Multi-directional skip and direct modes design in bi-predictive slices for AVS2 standard

The second generation of Audio-video coding standard (AVS2) part 2 has obtained an outstanding compressing performance by a series of advanced technologies, e.g. flexible partition structure and high efficient prediction methods, etc. However, it is observed that there is still substantial motion information redundancy between spatial adjacent blocks. Therefore, this paper introduces a technique named Multi-directional SKIP and DIRECT modes (MDSD) to ameliorate SKIP/DIRECT mode to adapt to the features of block motion. Based on the study of the correlation between spatial adjacent blocks with the same or different motion models, a priority-based motion information derivation method is designed. A higher priority is assigned to the motion information of neighboring blocks with the same motion model as current block. Experiments in AVS2 reference software RD3.0 show improvements of up to 3.9% in BD rate reduction are achieved.