[asterisk-users] Codec Negotiation

[Woodoo People .pGa!]

> I have two polycom phones. One on a slow link, and one on a fast one.
> I'm trying to set the phone on the slow link to use G729 as it's first preference, and the phone on the fast link to use G711 as it's first preference.
> 
> sip.conf has:
> [general]
> allow=ulaw
> allow=g729
> 
> [slow-link] ; Override codecs for slow link phone.
> allow = g729
> allow = ulaw
> 
> When the slow link phone dialls the fast link phone, it sends G729 as it's first preference in the INVITE to Asterisk. Asterisk then sends G729 as the first preference in the INVITE to the fast link phone. Why doesn't Asterisk send G711 instead?
> 
> This raises an interesting question. If one phone uses G729, and one G711, then Asterisk is going to have to transcode, and I am going to use up a G729 license. It would seem more beneficial for it to work the way it is now. That is, both legs are using G729. Why is this better? It doesn't chew up a G729 license as there is no transcoding, and heck, if one of your call legs is G729, then the G711 party isn't going to hear anything better anyway.
> 
> Thoughts?

don't forget the following:
if canreinvite=yes, asterisk will NOT stay in mediapath, so, it going to ask both parties to negotiate codec, and say hello to the stream.
(if both parties supports g729, and can negotiate it, no licence will be used)
if canreinvite=no, * will STAY in mediapath, so both parties will negotiate with asterisk itself, and will not care about other side.
that means, if caller has g729, and callee has g711, asterisk WILL transcode. if both parties have g729, asterisk will NOT transcode, but
2 licence will be used!

as i experienced, the codec order in sip.conf [general]  will take priority over [user]  

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