#define FFTTOOLS_H
#include <QVector>
+#include <QHash>
+#include "kiss_fft/tools/kiss_fftr.h"
class FFTTools
{
public:
FFTTools();
+ ~FFTTools();
enum WindowType { Window_Rect, Window_Triangle, Window_Hamming };
default is 0)
* Nothing for the Hamming window
*/
- static const QVector<float> window(WindowType windowType, const int size, const float param);
+ static const QVector<float> window(const WindowType windowType, const int size, const float param = 0);
+
+ static const QString windowSignature(const WindowType windowType, const int size, const float param = 0);
+
+ /** Returns a signature for a kiss_fft configuration
+ used as a hash in the cache */
+ static const QString cfgSignature(const int size);
+
+ /** Calculates the Fourier Tranformation of the input audio frame.
+ The resulting values will be given in relative dezibel: The maximum power is 0 dB, lower powers have
+ negative dB values.
+ * audioFrame: Interleaved format with #numChannels channels
+ * freqSpectrum: Array pointer to write the data into
+ * windowSize must be divisible by 2,
+ * freqSpectrum has to be of size windowSize/2
+ For windowType and param see the FFTTools::window() function above.
+ */
+ void fftNormalized(const QVector<int16_t> audioFrame, const uint channel, const uint numChannels, float *freqSpectrum,
+ const WindowType windowType, const uint windowSize, const float param = 0);
+
+
+ /** This is linear interpolation with the special property that it preserves peaks, which is required
+ for e.g. showing correct Decibel values (where the peak values are of interest because of clipping which
+ may occur for too strong frequencies; The lower values are smeared by the window function anyway).
+ Consider f = {0, 100, 0}
+ x = {0.5, 1.5}: With default linear interpolation x0 and x1 would both be mapped to 50.
+ This function maps x1 (the first position after the peak) to 100.
+
+ @param in The source vector containing the data
+ @param targetSize Number of interpolation nodes between ...
+ @param left the left array index in the in-vector and ...
+ @param right the right array index (both inclusive).
+ @param fill If right lies outside of the array bounds (which is perfectly fine here) then this value
+ will be used for filling the missing information.
+ */
+ static const QVector<float> interpolatePeakPreserving(const QVector<float> in, const uint targetSize, uint left = 0, uint right = 0, float fill = 0.0);
+
+private:
+ QHash<QString, kiss_fftr_cfg> m_fftCfgs; // FFT cfg cache
+ QHash<QString, QVector<float> > m_windowFunctions; // Window function cache
};