Implementation of a Low Bit-Rate Vocoder

Abstract

: The main focus of this work will be an investigation of the implementation of a low bit-rate vocoder. By low bit-rate we mean a vocoder which has a bandwidth requirement of at most 3250 bits per second. The paper demonstrates a prototype Vocoder System near the bit rate of 4.05 kbps. In this Coding system, the optimum excitation signal is selected from a codebook (Codebook Sizes = 256) using perceptually weighted mean square error criterion and is applied to the cascade of two time-varying linear recursive filter called as Pitch Synthesis filter (related to pitch periodicity) and Formant Synthesis filter (spectral envelope)  for the construction of Synthetic Speech.