# US 11,909,987 B2 · Video coding method and device for avoiding small chroma block intra prediction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,987 B2 - Document ID: US11909987B2 - Status: Granted - Kind: B2 - Application number: 18/182,340 - Filed: 2023-03-12 - Published: 2023-07-06 - Granted: 2024-02-20 - Earliest claimed: 2019-09-16 - Assignees: Tencent America LLC - Applicants: Tencent America LLC - Inventors: Liang Zhao; Xiang Li; Xin Zhao; Shan Liu; Guichun Li; Xiaozhong Xu - Web page: https://patentgrep.com/patent/US11909987B2 ## CPC - H04N 19/103: Selection of coding mode or of prediction mode - H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction - H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks - H04N 19/157: Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter - 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 19/61: in combination with predictive coding - H04N 19/96: Tree coding, e.g. quad-tree coding - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A method for controlling block intra prediction is provided for a decoder. The method includes: obtaining a coded video bitstream; decoding, prediction information of a current coding unit (CU) in a segment of a current picture from the coded video bitstream; determining, according to the prediction information, a prediction type of a chroma coding block (CB) of the current CU, the prediction type being intra prediction or inter prediction; and reconstructing the chroma CB according to the prediction information, where a width of any reconstructed chroma CB intra-predicted from the coded video bitstream is greater than 2. ## Claims ### Claim 1 A method for controlling block intra prediction for an encoder, comprising: obtaining a video bitstream; encoding the video bitstream with prediction information of a current coding unit (CU) in a segment of a current picture, comprising: upon determining that the segment has a single tree structure indicating a same partitioning structure for both luma and chroma components of the segment, and that a prediction type of a chroma coding block (CB) of the current CU is intra prediction, including the prediction type of the chroma CB of the current CU in the prediction information, wherein when block area size of the chroma CB is smaller than or equal to a threshold T1, T1 being a positive integer, a luma component of the current CU is allowed to be sub-partitioned into multiple prediction units (PUs) for intra prediction, and a chroma component of the current CU only has one PU, a PU being a basic unit for prediction; and outputting the encoded video bitstream, wherein a width of any reconstructed chroma CB intra-predicted from the encoded video bitstream is greater than 2. ### Claim 2 (depends on 1) The method according to claim 1, wherein T1 is 16 or 32. ### Claim 3 (depends on 1) The method according to claim 1, wherein: when the current CU is a leaf node in the single tree structure for intra prediction, the prediction information includes an extended Intra Sub-Partition (ISP) signal indicating whether the current CU is sub-partitioned based on an extended ISP type, the extended ISP type including at least one of a binary tree split, a ternary tree split, or a quad tree split. ### Claim 4 (depends on 3) The method according to claim 3, wherein: each sub-partition of the current CU obtained based on the extended ISP type has an individual prediction mode. ### Claim 5 (depends on 3) The method according to claim 3, wherein when the current CU is sub-partitioned based on the extended ISP type, the prediction information includes a multiple transform set (MTS) flag and an MTS index for each sub-partition of the current CU. ### Claim 6 (depends on 3) The method according to claim 3, wherein when the current CU is sub-partitioned based on the extended ISP type, the prediction information includes a value indicating that Low Frequency Non-Separable Transform (LFNST) is not applied for the current CU at the decoder. ### Claim 7 (depends on 3) The method according to claim 3, wherein when a width of the current CU is not equal to a height of the current CU, the current CU is not allowed to be sub-partitioned based on the quad-tree split of the extended ISP type. ### Claim 8 (depends on 1) The method according to claim 1, wherein: when the segment has the single tree structure, a size of a transform unit of the current CU is equal to a size of the corresponding PU. ### Claim 9 (depends on 1) The method according to claim 1, wherein encoding the video bitstream with the prediction information further comprises: upon determining that a width of a luma CB of the current CU is less