Unbalanced Quantized Multiple Description Video Transmission using Path Diversity

Multiple Description Coding is a forward error correction scheme where two or more descriptions of the source are sent to the receiver over different channels. If only one channel is received the signal can be reconstructed with distortion D1 or D2. On the other hand, if both channels are received the combined information is used to achieve a lower distortion D0. Our approach is based on the Multiple State Video Coding with the novelty that we achieve a flexible unbalance rate of the two streams by varying the quantization step size while keeping the original frame rate constant. The total bitrate RT is fixed which is to be allocated between the two streams. If the assigned bitrates are not balanced there will be PSNR (peak signal to noise ratio) variations between neighbouring frames after reconstruction. Our goal is to find the optimal rate allocation while maximizing the average reconstructed frame PSNR and minimizing the PSNR variations given the total bitrate RT and the packet loss probabilities p1 and p2 over the two paths. The reconstruction algorithm is also taken into account in the optimization process. The paper will report results presenting optimal system designs for balanced (equal packet loss probabilities) but also for unbalanced path conditions (different packet loss probabilities).