[Asterisk-Users] dtmfmode=inband but SDP also indicates rfc2833

[Stagg Shelton]

I'm trying to figure out a way around a problem that I'm having.  My 
carrier sends me a SIP INVITE that indicates that the dtmf modes 
available are inband (0), and rfc2833 (101).  My asterisk server 
(1.2.9.1) sends back a 200 OK message and shows in its SDP Media 
Description that we accept inband (0) and rfc2833 (101).  My carrier 
therefore sends all DTMF via rfc2833 which obviously causes problems 
since asterisk is configured for inband.

I've tried going pure rfc2833 with the carrier, and am having DTMF 
related problems.  From the research that I have done with my issue it 
seems to be a problem with the way asterisk sends the rfc2833 packets 
out at nearly the same time.  Altering the timing that asterisk uses to 
send the rfc2833 packets seems too deeply seated in asterisk.  I 
therefore have settled on the idea on using inband for dtmf.  My 
termination tests using inband have been successful.

So here is what i think will solve my particular problem.  I just want 
to respond with a 200 OK that does not contain anything about rfc2833 in 
the SDP.  Is this fairly doable.  I've been diging through chan_sip.c 
and think I could just make a couple of modifications to make asterisk 
do what I need it to.  I'm hoping to have someone who is familiar with 
chan_sip.c enlighten me as to whether or not this can be done, and what 
functions I would need to modify in order to make it happen.

Thank You
Stagg Shelton
www.oneringnetworks.com