Rework on audio interface

Sound instance is now called audio instance and uses funcation pointers.
This gives a clean interface to be exchanged with other technologies,
linke SDR.

29 files changed, 231 insertions, 162 deletions

diff --git a/src/amps/amps.c b/src/amps/amps.c
index cfe5155..8f9b1ad 100644
--- a/src/amps/amps.c
+++ b/src/amps/amps.c
@@ -83,7 +83,7 @@ double amps_channel2freq(int channel, int uplink)
 	if (uplink)
 		freq -= 45.000;
 
-	return freq;
+	return freq * 1e6;
 }
 
 enum amps_chan_type amps_channel2type(int channel)
@@ -376,7 +376,7 @@ static amps_t *search_pc(void)
 static void amps_go_idle(amps_t *amps);
 
 /* Create transceiver instance and link to a list. */
-int amps_create(int channel, enum amps_chan_type chan_type, const char *sounddev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, amps_si *si, uint16_t sid, uint8_t sat, int polarity, int tolerant, int loopback)
+int amps_create(int channel, enum amps_chan_type chan_type, const char *audiodev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, amps_si *si, uint16_t sid, uint8_t sat, int polarity, int tolerant, int loopback)
 {
 	sender_t *sender;
 	amps_t *amps;
@@ -442,7 +442,7 @@ int amps_create(int channel, enum amps_chan_type chan_type, const char *sounddev
 	PDEBUG(DAMPS, DEBUG_DEBUG, "Creating 'AMPS' instance for channel = %d (sample rate %d).\n", channel, samplerate);
 
 	/* init general part of transceiver */
-	rc = sender_create(&amps->sender, channel, sounddev, samplerate, rx_gain, 0, 0, write_rx_wave, write_tx_wave, read_rx_wave, loopback, 0, PILOT_SIGNAL_NONE);
+	rc = sender_create(&amps->sender, channel, amps_channel2freq(channel, 0), amps_channel2freq(channel, 1), audiodev, samplerate, rx_gain, 0, 0, write_rx_wave, write_tx_wave, read_rx_wave, loopback, 0, PILOT_SIGNAL_NONE);
 	if (rc < 0) {
 		PDEBUG(DAMPS, DEBUG_ERROR, "Failed to init transceiver process!\n");
 		goto error;
@@ -919,7 +919,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 		int16_t up[(int)((double)count * amps->sender.srstate.factor + 0.5) + 10];
 		compress_audio(&amps->cstate, samples, count);
 		count = samplerate_upsample(&amps->sender.srstate, samples, count, up);
-		jitter_save(&amps->sender.audio, up, count);
+		jitter_save(&amps->sender.dejitter, up, count);
 	}
 }
 
diff --git a/src/amps/amps.h b/src/amps/amps.h
index b9f4ad2..4ff910b 100644
--- a/src/amps/amps.h
+++ b/src/amps/amps.h
@@ -163,7 +163,7 @@ const char *amps_min12number(uint32_t min1);
 void amps_number2min(const char *number, uint32_t *min1, uint16_t *min2);
 const char *amps_min2number(uint32_t min1, uint16_t min2);
 const char *amps_scm(uint8_t scm);
-int amps_create(int channel, enum amps_chan_type chan_type, const char *sounddev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, amps_si *si, uint16_t sid, uint8_t sat, int polarity, int tolerant, int loopback);
+int amps_create(int channel, enum amps_chan_type chan_type, const char *audiodev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, amps_si *si, uint16_t sid, uint8_t sat, int polarity, int tolerant, int loopback);
 void amps_destroy(sender_t *sender);
 void amps_rx_signaling_tone(amps_t *amps, int tone, double quality);
 void amps_rx_sat(amps_t *amps, int tone, double quality);
diff --git a/src/amps/dsp.c b/src/amps/dsp.c
index ae8b27b..776ec3b 100644
--- a/src/amps/dsp.c
+++ b/src/amps/dsp.c
@@ -481,7 +481,7 @@ again:
 		test_tone_encode(amps, samples, length);
 		break;
 	case DSP_MODE_AUDIO_RX_AUDIO_TX:
-		jitter_load(&amps->sender.audio, samples, length);
+		jitter_load(&amps->sender.dejitter, samples, length);
 		/* pre-emphasis */
 		if (amps->pre_emphasis)
 			pre_emphasis(&amps->estate, samples, length);
diff --git a/src/amps/frame.c b/src/amps/frame.c
index 6cf00bb..478739b 100644
--- a/src/amps/frame.c
+++ b/src/amps/frame.c
@@ -1701,7 +1701,7 @@ static const char *ie_chan(uint64_t value)
 	
 	if (value == 0)
 		return "No channel";
-	sprintf(string, "%" PRIu64 " = %.3f MHz", value, amps_channel2freq(value, 0));
+	sprintf(string, "%" PRIu64 " = %.3f MHz", value, amps_channel2freq(value, 0) / 1e6);
 	return string;
 }
 
diff --git a/src/amps/main.c b/src/amps/main.c
index d50b423..e97c5d4 100644
--- a/src/amps/main.c
+++ b/src/amps/main.c
@@ -259,9 +259,9 @@ int main(int argc, char *argv[])
 		print_help(argv[-skip_args]);
 		return 0;
 	}
-	if (num_kanal == 1 && num_sounddev == 0)
-		num_sounddev = 1; /* use defualt */
-	if (num_kanal != num_sounddev) {
+	if (num_kanal == 1 && num_audiodev == 0)
+		num_audiodev = 1; /* use defualt */
+	if (num_kanal != num_audiodev) {
 		fprintf(stderr, "You need to specify as many sound devices as you have channels.\n");
 		exit(0);
 	}
@@ -291,7 +291,7 @@ int main(int argc, char *argv[])
 	}
 	dsp_init();
 	init_frame();
-	rc = call_init(station_id, call_sounddev, samplerate, latency, 10, loopback);
+	rc = call_init(station_id, call_audiodev, samplerate, latency, 10, loopback);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create call control instance. Quitting!\n");
 		goto fail;
@@ -348,15 +348,15 @@ int main(int argc, char *argv[])
 		amps_si si;
 
 		init_sysinfo(&si, ms_power, ms_power, dcc, sid >> 1, regh, regr, pureg, pdreg, locaid, regincr, bis);
-		rc = amps_create(kanal[i], chan_type[i], sounddev[i], samplerate, rx_gain, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, &si, sid, scc, polarity, tolerant, loopback);
+		rc = amps_create(kanal[i], chan_type[i], audiodev[i], samplerate, rx_gain, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, &si, sid, scc, polarity, tolerant, loopback);
 		if (rc < 0) {
 			fprintf(stderr, "Failed to create \"Sender\" instance. Quitting!\n");
 			goto fail;
 		}
-		printf("Base station on channel %d ready (%s), please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], chan_type_long_name(chan_type[i]), amps_channel2freq(kanal[i], 0), amps_channel2freq(kanal[i], 1));
+		printf("Base station on channel %d ready (%s), please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], chan_type_long_name(chan_type[i]), amps_channel2freq(kanal[i], 0) / 1e6, amps_channel2freq(kanal[i], 1) / 1e6);
 	}
 
-	main_loop(&quit, latency, interval, NULL);
+	main_common(&quit, latency, interval, NULL);
 
 fail:
 	/* cleanup functions */
diff --git a/src/anetz/anetz.c b/src/anetz/anetz.c
index f8c13fd..23ec592 100644
--- a/src/anetz/anetz.c
+++ b/src/anetz/anetz.c
@@ -82,7 +82,7 @@ double anetz_kanal2freq(int kanal, int unterband)
 	if (unterband)
 		freq -= 4.500;
 
