arch/all-pc/boot/grub2-aros/util/spkmodem-recv.c

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