[Freeswitch-users] Inband DTMF Problem

Brian West brian at freeswitch.org
Wed Nov 5 07:14:55 PST 2008

Inband DTMF on voip isn't the most reliable thing in the first  
place... anyway to use RFC2833 or SIP Info?


On Nov 5, 2008, at 9:08 AM, Klaus Teller wrote:

> Hi Folks,
> It's me again with a DTMF issue. Here is what's going on. I have a  
> remote IVR and i'm writing some code to communicate with it,  
> exercise it, and test it. The remote IVR is playing DTMF as inband.
> Right now, Freeswitch can detect all DTMF digits from the IVR. The  
> interaction between my code and the IVR is essentially  a  
> combination of  playing files and sending and reading DTMFs.
> The issue: whenever my code plays a file or send a DTMF digit, the  
> following attempt to read DTMF fails. By failing i mean that there  
> will be a spurious DTMF detected by Freeswitch that was not sent by  
> the IVR.
> That is, if i have something like:
> sendDTMF("3"); getDigits("38373", "#");  // # is the termination  
> character
> After executing the sendDTMF, getDigits fails because it immediately  
> detects a pound. Yet this pound is not sent by the IVR. I can check  
> this by having wireshark running both on the IVR's computer and on  
> Freeswitch's computer.
> Any idea what may be causing this problem? Is there some sort of  
> Echo going on or something like that?
> Thanks,
> Klaus.

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