Re: [rtcweb] Is there room for a compromise? what about no MTI?

Ron <ron@debian.org> Sat, 21 December 2013 23:16 UTC

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Date: Sun, 22 Dec 2013 09:46:51 +1030
From: Ron <ron@debian.org>
To: rtcweb@ietf.org
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Subject: Re: [rtcweb] Is there room for a compromise? what about no MTI?
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On Sat, Dec 21, 2013 at 04:55:13PM -0500, Bernard Aboba wrote:
> "David Singer" said:
> > There are some things to be said for no MTI:
> > 
> > * (we have had this in 3GPP): once something is mandatory, it’s hard to
> > un-mandate it.  “what about backward compatibility with older systems?”.
> > 3GPP is taking many years to move H.263 from mandated to recommended to
> > optional.  the world moves on, and mandates stay.
> 
> [BA] In particular, I am expecting implementations of H.265 and VP9 to show
> up during 2014, and in 18-24 months it is quite possible the H.264/VP8 debate
> will be irrelevant. "No MTI" allows us to focus on getting the specs
> finalized without the continuing distraction of MTI video codec debates. 

While I have no doubt that people will begin supporting VP9 and/or H.265
before too long, the significant extra processing cost required to run
them anywhere near real-time will likely pose its own interoperability
barrier well beyond the challenges of choosing an MTI codec for anything
that might elect to only support those.

You're still going to need a lower complexity fallback for some time to
come if you actually care about broad interop.  Unless Daala manages a
clean sweep like Opus did.


> > * it is functionally equivalent to an MTI that is not respected (and more honest)
> 
> [BA] No MTI is better than a disrespected MTI choice that continues to distract the WG.

Spoiling the marketing of people who don't care about interop is better
than spoiling the standard.


> > * there are audio-only devices (anyone remember those things called ‘telephones’?)
> 
> [BA] How did SIP somehow survive without an IETF mandatory to implement audio
> codec?

It ...  didn't?  SIP has so many ways to be completely non-interoperable
that as a global standard it's been completely stillborn.  Codecs are
the least of the many interoperability problems that ruined it by design.

It's effectively been contained to being a reinvention of proprietary
digital handset protocols bound to a particular brand of PBX, with few
guarantees beyond boundless user frustration once you mix equipment
from more than one vendor.

As a communication mechanism for connecting arbitrary remote peers it's
a complete failure.  If it wasn't, it's probably pretty safe to say this
working group would have never actually needed to form in the first place.
And maybe also safe to say that Microsoft would have never purchased
Skype :)

We should learn from those mistakes, not let people fool us again into
re-creating them.


> And if they had chosen something other than G.711, might that not have
> complicated RTCWEB discussions on the subject?

The PSTN?  You could trivially fit full band Opus into a single G.711
timeslot today.

But they don't for general use because, you know, interoperability.

And the PSTN *also* needs gateways to transcode G.711 to 'itself' in
some cases, because when people let the market decide, they came up
with two mutually incompatible companding algorithms.  So a standards
body had to step in and mandate which one wins when they collide, so
that we could have an actually global telephone network.  QED.

  Ron