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authorAndreas Eversberg <jolly@eversberg.eu>2017-11-20 19:51:24 +0100
committerAndreas Eversberg <jolly@eversberg.eu>2017-12-03 08:46:05 +0100
commit9e75e64787e10556bf2075f241e23e41d8fd2b4c (patch)
tree5b8da262760a0ef4617cd3ee070f82db88c304cc
parent44247ffb536ef25c1fc8c49c75b501d6f1808c52 (diff)
Add DTMF decoder to libdtmf
Note: This decoder has no user yet.
-rw-r--r--.gitignore1
-rw-r--r--src/libdtmf/Makefile.am3
-rw-r--r--src/libdtmf/dtmf_decode.c259
-rw-r--r--src/libdtmf/dtmf_decode.h35
-rw-r--r--src/test/Makefile.am10
-rw-r--r--src/test/test_dtmf.c114
6 files changed, 421 insertions, 1 deletions
diff --git a/.gitignore b/.gitignore
index 494a229..359c9e0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -61,6 +61,7 @@ src/test/test_filter
src/test/test_sendevolumenregler
src/test/test_compandor
src/test/test_emphasis
+src/test/test_dtmf
src/test/test_dms
src/test/test_sms
src/test/test_performance
diff --git a/src/libdtmf/Makefile.am b/src/libdtmf/Makefile.am
index a44d4f6..f1df569 100644
--- a/src/libdtmf/Makefile.am
+++ b/src/libdtmf/Makefile.am
@@ -3,4 +3,5 @@ AM_CPPFLAGS = -Wall -Wextra -g $(all_includes)
noinst_LIBRARIES = libdtmf.a
libdtmf_a_SOURCES = \
- dtmf_encode.c
+ dtmf_encode.c \
+ dtmf_decode.c
diff --git a/src/libdtmf/dtmf_decode.c b/src/libdtmf/dtmf_decode.c
new file mode 100644
index 0000000..c9ace1e
--- /dev/null
+++ b/src/libdtmf/dtmf_decode.c
@@ -0,0 +1,259 @@
+/* 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 <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <math.h>
+#include "../libsample/sample.h"
+#include "dtmf_decode.h"
+
+//#define DEBUG
+
+#define level2db(level) (20 * log10(level))
+#define db2level(db) pow(10, (double)db / 20.0)
+
+#define DTMF_LOW_1 697.0
+#define DTMF_LOW_2 770.0
+#define DTMF_LOW_3 852.0
+#define DTMF_LOW_4 941.0
+#define DTMF_HIGH_1 1209.0
+#define DTMF_HIGH_2 1336.0
+#define DTMF_HIGH_3 1477.0
+#define DTMF_HIGH_4 1633.0
+
+static const char dtmf_digit[] = " 123A456B789C*0#D";
+
+#ifdef DEBUG
+const char *_debug_amplitude(double level)
+{
+ static char text[42];
+
+ strcpy(text, " : ");
+ if (level > 1.0)
+ level = 1.0;
+ if (level < -1.0)
+ level = -1.0;
+ text[20 + (int)(level * 20)] = '*';
+
+ return text;
+}
+#endif
+
+int dtmf_decode_init(dtmf_dec_t *dtmf, void *priv, void (*recv_digit)(void *priv, char digit, dtmf_meas_t *meas), int samplerate, double max_amplitude, double min_amplitude)
+{
+ int rc;
+
+ memset(dtmf, 0, sizeof(*dtmf));
+ dtmf->priv = priv;
+ dtmf->recv_digit = recv_digit;
+ dtmf->samplerate = samplerate;
+ dtmf->freq_tollerance = 3.0;
+ dtmf->max_amplitude = max_amplitude;
+ dtmf->min_amplitude = min_amplitude;
+ dtmf->forward_twist = db2level(4.0);
+ dtmf->reverse_twist = db2level(8.0);
+ dtmf->time_detect = (int)(0.025 * (double)samplerate);
+ dtmf->time_meas = (int)(0.015 * (double)samplerate);
+ dtmf->time_pause = (int)(0.010 * (double)samplerate);
+
+ /* init fm demodulator */
+ rc = fm_demod_init(&dtmf->demod_low, (double)samplerate, (DTMF_LOW_1 + DTMF_LOW_4) / 2.0, DTMF_LOW_4 - DTMF_LOW_1);
