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Diffstat (limited to 'src/libdtmf/dtmf_encode.c')
| -rw-r--r-- | src/libdtmf/dtmf_encode.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/src/libdtmf/dtmf_encode.c b/src/libdtmf/dtmf_encode.c new file mode 100644 index 0000000..53bd1b6 --- /dev/null +++ b/src/libdtmf/dtmf_encode.c @@ -0,0 +1,123 @@ +/* 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)); +} + |