# US 11,445,184 B2 · Image decoding method and device for deriving weight index information for generation of prediction sample > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,445,184 B2 - Document ID: US11445184B2 - Status: Granted - Kind: B2 - Application number: 17/550,476 - Filed: 2021-12-14 - Published: 2022-03-31 - Granted: 2022-09-13 - Earliest claimed: 2019-06-14 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Naeri Park; Junghak Nam; Hyeongmoon Jang - Web page: https://patentgrep.com/patent/US11445184B2 ## CPC - H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction - H04N 19/52: by predictive encoding - 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 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/54: using feature points or meshes - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract According to the disclosure of the present document, when the inter prediction type of a current block indicates bi-prediction, weight index information for candidates in a merge candidate list or a sub-block merge candidate list can be derived, and thus coding efficiency can be increased. ## Claims ### Claim 1 An image decoding method performed by a decoding apparatus, the method comprising: receiving image information comprising inter prediction mode information through a bitstream; generating a merge candidate list for a current block based on the inter prediction mode information; deriving motion information on the current block based on a candidate selected from among candidates in the merge candidate list; generating L0 prediction samples and L1 prediction samples of the current block based on the motion information; and generating prediction samples of the current block based on the L0 prediction samples, the L1 prediction samples, and a weight index for the current block, wherein the weight index is derived based on a weight index for the selected candidate, wherein the candidates comprise a constructed affine merge candidate, and the constructed affine merge candidate comprises control point motion vectors (CPMVs), wherein based on a case that the constructed affine merge candidate comprises a CPMV0 for a control point 0 (CP0), a weight index for the constructed affine merge candidate is set equal to a weight index for the CP0, wherein the CP0 is related to a top-left corner of the current block, and wherein based on a case that the constructed affine merge candidate does not comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to a weight index for the CP1, wherein the CP1 is related to a top-right corner of the current block. ### Claim 2 (depends on 1) The image decoding method of claim 1, wherein the weight index for the CP0 is equal to a weight index for a block that is used for deriving the CPMV0 among neighboring blocks of the CP0, and wherein the neighboring blocks of the CP0 comprises a top-left corner neighboring block of the current block, a left neighboring block adjacent to a bottom side of the top-left corner neighboring block, and a top neighboring block adjacent to a right side of the top-left corner neighboring block. ### Claim 3 (depends on 1) The image decoding method of claim 1, wherein the weight index for the CP1 is equal to a weight index for a block that is used for deriving the CPMV1 among neighboring blocks of the CP1, and wherein the neighboring blocks of the CP1 comprise a top-right corner neighboring block of the current block and a top neighboring block adjacent to a left side of the top-right corner neighboring block. ### Claim 4 (depends on 1) The image decoding method of claim 1, wherein the candidates comprise a sub-block-based temporal motion vector prediction (SbTMVP) candidate, and wherein a weight index for the SbTMVP candidate is derived based on a weight index for a left neighboring block of the current block. ### Claim 5 (depends on 1) The image decoding method of claim 1, wherein the candidates comprise a sub-block-based temporal motion vector prediction (SbTMVP) candidate, and wherein a weight index for the SbTMVP candidate is derived as 0. ### Claim 6 (depends on 1) The image decoding method of claim 1, wherein the candidates comprise a sub-block-based temporal motion vector prediction (SbTMVP) candidate, wherein a weight index for the SbTMVP candidate is derived based on a weight index for a center block in a collocated block, wherein the collocated block comprises a block at a same position as a position of the current block in a reference picture different from a current picture in which the current block is positioned, and wherein the center block comprises a bottom-right sub-block among four sub-blocks positioned in a central area of the collocated block. ### Claim 7 (depends on 1) The image decoding method of claim 1, wherein based on the case that the constructed affine merge candidate comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to the weight index for the CP0 regardless of the weight index for the CP1 and a weight index for a control point 2 (CP2), wherein the CP2 is related to a bottom-left corner of the current block. ### Claim 8 (depends on 1) The image decoding method of claim 1, wherein based on the case that the constructed affine merge candidate comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to the weight index for the CP0 without comparing the weight index for the CP0 to the weight index for the CP1 or a weight index for a control point 2 (CP2), wherein the CP2 is related to a bottom-left corner of the current block. ### Claim 9 An image encoding method performed by an encoding apparatus, the method comprising: determining an inter prediction mode of a current block and generating inter prediction mode information indicating the inter prediction mode; generating a merge candidate list for the current block based on the inter prediction mode; generating selection information indicating one candidate among candidates included in the merge candidate list; and encoding image information comprising the inter prediction mode information and the selection information, wherein the candidates comprise a constructed affine merge candidate, and the constructed affine merge candidate comprises control point motion vectors (CPMVs), wherein based on a case that the constructed affine merge candidate comprises CPMV0 for a control point 0 (CP0), a weight index for the constructed affine merge candidate is set equal to a weight index for the CP0, wherein the CP0 is related to a top-left corner of the current block, and wherein based on a case that the constructed affine merge candidate does not comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to a weight index for a control point 1 (CP1), wherein the CP1 is related to a top-right corner of the current block. ### Claim 10 (depends on 9) The image encoding method of claim 9, wherein based on the case that the constructed affine merge candidate comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to the weight index for the CP0 regardless of the weight index for the CP1 and a weight index for a control point 2 (CP2), wherein the CP2 is related to a bottom-left corner of the current block. ### Claim 11 (depends on 9) The image encoding method of claim 9, wherein based on the case that the constructed affine merge candidate comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to the weight index for the CP0 without comparing the weight index for the CP0 to the weight index for the CP1 or a weight index for a control point 2 (CP2), wherein the CP2 is related to a bottom-left corner of the current block. ### Claim 12 A non-transitory computer readable digital storage medium storing a bitstream generated by an image encoding method, the method comprising: determining an inter prediction mode of a current block and generating inter prediction mode information indicating the inter prediction mode; generating a merge candidate list for the current block based on the inter prediction mode; generating selection information indicating one candidate among candidates included in the merge candidate list; and encoding image information to generate the bitstream, wherein the image information comprises the inter prediction mode information and the selection information, wherein the candidates comprise a constructed affine merge candidate, and the constructed affine merge candidate comprises control point motion vectors (CPMVs), wherein based on a case that the constructed affine merge candidate comprises CPMV0 for a control point 0 (CP0), a weight index for the constructed affine merge candidate is set equal to a weight index for the CP0, wherein the CP0 is related to a top-left corner of the current block, and wherein based on a case that the constructed affine merge candidate does not comprise the CPMV0 for the CP0, the weight index for the constructed affine merge candidate is set equal to a weight index for a control point 1 (CP1), wherein the CP1 is related to a top-right corner of the current block.