[asterisk-users] Are there any settings for DTMF detection?

Dan Cropp dan at amtelco.com
Fri Mar 12 12:17:50 CST 2021

One of my co-workers just migrated from a Samsung phone to a Pixel 5 phone.
An app on the phone dials into our asterisk.
He has the same app installed on both and can move the SIM card between them.

Call is answered and a prompt plays to collect digits.
The app dials a number followed by a pound (example 1234#).
Asterisk and our AMI based application sees this and everything is good so far.

Another play begins to ask for another set of DTMFs.
Milliseconds after asterisk starts playing, it is reporting the DTMF # ended a second time.  The RTP is showing no new # being sent (1-2 seconds later phone dials digits for this second query)

What I determined when listening to a comparison of a tcpdump and the RTP streams:
Samsung has an interdigit timeout to the point you can hear a delay between the digits.  Just from listening, probably 150-200 ms between digits.
When listening to his Pixel 5 phone's RTP, the digits are speed dialed.  From listening, either there is no pause between digits or it is extremely small.

This is PJSIP and DTMFs are inband.

Are there any configuration setting in asterisk to adjust the amount of time between digits?
Any suggestions that I can try?


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