These represent the reference samples currently located to the left and above the sample (x,y), respectively, and R -1,-1 This represents the reference sample currently located at the top-left corner of the block. If DC mode is applied to the current block, the weighted value (also called the PDPC weighted value) may be calculated based on the following equation 2.

[0101] [Math 2] wT = 32 >> ( ( y<<1 ) >> shift ), wL = 32 >> ( ( x<<1 ) >> shift ), wTL = ( wL>>4 ) + ( wT>>4 )

[0102] In Equation 2, shift may be set to (log2(width)-2+log2(height)-2+2)>>2. Then, wTL may be set to 0 for planar mode, wTL may be set to wT for horizontal mode, and wTL may be set to wL for vertical mode. The PDPC weighted value may be calculated based only on summation and shift operations. The pred(x,y) value may be calculated in a single step using Equation 1 described above.

[0103] If PDPC is applied to DC, planar, horizontal, and / or vertical modes, additional boundary filtering may not be required. For example, this additional boundary filtering could include DC mode boundary filters or horizontal / vertical mode edge filters from conventional video compression technologies (e.g., HEVC).

[0104] FIG. 12 is a diagram illustrating reference samples used for PDPC in an intra prediction mode as an example of an embodiment of the present invention. Referring to FIG. 12, (a) of FIG. 12 assumes that the intra prediction mode is prediction mode 2, and (b) of FIG. 12 assumes that the intra prediction mode is prediction mode 66. Specifically, FIG. 12 shows reference samples R x,-1 , R -1,y and R -1,-1 when PDPC is applied to the top - right diagonal mode. The prediction sample pred(x’, y’) represents the prediction sample located at (x’, y’) within the prediction block. The x - coordinate of the reference sample R x,-1 is given by x = x’ + y’ + 1. And the y - coordinate of the reference sample R -1,y is similarly given by y = x’ + y’ + 1.

[0105] According to an embodiment of the present invention, the PDPC weight value for the top - right diagonal mode may be determined by the following Equation 3.

[0106] [Equation 3] wT = 16 >> ( ( y’<<1 ) >> shift ), wL = 16 >> ( ( x’<<1 ) >> shift ), wTL = 0

[0107] FIG. 13 is a diagram illustrating reference samples used for PDPC in an intra prediction mode as an example of an embodiment of the present invention. Referring to FIG. 13, (a) of FIG. 13 assumes that the mode number (or mode index) of the intra prediction mode is any one of 3 to 10, and (b) of FIG. 13 assumes that the mode number of the intra prediction mode is any one of 58 to 65. Similar to FIG. 12 described above, FIG. 13 shows reference samples R x,-1 , R -1,y and R -1,-1This shows that the predicted sample pred(x',y') represents the predicted sample located within the prediction block (x',y'). Reference sample R x,-1 The coordinate x is given as x = x' + y' + 1. And, see the reference sample R. -1,y The coordinate y is similarly given as y = x' + y' + 1.

[0108] According to one embodiment of the present invention, the PDPC weighting value for the lower left diagonal mode may be determined by the following equation 4.

[0109] [Math 4] wT = 16 >> ( ( y'<<1 ) >> shift ), wL = 16 >> ( ( x'<<1 ) >> shift ), wTL = 0

[0110] For the upper right diagonal mode, in the case of Figure 13(a), the PDPC weighting value may be defined as shown in Equation 5 below.

[0111] [Number 5] wT = 32 >> ( ( y'<<1 ) >> shift ), wL = 0, wTL = 0

[0112] Similarly, in the case of Figure 13(b) for the lower left diagonal mode, the PDPC weighting value may be defined as shown in Equation 6 below.

[0113] [Number 6] wL = 32 >> ( ( x'<<1 ) >> shift ), wT =0, wTL = 0

[0114] Referring to Figures 12 and 13, in an embodiment, as in the case where PDPC is applied to DC, planar, horizontal and / or vertical modes, additional boundary filtering is not required for the diagonal mode and the adjacent modes of the diagonal mode shown in Figure 13.

