With the change to sip_general_custom.conf listed above, and the g729 sounds files extracted, the system is now using g729 on all internal and external calls. Not the mixed solution originally asked for, but at least trunk calls are on the compressed codec. We’ll see how that sounds…
I wrote this up here: Get Asterisk to Use the G.729a Codec.
Update 11/5/2011: I had to set the Preferred Codec of my SPA3102 to G729a for inbound calls. And it seems we still need a transcoder to handle some voicemail and other functions, but the pass-through means far less transcoding. Blog post updated.
Mark Berry
MCB Systems