1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
/* spkmodem-recv.c - decode spkmodem signals */
/*
* Copyright (C) 2013 Vladimir 'phcoder' Serbinenko
*
* spkmodem-recv is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* spkmodem-recv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with spkmodem-recv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Compilation: gcc -o spkmodem-recv spkmodem-recv */
/* Usage: parecord --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv */
#define SAMPLES_PER_TRAME 240
#define FREQ_SEP_MIN 5
#define FREQ_SEP_MAX 15
#define FREQ_DATA_MIN 15
#define FREQ_DATA_THRESHOLD 25
#define FREQ_DATA_MAX 60
#define THRESHOLD 500
#define DEBUG 0
#define FLUSH_TIMEOUT 1
static signed short trame[2 * SAMPLES_PER_TRAME];
static signed short pulse[2 * SAMPLES_PER_TRAME];
static int ringpos = 0;
static int pos, f1, f2;
static int amplitude = 0;
static int lp = 0;
static void
read_sample (void)
{
amplitude -= abs (trame[ringpos]);
f1 -= pulse[ringpos];
f1 += pulse[(ringpos + SAMPLES_PER_TRAME) % (2 * SAMPLES_PER_TRAME)];
f2 -= pulse[(ringpos + SAMPLES_PER_TRAME) % (2 * SAMPLES_PER_TRAME)];
fread (trame + ringpos, 1, sizeof (trame[0]), stdin);
amplitude += abs (trame[ringpos]);
if (pos ? (trame[ringpos] < -THRESHOLD)
: (trame[ringpos] > +THRESHOLD))
{
pulse[ringpos] = 1;
pos = !pos;
f2++;
}
else
pulse[ringpos] = 0;
ringpos++;
ringpos %= 2 * SAMPLES_PER_TRAME;
lp++;
}
int
main ()
{
int bitn = 7;
char c = 0;
int i;
int llp = 0;
while (!feof (stdin))
{
if (lp > 3 * SAMPLES_PER_TRAME)
{
bitn = 7;
c = 0;
lp = 0;
llp++;
}
if (llp == FLUSH_TIMEOUT)
fflush (stdout);
if (f2 > FREQ_SEP_MIN && f2 < FREQ_SEP_MAX
&& f1 > FREQ_DATA_MIN && f1 < FREQ_DATA_MAX)
{
#if DEBUG
printf ("%d %d %d @%d\n", f1, f2, FREQ_DATA_THRESHOLD,
ftell (stdin) - sizeof (trame));
#endif
if (f1 < FREQ_DATA_THRESHOLD)
c |= (1 << bitn);
bitn--;
if (bitn < 0)
{
#if DEBUG
printf ("<%c, %x>", c, c);
#else
printf ("%c", c);
#endif
bitn = 7;
c = 0;
}
lp = 0;
llp = 0;
for (i = 0; i < SAMPLES_PER_TRAME; i++)
read_sample ();
continue;
}
read_sample ();
}
return 0;
}
|
