Added a time resolution slider

mainwindow.cpp

@@ -46,6 +46,7 @@ MainWindow::MainWindow()
     connect(dock, SIGNAL(fftOrZoomChanged(int, int)), plots, SLOT(setFFTAndZoom(int, int)));
     connect(dock->powerMaxSlider, SIGNAL(valueChanged(int)), plots, SLOT(setPowerMax(int)));
     connect(dock->powerMinSlider, SIGNAL(valueChanged(int)), plots, SLOT(setPowerMin(int)));
+    connect(dock->timeResolutionSlider, SIGNAL(valueChanged(int)), plots, SLOT(setTimeResolution(int)));
     connect(dock->cursorsCheckBox, &QCheckBox::stateChanged, plots, &PlotView::enableCursors);
     connect(dock->scalesCheckBox, &QCheckBox::stateChanged, plots, &PlotView::enableScales);
     connect(dock->cursorSymbolsSpinBox, static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged), plots, &PlotView::setCursorSegments);

plotview.cpp

@@ -382,20 +382,27 @@ void PlotView::setFFTAndZoom(int size, int zoom)
 
 void PlotView::setPowerMin(int power)
 {
-    powerMin = power;
+//  HVI_REVIEW: Not needed?   powerMin = power;
     if (spectrogramPlot != nullptr)
         spectrogramPlot->setPowerMin(power);
     updateView();
 }
 
 void PlotView::setPowerMax(int power)
 {
-    powerMax = power;
+//  HVI_REVIEW: Not needed?  powerMax = power;
     if (spectrogramPlot != nullptr)
         spectrogramPlot->setPowerMax(power);
     updateView();
 }
 
+void PlotView::setTimeResolution(int resolution)
+{
+    if (spectrogramPlot != nullptr)
+        spectrogramPlot->setTimeResolution(resolution);
+//    updateView(true);
+}
+
 void PlotView::paintEvent(QPaintEvent *event)
 {
     if (mainSampleSource == nullptr) return;

plotview.h

@@ -52,6 +52,7 @@ public slots:
     void setFFTAndZoom(int fftSize, int zoomLevel);
     void setPowerMin(int power);
     void setPowerMax(int power);
+    void setTimeResolution(int resolution);
 
 protected:
     void contextMenuEvent(QContextMenuEvent * event) override;
@@ -70,8 +71,8 @@ public slots:
 
     int fftSize = 1024;
     int zoomLevel = 0;
-    int powerMin;
-    int powerMax;
+//    int powerMin;
+//    int powerMax;
     bool cursorsEnabled;
     off_t sampleRate = 0;
     bool timeScaleEnabled;

spectrogramcontrols.cpp

@@ -63,6 +63,10 @@ SpectrogramControls::SpectrogramControls(const QString & title, QWidget * parent
     powerMinSlider->setRange(-140, 10);
     layout->addRow(new QLabel(tr("Power min:")), powerMinSlider);
 
+    timeResolutionSlider = new QSlider(Qt::Horizontal, widget);
+    timeResolutionSlider->setRange(0, 99);
+    layout->addRow(new QLabel(tr("Time resolution:")), timeResolutionSlider);
+
     scalesCheckBox = new QCheckBox(widget);
     scalesCheckBox->setCheckState(Qt::Checked);
     layout->addRow(new QLabel(tr("Scales:")), scalesCheckBox);

spectrogramcontrols.h

@@ -66,6 +66,7 @@ private slots:
     QSlider *zoomLevelSlider;
     QSlider *powerMaxSlider;
     QSlider *powerMinSlider;
+    QSlider *timeResolutionSlider;
     QCheckBox *cursorsCheckBox;
     QSpinBox *cursorSymbolsSpinBox;
     QLabel *rateLabel;

spectrogramplot.cpp

@@ -33,12 +33,13 @@
 
 SpectrogramPlot::SpectrogramPlot(std::shared_ptr<SampleSource<std::complex<float>>> src) : Plot(src), inputSource(src), fftSize(512), tuner(fftSize, this)
 {
-    setFFTSize(fftSize);
     zoomLevel = 1;
     powerMax = 0.0f;
     powerMin = -50.0f;
+    timeResolution = 0.0;
     sampleRate = 0;
     frequencyScaleEnabled = false;
+    setFFTSize(fftSize);
 
     for (int i = 0; i < 256; i++) {
         float p = (float)i / 256;
@@ -271,15 +272,46 @@ std::shared_ptr<AbstractSampleSource> SpectrogramPlot::output()
     return tunerTransform;
 }
 
+static float bessel(float x, int kmax = 5)
+{
+    int k;
+    float kfactorial = 1.0;
+    float half_x_to_k_pow = 1.0;
+    float term;
+    float result = 1.0;
+    for(k = 1; k < kmax; k++) {
+        half_x_to_k_pow *= x/2.0;
+        kfactorial *= k;
+        term = half_x_to_k_pow / kfactorial;
+        result += term * term;
+    }
+    return result;
+}
+
 void SpectrogramPlot::setFFTSize(int size)
 {
     float sizeScale = float(size) / float(fftSize);
+    float beta = 20;
+    float denominator = bessel(beta);
+
     fftSize = size;
     fft.reset(new FFT(fftSize));
 
     window.reset(new float[fftSize]);
-    for (int i = 0; i < fftSize; i++) {
-        window[i] = 0.5f * (1.0f - cos(Tau * i / (fftSize - 1)));
+    int zeroCount = (fftSize * timeResolution) / 100;
+    if ((zeroCount >= 0) && (zeroCount <= fftSize)) {
+        int windowSize = fftSize - zeroCount;
+        for (int i = 0; i < windowSize; i++) {
+            float term = float(2*i - windowSize + 1) / windowSize;
+            window[i] = bessel(beta * sqrt(1.0 - term * term)) / denominator;
+        }
+        for (int i = windowSize; i < fftSize; i++) {
+            window[i] = 0;
+        }
+    } else {
+        for(int i = 0; i < fftSize; i++) {
+            window[i] = 0;
+        }
     }
 
     setHeight(fftSize);
@@ -301,6 +333,14 @@ void SpectrogramPlot::setPowerMin(int power)
 {
     powerMin = power;
     pixmapCache.clear();
+    // HVI_REVIEW: Why no tunerMoved like in setPowerMax()?
+}
+
+void SpectrogramPlot::setTimeResolution(int resolution)
+{
+    timeResolution = resolution;
+    setFFTSize(fftSize);
+    invalidateEvent();
 }
 
 void SpectrogramPlot::setZoomLevel(int zoom)

spectrogramplot.h

@@ -54,6 +54,7 @@ public slots:
     void setPowerMax(int power);
     void setPowerMin(int power);
     void setZoomLevel(int zoom);
+    void setTimeResolution(int res);
     void tunerMoved();
 
 private:
@@ -71,6 +72,7 @@ public slots:
     int zoomLevel;
     float powerMax;
     float powerMin;
+    int timeResolution;
     off_t sampleRate;
     bool frequencyScaleEnabled;