+ if (rc < 0)
+ goto error;
+ rc = fm_demod_init(&dtmf->demod_high, (double)samplerate, (DTMF_HIGH_1 + DTMF_HIGH_4) / 2.0, DTMF_HIGH_4 - DTMF_HIGH_1);
+ if (rc < 0)
+ goto error;
+
+ /* use fourth order (2 iter) filter, since it is as fast as second order (1 iter) filter */
+ iir_lowpass_init(&dtmf->freq_lp[0], 100.0, samplerate, 2);
+ iir_lowpass_init(&dtmf->freq_lp[1], 100.0, samplerate, 2);
+
+ return 0;
+
+error:
+ dtmf_decode_exit(dtmf);
+ return rc;
+}
+
+void dtmf_decode_exit(dtmf_dec_t *dtmf)
+{
+ fm_demod_exit(&dtmf->demod_low);
+ fm_demod_exit(&dtmf->demod_high);
+}
+
+void dtmf_decode_filter(dtmf_dec_t *dtmf, sample_t *samples, int length, sample_t *frequency_low, sample_t *frequency_high, sample_t *amplitude_low, sample_t *amplitude_high)
+{
+ sample_t I_low[length], Q_low[length];
+ sample_t I_high[length], Q_high[length];
+ int i;
+
+ fm_demodulate_real(&dtmf->demod_low, frequency_low, length, samples, I_low, Q_low);
+ fm_demodulate_real(&dtmf->demod_high, frequency_high, length, samples, I_high, Q_high);
+ /* peak amplitude is the length of I/Q vector
+ * since we filter out the unwanted modulation product, the vector is only half of length */
+ for (i = 0; i < length; i++) {
+ amplitude_low[i] = sqrt(I_low[i] * I_low[i] + Q_low[i] * Q_low[i]) * 2.0;
+ amplitude_high[i] = sqrt(I_high[i] * I_high[i] + Q_high[i] * Q_high[i]) * 2.0;
+ }
+ iir_process(&dtmf->freq_lp[0], frequency_low, length);
+ iir_process(&dtmf->freq_lp[1], frequency_high, length);
+}
+void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
+{
+ sample_t frequency_low[length], amplitude_low[length];
+ sample_t frequency_high[length], amplitude_high[length];
+ double tollerance, min_amplitude, max_amplitude, forward_twist, reverse_twist, f1, f2;
+ int time_detect, time_meas, time_pause;
+ int low = 0, high = 0;
+ char detected, digit;
+ int count;
+ int aplitude_ok, twist_ok;
+ int i;
+
+ tollerance = dtmf->freq_tollerance;
+ min_amplitude = dtmf->min_amplitude;
+ max_amplitude = dtmf->max_amplitude;
+ forward_twist = dtmf->forward_twist;
+ reverse_twist = dtmf->reverse_twist;
+ time_detect = dtmf->time_detect;
+ time_meas = dtmf->time_meas;
+ time_pause = dtmf->time_pause;
+ detected = dtmf->detected;
+ count = dtmf->count;
+
+ /* FM/AM demod */
+ dtmf_decode_filter(dtmf, samples, length, frequency_low, frequency_high, amplitude_low, amplitude_high);
+
+ for (i = 0; i < length; i++) {
+#ifdef DEBUG
+ printf("%s %.5f\n", _debug_amplitude(samples[i]/2.0), samples[i]/2.0);
+#endif
+ /* get frequency of low frequencies, correct amplitude drop at cutoff point */
+ f1 = frequency_low[i] + (DTMF_LOW_1 + DTMF_LOW_4) / 2.0;
+ if (f1 >= DTMF_LOW_1 - tollerance && f1 <= DTMF_LOW_1 + tollerance) {
+ /* cutoff point */
+ amplitude_low[i] /= 0.7071;
+ low = 1;
+ f1 -= DTMF_LOW_1;
+ } else
+ if (f1 >= DTMF_LOW_2 - tollerance && f1 <= DTMF_LOW_2 + tollerance) {
+ amplitude_low[i] /= 1.0734;
+ low = 2;
+ f1 -= DTMF_LOW_2;
+ } else
+ if (f1 >= DTMF_LOW_3 - tollerance && f1 <= DTMF_LOW_3 + tollerance) {
