[Freeswitch-users] DTMF bleed through in conference

[David Bolen]

Anthony Minessale <anthony.minessale at gmail.com> writes:

> even when you have 100% soft phones you hear the blip?
> Do you hear the blip on every phone?

Of the two phones in my recent tests, the DTMF originator was the soft
phone, the other participant was an analog handset through the PAP2T.
Both were muted (locally on the analog phone, and in the software for
the soft phone). I can try a test with just multiple soft phones
though.

I seem to get the exact same thing regardless of DTMF source (soft
phone, analog through PAP2T, analog through PSTN independent of
gateway) or other participants on the call.  So if the tone was
in-band, it would have to be multiple similar failures of all those
sources.

And yes, though I haven't run that as recently, if there are >2
participants I'm pretty sure all others other than the DMTF source
hear the blip.

> Something in the mix must be doing generated tones or you would not
> hear them.  FS would not just invent them.

That certainly seems to be the simplest/most plausible answer, I just
don't know how it could be happening with the softphone as DTMF
source since there should be no in-band tone.

I did see where mod_conference can have a member flag to replicate
DTMF to other participants, but I don't have that on, so I don't think
that's it.  It would probably be a full tone too, not the brief burst.

I'm sure it's got to be explainable, but so far I guess I just haven't
looked in the right place.

-- David