Enhanced motion list reordering for video coding

In video coding, motion information consisting of motion vectors and reference index is typically involved in motion compensation. Motion list is widely used to efficiently compress the motion information, in which a motion index indicating the motion information is signaled. And the compression efficiency can be improved by template matching based motion list reordering. Besides, the motion information is further refined before being used in motion compensation by motion refinement process such as decoder-side motion vector refinement and template matching. However, the original motion information of the motion list rather than the refined motion information is used in the motion list reordering, which limits the coding performance. Therefore, an enhanced motion list reordering (EMLR) approach is proposed in this paper, in which the refined motion information is used in the motion list reordering. To derive the refined motion information, a dedicated motion refinement with a simplified version of motion refinement process is proposed. Furthermore, a simplified version of EMLR with two fast algorithms (EMLR-S) is proposed. Experimental results demonstrate that EMLR can achieve 0.19% BD-rate saving on average, and EMLR-S can achieve 0.1 % BD-rate saving with negligible coding complexity change compared to ECM-4.0 under random access configuration.