- Packet loss concealment
Packet loss concealment (PLC) is a technique to mask the effects of
packet loss inVoIP communications. Because the voice signal is sent as packets on a VoIP network, they may travel different routes to get to destination. At the receiver a packet might arrive very late, corrupted or simply might not arrive. One of the situations in which the last situation could happen is where a packet is rejected by a server which has a full buffer and cannot accept any more data. In a VoIP connection, error-control techniques such as ARQ are not feasible and the receiver should be able to cope with packet loss.PLC techniques
* Zero insertion: the lost speech frames are replaced with zero
* Waveform substitution: the missing gap is reconstructed by repeating a portion of already received speech. The simplest form of this would be to repeat the last received frame. Other techniques account forfundamental frequency , gap duration etc. Waveform substitution methods are popular because of their simplicity to understand and implement. An example of such algorithm is proposed inITU recommendationG.711 Appendix I.
* Model-based methods: an increasing number ofalgorithm s that take advantage of speech models of interpolating and extrapolating speech gaps are being introduced and developed.External links
* [http://www.raduniversity.com/2004/packet_loss_concealment/main.htm Packet Loss Concealment Techniques and Algorithms]
* [http://www.voiptroubleshooter.com/problems/plc.html VoIP Troubleshooter: Packet Loss Concealment]
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