Loss Concealments for Low Bit-Rate Packet Voice in Voice over IP

In recent years, voice over IP has become an attractive alternative to conventional public telephony. However, the Internet is a best-effort network, with no guarantee on its quality of service. A fundamental issue in real-time interactive voice transmissions over an unreliable Internet protocol network is packet loss. This problem is especially serious in transmitting low-bit-rate coded speech in which pervasive dependencies are introduced in a bit stream, leading to error propagation to subsequent frames when loss happens. In this talk, we survey existing work in the area and present an end-to-end loss-concealment scheme that requires no special support from the underlying network. In particular, we focus on developing a non-redundant sender-receiver collaborated multiple-description coding (MDC) scheme. We propose a new coder-dependent parameter-based MDC that generates multiple descriptions systematically based on correlations of coding parameters. The design is done in such a way that requires no extra transmission bandwidth and that adapts its number of descriptions to network loss conditions. Extensive tests on FS CELP, ITU G.723.1, FS MELP, and G.729 for different loss scenarios demonstrate the high quality and reliability of our proposed scheme.