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 may comprise: a step of deriving transform coefficients for a current block by performing inverse quantization on the basis of residual information; and a step of deriving modified transform coefficients by applying LFNST to the transform coefficients, wherein the step of deriving the transform coefficients comprises a step of parsing position information of a last non-zero transform coefficient, an LFNST index related to application of the LFNST is parsed after parsing a position of the last non-zero transform coefficient, and the transform coefficients are derived after parsing the LFNST index.

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: The present disclosure relates to a method for decoding a video signal based on adaptive multiple transforms (AMT). The method includes: obtaining an AMT index from the video signal, where the AMT index indicates any one of a plurality of transform combinations in a transform configuration group, and the transform configuration group includes discrete sine transform type 7 (DST7) and discrete cosine transform type 8 (DCT8); deriving a transform combination corresponding to the AMT index, where the transform combination includes a horizontal transform and a vertical transform, and at least one of the DST-7 or the DCT-8; performing an inverse transform on a current block on the basis of the transform combination; and restoring the video signal by using the inversely transformed current block. The AMT represents a transform scheme that is performed based on a transform combination adaptively selected from a plurality of transform combinations.

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: An image decoding method according to the present document comprises the steps of: obtaining intra prediction mode information and an LFNST index; deriving an intra prediction mode of a current block on the basis of intra prediction mode information; when wide-angle intra prediction is applied to the current block, deriving a modified intra prediction mode by means of intra prediction mode remapping; deciding an LFNST set comprising LFNST matrices on the basis of the modified intra prediction mode; selecting one of the LFNST matrices on the basis of the LFNST set and LFNST index; and deriving transform coefficients for the current block on the basis of the selected LFNST matrix.

Abstract: An image decoding method according to the present document comprises the steps of: determining whether or not an effective coefficient is present in a second area not including an upper-left first area of a current block; parsing an MTS index from a bitstream on the basis that the effective coefficient is not present in the second area; and deriving residual samples for the current block by applying a transform kernel, which is derived on the basis of the MTS index, to transform coefficients in the first area, wherein the MTS index can be parsed on the basis that the effective coefficient, which is present in a scan sub-block which is scanned for the effective coefficient, is not present in the second area.

Abstract: An image decoding method according to the present document comprises the steps of: updating an intra-prediction mode of a chroma block on the basis of an intra-prediction mode of a luma block corresponding to the chroma block on the basis of the intra-prediction mode of the chroma block being a cross-component linear model (CCLM) mode; and determining a LFNST set including LFNST matrixes on the basis of the updated intra-prediction mode, wherein the updated intra-prediction mode is derived as an intra-prediction mode corresponding to a specific position in the luma block, and the updated intra-prediction mode is updated as an intra-DC mode on the basis of the intra-prediction mode, that corresponds to the specific position, being an intra-block copy (IBC) mode.

Abstract: An image decoding method includes a step of deriving a residual sample, wherein the step of deriving the residual sample includes the steps of: when a current block is divided into sub-partition blocks, deriving a transform kernel for an inverse primary transform applied to a sub-partition block based on a horizontal or a vertical length of the sub-partition block; and deriving the residual sample from transform coefficients based on the transform kernel.

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.