Predictive motion field segmentation for image sequence coding

A method is described for improving block-based motion-compensation techniques by segmenting blocks into regions corresponding to objects moving with distinct velocities. The method uses standard block motion-estimation techniques and assumes that each distinct velocity within a block is approximated by one of the motion estimates in a neighborhood of that block. A multiresolution approach to segmenting each block is taken. It is based on a Markov random-field model of the segmentation field and incorporates additional constraints which reflect an assumption that the blocks are small relative to objects in the scene. In order to avoid transmitting the segmentation, the method computes the segmentation of previous frames at the receiver and transmitter and predicts the current segmentation from past ones. Experimental results show that the method eliminates most artifacts due to block motion compensation at edges of moving objects and achieves 30-50% reductions in displaced frame-difference energy in frames where reliable motion estimates are available