Re: [rtcweb] Confirmation of consensus on audio codecs

Randall Gellens <> Wed, 29 August 2012 16:29 UTC

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Date: Wed, 29 Aug 2012 09:25:53 -0700
From: Randall Gellens <>
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Subject: Re: [rtcweb] Confirmation of consensus on audio codecs
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Re: [rtcweb] Confirmation of consensus on audio codecs
At 7:26 PM +0000 8/28/12, <> wrote:

We do not recommend Opus to be taken as a mandatory codec for RTCWeb at this point. From high quality low bit rate and mobile applications point of view the 3GPP AMR-WB codec (also known as ITU-T G.722.2) is the most preferable for us. For interoperability with implementations restricted to unencumbered codecs, we prefer G.711 and G.722.

Mandating only G.711 provides a floor to prevent total failure to negotiate codecs, while allowing implementations to support whichever codecs make sense in their environments.

At 8:39 PM -0700 8/21/12, Ted Hardie <ted.ietf at> wrote:

the fundamental design of RTCWEB allows for the
negotiation of any codec mutually supported.  The decision to chose a
Mandatory-to-implement was not made to eliminate other choices, but to
eliminate interoperability failures by ensuring that at least one
common codec is always available.

I think this is a key point.  Codecs should be mandated only to prevent negotiation failure, not to guarantee ideal performance, especially in light of Ted's next statement:

At 8:39 PM -0700 8/21/12, Ted Hardie <ted.ietf at> wrote:

the group presumes that codec support does not
come from the downloadable Javascript application, but from the
application environment into which it is downloaded (commonly a
browser or mobile environment using similar technology).  Promoting
support for those environments to have access to codecs supported by
the underlying hardware is the best way to further this goal, at least
in my personal opinion.

This makes a lot of sense. Especially on mobile devices, natively supported codecs are likely to have optimized performance within the operating environment (e.g., mobile device and cellular channel).

Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
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Randall Gellens
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