Re: [rtcweb] H.261 vs No MTI (was: Alternative consensus and MTI video codecs)

Tim Panton <> Fri, 08 November 2013 11:34 UTC

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From: Tim Panton <>
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Date: Fri, 8 Nov 2013 11:31:33 +0000
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To: cowwoc <>
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Subject: Re: [rtcweb] H.261 vs No MTI (was: Alternative consensus and MTI video codecs)
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On 8 Nov 2013, at 05:56, cowwoc <> wrote:

> I'll bring up a related point that I brought up a few days ago (I changed to subject to avoid hijacking the thread).
> Say we can't agree on whether to use VP8 or H.264 as MTI. We can then simply settle on a codec with expired IPR such as H.261. H.261 is the codec everyone loves to hate but allow me to point out the following:
> If H.261 is MTI, you can still upgrade to VP8
> If H.261 is MTI, you can still upgrade to H.264
> If H.261 is MTI, you can still use transcoding to connect VP8 to H.264
> Using H.261 as MTI is a big win over no MTI because "no MTI" means we're forced to do transcoding, whereas H.261 as MTI means         we can still do transcoding if we want, but we don't have to.
> And yes, I agree that a more ideal solution is to choose VP8 or H.264 as MTI (or both) than H.261... but if worse comes to worse, I don't see a benefit to choosing "no MTI" over H.261.
> Does anyone have a counter-point?

Ok, I'll bite. (Despite having proposed H261 at the mic in Paris, I've changed my mind in the meanwhile.)

The H261 option makes _everyone_ equally unhappy. 

The browser makers have to support and test 2 codecs - one of which they don't want anyone to use.

The javascript folks have to do massive amounts of digging in the SDP to try and work out if the remote offer of h264 is
transcoded in a middlebox or is direct vp8 or perhaps that h261 is the best option - or perhaps no video is applicable.

The middlebox guys get to implement 3 different codecs, and test transcode paths between all of them. The video mixer guys
can't do video size switching well because h261 hasn't got that concept.

The user gets a totally variable experience based on factors she cant control. There will be lots of dissatisfied users who's
first video call happened to be h261 and never go back to the service - better to fail back to audio than connect with a poor experience.

Part of the problem is that O/A + SDP isn't a rich enough medium for the application to make a sensible/correct decision.
Given that we are stuck with OA+SDP for version 1.0 at least, lets not make it worse by complicating the SDP and degrading the 
user experience at the same time.

Sorry to be so negative. 
I'll try and come up with a more positive solution next :-)


> Gili
> On 07/11/2013 9:22 PM, Gregory Maxwell wrote:
>> On Thu, Nov 7, 2013 at 5:06 PM, Adam Roach <> wrote:
>>> Our situation is radically different: there are a number of actual arguments
>>> to be made for both options.
>> We've heard these arguments, at long length, and have, apparently, not
>> found them sufficiently decisive or we wouldn't be at this juncture.
>> I must have failed to make the point I was attempting to make
>> sufficiently clear.  Let me retry: If we believe that an MTI video
>> codec, regardless of what it is, was an independently important thing
>> to have then "no MTI" shouldn't be the result of failing to achieve an
>> MTI in discussion, because there exist _an option_, any option, to
>> achieve a MTI video codec.  So I was hoping to see any support for "no
>> MTI" (which sounded very popular in the room) to come with arguments
>> for why an MTI doesn't actually matter.
>> Without intending any "push", strong or otherwise, I'll point out that
>> the apparent difficulty in responding to my message without
>> allegations of irrational arguments and emotional investments
>> increases my estimation that locating a set of "randomly selected
>> neutral parties" which is sufficiently non-partisan to not cloud the
>> process is not obviously possible.  Without that kind of doubt in mind
>> it's not clear to me if that alternative process could be successful,
>> which is why I attempted to illustrate my point with the 4.4 coinflip.
>> Coinflip will produce a result, and the result it will produce will
>> achieve the goal of selecting an MTI codec (especially in
>> consideration of substantial support for either option, both on the list
>> and in the room), and it doesn't require selecting non-partisan
>> parties.  I wasn't trying to say it was _good_ though, only that it
>> was enough to say failure to pick an MTI alone isn't enough to justify
>> removing MTI for the sake of MTI from the goals.
>> (There are plenty of other arguments that can be made about the
>> non-optimality of the 3929 panel process— e.g. the requirement to meet
>> nomcom requirements with physical meeting attendance would generally
>> make it easy for large corporate contributors, especially ones with
>> diverse participation, to be over represented. But, to be frank, your
>> response has made me feel uncomfortable pointing that much out... I
>> didn't start this thread with an intention to argue against it, but I
>> wonder after your message if anyone else would dare.)
>> _______________________________________________
>> rtcweb mailing list
> _______________________________________________
> rtcweb mailing list

Tim Panton - Web/VoIP consultant and implementor