[asterisk-users] Codec Negotiation

[Martin Joseph]

On Jul 17, 2006, at 9:25 AM, Douglas Garstang wrote:

> 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?
Because you set the calling to prefer g729? What did you expect?
>
> 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.
Exactly.  In fact I would generally force g729 in that case (ie 
disallow all but g729).
> 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.
Yes this is clearly a win.