Abstract: An image decoding method, according to the present document, comprises a step of generating residual samples for a current block on the basis of residual information, wherein the residual samples are generated on the basis of information on a transform kernel set and transform coefficients for the current block, the transform coefficients are derived on the basis of the residual information, and the information on the transform kernel set represents a transform kernel set to be applied to the current block from among transform kernel set candidates. At least one bin from among bins of a bin string of the information on the transform kernel set is derived on the basis of context coding, and the context coding is performed on the basis of at least one context model.

Abstract: An image decoding method according to the present document comprises the steps of: deriving transform coefficients through inverse quantization on the basis of quantized transform coefficients for a target block; deriving modified transform coefficients on the basis of an inverse reduced secondary transform (RST) for the transform coefficients; and generating, on the basis of an inverse primary transform for the modified transform coefficients, a restoration picture based on residual samples for the target block, wherein the modified transform coefficients derived according to the inverse RST are two-dimensionally arranged according to the order of a row priority direction or a column priority direction according to an intra prediction mode to be applied to the target block.

Abstract: Embodiments of the present invention provide video signal processing methods.

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: The present disclosure provides a method of reconstructing a video signal based on a reduced secondary transform, which includes: obtaining a secondary transform index from the video signal; deriving a secondary transform corresponding to the secondary transform index, wherein the secondary transform represents a reduced secondary transform, and the reduced secondary transform represents a transform outputting L (L<N) transform coefficient data (L×1 transform coefficient vectors) based on inputted N residual data (N×1 residual vectors); obtaining a transform coefficient block by performing an entropy decoding and a dequantization for a current block (N×N); performing an inverse secondary transform for the transform coefficient block using the reduced secondary transform; performing an inverse primary transform for a block which the inverse secondary transform is applied to; and reconstructing the current block using a block which the inverse primary transform is applied to.

Abstract: A method and a device for processing a video signal are disclosed. In particular, a method for decoding a video signal includes parsing a first syntax element indicating a primary transform kernel applied to a primary transform of a current block; determining whether a secondary transform is applicable to the current block based on the first syntax element; if the secondary transform is applicable to the current block, parsing a second syntax element indicating a secondary transform kernel applied to a secondary transform of the current block; deriving a secondary inverse-transformed block, by performing a secondary inverse-transform for a top-left specific region of the current block using a secondary transform kernel indicated by the second syntax element; and deriving a residual block of the current block, by performing a primary inverse-transform for the secondary inverse-transformed block using a primary transform kernel indicated by the first syntax element.

Abstract: An image decoding method according to the present document may include the steps of: deriving the position of the final significant coefficient in the current block and transform coefficients for the current block on the basis of residual information; determining whether the index of a sub-block including the final significant coefficient is 0 and whether the position of the final significant coefficient in the sub-block is greater than 0; determining whether a significant coefficient exists in a second area excluding a first area at the upper left end of the current block; and parsing an LFNST index from a bitstream when the position of the final significant coefficient is determined to be greater than 0 in the sub-block in which the index is 0, and the significant coefficient does not exist in the second area.

Abstract: The present disclosure, in a method of decoding a video signal, provides a method including checking whether a transform skip is applied to a current block; acquiring a transform index indicating transform types applied to a horizontal direction and a vertical direction of the current block from among a plurality of predefined transform types from the video signal when the transform skip is not applied to the current block; and performing an inverse primary transform on the current block using the transform types indicated by the transform index, wherein the transform types applied to the horizontal direction and the vertical direction of the current block are determined from among transform types defined according to an intra prediction mode of the current block based on the transform index.

Abstract: Embodiments in the present specification provide a video signal processing method and device. A method of processing a video signal according to an embodiment in the present specification comprises the steps of: acquiring an intra-prediction mode for a current block from the video signal; determining a modified intra-prediction mode from the intra-prediction mode for the current block on the basis of the width and height of and the intra-prediction mode for the current block; and applying a transform determined on the basis of the modified intra-prediction mode. The accuracy of prediction can be further improved by deriving a modified intra-prediction mode according to a wide-angle intra-prediction mode according to the shape of and an intra-prediction mode for a current block.

Abstract: An embodiment of the present specification provides a method and device for processing video data. A method for processing a video signal according to an embodiment of the present specification may comprise the steps of: acquiring a transform index related to one of a plurality of transform combinations including combinations of one or more transform kernels for transforming of a current block of the video signal; deriving a transform combination including a vertical transform and a horizontal transform related to the transform index; and applying each of the vertical transform and horizontal transform of the transform combination to the current block.

