Adaptive predictive coding of base-band speech signals

In this paper, a new quantization scheme for sub-band signals resulting from the QMF filter bank analysis of base-band signals in base-band vocoders is proposed. In the first part of the paper, the reference vocoder is briefly reminded. Then, a new quantizing scheme is proposed, which takes advantage of the short-term redundancy of the sub-band signals. Assuming that the QMF analysis is narrow enough, one can consider that, for voiced sounds, the pitch harmonics are well separated in the sense that they lie in separate sub-bands. This assumption allows to encode the sub-band signals with a second order adaptive predictor. The adaptation of the predictor coefficients is made sequentially both at the emitter and at the receiver, thus avoiding their transmission.