1 / 9

RTP Payload Format for Multiple Flows FEC

RTP Payload Format for Multiple Flows FEC. IETF 77 – March 2010. draft-peck-fecframe-rtp-mf-01. Orly Peck, RADVISION orlyp@radvision.com. Background. protecting RTP packets from multiple source flows This draft FEC scheme generic Specifies RTP payload format for such FEC packets

mala
Download Presentation

RTP Payload Format for Multiple Flows 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 Multiple Flows FEC IETF 77 – March 2010 draft-peck-fecframe-rtp-mf-01 Orly Peck, RADVISION orlyp@radvision.com

  2. Background • protecting RTP packets from multiple source flows • This draft • FEC scheme generic • Specifies RTP payload format for such FEC packets • Aims to solve source-synchronization problems • Multiple Flows includes Multi-Session and Multi-Source Transmission

  3. Main changes from draft 00 • Remove use of Marker-bit in RTP header • Added L-bit in fec-mf header instead • FEC-Scheme param in SDP moved to a=fmtp line • Implementation considerations added • Offer-Answer considerations added • Security considerations added

  4. FEC-MF 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Num Flows | FID | FID | FID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FID | FID | padding | padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC identifiers (Optional) | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ • L-Bit – indicating whether a list of SSRC identifiers is appended to the FEC-MF header. • Num Flows – number of flows protected by this FEC block • FID – flow ID. Determined by SDP. Correlated to a FEC header appended to the MF-Header. Number of FIDs = Num Flows. • SSRC Identifiers – list of SSRC identifiers from the source RTP headers. Number of SSRC identifiers is 0 if L-bit is set to 0. Otherwise, equals Num Flows * 4 bytes for each SSRC identifier (taken from RTP header of protected source flow).

  5. IANA Registration • Register subtype name fec-mf for application type • Required parameters • fmtp line starts with the FEC-scheme parameter indicating which fec scheme is used for FEC encoding. Following is a list of the required fec scheme specific parameters.

  6. Example – SDP v=0 o=orly 1122334455 1122334466 IN IP4 fec.example.com s= MF FEC Example t=0 0 a=group:FEC S1 S2 R1 m=video 30000 RTP/AVP 100 c=IN IP4 224.1.1.1/127 a=rtpmap:100 MP2T/90000 a=fec-source-flow: id=0 a=mid:S1 m=video 30002 RTP/AVP 100 c=IN IP4 224.1.1.1/127 a=rtpmap:100 MP2T/90000 a=fec-source-flow: id=1 a=mid:S2 m=application 30000 RTP/AVP 110 c=IN IP4 224.1.2.1/127 a=rtpmap:110 fec-mf/90000 a=fmtp:110 FEC-scheme:reed-solomon-fec; max_N:5; repair-window:200000; symbol-size:8 a=mid:R1

  7. Implementation Considerations • For applications with low-latency requirement, protecting multiple flows can reduce FEC bandwidth overhead (while decreasing FEC protection strength).Example – protecting 2D + depth frames in 3D interactive video (requires FEC block to include not more than a single video frame). • Can be used to increase FEC strength (for example protecting 8 packets with 2 FEC packets instead of protecting each 4 packets with a single FEC packet. • Example for application not suitable for using multi-flow FEC protection – two flows where one of them suffers from high packet loss rate, and the other does not.

  8. Offer-Answer Considerations • Sender can offer several FEC-schemes for a multi-flow fec protection. • Offer same FEC-scheme with different parameters. • Receivers not supporting fec-mf must ignore fec-mf lines.

  9. Questions & Comments

More Related