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authorAndreas Eversberg <jolly@eversberg.eu>2017-11-15 18:45:56 +0100
committerAndreas Eversberg <jolly@eversberg.eu>2017-11-25 19:23:46 +0100
commitfd3a4d7ac2d0a3759067c08c67cfad406fbcfb3c (patch)
treeca0a5640df0777ddd7c38000ac5c0ac963e6d5ff /src/libdtmf/dtmf_encode.c
parent17b34fbae63f0ddebcb82e9714718c030e770300 (diff)
Restructure: Move dtmf from common code to 'libdtmf'
Diffstat (limited to 'src/libdtmf/dtmf_encode.c')
-rw-r--r--src/libdtmf/dtmf_encode.c123
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..6413954
--- /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 "../common/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));
+}
+