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Re: [rtcweb] Working Group Last Call for draft-ietf-rtcweb-rtp-usage-13

Alex Eleftheriadis <alex@vidyo.com> Mon, 12 May 2014 06:48 UTC

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From: Alex Eleftheriadis <alex@vidyo.com>
To: Bernard Aboba <bernard.aboba@gmail.com>
Thread-Topic: [rtcweb] Working Group Last Call for draft-ietf-rtcweb-rtp-usage-13
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Date: Mon, 12 May 2014 06:48:45 +0000
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Subject: Re: [rtcweb] Working Group Last Call for draft-ietf-rtcweb-rtp-usage-13
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On May 10, 2014, at 2:47 AM, Bernard Aboba <bernard.aboba@gmail.com> wrote:

> Cullen said:
> 
> "This has RTX (RFC4588) and MUST. RTX has turned out to be close to useless in interactive communications systems because the RTT is just too high to make this viable. "
> 
> [BA] Where temporal scaling is used, RTX can be useful in protecting the base layer.  So it's not universally useless.  I do agree that MUST is too strict, though.
> 

Let's make sure that this point is clearly understood, because it keeps re-appearing in discussions. 

When temporal scalability is used, the lowest temporal level frames are far enough apart that retransmission can be used. This is already deployed in products, and is supported by all RTP payload formats for video codecs that support temporal scalability (H.264 SVC, VP8, HEVC). 

Regards,

--Alex

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