+ amplitude_low[i] /= 1.0389;
+ low = 3;
+ f1 -= DTMF_LOW_3;
+ } else
+ if (f1 >= DTMF_LOW_4 - tollerance && f1 <= DTMF_LOW_4 + tollerance) {
+ /* cutoff point */
+ amplitude_low[i] /= 0.7071;
+ low = 4;
+ f1 -= DTMF_LOW_4;
+ } else
+ low = 0;
+ /* get frequency of high frequencies, correct amplitude drop at cutoff point */
+ f2 = frequency_high[i] + (DTMF_HIGH_1 + DTMF_HIGH_4) / 2.0;
+ if (f2 >= DTMF_HIGH_1 - tollerance && f2 <= DTMF_HIGH_1 + tollerance) {
+ /* cutoff point */
+ amplitude_high[i] /= 0.7071;
+ high = 1;
+ f2 -= DTMF_HIGH_1;
+ } else
+ if (f2 >= DTMF_HIGH_2 - tollerance && f2 <= DTMF_HIGH_2 + tollerance) {
+ amplitude_high[i] /= 1.0731;
+ high = 2;
+ f2 -= DTMF_HIGH_2;
+ } else
+ if (f2 >= DTMF_HIGH_3 - tollerance && f2 <= DTMF_HIGH_3 + tollerance) {
+ amplitude_high[i] /= 1.0372;
+ high = 3;
+ f2 -= DTMF_HIGH_3;
+ } else
+ if (f2 >= DTMF_HIGH_4 - tollerance && f2 <= DTMF_HIGH_4 + tollerance) {
+ /* cutoff point */
+ amplitude_high[i] /= 0.7071;
+ high = 4;
+ f2 -= DTMF_HIGH_4;
+ } else
+ high = 0;
+ digit = 0;
+ aplitude_ok = 0;
+ twist_ok = 0;
+ if (low && high) {
+ digit = dtmf_digit[low*4+high];
+ /* check for limits */
+ if (amplitude_low[i] <= max_amplitude && amplitude_low[i] >= min_amplitude && amplitude_high[i] <= max_amplitude && amplitude_high[i] >= min_amplitude) {
+ aplitude_ok = 1;
+#ifdef DEBUG
+ printf("%.5f %.5f %.1f\n", amplitude_low[i], amplitude_high[i], level2db(amplitude_high[i] / amplitude_low[i]));
+#endif
+ if (amplitude_high[i] / amplitude_low[i] <= forward_twist && amplitude_low[i] / amplitude_high[i] <= reverse_twist)
+ twist_ok = 1;
+ }
+ }
+
+ if (!detected) {
+ if (digit && aplitude_ok && twist_ok) {
+ if (count == 0) {
+ memset(&dtmf->meas, 0, sizeof(dtmf->meas));
+ }
+ if (count >= time_meas) {
+ dtmf->meas.frequency_low += f1;
+ dtmf->meas.frequency_high += f2;
+ dtmf->meas.amplitude_low += amplitude_low[i];
+ dtmf->meas.amplitude_high += amplitude_high[i];
+ dtmf->meas.count++;
+ }
+ count++;
+ if (count >= time_detect) {
+ detected = digit;
+ dtmf->meas.frequency_low /= dtmf->meas.count;
+ dtmf->meas.frequency_high /= dtmf->meas.count;
+ dtmf->meas.amplitude_low /= dtmf->meas.count;
+ dtmf->meas.amplitude_high /= dtmf->meas.count;
+ dtmf->meas.count = 1;
+ dtmf->recv_digit(dtmf->priv, digit, &dtmf->meas);
+ }
+ } else
+ count = 0;
+ } else {
+ if (!digit || digit != detected || !aplitude_ok || !twist_ok) {
+ count++;
+ if (count >= time_pause) {
+ detected = 0;
+#ifdef DEBUG
+ printf("lost!\n");
+#endif
+ }
+ } else
+ count = 0;
+ }
+#ifdef DEBUG
+ if (digit)
+ printf("DTMF tone='%c' diff frequency=%.1f %.1f amplitude=%.1f %.1f dB (%s) twist=%.1f dB (%s)\n", digit, f1, f2, level2db(amplitude_low[i]), level2db(amplitude_high[i]), (aplitude_ok) ? "OK" : "nok", level2db(amplitude_high[i] / amplitude_low[i]), (twist_ok) ? "OK" : "nok");
+#endif
+
+ dtmf->detected = detected;
+ dtmf->count = count;
+ }
+}
+
diff --git a/src/libdtmf/dtmf_decode.h b/src/libdtmf/dtmf_decode.h
new file mode 100644
index 0000000..4aa6546
--- /dev/null
