Estimation and mode decision for spatially correlated motion sequences

Abstract

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 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 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 framework and the results are encouraging.