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Error recovery for Packet Audio and Video

Error recovery for Packet Audio and Video. Henning Schulzrinne Columbia University New York, NY. Options for reliability. retransmission redundancy interleaving forward error correction. Redundancy. packet redundant coding offset in time but: lose coding state. RTP packet header.

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Error recovery for Packet Audio and Video

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  1. Error recovery for Packet Audio and Video Henning Schulzrinne Columbia University New York, NY

  2. Options for reliability • retransmission • redundancy • interleaving • forward error correction

  3. Redundancy • packet • redundant coding offset in time • but: lose coding state RTP packet header hi-bw content (e.g. MPEG audio) lo-bw content

  4. Retransmission • receiver requests missing packets by sequence number • scalable multicast under development • used by RTP H.261 codec • usually, delay too high • useful for passive listeners, recording devices

  5. Forward Error Correction • exclusive OR (XOR) or Reed-Solomon • N > 1 redundant packets within block • XOR: parity of other packets in block • can recover if <= N lost • XOR: low complexity • media independent • great for multicast

  6. Interleaving • typically, several frames per packet (header overhead!) • split samples or frames across packets •  packet loss affects smaller amount of voice data •  increases delay, header overhead

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