Abstract: An image decoding method according to the present document may comprise the steps of: receiving flag information, which indicates whether a scaling list is available while an LFNST is being performed, and an LFNST index and residual information for the current block; determining, on the basis of the flag information, the LFNST index, and the tree type of the current block, whether the scaling list is applicable to the current block; deriving transform coefficients for the current block from the residual information on the basis of the determination result; and applying the LFNST to the transform coefficients to derive corrected transform coefficients.

Abstract: A video decoding method according to the present document is characterized by comprising: a step for deriving transform coefficients through inverse quantization on the basis of quantized transform coefficients for a target block; a step for deriving modified transform coefficients on the basis of an inverse reduced secondary transform (RST) of the transform coefficients; and a step for generating a reconstructed picture on the basis of residual samples for the target block on the basis of an inverse primary transform of the modified transform coefficients, wherein the inverse RST using a transform kernel matrix is performed on transform coefficients of the upper-left 4×4 region of an 8×8 region of the target block, and the modified transform coefficients of the upper-left 4×4 region, upper-right 4×4 region, and lower-left 4×4 region of the 8×8 region are derived through the inverse RST.

Abstract: An image information decoding method performed by means of a decoding device according to the present invention comprises the steps of: decoding a non-separable secondary transform (NSST) index from a bitstream if NSST is applied to a target block; decoding information relating to transform coefficients with respect to the target block from the bitstream on the basis of the decoded NSST index; and deriving the transform coefficients with respect to the target block on the basis of the decoded information relating to the transform coefficients, wherein the NSST index is decoded prior to the information relating to the transform coefficients with respect to the target block.

Abstract: An image decoding method performed by means of a decoding device according to the present invention comprises the steps of: deriving quantized transform coefficients with respect to a target block from a bitstream; performing inverse quantization with respect to the quantized transform coefficients with respect to the target block and deriving transform coefficients; deriving residual samples with respect to the target block on the basis of reduced inverse transform with respect to the transform coefficients; and generating a reconstructed picture on the basis of the residual samples with respect to the target block and prediction samples with respect to the target block. The reduced inverse transform is performed on the basis of a reduced inverse transform matrix. The reduced inverse transform matrix is a non-square matrix of which the number of columns is smaller than the number of rows.

Abstract: An image decoding method according to the present document may comprise the steps of: receiving, at a general restriction information level, a restriction flag for restricting whether to perform a non-separable inverse transform in a low frequency area of a transform block; receiving, at a sequence parameter set level, an activation flag indicating whether to activate the non-separable inverse transform; parsing a transform index used for the non-separable inverse transform, on the basis of the restriction flag and the activation flag; and performing the non-separable inverse transform on the transform block on the basis of the transform index.

Abstract: An image decoding method according to the present document comprises the steps of: receiving an intra-MIP syntax element for a first target block; deriving the value of the intra-MIP syntax element; setting a variable MIP flag for the preset specific area, which is the same as the area of the first target block, on the basis of the value of the intra-MIP syntax element; deriving an intra-prediction mode of the second target block on the basis of the variable MIP flag; and deriving a prediction sample of the second target block on the basis of the intra-prediction mode of the second target block.

Abstract: An image decoding method according to the present document comprises a step of deriving a corrected transform coefficient, wherein the step of deriving the corrected transform coefficient comprises the steps of: determining whether LFNST can be applied to the height and width of a divided sub-partition block when an ISP is applied to a current block; parsing a LFNST index when the LFNST can be applied; and deriving the corrected transform coefficient on the basis of the LFNST index and a LFNST matrix.

Abstract: A method for decoding an image by a decoding device according to the present invention comprises the steps of: deriving, from a bit stream, transform coefficients of a block to be decoded; deriving residual samples of the block to be decoded, on the basis of a selective transform of the transform coefficients; and generating a reconstructed picture on the basis of the residual samples of the block to be decoded and prediction samples of the block to be decoded, wherein the selective transform is performed on the basis of a modified transform matrix, the modified transform matrix comprises a matrix including a modified basis vector, and the modified basis vector contains a certain number of elements selected from N elements.

Abstract: An image decoding method according to the present disclosure includes deriving transform coefficients through dequantization based on the quantized transform coefficients for the target block; deriving modified transform coefficients based on an inverse reduced secondary transform (RST) for the transform coefficients; deriving residual samples for the target block based on an inverse primary transform for the modified transform coefficients; and generating a reconstructed samples based on the residual samples, and prediction samples derived based on an intra prediction mode for the target block, wherein the inverse RST is performed based on a transform kernel matrix selected from a transform set including a plurality of transform kernel matrices, the transform set is determined based on a mapping relationship according to the intra prediction mode applied to the target block, and a plurality of intra prediction modes including the intra prediction mode of the target block are mapped to one transform set.

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.