Re: [AVTCORE] Improved RTP-mixer performance for RFC 2198 and RFC 4103 redundancy coding

James Hamlin <> Mon, 09 March 2020 17:11 UTC

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From: James Hamlin <>
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Thread-Topic: [AVTCORE] Improved RTP-mixer performance for RFC 2198 and RFC 4103 redundancy coding
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Date: Mon, 09 Mar 2020 17:11:05 +0000
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Subject: Re: [AVTCORE] Improved RTP-mixer performance for RFC 2198 and RFC 4103 redundancy coding
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Hi Gunnar

This is a very interesting draft. It seems to me to fix the stated problem.

We'll have some comments on the use of the CSRC-list, and packet format, but I'll start with a more general thread:-

There have been interoperability issues within VRS to do with redundancy, which have taken time to iron out. It will be important to maintain interoperability with current implementations - which you've specified with the rtt-mix attribute.

I think, the latency incurred with current implementations can probably be kept within acceptable limits. For example when 2 participants are typing concurrently a transmission interval of 100ms and 2 redundant generations would incur no more latency that one participant at 300ms intervals. There is some reduction in fault tolerance because the redundant generations are closer in time and therefore their loss probabilities are likely to be more correlated. Some further timing tweaks could improve further. Most of the time people don't type over each other so the need for higher transmission rates would not be sustained and networks can generally handle much higher rates if required.

Best regards



[X]James Hamlin
Purple, a Division of ZP Better Together, LLC

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