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I have seen a similar scenario play out when transmitting DTMF via
RFC2833 when the negotiated codec is G711, and the gateway is
configured to accept both in-band and RFC2833. <br>
<br>
What we eventually found was happening was a faint echo of the DTMF
as produced by the handset as user-feedback was echoing back into
the handset microphone, and causing a faint "echo" of dtmf so there
was faint in-band, as well as rfc2833 event packets, and the gateway
would try to render them both. This naturally caused all kinds of
headache. As a litmus test, you might switch the negotiated codec to
G729 and see if the DTMF gets more reliable since it takes the
in-band confusion off the table. <br>
<br>
We had this exact problem with a very large tier 1 carrier whose
border controllers are configured to accept both in-band and
RFC2833, and re-constitute it all into in-band across their core,
and we wound up getting duplicate digits out to the PSTN for no
reason we could discern. <br>
<br>
<br>
<br>
On 02/15/2012 10:40 PM, Peter Childs wrote:
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<div>Gday folks.</div>
<div><br>
</div>
<div>I'm working through one of those lovely DTMF issues and have
notice that a particular CPE that is experiencing a DTMF fault
on our network sends both rfc2833 rtp packets _and_ the tone in
audio stream (not named rtp packets, but how the device has
'heard' the tones from the originating handset).</div>
<div><br>
</div>
<div>Just wondering if this sounds 'normal', or is common, or is
broken. It appears to be causing the media-gateway on our end
to sends some pretty awful junk to line (ds0) that is not
recognised by most 'PSTN' connected equipment.</div>
<div><br>
</div>
<div>Thoughts or comments?</div>
<div><br>
</div>
<div>Ta.</div>
<br>
<div><span class="Apple-style-span" style="border-collapse:
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<div>
<div>--</div>
<div> Peter Childs - Voice Engineer</div>
<div> Internode/Agile</div>
<div> Ph: 08 8228 2380 Mb: 0406 388 405 Fax: 08 8235 6801</div>
</div>
</span></div>
<br>
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