[asterisk-users] Random DTMF Tones Only on heard on ATA

[Sherwood McGowan]

Sorry, I came into this late...what codec is the device using, and is
the audio being trascoded?

Back at Voxitas, we had a couple of customers complain about random
DTMF tones coming across their line, and Asterisk WAS actually
"hearing" DTMF tones...want to know what it was?.....

In that particular case (just a place to start looking) it was G729 on
customer ATAs (don't remember the models)....Here's the freaky
thing....It only happened with CERTAIN people talking on the
phone...IIRC, we determined that the ATA's G729 processor was
mistaking certain audio frequencies in the speaker's voice and
believing it was a DTMF tone from the analog device and sending the
appropriate DTMF signal to our servers...

I'm sorry, I don't remember how we fixed it...I think we did some
audio tweaking (advanced ATA config, input level, out level, etc..),
be we may have just ended up having to tell that client to not use
G729 on those ATAs....

This _MAY_ happen with other codecs, but I think it's mainly either
G729..maybe primarily transcoding?


NERDY FUn Crap below:

capture SIP and RTP between your Asterisk and an offending device
(writing to a file)....then start doing everything you can to cause
the DTMF issue to occur. NOW, open your capture in wireshark...dump
the RTP payload to a file and open that file in an audio editor....

Now, go through the wireshark capture...see if you see any DTMF events
(if rfc2833 it'll be an RTP EVENT, if SIP INFO, it'll be a sip info,
and if you're using inband **SHUDDER** you can just listen to the
audio).....note the time in seconds from the beginning of the audio
stream whenever a DTMF event occurs, and then go to that spot in the
audio file....If you're feeling REALLY frisky, do a frequency
analysis...I'll bet you'll see that the voice that is speaking at the
time of the DTMF event on your various captures will have a frequency
range in common...a very close range...maybe look up DTMF tone
definition and get the freqs....(did it....more detail than even I
feel like doing right now :D)

Cheers,
Sherwood McGowan

On Wed, Jul 28, 2010 at 6:43 PM, Travis Langhals <travis at netitek.com> wrote:
> SIP/5211 is a Grandstream device.
> Did not add relaxdtmf=no, but sip show settings verifies it's already set to
> no.
> Fat fingered the version, it should have said 1.6.2.6 through 1.6.2.10
> Travis
>
> On Wed, Jul 28, 2010 at 3:12 AM, Benny Amorsen <benny+usenet at amorsen.dk>
> wrote:
>>
>> Travis Langhals <travis at netitek.com> writes:
>>
>> > [2010-07-27 10:34:42] DTMF[9744] channel.c: DTMF begin '1' received on
>> > SIP/5211-00000078
>>
>> Is SIP/5211 a Linksys or a Grandstream or something else?
>>
>> Do you have relaxdtmf=no?
>>
>> Also, your Asterisk version numbers are incorrect. Do you mean 1.6.2.10?
>>
>>
>> /Benny
>>
>
>
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