DTMF: Correctly handle frequency marging (percent not hertz!)

This commit is contained in:
Andreas Eversberg 2020-10-11 18:03:12 +02:00
parent 51204b55a9
commit f37dfbe4ee
2 changed files with 20 additions and 20 deletions

View File

@ -64,7 +64,7 @@ int dtmf_decode_init(dtmf_dec_t *dtmf, void *priv, void (*recv_digit)(void *priv
dtmf->priv = priv; dtmf->priv = priv;
dtmf->recv_digit = recv_digit; dtmf->recv_digit = recv_digit;
dtmf->samplerate = samplerate; dtmf->samplerate = samplerate;
dtmf->freq_tollerance = 3.0; dtmf->freq_margin = 1.03; /* 1.8 .. 3.5 % */
dtmf->max_amplitude = max_amplitude; dtmf->max_amplitude = max_amplitude;
dtmf->min_amplitude = min_amplitude; dtmf->min_amplitude = min_amplitude;
dtmf->forward_twist = db2level(4.0); dtmf->forward_twist = db2level(4.0);
@ -119,15 +119,15 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
{ {
sample_t frequency_low[length], amplitude_low[length]; sample_t frequency_low[length], amplitude_low[length];
sample_t frequency_high[length], amplitude_high[length]; sample_t frequency_high[length], amplitude_high[length];
double tollerance, min_amplitude, max_amplitude, forward_twist, reverse_twist, f1, f2; double margin, min_amplitude, max_amplitude, forward_twist, reverse_twist, f1, f2;
int time_detect, time_meas, time_pause; int time_detect, time_meas, time_pause;
int low = 0, high = 0; int low = 0, high = 0;
char detected, digit; char detected, digit;
int count; int count;
int aplitude_ok, twist_ok; int amplitude_ok, twist_ok;
int i; int i;
tollerance = dtmf->freq_tollerance; margin = dtmf->freq_margin;
min_amplitude = dtmf->min_amplitude; min_amplitude = dtmf->min_amplitude;
max_amplitude = dtmf->max_amplitude; max_amplitude = dtmf->max_amplitude;
forward_twist = dtmf->forward_twist; forward_twist = dtmf->forward_twist;
@ -143,27 +143,27 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
for (i = 0; i < length; i++) { for (i = 0; i < length; i++) {
#ifdef DEBUG #ifdef DEBUG
printf("%s %.5f\n", _debug_amplitude(samples[i]/2.0), samples[i]/2.0); // printf("%s %.5f\n", _debug_amplitude(samples[i]/2.0), samples[i]/2.0);
#endif #endif
/* get frequency of low frequencies, correct amplitude drop at cutoff point */ /* get frequency of low frequencies, correct amplitude drop at cutoff point */
f1 = frequency_low[i] + (DTMF_LOW_1 + DTMF_LOW_4) / 2.0; f1 = frequency_low[i] + (DTMF_LOW_1 + DTMF_LOW_4) / 2.0;
if (f1 >= DTMF_LOW_1 - tollerance && f1 <= DTMF_LOW_1 + tollerance) { if (f1 >= DTMF_LOW_1 / margin && f1 <= DTMF_LOW_1 * margin) {
/* cutoff point */ /* cutoff point */
amplitude_low[i] /= 0.7071; amplitude_low[i] /= 0.7071;
low = 1; low = 1;
f1 -= DTMF_LOW_1; f1 -= DTMF_LOW_1;
} else } else
if (f1 >= DTMF_LOW_2 - tollerance && f1 <= DTMF_LOW_2 + tollerance) { if (f1 >= DTMF_LOW_2 / margin && f1 <= DTMF_LOW_2 * margin) {
amplitude_low[i] /= 1.0734; amplitude_low[i] /= 1.0734;
low = 2; low = 2;
f1 -= DTMF_LOW_2; f1 -= DTMF_LOW_2;
} else } else
if (f1 >= DTMF_LOW_3 - tollerance && f1 <= DTMF_LOW_3 + tollerance) { if (f1 >= DTMF_LOW_3 / margin && f1 <= DTMF_LOW_3 * margin) {
amplitude_low[i] /= 1.0389; amplitude_low[i] /= 1.0389;
low = 3; low = 3;
f1 -= DTMF_LOW_3; f1 -= DTMF_LOW_3;
} else } else
if (f1 >= DTMF_LOW_4 - tollerance && f1 <= DTMF_LOW_4 + tollerance) { if (f1 >= DTMF_LOW_4 / margin && f1 <= DTMF_LOW_4 * margin) {
/* cutoff point */ /* cutoff point */
amplitude_low[i] /= 0.7071; amplitude_low[i] /= 0.7071;
low = 4; low = 4;
@ -172,23 +172,23 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
low = 0; low = 0;
/* get frequency of high frequencies, correct amplitude drop at cutoff point */ /* get frequency of high frequencies, correct amplitude drop at cutoff point */
f2 = frequency_high[i] + (DTMF_HIGH_1 + DTMF_HIGH_4) / 2.0; f2 = frequency_high[i] + (DTMF_HIGH_1 + DTMF_HIGH_4) / 2.0;
if (f2 >= DTMF_HIGH_1 - tollerance && f2 <= DTMF_HIGH_1 + tollerance) { if (f2 >= DTMF_HIGH_1 / margin && f2 <= DTMF_HIGH_1 * margin) {
/* cutoff point */ /* cutoff point */
