[asterisk-users] Codec Negotiation

[Douglas Garstang]

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?