DTMF (inband) Deutsche Telekom All-IP problem

Asterisk Asterisk Support
1

We are running a asterisk IVR system controlled by dtmf

Every “normal” provider uses rfc2833 to transmit keystrokes which works fine

“Deutsche Telekom” in germany introduced some time ago so called ALL-IP product. This meanes Telekom switches to VOIP

Problem is that asterisk does not recognize dtmf keystrokes. Reason seams to be, that telekom does signal rfc2833 but sends keystrokes only as DTMF-inband

FreeSwitch seems to have a feature called “spandsp_start_dtmf”. Using this FreeSwitch can (not tested) recognize rfc2833 and inband in parallel.

Is there some solution for asterisk?

I tried sip and pjsip (with 13.9.1) but inband is not recognized.

2

What happens if you explicitly set the configuration to inband? Does it then work? Do you need to send in RFC2833, but accept inband?

3

Thank you for your answer.

Setting fixed to inband results in randomly duplicate DTMF digits when using non-telekom line. And i can not garantue that all other clients support inband DTMF. Telekom client works fine with inband.

And … in my opinion out-of-band signalling is the future and DTMF-Inband is deprecated. I can not understand why telekom decided to use inband …

4

Does Deutsche Telecom uses Huawei IMS softswitch?

5

Sorry i do not know. How can i check this? Is this transmitted in SIP headers?

6

Any Ideas? I need to detect RFC2833 and INBAND Tones in parallel …