[0115] The example reference sample coordinates shown in Figure 13 may be derived based on a table defined for directional mode intra-prediction. As mentioned above, the table may be defined as the diagonal and its adjacent modes, which has the advantage that no additional table is required for the PDPC implementation described in this invention. Also, multiplication operations may not be used when calculating the coordinates x and y. Furthermore, in one embodiment, when fractional reference sample coordinates are used, linear interpolation may be performed on the reference sample.

[0116] Figure 14 illustrates an example of how to apply ISP (Intra subpartitions) and PDPC (position-dependent intra prediction combination) to a coding block according to one embodiment to which the present invention is applied. Referring to Figure 14(a), the current coding block may be expressed as W×H using width W and height H. Figure 14(b) shows an example in which the current coding block is divided vertically into four transformation blocks when the ISP mode is applied. Figure 14(c) shows an example in which PDPC is applied to each of the transformation blocks divided in Figure 14(b).

[0117] In one embodiment, the encoder / decoder can use (or apply) an interpolation filter in each conversion block to which ISP is applied, as shown in Figure 14(b). The interpolation filter represents a method for obtaining a sample value from a reference sample. For example, the encoder / decoder can use cubic interpolation filter coefficients if the filter flag is 0, and Gaussian interpolation filter coefficients if it is 1. The encoder / decoder can determine the reference sample value using the determined interpolation filter coefficients and use this value as a predicted value. In another embodiment, the encoder / decoder can set the filter flag to 1 for blocks to which ISP is applied, where the conversion block is a Luma component. As another example, the encoder / decoder can also decide whether or not to apply an interpolation filter based on the filter flag.

[0118] In one embodiment, the encoder / decoder is a Luma component and can set (or determine) a filter flag value for a transformed block to which ISP is applied, based on the block width W and height H. In one embodiment, the encoder / decoder can set the flag value by comparing the number of block samples W*H with a predefined (or pre-set) specific reference value. For example, the encoder / decoder can compare W*H>reference value, W*H>=reference value, W*H<reference value, and W*H<=reference value. Alternatively, the encoder / decoder can set different filter flag values ​​by comparing the block width and height with reference values, respectively. In one embodiment, the conditions for determining the filter flag value may be defined as (W>reference value and H>reference value), (W>reference value or H>reference value). In the above example, the inequality is not limited to being greater than the reference value, but may be defined as being equal, greater or equal, less, or less or equal. The reference values ​​applied to W and H may be different from each other, and different inequality signs may be applied to each other. Alternatively, the filter flag value may be set based on whether or not it falls within a specific block size range.

[0119] Referring to Figure 14(c), in one embodiment of the present invention, the encoder / decoder can apply PDPC to a block to which ISP is applied. For example, the encoder / decoder can determine whether or not to apply PDPC to a block to which ISP is applied based on the number of samples in the block W*H. In one embodiment, conditions for determining whether or not to apply PDPC based on the number of samples in the block may be defined. For example, the conditions may be W*H>reference value, W*H>=reference value, W*H<reference value, W*H<=reference value, etc. The reference value may be a preset value. In another embodiment, the conditions for determining whether or not to apply PDPC may be defined as (W>reference value and H>reference value) or (W>reference value or H>reference value). In this example, the inequality is not limited to being greater than the reference value, but may be defined as being equal to, greater or equal, less than, or less or equal. For example, the conditions for determining whether or not PDPC applies may be defined as (W ≥ reference value and H ≥ reference value) or (W ≥ reference value or H ≥ reference value). In practice, the reference values ​​applied to W and H may be defined as the same value, different values, the same sign (or inequality sign), or different signs.

[0120] Furthermore, referring to Figure 14(c), in one embodiment of the present invention, the block to which ISP is applied may be divided into a plurality of rectangular transformation blocks, and the encoding / decoding process may be carried out on a unit basis of the divided transformation blocks. In one embodiment, when the encoder / decoder applies PDPC, it may also apply it on a unit basis of coding blocks instead of a unit basis of transformation blocks. That is, the encoder / decoder can perform PDPC on the coding block to which ISP is applied on a unit basis of coding blocks instead of a unit basis of transformation blocks.

[0121] Referring to Figure 14(c), in one embodiment of the present invention, when PDPC is applied to a block to which ISP is applied, the encoder / decoder can apply PDPC only if certain conditions defined for some of the modes to which PDPC is applied are met. For example, when determining whether or not to apply PDPC based on the number of samples or width / height, as in the embodiment described above, the reference values ​​for planar mode, horizontal mode, and vertical mode may be set to be different.

