Block Partitioning Structure in the VVC Standard

• Published in: IEEE transactions on circuits and systems for video technology Vol. 31; no. 10; pp. 3818 - 3833
• Main Authors: Huang, Yu-Wen, An, Jicheng, Huang, Han, Li, Xiang, Hsiang, Shih-Ta, Zhang, Kai, Gao, Han, Ma, Jackie, Chubach, Olena
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: binary tree; Block partitioning structure; Coding; Coding standards; Copper; CTU dual tree; Encoding; H.266; Indexes; ISO Standards; Lead; local dual tree; MPEG-I Part 3; multi-type tree; Partitioning; picture boundary handling; quaternary tree; ternary tree; Transform coding; versatile video coding; Video compression; virtual pipeline data unit; VVC
• ISSN: 1051-8215; 1558-2205
• DOI: 10.1109/TCSVT.2021.3088134

Versatile Video Coding (VVC) is the latest video coding standard jointly developed by ITU-T VCEG and ISO/IEC MPEG. In this paper, technical details and experimental results for the VVC block partitioning structure are provided. Among all the new technical aspects of VVC, the block partitioning structure is identified as one of the most substantial changes relative to the previous video coding standards and provides the most significant coding gains. The new partitioning structure is designed using a more flexible scheme. Each coding tree unit (CTU) is either treated as one coding unit or split into multiple coding units by one or more recursive quaternary tree partitions followed by one or more recursive multi-type tree splits. The latter can be horizontal binary tree split, vertical binary tree split, horizontal ternary tree split, or vertical ternary tree split. A CTU dual tree for intra-coded slices is described on top of the new block partitioning structure, allowing separate coding trees for luma and chroma. Also, a new way of handling picture boundaries is presented. Additionally, to reduce hardware decoder complexity, virtual pipeline data unit constraints are introduced, which forbid certain multi-type tree splits. Finally, a local dual tree is described, which reduces the number of small chroma intra blocks.