Patent ID: 6496797
Filing Date: 2002-12-17
Classification: G10L

Abstract:
An Analysis by Synthesis method for determining the spectral envelope information in speech coding systems based. on synthesizing a synthetic digital speech signal from a data structure produced by dividing an initial speech signal into a plurality of frames, determining a pitch frequency, determining voicing information, representing whether each of a plurality of frequency bands of each frame should be synthesized as voiced or unvoiced frequency bands, and processing the frames to determine spectral envelope information representative of the magnitudes of a spectrum in the frequency bands, wherein the method of determining the spectral envelope information comprises the steps of:a) forming a model set of the spectral magnitudes by assigning fixed values; b) synthesizing a model speech signal for the model set of the spectral magnitudes using both pitch frequencies and a set of voicing decisions determined for previous and current frames; c) calculating a spectrum of the model speech signal; d) approximating a spectrum of the initial speech signal by the spectrum of the model speech signal; and e) encoding coefficients obtained from the approximated spectrum.