Adds Frequency Offset option to adjust the vertical freq to captured frequency center

inputsource.cpp

@@ -249,6 +249,17 @@ double InputSource::rate()
     return sampleRate;
 }
 
+void InputSource::setFrequencyOffset(double offset)
+{
+    frequencyOffset = offset;
+    invalidate();
+}
+
+double InputSource::offset()
+{
+    return frequencyOffset;
+}
+
 std::unique_ptr<std::complex<float>[]> InputSource::getSamples(size_t start, size_t length)
 {
     if (inputFile == nullptr)

inputsource.h

@@ -36,6 +36,7 @@ class InputSource : public SampleSource<std::complex<float>>
     QFile *inputFile = nullptr;
     size_t sampleCount = 0;
     double sampleRate = 0.0;
+    double frequencyOffset = 0.0;
     uchar *mmapData = nullptr;
     std::unique_ptr<SampleAdapter> sampleAdapter;
     std::string _fmt;
@@ -51,8 +52,10 @@ class InputSource : public SampleSource<std::complex<float>>
         return sampleCount;
     };
     void setSampleRate(double rate);
+    void setFrequencyOffset(double rate);
     void setFormat(std::string fmt);
     double rate();
+    double offset();
     bool realSignal() {
         return _realSignal;
     };

mainwindow.cpp

@@ -44,6 +44,7 @@ MainWindow::MainWindow()
     // Connect dock inputs
     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->frequencyOffset, static_cast<void (QLineEdit::*)(const QString&)>(&QLineEdit::textChanged), this, static_cast<void (MainWindow::*)(QString)>(&MainWindow::setFrequencyOffset));
     connect(dock, static_cast<void (SpectrogramControls::*)(int, int)>(&SpectrogramControls::fftOrZoomChanged), plots, &PlotView::setFFTAndZoom);
     connect(dock->powerMaxSlider, &QSlider::valueChanged, plots, &PlotView::setPowerMax);
     connect(dock->powerMinSlider, &QSlider::valueChanged, plots, &PlotView::setPowerMin);
@@ -107,11 +108,27 @@ void MainWindow::setSampleRate(QString rate)
     settings.setValue("SampleRate", sampleRate);
 }
 
+void MainWindow::setFrequencyOffset(QString rate)
+{
+    auto frequencyOffset = rate.toDouble();
+    input->setFrequencyOffset(frequencyOffset);
+    plots->setFrequencyOffset(frequencyOffset);
+
+    // Save the frequency offset in settings as we're likely to be opening the same file across multiple runs
+    QSettings settings;
+    settings.setValue("FrequencyOffset", frequencyOffset);
+}
+
 void MainWindow::setSampleRate(double rate)
 {
     dock->sampleRate->setText(QString::number(rate));
 }
 
+void MainWindow::setFrequencyOffset(double rate)
+{
+    dock->frequencyOffset->setText(QString::number(rate));
+}
+
 void MainWindow::setFormat(QString fmt)
 {
     input->setFormat(fmt.toUtf8().constData());

mainwindow.h

@@ -36,6 +36,8 @@ public slots:
     void openFile(QString fileName);
     void setSampleRate(QString rate);
     void setSampleRate(double rate);
+    void setFrequencyOffset(QString rate);
+    void setFrequencyOffset(double rate);
     void setFormat(QString fmt);
 
 private:

plotview.cpp

@@ -573,6 +573,16 @@ void PlotView::setSampleRate(double rate)
     emitTimeSelection();
 }
 
+void PlotView::setFrequencyOffset(double rate)
+{
+    frequencyOffset = rate;
+
+    if (spectrogramPlot != nullptr)
+        spectrogramPlot->setFrequencyOffset(rate);
+
+    emitTimeSelection();
+}
+
 void PlotView::enableScales(bool enabled)
 {
     timeScaleEnabled = enabled;

plotview.h

@@ -36,6 +36,7 @@ class PlotView : public QGraphicsView, Subscriber
 public:
     PlotView(InputSource *input);
     void setSampleRate(double rate);
+    void setFrequencyOffset(double rate);
 
 signals:
     void timeSelectionChanged(float time);
@@ -76,6 +77,7 @@ public slots:
     int powerMax;
     bool cursorsEnabled;
     double sampleRate = 0.0;
+    double frequencyOffset = 0.0;
     bool timeScaleEnabled;
     int scrollZoomStepsAccumulated = 0;
 

spectrogramcontrols.cpp

@@ -41,6 +41,12 @@ SpectrogramControls::SpectrogramControls(const QString & title, QWidget * parent
     sampleRate->setValidator(double_validator);
     layout->addRow(new QLabel(tr("Sample rate:")), sampleRate);
 
