Re: [MMUSIC] Proposal for what bundle should say about demux

Colin Perkins <> Mon, 27 May 2013 12:41 UTC

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Date: Mon, 27 May 2013 13:41:35 +0100
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To: Cullen Jennings <>
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Subject: Re: [MMUSIC] Proposal for what bundle should say about demux
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I'm not sure I agree.

As I said in my previous message to the list, if we are agreed that the m= lines in a BUNDLE group form a single RTP session, then I believe we need unique payload types across all m= lines. In this case, BUNDLE can simply say that regular RTP source demultiplexing based on the SSRC has to be performed, then the payload type can be used to match sources to m= lines for those applications that care about doing so. 

If we're not agreed that the m= lines in a BUNDLE group form a single RTP session, then we have a lot more to discuss...


On 23 May 2013, at 19:02, Cullen Jennings (fluffy) wrote:
> Here's is my proposal for roughly what the bundle draft should say about this demux topic 
> Application will decide which packet processing pipeline to pass an given RTP/RTCP packet to based on what the application knows:
> 1) If future RFCs define new things (like RTP header extension), that explicitly specify the mapping, check if that future RFC is in use and if so then use that to form the mapping 
> 2) If the PT type is uniquely identifies a mapping, use that to form the mapping
> 3) If application knows the SSRC the other side will use, use that to form the mapping 
> 4) if there is no way to know which pipeline to pass it too, the packet MAY be discarded or the application MAY decide to buffer it until the mapping is known 
> This is trivial to implement. It meets the requirements for Plan A, Plan B, UCIF, CLUE, and so on. 
> We could swap the order of step 2 and 3, My thinking for this order was the only time it made any difference the order was if the PT were unique and indicated a different mapping than the SSRC. The only way this could happen is with a SSRC collision so the PT is the one that would be correct not the SSRC. If someone feels strongly the order of steps 2 and 3 should be the opposite way around, I can live with that.
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Colin Perkins