[Asterisk-Users] Codec negotiation

[Steven Critchfield]

On Sat, 2004-11-20 at 18:48 +0100, Tamas J wrote:
> Hello!
> 
> I would like to know wether it is possible to have end-to-end codec
> negotiation in iax2?
> What I mean is...
> 
> In case the user dials a number available through PSTN, let's force to
> use alaw (the client is in LAN) to overcome unneeded transcoding:
> iaxphone->1st asterisk -> PSTN
> 
> In case the same user dials a number available throug a chain of IAX2
> peers (e.g. 2 peers), try to negotiate the codec end-to-end to consume
> less resources for transcoding on asterisk servers (of course, in that
> case we don't want to use g711, but ilbc, speex or gsm).
> iaxphone->1st asterisk->2nd asterisk->PSTN
> Or maybe:
> iaxphone->1st asterisk->2nd asterisk->iaxpohone
> 
> Is there a way to do that? If yes, how?

If 1st asterisk -> 2nd asterisk is a link that negotiates the ILBC, gsm,
or speex, when the call transfers, it should negotiate the codec. Of
course part of the interesting effect here is that unless there is NAT
or something similar in the way, IAX is going to try and get out of each
section if it can. So you may end up with the end result being iaxphone
-> iaxphone and they might be negotiating with each other.
-- 
Steven Critchfield <critch at basesys.com>