[Freeswitch-users] DTMF from cell phones

[Michael Jerris]

On Dec 5, 2008, at 6:08 AM, Jan Kubr wrote:

> Hi,
> recently someone was mentioning an issue with DTMF here, but there was
> no solution. I have a similar problem, when calling Freeswitch from my
> cell phone (via a SIP provider), sometimes DTMF is not recognized
> (read app doesn't terminate). I could not find any regularity in this,
> sometimes it is recognized just fine, sometimes I had to wait for the
> file to be played etc. The important thing to note is that when using
> a SIP softphone (X-Lite) I have never had this problem, DTMF is
> recognized perfectly. So it's probably related to GSM or something.
>
> I was wondering whether anyone experienced the same and whether there
> is something I can do about it. There are a few DTMF-related variables
> in the config files (dtmf-duration, pass-rfc2833, rfc2833-pt,
> dtmf-type, default_dtmf_duration, max_dtmf_duration) and I played with
> them a bit, but I don't really know what I'm doing.. Couldn't find any
> docs, either.
> Any ideas would be appreciated.

If it is coming from the sip provider as rfc 2833 dtmf, they are  
probably doing inband detection and failing at it.  If you look at an  
rtp dump you can confirm this.  If this is the case, there is nothing  
you can do on the FreeSWITCH side and the provider will have to fix it.

Mike