[0122] Furthermore, according to one embodiment of the present invention, when determining whether or not reference sample filtering is applied, the encoder / decoder can set a filter flag indicating whether or not filtering is applied based on whether or not ISP and / or PDPC is applied to the block. For example, for blocks to which ISP and PDPC are applied, the filter flag may be set to a fixed value of 0 or 1. Alternatively, for blocks to which ISP and PDPC are applied, the filter flag value may be determined by the MDIS (Mode dependent Intra smoothing) condition. Alternatively, the encoder / decoder can apply different filter flag values ​​for blocks to which ISP and PDPC are applied and for blocks to which only ISP is applied.

[0123] Furthermore, according to one embodiment of the present invention, when determining the wide-angle mode, the encoder / decoder can reset the intra-prediction mode based on the width and height of the coding block. For example, the encoder / decoder can perform a wide-angle mode reanalysis process based on the width and height of the coding block for the block to which ISP is applied, and set a reference sample filter flag based on this. Alternatively, the encoder / decoder can individually set the wide-angle mode application method based on the division direction / size of the block to which ISP is applied. In one embodiment, a specific division direction can be applied based on the width / height of the conversion block or the width / height of the coding block, and otherwise, it can be applied in another manner. In another embodiment, the encoder / decoder can apply the wide-angle mode based on the width and height values ​​of the divided conversion block. For example, if the minimum value of the width and height of the conversion block is greater than, equal to, or greater than a reference value, the wide-angle mode can be applied using the height and width of the coding block; if it is equal to, less than, or less than the reference value, the wide-angle mode can be applied using the width and height of the conversion block. Alternatively, conversely, if the minimum of the width and height of the transformation block is greater than, equal to, or greater than the reference value, the wide-angle mode can be applied using the height and width of the transformation block; if it is equal to, less than, or less than the reference value, the wide-angle mode can be applied using the width and height of the coding block.

[0124] The embodiments described above in Figures 10 to 14 may be applied in combination of one or more embodiments, or they may be applied independently. Furthermore, the embodiments described above may be applied in substantially the same manner to the decoder and encoder.

[0125] Figure 15 is a diagram illustrating a conversion unit division processing method according to one embodiment of the present invention. Referring to Figure 15, in one embodiment of the present invention, the encoder / decoder can encode / decode the current block (coding block, coding unit) by dividing it into multiple conversion blocks. As an example, when intra subpartitions (ISP) mode is applied, the coding block may be divided into multiple conversion blocks. Alternatively, if the size of the coding block is larger than the maximum conversion size, the coding block may be divided into multiple conversion blocks. When intra subpartition mode is applied, as shown in Figure 15, the coding block may be divided into horizontal or vertical rectangular conversion blocks, and may be divided into two or four conversion blocks.

[0126] Figure 16 shows the encoding / decoding process via primary and secondary transforms according to one embodiment to which the present invention is applied. As mentioned above, a coding block may be divided into multiple transformation blocks, and the encoder / decoder can apply transformations to the divided transformation blocks. Figure 16 shows an example in which two transformations are applied to a transformation block. The forward primary transform in Figure 16 is the first transformation applied with respect to the encoder side, and may be called a primary transform in the present invention. The forward secondary transform in Figure 16 is the second transformation applied with respect to the encoder side, and may be called a secondary transform in the present invention. A secondary transform (i.e., an inverse quadratic transform) and a primary transform (i.e., an inverse primary transform) may be performed sequentially on the inversely quantized transformation block with respect to the decoder side. As mentioned above, the secondary transform may be called a low-frequency non-separable transform (LFNST).

[0127] In one embodiment of the present invention, the transformation matrix (or transformation kernel, transformation type) used for the first-order transformation may be a known transformation matrix in conventional video compression technologies such as DCT-2, DST-7, and DCT-8. The second-order transformation may be applied to a portion of the transformation block depending on the size of the coding block. For example, the portion may be a 4x4 region or an 8x8 region. The location of the portion may be the upper left region of the coding block (or transformation block). In one embodiment, if both the width and height of the coding block are greater than 4, it may be applied to the upper left 8x8 region, and if either the width or height is equal to 4, it may be applied to the upper left 4x4 region. The second-order transformation may be applied to the lumen and chroma components of the intra-mode coded block.

