From: Thomas Tonino <ttonino@users.sf.net>
To: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [Asterisk] DTMF noise
Date: Tue, 07 Jan 2003 20:08:18 +0100 [thread overview]
Message-ID: <3E1B25A2.7020508@users.sf.net> (raw)
In-Reply-To: <20030107150006$4896@gated-at.bofh.it>
Mark Spencer wrote:
> The DTMF detector in the linux kernel is fairly simplistic and doesn't do
> many relative energy tests. The Zapata library has a much better tone
> detector, but it is FP, and so would have to be made fixed point. If
> nothing else, it may provide some lessons for the ISDN folks.
I remember that a good DTMF decoder can be very simplistic: DTMF was designed
for that.
The idea is:
- separate the high tones from the low tones.
- amplify clip the high band and the low band separately
- run the tone decoders on the clipped signals
The clipping stage would make sure that only relatively pure tones will trigger
the detector.
See also http://groups.google.com/groups?selm=7462%40accuvax.nwu.edu
Thomas
next parent reply other threads:[~2003-01-07 18:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20030107140012$1b66@gated-at.bofh.it>
[not found] ` <20030107150006$4896@gated-at.bofh.it>
2003-01-07 19:08 ` Thomas Tonino [this message]
2003-01-07 22:46 ` [Asterisk] DTMF noise Roy Sigurd Karlsbakk
2003-01-08 7:51 ` Thomas Tonino
2003-01-08 12:43 ` David D. Hagood
2003-01-08 13:04 ` Matti Aarnio
2003-01-08 15:49 ` Wolfgang Fritz
2003-01-08 16:30 ` Wolfgang Fritz
2003-01-08 19:48 ` Andrew McGregor
2003-01-08 22:19 ` Jamie Lokier
2003-01-09 12:51 ` David D. Hagood
2003-01-09 13:31 ` Wolfgang Fritz
2003-01-09 23:32 ` David D. Hagood
2003-01-10 6:52 ` Matti Aarnio
2003-01-10 12:42 ` David D. Hagood
2003-01-10 12:03 ` Roy Sigurd Karlsbakk
2003-01-08 20:22 ` Thomas Tonino
2003-01-09 12:42 ` David D. Hagood
2003-01-07 13:55 Roy Sigurd Karlsbakk
2003-01-07 14:49 ` [Asterisk] " Mark Spencer
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