An enhanced two-stage multiple description video coder with drift reduction

Multiple description coding (MDC) is a source coding technique that exploits path diversity to increase the robustness of transmitting a compressed signal over error-prone channels. However, the application of MDC to video coding is still problematic because a prediction mismatch problem, called drift, may occur at the decoder when one description is lost. In the literature, it has been shown that drift can be effectively prevented by encoding this prediction mismatch and sending it as side information in a three-prediction-loop structure. However, this side information is totally redundant when both descriptions are received. We propose a very simple, but efficient two-stage MDC in the central prediction loop based on the three-prediction-loop structure of A. Reibman et al. (see Proc. IEEE Int. Conf. Image Processing - ICIP´99, p.837-41, 1999). We introduce an additional multiple description scalar quantizer into the central prediction loop. The encoding of the side information is modified in such a way that it can be used to improve the video quality when no drift occurs, but still maintain a drift prevention capability. The simulation results, with different video sequences at various packet loss rates, demonstrate that the proposed two-stage MDC structure indeed enhances the quality when the channel is error-free, yet effectively avoids drift when one description is completely lost.