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1. (WO2001003117) AUDIO CODING WITH ADAPTIVE LIFTERING

Pub. No.:    WO/2001/003117    International Application No.:    PCT/FR2000/001905
Publication Date: Fri Jan 12 00:59:59 CET 2001 International Filing Date: Wed Jul 05 01:59:59 CEST 2000
IPC: G10L 19/02
G10L 19/26
G10L 19/10
Applicants: MATRA NORTEL COMMUNICATIONS
CAPMAN, François
MURGIA, Carlo
Inventors: CAPMAN, François
MURGIA, Carlo
Title: AUDIO CODING WITH ADAPTIVE LIFTERING
Abstract:
The invention concerns a method wherein the encoder estimates a fundamental frequency (F0) of an audio signal, and determines a compressed higher envelope of the spectrum of the signal by interpolation of the spectral amplitudes associated with multiple frequencies of the fundamental frequency with application of a spectral compression function. It transforms the compressed higher envelope in the cepstral domain to obtain cepstral coefficients (cx_sup), and includes in a digital flow transmitted to the decoder quantization data of said cepstral coefficients. The cepstral coefficients are transformed by liftering in the cepstral domain before they are quantized. A value of the spectrum module of the audio signal is recalculated at at least multiple frequency of the fundamental frequency on the basis of the transformed cepstral coefficients (cx-sup q), and the liftering is adapted so as to minimise the module difference between the audio signal spectrum and at least a recalculated module value.