FM Stereo experiment, partly working

src/demod/DemodDefs.h

@@ -70,13 +70,14 @@ public:
 class DemodulatorThreadPostIQData: public ReferenceCounter {
 public:
     std::vector<liquid_float_complex> data;
+    int bandwidth;
     float audio_resample_ratio;
     msresamp_rrrf audio_resampler;
     float resample_ratio;
     msresamp_crcf resampler;
 
     DemodulatorThreadPostIQData() :
-            audio_resample_ratio(0), audio_resampler(NULL), resample_ratio(0), resampler(NULL) {
+            bandwidth(0), audio_resample_ratio(0), audio_resampler(NULL), resample_ratio(0), resampler(NULL) {
 
     }
 

src/demod/DemodulatorInstance.cpp

@@ -146,6 +146,16 @@ void DemodulatorInstance::setActive(bool state) {
     audioThread->setActive(state);
 }
 
+bool DemodulatorInstance::isStereo() {
+    return stereo;
+}
+
+void DemodulatorInstance::setStereo(bool state) {
+    stereo = state;
+    demodulatorThread->setStereo(state);
+}
+
+
 void DemodulatorInstance::squelchAuto() {
     DemodulatorThreadControlCommand command;
     command.cmd = DemodulatorThreadControlCommand::DEMOD_THREAD_CMD_CTL_SQUELCH_AUTO;

src/demod/DemodulatorInstance.h

@@ -49,6 +49,9 @@ public:
     bool isActive();
     void setActive(bool state);
 
+    bool isStereo();
+    void setStereo(bool state);
+
     void squelchAuto();bool isSquelchEnabled();
     void setSquelchEnabled(bool state);
 
@@ -56,5 +59,6 @@ private:
     std::atomic<std::string *> label;bool terminated;bool demodTerminated;bool audioTerminated;bool preDemodTerminated;
     std::atomic<bool> active;
     std::atomic<bool> squelch;
+    std::atomic<bool> stereo;
 };
 

src/demod/DemodulatorPreThread.cpp

@@ -219,6 +219,7 @@ void DemodulatorPreThread::threadMain() {
             resamp->audio_resampler = audio_resampler;
             resamp->resample_ratio = resample_ratio;
             resamp->resampler = resampler;
+            resamp->bandwidth = params.bandwidth;
 
             postInputQueue->push(resamp);
         }

src/demod/DemodulatorThread.cpp

@@ -8,7 +8,7 @@
 
 DemodulatorThread::DemodulatorThread(DemodulatorThreadPostInputQueue* pQueue, DemodulatorThreadControlCommandQueue *threadQueueControl,
         DemodulatorThreadCommandQueue* threadQueueNotify) :
-        postInputQueue(pQueue), visOutQueue(NULL), audioInputQueue(NULL), agc(NULL), terminated(false), threadQueueNotify(threadQueueNotify), threadQueueControl(
+        postInputQueue(pQueue), visOutQueue(NULL), audioInputQueue(NULL), agc(NULL), stereo(false), terminated(false), threadQueueNotify(threadQueueNotify), threadQueueControl(
                 threadQueueControl), squelch_level(0), squelch_tolerance(0), squelch_enabled(false) {
 
     float kf = 0.5;         // modulation factor
@@ -44,7 +44,11 @@ void DemodulatorThread::threadMain() {
     std::vector<liquid_float_complex> resampled_data;
     std::vector<liquid_float_complex> agc_data;
     std::vector<float> demod_output;
+    std::vector<float> demod_output_stereo;
     std::vector<float> resampled_audio_output;
+    std::vector<float> resampled_audio_output_stereo;
+
+    double freq_index = 0;
 
     while (!terminated) {
         DemodulatorThreadPostIQData *inp;
@@ -89,24 +93,49 @@ void DemodulatorThread::threadMain() {
         if (demod_output.size() != num_written) {
             if (demod_output.capacity() < num_written) {
                 demod_output.reserve(num_written);
+                demod_output_stereo.reserve(num_written);
             }
             demod_output.resize(num_written);
+            demod_output_stereo.resize(num_written);
         }
 
         freqdem_demodulate_block(fdem, &agc_data[0], num_written, &demod_output[0]);
 
