Added frequency zoom

src/mainwindow.cpp

@@ -46,6 +46,7 @@ MainWindow::MainWindow()
     connect(dock, &SpectrogramControls::openFile, this, &MainWindow::openFile);
     connect(dock->sampleRate, static_cast<void (QLineEdit::*)(const QString&)>(&QLineEdit::textChanged), this, static_cast<void (MainWindow::*)(QString)>(&MainWindow::setSampleRate));
     connect(dock, static_cast<void (SpectrogramControls::*)(int, int)>(&SpectrogramControls::fftOrZoomChanged), plots, &PlotView::setFFTAndZoom);
+    connect(dock->freqZoomLevelSlider, &QSlider::valueChanged, plots, &PlotView::setFrequencyZoom);
     connect(dock->powerMaxSlider, &QSlider::valueChanged, plots, &PlotView::setPowerMax);
     connect(dock->powerMinSlider, &QSlider::valueChanged, plots, &PlotView::setPowerMin);
     connect(dock->cursorsCheckBox, &QCheckBox::stateChanged, plots, &PlotView::enableCursors);

src/plotview.cpp

@@ -472,6 +472,14 @@ void PlotView::setFFTAndZoom(int size, int zoom)
     updateView(true, samplesPerColumn() < oldSamplesPerColumn);
 }
 
+void PlotView::setFrequencyZoom(int zoomLevel)
+{
+    if (spectrogramPlot != nullptr)
+        spectrogramPlot->setFrequencyZoomLevel(zoomLevel);
+
+    updateView();
+}
+
 void PlotView::setPowerMin(int power)
 {
     powerMin = power;

src/plotview.h

@@ -52,6 +52,7 @@ public slots:
     void repaint();
     void setCursorSegments(int segments);
     void setFFTAndZoom(int fftSize, int zoomLevel);
+    void setFrequencyZoom(int zoomLevel);
     void setPowerMin(int power);
     void setPowerMax(int power);
 

src/spectrogramcontrols.cpp

@@ -55,7 +55,13 @@ SpectrogramControls::SpectrogramControls(const QString & title, QWidget * parent
     zoomLevelSlider->setRange(0, 10);
     zoomLevelSlider->setPageStep(1);
 
-    layout->addRow(new QLabel(tr("Zoom:")), zoomLevelSlider);
+    layout->addRow(new QLabel(tr("Time zoom:")), zoomLevelSlider);
+
+    freqZoomLevelSlider = new QSlider(Qt::Horizontal, widget);
+    freqZoomLevelSlider->setRange(1, 16);
+    freqZoomLevelSlider->setPageStep(1);
+
+    layout->addRow(new QLabel(tr("Freq zoom:")), freqZoomLevelSlider);
 
     powerMaxSlider = new QSlider(Qt::Horizontal, widget);
     powerMaxSlider->setRange(-140, 10);
@@ -107,6 +113,7 @@ SpectrogramControls::SpectrogramControls(const QString & title, QWidget * parent
 
     connect(fftSizeSlider, &QSlider::valueChanged, this, &SpectrogramControls::fftSizeChanged);
     connect(zoomLevelSlider, &QSlider::valueChanged, this, &SpectrogramControls::zoomLevelChanged);
+    connect(freqZoomLevelSlider, &QSlider::valueChanged, this, &SpectrogramControls::freqZoomLevelChanged);
     connect(fileOpenButton, &QPushButton::clicked, this, &SpectrogramControls::fileOpenButtonClicked);
     connect(cursorsCheckBox, &QCheckBox::stateChanged, this, &SpectrogramControls::cursorsStateChanged);
     connect(powerMinSlider, &QSlider::valueChanged, this, &SpectrogramControls::powerMinChanged);
@@ -146,6 +153,7 @@ void SpectrogramControls::setDefaults()
     powerMaxSlider->setValue(settings.value("PowerMax", 0).toInt());
     powerMinSlider->setValue(settings.value("PowerMin", -100).toInt());
     zoomLevelSlider->setValue(settings.value("ZoomLevel", 0).toInt());
+    freqZoomLevelSlider->setValue(settings.value("FreqZoomLevel", 1).toInt());
 }
 
 void SpectrogramControls::fftOrZoomChanged(void)
@@ -169,6 +177,12 @@ void SpectrogramControls::zoomLevelChanged(int value)
     fftOrZoomChanged();
 }
 
+void SpectrogramControls::freqZoomLevelChanged(int value)
+{
+    QSettings settings;
+    settings.setValue("FreqZoomLevel", value);
+}
+
 void SpectrogramControls::powerMinChanged(int value)
 {
     QSettings settings;

src/spectrogramcontrols.h

@@ -49,6 +49,7 @@ public slots:
 private slots:
     void fftSizeChanged(int value);
     void zoomLevelChanged(int value);
+    void freqZoomLevelChanged(int value);
     void powerMinChanged(int value);
     void powerMaxChanged(int value);
     void fileOpenButtonClicked();
@@ -65,6 +66,7 @@ private slots:
     QLineEdit *sampleRate;
     QSlider *fftSizeSlider;
     QSlider *zoomLevelSlider;
+    QSlider *freqZoomLevelSlider;
     QSlider *powerMaxSlider;
     QSlider *powerMinSlider;
     QCheckBox *cursorsCheckBox;

src/spectrogramplot.cpp

@@ -35,6 +35,7 @@
 
 SpectrogramPlot::SpectrogramPlot(std::shared_ptr<SampleSource<std::complex<float>>> src) : Plot(src), inputSource(src), fftSize(512), tuner(fftSize, this)
 {
+    freqZoomLevel = 1;
     setFFTSize(fftSize);
     zoomLevel = 1;
     powerMax = 0.0f;
@@ -229,15 +230,20 @@ void SpectrogramPlot::paintMid(QPainter &painter, QRect &rect, range_t<size_t> s
     size_t tileID = sampleRange.minimum - sampleOffset;
     int xoffset = sampleOffset / getStride();
 
