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SRCNAME – A RTCP Source Description Item

SRCNAME – A RTCP Source Description Item. draft-westerlund-avtext-rtcp-sdes-srcname-03 Bo Burman, Magnus Westerlund. OVERVIEW. IPR Declarations SRCNAME Proposal SRCNAME Open Issues Relation to APPID Next Steps. IPR Declarations.

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SRCNAME – A RTCP Source Description Item

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  1. SRCNAME – A RTCP Source Description Item draft-westerlund-avtext-rtcp-sdes-srcname-03 Bo Burman, Magnus Westerlund

  2. OVERVIEW • IPR Declarations • SRCNAME Proposal • SRCNAME Open Issues • Relation to APPID • Next Steps

  3. IPR Declarations • There exist IPR Declarations on draft-westerlund-avtext-rtcp-sdes-srcname-03: • Ericsson • https://datatracker.ietf.org/ipr/1638/ • Microsoft • https://datatracker.ietf.org/ipr/1932/

  4. SRCNAME • This version has been scoped down • Targets the needs of Simulcast: • draft-westerlund-avtcore-rtp-simulcast-03 • Provide a SSRC with the Identify of its: • Media Source • Encoding Configuration • Enables a RTP Receiver to immediately determine: • Is this an alternate encoding of a Media Source • What Properties does this encoding have

  5. SRCNAME • Media Source is the combination short source identifier • Scoped by CNAME • CNAME ensures inter endpoint uniqueness • Thus short token • The Encoding Configuration Identifier • short token • Bind it to encoding configuration in signaling • srcname= <media-source>.<encoding-id> • Example: “a.G”

  6. SRCNAME • SRCNAME Distribution • RTCP: Default method • RTP Header Extension: Optional • draft-westerlund-avtext-sdes-hdr-ext-01 • SDP Signaling as Source attribute: Optional • a=ssrc: 123456789 srcname:a.G • Available with SSRCs in RTP/RTCP • Intended to be persistent on per SSRC level • A given SSRC should not change its SRCNAME • Conceptual Source like mixes • Is there own sources • Contributing Sources can be ID through CSRC => SRCNAME

  7. SRCNAME Open Issue • Usage of SRCNAME on Redundancy Packets Streams • Examples: • RTP Retransmission (RFC 4588) • XOR FEC (RFC 5109) • These are one to one mappings with Source Packet Streams • Use the same SRCNAME and you know there is a relation? • But not what! • Given by RTP Payload Type in the above cases

  8. Relation to APPID • Assuming APPID is a indirection to SSRC • Could be a replacement for SRCNAME • Then each Simulcast Source Packet Stream needs its own APPID • Bind that to Media Source and Encoding Configuration • However APPID requires: • A Receiver must create sufficient number of APPIDs for the Media Sources the sender have • That signaling can distribute the APPIDs • Broadcast or Multicast can fail these • SRCNAME hasexplicit semantics: • Works in all cases independent of configuration

  9. Next Steps • A solution for stream correlation • Required if Simulcast goes forward • APPID discussion needs to continue • Willing to give it some time to mature • APPID can solve a complementary problem • Provide Purpose for Simulcast Encoded Streams • Explicit Semantics has advantages • Please review and provide feedback • Later consideration for adoption

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