[Asterisk-Users] Re: DTMF not sending properly via IAX

[Tony Mountifield]

In article <Chameleon.1121164514.adar0 at vegas>,
Rich Adamson <radamson at routers.com> wrote:
> Not sure this applies, but a few months ago some of us were having
> problems with an itsp (livevoip.com) and incoming iax calls that 
> hit the * ivr. dtmf was essentially not being passed. I opened a
> bug, however Mark quickly closed it with a note "that's the way
> iax works; have the itsp fix their problem".
> 
> The issue at that time was oriented around a call that was considered
> "answered". If the end-to-end path of the call is considered answered,
> asterisk is no longer in the voice path to translate dtmf into iax
> out-of-band dtmf packets. Part of the argument was then "what is an 
> asterisk user suppose to do to pass dtmf across an iax link that uses
> g729"?  g729 won't reproduce the audio tones reliably, etc, etc.
> 
> Lurking behind all of that is a defacto telephony standard that
> essentially supports dtmf end-to-end regardless of what type of circuit
> is involved (dtmf passed in-band after answer). 
> 
> Is it possible that part of your issue might involve the answer status
> of the iax path?

I doubt it. The puzzling thing is that it used to work, and doesn't now.
So it is either something I've changed (I updated from April CVS-STABLE
to July CVS-STABLE), or something the provider has changed (I have
raised a ticket with them).

I'm not sure about your second paragraph. As I understand it, a device
that interfaces from TDM to IAX is supposed to detect DTMF tones, and
translate them into out-of-band IAX DTMF control frames. Conversely a
device going from IAX to TDM should generate outgoing inband tones
when it gets such DTMF control frames.

Surely if Asterisk is interfacing between IAX and TDM, it must remain
in the voice path all the time?

The salient feature of my current problem is that the first digit of a
SendDTMF string does get sent out inband by my provider, but subsequent
digits don't. My feeling is that it has something to do with seqnos or
timestamps in the DTMF control frames, but I don't know what.

I've even tried a loop in the dialplan to peel off the digits one by one
and send them individually using SendDTMF with a Wait(1) in between, but
it doesn't seem to help. However, after some other audio activity and a
delay, a fresh SendDTMF will again have its first digit converted to
tones, but not subsequent digits. Bizarre!

Cheers
Tony
-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org