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Flexible FEC: Encoding in RTP
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Varun Singh
November 10, 2014
Technology
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Flexible FEC: Encoding in RTP
Payload WG, IETF91, Honolulu
Varun Singh
November 10, 2014
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Transcript
flexible-FEC Ali C Begen Varun Singh Mo Zanaty AVTCore, IETF
91 draft-singh-payload-rtp-1d2d-parity-scheme-00
Motivation • Scalability issues with – RFC 5109 – SMPTE 2022-1 – RFC
2733
Row FEC (1D) 1 2 3 7 8 9 4
5 6 R1 R2 R3 ! 1 2 3 7 8 9 4 5 6 R1 R2 R3 ! !
Column FEC (1D) 1 2 3 7 8 9 4
5 6 C1 C2 C3 1 2 3 7 8 9 4 5 6 C1 C2 C3 ! ! ! ! ! ! !
2-D FEC 1 2 3 7 8 9 4 5
6 C1 C2 C3 R1 R2 R3 ! ! ! ! 1 2 3 7 8 9 4 5 6 C1 C2 C3 R1 R2 R3 ! ! ! ! !
RFC 6363: FEC Framework RTP Packets FEC Code FEC Module
RTP (De)mux Transport Layer (UDP) IP Repair RTP Source RTP
Format of repair packets IP Transport RTP header FEC header
Repair Symbol RTP payload
FEC payload 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 +-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+ |MSK|P|X| CC |M| PT recovery | SN base | +-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+ | TS recovery | +-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+ | length recovery |M or Mask[8-‐15]| N or Mask[0-‐7]| +-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+ | Mask [16-‐47] (optional) | +-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+ | | + Mask [48-‐111] (optional) + | | +-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+-‐+
MSK values (1/2) • 00 à 16-bit mask • 01
à 48-bit mask • 10 à 112-bit mask • 11 à variable length mask, see M and N values
MSK values (2/2) • M=0, N=0 à fixed values indicated
in SDP • M>0, N=0 à non-interleaved of M packets starting from SN_base – FEC = SN, SN+1, SN+2,…, SN+(M-‐1), SN+M. • M>0, N>0 à interleaved with M offset starting from SN_base in a group of N packets – FEC = SN+(Mx0), SN+(Mx1),…, SN+(MxN).
Next steps • Discussion in MMUSIC about SDP • Adoption
as PAYLOAD WG-item