+    frequencyOffset = new QLineEdit();
+    auto freq_validator = new QDoubleValidator(this);
+    freq_validator->setBottom(0.0);
+    frequencyOffset->setValidator(freq_validator);
+    layout->addRow(new QLabel(tr("Frequency offset:")), frequencyOffset);
+
     // Spectrogram settings
     layout->addRow(new QLabel()); // TODO: find a better way to add an empty row?
     layout->addRow(new QLabel(tr("<b>Spectrogram</b>")));
@@ -130,6 +136,10 @@ void SpectrogramControls::setDefaults()
     QSettings settings;
     int savedSampleRate = settings.value("SampleRate", 8000000).toInt();
     sampleRate->setText(QString::number(savedSampleRate));
+
+    int savedFrequencyOffset = settings.value("FrequencyOffset", 0).toInt();
+    frequencyOffset->setText(QString::number(savedFrequencyOffset));
+
     fftSizeSlider->setValue(settings.value("FFTSize", 9).toInt());
     powerMaxSlider->setValue(settings.value("PowerMax", 0).toInt());
     powerMinSlider->setValue(settings.value("PowerMin", -100).toInt());

spectrogramcontrols.h

@@ -62,6 +62,7 @@ private slots:
 public:
     QPushButton *fileOpenButton;
     QLineEdit *sampleRate;
+    QLineEdit *frequencyOffset;
     QSlider *fftSizeSlider;
     QSlider *zoomLevelSlider;
     QSlider *powerMaxSlider;

spectrogramplot.cpp

@@ -101,33 +101,42 @@ void SpectrogramPlot::paintFrequencyScale(QPainter &painter, QRect &rect)
         int tickny = plotHeight / 2 + tick / bwPerPixel + y;
 
         if (!inputSource->realSignal())
-            painter.drawLine(0, tickny, 30, tickny);
-        painter.drawLine(0, tickpy, 30, tickpy);
+            painter.drawLine(0, tickny, 30, tickny); // draws neg lines
+        painter.drawLine(0, tickpy, 30, tickpy); // draws pos lines
 
         if (tick != 0) {
             char buf[128];
 
-            if (bwPerTick % 1000000 == 0) {
-                snprintf(buf, sizeof(buf), "-%d MHz", (int)tick / 1000000);
+            if (!inputSource->realSignal()) {
+                if (bwPerTick % 1000000000 == 0) {
+                  snprintf(buf, sizeof(buf), "%d MHz", ((int)frequencyOffset - (int)tick) / 1000000000);
+                } else if (bwPerTick % 1000000 == 0) {
+                  snprintf(buf, sizeof(buf), "%d MHz", ((int)frequencyOffset - (int)tick) / 1000000);
+                } else if(bwPerTick % 1000 == 0) {
+                  snprintf(buf, sizeof(buf), "%d kHz", ((int)frequencyOffset - (int)tick) / 1000);
+                } else {
+                  snprintf(buf, sizeof(buf), "%d Hz", (int)frequencyOffset - tick);
+                }
+              painter.drawText(5, tickny - 5, buf); // draws neg text
+            }
+
+            if (bwPerTick % 1000000000 == 0) {
+              snprintf(buf, sizeof(buf), "%d MHz", ((int)frequencyOffset + (int)tick) / 1000000000);
+            } else if (bwPerTick % 1000000 == 0) {
+              snprintf(buf, sizeof(buf), "%d MHz", ((int)frequencyOffset + (int)tick) / 1000000);
             } else if(bwPerTick % 1000 == 0) {
-                snprintf(buf, sizeof(buf), "-%d kHz", tick / 1000);
+              snprintf(buf, sizeof(buf), "%d kHz", ((int)frequencyOffset + (int)tick) / 1000);
             } else {
-                snprintf(buf, sizeof(buf), "-%d Hz", tick);
+              snprintf(buf, sizeof(buf), "%d Hz", (int)frequencyOffset + tick);
             }
-
-            if (!inputSource->realSignal())
-                painter.drawText(5, tickny - 5, buf);
-
-            buf[0] = ' ';
-            painter.drawText(5, tickpy + 15, buf);
+             painter.drawText(5, tickpy + 15, buf); // draws pos text
         }
 
         tick += bwPerTick;
     }
 
     // Draw small ticks
     bwPerTick /= 10;
-
     if (bwPerTick >= 1 ) {
         tick = 0;
         while (tick <= sampleRate / 2) {
@@ -329,6 +338,11 @@ void SpectrogramPlot::setSampleRate(size_t rate)
     sampleRate = rate;
 }
 
+void SpectrogramPlot::setFrequencyOffset(size_t rate)
+{
+    frequencyOffset = rate;
+}
+
 void SpectrogramPlot::enableScales(bool enabled)
 {
    frequencyScaleEnabled = enabled;

spectrogramplot.h

@@ -46,6 +46,7 @@ class SpectrogramPlot : public Plot
     bool mouseEvent(QEvent::Type type, QMouseEvent event) override;
     std::shared_ptr<SampleSource<std::complex<float>>> input() { return inputSource; };
     void setSampleRate(size_t sampleRate);
+    void setFrequencyOffset(size_t frequencyOffset);
     bool tunerEnabled();
     void enableScales(bool enabled);
 
@@ -72,6 +73,7 @@ public slots:
     float powerMax;
     float powerMin;
     size_t sampleRate;
+    size_t frequencyOffset;
     bool frequencyScaleEnabled;
 
     Tuner tuner;