Rate-constrained hierarchical grid interpolation for object-based motion compensation

In this paper, we propose a rate-constrained object-based hierarchical motion compensation technique, by extending the hierarchical grid interpolation (HGI) technique. First, the HGI technique is extended to the object-based HGI (OHGI), in order to cope with the object-based motion compensation (MC). By noting that the HGI does not exploit the rate-distortion (R-D) trade-off inherent in the quadtree segmentation, we employ the greedy algorithm to achieve the improved performance in the R-D sense. Also, attempts are made to alleviate the computational complexity relating to the proposed technique, while degrading the performance slightly. Intensive computer simulation is performed, using three different MPEG-4 test sequences, to evaluate the performance of the proposed technique in the R-D sense. In comparison with the OHGI technique as well as the polygon matching, which is an object-based MC technique adopted in MPEG-4, the proposed technique provides better R-D performance; it yields higher PSNRs at the same bit rate, by about 1.0-1.9 dB, depending on the sequences.