-	return freq;
+	return freq * 1e6;
 }
 
 /* Convert paging frequency number to to frequency. */
@@ -168,7 +168,7 @@ static void anetz_timeout(struct timer *timer);
 static void anetz_go_idle(anetz_t *anetz);
 
 /* Create transceiver instance and link to a list. */
-int anetz_create(int kanal, const char *sounddev, int samplerate, double rx_gain, int page_sequence, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume)
+int anetz_create(int kanal, const char *audiodev, int samplerate, double rx_gain, int page_sequence, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume)
 {
 	anetz_t *anetz;
 	int rc;
@@ -187,7 +187,7 @@ int anetz_create(int kanal, const char *sounddev, int samplerate, double rx_gain
 	PDEBUG(DANETZ, DEBUG_DEBUG, "Creating 'A-Netz' instance for 'Kanal' = %d (sample rate %d).\n", kanal, samplerate);
 
 	/* init general part of transceiver */
-	rc = sender_create(&anetz->sender, kanal, sounddev, samplerate, rx_gain, pre_emphasis, de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, loss_volume, PILOT_SIGNAL_NONE);
+	rc = sender_create(&anetz->sender, kanal, anetz_kanal2freq(kanal, 0), anetz_kanal2freq(kanal, 1), audiodev, samplerate, rx_gain, pre_emphasis, de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, loss_volume, PILOT_SIGNAL_NONE);
 	if (rc < 0) {
 		PDEBUG(DANETZ, DEBUG_ERROR, "Failed to init 'Sender' processing!\n");
 		goto error;
@@ -508,7 +508,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 	if (anetz->dsp_mode == DSP_MODE_AUDIO) {
 		int16_t up[(int)((double)count * anetz->sender.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&anetz->sender.srstate, samples, count, up);
-		jitter_save(&anetz->sender.audio, up, count);
+		jitter_save(&anetz->sender.dejitter, up, count);
 	}
 }
 
diff --git a/src/anetz/anetz.h b/src/anetz/anetz.h
index eacc616..ed5c4d5 100644
--- a/src/anetz/anetz.h
+++ b/src/anetz/anetz.h
@@ -45,7 +45,7 @@ typedef struct anetz {
 
 double anetz_kanal2freq(int kanal, int unterband);
 int anetz_init(void);
-int anetz_create(int kanal, const char *sounddev, int samplerate, double rx_gain, int page_sequence, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume);
+int anetz_create(int kanal, const char *audiodev, int samplerate, double rx_gain, int page_sequence, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume);
 void anetz_destroy(sender_t *sender);
 void anetz_loss_indication(anetz_t *anetz);
 void anetz_receive_tone(anetz_t *anetz, int bit);
diff --git a/src/anetz/dsp.c b/src/anetz/dsp.c
index b79b572..41888cd 100644
--- a/src/anetz/dsp.c
+++ b/src/anetz/dsp.c
@@ -371,7 +371,7 @@ void sender_send(sender_t *sender, int16_t *samples, int length)
 		memset(samples, 0, length * sizeof(*samples));
 		break;
 	case DSP_MODE_AUDIO:
-		jitter_load(&anetz->sender.audio, samples, length);
+		jitter_load(&anetz->sender.dejitter, samples, length);
 		break;
 	case DSP_MODE_TONE:
 		fsk_tone(anetz, samples, length);
diff --git a/src/anetz/main.c b/src/anetz/main.c
index 9b06859..d13d5be 100644
--- a/src/anetz/main.c
+++ b/src/anetz/main.c
@@ -143,9 +143,9 @@ int main(int argc, char *argv[])
 		print_help(argv[-skip_args]);
 		return 0;
 	}
-	if (num_kanal == 1 && num_sounddev == 0)
-		num_sounddev = 1; /* use defualt */
-	if (num_kanal != num_sounddev) {
+	if (num_kanal == 1 && num_audiodev == 0)
+		num_audiodev = 1; /* use defualt */
+	if (num_kanal != num_audiodev) {
 		fprintf(stderr, "You need to specify as many sound devices as you have channels.\n");
 		exit(0);
 	}
@@ -163,7 +163,7 @@ int main(int argc, char *argv[])
 	}
 	dsp_init();
 	anetz_init();
-	rc = call_init(station_id, call_sounddev, samplerate, latency, 5, loopback);
+	rc = call_init(station_id, call_audiodev, samplerate, latency, 5, loopback);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create call control instance. Quitting!\n");
 		goto fail;
@@ -171,15 +171,15 @@ int main(int argc, char *argv[])
 
 	/* create transceiver instance */
 	for (i = 0; i < num_kanal; i++) {
-		rc = anetz_create(kanal[i], sounddev[i], samplerate, rx_gain, page_sequence, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, lossdetect / 100.0);
+		rc = anetz_create(kanal[i], audiodev[i], samplerate, rx_gain, page_sequence, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, lossdetect / 100.0);
 		if (rc < 0) {
 			fprintf(stderr, "Failed to create \"Sender\" instance. Quitting!\n");
 			goto fail;
 		}
-		printf("Base station on channel %d ready, please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], anetz_kanal2freq(kanal[i], 0), anetz_kanal2freq(kanal[i], 1));
+		printf("Base station on channel %d ready, please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], anetz_kanal2freq(kanal[i], 0) / 1e6, anetz_kanal2freq(kanal[i], 1) / 1e6);
 	}
 
-	main_loop(&quit, latency, interval, NULL);
+	main_common(&quit, latency, interval, NULL);
 
 fail:
 	/* cleanup functions */
diff --git a/src/bnetz/bnetz.c b/src/bnetz/bnetz.c
index 9bb4b8b..6b8a6d9 100644
--- a/src/bnetz/bnetz.c
+++ b/src/bnetz/bnetz.c
@@ -106,7 +106,7 @@ double bnetz_kanal2freq(int kanal, int unterband)
 	if (unterband)
 		freq -= 4.600;
 
-	return freq;
+	return freq * 1e6;
 }
 
 /* switch pilot signal (tone or file) */
@@ -141,7 +141,7 @@ static void bnetz_timeout(struct timer *timer);
 static void bnetz_go_idle(bnetz_t *bnetz);
 
 /* Create transceiver instance and link to a list. */
-int bnetz_create(int kanal, const char *sounddev, int samplerate, double rx_gain, int gfs, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_factor, const char *pilot)
+int bnetz_create(int kanal, const char *audiodev, int samplerate, double rx_gain, int gfs, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_factor, const char *pilot)
 {
 	bnetz_t *bnetz;
 	enum pilot_signal pilot_signal = PILOT_SIGNAL_NONE;
@@ -202,7 +202,7 @@ error_pilot:
 	PDEBUG(DBNETZ, DEBUG_DEBUG, "Creating 'B-Netz' instance for 'Kanal' = %d 'Gruppenfreisignal' = %d (sample rate %d).\n", kanal, gfs, samplerate);
 
