Speech coding based on adaptive mel-cepstral analysis

We propose an ADPCM coder which uses a backward adaptive predictor based on the adaptive mel-cepstral analysis. The spectrum represented by the mel-cepstral coefficients has frequency resolution similar to that of the human ear which has high resolution at low frequencies. In the coder, since the transfer functions of noise shaping and postfiltering are also defined through the mel-cepstral coefficients, the effects of nose shaping and postfiltering should fit with characteristics of the human auditory sensation. We incorporate a pitch predictor into the ADPCM coder, and evaluate the speech quality based on objective and subjective performance tests. It is shown that the coder at 16 kb/s can produce a high quality speech comparable with that of the CCITT G.721 ADPCM coder at 32 kb/s with no algorithmic delay