The begin frames (and associated end frames) are helpful to filter out short dtmf reads. There's even a #define which specifies the minimum length of a dtmf tone. One problem we're having is multiple dtmf detections on a noisy cell phone connection, which should be mostly filtered by knowing the begin and end time so that the length can be properly measured and filtered if needed.
<br><br>John<br><br><div class="gmail_quote">On Dec 2, 2007 6:58 PM, Dmitry Andrianov <<a href="mailto:dimas@dataart.com">dimas@dataart.com</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div link="blue" vlink="purple" lang="RU">
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<p><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US">As far as I understand, Asterisk DSP code does not generate DTMF_BEGIN
frames (at least unless DSP_DIGITMODE_MUTECONF+DSP_DIGITMODE_MUTEMAX flags are
passed to DSP – I do not completely understand that branch of code). This
means it is not problem with your configuration, it is the way how DSP code
works now.</span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US"> </span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US">I believe this can be easily fixed if anyone needs these BEGIN frames.</span></p>
<p><span style="font-size: 11pt; color: rgb(31, 73, 125);" lang="EN-US"> </span></p>
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<p><b><span style="font-size: 10pt;" lang="EN-US">From:</span></b><span style="font-size: 10pt;" lang="EN-US"> <a href="mailto:asterisk-dev-bounces@lists.digium.com" target="_blank">asterisk-dev-bounces@lists.digium.com</a>
[mailto:<a href="mailto:asterisk-dev-bounces@lists.digium.com" target="_blank">asterisk-dev-bounces@lists.digium.com</a>] <b>On Behalf Of </b>John Aughey<br>
<b>Sent:</b> Sunday, December 02, 2007 3:20 PM<br>
<b>To:</b> <a href="mailto:asterisk-dev@lists.digium.com" target="_blank">asterisk-dev@lists.digium.com</a><br>
<b>Subject:</b> [asterisk-dev] DTMF end accepted without begin</span></p>
</div><div><div></div><div class="Wj3C7c">
<p> </p>
<p>I was having problems with consistent DTMF detection on a
FXO Zap device, so I turned on DTMF logging. I noticed that it always
reports "DTMF end accepted without begin" for every digit
pressed. I've verified this on 1.4.15 and the latest svn release.
It indicates a duration of 0ms which is consistent with not receiving a begin
event. The tones get "detected", but it can't do any filtering
based on duration this way.<br>
<br>
This seems to be a core problem that the Zap layer isn't passing on DTMF_BEGIN
events. Is this a known issue or is anyone working on this problem?
Or could I have something messed up in my own configuration?<br>
<br>
Thanks<br>
<br>
John Aughey</p>
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