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. In this paper, we focus on some of these encoder optimization issues. We first stu dy motion estimation, a computationally intensive part of encoding, and pro pose efficient algorithms based on exploiting spatially correlated motion i nformation. We extend our motion-estimation algorithms to find motion vecto rs for sub-parts of a block, as allowed for in the H.263 and MPEG-4 standar ds, and propose an efficient two-tier decision strategy for the one-four mo tion-vector decision. We introduce a new measure of block similarity that c an improve the inter-intra mode decision significantly. Furthermore, for ce rtain motion-estimation strategies, this new measure can also improve the b it rate resulting from a better motion estimation. Another issue that we ad dress in this paper is the estimation of delta motion vectors in the H.263 and MPEG-4 standards. We have implemented these optimizations in a H.263 fr amework and the results are encouraging.