[0128] Figure 17 is a diagram illustrating a method for selecting a conversion kernel used in a quadratic conversion according to one embodiment of the present invention. Referring to Figure 17, a set of conversion kernels (or a set of conversion types, a set of conversion matrices) may be determined based on the prediction mode used for intra-prediction, and the table shown in Figure 17 may be defined in the encoder / decoder. In this embodiment, intra-prediction modes may be defined from -14 to 83. As shown in Figure 17, a set of conversion kernels may be determined for each grouped intra-prediction mode. The same index may be applied to the lumen component and the chroma component. Since the set of quadratic conversion kernels is determined based on the intra-prediction mode, the set of conversion kernels can be determined after obtaining (or determining) the intra-prediction mode. This results in a dependency problem. Therefore, in one embodiment of the present invention, a method for eliminating such dependencies will be described.

[0129] As an example, an encoder / decoder can determine the set of transformation kernels to apply to the current block by an intra-predictive mode, taking the following into consideration:

[0130] - CU width-to-height ratio or height-to-width ratio

[0131] - CU size

[0132] - Types of linear transformations

[0133] - MTS Index

[0134] - Whether implicit MTS applies or not

[0135] The encoder / decoder can determine the conversion kernel set based on the above-mentioned factors, and these factors may be used individually or in combination to determine the conversion kernel set.

[0136] Figure 18 illustrates a method for applying a secondary transformation to a transformation block according to one embodiment of the present invention. According to one embodiment of the present invention, an encoder / decoder can divide a coding block (or coding unit) into a plurality of transformation blocks (or transformation units) and apply a secondary transformation to each transformation block. A secondary transformation can be applied to each of the transformation blocks divided from a single coding unit. The size of each transformation block is determined based on the method of division of the coding unit. The size of each transformation block in a coding unit to which ISP is applied may be determined by vertical or horizontal division, as shown in Figure 15, and may further be determined by the number of divisions. The number of divisions in a block to which ISP is applied may be 2 or 4. Figure 18 illustrates a case where a single coding unit is divided vertically as a block to which ISP is applied, and the number of divisions is 4. As shown in Figure 14(b) above, if the size of the coding unit is W × H, the size of each transformation block may be W / 4 × H. The size of the transformation block may be used as the width and height to determine whether or not a secondary transformation is applied.

[0137] According to one embodiment of the present invention, the encoder / decoder can use either the same set of conversion kernels for each conversion block or different sets of conversion kernels. Divided conversion blocks can use the same conversion kernel if the intra-prediction mode and the size of the divided block are the same. Conversely, the encoder / decoder can determine and use a kernel set for each conversion block. In a coding unit to which the intra-subpartition mode is applied, the lumar component is converted into multiple conversion blocks, but the chroma component does not need to be divided. In this case, both the lumar conversion block and the chroma conversion block can use the same secondary conversion kernel set, provided that the size of the coding block to which the secondary conversion block is applied satisfies this requirement. Also, the conversion block sizes of lumar and chroma may be different. In this case, the encoder / decoder can be applied to a 4x4 or 8x8 region according to the block size requirements to which the secondary conversion block is applied. Alternatively, the encoder / decoder can use the same region for chroma as it was for lumar conversion. Since the intra-prediction modes of lumar and chroma may be different, the encoder / decoder can use different sets of conversion kernels for each. Although this method was described as determining the intra-predictive mode-based kernel set, any method for determining the quadratic transformation kernel set, as described in Figure 17, may be applied.

[0138] According to one embodiment of the present invention, if the size of a coding unit is larger than the maximum transformation size, the coding unit may be divided into multiple transformation blocks without further signaling. In this case, applying a quadratic transformation may result in reduced performance and increased complexity, and the maximum coding block to which the quadratic transformation is applied can be limited. The size of the maximum coding block may be the same as the maximum transformation size. Alternatively, a preset coding block size can be used. The preset values ​​may be, but are not limited to, 64, 32, or 16. It may be the length of the longer side, a value, or the total number of samples.

