TIME ENCODING OF LPC ROOTS

Since the formants in human speech move slowly over time, their slow time-varying behavior provides a source of information redundancy which can be used to reduce the required data rate in encoding of speech. In the present invention, speech is encoded by an adaptive tracking procedure, which follows the time-varying behavior of the speech parameters (e.g. the roots of the LPC inverse filter) with a minimum bit rate. A sequence of frames of parameters is segmented into locally-smooth segments which are approximated by higher-order orthogonal functions, and the required best-fit approximation order and coefficients are encoded.