Two asymmetric descriptions from many symmetric descriptions

Multiple descriptions provide a mechanism for graceful degradation in open-loop lossy source coding over a lossy-packet network. Two well understood extreme cases are successive refinement (fully asymmetric) and symmetric descriptions. Existing solutions for the general asymmetric case are, however, cumbersome. We present a framework for designing an efficient asymmetric two-description scheme, based on dividing many symmetric descriptions into two groups, and encoding each group jointly. Using this framework, we present a sum-rate optimal solution based on oversampling and dithered delta-sigma quantization, which was previously applicable only for the symmetric descriptions case.