125 lines
4 KiB
C++
125 lines
4 KiB
C++
/**
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* \file beacon.hxx -- Provides marker beacon audio generation.
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*/
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// Written by Curtis Olson, started March 2001.
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//
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// Copyright (C) 2001 Curtis L. Olson - curt@flightgear.org
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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//
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// $Id$
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#ifndef _BEACON_HXX
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#define _BEACON_HXX
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <simgear/compiler.h>
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#include <plib/sl.h>
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#include <plib/sm.h>
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#include "morse.hxx"
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#include "soundmgr.hxx"
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// Quoting from http://www.smartregs.com/data/sa326.htm
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// Smart REGS Glossary - marker beacon
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//
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// An electronic navigation facility transmitting a 75 MHz vertical fan
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// or boneshaped radiation pattern. Marker beacons are identified by
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// their modulation frequency and keying code, and when received by
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// compatible airborne equipment, indicate to the pilot, both aurally
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// and visually, that he is passing over the facility.
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// (See outer marker middle marker inner marker.)
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//
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// Smart REGS Glossary - outer marker
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//
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// A marker beacon at or near the glideslope intercept altitude of an
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// ILS approach. It is keyed to transmit two dashes per second on a
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// 400 Hz tone, which is received aurally and visually by compatible
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// airborne equipment. The OM is normally located four to seven miles from
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// the runway threshold on the extended centerline of the runway.
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//
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// Smart REGS Glossary - middle marker
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//
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// A marker beacon that defines a point along the glideslope of an
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// ILS normally located at or near the point of decision height
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// (ILS Category I). It is keyed to transmit alternate dots and dashes,
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// with the alternate dots and dashes keyed at the rate of 95 dot/dash
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// combinations per minute on a 1300 Hz tone, which is received
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// aurally and visually by compatible airborne equipment.
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//
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// Smart REGS Glossary - inner marker
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//
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// A marker beacon used with an ILS (CAT II) precision approach located
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// between the middle marker and the end of the ILS runway,
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// transmitting a radiation pattern keyed at six dots per second and
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// indicating to the pilot, both aurally and visually, that he is at
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// the designated decision height (DH), normally 100 feet above the
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// touchdown zone elevation, on the ILS CAT II approach. It also marks
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// progress during a CAT III approach.
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// (See instrument landing system) (Refer to AIM.)
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static const int INNER_FREQ = 3000;
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static const int MIDDLE_FREQ = 1300;
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static const int OUTER_FREQ = 400;
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static const int INNER_SIZE = BYTES_PER_SECOND;
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static const int MIDDLE_SIZE = (int)(BYTES_PER_SECOND * 60 / 95 );
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static const int OUTER_SIZE = BYTES_PER_SECOND;
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static const int INNER_DIT_LEN = (int)(BYTES_PER_SECOND / 6.0);
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static const int MIDDLE_DIT_LEN = (int)(MIDDLE_SIZE / 3.0);
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static const int MIDDLE_DAH_LEN = (int)(MIDDLE_SIZE * 2 / 3.0);
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static const int OUTER_DAH_LEN = (int)(BYTES_PER_SECOND / 2.0);
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// manages everything we need to know for an individual sound sample
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class FGBeacon {
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private:
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unsigned char inner_buf[ INNER_SIZE ] ;
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unsigned char middle_buf[ MIDDLE_SIZE ] ;
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unsigned char outer_buf[ OUTER_SIZE ] ;
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FGSimpleSound *inner;
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FGSimpleSound *middle;
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FGSimpleSound *outer;
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public:
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FGBeacon();
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~FGBeacon();
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// allocate and initialize sound samples
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bool init();
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FGSimpleSound *get_inner() { return inner; }
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FGSimpleSound *get_middle() { return middle; }
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FGSimpleSound *get_outer() { return outer; }
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};
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#endif // _BEACON_HXX
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