than or equal to 4 luma samples, or a width of the chroma CB of the current CU is less than or equal to 4 chroma samples, or the width and a height of the chroma CB of the current CU is less than or equal to 4 chroma samples, indicating, in the prediction information, that Combined Inter/Intra prediction (CIIP) mode is disabled for the current CU. ### Claim 10 (depends on 1) The method according to claim 1, wherein encoding the video bitstream with the prediction information further comprises: indicating, in the prediction information, that CIIP mode is enabled for a luma CB of the current CU and disabled for the chroma CB of the current CU upon determining that a width of the chroma CB of the current CU is less than or equal to 4 chroma samples, or the width or a height of the chroma CB of the current CU is less than or equal to 4 chroma samples. ### Claim 11 A method for controlling block intra prediction for an encoder, comprising: obtaining a video bitstream; encoding the video bitstream with prediction information of a current coding unit (CU) in a segment of a current picture, comprising: upon determining that the current CU belongs to a current Small Chroma Intra Prediction Unit (SCIPU) and a tree depth of the SCIPU is less than or equal to a threshold T2, and that the prediction type of the chroma CB is intra prediction, including the prediction type of the chroma CB in the prediction information, a SCIPU being a coding tree node whose chroma CB size is larger than or equal to TH chroma samples and has at least one child luma CB whose size is smaller than 4TH luma samples, and T2 being 1 or 2; and outputting the encoded video bitstream, wherein a width of any reconstructed chroma CB intra-predicted from the encoded video bitstream is greater than 2. ### Claim 12 (depends on 11) The method according to claim 11, wherein all CUs in the current SCIPU region are intra-coded CU. ### Claim 13 A method for controlling block intra prediction for an encoder, comprising: obtaining a video bitstream; encoding the video bitstream with prediction information of a current coding unit (CU) in a segment of a current picture, comprising: upon determining that the segment has a dual tree structure indicating separate partitioning structures for luma and chroma components of the segment, and that the prediction type of the segment is intra prediction, including the prediction type of the segment and a variable MinCbLog2SizeC in the prediction information, the variable MinCbLog2SizeC indicating a binary logarithmic value of a minimum size of the chroma CB of the current CU; and outputting the encoded video bitstream, wherein a width of any reconstructed chroma CB intra-predicted from the coded video bitstream is greater than 2. ### Claim 14 (depends on 13) The method according to claim 13, wherein the variable MinCbLog2SizeC is derived by: a higher value of 2 and a difference value between a minimum luma coding block size MinCbLog2SizeY and a horizontal chroma sub-sampling factor based on color format ChromaShiftHor; the ChromaShiftHor being defined based on the table below: Chroma format ChromaShiftHor Monochrome 0 4:2:0 1 4:2:2 1 4:4:4 0. ### Claim 15 (depends on 13) The method according to claim 13, wherein the variable MinCbLog2SizeC is derived by: a higher value of 2 and a difference value between the minimum luma coding block size MinCbLog2SizeY and a vertical chroma sub-sampling factor based on color format ChromaShiftVer, the ChromaShiftVer being defined based on the table below: Chroma format ChromaShiftVer Monochrome 0 4:2:0 1 4:2:2 0 4:4:4 0. ### Claim 16 (depends on 13) The method according to claim 13, wherein encoding the video bitstream with the prediction information further comprises: upon determining that a width of a luma CB of the current CU is less than or equal to 4 luma samples, or a width of the chroma CB of the current CU is less than or equal to 4 chroma samples, or the width and a height of the chroma CB of the current CU is less than or equal to 4 chroma samples, indicating, in the prediction information, that Combined Inter/Intra prediction (CIIP) mode is disabled for the current CU. ### Claim 17 (depends on 13) The method according to claim 13, wherein encoding the video bitstream with the prediction information further comprises: indicating, in the prediction information, that CIIP mode is enabled for a luma CB of the current CU and disabled for the chroma CB of the current CU upon determining that a width of the chroma CB of the current CU is less than or equal to 4 chroma samples, or the width or a height of the chroma CB of the current CU is less than or equal to 4 chroma samples.