Abstract: In video coding at high compression rates, e.g., in very low bit rate coding, every transmitted bit carries a significant amount of information that is related either to motion parameters or to intensity residual. As demonstrated in the SIM-3 coding scheme, a more precise motion model leads to improved quality of coded images when compared with the H.261 coding standard. In this paper, we present some of our recent results on the modeling and estimation of motion of the compression and post-processing of typical videophone ('head-and- shoulders') image sequences. We describe a block-based motion estimation that attempts to optimize the overall bit budget for intensity residual, motion and overhead information. We compare simulation results for this scheme with full-search block matching in the context of the H.261 coding. Then, we discuss a region-based motion estimation that exploits segmentation maps obtained from an MDL-based (minimum description length) algorithm. We compare experimentally several algorithms for the compression of such maps. Finally, we describe motion-compensated interpolation that takes into account pixel acceleration. We show experimentally a major performance improvement of the constant- acceleration model over the usual constant-velocity models. This is a very promising technique for post-processing in the receiver to improve reconstruction of frames dropped in the transmitter.!25
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