Setting calling party's codec in the dialplan

[jbh]

This may be well known, but took me a while to figure out.

To make a phone originating a call use a particular codec (ulaw) when calling out via a trunk, I added this to extensions_custom.conf:

[from-internal-custom]
; Do not use an Answer() command
; It breaks it- at least it does in Asterisk 1.6.1.10
;Use ulaw when dialling via an outbound route with prefix 9

exten => _9.,1,Set(SIP_CODEC=ulaw)
exten => _9.,n,Dial(SIP/${EXTEN})
exten => _9.,n,Hangup()

 

[blanchae]

Could you not add these lines in the FreePBX trunk "Outgoing Settings"?

disallow=all
allow=ulaw

Add them to this example trunk outgoing settings:

 

[blanchae]

My method would force the trunk but it may not force the calling phone. Interesting problem. But then again, the extension may negotiate with the trunk for the proper codec. Need someone smarter than me to confirm if this would work or not.

 

[jbh]

In my settup putting the rule in the trunk forces the outgoing codec in the trunk but may leave the PBX needing to transcode. This is one method to avoid the transcoding.