Abstract: An image decoding method according to the present document can comprise the steps of: deriving a transform coefficient for a current block on the basis of residual information; determining whether an effective coefficient is in a second area that excludes the upper left first area of the current block; parsing an MTS index from a bitstream if the effective coefficient is not in the second area; and deriving a residual sample by applying, to transform coefficients of the first area, an MTS kernel derived on the basis of the MTS index.

Abstract: According to the disclosure of the present disclosure: an LFNST set index for a current block may be derived on the basis of an intra prediction mode on the basis of the intra prediction mode for the current block being a WAIP mode, the LFNST set index may be derived as predetermined one value; and on the basis of the intra prediction mode for the current block being an NAIP mode, the LFNST set index may be derived as one of predetermined N values. Accordingly, it is possible to maximize the coding performance that can be brought about by LFNST within the implementation complexity allowed by a next standard.

Abstract: A method and device for processing a video signal using a reduced transform are provided. A method for decoding a video signal includes splitting a current block into a plurality of subblocks based on a first flag for a split direction of the current block, determining a subblock, to which a transform is applied, among the plurality of subblocks based on a second flag for a position of a transform target block, determining a transform target area in the subblock, and applying an inverse transform including a horizontal transform and a vertical transform to transform coefficients of the transform target area. The transform target area is determined based on a transform type applied to the subblock and a size of the subblock.

Abstract: Embodiments of the present invention provide a method and apparatus for processing a video signal. A method for decoding an image signal according to an embodiment of the present invention comprises the steps of: for a current block having a width and a height different from each other, determining a modified intra prediction mode from an intra prediction mode, on the basis of a ratio between the width and the height of the current block and the intra prediction mode; determining an inverse non-separable transform set on the basis of the modified intra prediction mode; and applying an inverse non-separable transform matrix selected from the inverse non-separable transform set with respect to the top-left region of the current block, which is determined according to the width and the height of the current block.

Abstract: An image decoding method according to the present document comprises the step of deriving modified transform coefficients by applying LFNST to transform coefficients, wherein the step of deriving the modified transform coefficients comprises the steps of: deriving a variable indicating whether an effective coefficient is present in a DC component of a current block; and parsing an LFNST index on the basis of whether the variable indicates that the effective coefficient is present in a position other than the DC component, wherein the variable may be derived on the basis of an individual transform skip flag value for a color component of the current block.

Abstract: An image decoding method according to the present disclosure comprises the steps of: deriving residual samples with respect to a target block on the basis of an inverse primary transform with respect to modified transform coefficients; and on the basis of the residual samples, generating a reconstructed picture, wherein a step of deriving the modified transform coefficients may include the steps of: parsing an LFNST index on the basis of the tree-type of a current block not being a dual-tree chroma and a MIP mode not being applicable to the current block; and deriving the modified transform coefficients on the basis of the LFNST index and an LFNST matrix.

Abstract: An image decoding method according to the present document comprises the steps of: receiving a quantized transform coefficient for a target block and a transform index for a non-separable secondary transform; dequantizing the quantized transform coefficients to derive transform coefficients; deriving modified transform coefficients on the basis of a matrix operation of a transform kernel matrix in a transform set indicated by the transform index and a transform coefficient list corresponding to the magnitude of dequantized transform coefficients; clipping the modified transform coefficients to a predetermined range of values; and deriving residual samples for the target block on the basis of an inverse primary transform with respect to the modified transform coefficients clipped.

Abstract: The present invention relates to a video signal decoding method based on a Multiple Transform Selection (MTS).

Abstract: A video decoding method and device according to the present disclosure can derive a transform coefficient of a current block from a bitstream, derive a residual sample of the current block by performing at least one of inverse quantization or inverse transformation on the transform coefficient of the current block, and restore the current block on the basis of the residual sample of the current block. A transform kernel of the current block for inverse transformation is determined from a transform set including a plurality of transform kernel candidates, and the plurality of transform kernel candidates may include a reference transform kernel for the current block.

Abstract: According to the disclosure of the present document, a quantization parameter for a quantized transform coefficient present at a DC position within a current block can have the smallest value among quantization parameters which are applied to quantized transform coefficients within the current block, on the basis that an LFNST is applied to the current block. Therefore, coding performance capable of being brought by the LFNST can be maximized within the implementation complexity permitted in forthcoming standards.

