When dtmfmode is set to inband for SIP, and i originate a call from sip
out to the PSTN, I can hear the DTMF digit twice in the audio stream.
Once very briefly and once for normal duration.
Our Theory: 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.
Is anyone else experiencing this?
I have reproduced this in an environment
* with one asterisk server that is both the feature server and the
media gateway, and is timing off of network T1s
* with two servers, one feature server (timing off of ztdummy) and
one media gateway (timing off of network T1s) using IAX as the inter
asterisk protocol
It is pretty easy to reproduce:
-Dial a PSTN number(like your cell) from a sip phone using inband DTMF,
and configured in asterisk sip.conf with dtmfmode=inband.
-Answer the PSTN end.
-Press and hold a digit on the sip phone. On the PSTN phone you will
hear a very brief, end user generated, tone.
-Let go of the digit on the sip phone. On the PSTN phone you will hear
the asterisk generated tone.
Can anyone else hear the brief initial tone? Any help is greatly
appreciated!
There is a good wiki article on DTMF:
http://www.voip-info.org/wiki/view/Asterisk+DTMF
and there has been a thread about it on this mailing list:
http://lists.digium.com/pipermail/asterisk-users/2007-March/181461.html
We have opened a bug report:
http://bugs.digium.com/view.php?id=9382
Some System Specifications:
Asterisk 1.2.14
Digium Wildcard TE405P/TE410P
CentOS release 4.4 (Final)
--
Ken W. Leland III
Engineering
k3leland@monmouth.com
Monmouth Telecom
10 Drs. James Parker Blvd., Suite 110
Red Bank, NJ 07701
732-704-1000 X283
On 5/3/07, Ken Leland III <k3leland@monmouth.com> wrote:> When dtmfmode is set to inband for SIP, and i originate a call from sip > out to the PSTN, I can hear the DTMF digit twice in the audio stream. > Once very briefly and once for normal duration. > > Our Theory: 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. > > Is anyone else experiencing this? > > I have reproduced this in an environment > * with one asterisk server that is both the feature server and the > media gateway, and is timing off of network T1s > * with two servers, one feature server (timing off of ztdummy) and > one media gateway (timing off of network T1s) using IAX as the inter > asterisk protocol > > It is pretty easy to reproduce: > -Dial a PSTN number(like your cell) from a sip phone using inband DTMF, > and configured in asterisk sip.conf with dtmfmode=inband. > -Answer the PSTN end. > -Press and hold a digit on the sip phone. On the PSTN phone you will > hear a very brief, end user generated, tone. > -Let go of the digit on the sip phone. On the PSTN phone you will hear > the asterisk generated tone. > > Can anyone else hear the brief initial tone? Any help is greatly > appreciated!Yes, we have a similar issue, but do not normally use inband DTMF because SIP phones very cleanly generate rfc2833 RTP packets directly and remove this issue. On the other hand, asterisk is not alone dealing with this issue in SIP. The Linksys ATAs have exactly the same issue. Strangely, I do not have a problem receiving inband DTMF through Zaptel, which I believe uses the same DSP code for DTMF detection... Or does it? Steve