MOTION OPTIMIZATION OF ORDERED BLOCKS FOR OVERLAPPED BLOCK MOTION COMPENSATION

While overlapped block motion compensation (OBMC) [1]-[3] with block m atching motion vectors yields better estimation accuracy than standard block matching, these estimates may be significantly improved by opti mizing the motion vectors, Optimal motion vectors may be determined by an iterative and computationally intensive process, However, for a lo w-cost system (e,g,, videoconferencing [4]), such an approach is not f easible, An analysis of the compensation errors after motion optimizat ion reveals that most gains in estimation accuracy result from the opt imization of a fraction of the total number of blocks in a frame, It i s thus conceivable that, by defining suitable ordering algorithms for blocks, coding systems could see improved performance by optimizing so me number of blocks based on the ordering depending on available compu tational resources, In this paper, with the aid of simulations we firs t show that most improvements by optimizing motion are limited to a fe w motion vectors, Then we present simple and intuitive algorithms base d on compensation error after OBMC with block matching vectors to orde r blocks, Simulation results using these algorithms for ordering and o ptimizing motion are presented for two video sequences, The results re veal improvements obtained by optimizing motion of blocks from the ord ering are reasonable; however, the improvements are not limited to the first fraction of blocks from the ordering, suggesting that better or dering algorithms be investigated in the future.