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Extend FEC BB to RTP streaming?

Extend FEC BB to RTP streaming?. Michael Luby Digital Fountain. Motivation. A lot of careful thought and experience has gone into the FEC BB It is a modular, reusable building block that has successfully been the basis of File delivery apps (FLUTE, commercial)

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Extend FEC BB to RTP streaming?

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  1. Extend FEC BB to RTP streaming? Michael Luby Digital Fountain

  2. Motivation • A lot of careful thought and experience has gone into the FEC BB • It is a modular, reusable building block that has successfully been the basis of • File delivery apps (FLUTE, commercial) • Streaming apps (proprietary, commercial) • Based on this experience, there is a proposal to improve the FEC BB in its move from Experimental to Proposed Standard status • This is a good time to officially allow FEC BB to apply to streaming

  3. Motivation • 3GPP SA4 MBMS service has adopted an FEC protection architecture for RTP streaming data that fits into the FEC BB • Generic approach to using FEC for streaming has been identified and verified to be applicable to the 5/6 FEC schemes under consideration for MBMS • S4-AHP159, S4-AHP138, S4-AHP166, S4-AHP181 • Most likely will end up being part of MBMS in Release 6 • 3GPP intention is to bring this work back to IETF (at least in form of Informational RFC)

  4. FEC streaming source block formation example Symbol size = 7 bytes First RTP packet = 8 bytes Second RTP packet = 24 bytes Source block = length of RTP packet, RTP packet (padded out to full symbol) Source symbol 0 0 8 B0,0 B0,1 B0,2 B0,3 B0,4 Source symbol 1 B0,5 B0,6 B0.7 0 0 0 0 0 24 B1,0 B1,1 B1,2 B1,3 B1,4 Source symbol 2 B1,5 B1,6 B1,7 B1,8 B1,9 B1,10 B1,11 Source symbol 3 B1,12 B1,13 B1,14 B1,15 B1,16 B1,17 B1,18 Source symbol 4 B1,19 B1,20 B1,21 B1,22 B1,23 0 0 Source symbol 5 Source block

  5. Source Packet FEC Payload ID SBN ESI • SBN (Source Block Number) • Numbered consecutively • Identifies the source block that the source RTP packets is part of • ESI (Encoding Symbol ID) • Index of first source symbol in source block where this RTP packet starts • Interpretation is FEC scheme independent (except for possibly the length of the field)

  6. Repair packet FEC Payload ID • FEC Scheme dependent • SBN • Identifies the source block from which the repair symbols are generated • Used by all FEC Schemes • ESI • Identifies how the repair symbols are generated • This is FEC scheme dependent • Used by all FEC Schemes • SBL • Number of source symbols in the source block • For some FEC Schemes, this may be part of OTI • EBL • Maximum number of encoding symbols generated for the source block • Used by some FEC Schemes • For some FEC Schemes, this may be part of the OTI • T • Symbol length • For many FEC schemes, this may be part of the OTI

  7. Objective • Proper split of work between AVT and RMT • Streaming issues to be addressed in AVT • How signaling of OTI is done • How source blocks are formed • How source packets and repair packets are multiplexed and demultiplexed • FEC issues to be addressed in RMT • FEC Schemes defined • FEC Payload ID(s) to be used • FEC OTI parameters defined

  8. Possibilities for FEC BB • Explicitly allow applicability to streaming • Currently limited to object delivery by RMT charter • Some FEC Encoding IDs may not be applicable to streaming (leave as is) • Some FEC Encoding IDs may be applicable to streaming without modification (allow mention of this) • Some FEC Encoding IDS may be applicable to both with minor modifications (e.g., use a subset of OTI parameters for streaming) • Use different FEC Encoding IDs for objects and streaming? • Use one FEC Encoding ID and explicit indication in OTI of whether streaming or object delivery? • Use one FEC Encoding ID and implicit indication based on what is included in OTI? • Define FEC Encoding ID for only repair packets and let AVT define generic format for source FEC packets?

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