I’m trying to force any calls coming from/to an extension to use only the ulaw codec.
This extension (Cisco SPA122 used as an ATA for a fax) is configured to only use ulaw. I’ve verified with a packet capture that it’s only sending PCMU/8000 in it’s INVITE to asterisk.
The extension has:
And the outgoing SIP trunk has
set in pjsip.endpoint.conf.
When Asterisk sends the INVITE to the SIP trunk, it includes G722 and G729 in the SDP offer (as well as PCMU). The trunk seems to always negotiate to G729, so Asterisk ends up transcoding the ulaw to G729 between the two, and faxes have lots of issues.
I know I can just set the SIP trunk to only allow ulaw, and everything works properly, but I’d like to have
have my normal extensions use G729. I can’t find a way to stop Asterisk from offering the disallowed codecs.