PACKETIZED SPEECH QUALITY IMPROVEMENT WITH BANDWIDTH EXPANSION APPROACH

Abstract

Speech packets can be corrupted while travelling through a transmission medium. The corruption of packet causes quality impairments. Speech quality, coded at low bit rates, is rated below excellent quality. Therefore, additional loss of packets further causes degradation in speech quality. There are lost frame reconstruction techniques through which the effects of lost and corrupted packets, on speech quality can be mitigated. Bandwidth expansion is one of the approaches applied upon Linear Prediction Coding (LPC) based packetization to improve speech quality. In this paper, a Codebook Excitation Linear Prediction (CELP) system of 4.3 kb/s speech is packetized and a random packet loss phenomenon is simulated. The lost packets are reconstructed by pitch filter and LPC filter with bandwidth expansion of LPC coefficients. The simulation results for various loss rates and corresponding speech quality measures are presented with Mean Opinion Scores (MOS). It has been observed that with bandwidth expansion, quality is improved over without bandwidth expansion schemes in similar scenario.