Channel and source considerations of a melp derived vocoder operating at reduced bit rates

Abstract

Robust low bit rate speech coders are essential in commercial and military communication Systems. They operate at fix bit rates and those bit rates can not be altered without majör modifications in the vocoder design. In this paper we introduce a Scaled Speech Coder, which operates on time-scale modified input speech. The proposed method offers any bit rate from 2,400 bits/s to downwards vvithout modifying the principle vocoder structure, which is the Mixed Excitation Linear Prediction (MELP) vocoder.