1 / 8

RTP Payload Format for Reed-Solomon FEC

RTP Payload Format for Reed-Solomon FEC. IETF 77 – March 2010. draft-galanos-fecframe-rtp-reedsolomon-01. Vincent Roca, INRIA vincent.roca@inria.fr. Orly Peck, RADVISION orlyp@radvision.com. Sarit Galanos, RADVISION sarit@radvision.com. Main Changes from draft 00.

niyati
Download Presentation

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 77 – March 2010 draft-galanos-fecframe-rtp-reedsolomon-01 Vincent Roca, INRIA vincent.roca@inria.fr Orly Peck, RADVISION orlyp@radvision.com Sarit Galanos, RADVISION sarit@radvision.com

  2. Main Changes from draft 00 • Using terminology as defined in RFC 5510 • Removing constraint for protection of consecutive RTP packets • Added implementation considerations section • Added clarifying sentences and examples. • Added a comprehensive security section

  3. 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_r | i | SN_base | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | reserved | BML | pkt_span| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . bit-mask (optional, variable length) . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ • n_r : the number of FEC repair packets used to protect this source block. • i – the 0-based index in the sequence of n_r FEC repair packets • SN_base– the lowest RTP sequence number (taking wraparound into account) of the source packets protected by this repair packet. This SN_base also identifies the source block. • pkt_span–The number of consecutive source packets protected by this repair packet • Reserved - for future use • BML - Bit Mask Length: indicates the length of the bit-mask in units of 32-bit words. For case of non-consecutive RTP packets protected. • Bit-mask – set at the length indicated by BML. Indicates which RTP packets are protected.

  4. About the bit-mask… • used in situations where RTP packet erasures happen prior to reaching FECFRAME encoder or when non-consecutive packets are protected. • need a way to signal gaps in RTP SN numbering, i.e. packets that are not in the source block • use a variable length bit-mask array • no mask if BML=0

  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 • element-size: a non-negative integer indicating the length of each encoding symbol in bits. Equals to the m parameter in the GF (2^m).

  6. Repair-Window • The sender knows the time that spans between the first RTP packet sent, and the repair packets. Defining the RW size impacts the maximum number of source packets in a FEC block. • Defines the minimum time the receiver should wait. • May be negotiated between sender and receiver.

  7. Implementation considerations • Set FEC code-rate dynamically according to network packet loss. Improves bandwidth utilization. • Reduce protected media bandwidth, in order not to increase total bandwidth consumption and worsen network conditions. • Appropriate design – choosing k, n • Packetization – protecting RTP packets with similar sizes if possible.

  8. Questions & Comments

More Related