Radio: Add option to change volume of transmission/reception

src/radio/main.c

@@ -63,6 +63,7 @@ static double bandwidth = 0.0;
 static double deviation = 75000.0;
 static double modulation_index = 1.0;
 static double time_constant_us = 50.0;
+static double volume = 1.0;
 static int stereo = 0;
 static int rds = 0;
 static int rds2 = 0;
@@ -138,6 +139,8 @@ void print_help(const char *arg0)
 	printf("        modulation. Give 0 to disbale. (default = %.0f uS)\n", time_constant_us);
 	printf("        VHF broadcast 50 uS in Europe and 75 uS in the United States.\n");
 	printf("        Other radio FM should use 530 uS, to cover complete speech spectrum.\n");
+	printf(" -V --volume %.3f\n", volume);
+	printf("        Change volume of radio side. (Gains transmission, dampens reception)\n");
 	printf(" -S --stereo\n");
 	printf("        Enables stereo carrier for frequency modulated UHF broadcast.\n");
 	printf("        It uses the 'Pilot-tone' system.\n");
@@ -169,6 +172,7 @@ static void add_options(void)
 	option_add('D', "deviation", 1);
 	option_add('I', "modulation-index", 1);
 	option_add('E', "emphasis", 1);
+	option_add('V', "volume", 1);
 	option_add('S', "stereo", 0);
 	option_add(OPT_FAST_MATH, "fast-math", 0);
 	option_add(OPT_LIMESDR, "limesdr", 0);
@@ -238,6 +242,9 @@ static int handle_options(int short_option, int argi, char **argv)
 	case 'E':
 		time_constant_us = atof(argv[argi]);
 		break;
+	case 'V':
+		volume = atof(argv[argi]);
+		break;
 	case 'S':
 		stereo = 1;
 		break;
@@ -348,7 +355,7 @@ int main(int argc, char *argv[])
 	/* now we have latency and sample rate */
 	latspl = samplerate * latency / 1000;
 
-	rc = radio_init(&radio, latspl, samplerate, tx_wave_file, rx_wave_file, (tx) ? tx_audiodev : NULL, (rx) ? rx_audiodev : NULL, modulation, bandwidth, deviation, modulation_index, time_constant_us, stereo, rds, rds2);
+	rc = radio_init(&radio, latspl, samplerate, tx_wave_file, rx_wave_file, (tx) ? tx_audiodev : NULL, (rx) ? rx_audiodev : NULL, modulation, bandwidth, deviation, modulation_index, time_constant_us, volume, stereo, rds, rds2);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to initialize radio with given options, exitting!\n");
 		exit(0);

src/radio/radio.c

@@ -36,7 +36,7 @@
 #define PILOT_FREQ	19000.0
 #define PILOT_BW	5.0
 
-int radio_init(radio_t *radio, int latspl, int samplerate, const char *tx_wave_file, const char *rx_wave_file, const char *tx_audiodev, const char *rx_audiodev, enum modulation modulation, double bandwidth, double deviation, double modulation_index, double time_constant_us, int stereo, int rds, int rds2)
+int radio_init(radio_t *radio, int latspl, int samplerate, const char *tx_wave_file, const char *rx_wave_file, const char *tx_audiodev, const char *rx_audiodev, enum modulation modulation, double bandwidth, double deviation, double modulation_index, double time_constant_us, double volume, int stereo, int rds, int rds2)
 {
 	int rc = -EINVAL;
 
@@ -44,6 +44,7 @@ int radio_init(radio_t *radio, int latspl, int samplerate, const char *tx_wave_f
 
 	memset(radio, 0, sizeof(*radio));
 	radio->latspl = latspl;
+	radio->volume = volume;
 	radio->stereo = stereo;
 	radio->rds = rds;
 	radio->rds2 = rds2;
@@ -457,6 +458,7 @@ int radio_tx(radio_t *radio, float *baseband, int signal_num)
 	switch (radio->tx_audio_mode) {
 	case AUDIO_MODE_WAVEFILE:
 		wave_read(&radio->wave_tx_play, audio_samples, audio_num);
+		
 		if (!radio->wave_tx_play.left) {
 			int rc;
 			int _samplerate = 0;
@@ -527,6 +529,16 @@ int radio_tx(radio_t *radio, float *baseband, int signal_num)
 	if (radio->stereo)
 		iir_process(&radio->tx_dc_removal[1], audio_samples[1], audio_num);
 
+	/* gain volume */
+	if (radio->volume != 1.0) {
+		for (i = 0; i < audio_num; i++)
+			audio_samples[0][i] *= radio->volume;
+		if (radio->stereo) {
+			for (i = 0; i < audio_num; i++)
+				audio_samples[1][i] *= radio->volume;
+		}
+	}
+
 	/* upsample */
 	signal_num = samplerate_upsample(&radio->tx_resampler[0], audio_samples[0], audio_num, signal_samples[0]);
 	if (radio->stereo)
@@ -654,6 +666,16 @@ int radio_rx(radio_t *radio, float *baseband, int signal_num)
 	if (radio->stereo)
 		samplerate_downsample(&radio->rx_resampler[1], samples[1], signal_num);
 
+	/* dampen volume */
+	if (radio->volume != 1.0) {
+		for (i = 0; i < audio_num; i++)
+			samples[0][i] /= radio->volume;
+		if (radio->stereo) {
+			for (i = 0; i < audio_num; i++)
+				samples[1][i] /= radio->volume;
+		}
+	}
+
 	/* convert mono/stereo, (from differential signal) */
 	if (radio->stereo && radio->rx_audio_channels == 1) {
 		/* stereo to mono */

src/radio/radio.h

@@ -27,6 +27,7 @@ typedef struct radio {
 	enum modulation	modulation;		/* modulation type */
 	enum audio_mode	tx_audio_mode;		/* mode for audio source */
 	enum audio_mode	rx_audio_mode;		/* mode for audio sink */
+	double		volume;			/* volume change (gain/dampen) */
 	int		stereo;			/* use stere FM */
 	int		rds, rds2;		/* use RDS */
 	/* audio stage */
@@ -77,7 +78,7 @@ typedef struct radio {
 	sample_t	*carrier_buffer;
 } radio_t;
 
-int radio_init(radio_t *radio, int latspl, int samplerate, const char *tx_wave_file, const char *rx_wave_file, const char *tx_audiodev, const char *rx_audiodev, enum modulation modulation, double bandwidth, double deviation, double modulation_index, double time_constant, int stereo, int rds, int rds2);
+int radio_init(radio_t *radio, int latspl, int samplerate, const char *tx_wave_file, const char *rx_wave_file, const char *tx_audiodev, const char *rx_audiodev, enum modulation modulation, double bandwidth, double deviation, double modulation_index, double time_constant, double volume, int stereo, int rds, int rds2);
 void radio_exit(radio_t *radio);
 int radio_start(radio_t *radio);
 int radio_tx(radio_t *radio, float *baseband, int num);