131 lines
3.6 KiB
C
131 lines
3.6 KiB
C
/* DTMF coder
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*
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* (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdint.h>
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#include <string.h>
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#include <math.h>
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#include "../libsample/sample.h"
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#include "dtmf_encode.h"
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#define PI M_PI
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#define PEAK_DTMF_LOW 0.2818 /* -11 dBm, relative to 0 dBm level */
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#define PEAK_DTMF_HIGH 0.3548 /* -9 dBm, relative to 0 dBm level */
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void dtmf_encode_init(dtmf_enc_t *dtmf, int samplerate, double dBm_level)
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{
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int i;
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memset(dtmf, 0, sizeof(*dtmf));
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dtmf->samplerate = samplerate;
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for (i = 0; i < 65536; i++) {
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dtmf->sine_low[i] = sin((double)i / 65536.0 * 2.0 * PI) * PEAK_DTMF_LOW * dBm_level;
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dtmf->sine_high[i] = sin((double)i / 65536.0 * 2.0 * PI) * PEAK_DTMF_HIGH * dBm_level;
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}
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}
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/* set dtmf tone */
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int dtmf_encode_set_tone(dtmf_enc_t *dtmf, char tone, double on_duration, double off_duration)
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{
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double f1, f2;
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switch(tone) {
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case '1': f1 = 697.0; f2 = 1209.0; break;
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case '2': f1 = 697.0; f2 = 1336.0; break;
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case '3': f1 = 697.0; f2 = 1477.0; break;
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case'a':case 'A': f1 = 697.0; f2 = 1633.0; break;
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case '4': f1 = 770.0; f2 = 1209.0; break;
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case '5': f1 = 770.0; f2 = 1336.0; break;
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case '6': f1 = 770.0; f2 = 1477.0; break;
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case'b':case 'B': f1 = 770.0; f2 = 1633.0; break;
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case '7': f1 = 852.0; f2 = 1209.0; break;
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case '8': f1 = 852.0; f2 = 1336.0; break;
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case '9': f1 = 852.0; f2 = 1477.0; break;
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case'c':case 'C': f1 = 852.0; f2 = 1633.0; break;
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case '*': f1 = 941.0; f2 = 1209.0; break;
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case '0': f1 = 941.0; f2 = 1336.0; break;
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case '#': f1 = 941.0; f2 = 1477.0; break;
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case'd':case 'D': f1 = 941.0; f2 = 1633.0; break;
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default:
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dtmf->tone = 0;
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return -1;
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}
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dtmf->tone = tone;
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dtmf->pos = 0;
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dtmf->on = (int)((double)dtmf->samplerate * on_duration);
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dtmf->off = dtmf->on + (int)((double)dtmf->samplerate * off_duration);
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dtmf->phaseshift65536[0] = 65536.0 / ((double)dtmf->samplerate / f1);
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dtmf->phaseshift65536[1] = 65536.0 / ((double)dtmf->samplerate / f2);
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dtmf->phase65536[0] = 0.0;
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dtmf->phase65536[1] = 0.0;
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return 0;
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}
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/* Generate audio stream from DTMF tone.
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* Keep phase for next call of function.
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* Stop, if tone has finished and return only the samples that were used.
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*/
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int dtmf_encode(dtmf_enc_t *dtmf, sample_t *samples, int length)
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{
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double *phaseshift, *phase;
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sample_t *sine_low, *sine_high;
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int count = 0;
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int i;
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/* if no tone */
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if (!dtmf->tone)
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return 0;
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sine_low = dtmf->sine_low;
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sine_high = dtmf->sine_high;
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phaseshift = dtmf->phaseshift65536;
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phase = dtmf->phase65536;
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for (i = 0; i < length; i++) {
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*samples++ = sine_low[(uint16_t)phase[0]]
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+ sine_high[(uint16_t)phase[1]];
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phase[0] += phaseshift[0];
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if (phase[0] >= 65536.0)
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phase[0] -= 65536.0;
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phase[1] += phaseshift[1];
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if (phase[1] >= 65536.0)
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phase[1] -= 65536.0;
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dtmf->pos++;
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/* tone ends */
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if (dtmf->pos == dtmf->on) {
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phaseshift[0] = 0.0;
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phaseshift[1] = 0.0;
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phase[0] = 0.0;
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phase[1] = 0.0;
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}
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/* pause ends */
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if (dtmf->pos == dtmf->off) {
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dtmf->tone = 0;
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break;
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}
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}
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count += i;
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return count;
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}
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