146 lines
5.1 KiB
C++
146 lines
5.1 KiB
C++
// morse.hxx -- Morse code generation class
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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 _MORSE_HXX
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#define _MORSE_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 <simgear/sound/soundmgr_openal.hxx>
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// Quoting from http://www.kluft.com/~ikluft/ham/morse-intro.html by
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// Ian Kluft KO6YQ <ikluft@kluft.com>
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//
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// [begin quote]
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//
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// What is the Standard for Measuring Morse Code Speed?
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//
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// [This was adapted from the Ham Radio FAQ which used to be posted on UseNet.]
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//
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// The word PARIS was chosen as the standard length for CW code
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// speed. Each dit counts for one count, each dah counts for three
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// counts, intra-character spacing is one count, inter-character
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// spacing is three counts and inter-word spacing is seven counts, so
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// the word PARIS is exactly 50 counts:
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//
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// PPPPPPPPPPPPPP AAAAAA RRRRRRRRRR IIIIII SSSSSSSSSS
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// di da da di di da di da di di di di di di
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// 1 1 3 1 3 1 1 3 1 1 3 3 1 1 3 1 1 3 1 1 1 3 1 1 1 1 1 7 = 50
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// ^ ^ ^
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// ^Intra-character ^Inter-character Inter-word^
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//
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// So 5 words-per-minute = 250 counts-per-minute / 50 counts-per-word
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// or one count every 240 milliseconds. 13 words-per-minute is one
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// count every ~92.3 milliseconds. This method of sending code is
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// sometimes called "Slow Code", because at 5 wpm it sounds VERY SLOW.
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//
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// The "Farnsworth" method is accomplished by sending the dits and
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// dahs and intra-character spacing at a higher speed, then increasing
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// the inter-character and inter-word spacing to slow the sending
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// speed down to the desired speed. For example, to send at 5 wpm with
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// 13 wpm characters in Farnsworth method, the dits and
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// intra-character spacing would be 92.3 milliseconds, the dah would
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// be 276.9 milliseconds, the inter-character spacing would be 1.443
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// seconds and inter-word spacing would be 3.367 seconds.
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//
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// [end quote]
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// Ok, back to Curt
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// My formulation is based dit = 1 count, dah = 3 counts, 1 count for
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// intRA-character space, 3 counts for intER-character space. Target
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// is 5 wpm which by the above means 1 count = 240 milliseconds.
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//
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// AIM 1-1-7 (f) states that the frequency of the tone should be 1020
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// Hz for the VOR ident.
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static const char DI = '1';
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static const char DIT = '1';
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static const char DA = '2';
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static const char DAH = '2';
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static const char end = '0';
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static const int BYTES_PER_SECOND = 22050;
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// static const int BEAT_LENGTH = 240; // milleseconds (5 wpm)
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static const int BEAT_LENGTH = 92; // milleseconds (13 wpm)
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static const int TRANSITION_BYTES = (int)(0.005 * BYTES_PER_SECOND);
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static const int COUNT_SIZE = BYTES_PER_SECOND * BEAT_LENGTH / 1000;
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static const int DIT_SIZE = 2 * COUNT_SIZE; // 2 counts
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static const int DAH_SIZE = 4 * COUNT_SIZE; // 4 counts
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static const int SPACE_SIZE = 3 * COUNT_SIZE; // 3 counts
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static const int LO_FREQUENCY = 1020; // AIM 1-1-7 (f) specified in Hz
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static const int HI_FREQUENCY = 1350; // AIM 1-1-7 (f) specified in Hz
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// manages everything we need to know for an individual sound sample
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class FGMorse {
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private:
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unsigned char hi_dit[ DIT_SIZE ] ;
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unsigned char lo_dit[ DIT_SIZE ] ;
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unsigned char hi_dah[ DAH_SIZE ] ;
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unsigned char lo_dah[ DAH_SIZE ] ;
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unsigned char space[ SPACE_SIZE ] ;
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unsigned char cust_dit[ DIT_SIZE ] ;
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unsigned char cust_dah[ DAH_SIZE ] ;
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bool cust_init( const int freq );
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public:
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FGMorse();
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~FGMorse();
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// allocate and initialize sound samples
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bool init();
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// make a SimpleSound morse code transmission for the specified string
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SGSoundSample *make_ident( const string& id,
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const int freq = LO_FREQUENCY );
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};
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/**
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* \relates FGMorse
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* Make a tone of specified freq and total_len with trans_len ramp in
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* and out and only the first len bytes with sound, the rest with
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* silence.
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* @param buf unsigned char pointer to sound buffer
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* @param freq desired frequency of tone
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* @param len length of tone within sound
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* @param total_len total length of sound (anything more than len is padded
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* with silence.
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* @param trans_len length of ramp up and ramp down to avoid audio "pop"
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*/
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void make_tone( unsigned char *buf, int freq,
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int len, int total_len, int trans_len );
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#endif // _MORSE_HXX
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