Patent ID: 6691092
Filing Date: 2004-02-10
Classification: G10L

Abstract:
A frequency domain interpolative coding system for low bit-rate coding of speech signals, comprising:a linear prediction (LP) front end, responsive to an input signal, providing LP parameters which are quantized and encoded over predetermined intervals and used to compute a LP residual; an open loop pitch estimator, responsive to said LP residual signal, a pitch quantizer, and a pitch interpolator yielding a pitch contour within the predetermined interval; a voice activity detector (VAD) mechanism responsive to said LP parameters and open loop pitch, generating a VAD flag for every predetermined interval; a signal processor responsive to said LP residual signal and the pitch contour for extracting a prototype waveform (PW) for a number of equal sub-intervals within the predetermined interval; and said signal processor computing a PW gain for generating a normalized PW for each sub-interval and a PW gain vector for the predetermined interval; a separation of the normalized PW into a slowly evolving waveform (SEW) component and a rapidly evolving waveform (REW) component using a low-pass filter along every pitch harmonic track; a representation of one or more of the components of the normalized PW in spectral magnitude-phase form; and a characterization of the degree of periodicity of the input signal by a voicing measure, derived from certain parameters that are correlated to signal periodicity and computed from the input signal, PW, SEW and REW over the predetermined interval.