Research On MELP Based Very Low Bit Rate Speech Coding Algorithm

In the speech coding algorithms, the Mixed Excitation Linear Prediction(MELP) algorithm can do better in imitate the natural speech characteristic to synthesize high quality speech in the low bit rate, so it become one of the most potential algorithms in the modern low bit rate speech coding. Based on MELP, several speech coding parameters, such as the pitch, gain, Fourier magnitudes, Unvoice/Voice judgement, LSF and so on, are analyzed in this paper, the selection, extraction and quantization methods of the parameters in very low bit rate speech coding algorithm are discussed. With these techniques, the very low bit speech coding algorithm at 1.2kb/s is designed and implemented,3-level vector quantization, multi-frame joint and parameter interpolating are proposed to reduce speech coding bit rate, and its performance is also evaluated in the paper. Informal subjective listening tests show that the speech quality of 1.2kb/s coding algorithm achieves high intelligibility, clearness, and relative naturalness.