annotate ringing/genring.c @ 11:1d22e3f81531

ringing: generate FR-encoded and EFR-encoded "recordings" for GSM
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 07 Apr 2024 19:21:23 +0000
parents b875c8edd54f
children
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b875c8edd54f ringing: generate North American ringing signal
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1 /*
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2 * This program computes the waveform for the North American precise tone plan
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3 * ringing signal, specifically the 2 s long ON phase, and writes it into a
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4 * "robe" PCM16 file.
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5 */
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6
b875c8edd54f ringing: generate North American ringing signal
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7 #include <math.h>
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8 #include <stdio.h>
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9 #include <stdint.h>
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10 #include <stdlib.h>
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11
b875c8edd54f ringing: generate North American ringing signal
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12 #define FREQ_LOW (M_PI * 440.0 / 4000.0)
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13 #define FREQ_HIGH (M_PI * 480.0 / 4000.0)
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14
b875c8edd54f ringing: generate North American ringing signal
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15 #define AMPL_PEAK 2552.329f /* -19 dBm0 */
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16
b875c8edd54f ringing: generate North American ringing signal
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17 #define TOTAL_SAMPLES 16000
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18
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19 main(argc, argv)
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20 char **argv;
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21 {
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22 FILE *outf;
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23 float angle_low, angle_high;
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24 unsigned nsamp;
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25 int sample;
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26 unsigned sample_out;
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27
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28 if (argc != 2) {
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29 fprintf(stderr, "usage: %s outfile\n", argv[0]);
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30 exit(1);
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31 }
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32 outf = fopen(argv[1], "w");
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33 if (!outf) {
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34 perror(argv[1]);
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35 exit(1);
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36 }
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37 angle_low = 0;
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38 angle_high = 0;
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39 for (nsamp = 0; nsamp < TOTAL_SAMPLES; nsamp++) {
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40 sample = (sinf(angle_low) + sinf(angle_high)) * AMPL_PEAK;
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41 sample_out = sample & 0xFFFF;
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42 putc(sample_out >> 8, outf);
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43 putc(sample_out & 0xFF, outf);
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44 angle_low += FREQ_LOW;
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45 angle_high += FREQ_HIGH;
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46 }
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47 exit(0);
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48 }