1 / 8

RTP Payload Format for Reed-Solomon FEC

RTP Payload Format for Reed-Solomon FEC. IETF 76 – November 2009. draft-galanos-fecframe-rtp-reedsolomon-00. Sarit Galanos, RADVISION sarit@radvision.com. Orly Peck, RADVISION orlyp@radvision.com. Background. Splitting draft-galanos-fecframe-rtp-reedsolomon-mf-00 to 2 drafts

bond
Télécharger la présentation

RTP Payload Format for Reed-Solomon FEC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RTP Payload Format for Reed-Solomon FEC IETF 76 – November 2009 draft-galanos-fecframe-rtp-reedsolomon-00 Sarit Galanos, RADVISION sarit@radvision.com Orly Peck, RADVISION orlyp@radvision.com

  2. Background • Splitting draft-galanos-fecframe-rtp-reedsolomon-mf-00 to 2 drafts • Searched for a method of protecting RTP packets against random, bursty losses which enables: • Backward compatibility • Low recovery latency • Dynamic on/off switching • This draft • Describes FEC scheme based on Reed Solomon code and FEC framework • Specifies RTP payload format for such FEC packets

  3. RTP header for repair packets 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |V=2|P|X| CC |M| PT | sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | timestamp | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | synchronization source (SSRC) identifier | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | contributing source (CSRC) identifiers | | .... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ • Marker bit (M) – not used • Payload Type (PT) – dynamically determined in SDP • Sequence Number • initiated randomly [rfc3550] • One higher than number in the previously transmitted repair packet • Timestamp – corresponds to repair packet transmit time • Synchronization source (SSRC) – randomly assigned [rfc3550]

  4. FEC header for repair packets 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | N-K | i | SN Base | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Num Packets | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ General fields • N-K – the number of FEC packets used to protect this block • i – 0 based packet index in the N-K FEC packets sequence • SN base – the lowest sequence number (taking wraparound into account) of the source packets protected by this repair packet • Num Packets –The number of consecutive source packets protected by this repair packet • Reserved - for future use

  5. IANA Registration • Register subtype name reed-solomon-fec for audio/video/text/application • Required parameters • Max_N – upper limit for N, which is the total number of source and repair packets in a block • Repair window (us) – time span of the source and repair packets • symbol-size: a non-negative integer indicating the length of each encoding symbol in bits.

  6. SDP example v=0 o=sarit 1122334455 1122334466 IN IP4 fec.example.com s= Reed Solomon FEC Example t=0 0 a=group:FEC S1 R1 m=video 30000 RTP/AVP 100 c=IN IP4 224.1.1.1/127 a=rtpmap:100 MP2T/90000 a=mid:S1 m=application 30000 RTP/AVP 110 c=IN IP4 224.1.2.1/127 a=rtpmap:110 reed-solomon-fec /90000 a=fmtp:110 max_N:5; repair-window: 200000; symbol-size:8 a=mid:R1

  7. Open issues • Reed-Solomon primitive polynomial – • Defined by protocol (hard definition) • Negotiated in SDP • Combination (unless specified in SDP use default value from standard).

  8. Comments are welcome!

More Related