Adapting quantization offset in multiple description coding for error resilient video transmission

Multiple description coding (MDC) provides an excellent error resilient approach for transmitting video over wireless ad hoc networks. In this paper, we propose an improvement to this scheme by jointly selecting the quantization offsets in different paths to achieve the best overall video quality at the decoder. The statistical distribution of the transform coefficients in the encoded video sequence is parameterized using a Laplacian model. The optimal offset values are computed by solving a multi-level optimization problem based on the statistics of the transform coefficients and the individual path failure probabilities. In order to reduce the computational complexity, the encoding modes for the motion vectors and transform coefficients are collected in the first step. In the second step, the model parameter is calculated from the transform coefficients and the offset search is performed when the model parameter between frames deviates beyond the pre-set threshold. In the final step, the stored modes and the respective offset values are directly used for encoding the two bit streams. The simulation results using H.264/AVC system confirm the advantages of the proposed approach under different packet loss conditions.