Decoder Side Motion Vector Refinement for Versatile Video Coding

Han Gao, Semih Esenlik, Zhijie Zhao, Eckehard G. Steinbach, Jianle Chen

Abstract: Inter picture prediction is an essential component of today's hybrid video codecs. In order to reduce the bitrate required for motion vector (MV) signaling, the High Efficiency Video Coding (HEVC) standard and the latest Versatile Video Coding (VVC) draft utilize a merge mode to signal the MV. While the merge mode saves the bits for MV indication, it generates inaccurate MVs, which lead to imprecise prediction. To improve the coding performance, novel decoder side motion vector refinement (DMVR) schemes are currently being proposed. The DMVR approach refines the initial MV from the merge mode by searching the block with the smallest matching cost in the previous decoded reference pictures. We present two variants of block matching-based DMVR, namely template matching and bilateral matching. Experimental results obtained with the VTM-2.0 reference software, after integrating our approaches, demonstrate that our proposed methods provide an average luma BD-rate reduction of 4.71% for the template matching-based DMVR and 4.92% for the bilateral matching-based DMVR when using the random access configuration.