Study On VoIP Based Packet Loss Audio Prediction For Engineering

Voice-Over-IP (VoIP) uses packet transmission of speech over the Internet (IP network). However, at the receiving end, packets are missing due to network delay, network congestion (Jitter) and network errors. This packet loss degrades the quality of speech at the receiving end of a voice transmission system in an IP network . Since the voice transmission is a real-time process, the receiver cannot request for retransmission of the missing packets. Concealment algorithms , either transmitter or receiver based, are used to replace these lost packets . The packet loss concealment (PLC) techniques described in the standards ANSI T1.521 (Annex B) and ITU-T Rec. G. 711 (Appendix I),have good performance, but these algorithms so not use subsequent packets for reconstruction. Furthermore, there are discontinuities between the reconstructed and the subsequent packets, especially at the transitions from voiced to unvoiced and phoneme-to-phoneme.The goal of this work is to develop an improved PLC algorithm, using the subsequent packet information when available. For this, we use the Time-Scale Modification (TSM) technique based on Waveform Similarity Over-Lap Add (WSOLA) to reconstruct the dropped or lost packets. The algorithm looks ahead for subsequent packets., If these packets are not available for reconstruction, algorithm uses information from past packetSo Subjective tests show that the proposed method improves the reconstructed speech quality significantly,,By implementing the algorithm on Hardware Development Kit of Voice-Over-IP over WIFI , under the manually simulate the random packet loss ratio from 1% to 35%, this algorithm shows excellent and robust performance.