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Re: [rtcweb] Call for Consensus Regarding Selecting Recommended Audio Codecs

Koen Vos <koen.vos@skype.net> Thu, 27 December 2012 18:34 UTC

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From: Koen Vos <koen.vos@skype.net>
To: Steve Sokol <ssokol@digium.com>, "Cullen Jennings (fluffy)" <fluffy@cisco.com>
Thread-Topic: [rtcweb] Call for Consensus Regarding Selecting Recommended Audio Codecs
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Date: Thu, 27 Dec 2012 18:33:44 +0000
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Call for Consensus Regarding Selecting Recommended Audio Codecs
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Steve Sokol wrote:
> G.722 has no known IPR issues.

This is inaccurate.

While the basic codec has no such issues, the various Packet Loss Concealment methods that were later added to the standard are patented.  This matters because G.722 uses ADPCM and is unusually sensitive to packet loss.  For instance, without PLC the codec will sometimes generate a full-scale oscillating output after a loss.  Since a traditional PLC doesn't work for this kind of behavior, there was a need to invent a PLC specifically for G.722.

In short: there are IPR issues with the PLC required for using G.722 on the Internet.

koen.


________________________________
From: rtcweb-bounces@ietf.org on behalf of Steve Sokol
Sent: Thursday, December 27, 2012 9:05 AM
To: Cullen Jennings (fluffy)
Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] Call for Consensus Regarding Selecting Recommended Audio Codecs

Per Cullen's request, here is the very short list of audio codecs that seem to have received some interest and the associated benefit of including them in the standard:

G.722 - The de facto standard for "HD audio", G.722 has the advantage of wide deployment in both hard and soft endpoints. G.722 has no known IPR issues. It consumes a relatively modest 64 Kbps which covers most use cases (though not Edge). Inclusion of G.722 would arguably simplify interoperability with HD-capable legacy endpoints and gateways.

AMR, AMR-WB - The official standards for mobile telephony. Adding support for the AMR codecs would arguably simplify the process of interoperation with mobile endpoints. Licenses would be required as both include patented technology.

None - Several group members have argued that the standard should not include SHOULD or RECOMMENDED codecs for various reasons.

Speaking for myself, I don't see much reason to include any of these. With mandatory encryption, media stream bundling and various other divergences from the way most legacy endpoints operate, I don't see unmediated legacy interoperability as likely to happen -- you will always need something to act as a gateway.  That being the case, why clutter up the standard with "SHOULD" or "RECOMMENDED" directives?

The best thing about WebRTC is that it is (thus far) not an attempt to re-build the PSTN on yet another IP platform. Keep is simple.

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