[0139] Furthermore, in one embodiment, the encoder / decoder may define the size of the secondary conversion block not as limited to the 4x4 or 8x8 region at the upper left of the coding unit, but as 2x8, 8x2, 4x16, 16x4, 2x32, or 32x2. The encoder / decoder can determine the region to which the secondary conversion is applied adaptively / without signaling by considering the width-to-height ratio / height-to-width ratio of the coding block.

[0140] Figure 19 shows a method for applying PDPC to a currently coded block to which an intra-prediction mode according to one embodiment to which the present invention is applied is applied. According to one embodiment of the present invention, if the currently coded block is not a square block, the encoder / decoder can perform prediction using only the reference samples on the longer side in the DC mode of the intra-prediction mode. In this case, the sample values ​​on the shorter side do not need to be reflected in the prediction of the currently coded block at all. In this case, the difference between the predicted value of the currently coded block and the reference samples on the shorter side may become large. For this reason, the encoder / decoder may perform sample position-based filtering when performing intra-prediction. As mentioned above, in the present invention, such a sample position-based filtering method can be called PDPC. When PDPC is applied, the encoder / decoder can perform weighted filtering using the first reference sample, the second reference sample, and the reference sample value adjacent to the upper left corner in DC mode. At this time, the reference samples and / or the weighted values ​​applied to each reference sample can be derived using the following equations 7 to 12.

[0141] [Number 7] refL[ x ][ y ] = p[ -1 ][ y ]

[0142] [Number 8] refT[ x ][ y ] = p[ x ][ -1 ]

[0143] [Number 9] wT[ y ] = 32 >> ( ( y << 1 ) >> nScale )

[0144] [Number 10] wL[ x ] = 32 >> ( ( x << 1 ) >> nScale )

[0145] [Number 11] wTL[ x ][ y ] = ( predModeIntra = = INTRA_DC ) ? ( ( wL[ x ] >> 4 ) + ( wT[ y ] >> 4 ) ) : 0

[0146] [Number 12] predSamples[ x ][ y ] = clip1Cmp( ( refL[ x ][ y ] * wL[ x ] + refT[ x ][ y ] * wT[ y ] - p[ -1 ][ -1 ] * wTL[ x ][ y ] + ( 64 - wL[ x ] - wT[ y ] + wTL[ x ][ y ] ) * predSamples[ x ][ y ] + 32 ) >>6 )

[0147] Specifically, the left-side reference sample can be derived using Equation 7, and the right-side reference sample can be derived using Equation 8. The weight applied to the right-side reference sample can be derived using Equation 9, the weight applied to the left-side reference sample can be derived using Equation 10, and the weight applied to the reference sample located at the upper left corner can be derived using Equation 11. Then, the encoder / decoder can generate predicted samples using Equation 12 based on the determined weights.

[0148] According to one embodiment of the present invention, the encoder / decoder can set different weightings for the relatively longer and shorter sides when dealing with non-square blocks other than square blocks. For example, the encoder / decoder can set the weighting applied to the relatively longer side to be smaller than the weighting applied to the shorter side. In equations 9 and 10 described above, the weighting can be set differently for the shorter side than for the longer side. As an example, the weighting can be set to 16, 8, 4, etc., instead of 32. Alternatively, the scale variable nScale used in equations 9 and 10 described above can be used. The encoder / decoder can set its value based on the position of the longer and shorter sides.

[0149] In one embodiment, when using multiple reference line samples, the encoder / decoder can apply the PDPC to vertical and / or horizontal modes. Alternatively, the encoder / decoder can apply the PDPC to vertical, horizontal, DC, and PLANAR modes.

[0150] Figure 20 is a flowchart showing a video signal processing method according to one embodiment of the present invention. Referring to Figure 20, the explanation will focus on the decoder for convenience, but the present invention is not limited to this, and the video signal processing method according to this embodiment can be applied to an encoder in substantially the same manner.

[0151] Referring to Figure 20, the decoder determines whether the current block is in intra-sub-partition (ISP) mode (S2001).

[0152] When the ISP mode is applied to the current block, the decoder divides the current block into multiple horizontal or vertical rectangular transformation blocks (S2002).

