A study of design compromises for speech coders in packet networks
Rémi Lefebvre, Philippe Gournay, Redwan A. Salami · 2004
We present an objective and subjective comparison of alternative methods for improving the robustness of speech coders in packet networks. The two approaches are considered: 1) adding redundancy in the packets to improve the robustness of a baseline encoder; 2) reducing (or eliminating) inter-frame dependencies at the encoder. It is shown that both approaches have to trade bit rate and/or delay for quality over lossy channels. Formal subjective tests clearly show that, using relatively simple forward error correction methods, standard coders such as ITU-T recommendation G.729 can be made significantly more robust than "frame-independent" coders, at a lower or similar bit rate.