Fixed waterfall at very low samplerates

core/src/gui/main_window.cpp

@@ -38,9 +38,6 @@ void MainWindow::init() {
     gui::waterfall.init();
     gui::waterfall.setRawFFTSize(fftSize);
 
-    appliedWindow = new float[fftSize];
-    generateFFTWindow(selectedWindow, fftSize);
-
     credits::init();
 
     core::configManager.acquire();
@@ -215,10 +212,14 @@ void MainWindow::init() {
 void MainWindow::fftHandler(dsp::complex_t* samples, int count, void* ctx) {
     MainWindow* _this = (MainWindow*)ctx;
     std::lock_guard<std::mutex> lck(_this->fft_mtx);
-    if (count != _this->fftSize) { return; }
 
     // Apply window
-    volk_32fc_32f_multiply_32fc((lv_32fc_t*)_this->fft_in, (lv_32fc_t*)samples, _this->appliedWindow, count);
+    volk_32fc_32f_multiply_32fc((lv_32fc_t*)_this->fft_in, (lv_32fc_t*)samples, sigpath::signalPath.fftTaps, count);
+
+    // Zero out the rest of the samples
+    if (count < _this->fftSize) {
+        memset(&_this->fft_in[count], 0, (_this->fftSize-count) * sizeof(dsp::complex_t));
+    } 
 
     // Execute FFT
     fftwf_execute(_this->fftwPlan);
@@ -231,7 +232,7 @@ void MainWindow::fftHandler(dsp::complex_t* samples, int count, void* ctx) {
     }
 
     // Take power of spectrum
-    volk_32fc_s32f_power_spectrum_32f(fftBuf, (lv_32fc_t*)_this->fft_out, count, count);
+    volk_32fc_s32f_power_spectrum_32f(fftBuf, (lv_32fc_t*)_this->fft_out, _this->fftSize, _this->fftSize);
 
     // Push back data
     gui::waterfall.pushFFT();
@@ -663,30 +664,11 @@ void MainWindow::setFFTSize(int size) {
     fft_in = (fftwf_complex*)fftwf_malloc(sizeof(fftwf_complex) * fftSize);
     fft_out = (fftwf_complex*)fftwf_malloc(sizeof(fftwf_complex) * fftSize);
     fftwPlan = fftwf_plan_dft_1d(fftSize, fft_in, fft_out, FFTW_FORWARD, FFTW_ESTIMATE);
-
-    delete appliedWindow;
-
-    appliedWindow = new float[fftSize];
-    generateFFTWindow(selectedWindow, fftSize);
 }
 
 void MainWindow::setFFTWindow(int win) {
     std::lock_guard<std::mutex> lck(fft_mtx);
-    selectedWindow = win;
-    generateFFTWindow(selectedWindow, fftSize);
-}
-
-void MainWindow::generateFFTWindow(int win, int size) {
-    if (win == FFT_WINDOW_RECTANGULAR) {
-        for (int i = 0; i < size; i++) {
-            appliedWindow[i] = (i%2) ? 1 : -1;
-        }
-    }
-    else if (win == FFT_WINDOW_BLACKMAN) {
-        for (int i = 0; i < size; i++) {
-            appliedWindow[i] = ((i%2) ? dsp::window_function::blackman(i, size) : -dsp::window_function::blackman(i, size))*2;
-        }
-    }
+    sigpath::signalPath.setFFTWindow(win);
 }
 
 bool MainWindow::isPlaying() {

core/src/gui/main_window.h

@@ -11,12 +11,6 @@
 
 #define WINDOW_FLAGS    ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoBackground
 
-enum {
-    FFT_WINDOW_RECTANGULAR,
-    FFT_WINDOW_BLACKMAN,
-    _FFT_WINDOW_COUNT
-};
-
 class MainWindow {
 public:
     void init();
@@ -37,7 +31,6 @@ public:
     Event<bool> onPlayStateChange;
 
 private:
-    void generateFFTWindow(int win, int size);
     static void fftHandler(dsp::complex_t* samples, int count, void* ctx);
     static void vfoAddedHandler(VFOManager::VFO* vfo, void* ctx);
 
@@ -46,7 +39,6 @@ private:
     std::mutex fft_mtx;
     fftwf_complex *fft_in, *fft_out;
     fftwf_plan fftwPlan;
-    float* appliedWindow;
     
     // GUI Variables
     bool firstMenuRender = true;

core/src/signal_path/dsp.cpp

@@ -14,12 +14,22 @@ void SignalPath::init(uint64_t sampleRate, int fftRate, int fftSize, dsp::stream
 
     halfBandWindow.init(1000000, 200000, 4000000);
 
-    // split.init(input);
     inputBuffer.init(input);
     corrector.init(&inputBuffer.out, 50.0f / sampleRate);
     split.init(&inputBuffer.out);
 
-    reshape.init(&fftStream, fftSize, (sampleRate / fftRate) - fftSize);
+    // Allocate the fft taps
+    fftTaps = new float[fftSize];
+
+    // Calculate the parameters for the reshaper
+    int fftInterval = sampleRate / fftRate;
+    fftOutputSampleCount = std::min<int>(fftInterval, fftSize);
+    int fftSkip = fftInterval - fftOutputSampleCount;
+
+    // Generate FFT Windows
+    generateFFTWindow(fftWindow, fftTaps, fftOutputSampleCount);
+
+    reshape.init(&fftStream, fftSize, fftSkip);
     split.bindStream(&fftStream);
     fftHandlerSink.init(&reshape.out, fftHandler, fftHandlerCtx);
 }
@@ -27,26 +37,29 @@ void SignalPath::init(uint64_t sampleRate, int fftRate, int fftSize, dsp::stream
 void SignalPath::setSampleRate(double sampleRate) {
     this->sampleRate = sampleRate;
 