 	/* init general part of transceiver */
-	rc = sender_create(&bnetz->sender, kanal, sounddev, samplerate, rx_gain, pre_emphasis, de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, loss_factor, pilot_signal);
+	rc = sender_create(&bnetz->sender, kanal, bnetz_kanal2freq(kanal, 0), bnetz_kanal2freq(kanal, 1), audiodev, samplerate, rx_gain, pre_emphasis, de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, loss_factor, pilot_signal);
 	if (rc < 0) {
 		PDEBUG(DBNETZ, DEBUG_ERROR, "Failed to init transceiver process!\n");
 		goto error;
@@ -823,7 +823,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 	if (bnetz->dsp_mode == DSP_MODE_AUDIO) {
 		int16_t up[(int)((double)count * bnetz->sender.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&bnetz->sender.srstate, samples, count, up);
-		jitter_save(&bnetz->sender.audio, up, count);
+		jitter_save(&bnetz->sender.dejitter, up, count);
 	}
 }
 
diff --git a/src/bnetz/bnetz.h b/src/bnetz/bnetz.h
index 444a5a2..10f5a6d 100644
--- a/src/bnetz/bnetz.h
+++ b/src/bnetz/bnetz.h
@@ -100,7 +100,7 @@ typedef struct bnetz {
 
 double bnetz_kanal2freq(int kanal, int unterband);
 int bnetz_init(void);
-int bnetz_create(int kanal, const char *sounddev, int samplerate, double rx_gain, int gfs, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_factor, const char *pilot);
+int bnetz_create(int kanal, const char *audiodev, int samplerate, double rx_gain, int gfs, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_factor, const char *pilot);
 void bnetz_destroy(sender_t *sender);
 void bnetz_loss_indication(bnetz_t *bnetz);
 void bnetz_receive_tone(bnetz_t *bnetz, int bit);
diff --git a/src/bnetz/dsp.c b/src/bnetz/dsp.c
index d91780f..2e2a7f1 100644
--- a/src/bnetz/dsp.c
+++ b/src/bnetz/dsp.c
@@ -388,7 +388,7 @@ again:
 		memset(samples, 0, length * sizeof(*samples));
 		break;
 	case DSP_MODE_AUDIO:
-		jitter_load(&bnetz->sender.audio, samples, length);
+		jitter_load(&bnetz->sender.dejitter, samples, length);
 		break;
 	case DSP_MODE_0:
 		fsk_tone(bnetz, samples, length, 0);
diff --git a/src/bnetz/main.c b/src/bnetz/main.c
index 6f5a73b..7322ca3 100644
--- a/src/bnetz/main.c
+++ b/src/bnetz/main.c
@@ -153,9 +153,9 @@ int main(int argc, char *argv[])
 		print_help(argv[-skip_args]);
 		return 0;
 	}
-	if (num_kanal == 1 && num_sounddev == 0)
-		num_sounddev = 1; /* use defualt */
-	if (num_kanal != num_sounddev) {
+	if (num_kanal == 1 && num_audiodev == 0)
+		num_audiodev = 1; /* use defualt */
+	if (num_kanal != num_audiodev) {
 		fprintf(stderr, "You need to specify as many sound devices as you have channels.\n");
 		exit(0);
 	}
@@ -174,12 +174,12 @@ int main(int argc, char *argv[])
 		rc = mncc_init("/tmp/bsc_mncc");
 		if (rc < 0) {
 			fprintf(stderr, "Failed to setup MNCC socket. Quitting!\n");
-			return -1;
+			goto fail;
 		}
 	}
 	dsp_init();
 	bnetz_init();
-	rc = call_init(station_id, call_sounddev, samplerate, latency, 5, loopback);
+	rc = call_init(station_id, call_audiodev, samplerate, latency, 5, loopback);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create call control instance. Quitting!\n");
 		goto fail;
@@ -187,16 +187,16 @@ int main(int argc, char *argv[])
 
 	/* create transceiver instance */
 	for (i = 0; i < num_kanal; i++) {
-		rc = bnetz_create(kanal[i], sounddev[i], samplerate, rx_gain, gfs, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, (double)lossdetect / 100.0, pilot[i]);
+		rc = bnetz_create(kanal[i], audiodev[i], samplerate, rx_gain, gfs, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, (double)lossdetect / 100.0, pilot[i]);
 		if (rc < 0) {
 			fprintf(stderr, "Failed to create \"Sender\" instance. Quitting!\n");
 			goto fail;
 		}
-		printf("Base station for channel %d ready, please tune transmitter to %.3f MHz and receiver " "to %.3f MHz.\n", kanal[i], bnetz_kanal2freq(kanal[i], 0), bnetz_kanal2freq(kanal[i], 1));
-		printf("To call phone, switch transmitter (using pilot signal) to %.3f MHz.\n", bnetz_kanal2freq(19, 0));
+		printf("Base station for channel %d ready, please tune transmitter to %.3f MHz and receiver " "to %.3f MHz.\n", kanal[i], bnetz_kanal2freq(kanal[i], 0) / 1e6, bnetz_kanal2freq(kanal[i], 1) / 1e6);
+		printf("To call phone, switch transmitter (using pilot signal) to %.3f MHz.\n", bnetz_kanal2freq(19, 0) / 1e6);
 	}
 
-	main_loop(&quit, latency, interval, NULL);
+	main_common(&quit, latency, interval, NULL);
 
 fail:
 	/* cleanup functions */
diff --git a/src/cnetz/cnetz.c b/src/cnetz/cnetz.c
index ca0e941..f0a4ec5 100644
--- a/src/cnetz/cnetz.c
+++ b/src/cnetz/cnetz.c
@@ -161,7 +161,7 @@ double cnetz_kanal2freq(int kanal, int unterband)
 	if (unterband)
 		freq -= 10.0;
 
-	return freq;
+	return freq * 1e6;
 }
 
 const char *cnetz_state_name(enum cnetz_state state)
@@ -215,7 +215,7 @@ int cnetz_init(void)
 static void cnetz_go_idle(cnetz_t *cnetz);
 
 /* Create transceiver instance and link to a list. */
-int cnetz_create(int kanal, enum cnetz_chan_type chan_type, const char *sounddev, int samplerate, double rx_gain, int auth, int ms_power, int measure_speed, double clock_speed[2], int polarity, double noise, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback)
+int cnetz_create(int kanal, enum cnetz_chan_type chan_type, const char *audiodev, int samplerate, double rx_gain, int auth, int ms_power, int measure_speed, double clock_speed[2], int polarity, double noise, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback)
 {
 	sender_t *sender;
 	cnetz_t *cnetz;
@@ -258,7 +258,7 @@ int cnetz_create(int kanal, enum cnetz_chan_type chan_type, const char *sounddev
 
 	for (sender = sender_head; sender; sender = sender->next) {
 		cnetz = (cnetz_t *)sender;
-		if (!!strcmp(sender->sounddev, sounddev)) {
+		if (!!strcmp(sender->audiodev, audiodev)) {
 			PDEBUG(DCNETZ, DEBUG_NOTICE, "To be able to sync multiple channels, all channels must be on the same sound device!\n");
 			return -EINVAL;
 		}
@@ -274,7 +274,7 @@ int cnetz_create(int kanal, enum cnetz_chan_type chan_type, const char *sounddev
 
 	/* init general part of transceiver */
 	/* do not enable emphasis, since it is done by cnetz code, not by common sender code */
-	rc = sender_create(&cnetz->sender, kanal, sounddev, samplerate, rx_gain, 0, 0, write_rx_wave, write_tx_wave, read_rx_wave, loopback, 0, PILOT_SIGNAL_NONE);
+	rc = sender_create(&cnetz->sender, kanal, cnetz_kanal2freq(kanal, 0), cnetz_kanal2freq(kanal, 1), audiodev, samplerate, rx_gain, 0, 0, write_rx_wave, write_tx_wave, read_rx_wave, loopback, 0, PILOT_SIGNAL_NONE);
 	if (rc < 0) {
 		PDEBUG(DCNETZ, DEBUG_ERROR, "Failed to init transceiver process!\n");
 		goto error;
@@ -443,7 +443,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 
 	if (cnetz->dsp_mode == DSP_MODE_SPK_V) {
 		/* store as is, since we convert rate when processing FSK frames */
-		jitter_save(&cnetz->sender.audio, samples, count);
+		jitter_save(&cnetz->sender.dejitter, samples, count);
 	}
 }
 
