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/* DTMF coder
*
* (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
* All Rights Reserved
*
* This program 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
#include <string.h>
#include <math.h>
#include "../libsample/sample.h"
#include "dtmf_encode.h"
#define PI M_PI
#define PEAK_DTMF_LOW 0.2818 /* -11 dBm, relative to 0 dBm level */
#define PEAK_DTMF_HIGH 0.3548 /* -9 dBm, relative to 0 dBm level */
#define DTMF_DURATION 0.100 /* duration in seconds */
static sample_t dsp_sine_dtmf_low[65536];
static sample_t dsp_sine_dtmf_high[65536];
void dtmf_encode_init(dtmf_enc_t *dtmf, int samplerate, double dBm_level)
{
int i;
memset(dtmf, 0, sizeof(*dtmf));
dtmf->samplerate = samplerate;
dtmf->max = (int)((double)samplerate * DTMF_DURATION + 0.5);
// FIXME: do this globally and not per instance */
for (i = 0; i < 65536; i++) {
dsp_sine_dtmf_low[i] = sin((double)i / 65536.0 * 2.0 * PI) * PEAK_DTMF_LOW * dBm_level;
dsp_sine_dtmf_high[i] = sin((double)i / 65536.0 * 2.0 * PI) * PEAK_DTMF_HIGH * dBm_level;
}
}
/* set dtmf tone */
void dtmf_encode_set_tone(dtmf_enc_t *dtmf, char tone)
{
double f1, f2;
switch(tone) {
case '1': f1 = 697.0; f2 = 1209.0; break;
case '2': f1 = 697.0; f2 = 1336.0; break;
case '3': f1 = 697.0; f2 = 1477.0; break;
case'a':case 'A': f1 = 697.0; f2 = 1633.0; break;
case '4': f1 = 770.0; f2 = 1209.0; break;
case '5': f1 = 770.0; f2 = 1336.0; break;
case '6': f1 = 770.0; f2 = 1477.0; break;
case'b':case 'B': f1 = 770.0; f2 = 1633.0; break;
case '7': f1 = 852.0; f2 = 1209.0; break;
case '8': f1 = 852.0; f2 = 1336.0; break;
case '9': f1 = 852.0; f2 = 1477.0; break;
case'c':case 'C': f1 = 852.0; f2 = 1633.0; break;
case '*': f1 = 941.0; f2 = 1209.0; break;
case '0': f1 = 941.0; f2 = 1336.0; break;
case '#': f1 = 941.0; f2 = 1477.0; break;
case'd':case 'D': f1 = 941.0; f2 = 1633.0; break;
default:
dtmf->tone = 0;
return;
}
dtmf->tone = tone;
dtmf->pos = 0;
dtmf->phaseshift65536[0] = 65536.0 / ((double)dtmf->samplerate / f1);
dtmf->phaseshift65536[1] = 65536.0 / ((double)dtmf->samplerate / f2);
}
/* Generate audio stream from DTMF tone. Keep phase for next call of function. */
void dtmf_encode(dtmf_enc_t *dtmf, sample_t *samples, int length)
{
double *phaseshift, *phase;
int i, pos, max;
/* use silence, if no tone */
if (!dtmf->tone) {
memset(samples, 0, length * sizeof(*samples));
return;
}
phaseshift = dtmf->phaseshift65536;
phase = dtmf->phase65536;
pos = dtmf->pos;
max = dtmf->max;
for (i = 0; i < length; i++) {
*samples++ = dsp_sine_dtmf_low[(uint16_t)phase[0]]
+ dsp_sine_dtmf_high[(uint16_t)phase[1]];
phase[0] += phaseshift[0];
if (phase[0] >= 65536)
phase[0] -= 65536;
phase[1] += phaseshift[1];
if (phase[1] >= 65536)
phase[1] -= 65536;
/* tone ends */
if (++pos == max) {
dtmf->tone = 0;
break;
}
}
length -= i;
dtmf->pos = pos;
/* if tone ends, fill rest with silence */
if (length)
memset(samples, 0, length * sizeof(*samples));
}
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