[0153] The decoder generates a predicted block for each of the conversion blocks by performing an intra prediction for each of the conversion blocks (S2003).

[0154] The decoder reconstructs the current block based on the residual block of the conversion block and the predicted block (S2004).

[0155] As described above, the step of generating the prediction block may include a step of performing position-dependent intra-prediction sample filtering on each transformed block separated from the current block.

[0156] Furthermore, as described above, the step of generating the prediction block may further include a step of determining whether or not the position-dependent intra-predictive sample filtering is applied based on at least one of the width and height of the transformation block.

[0157] Furthermore, as described above, the step of determining whether or not to apply the position-dependent intra predictive sample filtering may be performed by deciding to apply the position-dependent intra predictive sample filtering if the width of the transformation block is greater than or equal to a preset reference value, and the height of the transformation block is greater than or equal to the preset reference value.

[0158] Furthermore, as mentioned above, the residual block of the transformation block may be derived by performing an inverse secondary transform and an inverse primary transform on a unit of the transformation block.

[0159] Furthermore, as described above, the process may include the steps of: determining whether or not a quadratic transformation is applied to the current block; if the quadratic transformation is applied to the current block, deriving a set of quadratic transformation kernels to be applied to the current block from a predefined set of quadratic transformation kernels based on the intra-prediction mode of the current block; determining the quadratic transformation kernel to be applied to the current block within the determined set of quadratic transformation kernels; generating a quadratic inversely transformed block of the transformation block by performing a quadratic inversely transformed block on the transformation block unit; and generating a residual block of the transformation block by performing a linear inversely transformed block on the quadratic inversely transformed block.

[0160] The embodiments of the present invention described above can be embodied through a variety of means. For example, embodiments of the present invention can be embodied through hardware, firmware, software, or a combination thereof.

[0161] In the case of hardware implementation, the method according to the embodiment of the present invention is implemented by one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSDPs (Digital Signal Processing Devices), PDLs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, etc.

[0162] In the case of implementation by firmware or software, the method according to the embodiment of the present invention is implemented in the form of a module, procedure, or function that performs the functions or operations described above. The software code is stored in memory and implemented by a processor. The memory is located inside or outside the processor and exchanges data with the processor by various already known means.

[0163] Some embodiments also embody the form of recording media containing computer-executable instructions, such as program modules executed by a computer. Computer-readable media are any available media that can be accessed by a computer, and include both volatile and non-volatile media, and isolated and non-isolated media. Computer-readable media also include both storage media and communication media. Computer storage media include both volatile and non-volatile media, isolated and non-isolated media, and embodied in any method or technique for storing information such as computer-readable instructions, data structures, program modules, or other data. Communication media typically include computer-readable instructions, data structures, or other data such as modulated data signals or program modules, or other transmission mechanisms, and include any information transmission media.

[0164] The above description of the present invention is illustrative, and a person with ordinary skill in the art to which the present invention pertains should understand that it can be easily modified into other specific forms without altering the technical idea or essential features of the present invention. Therefore, the above embodiments should be understood to be illustrative and not limiting in all respects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0165] The scope of the present invention is indicated by the claims described below rather than by the detailed description above, and all modifications or altered forms derived from the meaning and scope of the claims and the concept of equivalents thereto should be interpreted as being included within the scope of the present invention. [Industrial applicability]

[0166] The preferred embodiments of the present invention described above are disclosed for illustrative purposes only, and those skilled in the art will be able to improve, modify, substitute, or add to them in various other embodiments within the technical concept and technical scope of the present invention disclosed in the appended claims.

Claims

1. A device for decoding video signals, Including the processor, The aforementioned processor, If the current block is subject to Intra Sub-Partition (ISP) mode, the current block is divided into multiple transformed blocks. The aforementioned plurality of transformation blocks include a first transformation block and a second transformation block, The first prediction block of the first transformation block and the second prediction block of the second transformation block are obtained, The first residual block of the first transformation block and the second residual block of the second transformation block are obtained, The first residual block and the second residual block are obtained by performing a Low Frequency Non-Separable Transform (LFNST) on each of the first and second transformation blocks. The current block is restored based on the first prediction block, the second prediction block, the first residual block, and the second residual block. The apparatus is obtained by applying position-dependent intra prediction sample filtering when the width of each of the plurality of transformation blocks is greater than or equal to a preset value, and the height of each of the plurality of transformation blocks is greater than or equal to the preset value.