+        if (stereo) {
+            int shift_freq = 38000-inp->bandwidth;
+            double freq =  (2.0 * M_PI) * (((double) abs(shift_freq)) / ((double) inp->bandwidth));
+
+            for (int i = 0; i < num_written; i++) {
+                freq_index+=freq;
+
+                demod_output_stereo[i] = demod_output[i] * sin(freq_index) + demod_output[i] * cos(freq_index);
+                while (freq_index > (M_PI*2.0)) {
+                    freq_index -= (M_PI*2.0);
+                }
+                while (freq_index < (M_PI*2.0)) {
+                    freq_index += (M_PI*2.0);
+                }
+            }
+        }
+
         int audio_out_size = ceil((float) (num_written) * audio_resample_ratio);
 
         if (audio_out_size != resampled_audio_output.size()) {
             if (resampled_audio_output.capacity() < audio_out_size) {
                 resampled_audio_output.reserve(audio_out_size);
+                resampled_audio_output_stereo.reserve(audio_out_size);
             }
             resampled_audio_output.resize(audio_out_size);
+            resampled_audio_output_stereo.resize(audio_out_size);
         }
 
         unsigned int num_audio_written;
         msresamp_rrrf_execute(audio_resampler, &demod_output[0], num_written, &resampled_audio_output[0], &num_audio_written);
 
+        if (stereo) {
+            msresamp_rrrf_execute(audio_resampler, &demod_output_stereo[0], num_written, &resampled_audio_output_stereo[0], &num_audio_written);
+        }
+
         if (audioInputQueue != NULL) {
             if (!squelch_enabled || ((agc_crcf_get_signal_level(agc)) >= 0.1)) {
                 AudioThreadInput *ati = NULL;
@@ -124,8 +153,18 @@ void DemodulatorThread::threadMain() {
                 }
 
                 ati->setRefCount(1);
-                ati->channels = 1;
-                ati->data.assign(resampled_audio_output.begin(), resampled_audio_output.begin() + num_audio_written);
+
+                if (stereo) {
+                    ati->channels = 2;
+                    ati->data.resize(num_audio_written*2);
+                    for (int i = 0; i < num_audio_written; i++) {
+                        ati->data[i*2] = (resampled_audio_output[i]-(resampled_audio_output_stereo[i]*2.0))/2.0;
+                        ati->data[i*2+1] = (resampled_audio_output[i]+(resampled_audio_output_stereo[i]*2.0))/2.0;
+                    }
+                } else {
+                    ati->channels = 1;
+                    ati->data.assign(resampled_audio_output.begin(), resampled_audio_output.begin() + num_audio_written);
+                }
 
                 audioInputQueue->push(ati);
             }
@@ -204,3 +243,12 @@ void DemodulatorThread::terminate() {
     DemodulatorThreadPostIQData *inp = new DemodulatorThreadPostIQData;    // push dummy to nudge queue
     postInputQueue->push(inp);
 }
+
+
+void DemodulatorThread::setStereo(bool state) {
+    stereo = state;
+}
+
+bool DemodulatorThread::isStereo() {
+    return stereo;
+}

src/demod/DemodulatorThread.h

@@ -35,6 +35,9 @@ public:
 
     void terminate();
 
+    void setStereo(bool state);
+    bool isStereo();
+
 #ifdef __APPLE__
     static void *pthread_helper(void *context) {
         return ((DemodulatorThread *) context)->threadMain();
@@ -49,6 +52,7 @@ protected:
     freqdem fdem;
     agc_crcf agc;
 
+    std::atomic<bool> stereo;
     std::atomic<bool> terminated;
 
     DemodulatorThreadCommandQueue* threadQueueNotify;

src/visual/WaterfallCanvas.cpp

@@ -200,6 +200,16 @@ void WaterfallCanvas::OnKeyDown(wxKeyEvent& event) {
             activeDemod->squelchAuto();
         }
         break;
+    case WXK_SPACE:
+          if (!activeDemod) {
+              break;
+          }
+          if (activeDemod->isStereo()) {
+              activeDemod->setStereo(false);
+          } else {
+              activeDemod->setStereo(true);
+          }
+          break;
     default:
         event.Skip();
         return;