# US 12,225,213 B2 · Transform-based image coding method and apparatus therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,225,213 B2 - Document ID: US12225213B2 - Status: Granted - Kind: B2 - Application number: 18/442,607 - Filed: 2024-02-15 - Published: 2024-06-13 - Granted: 2025-02-11 - Earliest claimed: 2019-09-25 - Assignees: Xiaomi Inc. - Applicants: LG Electronics Inc. - Inventors: Moonmo Koo; Jaehyun Lim; Seunghwan Kim - Web page: https://patentgrep.com/patent/US12225213B2 ## CPC - H04N 19/12: Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264 - H04N 19/18: the unit being a set of transform coefficients - H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks - H04N 19/122: Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type - H04N 19/124: Quantisation - H04N 19/14: Coding unit complexity, e.g. amount of activity or edge presence estimation (H04N19/146 takes precedence) - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/186: the unit being a colour or a chrominance component - H04N 19/60: using transform coding - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N 19/96: Tree coding, e.g. quad-tree coding - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## 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; deriving a residual sample by applying, to the transform coefficient, at least one of LFNST and MTS; and generating a reconstructed picture on the basis of the residual samples, wherein the LFNST is performed on the basis of an LFNST index indicating an LFNST kernel, the MTS is performed on the basis of an MTS index indicating an MTS kernel, and the LFNST index may be parsed before the MTS index. ## Claims ### Claim 1 An image decoding method performed by a decoding apparatus, the method comprising: obtaining prediction related information for a current block from a bitstream; deriving prediction samples for a current block based on the prediction related information; obtaining residual information from the bitstream; deriving transform coefficients for the current block based on the residual information; deriving residual samples by applying at least one of a low frequency non-separable transform (LFNST) kernel derived from an LFNST index or a primary transform kernel derived from a multiple transform selection (MTS) index to the transform coefficients; and generating a reconstructed picture based on the prediction samples and the residual samples, wherein the LFNST index is parsed before the MTS index, and wherein the MTS index is signaled based on a value of the LFNST index. ### Claim 2 (depends on 1) The image decoding method of claim 1, wherein when the current block is a luma block and the LFNST index is 0, the MTS index is parsed. ### Claim 3 (depends on 1) The image decoding method of claim 1, wherein when a tree type of the current block is a dual tree, the LFNST index for each of a luma block and a chroma block is parsed. ### Claim 4 (depends on 1) The image decoding method of claim 1, wherein the deriving the transform coefficient comprises deriving a width and a height for a top-left region in which a last significant coefficient may exist in the current block by zero-out, and wherein the width and height for the top-left region are derived before parsing the MTS index. ### Claim 5 (depends on 1) The image decoding method of claim 1, wherein the last significant coefficient position is derived based on the width and the height for the top-left region, wherein last significant coefficient position information is binarized based on the width and the height for the top-left region. ### Claim 6 An image encoding method performed by an encoding apparatus, the method comprising: deriving prediction samples for a current block; deriving residual samples for the current block based on the prediction sample; deriving transform coefficients by applying at least one of a low frequency non-separable transform (LFNST) kernel or a primary transform kernel to the residual samples; and encoding i) prediction related information, ii) residual information related to the transform coefficients and iii) at least one of an LFNST index related to the LFNST kernel and an MTS index related to the primary transform kernel, wherein the LFNST index is encoded before the MTS index, and wherein the MTS index is encoded based on a value of the LFNST index. ### Claim 7 (depends on 6) The image encoding method of claim 6, wherein when the current block is a luma block and the LFNST index is 0, the MTS index is encoded. ### Claim 8 (depends on 6) The image encoding method of claim 6, wherein when a tree type of the current block is a dual tree, the LFNST index for each of a luma block and a chroma block is encoded. ### Claim 9 (depends on 6) The image encoding method of claim 6, wherein the deriving the transform coefficient comprises deriving a width and a height for a top-left region in which a last significant coefficient may exist in the current block by zero-out, and wherein the width and the height for the top-left region are derived before signaling the MTS index. ### Claim 10 (depends on 9) The image encoding method of claim 9, wherein the last significant coefficient position is derived based on the width and the height for the top-left region, and wherein the last significant coefficient position information is binarized based on the width and the height of the top-left region. ### Claim 11 A transmitting method comprising obtaining a bitstream, wherein the bitstream is generated by deriving prediction samples for a current block; deriving residual samples for the current block based on the prediction sample; deriving transform coefficients by applying at least one of a low frequency non-separable transform (LFNST) kernel or a primary transform kernel to the residual samples; and encoding i) prediction related information, ii) residual information related to the transform coefficients and iii) at least one of an LFNST index related to the LFNST kernel and an MTS index related to the primary transform kernel to generate the bitstream, wherein the LFNST index is encoded before the MTS index, and wherein the MTS index is encoded based on a value of the LFNST index.