Add DTMF decoder to libdtmf

Note: This decoder has no user yet.
pull/1/head
Andreas Eversberg 5 years ago
parent 44247ffb53
commit 9e75e64787
  1. 1
      .gitignore
  2. 3
      src/libdtmf/Makefile.am
  3. 259
      src/libdtmf/dtmf_decode.c
  4. 35
      src/libdtmf/dtmf_decode.h
  5. 10
      src/test/Makefile.am
  6. 114
      src/test/test_dtmf.c

1
.gitignore vendored

@ -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

@ -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

@ -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;
}
}

@ -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);

@ -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 = \

@ -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;
}
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