Summary:ASTERISK-16021: Inband DTMF Double digits being sent.
Reporter:Ken Leland (kenlee)Labels:
Date Opened:2010-04-27 12:01:42Date Closed:2011-07-26 15:17:08
Versions:Frequency of
Description:When dtmfmode is set to inband for SIP, and a zap channel is bridged with the SIP channel, and the user on the zap channel side presses a digit, you can hear the DTMF digit twice in the audio stream. This happens while Asterisk is parsing the DTMF. For a fraction of a second, while the end user generated DTMF is being detected, the DTMF is passed inband. Once the DTMF is detected Asterisk silences it and regenerates it. Sensitive machines like auto attendants pick up both the brief end user generated tone as well as the full length asterisk generated tone and ultimately perceive each digit twice.


We measured the effect of this bug with a Metro-Tel Corp Digit Grabber, Model TPM32. We were able to detect 1 out 100 double digits very reliably.

Check out the patch on the reviewboard.
Comments:By: Ken Leland (kenlee) 2010-04-27 12:04:10

Related issues:

0009382, 0011968, 0016243

Note that 0016243 was closed as per my testing incorrectly.  What occurred was a significant redesign in main/dsp.c that brought the problem from a 5% error rate that was audible by the human ear to a 1% error rate that is not audible by the human hear.  This is why i mistook it as a fix.

By: Leif Madsen (lmadsen) 2011-07-26 15:17:03.806-0500

Per the Asterisk maintenance timeline page at http://www.asterisk.org/asterisk-versions maintenance (bug) support for the 1.4 and 1.6.x branches has ended. For continued maintenance support please move to the 1.8 branch which is a long term support (LTS) branch. For more information about branch support, please see https://wiki.asterisk.org/wiki/display/AST/Asterisk+Versions

If this is still an issue, please open a new issue so it can be re-triaged appropriately. Thanks!