From b16b26d32627b18c714e4c6b27a80a14b7863dca Mon Sep 17 00:00:00 2001
From: Andreas Eversberg <jolly@eversberg.eu>
Date: Sun, 21 Apr 2024 14:47:06 +0200
Subject: [PATCH] Add parameter to DTMF decode to change frequency margin

There is no user for this yet.
---
 src/jolly/dsp.c           | 2 +-
 src/libdtmf/dtmf_decode.c | 6 +++---
 src/libdtmf/dtmf_decode.h | 6 ++++--
 src/test/test_dtmf.c      | 3 ++-
 4 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/jolly/dsp.c b/src/jolly/dsp.c
index 82d8012..baa3862 100644
--- a/src/jolly/dsp.c
+++ b/src/jolly/dsp.c
@@ -90,7 +90,7 @@ int dsp_init_sender(jolly_t *jolly, int nbfm, double squelch_db, int repeater)
 	/* init dtmf audio processing.
 	 * each frequency may be +6 dB deviation, which means a total deviation of +12 dB is allowed for detection.
 	 * also we allow a minimum of -30 dB for each tone. */
-	rc = dtmf_decode_init(&jolly->dtmf, jolly, jolly_receive_dtmf, 8000, db2level(6.0), db2level(-30.0));
+	rc = dtmf_decode_init(&jolly->dtmf, jolly, jolly_receive_dtmf, 8000, db2level(6.0), db2level(-30.0), DTMF_FREQ_MARGIN_PERCENT_DEFAULT);
 	if (rc < 0) {
 		LOGP(DDSP, LOGL_ERROR, "Failed to init DTMF decoder!\n");
 		goto error;
diff --git a/src/libdtmf/dtmf_decode.c b/src/libdtmf/dtmf_decode.c
index b1c30aa..97aec6a 100644
--- a/src/libdtmf/dtmf_decode.c
+++ b/src/libdtmf/dtmf_decode.c
@@ -41,7 +41,7 @@
 
 static const char dtmf_digit[] = "     123A456B789C*0#D";
 
-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 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, double freq_margin)
 {
 	int rc;
 
@@ -49,7 +49,7 @@ int dtmf_decode_init(dtmf_dec_t *dtmf, void *priv, void (*recv_digit)(void *priv
 	dtmf->priv = priv;
 	dtmf->recv_digit = recv_digit;
 	dtmf->samplerate = samplerate;
-	dtmf->freq_margin = 1.03; /* 1.8 .. 3.5 % */
+	dtmf->freq_margin = freq_margin;
 	dtmf->max_amplitude = max_amplitude;
 	dtmf->min_amplitude = min_amplitude;
 	dtmf->forward_twist = db2level(4.0);
@@ -118,7 +118,7 @@ void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length)
 	int amplitude_ok, twist_ok;
 	int i;
 
-	margin = dtmf->freq_margin;
+	margin = dtmf->freq_margin / 100.0 + 1.0;
 	min_amplitude = dtmf->min_amplitude;
 	max_amplitude = dtmf->max_amplitude;
 	forward_twist = dtmf->forward_twist;
diff --git a/src/libdtmf/dtmf_decode.h b/src/libdtmf/dtmf_decode.h
index 9c162fe..ea2ff8e 100644
--- a/src/libdtmf/dtmf_decode.h
+++ b/src/libdtmf/dtmf_decode.h
@@ -1,6 +1,8 @@
 #include "../libfm/fm.h"
 
-typedef struct ftmf_meas {
+#define DTMF_FREQ_MARGIN_PERCENT_DEFAULT	3	/* 1.8 .. 3.5 % */
+
+typedef struct dtmf_meas {
 	double		frequency_low;
 	double		frequency_high;
 	double		amplitude_low;
@@ -28,7 +30,7 @@ typedef struct dtmf_dec {
 	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);
+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, double freq_margin);
 void dtmf_decode_exit(dtmf_dec_t *dtmf);
 void dtmf_decode_reset(dtmf_dec_t *dtmf);
 void dtmf_decode(dtmf_dec_t *dtmf, sample_t *samples, int length);
diff --git a/src/test/test_dtmf.c b/src/test/test_dtmf.c
index 5b92634..e35ec8e 100644
--- a/src/test/test_dtmf.c
+++ b/src/test/test_dtmf.c
@@ -65,7 +65,8 @@ int main(void)
 
 	fm_init(0);
 
-	dtmf_decode_init(&dtmf_dec, NULL, recv_digit, SAMPLERATE, db2level(0), db2level(-30.0));
+	/* decoder uses a strict frequency offset of 0.1 percent. */
+	dtmf_decode_init(&dtmf_dec, NULL, recv_digit, SAMPLERATE, db2level(0), db2level(-30.0), 0.1);
 
 	for (f = 0; f < 8; f++) {
 		printf("Testing filter with frequency %.0f Hz:\n", test_frequency[f]);