2. The apparatus according to claim 1, wherein the conversion kernel for the low-bandwidth unseparated conversion is determined based on the intra-prediction mode of the current block.

3. The apparatus according to claim 1, wherein the intra-prediction mode of the current block is DC mode, planar mode, or angular mode.

4. A device for encoding video signals, Including the processor, The aforementioned processor, The bitstream is obtained to be decoded by the decoder using the decoding method. The decoding method is, If the current block is subject to an Intra Sub-Partition (ISP) mode, the step is to divide the current block into a plurality of transformed blocks, wherein the plurality of transformed blocks include a first transformed block and a second transformed block; A step of obtaining the first prediction block of the first transformation block and the second prediction block of the second transformation block; A step of obtaining the first residual block of the first conversion block and the second residual block of the second conversion block, wherein the first residual block and the second residual block are obtained by performing a Low Frequency Non-Separable Transform (LFNST) on each of the first and second conversion blocks; and The process includes the step of restoring the current block based on the first prediction block, the second prediction block, the first residual block, and the second residual block, The apparatus is obtained by applying position-dependent intra prediction sample filtering when the width of each of the plurality of transformation blocks is greater than or equal to a preset value, and the height of each of the plurality of transformation blocks is greater than or equal to the preset value.

5. The apparatus according to claim 4, wherein the conversion kernel for the low-bandwidth unseparated conversion is determined based on the intra-prediction mode of the current block.

6. The apparatus according to claim 4, wherein the intra-prediction mode of the current block is DC mode, planar mode, or angular mode.

7. A method for obtaining a bitstream, If the current block is subject to an Intra Sub-Partition (ISP) mode, the step is to divide the current block into a plurality of transformed blocks, wherein the plurality of transformed blocks include a first transformed block and a second transformed block; A step of obtaining the first prediction block of the first transformation block and the second prediction block of the second transformation block; A step of obtaining the first residual block of the first conversion block and the second residual block of the second conversion block, wherein the first residual block and the second residual block are obtained by performing a Low Frequency Non-Separable Transform (LFNST) on each of the first and second conversion blocks; A step of restoring the current block based on the first prediction block, the second prediction block, the first residual block, and the second residual block, wherein the first prediction block and the second prediction block are obtained by applying position-dependent intra prediction sample filtering if the width of each of the plurality of transformation blocks is greater than or equal to a preset value, and the height of each of the plurality of transformation blocks is greater than or equal to the preset value; A method comprising the step of obtaining a bitstream by encoding information for the aforementioned plurality of transformation blocks.

8. The method according to claim 7, wherein the conversion kernel for the low-bandwidth unseparated conversion is determined based on the intra-prediction mode of the current block.

9. The method according to claim 7, wherein the intra-prediction mode of the current block is DC mode, planar mode, or angular mode.

10. A video signal processing method, If the current block is subject to an Intra Sub-Partition (ISP) mode, the step is to divide the current block into a plurality of transformed blocks, wherein the plurality of transformed blocks include a first transformed block and a second transformed block; A step of obtaining the first prediction block of the first transformation block and the second prediction block of the second transformation block; A step of obtaining the first residual block of the first conversion block and the second residual block of the second conversion block, wherein the first residual block and the second residual block are obtained by performing a Low Frequency Non-Separable Transform (LFNST) on each of the first and second conversion blocks; and The process includes the step of restoring the current block based on the first prediction block, the second prediction block, the first residual block, and the second residual block, A video signal processing method wherein the first prediction block and the second prediction block are obtained by applying position-dependent intra prediction sample filtering when the width of each of the plurality of transformation blocks is greater than or equal to a preset value, and the height of each of the plurality of transformation blocks is greater than or equal to the preset value.

11. The method according to claim 10, wherein the conversion kernel for the low-bandwidth unseparated conversion is determined based on the intra-prediction mode of the current block.

12. The method according to claim 10, wherein the intra-prediction mode of the current block is DC mode, planar mode, or angular mode.

Images