+    // Stop the splitter
     split.stop();
+    reshape.stop();
 
+    // Stop all VFOs
     for (auto const& [name, vfo] : vfos) {
         vfo.vfo->stop();
     }
 
-    // Claculate skip to maintain a constant fft rate
-    int skip = (sampleRate / fftRate) - fftSize;
-    reshape.setSkip(skip);
-
-    // TODO: Tell modules that the block size has changed (maybe?)
+    updateFFTDSP();
 
+    // Update the sample rate for all VFOs and start them up
     for (auto const& [name, vfo] : vfos) {
         vfo.vfo->setInSampleRate(sampleRate);
         vfo.vfo->start();
     }
 
+    // Update correction rate on the IQ corrector
     corrector.setCorrectionRate(50.0f / sampleRate);
 
+    // Start the splitter
     split.start();
+    reshape.start();
 }
 
 double SignalPath::getSampleRate() {
@@ -117,19 +130,15 @@ void SignalPath::unbindIQStream(dsp::stream<dsp::complex_t>* stream) {
 
 void SignalPath::setFFTSize(int size) {
     fftSize = size;
-    int skip = (sampleRate / fftRate) - fftSize;
     reshape.stop();
-    reshape.setSkip(skip);
-    reshape.setKeep(fftSize);
+    updateFFTDSP();
     reshape.start();
 }
 
 void SignalPath::setFFTRate(double rate) {
     fftRate = rate;
-    int skip = (sampleRate / fftRate) - fftSize;
     reshape.stop();
-    reshape.setSkip(skip);
-    reshape.setKeep(fftSize);
+    updateFFTDSP();
     reshape.start();
 }
 
@@ -226,4 +235,45 @@ void SignalPath::setIQCorrection(bool enabled) {
         corrector.offset.re = 0;
         corrector.offset.im = 0;
     }
+}
+
+void SignalPath::setFFTWindow(int win) {
+    fftWindow = win;
+    reshape.stop();
+    updateFFTDSP();
+    reshape.start();
+}
+
+void SignalPath::generateFFTWindow(int win, float* taps, int size) {
+    if (win == FFT_WINDOW_RECTANGULAR) {
+        for (int i = 0; i < size; i++) {
+            taps[i] = (i%2) ? 1 : -1;
+        }
+    }
+    else if (win == FFT_WINDOW_BLACKMAN) {
+        for (int i = 0; i < size; i++) {
+            taps[i] = ((i%2) ? dsp::window_function::blackman(i, size) : -dsp::window_function::blackman(i, size))*2;
+        }
+    }
+}
+
+void SignalPath::updateFFTDSP() {
+
+    // Allocate the fft taps
+    if (fftTaps != NULL) { delete[] fftTaps; }
+    fftTaps = new float[fftSize];
+
+    // Calculate the parameters for the reshaper
+    int fftInterval = sampleRate / fftRate;
+    fftOutputSampleCount = std::min<int>(fftInterval, fftSize);
+    int fftSkip = fftInterval - fftOutputSampleCount;
+
+    // Generate FFT Windows
+    generateFFTWindow(fftWindow, fftTaps, fftOutputSampleCount);
+
+    // Update parameters of the reshaper
+    reshape.setKeep(fftOutputSampleCount);
+    reshape.setSkip(fftSkip);
+
+    spdlog::info("Updating FFT DSP settings: Keep: {0}, Skip: {1}", fftOutputSampleCount, fftSkip);
 }

core/src/signal_path/dsp.h

@@ -6,6 +6,12 @@
 #include <dsp/decimation.h>
 #include <dsp/correction.h>
 
+enum {
+    FFT_WINDOW_RECTANGULAR,
+    FFT_WINDOW_BLACKMAN,
+    _FFT_WINDOW_COUNT
+};
+
 class SignalPath {
 public:
     SignalPath();
@@ -26,12 +32,18 @@ public:
     void setBuffering(bool enabled);
     void setDecimation(int dec);
     void setIQCorrection(bool enabled);
+    void setFFTWindow(int win);
 
     dsp::SampleFrameBuffer<dsp::complex_t> inputBuffer;
     double sourceSampleRate = 0;
     int decimation = 0;
 
+    float* fftTaps = NULL;
+
 private:
+    void generateFFTWindow(int win, float* taps, int size);
+    void updateFFTDSP();
+
     struct VFO_t {
         dsp::stream<dsp::complex_t>* inputStream;
         dsp::VFO* vfo;
@@ -50,10 +62,12 @@ private:
     std::vector<dsp::HalfDecimator<dsp::complex_t>*> decimators;
     dsp::filter_window::BlackmanWindow halfBandWindow;
 
+    int fftOutputSampleCount = 0;
     double sampleRate;
     double fftRate;
     int fftSize;
     int inputBlockSize;
+    int fftWindow = FFT_WINDOW_RECTANGULAR;
     bool bufferingEnabled = false;
     bool running = false;
     bool iqCorrection = false;

core/src/version.h

@@ -1,3 +1,3 @@
 #pragma once
 
-#define VERSION_STR "1.0.0_rc4"
+#define VERSION_STR "1.0.0_rc5"