Diverse Subblock-Level Motion Derivation Schemes for AVS3

AVS3 is the third generation audio video coding standard (AVS) developed by the AVS working group from 2018 and its base profile achieves roughly 20% bit rate saving compared to H.265/HEVC. In this paper, two subblock-level motion derivation methods, including enhanced temporal motion vector prediction (ETMVP) and planar mode based motion vector prediction (PMMVP), are proposed to diversify the motion derivation scheme and enhance the prediction efficiency of skip/direct mode in the AVS3 structure. Different from the traditional temporal motion vector prediction (TMVP), subblock-level motion vectors in ETMVP are derived by combining the traditional TMVP and motion vector difference predictor (MVDP). In PMMVP, the motion of each subblock is generated by interpolation from spatially neighboring blocks in a manner of intra planar mode. The newly introduced motions are developed as the additional motion candidates in skip/direct mode. The proposed method is implemented on top of the AVS3 reference software (HPM-3.2), and the experimental result shows that a 1.65% BD-rate reduction (up to -3.13%) is achieved under Random Access configuration.