Re: [rtcweb] Signalling, SDP, and the way we think about interconnecting RTCWEB applications

Stephan Wenger <stewe@stewe.org> Sat, 15 October 2011 18:42 UTC

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Date: Sat, 15 Oct 2011 11:42:39 -0400
From: Stephan Wenger <stewe@stewe.org>
To: Harald Alvestrand <harald@alvestrand.no>, <rtcweb@ietf.org>
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Thread-Topic: [rtcweb] Signalling, SDP, and the way we think about interconnecting RTCWEB applications
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Subject: Re: [rtcweb] Signalling, SDP, and the way we think about interconnecting RTCWEB applications
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Hi Harald,

On 10.15.2011 07:29 , "Harald Alvestrand" <harald@alvestrand.no>; wrote:

>
>Given the last point - the app *cannot* "implicitly" what codec will be
>used. And given that it doesn't know the codec, it can't know the
>parameters either.
>
>(that said... I'm all in favour of fewer parameters. The RTP format for
>VP8 that we're in the process of finishing has zero parameters. I hope
>it will remain that way.)

I would be surprised if that were the case.  As the very minimum, I would
suspect that you need some form of upper bound for computational decoder
complexity (measured in pixel numbers per second, framerate/picture size
combination, or whatever).  It doest make sense that two systems agree on
VP8, and the receiver cannot rdecode the sender's bitstream because the
receiver is a cheap cellphone and the sender is a desktop PC which likes
to send 1080p.  Let me also note that the VP8 payload spec (at least the
current public version) has a number of "optional" mechanisms, which you
would want to negotiate, no?

Stephan