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

Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com> Tue, 15 January 2013 14:48 UTC

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Date: Tue, 15 Jan 2013 15:48:12 +0100
From: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
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Subject: Re: [rtcweb] Call for Consensus Regarding Selecting Recommended Audio Codecs
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On 2012-12-20 09:29, Magnus Westerlund wrote:
> WG,
>
> As an outcome of the Vancouver IETF meeting codec discussions we did
> promise to run a call for consensus regarding if the WG was interested
> in specifying a small set of recommended audio codecs. We are sorry this
> has been delayed until now.
>
> The question for the call of consensus is between two options.
>
> 1) Run a process in the WG to select and specify a small set of
> audio/speech codecs that would be RECOMMNEDED to implement by a WebRTC
> end-points
>
> 2) Do nothing and let the already specified Mandatory to Implement Audio
> codecs be the only audio codecs mentioned in the WebRTC specification.
>
> Please indicate your position by January 16th 2013.

I see the following important reasons for creating a RECOMMENDED category:

1. interoperability without quality degradations due to transcoding with 
large installed legacy and existing services.
   Typical examples are interconnection cases to major mobile or fixed 
communication systems. Clearly interop with 3GPP voice services and HD 
Voice in 3GPP and fixed networks is very important. The option with 
transcoding should be avoided as - besides the equipment costs - it is 
affecting the communication quality in terms of more coding distortions 
and delay.

2. take advantage of deep codec specific integrations/optimizations.
   Typical examples are interconnection cases to major mobile systems 
which bearers are highly optimized for a given codec specified for these 
systems. For these systems operating with their 'native' codecs is 
beneficial not only in terms of system capacity and efficiency but also 
from end-user perspective as it will allow least battery consumption in 
the mobile devices (due to that hardware implementations for the codecs 
are often used) and provide best robustness/coverage. At least interop 
to such native codecs in 3GPP mobile networks is essential. This point 
partly overlaps with the previous but also covers cases where new codecs 
will get a deep system integration. The alternative with transcoding in 
a GW should be avoided for the reasons given above (avoiding extra 
distortions and delay).

3. future-proofness of specifications allowing to recommend new codecs 
that turn out to be better/more efficient than existing mandatory codecs.
   As history has proven, even the best mandatory codec has a 
best-before date. We should foresee the possibility to at least 
recommend such a better codec at some stage when felt appropriate.

At the same time, when creating a RECOMMENDED category, I think that it 
should be strictly limited to very few codecs only. At present I see a 
reasonable limit of 3 recommended codecs related to particular interop 
scenarios. However, this number could be increased if new and better 
codecs are deemed would in the future enter this category.

So, my vote goes for option 1.

Stefan

>
> Regards
>
> Magnus Westerlund
>
> ----------------------------------------------------------------------
> Multimedia Technologies, Ericsson Research EAB/TVM
> ----------------------------------------------------------------------
> Ericsson AB                | Phone  +46 10 7148287
> Färögatan 6                | Mobile +46 73 0949079
> SE-164 80 Stockholm, Sweden| mailto: magnus.westerlund@ericsson.com
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