Abstract: Embodiments of the disclosure provide a method and apparatus for processing a video signal. Particularly, a method for decoding a video signal according to an embodiment of the disclosure may include: determining, among predefined secondary transform sets based on intra-prediction modes of a current block, a secondary transform set applied to the current block; obtaining a first syntax element indicating a secondary transform matrix applied to the current block in the determined secondary transform set; deriving a secondary inverse-transformed block by performing a secondary inverse transform on a left top region of the current block by using the secondary transform matrix specified by the first syntax element; and deriving a residual block of the current block by performing a primary inverse transform on the secondary inverse-transformed block using a primary transform matrix of the current block.

Abstract: An image decoding method and device according to the present disclosure can acquire residual information from a bitstream, derive transform coefficients of the current block on the basis of the residual information, derive residual samples of the current block by performing inverse quantization and/or inverse transform on the transform coefficients of the current block, and reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse transform can be performed on the basis of a non-separable primary transform and/or a low frequency non-separable transform.

Abstract: An image decoding method according to the present document comprises the steps of: applying LFNST to transform coefficients to derive modified transform coefficients; deriving residual samples for a target block on the basis of an inverse primary transform for the modified transform coefficients; and generating a reconstructed picture on the basis of the residual samples, wherein the step of deriving the modified transform coefficients can comprise the steps of parsing an LFNST index on the basis of the current block tree type being a dual tree chroma, 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: acquiring prediction-related information and residual-related information for a current block; deriving transform coefficients for the current block on the basis of the residual-related information; and generating residual samples of the current block on the basis of the transform coefficients, wherein the residual-related information includes low-frequency non-separable transform (LFNST) index information indicating information relating to non-separable transform for a low-frequency transform coefficient of the current block on the basis of a matrix-based intra prediction (MIP) flag.

Abstract: Embodiments of the present invention provide a video signal processing method and device. Particularly, a method for decoding a video signal, may comprise the steps of: checking whether a transfer skip is applied to a current block; obtaining, from a video signal, a transform index for indicating a transform type set applied to the current block when the transform skip is not applied to the current block, wherein the transform type set includes transform types applied to the current block in horizontal and vertical directions; checking whether the transform type set includes DCT2; determining a region to which a primary transform is applied based on a checking result; and performing an inverse transform on the region to which the primary transform is applied in the horizontal and vertical directions using the transform types included in the transform type set.

Abstract: An image decoding method, according to the present document, comprises the steps of: determining whether to parse an MTS index for applying an MTS to the current block; deriving residual samples for the current block by applying the MTS to the current block on the basis of the MTS index; and generating a reconstructed picture on the basis of the residual samples, wherein the step of determining whether to parse the MTS index includes determining the tree type of the current block, the division type of the current block, and whether zero-out for the MTS has been performed in the current block.

Abstract: An image decoding method and apparatus, according to the present disclosure, may: derive transform coefficients of the current block from a bitstream; determine a non-separable primary transform (NSPT) set for the current block; on the basis of a transform index of the current block, determine an NSPT kernel of the current block from the NSPT set; derive residual samples of the current block by applying inverse NSPT to at least one of the transform coefficients of the current block on the basis of the NSPT kernel; and reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse NSPT may be applied on the basis that the size of the current block belongs to a group of one or more block sizes to which NSPT may be applied.

Abstract: An image decoding method and device according to the present disclosure may be provided, the method comprising: acquiring residual information from a bitstream; deriving transform coefficients of a current block on the basis of the residual information; performing at least one of de-quantization and inverse transform on the transform coefficients of the current block so as to derive a residual sample of the current block; and reconstructing the current block on the basis of the residual sample of the current block. Here, the inverse transform may be performed on the basis of at least one of a non-separable primary transform and a low-frequency non-separable transform, and a transform kernel for the inverse transform may be determined on the basis of a transform index indicating any one of multiple transform kernel candidates belonging to a transform set.

Abstract: An image decoding method and device according to the present disclosure may derive conversion factors of a current block from a bitstream, determine a non-separable primary transform (NSPT) set for the current block, apply a reversed NSPT to at least one of the conversion factors of the current block on the basis of one of multiple NSPT Kernel candidates included in the NSPT set to derive residual samples of the current block, and restore the current block on the basis of the residual samples of the current block. In this case, the reversed NSPT may be applied based on that a size of the current block is included in a group of one or more sizes of blocks to which the NSPT may be applied.

Abstract: An image decoding method and device, according to the present disclosure, can acquire residual information from a bit-stream, derive transform coefficients of the current block on the basis of the residual information, determine a non-separable primary transform (NSPT) kernel for the current block on the basis of a transform index of the current block, apply inverse NSPT to at least one from among the transform coefficients of the current block on the basis of the NSPT kernel for the current block so as to derive residual samples of the current block, and reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse NSPT can be applied on the basis that the size of the current block belongs to a group of one or more block sizes to which NSPT can be applied.

Abstract: An image decoding method and device, according to the present disclosure, can derive transform coefficients of the current block from a bit-stream, apply inverse non-separable primary transform to at least one from among transform coefficients of the current block so as to derive residual samples of the current block, and reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse non-separable primary transform can be applied on the basis of that the size of the current block belongs to a group of one or more block sizes to which non-separable primary transform can be applied.

Abstract: An image decoding method according to this document comprises the steps of: deriving an LFNST matrix for a current block on the basis of an LFNST index derived from LFNST index information and an LFNST set index; deriving modified transform coefficients on the basis of transform coefficients and the LFNST matrix; and generating residual samples for the current block on the basis of the modified transform coefficients, wherein when the width or height of the current block has a value of 16 and both the width and height have a value of 16 or more, the LFNST matrix may be derived as a 96×32 dimensional matrix. Therefore, coding performance achievable 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: 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: An image decoding method and device according to the present disclosure can acquire residual information from a bitstream, derive transform coefficients of the current block on the basis of the residual information, apply an inverse non-separable primary transform (NSPT) to at least one from among transform coefficients of the current block on the basis of an NSPT set in order to derive residual samples of the current block, and reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse NSPT can be applied on the basis of the size of the current block belonging to a group of one or more block sizes to which the NSPT can be applied.

Abstract: An image decoding method and device according to the present disclosure may: acquire residual information from a bitstream; derive transform coefficients of a current block on the basis of the residual information; 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 reconstruct the current block on the basis of the residual samples of the current block. Here, the inverse transform may be performed on the basis of an inverse non-separable primary transform.

Abstract: An image decoding method according to the present document comprises the steps of: on the basis of an intra prediction mode of a chroma block being a cross-component linear model (CCLM) mode and an intra prediction mode of a luma block corresponding to the chroma block being a palette mode, updating the intra prediction mode of the chroma block to an intra DC mode; on the basis of the updated intra prediction mode, determining an LFNST set including LFNST matrices; and performing LFNST on the chroma block on the basis of an LFNST matrix derived from the LFNST set, wherein the intra DC mode is an intra prediction mode corresponding to a specific location within the luma block.

Abstract: An image decoding method according to the present document comprises a step for deriving a residual sample, wherein the step for deriving the residual sample comprises the steps of: deriving a zero out block for a current block; deriving a context model for last significant coefficient location information on the basis of the width or height of the current block; deriving a value of a last significant coefficient location on the basis of the context model; and deriving the last significant coefficient location on the basis of a value of the last significant coefficient location information and the width or height of the zero out block.

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.