A 2400 bps vocoder based on mixed excitation linear prediction and channel coding

To obtain high quality synthetic speech at 2400 bps, this paper presents a vocoder based on the Mixed Excitation Linear Prediction (MELP) model. The differences of the vocoder parameters are analyzed, and an unequal error protection channel coding and a parameter substitution method for error frame are proposed to improve the robustness over random error channel. Several channel coding schemes are compared and the optimal one is then selected. Test results show that the proposed speech coding algorithm could provide satisfactory speech quality and strong robustness against channel errors.