124 lines
3.5 KiB
C
124 lines
3.5 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 "sample.h"
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#include "dtmf.h"
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#define PI M_PI
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static double tx_peak_dtmf_low = 0.2818 / SPEECH_LEVEL; /* -11 dBm, relative to speech level */
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static double tx_peak_dtmf_high = 0.3548 / SPEECH_LEVEL;/* -9 dBm, relative to speech level */
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#define DTMF_DURATION 0.100 /* duration in seconds */
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static sample_t dsp_sine_dtmf_low[65536];
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static sample_t dsp_sine_dtmf_high[65536];
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void dtmf_init(dtmf_t *dtmf, int samplerate)
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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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dtmf->max = (int)((double)samplerate * DTMF_DURATION + 0.5);
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// FIXME: do this globally and not per instance */
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for (i = 0; i < 65536; i++) {
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dsp_sine_dtmf_low[i] = sin((double)i / 65536.0 * 2.0 * PI) * tx_peak_dtmf_low;
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dsp_sine_dtmf_high[i] = sin((double)i / 65536.0 * 2.0 * PI) * tx_peak_dtmf_high;
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}
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}
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/* set dtmf tone */
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void dtmf_set_tone(dtmf_t *dtmf, char tone)
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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;
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}
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dtmf->tone = tone;
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dtmf->pos = 0;
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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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}
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/* Generate audio stream from DTMF tone. Keep phase for next call of function. */
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void dtmf_tone(dtmf_t *dtmf, sample_t *samples, int length)
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{
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double *phaseshift, *phase;
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int i, pos, max;
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/* use silence, if no tone */
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if (!dtmf->tone) {
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memset(samples, 0, length * sizeof(*samples));
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return;
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}
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phaseshift = dtmf->phaseshift65536;
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phase = dtmf->phase65536;
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pos = dtmf->pos;
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max = dtmf->max;
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for (i = 0; i < length; i++) {
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*samples++ = dsp_sine_dtmf_low[(uint16_t)phase[0]]
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+ dsp_sine_dtmf_high[(uint16_t)phase[1]];
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phase[0] += phaseshift[0];
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if (phase[0] >= 65536)
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phase[0] -= 65536;
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phase[1] += phaseshift[1];
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if (phase[1] >= 65536)
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phase[1] -= 65536;
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/* tone ends */
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if (++pos == max) {
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dtmf->tone = 0;
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break;
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}
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}
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length -= i;
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dtmf->pos = pos;
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/* if tone ends, fill rest with silence */
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if (length)
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memset(samples, 0, length * sizeof(*samples));
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}
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