Estimation and mode decision for spatially correlated motion sequences
There are several parts of the video-encoding process that can be optimized for high quality, high compression ratio, and fast encoding speed. We focus on some of these encoder optimization issues. We first study motion estimation, a computationally intensive part of encoding, and propose efficient algorithms based on exploiting spatially correlated motion information. We extend our motion estimation algorithms to find motion vectors for sub-parts of a block, as allowed for in the H.263 and MPEG-4 standards, and propose an efficient two-tier decision strategy for the one-four motion-vector decision. We introduce a new measure of block similarity that can improve the inter-intra mode decision significantly. Furthermore, for certain motion-estimation strategies, this new measure can also improve the bit rate resulting from a better motion estimation. Another issue that we address is the estimation of delta motion vectors in the H.263 and MPEG-4 standards. We have implemented these optimizations in a H.263 framework and the results are encouraging.