Abstract: An image decoding method according to the present document comprises the steps of: receiving a quantized transform coefficient for a target block and a transform index for non-separable quadratic transform; deriving transform coefficients by inversely quantizing the quantized transform coefficient; deriving corrected transform coefficients on the basis of a transform kernel matrix in a predetermined transform set indicated by the transform index; and deriving residual samples for the target block on the basis of inverse linear transform for the corrected transform coefficients, wherein when the target block is divided into a predetermined number of sub-blocks and is coded by intra prediction, the corrected transform coefficients are derived in units of the sub-blocks, and the transform index is received for the target block.

Abstract: An image decoding method and device according to the present disclosure may induce transform coefficients of a current block from a bitstream, perform inverse quantization and inverse transformation on the transform coefficients of the current block to induce residual samples of the current block, and restore the current block on the basis of the residual samples of the current block.

Abstract: An image decoding method performed by means of a decoding device according to the present disclosure comprises the steps of: deriving transform coefficients of a target block from a bitstream; deriving a non-separable secondary transform (NSST) index with respect to the target block; performing inverse transform with respect to the transform coefficients of the target block on the basis of the NSST index and thus deriving residual samples of the target block; and generating a reconstructed picture on the basis of the residual samples.

Abstract: A video signal encoding method according to an embodiment of the present invention comprises checking a transform block including residual samples except a prediction sample from a picture of the video signal, generating transform coefficients through a transform for the residual samples of the transform block based on a size of the transform block, and performing quantization and entropy coding the transform coefficients, wherein generating the transform coefficients includes, applying a forward primary transform to each of a horizontal direction and vertical direction of the transform block including the residual samples, and not applying a forward non-separable secondary transform to the transform block to which the primary transform has been applied when the size of the transform block is smaller than or equal to 4×4, and applying the forward non-separable secondary transform to the transform block when the size of the transform block is greater than 4×4.

Abstract: An image decoding method according to the present document comprises the steps of: deriving a transform coefficient for a current block on the basis of residual information; when LFNST is applied to the current block, receiving an LFNST index related to an LFNST matrix; and deriving a modified transform coefficient for the current block on the basis of the LFNST matrix, wherein the LFNST index may be signaled for a luma component of the current block.

Abstract: A video decoding method and device disclosed herein may: derive transform coefficients of the current block from a bitstream; perform at least one of inverse quantization or inverse transform on the transform coefficients of the current block and derive residual samples of the current block; and recover the current block on the basis of the residual samples of the current block. Here, the inverse transform is performed on the basis of a length-based transform kernel, and the length-based transform kernel may include at least one of the horizontal transform kernel having the same length as the width of the current block or the vertical transform kernel having the same length as the height of the current block.

Abstract: Provided is a method for decoding a video signal based on a reduced transform, which includes: checking whether a transform skip is applied to a current block; obtaining a transform index indicating a transform kernel of the current block from the video signal when the transform skip is not applied to the current block; determining a region where a primary transform is applied to the current block based on the transform kernel indicated by the transform index and a size of the current block; and performing an inverse primary transform on the region to which the primary transform is applied by using the transform kernel indicated by the transform index.

Abstract: Embodiments in the present specification provide a method and device for processing video signal including steps of: obtaining a sub-block transform (SBT) flag indicating whether a SBT is applied, wherein the SBT represents a transform applied to a transform unit corresponding to one of subblocks split from a coding unit; determining a variable value related to a transform target region based on the SBT flag and a size value of the transform unit, wherein if the SBT flag equals to 1 and the size value is greater than a threshold value, the variable value is determined as the threshold value; obtaining position information of a last significant coefficient according to a scan order within the transform unit, wherein the position information of the last significant coefficient is coded based on the variable value; and performing an inverse-transform based on the position information of the last significant coefficient.

Abstract: An image decoding method according to the present document comprises the steps of: deriving a quantized transform coefficient for a current block on the basis of BDPCM; deriving a transform coefficient by performing dequantization on the quantized transform coefficient; and deriving a residual sample on the basis of the transform coefficient, wherein, when the BDPCM is applied to the current block, inverse non-separable transform is not applied to the transform coefficient.

Abstract: A video signal encoding method according to an embodiment of the present invention comprises checking a transform block including residual samples except a prediction sample from a picture of the video signal, generating transform coefficients through a transform for the residual samples of the transform block based on a size of the transform block, and performing quantization and entropy coding the transform coefficients, wherein generating the transform coefficients includes, applying a forward primary transform to each of a horizontal direction and vertical direction of the transform block including the residual samples, and not applying a forward non-separable secondary transform to the transform block to which the primary transform has been applied when the size of the transform block is smaller than or equal to 4×4, and applying the forward non-separable secondary transform to the transform block when the size of the transform block is greater than 4×4.