Subject: RE: [Speermint] Voice codecs

From: "Livingood, Jason" <[email-masked]>
Date: Mon, 31 Jul 2006 09:47:11 -0400

Brian wrote:

> I did say something in my message which may have escaped some 
> notice.  I said "origination side".  One of the things you 
> have to get right on any kind of part like transcoding is 
> what assumptions are made.  You can assume the origination 
> side does it, the destination side does it or the peering 
> fabric itself does it.  I think it's essential to choose one, 
> or we won't have interoperability.  More than one is always 
> possible, but at least one is required.  I think origination 
> side is best: it means that across the peering fabric, there 
> is at least one common codec.

So, it is looking convincingly now that WG consensus is against a lowest
common denominator codec.  ;-) 

But Brian raises an interesting question here.  Somewhere in our drafts
(several of them) we *may* need to consider optional inclusion of a
transcoding function and describe how it might be implemented.  When we
take up that discussion, I think Brian poses an interesting question.  

If I consider it from the perspective of some operator that is using all
the major codecs in my endpoints, and someone connects with some obscure
codec then I can see an arguement for having the originator perform any
transcoding.  (And if that is indeed the case, it may even be like lots
of other stuff an originating network may or may not do that we don't
care about and call out of scope.)

Jason

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From: "Geoff Devine" <[email-masked]>
Date: Mon, 31 Jul 2006 14:27:41 -0400

In your codec architecture example, you say that the originator may have
some strange and wonderful codec that is not supported by the peer
network.  I'd point out that the other 50% of the time, that endpoint is
the terminator in the call, not the originator.  I would think that
transcoding would be something that is negotiated as part of the peering
business arrangement.  In terms of $ per port, transcoding is a
relatively costly operation and somebody is going to have to purchase
and operate the transcoding equipment.  

Transcoding, like echo cancellation, is something you want to avoid
doing extra times since it degrades voice quality.  A path that goes,
say, from AMR to G.711 to iLBC is going to have a lower MOS score than a
path that goes AMR to iLBC.  Ideally, you don't want to transcode at all
since that gives you the least impairment and the least delay.

Geoff

-----Original Message-----
From: Livingood, Jason [mailto:[email-masked]] 
Sent: Monday, July 31, 2006 9:47 AM
To: Brian Rosen; [email-masked]
Cc: Greg Herlein; Ed Okerson; Lipford,Mark A [CTO]; Geoff Devine; Klaus
Darilion; Henry Sinnreich
Subject: RE: [Speermint] Voice codecs

Jason

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From: "Brian Rosen" <[email-masked]>
Date: Mon, 31 Jul 2006 14:39:10 -0400

Okay, makes sense.  So, maybe it's more like, the federation agrees on
minimal codec support, and participants must be prepared to transcode to
that minimal set if their endpoints need it.

I don't think you can mandate anything that guarantees only one transcode.
However desirable it may be.

Brian

> From: Geoff Devine [mailto:[email-masked]]
> Sent: Monday, July 31, 2006 2:28 PM
> To: Livingood, Jason; Brian Rosen; [email-masked]
> Cc: Greg Herlein; Ed Okerson; Lipford,Mark A [CTO]; Klaus Darilion; Henry
> Sinnreich

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From: "Geoff Devine" <[email-masked]>
Date: Mon, 31 Jul 2006 14:52:18 -0400

That sounds good to me.  

I'd point out that different federations are likely to have different
ideas about what makes up the "minimal codec".  In broadband-oriented
federations, that would likely be G.711.  In cellular-centric
federations that are converging to IP transport, it's more likely to be
their native client compression codec.  If eBay created one based on
Skype, it could very well be iLBC.

I think we all agree that transcoding is something we want to avoid but
we need to come up with an architecture that takes it into account. 

Geoff

-----Original Message-----
From: Brian Rosen [mailto:[email-masked]] 
Sent: Monday, July 31, 2006 2:39 PM
To: Geoff Devine; 'Livingood, Jason'; [email-masked]
Cc: 'Greg Herlein'; 'Ed Okerson'; 'Lipford,Mark A [CTO]'; 'Klaus
Darilion'; 'Henry Sinnreich'
Subject: RE: [Speermint] Voice codecs

I don't think you can mandate anything that guarantees only one
transcode.
However desirable it may be.

Brian

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From: Daryl Malas <[email-masked]>
Date: Mon, 31 Jul 2006 15:05:17 -0600

I agree with Geoff's statement below.