Adaptive schemes for motion-compensated coding

Several variations on the popular motion-compensated interframe block-coding schemes are proposed. The idea behind these schemes is to handle each image block with a different parameter and/or algorithm based on the contents of that individual block. They are extensions of the basic nonadaptive algorithm and are designed to reduce the coding bit rate and to improve the reconstructed picture quality. Our goal in this paper is to explore the potential merits offered by these adaptive techniques. Three schemes are described in this paper: (1) adaptive block-size motion compensation and coding, (2) multiple-transform coding, and (3) DCT and cluster (pel-domain) hybrid coding. Similar to many other adaptive algorithms, each of the above schemes has a number of parameters that need to be chosen carefully for optimum performance. We make no such exhaustive attempt, rather the results presented here are based on a limited set of experiments using a few preselected parameters. However, we find that the experiments conducted still provide us with some insights into issues concerning the adaptive image-sequence coding schemes, such as, the performance versus complexity issue.