PACKETIZED SPEECH QUALITY IMPROVEMENT BY POST-PITCH FILTERING APPROCH

Abstract

In packetized speech communication, speech packets can be corrupted due to noise or can be lost due to transmission delay. These packets cause speech quality degradation. For low bit rate speech, lost packets problem is severe, because speech coded at low bit rates is already sacrificed over bit rates reduction to save bandwidth and quality loss due to the limitation and coding algorithm limitations. Post-pitch filtering is an approach by which the effects of lost packet can be mitigated. In this paper, a Codebook Excited Linear Prediction (ECLP) system of 4.3 kb/s speech is packetized and a random packet loss phenomenon is simulated. The lost packets are reconstructed by a cascaded response of post-pitch filter and LPC filter. In this paper the simulation results for various packet loss rates and corresponding speech quality measures are presented.