Issue 401 - Avoid receiving own transmission due to audio crosstalk.

src/demod.c

@@ -852,7 +852,6 @@ int demod_init (struct audio_s *pa)
 
 #define FSK_READ_ERR (256*256)
 
-
 __attribute__((hot))
 int demod_get_sample (int a)		
 {
@@ -862,7 +861,6 @@ int demod_get_sample (int a)
 
 	assert (save_audio_config_p->adev[a].bits_per_sample == 8 || save_audio_config_p->adev[a].bits_per_sample == 16);
 
-
 	if (save_audio_config_p->adev[a].bits_per_sample == 8) {
 
 	  x1 = audio_get(a);				
@@ -929,6 +927,21 @@ int demod_get_sample (int a)
  *
  *--------------------------------------------------------------------*/
 
+static int mute_input[MAX_CHANS];
+
+// New in 1.7.
+// A few people have a really bad audio cross talk situation where they receive their own transmissions.
+// It usually doesn't cause a problem but it is confusing to look at.
+// "half duplex" setting applied only to the transmit logic.  i.e. wait for clear channel before sending.
+// Receiving was still active.
+// I think the simplest solution is to mute/unmute the audio input at this point if not full duplex.
+// This is called from ptt_set for half duplex.
+
+void demod_mute_input (int chan, int mute_during_xmit)
+{
+	assert (chan >= 0 && chan < MAX_CHANS);
+	mute_input[chan] = mute_during_xmit;
+}
 
 __attribute__((hot))
 void demod_process_sample (int chan, int subchan, int sam)
@@ -942,6 +955,10 @@ void demod_process_sample (int chan, int subchan, int sam)
 	assert (chan >= 0 && chan < MAX_CHANS);
 	assert (subchan >= 0 && subchan < MAX_SUBCHANS);
 
+	if (mute_input[chan]) {
+	  sam = 0;
+	};
+
 	D = &demodulator_state[chan][subchan];
 
 

src/demod.h

@@ -8,6 +8,8 @@
 
 int demod_init (struct audio_s *pa);
 
+void demod_mute_input (int chan, int mute);
+
 int demod_get_sample (int a);
 
 void demod_process_sample (int chan, int subchan, int sam);
@@ -15,3 +17,4 @@ void demod_process_sample (int chan, int subchan, int sam);
 void demod_print_agc (int chan, int subchan);
 
 alevel_t demod_get_audio_level (int chan, int subchan);
+

src/ptt.c

@@ -1,7 +1,7 @@
 //
 //    This file is part of Dire Wolf, an amateur radio packet TNC.
 //
-//    Copyright (C) 2011, 2013, 2014, 2015, 2016, 2017  John Langner, WB2OSZ
+//    Copyright (C) 2011, 2013, 2014, 2015, 2016, 2017, 2023  John Langner, WB2OSZ
 //
 //    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
@@ -176,6 +176,7 @@ typedef int HANDLE;
 #include "audio.h"
 #include "ptt.h"
 #include "dlq.h"
+#include "demod.h"	// to mute recv audio during xmit if half duplex.
 
 
 #if __WIN32__
@@ -1141,6 +1142,8 @@ void ptt_init (struct audio_s *audio_config_p)
  *
  *--------------------------------------------------------------------*/
 
+// JWL - save status and new get_ptt function.
+
 
 void ptt_set (int ot, int chan, int ptt_signal)
 {
@@ -1164,6 +1167,19 @@ void ptt_set (int ot, int chan, int ptt_signal)
 	  return;
 	}
 
+// New in 1.7.
+// A few people have a really bad audio cross talk situation where they receive their own transmissions.
+// It usually doesn't cause a problem but it is confusing to look at.
+// "half duplex" setting applied only to the transmit logic.  i.e. wait for clear channel before sending.
+// Receiving was still active.
+// I think the simplest solution is to mute/unmute the audio input at this point if not full duplex.
+
+#ifndef TEST
+	if ( ! save_audio_config_p->achan[chan].fulldup) {
+	  demod_mute_input (chan, ptt_signal);
+	}
+#endif
+
 /*
  * The data link state machine has an interest in activity on the radio channel.
  * This is a very convenient place to get that information.