Patent ID: 6931373

Claim:
A frequency domain interpolative CODEC system for low bit rate coding of speech, comprising: a linear prediction (LP) front end adapted to process an input signal providing LP parameters which are quantized and encoded over predetermined intervals and used to compute a LP residual signal; an open loop pitch estimator adapted to process said LP residual signal, a pitch quantizer, and a pitch interpolator and provide a pitch contour within the predetermined intervals; and a signal processor responsive to said LP residual signal and the pitch contour and adapted to perform the following: provide a voicing measure, said voicing measure characterizing a degree of voicing of said input speech signal and is derived from several input parameters that are correlated to degrees of periodicity of the signal over the predetermined intervals; extract a prototype waveform (PW) from the LP residual and the open loop pitch contour for a number of equal sub-intervals within the predetermined intervals; normalize the PW by a gain value of said PW; encode a magnitude of said PW; and reconstruct a nonstationarity component of a PW phase at a decoder every subinterval using only a received PW magnitude, a stationary component of said PW, said voicing measure, a PW subband nonstationarity measure and a pitch frequency contour information; wherein a ratio is computed comparing the ratio of the energy of the nonstationarity component of the PW to that of the stationary component of the PW which is averaged over five PW subbands.