[Asterisk-Dev] IAX codec negociation (again...)

[Michael Giagnocavo]

I've run into the same issue. Search on Mantis for AgiNamu, and I have a few
patches that will allow you to do what you want to do.

The main issue, as others pointed out, is that Asterisk can get involved and
do lots of stuff. On top of that, at the time a call is placed (negotiated
with Asterisk), Asterisk does not know where the call will end up (since the
dialplan could be indefinite). Thus my patch relates to having you manually
specify which codec should be negotiated based on the called number.

As far as changing codecs in mid-call, I recall some discussion saying that
was "easy" and "already supported". But I don't think anyone has actually
done it.

Finally, yes, this can save BOTH bandwidth and CPU. This is because you
could negotiate down to G729 on both ends instead of transcoding ULAW->G729.

-Michael

-----Original Message-----
From: asterisk-dev-bounces at lists.digium.com
[mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of Goldenear
Sent: Monday, June 20, 2005 6:34 AM
To: Asterisk Developers Mailing List
Subject: [Asterisk-Dev] IAX codec negociation (again...)

Hi,

I wondering if codec negociation will soon be better in asterisk. I've 
installed the lastest CVS version of asterisk and I still have a problem:
user A wants to call user B
user A supports alaw, ulaw and gsm (with gsm as prefered codec)
user B only supports ulaw
So I guess that, theorically, user A could switch from gsm (prefered 
codec) to ulaw when calling user B (as it's the only commonly supported 
codec). This would avoid codec translation and could permet native bridging.

At the moment asterisk never does that and the call path is like this :

user A (iax2/gsm) --- (iax2/gsm) asterisk (iax2/ulaw) -- (iax2/ulaw) user B

Too bad :(

I'm not a programmer, but I guess this problem could be solved very 
easily. This would make asterisk better and could save many cpu and 
bandwidth :)

Please, let me know if somebody is working on this and if they are some 
patches I can test.

thanks,

Nicolas

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