+    // Source tiles hold the raw FFT bins (spectrogramHeight() rows); the
+    // destination is height() tall, so drawPixmap scales vertically by the
+    // frequency zoom level.
+    int srcHeight = spectrogramHeight();
+
     // Paint first (possibly partial) tile
-    painter.drawPixmap(QRect(rect.left(), rect.y(), linesPerTile() - xoffset, height()), *getPixmapTile(tileID), QRect(xoffset, 0, linesPerTile() - xoffset, height()));
+    painter.drawPixmap(QRect(rect.left(), rect.y(), linesPerTile() - xoffset, height()), *getPixmapTile(tileID), QRect(xoffset, 0, linesPerTile() - xoffset, srcHeight));
     tileID += getStride() * linesPerTile();
 
     // Paint remaining tiles
     for (int x = linesPerTile() - xoffset; x < rect.right(); x += linesPerTile()) {
         // TODO: don't draw past rect.right()
         // TODO: handle partial final tile
-        painter.drawPixmap(QRect(x, rect.y(), linesPerTile(), height()), *getPixmapTile(tileID), QRect(0, 0, linesPerTile(), height()));
+        painter.drawPixmap(QRect(x, rect.y(), linesPerTile(), height()), *getPixmapTile(tileID), QRect(0, 0, linesPerTile(), srcHeight));
         tileID += getStride() * linesPerTile();
     }
 }
@@ -329,13 +335,14 @@ int SpectrogramPlot::getStride()
 
 float SpectrogramPlot::getTunerPhaseInc()
 {
-    auto freq = 0.5f - tuner.centre() / (float)fftSize;
+    // Convert zoomed display size to FFT bins
+    auto freq = 0.5f - tuner.centre() / (freqZoomLevel * (float)fftSize);
     return freq * Tau;
 }
 
 std::vector<float> SpectrogramPlot::getTunerTaps()
 {
-    float cutoff = tuner.deviation() / (float)fftSize;
+    float cutoff = tuner.deviation() / (freqZoomLevel * (float)fftSize);
     float gain = pow(10.0f, powerMax / -10.0f);
     auto atten = 60.0f;
     auto len = estimate_req_filter_len(std::min(cutoff, 0.05f), atten);
@@ -381,11 +388,7 @@ void SpectrogramPlot::setFFTSize(int size)
         window[i] = 0.5f * (1.0f - cos(Tau * i / (fftSize - 1)));
     }
 
-    if (inputSource->realSignal()) {
-        setHeight(fftSize/2);
-    } else {
-        setHeight(fftSize);
-    }
+    setHeight(spectrogramHeight() * freqZoomLevel);
     auto dev = tuner.deviation();
     auto centre = tuner.centre();
     tuner.setHeight(height());
@@ -411,6 +414,29 @@ void SpectrogramPlot::setZoomLevel(int zoom)
     zoomLevel = zoom;
 }
 
+int SpectrogramPlot::spectrogramHeight()
+{
+    // Number of FFT bins displayed vertically, before applying freqZoomLevel
+    return inputSource->realSignal() ? fftSize / 2 : fftSize;
+}
+
+void SpectrogramPlot::setFrequencyZoomLevel(int zoom)
+{
+    // Rescale the tuner so it stays over the same frequency after zooming
+    float scale = (float)zoom / (float)freqZoomLevel;
+    auto dev = tuner.deviation();
+    auto centre = tuner.centre();
+
+    freqZoomLevel = zoom;
+    setHeight(spectrogramHeight() * freqZoomLevel);
+
+    tuner.setHeight(height());
+    tuner.setDeviation(dev * scale);
+    tuner.setCentre(centre * scale);
+
+    emit repaint();
+}
+
 void SpectrogramPlot::setSampleRate(double rate)
 {
     sampleRate = rate;

src/spectrogramplot.h

@@ -82,6 +82,7 @@ public slots:
     void setPowerMax(int power);
     void setPowerMin(int power);
     void setZoomLevel(int zoom);
+    void setFrequencyZoomLevel(int zoom);
     void tunerMoved();
 
 private:
@@ -98,6 +99,7 @@ public slots:
 
     int fftSize;
     int zoomLevel;
+    int freqZoomLevel;
     float powerMax;
     float powerMin;
     double sampleRate;
@@ -111,6 +113,7 @@ public slots:
     float* getFFTTile(size_t tile);
     void getLine(float *dest, size_t sample);
     int getStride();
+    int spectrogramHeight();
     float getTunerPhaseInc();
     std::vector<float> getTunerTaps();
     int linesPerTile();