[asterisk-users] DTMF

[Dave Fullerton]

Jeff LaCoursiere wrote:
> Hmm, let me rephrase that (now that I have googled a bit).  I am having 
> trouble with DTMF tones over two IAX trunks:
> 
> Polycom501--->ast---[IAX]---ast2---[IAX]--->provider
> 
> Both IAX trunks were ulaw, and that worked fine.  I recently changed the 
> first leg to be g729 (as their internet connection is lower bandwidth). 
> Now DTMF doesn't seem to pass.
> 
> In my searches just now I see that dtmfmode is not actually a valid 
> keyword in iax.conf.
> 
> So may I assume that dtmfmode is inband only over IAX (since adding 
> compression seems to have killed it?).  That would suck.
> 
> j
> 

It is my understanding that DTMF in IAX is *always* sent out of band. 
Make sure  your Polycom and Asterisk are configured to use the same DTMF 
method in sip.conf. Polycom defaults to using rfc2833.

It could have been prior to the G729 switch the DTMF audio just happened 
to be inband from the Polycom and Asterisk was configured to something 
different. Asterisk therefore didn't detect and translate the DTMF to 
out of band when it went over the IAX trunk.

-Dave