I’ve noticed some strange behavior with DTMF with SIP on asterisk in two different configurations.
Both Asterisk systems are running asterisk with SIP, one has about a month old CVS HEAD on Broadvoice, the other has asterisk 1.0.9 on Teliax.
Broadvoice uses inband dtmf and teliax by default uses rfc2833. We’re switching the teliax system to use inband to see if it helps at all.
Both systems exhibit the problem where dtmf tones are often read multiple times, for example, pressing 208 can sometimes be interpreted as 2208, 2008, or 2088. It seems to work better if you press the numbers slower, leaving a 0.5 to 1 second delay between each digit pressed.
I have experienced this both dialing out from a sip phone to an external IVR system as well as dialing in from an external phone to the internal Asterisk IVR system, it all seems to be related to asterisk’s handling of SIP and DTMF. Is it really this unreliable to use DTMF with Asterisk+SIP?