Re: [rtcweb] Consensus vs. Voting (was Re: Call for Consensus Regarding Selecting Recommended Audio Codecs)

["Rauschenbach, Uwe (NSN - DE/Munich)" <[e-mail]>]

From: [e-mail] on behalf of ext Roman Shpount
 

> On Mon, Jan 14, 2013 at 2:50 PM, Adam Roach <[e-mail]> wrote:
>
>
>	I am not making an argument supporting G.722 per se, and I think
its merits and/or drawbacks are red herrings in this conversation. The
argument is against *normatively* specifying support of *any* additional
codecs. I don't think it was a good idea to have 2 MTIs to start with. A
single MTI gets us interop. Anything beyond that rises to the level of
"MAY," and no higher.
>	
>	I would be making the exact same set of arguments if G.722 were
MTI, and the ongoing discussion were on whether Opus "SHOULD be
supported."
>
>
> We already have two MTI OPUS and G.711. From my point of view OPUS
gets us all the future end points; G.711 gets us PSTN; and G.722 would
get us legacy HD Audio.
>
> AMR-WB (as well as AMR and GSM) from my point of view deserve some
mention in the specification but do not warrant a SHOULD. AMR-WB would
be nice to have to connect to mobile networks but there are serious IPR
related issues preventing its support. Furthermore, even though AMR-WB
is supported by a significant number mobile phones, AMR-WB network
interconnects are virtually non-existent, so, from practical point of
view, support for this codecs is a lot less critical.


I do see AMR / AMR-WB at the same level as G.722 - to support
interoperability with legacy networks without the need for transcoding.
I believe saving transcoding cycles is important for the success of
RTCWeb, as it allows building bridges to the legacy world of real-time
communications (i.e. fixed and mobile communication networks) at a
reasonable cost. Hence, I consider it not just "nice to have".

It may be true that the G.711 is most widespread today at NNI interfaces
due to the PSTN legacy and support in the fixed network world, but SIP
NNI interfaces are only now being rolled out, and as codec negotiation
is an integral part of SIP, I do expect that they will support multiple
codecs (at least in the medium term). 

More or less all of today's mobile phones support AMR-WB. If we can
connect to them and support AMR-WB, transcoding won't be needed for
getting HD audio from mobiles. G.722 is not available in mobile phones.
If the WebRTC gateway connects directly to the mobile core network (be
it VoIP-based or circuit switched), then the network interconnects
mentioned above are not even needed, and AMR/AMR-WB audio can be passed
through directly. 

To support the deployment scenarios related to mobile networks, I
propose to include a recommendation for AMR/AMR-WB, i.e. I prefer option
1. 
Details of how to exactly do the recommendation can be worked out in the
process.   


Kind regards,
Uwe Rauschenbach