US 12,445,614 B2
Adaptive context-based adaptive binary arithmetic coding (CABAC) initial state selection from coded pictures
Xiaozhong Xu, State College, PA (US); and Shan Liu, San Jose, CA (US)
Assigned to Tencent America LLC, Palo Alto, CA (US)
Filed by Tencent America LLC, Palo Alto, CA (US)
Filed on Nov. 11, 2022, as Appl. No. 17/985,809.
Claims priority of provisional application 63/307,522, filed on Feb. 7, 2022.
Prior Publication US 2023/0254489 A1, Aug. 10, 2023
Int. Cl. H04N 19/13 (2014.01); H04N 19/105 (2014.01); H04N 19/169 (2014.01); H04N 19/172 (2014.01); H04N 19/70 (2014.01); H04N 19/91 (2014.01)
CPC H04N 19/13 (2014.11) [H04N 19/105 (2014.11); H04N 19/172 (2014.11); H04N 19/1883 (2014.11); H04N 19/70 (2014.11); H04N 19/91 (2014.11)] 12 Claims
OG exemplary drawing
 
1. A method of decoding in a decoder, comprising:
receiving a video bitstream including a current picture and a previous picture, wherein the previous picture comprises multiple regions, each region of the multiple regions in the previous picture being entropy coded, the multiple regions in the previous picture including coding tree units (CTUs) located at four corners and a center of the previous picture, respectively, the current picture including four corner regions and a center region;
determining previous probability information associated with each region of the multiple regions in the previous picture, the previous probability information being determined with a second quantization precision;
storing the previous probability information with a first quantization precision that is lower than the second quantization precision, the first quantization precision having less bits than the second quantization precision;
selecting, based on a location of an independently decodable coding segment that is a region in the current picture, one of the multiple regions in the previous picture by one of:
selecting a CTU located at one of the four corners of the previous picture when a block in the independently decodable coding segment is located at one of the four corner regions of the current picture, the CTU located at the one of the four corners being in the selected one of the multiple regions, and
selecting a CTU located at the center of the previous picture when the block in the independently decodable coding segment is located at the center region in the current picture, the CTU located at the center being in the selected one of the multiple regions;
determining initial probability information for entropy decoding one or more current syntax elements of the block in the independently decodable coding segment in the current picture based on the stored previous probability information that has the first quantization precision and is associated with the selected one of the multiple regions in the previous picture, the one or more current syntax elements being first to be entropy decoded among syntax elements in the independently decodable coding segment in the current picture; and
entropy decoding coded bits associated with the one or more current syntax elements into a bin string associated with the one or more current syntax elements based on the initial probability information and a probability estimation model for the coded bits, wherein
a flag in the video bitstream indicates that the initial probability information is to be determined based on the stored previous probability information from the previous picture.