A Motion Vector Entropy Coding Scheme Based on Motion Field Referencing for Video Compression
Jingning Han, Jia Feng, Yun Tian Teng, Yaowu Xu, James Bankoski · 2018
Video codec exploits the temporal correlations in video signal through block-based motion compensated prediction. The motion vector associated with each prediction unit needs to be coded in the bit-stream. A differential coding scheme that employs the motion information from spatial neighbors and collocated blocks in the reference frames to predict the current motion vector is commonly used. Its efficacy is largely limited to track consistent or slow motion activities. A linear projection model is proposed in this work to create a motion field estimation that is capable to capture motion trajectory with high velocity. The resulting motion field motion vectors (MFMV) are fed into a dynamic motion vector referencing system as candidates in addition to those obtained from the spatial neighboring blocks. It allows the codec to closely track complex motion activities that the spatial neighbors or collocated motion vector referencing system usually fail to keep synchronized with. The MFMV system improves the prediction quality of the motion vectors and substantially reduces the energy in the difference motion vector for entropy coding, which translates into considerable compression performance improvements, especially for video sequences that contain complex motion activities. A number of design considerations to make the computation efficiency in both hardware and software platforms practical for production are discussed.