Segment quantization for very-low-rate speech coding

Abstract

We introduce a new method for very-low-rate vocoding that the input speech as a sequence of variable-length segments. A segment is a by a spectrum of frames, where each frame is represented by a spectrum, pitch and gain. We use an automatic segmentation algorithm to obtain segments with an average duration comparable to that of a phoneme. A segment is quantized as a single block. The distance measure used for quantization incooporates the appropriate time alignment of two segments. We employ a computationally efficient metric that does not use the usual dynamic programming time warping. Two basic vocoders using the above approach of block quantization have been used to transmit intelligible speech at 200 b/s.