Summary:ASTERISK-11444: snom DTMF duration detected wrong
Reporter:tbsky (tbsky)Labels:
Date Opened:2008-02-15 03:04:48.000-0600Date Closed:2011-06-07 14:07:54
Versions:Frequency of
Environment:Attachments:( 0) snom-dtmf.txt
Description:i use asterisk 1.4.18 and zaptel 1.4.8.  ip phone is snom 300 with firmware 7.1.30
the snom DTMF payload type is 101, and asterisk DTMF is rfc2833.
snom can not use DTMF.  asterisk will set the DTMF duration wrong.
please see snom-dtmf.txt
Comments:By: Olle Johansson (oej) 2008-02-16 04:56:18.000-0600

[Feb 14 09:09:14] DTMF[20816] channel.c: DTMF end '1' received on SIP/3340-0825f060, duration 74617280 ms

That is a very long DTMF tone.

By: Nir Simionovich (GreenfieldTech - Israel) (greenfieldtech) 2008-02-17 05:40:10.000-0600


I have a friend who has a similar problem. However, with his system this occurs only when terminating the call to a PSTN, while DTMF's SIP-to-SIP happen normally.

I think above rules out a SNOM bug.


By: Olle Johansson (oej) 2008-02-17 06:26:05.000-0600

If you check, I'm sure we're sending SIP2SIP traffic either outside of Asterisk or in the native p2p bridge, which means that Asterisk doesn't handle it at all.

Was the SIP2SIP call from a Snom to another brand of SIP phone, or to another SNOM?

By: Nir Simionovich (GreenfieldTech - Israel) (greenfieldtech) 2008-02-17 06:42:41.000-0600

Well, the call that works fine is a SIP-2-SIP call, going to a LinkSys PAP2.

By: Olle Johansson (oej) 2008-02-17 06:49:26.000-0600

Ok, thanks for the quick feedback. I agree with you, then we have an Asterisk issue to fix.

By: Nir Simionovich (GreenfieldTech - Israel) (greenfieldtech) 2008-02-17 07:04:05.000-0600

you're welcome

By: Joshua C. Colp (jcolp) 2008-02-18 11:36:14.000-0600

Please provide an rtp debug so we can narrow this down a bit more.

By: Richard Begg (meric) 2008-02-20 14:47:13.000-0600

This is a SNOM bug.  I reported it to them months ago, but still haven't seen a fix.

It seems that the first SIP INFO message sent (since the phone was booted) contains an invalid duration.  Subsequent messages are ok.

The reason it doesn't affect SIP2SIP calls is that most SIP devices ignore the duration field anyway.  It's a problem with PSTN calls via asterisk, because asterisk uses the duration to generate the tones.

I went through the asterisk code a while back, and what it does is suppress all other audio while in tone generation, which given the duration provided by the SNOM phone is *quite* a while.  The result for the end-user is a call which appears to have dropped out.

I've uploaded my crude workaround which clamps the DTMF duration on all INFO messages.  It isn't something which belongs in Asterisk, but might be useful as a temporary solution.

By: Nir Simionovich (GreenfieldTech - Israel) (greenfieldtech) 2008-02-20 14:56:22.000-0600

Well, in that case, why not simply add this clamping feature into the sip.conf general configuration, allowing the admin to set the maximum duration for a DTMF over SIP connections. If SNOM messed up and are not willing to fix, I think a general variable to address the issue should be put into the code.

meric, can you please upload your patch into the ticket, so that we can take a look at it. I'm still new to the channels code, but I'd like to take a wiff at it, and try to make this into a configuration option or something.

By: Richard Begg (meric) 2008-02-20 18:57:59.000-0600

I've uploaded the patch, but it's still pending the license mumbo-jumbo before it's publicly viewable.  Hopefully it will pop up soon.

I've renewed my pursuit of SNOM over this and one other DTMF feature, so maybe we'll see some action in the next 6 months or so :-)

Another workaround is to revert to inband DTMF - although not an option if you're using any of the low-bitrate codecs like g.729.

By: tbsky (tbsky) 2008-03-04 22:13:25.000-0600

  my snom 300 problem seems solved.
  i tried a snom 320 with firmware 7.1.8, and found DTMF is ok.
  i upgrade the firmware to 7.1.30 and it is ok too!
  this inspires me.
  why my snom 300 with the same firmware 7.1.30 is broken.
  i re-flash the firmware, it is still broken.
  i do a reset to factory default, and the DTMF is working now!!
  there must be some hidden garbage settings inside when upgrade snom firmware
from 6.5 to 7.1.30.
  do a factory reset seems cure the misbehavior for me.

By: Joshua C. Colp (jcolp) 2008-03-12 16:33:34

Closed per reporter.