+++ b/src/libdtmf/dtmf_decode.h
@@ -0,0 +1,35 @@
+#include "../libfm/fm.h"
+
+typedef struct ftmf_meas {
+ double frequency_low;
+ double frequency_high;
+ double amplitude_low;
+ double amplitude_high;
+ int count;
+} dtmf_meas_t;
+
+typedef struct dtmf_dec {
+ void *priv;
+ void (*recv_digit)(void *priv, char digit, dtmf_meas_t *meas);
+ int samplerate; /* samplerate */
+ double freq_tollerance; /* +- limit of frequency deviation to allow */
+ double min_amplitude; /* minimum amplitude relative to 0 dBm */
+ double max_amplitude; /* maximum amplitude relative to 0 dBm */
+ double forward_twist; /* how much do higher frequencies are louder than lower frequencies */
+ double reverse_twist; /* how much do lower frequencies are louder than higher frequencies */
+ int time_detect;
+ int time_meas;
+ int time_pause;
+ fm_demod_t demod_low; /* demodulator for low frequencies */
+ fm_demod_t demod_high; /* demodulator for high frequencies */
+ iir_filter_t freq_lp[2]; /* low pass to filter the frequency result */
+ char detected; /* currently detected DTMF digit or 0 for no detection */
+ int count; /* counter to count detection or loss (pause) of signal */
+ dtmf_meas_t meas; /* measurements */
+} dtmf_dec_t;
+
+int dtmf_decode_init(dtmf_dec_t *dtmf, void *priv, void (*recv_digit)(void *priv, char digit, dtmf_meas_t *meas), int samplerate, double max_amplitude, double min_amplitude);
+void dtmf_decode_exit(dtmf_dec_t *dtmf);
+void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length);
+void dtmf_decode_filter(dtmf_dec_t *dtmf, sample_t *samples, int length, sample_t *frequency_low, sample_t *frequency_high, sample_t *amplitude_low, sample_t *amplitude_high);
+
diff --git a/src/test/Makefile.am b/src/test/Makefile.am
index d15256c..cac2cfe 100644
--- a/src/test/Makefile.am
+++ b/src/test/Makefile.am
@@ -5,6 +5,7 @@ noinst_PROGRAMS = \
test_sendevolumenregler \
test_compandor \
test_emphasis \
+ test_dtmf \
test_dms \
test_sms \
test_performance \
@@ -80,6 +81,15 @@ test_emphasis_LDADD += \
$(SOAPY_LIBS)
endif
+test_dtmf_SOURCES = dummy.x test_dtmf.c
+
+test_dtmf_LDADD = \
+ $(COMMON_LA) \
+ $(top_builddir)/src/libdtmf/libdtmf.a \
+ $(top_builddir)/src/libfm/libfm.a \
+ $(top_builddir)/src/libfilter/libfilter.a \
+ -lm
+
test_dms_SOURCES = test_dms.c dummy.c
test_dms_LDADD = \
diff --git a/src/test/test_dtmf.c b/src/test/test_dtmf.c
new file mode 100644
index 0000000..8f56e5c
--- /dev/null
+++ b/src/test/test_dtmf.c
@@ -0,0 +1,114 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <math.h>
+#include <string.h>
+#include "../libdebug/debug.h"
+#include "../libsample/sample.h"
+#include "../libdtmf/dtmf_decode.h"
+#include "../libdtmf/dtmf_encode.h"
+
+#define level2db(level) (20 * log10(level))
+#define db2level(db) pow(10, (double)db / 20.0)
+
+#define SAMPLERATE 8000
+
+static double test_frequency[8] = { 697.0, 770.0, 852.0, 941.0, 1209.0, 1336.0, 1477.0, 1633.0 };
+static const char *test_digits = "*#0123456789ABCD";
+
+static sample_t samples[SAMPLERATE];
+
+/* generate samples with two tones */
