1 // morse.hxx -- Morse code generation class
3 // Written by Curtis Olson, started March 2001.
5 // Copyright (C) 2001 Curtis L. Olson - http://www.flightgear.org/~curt
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
26 #include "soundgenerator.hxx"
27 #include <simgear/compiler.h>
28 #include <simgear/sound/soundmgr_openal.hxx>
31 // Quoting from http://www.kluft.com/~ikluft/ham/morse-intro.html by
32 // Ian Kluft KO6YQ <ikluft@kluft.com>
36 // What is the Standard for Measuring Morse Code Speed?
38 // [This was adapted from the Ham Radio FAQ which used to be posted on UseNet.]
40 // The word PARIS was chosen as the standard length for CW code
41 // speed. Each dit counts for one count, each dah counts for three
42 // counts, intra-character spacing is one count, inter-character
43 // spacing is three counts and inter-word spacing is seven counts, so
44 // the word PARIS is exactly 50 counts:
46 // PPPPPPPPPPPPPP AAAAAA RRRRRRRRRR IIIIII SSSSSSSSSS
47 // di da da di di da di da di di di di di di
48 // 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
50 // ^Intra-character ^Inter-character Inter-word^
52 // So 5 words-per-minute = 250 counts-per-minute / 50 counts-per-word
53 // or one count every 240 milliseconds. 13 words-per-minute is one
54 // count every ~92.3 milliseconds. This method of sending code is
55 // sometimes called "Slow Code", because at 5 wpm it sounds VERY SLOW.
57 // The "Farnsworth" method is accomplished by sending the dits and
58 // dahs and intra-character spacing at a higher speed, then increasing
59 // the inter-character and inter-word spacing to slow the sending
60 // speed down to the desired speed. For example, to send at 5 wpm with
61 // 13 wpm characters in Farnsworth method, the dits and
62 // intra-character spacing would be 92.3 milliseconds, the dah would
63 // be 276.9 milliseconds, the inter-character spacing would be 1.443
64 // seconds and inter-word spacing would be 3.367 seconds.
70 // My formulation is based dit = 1 count, dah = 3 counts, 1 count for
71 // intRA-character space, 3 counts for intER-character space. Target
72 // is 5 wpm which by the above means 1 count = 240 milliseconds.
74 // AIM 1-1-7 (f) states that the frequency of the tone should be 1020
75 // Hz for the VOR ident.
78 // manages everything we need to know for an individual sound sample
79 class FGMorse : public FGSoundGenerator {
83 unsigned char hi_dit[ DIT_SIZE ] ;
84 unsigned char lo_dit[ DIT_SIZE ] ;
85 unsigned char hi_dah[ DAH_SIZE ] ;
86 unsigned char lo_dah[ DAH_SIZE ] ;
87 unsigned char space[ SPACE_SIZE ] ;
89 unsigned char cust_dit[ DIT_SIZE ] ;
90 unsigned char cust_dah[ DAH_SIZE ] ;
92 static FGMorse * _instance;
94 bool cust_init( const int freq );
95 // allocate and initialize sound samples
99 static const int BYTES_PER_SECOND = 22050;
100 // static const int BEAT_LENGTH = 240; // milleseconds (5 wpm)
101 static const int BEAT_LENGTH = 92; // milleseconds (13 wpm)
102 static const int TRANSITION_BYTES = BYTES_PER_SECOND/200; // aka (int)(0.005 * BYTES_PER_SECOND);
103 static const int COUNT_SIZE = BYTES_PER_SECOND * BEAT_LENGTH / 1000;
104 static const int DIT_SIZE = 2 * COUNT_SIZE; // 2 counts
105 static const int DAH_SIZE = 4 * COUNT_SIZE; // 4 counts
106 static const int SPACE_SIZE = 3 * COUNT_SIZE; // 3 counts
107 static const int LO_FREQUENCY = 1020; // AIM 1-1-7 (f) specified in Hz
108 static const int HI_FREQUENCY = 1350; // AIM 1-1-7 (f) specified in Hz
114 static FGMorse * instance();
116 // make a SimpleSound morse code transmission for the specified string
117 SGSoundSample *make_ident( const std::string& id,
118 const int freq = LO_FREQUENCY );