Adaptive pitch pulse enhancer and method for use in a codebook excited linear prediction (CELP) search loop

Abstract

An adaptive pitch pulse enhancer and method, adaptive to a voicing measure of input speech, for modifying the adaptive codebook of a CELP search loop to enhance the pitch pulse structure of the adaptive codebook. The adaptive pitch pulse enhancer determines a voicing measure of an input signal, the voicing measure being voiced when the input signal includes voiced speech and the voicing measure being unvoiced when the input signal does not include voiced speech, modifies a total excitation vector produced by the CELP search loop in accordance with the voicing measure of the input signal, and updates the adaptive codebook of the CELP search loop by storing the modified total excitation vector in the adaptive codebook.