diff --git a/src/cnetz/cnetz.h b/src/cnetz/cnetz.h
index 8691ac4..5897735 100644
--- a/src/cnetz/cnetz.h
+++ b/src/cnetz/cnetz.h
@@ -123,7 +123,7 @@ int cnetz_channel_by_short_name(const char *short_name);
 const char *chan_type_short_name(enum cnetz_chan_type chan_type);
 const char *chan_type_long_name(enum cnetz_chan_type chan_type);
 int cnetz_init(void);
-int cnetz_create(int kanal, enum cnetz_chan_type chan_type, const char *sounddev, int samplerate, double rx_gain, int auth, int ms_power, int measure_speed, double clock_speed[2], int polarity, double noise, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback);
+int cnetz_create(int kanal, enum cnetz_chan_type chan_type, const char *audiodev, int samplerate, double rx_gain, int auth, int ms_power, int measure_speed, double clock_speed[2], int polarity, double noise, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback);
 void cnetz_destroy(sender_t *sender);
 void cnetz_sync_frame(cnetz_t *cnetz, double sync, int ts);
 int cnetz_meldeaufruf(uint8_t futln_nat, uint8_t futln_fuvst, uint16_t futln_rest);
diff --git a/src/cnetz/dsp.c b/src/cnetz/dsp.c
index 0b78b92..a35e8c8 100644
--- a/src/cnetz/dsp.c
+++ b/src/cnetz/dsp.c
@@ -137,8 +137,8 @@ int dsp_init_sender(cnetz_t *cnetz, int measure_speed, double clock_speed[2], do
 	scrambler_setup(&cnetz->scrambler_rx, (double)cnetz->sender.samplerate / 1.1);
 
 	/* reinit jitter buffer for 8000 kHz */
-	jitter_destroy(&cnetz->sender.audio);
-	rc = jitter_create(&cnetz->sender.audio, 8000 / 5);
+	jitter_destroy(&cnetz->sender.dejitter);
+	rc = jitter_create(&cnetz->sender.dejitter, 8000 / 5);
 	if (rc < 0)
 		goto error;
 
@@ -702,7 +702,7 @@ again:
 	for (i = 0; i < copy; i++) {
 		if (*spl == -32768) {
 			/* marker found to insert new chunk of audio */
-			jitter_load(&cnetz->sender.audio, speech_buffer, 100);
+			jitter_load(&cnetz->sender.dejitter, speech_buffer, 100);
 			/* 1. compress dynamics */
 			compress_audio(&cnetz->cstate, speech_buffer, 100);
 			/* 2. upsample */
diff --git a/src/cnetz/main.c b/src/cnetz/main.c
index efe3148..ddb8216 100644
--- a/src/cnetz/main.c
+++ b/src/cnetz/main.c
@@ -217,9 +217,9 @@ int main(int argc, char *argv[])
 		printf("No channel (\"Kanal\") is specified, I suggest channel %d.\n\n", CNETZ_OGK_KANAL);
 		mandatory = 1;
 	}
-	if (num_kanal == 1 && num_sounddev == 0)
-		num_sounddev = 1; /* use defualt */
-	if (num_kanal != num_sounddev) {
+	if (num_kanal == 1 && num_audiodev == 0)
+		num_audiodev = 1; /* use defualt */
+	if (num_kanal != num_audiodev) {
 		fprintf(stderr, "You need to specify as many sound devices as you have channels.\n");
 		exit(0);
 	}
@@ -248,7 +248,7 @@ int main(int argc, char *argv[])
 		rc = mncc_init("/tmp/bsc_mncc");
 		if (rc < 0) {
 			fprintf(stderr, "Failed to setup MNCC socket. Quitting!\n");
-			return -1;
+			goto fail;
 		}
 	}
 	scrambler_init();
@@ -261,7 +261,7 @@ int main(int argc, char *argv[])
 	}
 	init_coding();
 	cnetz_init();
-	rc = call_init(station_id, call_sounddev, samplerate, latency, 7, loopback);
+	rc = call_init(station_id, call_audiodev, samplerate, latency, 7, loopback);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create call control instance. Quitting!\n");
 		goto fail;
@@ -302,15 +302,19 @@ int main(int argc, char *argv[])
 
 	/* create transceiver instance */
 	for (i = 0; i < num_kanal; i++) {
-		rc = cnetz_create(kanal[i], chan_type[i], sounddev[i], samplerate, rx_gain, auth, ms_power, (i == 0) ? measure_speed : 0, clock_speed, polarity, noise, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback);
+		rc = cnetz_create(kanal[i], chan_type[i], audiodev[i], samplerate, rx_gain, auth, ms_power, (i == 0) ? measure_speed : 0, clock_speed, polarity, noise, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback);
 		if (rc < 0) {
 			fprintf(stderr, "Failed to create \"Sender\" instance. Quitting!\n");
 			goto fail;
 		}
-		printf("Base station on channel %d ready, please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], cnetz_kanal2freq(kanal[i], 0), cnetz_kanal2freq(kanal[i], 1));
+		if ((kanal[i] & 1)) {
+			printf("Base station on channel %d ready, please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], cnetz_kanal2freq(kanal[i], 0) / 1e6, cnetz_kanal2freq(kanal[i], 1) / 1e6);
+		} else {
+			printf("Base station on channel %d ready, please tune transmitter to %.4f MHz and receiver to %.4f MHz.\n", kanal[i], cnetz_kanal2freq(kanal[i], 0) / 1e6, cnetz_kanal2freq(kanal[i], 1) / 1e6);
+		}
 	}
 
-	main_loop(&quit, latency, interval, NULL);
+	main_common(&quit, latency, interval, NULL);
 
 fail:
 	/* cleanup functions */
diff --git a/src/common/call.c b/src/common/call.c
index 62bfa89..7f8fae6 100644
--- a/src/common/call.c
+++ b/src/common/call.c
@@ -170,7 +170,7 @@ typedef struct call {
 	void *sound;		/* headphone interface */
 	int latspl;		/* sample latency at sound interface */
 	samplerate_t srstate;	/* patterns/announcement upsampling */
-	jitter_t audio;		/* headphone audio dejittering */
+	jitter_t dejitter;	/* headphone audio dejittering */
 	int audio_pos;		/* position when playing patterns */
 	int test_audio_pos;	/* position for test tone toward mobile */
 	int dial_digits;	/* number of digits to be dialed */
@@ -454,7 +454,7 @@ static void process_timeout(struct timer *timer)
 	}
 }
 
-int call_init(const char *station_id, const char *sounddev, int samplerate, int latency, int dial_digits, int loopback)
+int call_init(const char *station_id, const char *audiodev, int samplerate, int latency, int dial_digits, int loopback)
 {
 	int rc = 0;
 
@@ -469,11 +469,11 @@ int call_init(const char *station_id, const char *sounddev, int samplerate, int
 	call.dial_digits = dial_digits;
 	call.loopback = loopback;
 
-	if (!sounddev[0])
+	if (!audiodev[0])
 		return 0;
 
 	/* open sound device for call control */
-	call.sound = sound_open(sounddev, samplerate);
+	call.sound = sound_open(audiodev, NULL, NULL, 1, samplerate);
 	if (!call.sound) {
 		PDEBUG(DSENDER, DEBUG_ERROR, "No sound device!\n");
 
@@ -487,9 +487,9 @@ int call_init(const char *station_id, const char *sounddev, int samplerate, int
 		goto error;
 	}
 
-	rc = jitter_create(&call.audio, samplerate / 5);
+	rc = jitter_create(&call.dejitter, samplerate / 5);
 	if (rc < 0) {
-		PDEBUG(DSENDER, DEBUG_ERROR, "Failed to create and init audio buffer!\n");
+		PDEBUG(DSENDER, DEBUG_ERROR, "Failed to create and init dejitter buffer!\n");
 		goto error;
 	}
 
@@ -509,7 +509,7 @@ void call_cleanup(void)
 	if (call.sound)
 		sound_close(call.sound);
 