+static void generate_test_sample(double frequency1, double frequency2, double amplitude1, double amplitude2)
+{
+ int i;
+ double value;
+
+ for (i = 0; i < SAMPLERATE; i++) {
+ value = cos(2.0 * M_PI * frequency1 / (double)SAMPLERATE * i) * amplitude1;
+ value += cos(2.0 * M_PI * frequency2 / (double)SAMPLERATE * i) * amplitude2;
+ samples[i] = value;
+ }
+}
+
+static void check_level(sample_t *samples, const char *desc, double target, int when1, int when2)
+{
+ int i;
+ double amplitude = 0.0, diff;
+
+ for (i = when1; i < when2; i++) {
+ amplitude += samples[i];
+ }
+ amplitude = amplitude / (when2 - when1);
+ diff = fabs(amplitude - target);
+ printf("%s: amplitude between %d and %d ms is %.4f / %.4f db (expected %.4f)\n", desc, when1 * 1000 / SAMPLERATE, when2 * 1000 / SAMPLERATE, amplitude, level2db(amplitude), level2db(target));
+ if (diff < -0.1 || diff > 0.1)
+ printf("**** ERROR: we expected a diff close to 0.0\n");
+ else
+ printf("OK!\n");
+}
+
+static char got_digit;
+
+static void recv_digit(void *inst, char digit, dtmf_meas_t *meas)
+{
+ printf("decoded digit '%c' frequency %.1f %.1f amplitude %.1f %.1f dB\n", digit, meas->frequency_low, meas->frequency_high, level2db(meas->amplitude_low), level2db(meas->amplitude_high));
+ got_digit = digit;
+}
+
+int main(void)
+{
+ dtmf_dec_t dtmf_dec;
+ dtmf_enc_t dtmf_enc;
+ sample_t frequency1[SAMPLERATE], frequency2[SAMPLERATE], amplitude1[SAMPLERATE], amplitude2[SAMPLERATE];
+ int f, i;
+ double target;
+
+ dtmf_decode_init(&dtmf_dec, NULL, recv_digit, SAMPLERATE, db2level(0), db2level(-30.0));
+
+ for (f = 0; f < 8; f++) {
+ printf("Testing filter with frequency %.0f Hz:\n", test_frequency[f]);
+ generate_test_sample(test_frequency[f], 0.0, 1.0, 0.0);
+
+ dtmf_decode_filter(&dtmf_dec, samples, SAMPLERATE, frequency1, frequency2, amplitude1, amplitude2);
+
+ if (f == 0 || f == 3)
+ target = sqrt(0.5);
+ else if (f == 1 || f == 2)
+ target = 1.0;
+ else
+ target = 0.0;
+ check_level(amplitude1, "frequency level", target, 900 * SAMPLERATE / 1000, 1000 * SAMPLERATE / 1000);
+ if (f == 4 || f == 7)
+ target = sqrt(0.5);
+ else if (f == 5 || f == 6)
+ target = 1.0;
+ else
+ target = 0.0;
+ check_level(amplitude2, "frequency level", target, 900 * SAMPLERATE / 1000, 1000 * SAMPLERATE / 1000);
+
+ puts("");
+ }
+
+ dtmf_encode_init(&dtmf_enc, SAMPLERATE, 1.0);
+
+ for (i = 0; i < 16; i++) {
+ printf("Testing digit '%c' encoding and decoding:\n", test_digits[i]);
+ memset(samples, 0, sizeof(samples[0]) * SAMPLERATE);
+ dtmf_encode_set_tone(&dtmf_enc, test_digits[i]);
+ dtmf_encode(&dtmf_enc, samples + SAMPLERATE / 10, SAMPLERATE / 20);
+ got_digit = 0;
+ dtmf_decode(&dtmf_dec, samples, SAMPLERATE);
+ if (got_digit == 0)
+ printf("**** ERROR: we expected to decode digit '%c', but nothing was decoded\n", test_digits[i]);
+ else if (got_digit != test_digits[i])
+ printf("**** ERROR: we expected to decode digit '%c', but we decoded digit '%c'\n", test_digits[i], got_digit);
+ else
+ printf("OK!\n");
+ puts("");
+ }
+
+ dtmf_decode_exit(&dtmf_dec);
+
+ return 0;
+}
+