[asterisk-dev] DTMF end accepted without begin

[Dmitry Andrianov]

Well, to me it sounds like business of DSP code itself to do such a filtering.
It sounds like bad idea if DSP will be detecting "raw" DTMF while some upper-level code (like channel driver or even application code) is post-processing it eliminating false alerts.

So it is not question of generating BEGIN frames, it is more like a question of improving DTMF detection in DSP.

From: asterisk-dev-bounces at lists.digium.com [mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of John Aughey
Sent: Monday, December 03, 2007 4:35 AM
To: Asterisk Developers Mailing List
Subject: Re: [asterisk-dev] DTMF end accepted without begin

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.

John
On Dec 2, 2007 6:58 PM, Dmitry Andrianov <dimas at dataart.com<mailto:dimas at dataart.com>> wrote:

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.



I believe this can be easily fixed if anyone needs these BEGIN frames.



From: asterisk-dev-bounces at lists.digium.com<mailto:asterisk-dev-bounces at lists.digium.com> [mailto:asterisk-dev-bounces at lists.digium.com<mailto:asterisk-dev-bounces at lists.digium.com>] On Behalf Of John Aughey
Sent: Sunday, December 02, 2007 3:20 PM
To: asterisk-dev at lists.digium.com<mailto:asterisk-dev at lists.digium.com>
Subject: [asterisk-dev] DTMF end accepted without begin



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.

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?

Thanks

John Aughey

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