-	jitter_destroy(&call.audio);
+	jitter_destroy(&call.dejitter);
 
 	if (process_head) {
 		PDEBUG(DMNCC, DEBUG_ERROR, "Not all MNCC instances have been released!\n");
@@ -658,17 +658,17 @@ void process_call(int c)
 			get_call_patterns(samples, count, PATTERN_RINGBACK);
 			count = samplerate_upsample(&call.srstate, samples, count, up);
 			/* prevent click after hangup */
-			jitter_clear(&call.audio);
+			jitter_clear(&call.dejitter);
 			break;
 		case CALL_DISCONNECTED:
 			count = (int)((double)count / call.srstate.factor + 0.5);
 			get_call_patterns(samples, count, cause2pattern(call.disc_cause));
 			count = samplerate_upsample(&call.srstate, samples, count, up);
 			/* prevent click after hangup */
-			jitter_clear(&call.audio);
+			jitter_clear(&call.dejitter);
 			break;
 		default:
-			jitter_load(&call.audio, up, count);
+			jitter_load(&call.dejitter, up, count);
 		}
 		spl_list[0] = up;
 		rc = sound_write(call.sound, spl_list, count, 1);
@@ -691,7 +691,7 @@ void process_call(int c)
 		int16_t down[count]; /* more than enough */
 
 		if (call.loopback == 3)
-			jitter_save(&call.audio, samples, count);
+			jitter_save(&call.dejitter, samples, count);
 		count = samplerate_downsample(&call.srstate, samples, count, down);
 		call_rx_audio(call.callref, down, count);
 	}
@@ -922,7 +922,7 @@ void call_tx_audio(int callref, int16_t *samples, int count)
 	if (call.sound) {
 		int16_t up[(int)((double)count * call.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&call.srstate, samples, count, up);
-		jitter_save(&call.audio, up, count);
+		jitter_save(&call.dejitter, up, count);
 	} else
 	/* else, if no sound is used, send test tone to mobile */
 	if (call.state == CALL_CONNECT) {
diff --git a/src/common/call.h b/src/common/call.h
index 1f96fe7..996224f 100644
--- a/src/common/call.h
+++ b/src/common/call.h
@@ -9,7 +9,7 @@ enum number_type {
 	TYPE_INTERNATIONAL,
 };
 
-int call_init(const char *station_id, const char *sounddev, int samplerate, int latency, int dial_digits, int loopback);
+int call_init(const char *station_id, const char *audiodev, int samplerate, int latency, int dial_digits, int loopback);
 void call_cleanup(void);
 void process_call(int c);
 void clear_console_text(void);
diff --git a/src/common/main.h b/src/common/main.h
index c8d1180..3b680e4 100644
--- a/src/common/main.h
+++ b/src/common/main.h
@@ -1,9 +1,9 @@
 
 extern int num_kanal;
 extern int kanal[];
-extern int num_sounddev;
-extern const char *sounddev[];
-extern const char *call_sounddev;
+extern int num_audiodev;
+extern const char *audiodev[];
+extern const char *call_audiodev;
 extern int samplerate;
 extern int interval;
 extern int latency;
@@ -39,7 +39,7 @@ void opt_switch_common(int c, char *arg0, int *skip_args);
 extern int quit;
 void sighandler(int sigset);
 
-void main_loop(int *quit, int latency, int interval, void (*myhandler)(void));
+void main_common(int *quit, int latency, int interval, void (*myhandler)(void));
 
 void dump_info(void);
 
diff --git a/src/common/main_common.c b/src/common/main_common.c
index 4c731f6..11fa358 100644
--- a/src/common/main_common.c
+++ b/src/common/main_common.c
@@ -36,9 +36,9 @@
 /* common settings */
 int num_kanal = 0;
 int kanal[MAX_SENDER];
-int num_sounddev = 0;
-const char *sounddev[MAX_SENDER] = { "hw:0,0" };
-const char *call_sounddev = "";
+int num_audiodev = 0;
+const char *audiodev[MAX_SENDER] = { "hw:0,0" };
+const char *call_audiodev = "";
 int samplerate = 48000;
 int interval = 1;
 int latency = 50;
@@ -95,7 +95,7 @@ void print_help_common(const char *arg0, const char *ext_usage)
 	printf(" -m --mncc-sock\n");
 	printf("        Disable built-in call contol and offer socket (to LCR)\n");
 	printf(" -c --call-device hw:<card>,<device>\n");
-	printf("        Sound card and device number for headset (default = '%s')\n", call_sounddev);
+	printf("        Sound card and device number for headset (default = '%s')\n", call_audiodev);
 	printf(" -t --tones 0 | 1\n");
 	printf("        Connect call on setup/release to provide classic tones towards fixed\n");
 	printf("        network (default = '%d')\n", send_patterns);
@@ -208,7 +208,7 @@ void opt_switch_common(int c, char *arg0, int *skip_args)
 		*skip_args += 2;
 		break;
 	case 'a':
-		OPT_ARRAY(num_sounddev, sounddev, strdup(optarg))
+		OPT_ARRAY(num_audiodev, audiodev, strdup(optarg))
 		*skip_args += 2;
 		break;
 	case 's':
@@ -256,7 +256,7 @@ void opt_switch_common(int c, char *arg0, int *skip_args)
 		*skip_args += 1;
 		break;
 	case 'c':
-		call_sounddev = strdup(optarg);
+		call_audiodev = strdup(optarg);
 		*skip_args += 2;
 		break;
 	case 't':
@@ -322,7 +322,7 @@ static int get_char()
 }
 
 /* Loop through all transceiver instances of one network. */
-void main_loop(int *quit, int latency, int interval, void (*myhandler)(void))
+void main_common(int *quit, int latency, int interval, void (*myhandler)(void))
 {
 	int latspl;
 	sender_t *sender;
@@ -330,11 +330,10 @@ void main_loop(int *quit, int latency, int interval, void (*myhandler)(void))
 	struct termios term, term_orig;
 	int c;
 
-	/* catch signals */
-	signal(SIGINT, sighandler);
-	signal(SIGHUP, sighandler);
-	signal(SIGTERM, sighandler);
-	signal(SIGPIPE, sighandler);
+
+	/* open audio */
+	if (sender_open_audio())
+		return;
 
 	/* real time priority */
 	if (rt_prio > 0) {
@@ -356,6 +355,12 @@ void main_loop(int *quit, int latency, int interval, void (*myhandler)(void))
 	term.c_cc[VTIME]=2;
 	tcsetattr(0, TCSANOW, &term);
 
+	/* catch signals */
+	signal(SIGINT, sighandler);
+	signal(SIGHUP, sighandler);
+	signal(SIGTERM, sighandler);
+	signal(SIGPIPE, sighandler);
+
 	while(!(*quit)) {
 		/* process sound of all transceivers */
 		for (sender = sender_head; sender; sender = sender->next) {
@@ -408,6 +413,12 @@ next_char:
 		usleep(interval * 1000);
 	}
 
+	/* reset signals */
+	signal(SIGINT, SIG_DFL);
+	signal(SIGHUP, SIG_DFL);
+	signal(SIGTERM, SIG_DFL);
+	signal(SIGPIPE, SIG_DFL);
+
 	/* get rid of last entry */
 	clear_console_text();
 
@@ -422,11 +433,5 @@ next_char:
 		schedp.sched_priority = 0;
 		sched_setscheduler(0, SCHED_OTHER, &schedp);
 	}
-
-	/* reset signals */
-	signal(SIGINT, SIG_DFL);
-	signal(SIGHUP, SIG_DFL);
-	signal(SIGTERM, SIG_DFL);
-	signal(SIGPIPE, SIG_DFL);
 }
 
diff --git a/src/common/sender.c b/src/common/sender.c
index 3a5dc43..45760e1 100644
--- a/src/common/sender.c
+++ b/src/common/sender.c
@@ -32,13 +32,15 @@ static sender_t **sender_tailp = &sender_head;
 int cant_recover = 0;
 
