Error propagation in motion compensated video over wireless channels

The use of multiple frames in block motion compensation (BMC) provides us with a new framework for increasing the robustness of video coders. We study the error robustness properties of multiframe BMC (MF-BMC) coders by modeling the error propagation process in the MF-BMC approach as a multiple Markov chain. Using Markov chain analysis we find that the probability of error propagation can decrease (i.e. robustness can increase) by (i) the use of additional frames in BMC, and by (ii) decreasing the probability with which blocks in the immediate previous frame are chosen for motion compensation. We outline a simple scheme that modifies the probabilities of macroblock prediction to achieve additional robustness. The MF-BMC coders proposed in this paper are a multiframe extension of the base level H.263 coder and are found to be more robust than the base level H.263 coder when subjected to simulated errors commonly encountered on wireless channels.