# US 2021/0243443 A1 · Method for coding transform coefficient and device therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0243443 A1 - Document ID: US20210243443A1 - Status: Published application - Kind: A1 - Application number: 17/217,739 - Filed: 2021-03-30 - Published: 2021-08-05 - Earliest claimed: 2018-10-05 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Jungah Choi; Sunmi Yoo; Seunghwan Kim; Jangwon Choi; Jin Heo - Web page: https://patentgrep.com/patent/US20210243443A1 ## CPC - H04N 19/124: Quantisation - H04N 19/91: Entropy coding, e.g. variable length coding [VLC] or arithmetic coding - H04N 19/132: Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking - H04N 19/172: the region being a picture, frame or field - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/18: the unit being a set of transform coefficients - H04N 19/184: the unit being bits, e.g. of the compressed video stream - H04N 19/60: using transform coding - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A method by which a decoding device decodes an image, according to the present invention, comprises the steps of: receiving a bitstream including residual information; deriving a quantized transform coefficient for a current block on the basis of the residual information included in the bitstream; deriving a residual sample for the current block on the basis of the quantized transform coefficient; and generating a restored picture on the basis of the residual sample for the current block. ## Claims ### Claim 1 An image decoding method performed by a decoding apparatus, the method comprising: receiving a bitstream including residual information; deriving a quantized transform coefficient for a current block based on the residual information included in the bitstream; deriving a residual sample for the current block based on the quantized transform coefficient; and generating a reconstructed picture based on the residual sample for the current block, wherein the residual information includes a context-based coded context syntax element, wherein the context syntax element is decoded based on a maximum value of context-coded bins for the current block, and wherein the maximum value is determined by a unit of a transform block. ### Claim 2 (depends on 1) The image decoding method of claim 1, wherein the context syntax element includes a significant coefficient flag related to whether or not the quantized transform coefficient is a non-zero significant coefficient, a parity level flag related to a parity of a transform coefficient level for the quantized transform coefficient, a first transform coefficient level flag related to whether or not the transform coefficient level is greater than a first threshold value, and a second transform coefficient level flag related to whether or not the transform coefficient level for the quantized transform coefficient is greater than a second threshold value, and wherein the maximum value is a maximum value of a sum of a number of the significant coefficient flags, a number of the parity level flags, a number of the first transform coefficient level flags, and a number of the second transform coefficient level flags. ### Claim 3 (depends on 2) The image decoding method of claim 2, wherein the maximum value is determined based on the size of the transform block. ### Claim 4 (depends on 2) The image decoding method of claim 2, wherein when the sum of the number of the significant coefficient flags, the number of the first transform coefficient level flags, the number of the parity level flags, and the number of the second transform coefficient level flags derived based on a 0th quantized transform coefficient to an nth quantized transform coefficient determined by a coefficient scan order reaches the predetermined maximum value, then explicit signaling of a significant coefficient flag, a first transform coefficient level flag, a parity level flag, and a second transform coefficient level flag is omitted for a (n+1)th quantized transform coefficient determined by the coefficient scan order, and a value of the (n+1)th quantized transform coefficient is derived based on a value of coefficient level information included in the residual information. ### Claim 5 (depends on 4) The image decoding method of claim 4, wherein the significant coefficient flags, the first transform coefficient level flags, the parity level flags, and the second transform coefficient level flags included in the residual information are context-based coded, and the coefficient level information is bypass-based coded. ### Claim 6 (depends on 1) The image decoding method of claim 1, wherein the current block is a sub-block within the transform block. ### Claim 7 (depends on 2) The image decoding method of claim 2, wherein the deriving the quantized transform coefficient comprises: decoding the first transform coefficient level flag and the parity level flag; and deriving the quantized transform coefficient based on a value of the decoded parity level flag and a value of the decoded first transform coefficient level flag, and wherein the decoding of the first transform coefficient level flag is performed prior to the decoding of the parity level flag. ### Claim 8 An image encoding method performed by an encoding apparatus, the method comprising: deriving a residual sample for a current block; deriving a quantized transform coefficient based on the residual sample for the current block; and encoding residual information including information on the quantized transform coefficient, wherein the residual information includes a context-based coded context syntax element, wherein the context syntax element is decoded based on a maximum value of context-coded bin for the current block, and wherein the maximum value is determined by a unit of a transform block. ### Claim 9 (depends on 8) The image encoding method of claim 8, wherein the context syntax element includes a significant coefficient flag related to whether or not the quantized transform coefficient is a non-zero significant coefficient, a parity level flag related to a parity of a transform coefficient level for the quantized transform coefficient, a first transform coefficient level flag related to whether or not the transform coefficient level is greater than a first threshold value, and a second transform coefficient level flag related to whether or not the transform coefficient level for the quantized transform coefficient is greater than a second threshold value, and wherein the maximum value is a maximum value of a sum of a number of the significant coefficient flags, a number of the parity level flags, a number of the first transform coefficient level flags, and a number of the second transform coefficient level flags. ### Claim 10 (depends on 9) The image encoding method of claim 9, wherein the maximum value is determined based on the size of the transform block. ### Claim 11 (depends on 9) The image encoding method of claim 9, when the sum of the number of the significant coefficient flags, the number of the first transform coefficient level flags, the number of the parity level flags, and the number of the second transform coefficient level flags derived based on a 0th quantized transform coefficient to an nth quantized transform coefficient determined by a coefficient scan order reaches the predetermined maximum value, then explicit signaling of a significant coefficient flag, a first transform coefficient level flag, a parity level flag, and a second transform coefficient level flag is omitted for a (n+1)th quantized transform coefficient determined by the coefficient scan order, and a value of the (n+1)th quantized transform coefficient is derived based on a value of coefficient level information included in the residual information. ### Claim 12 (depends on 11) The image encoding method of claim 11, the significant coefficient flags, the first transform coefficient level flags, the parity level flags, and the second transform coefficient level flags included in the residual information are context-based coded, and the coefficient level information is bypass-based coded. ### Claim at position 13 -15. (canceled) ### Claim 16 Non-transitory computer-readable storage medium storing encoded information causing a decoding apparatus to perform a video encoding method, the method comprising: receiving a bitstream including residual information; deriving a quantized transform coefficient for a current block based on the residual information included in the bitstream; deriving a residual sample for the current block based on the quantized transform coefficient; and generating a reconstructed picture based on the residual sample for the current block, wherein the residual information includes a context-based coded context syntax element, wherein the context syntax elements are decoded based on a maximum value of context-coded bins for the current block, and wherein the maximum value is determined by a unit of a transform block.