Merge pull request #1856 from das-Iro/fix-fft-overlap

Fix fft overlap
f4exb · Oct 23, 2023 · c9a4d54 · c9a4d54
2 parents dc7dd0c + 277b2b4
commit c9a4d54
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Showing 3 changed files with 14 additions and 16 deletions.
diff --git a/sdrbase/dsp/spectrumvis.cpp b/sdrbase/dsp/spectrumvis.cpp
@@ -327,7 +327,7 @@ void SpectrumVis::feed(const ComplexVector::const_iterator& cbegin, const Comple
 	while (begin < end)
 	{
 		std::size_t todo = end - begin;
-		std::size_t samplesNeeded = m_refillSize - m_fftBufferFill;
+		std::size_t samplesNeeded = m_settings.m_fftSize - m_fftBufferFill;
 
 		if (todo >= samplesNeeded)
 		{
@@ -338,6 +338,7 @@ void SpectrumVis::feed(const ComplexVector::const_iterator& cbegin, const Comple
             processFFT(positiveOnly);
 
 			// advance buffer respecting the fft overlap factor
+			// undefined bahavior if the memory regions overlap, valid code for 50% overlap
 			std::copy(m_fftBuffer.begin() + m_refillSize, m_fftBuffer.end(), m_fftBuffer.begin());
 
 			// start over
@@ -377,7 +378,7 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 	while (begin < end)
 	{
 		std::size_t todo = end - begin;
-		std::size_t samplesNeeded = m_refillSize - m_fftBufferFill;
+		std::size_t samplesNeeded = m_settings.m_fftSize - m_fftBufferFill;
 
 		if (todo >= samplesNeeded)
 		{
@@ -391,6 +392,7 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
             processFFT(positiveOnly);
 
 			// advance buffer respecting the fft overlap factor
+			// undefined bahavior if the memory regions overlap, valid code for 50% overlap
 			std::copy(m_fftBuffer.begin() + m_refillSize, m_fftBuffer.end(), m_fftBuffer.begin());
 
 			// start over
@@ -890,8 +892,8 @@ void SpectrumVis::applySettings(const SpectrumSettings& settings, bool force)
     if ((fftSize != m_settings.m_fftSize)
      || (settings.m_fftOverlap != m_settings.m_fftOverlap) || force)
     {
-        m_overlapSize = settings.m_fftOverlap < 0 ? 0 :
-            settings.m_fftOverlap < fftSize/2 ? settings.m_fftOverlap : (fftSize/2) - 1;
+		m_overlapSize = settings.m_fftOverlap < 0 ? 0 :
+			settings.m_fftOverlap < fftSize ? settings.m_fftOverlap : (fftSize - 1);
         m_refillSize = fftSize - m_overlapSize;
         m_fftBufferFill = m_overlapSize;
     }

diff --git a/sdrgui/gui/glspectrumgui.cpp b/sdrgui/gui/glspectrumgui.cpp
@@ -864,8 +864,7 @@ void GLSpectrumGUI::setAveragingToolitp()
     {
         QString s;
         int averagingIndex = m_settings.m_averagingMode == SpectrumSettings::AvgModeNone ? 0 : m_settings.m_averagingIndex;
-        float halfSize = m_settings.m_fftSize / 2;
-        float overlapFactor = (halfSize - m_settings.m_fftOverlap) / halfSize;
+        float overlapFactor = (m_settings.m_fftSize - m_settings.m_fftOverlap) / m_settings.m_fftSize;
         float averagingTime = (m_settings.m_fftSize * (SpectrumSettings::getAveragingValue(averagingIndex, m_settings.m_averagingMode) == 0 ?
             1 :
             SpectrumSettings::getAveragingValue(averagingIndex, m_settings.m_averagingMode))) / (float) m_glSpectrum->getSampleRate();
@@ -905,11 +904,10 @@ void GLSpectrumGUI::setFFTSize(int log2FFTSize)
 
 void GLSpectrumGUI::setMaximumOverlap()
 {
-    int halfSize = m_settings.m_fftSize/2;
-    ui->fftOverlap->setMaximum((halfSize)-1);
+    ui->fftOverlap->setMaximum(m_settings.m_fftSize -1);
     int value = ui->fftOverlap->value();
     ui->fftOverlap->setValue(value);
-    ui->fftOverlap->setToolTip(tr("FFT overlap %1 %").arg((value/(float)halfSize)*100.0f));
+    ui->fftOverlap->setToolTip(tr("FFT overlap %1 %").arg((value/(float)m_settings.m_fftSize)*100.0f));
 
     if (m_glSpectrum) {
         m_glSpectrum->setFFTOverlap(value);

diff --git a/sdrgui/gui/glspectrumview.cpp b/sdrgui/gui/glspectrumview.cpp
@@ -2733,10 +2733,9 @@ void GLSpectrumView::applyChanges()
         if (m_sampleRate > 0)
         {
             float timeScaleDiv = ((float)m_sampleRate / (float)m_timingRate);
-            float halfFFTSize = m_fftSize / 2;
 
-            if (halfFFTSize > m_fftOverlap) {
-                timeScaleDiv *= halfFFTSize / (halfFFTSize - m_fftOverlap);
+            if (m_fftSize > m_fftOverlap) {
+                timeScaleDiv *= m_fftSize / (m_fftSize - m_fftOverlap);
             }
 
             if (!m_invertedWaterfall) {
@@ -2827,10 +2826,9 @@ void GLSpectrumView::applyChanges()
         if (m_sampleRate > 0)
         {
             float timeScaleDiv = ((float)m_sampleRate / (float)m_timingRate);
-            float halfFFTSize = m_fftSize / 2;
 
-            if (halfFFTSize > m_fftOverlap) {
-                timeScaleDiv *= halfFFTSize / (halfFFTSize - m_fftOverlap);
+            if (m_fftSize > m_fftOverlap) {
+                timeScaleDiv *= m_fftSize / (m_fftSize - m_fftOverlap);
             }
 
             if (!m_invertedWaterfall) {
@@ -4454,7 +4452,7 @@ void GLSpectrumView::timeZoom(bool zoomInElseOut)
         return;
     }
 
-    if (zoomInElseOut && (m_fftOverlap == m_fftSize/2 - 1)) {
+	if (zoomInElseOut && (m_fftOverlap == m_fftSize - 1)) {
         return;
     }