SPEECH CODER USING PHASE EQUALIZATION AND VECTOR QUANTIZATION.

A speech processing and coding method is proposed which makes use of perceptual redundancy for slowly varying short-time phase characteristics. The method uses waveform conversion through a phase-equalizing filter, which is based on a time-domain matched filter for the residue of linear predictive coding (LPC). Phase-equalized speech is found to be almost perceptually equivalent and to be efficiently encoded by a two-stage quantization. The proposed coder is proved to be superior to other coders in terms of both SNR and subjective quality. The averaged subjective quality at 9. 6 kb/s is comparable to that of a 6-bit low PCM.