A Packet Loss Concealment Algorithm Robust to Burst Packet Loss for CELP-type Speech Coders

In this paper, a packet loss concealment (PLC) algorithm for CELP-type speech coders is proposed which improves the quality of decoded speech under burst packet loss conditions. The proposed PLC algorithm is based on the reconstruction of excitation by combining voiced excitation and random excitation, where the voice excitation is obtained from the adaptive codebook excitation scaled by a voicing probability and the random excitation is generated by permutating the previous decoded excitation. The voicing probability is estimated from the correlation using the decoded excitation and pitch of the previous frames. In addition, a linear regression-based gain amplitude is estimated and applied to the reconstructed excitation for the compensatation of the undesirable amplitude change under a burst packet loss condition. The proposed algorithm is implemented as a PLC algorithm for G.729 and its performance is compared with PLC employed in G.729 by means of perceptual evaluation of speech quality (PESQ), a waveform comparison, and an A-B preference test under random and burst packet loss rates of 3% and 5%. It is shown that the proposed algorithm provides significanlty better speech quality than the PLC of G.729, especially under burst packet losses.