 /* Init transceiver instance and link to list of transceivers. */
-int sender_create(sender_t *sender, int kanal, const char *sounddev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume, enum pilot_signal pilot_signal)
+int sender_create(sender_t *sender, int kanal, double sendefrequenz, double empfangsfrequenz, const char *audiodev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume, enum pilot_signal pilot_signal)
 {
-	sender_t *master;
+	sender_t *master, *slave;
 	int rc = 0;
 
 	sender->kanal = kanal;
-	strncpy(sender->sounddev, sounddev, sizeof(sender->sounddev) - 1);
+	sender->sendefrequenz = sendefrequenz;
+	sender->empfangsfrequenz = empfangsfrequenz;
+	strncpy(sender->audiodev, audiodev, sizeof(sender->audiodev) - 1);
 	sender->samplerate = samplerate;
 	sender->rx_gain = rx_gain;
 	sender->pre_emphasis = pre_emphasis;
@@ -61,43 +63,36 @@ int sender_create(sender_t *sender, int kanal, const char *sounddev, int sampler
 			rc = -EIO;
 			goto error;
 		}
-		if (!strcmp(master->sounddev, sounddev))
+		if (!strcmp(master->audiodev, audiodev))
 			break;
 	}
 	if (master) {
-		// FIXME: link more than two channels
-		if (master->slave) {
-			PDEBUG(DSENDER, DEBUG_ERROR, "Sound device '%s' cannot be used for channel %d. It is already shared by channel %d and %d!\n", sounddev, kanal, master->kanal, master->slave->kanal);
-			rc = -EBUSY;
-			goto error;
-		}
-		if (!sound_is_stereo_capture(master->sound) || !sound_is_stereo_playback(master->sound)) {
-			PDEBUG(DSENDER, DEBUG_ERROR, "Sound device '%s' cannot be used for more than one channel, because one direction is mono!\n", sounddev);
-			rc = -EBUSY;
-			goto error;
-		}
 		if (master->pilot_signal != PILOT_SIGNAL_NONE) {
-			PDEBUG(DSENDER, DEBUG_ERROR, "Cannot share sound device with channel %d, because second channel is used for pilot signal!\n", master->kanal);
+			PDEBUG(DSENDER, DEBUG_ERROR, "Cannot share audio device with channel %d, because second channel is used for pilot signal!\n", master->kanal);
 			rc = -EBUSY;
 			goto error;
 		}
 		if (pilot_signal != PILOT_SIGNAL_NONE) {
-			PDEBUG(DSENDER, DEBUG_ERROR, "Cannot share sound device with channel %d, because we need a stereo channel for pilot signal!\n", master->kanal);
+			PDEBUG(DSENDER, DEBUG_ERROR, "Cannot share audio device with channel %d, because we need a stereo channel for pilot signal!\n", master->kanal);
 			rc = -EBUSY;
 			goto error;
 		}
-		/* link us to a master/slave */
-		master->slave = sender;
-		// FIXME: link more than two channels, so link to last slave
+		/* link us to a master */
 		sender->master = master;
+		/* link master (or last slave) to us */
+		for (slave = master; ; slave = slave->slave) {
+			if (!slave->slave)
+				break;
+		}
+		slave->slave = sender;
 	} else {
-		/* open own device */
-		sender->sound = sound_open(sounddev, samplerate);
-		if (!sender->sound) {
-			PDEBUG(DSENDER, DEBUG_ERROR, "No sound device!\n");
-
-			rc = -EIO;
-			goto error;
+		/* link audio device */
+		{
+			sender->audio_open = sound_open;
+			sender->audio_close = sound_close;
+			sender->audio_read = sound_read;
+			sender->audio_write = sound_write;
+			sender->audio_get_inbuffer = sound_get_inbuffer;
 		}
 	}
 
@@ -107,7 +102,7 @@ int sender_create(sender_t *sender, int kanal, const char *sounddev, int sampler
 		goto error;
 	}
 
-	rc = jitter_create(&sender->audio, samplerate / 5);
+	rc = jitter_create(&sender->dejitter, samplerate / 5);
 	if (rc < 0) {
 		PDEBUG(DSENDER, DEBUG_ERROR, "Failed to create and init audio buffer!\n");
 		goto error;
@@ -151,6 +146,42 @@ error:
 	return rc;
 }
 
+int sender_open_audio(void)
+{
+	sender_t *master, *inst;
+	int channels;
+	int i;
+
+	for (master = sender_head; master; master = master->next) {
+		/* skip audio slaves */
+		if (master->master)
+			continue;
+
+		/* get list of frequencies */
+		channels = 0;
+		for (inst = master; inst; inst = inst->slave) {
+			channels++;
+		}
+		double tx_f[channels], rx_f[channels];
+		for (i = 0, inst = master; inst; i++, inst = inst->slave) {
+			tx_f[i] = inst->sendefrequenz;
+			if (inst->loopback)
+				rx_f[i] = inst->sendefrequenz;
+			else
+				rx_f[i] = inst->empfangsfrequenz;
+		}
+
+		/* open device */
+		master->audio = master->audio_open(master->audiodev, tx_f, rx_f, channels, master->samplerate);
+		if (!master->audio) {
+			PDEBUG(DSENDER, DEBUG_ERROR, "No audio device!\n");
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
 /* Destroy transceiver instance and unlink from list. */
 void sender_destroy(sender_t *sender)
 {
@@ -164,16 +195,16 @@ void sender_destroy(sender_t *sender)
 			sender_tailp = &((*sender_tailp)->next);
 	}
 
-	if (sender->sound) {
-		sound_close(sender->sound);
-		sender->sound = NULL;
+	if (sender->audio) {
+		sender->audio_close(sender->audio);
+		sender->audio = NULL;
 	}
 
 	wave_destroy_record(&sender->wave_rx_rec);
 	wave_destroy_record(&sender->wave_tx_rec);
 	wave_destroy_playback(&sender->wave_rx_play);
 
-	jitter_destroy(&sender->audio);
+	jitter_destroy(&sender->dejitter);
 }
 
 static void gen_pilotton(sender_t *sender, int16_t *samples, int length)
@@ -221,19 +252,23 @@ void process_sender_audio(sender_t *sender, int *quit, int latspl)
 
 	/* count instances for audio channel */
 	for (num_chan = 0, inst = sender; inst; num_chan++, inst = inst->slave);
-	if (sender->pilot_signal) {
+	if (sender->pilot_signal != PILOT_SIGNAL_NONE) {
 		if (num_chan != 1) {
 			PDEBUG(DSENDER, DEBUG_ERROR, "Software error, please fix!\n");
 			abort();
 		}
-		num_chan++;
+		num_chan = 2;
 	}
 	int16_t buff[num_chan][latspl], *samples[num_chan];
 	for (i = 0; i < num_chan; i++)
 		samples[i] = buff[i];
 
-	count = sound_get_inbuffer(sender->sound);
+	count = sender->audio_get_inbuffer(sender->audio);
 	if (count < 0) {
+		/* special case when the device is not yet ready to transmit packets */
+		if (count == -EAGAIN) {
+			goto transmit_later;
+		}
 		PDEBUG(DSENDER, DEBUG_ERROR, "Failed to get samples in buffer (rc = %d)!\n", count);
 		if (count == -EPIPE) {
 			if (cant_recover) {
@@ -252,7 +287,7 @@ cant_recover:
 		for (i = 0, inst = sender; inst; i++, inst = inst->slave) {
 			/* load TX data from audio loop or from sender instance */
 			if (inst->loopback == 3)
-				jitter_load(&inst->audio, samples[i], count);
+				jitter_load(&inst->dejitter, samples[i], count);
 			else
 				sender_send(inst, samples[i], count);
 			if (inst->wave_tx_rec.fp)
@@ -301,9 +336,9 @@ cant_recover:
 			break;
 		}
 
