Re: [AVTCORE] Multi-party real-time text requiring new RTP payload type

worley@ariadne.com Fri, 08 May 2020 01:19 UTC

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From: worley@ariadne.com (Dale R. Worley)
To: Gunnar =?utf-8?Q?Hellstr=C3=B6m?= <gunnar.hellstrom@omnitor.se>
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In-Reply-To: <b14513ac-c8f2-7e54-75d9-d2c7f67c3f97@omnitor.se> (gunnar.hellstrom@omnitor.se)
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Date: Thu, 07 May 2020 21:19:33 -0400
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Subject: Re: [AVTCORE] Multi-party real-time text requiring new RTP payload type
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Gunnar Hellstrom <gunnar.hellstrom@omnitor.se> writes:
> Therefore I 
> also doubt that current RTP implementations are easy to request to watch 
> out for new SSRCs. I took a look into one RTP implementation, and yes, I 
> found some traces of a possibility to look for new SSRCs, but also other 
> places where the method documented in RTP to detect a shift of SSRC for 
> an existing stream by seeing 50 packets received with the new SSRC.

Yes, it sounds like that's the crux.  While it's easy enough to say that
the protocol has the fields to allow that the packets all have the same
encoding and need to be sorted into separate streams based on the SSRCs,
the usage has always been that SSRCs change infrequently, e.g. video
cuts.  And that means that the implementations likely all embed that
assumption.

Dale