Fast Algorithm Based on Non-first Pre-coding Skip for AVS3 Intra Coding

The third generation of Audio Video coding Standard (AVS3) adopts multi-type tree, including Quad-Tree (QT), Binary-Tree (BT) plus Extend Quad-Tree (EQT), partition structure. During multi-type tree recursive pre-coding process of encoding, each Coding Units (CU) of each Size at each Location (CUeSeL) of the picture is repeatedly pre-coded many times when visiting each branch of each tree. Although there is early termination mechanism, the number of visit for each CUeSeL is still very high and up to more than twenty. This process brings very high coding complexity. To reduce the coding complexity of AVS3, this paper proposes a method named non-first pre-coding skip (NFPS) for CUeSeL. The contributions of the paper are as follows. In I picture, for a CU with top-left location (x, y), if both x and y are multiples of 64, then each non-first pre-coding is skipped and the coding result of the first pre-coding is reused for each non-first pre-coding. In non-I picture, for a CU with top-left location (x, y), if both x and y are multiples of 64 and a set of conditions is satisfied, then each non-first pre-coding is skipped and the coding result of the first pre-coding is reused for each non-first pre-coding. The experimental results demonstrate that NFPS has a negligible impact on coding efficiency under All intra (AI), Low Delay B (LDB), Random Access (RA) configurations, and coding runtime is reduced by 6% for AI and almost not changed for LDB and RA.