-		rc = sound_write(sender->sound, samples, count, num_chan);
+		rc = sender->audio_write(sender->audio, samples, count, num_chan);
 		if (rc < 0) {
-			PDEBUG(DSENDER, DEBUG_ERROR, "Failed to write TX data to sound device (rc = %d)\n", rc);
+			PDEBUG(DSENDER, DEBUG_ERROR, "Failed to write TX data to audio device (rc = %d)\n", rc);
 			if (rc == -EPIPE) {
 				if (cant_recover)
 					goto cant_recover;
@@ -312,10 +347,16 @@ cant_recover:
 			return;
 		}
 	}
+transmit_later:
 
-	count = sound_read(sender->sound, samples, latspl, num_chan);
+	count = sender->audio_read(sender->audio, samples, latspl, num_chan);
 	if (count < 0) {
-		PDEBUG(DSENDER, DEBUG_ERROR, "Failed to read from sound device (rc = %d)!\n", count);
+		/* special case when audio_read wants us to quit */
+		if (count == -EPERM) {
+			*quit = 1;
+			return;
+		}
+		PDEBUG(DSENDER, DEBUG_ERROR, "Failed to read from audio device (rc = %d)!\n", count);
 		if (count == -EPIPE) {
 			if (cant_recover)
 				goto cant_recover;
@@ -341,7 +382,7 @@ cant_recover:
 				sender_receive(inst, samples[i], count);
 			}
 			if (inst->loopback == 3)
-				jitter_save(&inst->audio, samples[i], count);
+				jitter_save(&inst->dejitter, samples[i], count);
 		}
 	}
 }
diff --git a/src/common/sender.h b/src/common/sender.h
index 2f3fc75..c89b405 100644
--- a/src/common/sender.h
+++ b/src/common/sender.h
@@ -25,10 +25,17 @@ typedef struct sender {
 
 	/* system info */
 	int			kanal;			/* channel number */
+	double			sendefrequenz;		/* transmitter frequency */
+	double			empfangsfrequenz;	/* receiver frequency */
 
-	/* sound */
-	void			*sound;
-	char			sounddev[64];		/* sound device name */
+	/* audio */
+	void			*audio;
+	char			audiodev[64];		/* audio device name (alsa or sdr) */
+	void			*(*audio_open)(const char *, double *, double *, int, int);
+	void 			(*audio_close)(void *);
+	int			(*audio_write)(void *, int16_t **, int, int);
+	int			(*audio_read)(void *, int16_t **, int, int);
+	int			(*audio_get_inbuffer)(void *);
 	int			samplerate;
 	samplerate_t		srstate;		/* sample rate conversion state */
 	double			rx_gain;		/* factor of level to apply on rx samples */
@@ -45,7 +52,7 @@ typedef struct sender {
 	wave_play_t		wave_rx_play;		/* wave playback (as rx) */
 
 	/* audio buffer for audio to send to transmitter (also used as loopback buffer) */
-	jitter_t		audio;
+	jitter_t		dejitter;
 
 	/* audio buffer for audio to send to caller (20ms = 160 samples @ 8000Hz) */
 	int16_t			rxbuf[160];
@@ -69,8 +76,9 @@ typedef struct sender {
 extern sender_t *sender_head;
 extern int cant_recover;
 
-int sender_create(sender_t *sender, int kanal, const char *sounddev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume, enum pilot_signal pilot_signal);
+int sender_create(sender_t *sender, int kanal, double sendefrequenz, double empfangsfrequenz, const char *audiodev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, int loopback, double loss_volume, enum pilot_signal pilot_signal);
 void sender_destroy(sender_t *sender);
+int sender_open_audio(void);
 void process_sender_audio(sender_t *sender, int *quit, int latspl);
 void sender_send(sender_t *sender, int16_t *samples, int count);
 void sender_receive(sender_t *sender, int16_t *samples, int count);
diff --git a/src/common/sound.h b/src/common/sound.h
index b516fdf..45eb2c0 100644
--- a/src/common/sound.h
+++ b/src/common/sound.h
@@ -1,9 +1,7 @@
 
-void *sound_open(const char *device, int samplerate);
+void *sound_open(const char *audiodev, double *tx_frequency, double *rx_frequency, int channels, int samplerate);
 void sound_close(void *inst);
 int sound_write(void *inst, int16_t **samples, int num, int channels);
 int sound_read(void *inst, int16_t **samples, int num, int channels);
 int sound_get_inbuffer(void *inst);
-int sound_is_stereo_capture(void *inst);
-int sound_is_stereo_playback(void *inst);
 
diff --git a/src/common/sound_alsa.c b/src/common/sound_alsa.c
index 219971f..15fe1a9 100644
--- a/src/common/sound_alsa.c
+++ b/src/common/sound_alsa.c
@@ -128,26 +128,31 @@ static int sound_prepare(sound_t *sound)
 	return 0;
 }
 
-void *sound_open(const char *device, int samplerate)
+void *sound_open(const char *audiodev, double __attribute__((unused)) *tx_frequency, double __attribute__((unused)) *rx_frequency, int channels, int samplerate)
 {
 	sound_t *sound;
 	int rc;
 
+	if (channels < 1 || channels > 2) {
+		PDEBUG(DSOUND, DEBUG_ERROR, "Cannot use more than two channels with the same sound card!\n");
+		return NULL;
+	}
+
 	sound = calloc(1, sizeof(sound_t));
 	if (!sound) {
 		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to alloc memory!\n");
 		return NULL;
 	}
 
-	rc = snd_pcm_open(&sound->phandle, device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
+	rc = snd_pcm_open(&sound->phandle, audiodev, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
 	if (rc < 0) {
-		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to open '%s' for playback! (%s)\n", device, snd_strerror(rc));
+		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to open '%s' for playback! (%s)\n", audiodev, snd_strerror(rc));
 		goto error;
 	}
 
-	rc = snd_pcm_open(&sound->chandle, device, SND_PCM_STREAM_CAPTURE, SND_PCM_NONBLOCK);
+	rc = snd_pcm_open(&sound->chandle, audiodev, SND_PCM_STREAM_CAPTURE, SND_PCM_NONBLOCK);
 	if (rc < 0) {
-		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to open '%s' for capture! (%s)\n", device, snd_strerror(rc));
+		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to open '%s' for capture! (%s)\n", audiodev, snd_strerror(rc));
 		goto error;
 	}
 
