[Freeswitch-users] inband DTMF bleeding through

Avi Marcus avi at avimarcus.net
Mon Mar 11 11:58:28 MSK 2013


Get a PCAP of your incoming call. (pcapsipdump?)

Likely, your carrier is passing along the DTMF inband, perhaps as well as
rfc2833. Or maybe they do clamp down as they convert it to rfc2833, but it
takes time and some bleeds through.
(Your logs will show how the dtmf got received -- see if start_dtmf got
triggered.)

As far as I can tell, FS has no feature to *remove* inband dtmf.

-Avi


On Mon, Mar 11, 2013 at 10:47 AM, Matt Broad <matt at inveroak.com> wrote:

> Hi,
>
> I have the following dialplan in my public folder (the dest_number below
> is just an example):
>
> <include>
> <extension name="dialExt1002">
>  <condition field="destination_number" expression="^(1234)$">
> <action application="set" data="drop_dtmf=true"/>
>  <action application="export" data="drop_dtmf=true"/>
>                         <!-- Add a bind_meta_app just to make sure that
> the rfc2833 is still being picked up -->
>   <action application="bind_meta_app" data="4 b s
> execute_extension::att_xfer XML features"/>
>  <action application="set" data="ignore_early_media=true" />
> <action application="set" data="ringback=${uk-ring}"/>
>  <action application="set" data="call_timeout=30"/>
> <action application="bridge" data="user/1002"/>
>  </condition>
> </extension>
> </include>
>
> I am trying to prevent the DTMF tones from being heard by the b-leg (in
> this case user/1002).
> This works fine if the extension is called by a registered softphone (the
> user_context is set to public). The digits are pressed and no beeps or
> tones are heard by the other side.
>
> If this extension is dialed by a landline/mobile number, when a digit is
> pressed there is a slight "bleeding" of the DTMF.  Enough to distinguish
> between different digits, though probably not enough to determin the digit
> pressed.
>
> I have tried several things such as stop_dtmf in the dialplan, setting
> the dtmf-duration to 0 (not quite sure what this param does but tried it
> anyway :) ) in the sip profile but nothing seems to prevent it.
>
> Could it be our provider? They have confirmed that they use out-of -band
> rfc2883. But without the drop_dtmf being set in the dialplan the full tone
> is heard. Could they be sending inband and out-of-band?
>
> Could anyone suggest any tests I could run or any log files I could look
> at please?
>
>
> Many Thanks
> Matt
>
>
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