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.\" $NetBSD: dtmfdecode.1,v 1.3 2002/02/08 01:38:48 ross Exp $
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.\"
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.\" Copyright (c) 1999 Hellmuth Michaelis. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $Id: dtmfdecode.1,v 1.3 2002/02/08 01:38:48 ross Exp $
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.\"
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.\" $FreeBSD$
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.\"
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.\" last edit-date: [Mon Dec 13 22:53:13 1999]
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.\"
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.\"
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2001-04-09 17:21:45 +04:00
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.Dd February 15, 1999
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.Dt DTMFDECODE 1
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.Os
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.Sh NAME
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.Nm dtmfdecode
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.Nd decodes DTMF tones from A-law audio data
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.Sh SYNOPSIS
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.Nm
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.Sh DESCRIPTION
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.Nm
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is part of the isdn4bsd package and is used to detect DTMF tones in the
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audio stream.
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.Pp
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It reads audio G.711 A-Law coded data from stdin and outputs the detected
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numbers values as ASCII charcters to stdout.
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.Pp
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The detector is implemented as 8 narrow band-pass filters realized with
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an integer double-cross recursive algorithm. Various ad-hoc methods are
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employed to provide hysteresis and anti-bounce for the detected signals.
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.Sh EXAMPLES
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The command:
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.Bd -literal -offset indent
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dtmfdecode \*[Lt] beep.al
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.Ed
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.Pp
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will print a "1" to stdout.
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.Sh STANDARDS
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ITU Recommendations G.711
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.Sh AUTHORS
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The
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.Nm
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utility was written by
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.An Poul-Henning Kamp Aq phk@freebsd.org .
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This man page was written by
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.An Hellmuth Michaelis Aq hm@freebsd.org .
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