@@ -156,6 +161,10 @@ void *sound_open(const char *device, int samplerate)
 		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to set playback hw params\n");
 		goto error;
 	}
+	if (sound->pchannels < channels) {
+		PDEBUG(DSOUND, DEBUG_ERROR, "Sound card only supports %d channel for playback.\n", sound->pchannels);
+		goto error;
+	}
 	PDEBUG(DSOUND, DEBUG_DEBUG, "Playback with %d channels.\n", sound->pchannels);
 
 	rc = set_hw_params(sound->chandle, samplerate, &sound->cchannels);
@@ -163,6 +172,10 @@ void *sound_open(const char *device, int samplerate)
 		PDEBUG(DSOUND, DEBUG_ERROR, "Failed to set capture hw params\n");
 		goto error;
 	}
+	if (sound->cchannels < channels) {
+		PDEBUG(DSOUND, DEBUG_ERROR, "Sound card only supports %d channel for capture.\n", sound->cchannels);
+		goto error;
+	}
 	PDEBUG(DSOUND, DEBUG_DEBUG, "Capture with %d channels.\n", sound->cchannels);
 
 	rc = sound_prepare(sound);
diff --git a/src/nmt/dsp.c b/src/nmt/dsp.c
index f0069e8..49f7fb4 100644
--- a/src/nmt/dsp.c
+++ b/src/nmt/dsp.c
@@ -624,7 +624,7 @@ again:
 	switch (nmt->dsp_mode) {
 	case DSP_MODE_AUDIO:
 	case DSP_MODE_DTMF:
-		jitter_load(&nmt->sender.audio, samples, length);
+		jitter_load(&nmt->sender.dejitter, samples, length);
 		/* send after dejitter, so audio is flushed */
 		if (nmt->dms.frame_valid) {
 			fsk_dms_frame(nmt, samples, length);
diff --git a/src/nmt/main.c b/src/nmt/main.c
index c34e1e6..085330a 100644
--- a/src/nmt/main.c
+++ b/src/nmt/main.c
@@ -281,9 +281,9 @@ int main(int argc, char *argv[])
 		printf("No channel (\"Kanal\") is specified, I suggest channel 1 (-k 1).\n\n");
 		mandatory = 1;
 	}
-	if (num_kanal == 1 && num_sounddev == 0)
-		num_sounddev = 1; /* use defualt */
-	if (num_kanal != num_sounddev) {
+	if (num_kanal == 1 && num_audiodev == 0)
+		num_audiodev = 1; /* use defualt */
+	if (num_kanal != num_audiodev) {
 		fprintf(stderr, "You need to specify as many sound devices as you have channels.\n");
 		exit(0);
 	}
@@ -335,7 +335,7 @@ int main(int argc, char *argv[])
 		return -1;
 	}
 	dsp_init();
-	rc = call_init(station_id, call_sounddev, samplerate, latency, 7, loopback);
+	rc = call_init(station_id, call_audiodev, samplerate, latency, 7, loopback);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create call control instance. Quitting!\n");
 		goto fail;
@@ -343,21 +343,21 @@ int main(int argc, char *argv[])
 
 	/* create transceiver instance */
 	for (i = 0; i < num_kanal; i++) {
-		rc = nmt_create(kanal[i], (loopback) ? CHAN_TYPE_TEST : chan_type[i], sounddev[i], samplerate, rx_gain, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, ms_power, nmt_digits2value(traffic_area, 2), area_no, compandor, supervisory, smsc_number, send_callerid, loopback);
+		rc = nmt_create(kanal[i], (loopback) ? CHAN_TYPE_TEST : chan_type[i], audiodev[i], samplerate, rx_gain, do_pre_emphasis, do_de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, ms_power, nmt_digits2value(traffic_area, 2), area_no, compandor, supervisory, smsc_number, send_callerid, loopback);
 		if (rc < 0) {
 			fprintf(stderr, "Failed to create transceiver instance. Quitting!\n");
 			goto fail;
 		}
 		if (kanal[i] > 200) {
-			printf("Base station on channel %d ready, please tune transmitter to %.4f MHz and receiver to %.4f MHz.\n", kanal[i], nmt_channel2freq(kanal[i], 0), nmt_channel2freq(kanal[i], 1));
+			printf("Base station on channel %d ready, please tune transmitter to %.4f MHz and receiver to %.4f MHz.\n", kanal[i], nmt_channel2freq(kanal[i], 0) / 1e6, nmt_channel2freq(kanal[i], 1) / 1e6);
 		} else {
-			printf("Base station on channel %d ready, please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], nmt_channel2freq(kanal[i], 0), nmt_channel2freq(kanal[i], 1));
+			printf("Base station on channel %d ready, please tune transmitter to %.3f MHz and receiver to %.3f MHz.\n", kanal[i], nmt_channel2freq(kanal[i], 0) / 1e6, nmt_channel2freq(kanal[i], 1) / 1e6);
 		}
 	}
 
 	nmt_check_channels();
 
-	main_loop(&quit, latency, interval, myhandler);
+	main_common(&quit, latency, interval, myhandler);
 
 fail:
 	/* fifo */
diff --git a/src/nmt/nmt.c b/src/nmt/nmt.c
index 46c9775..db764ec 100644
--- a/src/nmt/nmt.c
+++ b/src/nmt/nmt.c
@@ -218,7 +218,7 @@ double nmt_channel2freq(int channel, int uplink)
 	if (uplink)
 		freq -= 10.000;
 
-	return freq;
+	return freq * 1e6;
 }
 
 /* convert 7-digits dial string to NMT number */
@@ -303,7 +303,7 @@ uint8_t nmt_country_by_short_name(const char *short_name)
 static void nmt_timeout(struct timer *timer);
 
 /* Create transceiver instance and link to a list. */
-int nmt_create(int channel, enum nmt_chan_type chan_type, const char *sounddev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, uint8_t ms_power, uint8_t traffic_area, uint8_t area_no, int compandor, int supervisory, const char *smsc_number, int send_callerid, int loopback)
+int nmt_create(int channel, enum nmt_chan_type chan_type, const char *audiodev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, uint8_t ms_power, uint8_t traffic_area, uint8_t area_no, int compandor, int supervisory, const char *smsc_number, int send_callerid, int loopback)
 {
 	nmt_t *nmt;
 	int rc;
@@ -334,7 +334,7 @@ int nmt_create(int channel, enum nmt_chan_type chan_type, const char *sounddev,
 	PDEBUG(DNMT, DEBUG_DEBUG, "Creating 'NMT' instance for channel = %d (sample rate %d).\n", channel, samplerate);
 
 	/* init general part of transceiver */
-	rc = sender_create(&nmt->sender, channel, sounddev, samplerate, rx_gain, pre_emphasis, de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, 0, PILOT_SIGNAL_NONE);
+	rc = sender_create(&nmt->sender, channel, nmt_channel2freq(channel, 0), nmt_channel2freq(channel, 1), audiodev, samplerate, rx_gain, pre_emphasis, de_emphasis, write_rx_wave, write_tx_wave, read_rx_wave, loopback, 0, PILOT_SIGNAL_NONE);
 	if (rc < 0) {
 		PDEBUG(DNMT, DEBUG_ERROR, "Failed to init transceiver process!\n");
 		goto error;
@@ -1816,7 +1816,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 		if (nmt->compandor)
 			compress_audio(&nmt->cstate, samples, count);
 		count = samplerate_upsample(&nmt->sender.srstate, samples, count, up);
-		jitter_save(&nmt->sender.audio, up, count);
+		jitter_save(&nmt->sender.dejitter, up, count);
 	}
 }
 
diff --git a/src/nmt/nmt.h b/src/nmt/nmt.h
index 6cb8c73..f09d33d 100644
--- a/src/nmt/nmt.h
+++ b/src/nmt/nmt.h
@@ -143,7 +143,7 @@ const char *chan_type_long_name(enum nmt_chan_type chan_type);
 double nmt_channel2freq(int channel, int uplink);
 void nmt_country_list(void);
 uint8_t nmt_country_by_short_name(const char *short_name);
-int nmt_create(int channel, enum nmt_chan_type chan_type, const char *sounddev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, uint8_t ms_power, uint8_t traffic_area, uint8_t area_no, int compandor, int supervisory, const char *smsc_number, int send_callerid, int loopback);
+int nmt_create(int channel, enum nmt_chan_type chan_type, const char *audiodev, int samplerate, double rx_gain, int pre_emphasis, int de_emphasis, const char *write_rx_wave, const char *write_tx_wave, const char *read_rx_wave, uint8_t ms_power, uint8_t traffic_area, uint8_t area_no, int compandor, int supervisory, const char *smsc_number, int send_callerid, int loopback);
 void nmt_check_channels(void);
 void nmt_destroy(sender_t *sender);
 void nmt_go_idle(nmt_t *nmt);