amplitude_high[i] /= 0.7071; amplitude_high[i] /= 0.7071;
high = 1; high = 1;
f2 -= DTMF_HIGH_1; f2 -= DTMF_HIGH_1;
} else } else
if (f2 >= DTMF_HIGH_2 - tollerance && f2 <= DTMF_HIGH_2 + tollerance) { if (f2 >= DTMF_HIGH_2 / margin && f2 <= DTMF_HIGH_2 * margin) {
amplitude_high[i] /= 1.0731; amplitude_high[i] /= 1.0731;
high = 2; high = 2;
f2 -= DTMF_HIGH_2; f2 -= DTMF_HIGH_2;
} else } else
if (f2 >= DTMF_HIGH_3 - tollerance && f2 <= DTMF_HIGH_3 + tollerance) { if (f2 >= DTMF_HIGH_3 / margin && f2 <= DTMF_HIGH_3 * margin) {
amplitude_high[i] /= 1.0372; amplitude_high[i] /= 1.0372;
high = 3; high = 3;
f2 -= DTMF_HIGH_3; f2 -= DTMF_HIGH_3;
} else } else
if (f2 >= DTMF_HIGH_4 - tollerance && f2 <= DTMF_HIGH_4 + tollerance) { if (f2 >= DTMF_HIGH_4 / margin && f2 <= DTMF_HIGH_4 * margin) {
/* cutoff point */ /* cutoff point */
amplitude_high[i] /= 0.7071; amplitude_high[i] /= 0.7071;
high = 4; high = 4;
@ -196,15 +196,15 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
} else } else
high = 0; high = 0;
digit = 0; digit = 0;
aplitude_ok = 0; amplitude_ok = 0;
twist_ok = 0; twist_ok = 0;
if (low && high) { if (low && high) {
digit = dtmf_digit[low*4+high]; digit = dtmf_digit[low*4+high];
/* check for limits */ /* check for limits */
if (amplitude_low[i] <= max_amplitude && amplitude_low[i] >= min_amplitude && amplitude_high[i] <= max_amplitude && amplitude_high[i] >= min_amplitude) { if (amplitude_low[i] <= max_amplitude && amplitude_low[i] >= min_amplitude && amplitude_high[i] <= max_amplitude && amplitude_high[i] >= min_amplitude) {
aplitude_ok = 1; amplitude_ok = 1;
#ifdef DEBUG #ifdef DEBUG
printf("%.5f %.5f %.1f\n", amplitude_low[i], amplitude_high[i], level2db(amplitude_high[i] / amplitude_low[i])); printf("%.1f %.1f (limits %.1f .. %.1f) %.1f\n", level2db(amplitude_low[i]), level2db(amplitude_high[i]), level2db(min_amplitude), level2db(max_amplitude), level2db(amplitude_high[i] / amplitude_low[i]));
#endif #endif
if (amplitude_high[i] / amplitude_low[i] <= forward_twist && amplitude_low[i] / amplitude_high[i] <= reverse_twist) if (amplitude_high[i] / amplitude_low[i] <= forward_twist && amplitude_low[i] / amplitude_high[i] <= reverse_twist)
twist_ok = 1; twist_ok = 1;
@ -212,7 +212,7 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
} }
if (!detected) { if (!detected) {
if (digit && aplitude_ok && twist_ok) { if (digit && amplitude_ok && twist_ok) {
if (count == 0) { if (count == 0) {
memset(&dtmf->meas, 0, sizeof(dtmf->meas)); memset(&dtmf->meas, 0, sizeof(dtmf->meas));
} }
@ -236,7 +236,7 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
} else } else
count = 0; count = 0;
} else { } else {
if (!digit || digit != detected || !aplitude_ok || !twist_ok) { if (!digit || digit != detected || !amplitude_ok || !twist_ok) {
count++; count++;
if (count >= time_pause) { if (count >= time_pause) {
detected = 0; detected = 0;
@ -249,7 +249,7 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
} }
#ifdef DEBUG #ifdef DEBUG
if (digit) 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"); 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]), (amplitude_ok) ? "OK" : "nok", level2db(amplitude_high[i] / amplitude_low[i]), (twist_ok) ? "OK" : "nok");
#endif #endif
dtmf->detected = detected; dtmf->detected = detected;

View File

@ -12,7 +12,7 @@ typedef struct dtmf_dec {
void *priv; void *priv;
void (*recv_digit)(void *priv, char digit, dtmf_meas_t *meas); void (*recv_digit)(void *priv, char digit, dtmf_meas_t *meas);
int samplerate; /* samplerate */ int samplerate; /* samplerate */
double freq_tollerance; /* +- limit of frequency deviation to allow */ double freq_margin; /* +- limit of frequency deviation (percent) valid tone*/
double min_amplitude; /* minimum amplitude relative to 0 dBm */ double min_amplitude; /* minimum amplitude relative to 0 dBm */
double max_amplitude; /* maximum 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 forward_twist; /* how much do higher frequencies are louder than lower frequencies */