Locate and position the current Audacity source code, and clear a variety of old junk out of the way into junk-branches

src/FFT.h

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+/**********************************************************************
+
+  FFT.h
+
+  Dominic Mazzoni
+
+  September 2000
+
+  This file contains a few FFT routines, including a real-FFT
+  routine that is almost twice as fast as a normal complex FFT,
+  and a power spectrum routine which is more convenient when
+  you know you don't care about phase information.  It now also
+  contains a few basic windowing functions.
+
+  Some of this code was based on a free implementation of an FFT
+  by Don Cross, available on the web at:
+
+    http://www.intersrv.com/~dcross/fft.html
+
+  The basic algorithm for his code was based on Numerical Recipes
+  in Fortran.  I optimized his code further by reducing array
+  accesses, caching the bit reversal table, and eliminating
+  float-to-double conversions, and I added the routines to
+  calculate a real FFT and a real power spectrum.
+
+  Note: all of these routines use single-precision floats.
+  I have found that in practice, floats work well until you
+  get above 8192 samples.  If you need to do a larger FFT,
+  you need to use doubles.
+
+**********************************************************************/
+/*
+  Salvo Ventura - November 2006
+  Added more window functions:
+    * 4: Blackman
+    * 5: Blackman-Harris
+    * 6: Welch
+    * 7: Gaussian(a=2.5)
+    * 8: Gaussian(a=3.5)
+    * 9: Gaussian(a=4.5)
+*/
+
+#ifndef M_PI
+#define	M_PI		3.14159265358979323846  /* pi */
+#endif
+
+/*
+ * This is the function you will use the most often.
+ * Given an array of floats, this will compute the power
+ * spectrum by doing a Real FFT and then computing the
+ * sum of the squares of the real and imaginary parts.
+ * Note that the output array is half the length of the
+ * input array, and that NumSamples must be a power of two.
+ */
+
+void PowerSpectrum(int NumSamples, float *In, float *Out);
+
+/*
+ * Computes an FFT when the input data is real but you still
+ * want complex data as output.  The output arrays are the
+ * same length as the input, but will be conjugate-symmetric
+ * NumSamples must be a power of two.
+ */
+
+void RealFFT(int NumSamples,
+             float *RealIn, float *RealOut, float *ImagOut);
+
+/*
+ * Computes an Inverse FFT when the input data is conjugate symmetric
+ * so the output is purely real.  NumSamples must be a power of
+ * two.
+ * Requires: EXPERIMENTAL_USE_REALFFTF
+ */
+#include "Experimental.h"
+#ifdef EXPERIMENTAL_USE_REALFFTF
+void InverseRealFFT(int NumSamples,
+             float *RealIn, float *ImagIn, float *RealOut);
+#endif
+
+/*
+ * Computes a FFT of complex input and returns complex output.
+ * Currently this is the only function here that supports the
+ * inverse transform as well.
+ */
+
+void FFT(int NumSamples,
+         bool InverseTransform,
+         float *RealIn, float *ImagIn, float *RealOut, float *ImagOut);
+
+/*
+ * Applies a windowing function to the data in place
+ *
+ * 0: Rectangular (no window)
+ * 1: Bartlett    (triangular)
+ * 2: Hamming
+ * 3: Hanning
+ * 4: Blackman
+ * 5: Blackman-Harris
+ * 6: Welch
+ * 7: Gaussian(a=2.5)
+ * 8: Gaussian(a=3.5)
+ * 9: Gaussian(a=4.5)
+ */
+
+void WindowFunc(int whichFunction, int NumSamples, float *data);
+
+/*
+ * Returns the name of the windowing function (for UI display)
+ */
+
+const wxChar *WindowFuncName(int whichFunction);
+
+/*
+ * Returns the number of windowing functions supported
+ */
+
+int NumWindowFuncs();
+
+void DeinitFFT();
+
+// Indentation settings for Vim and Emacs and unique identifier for Arch, a
+// version control system. Please do not modify past this point.
+//
+// Local Variables:
+// c-basic-offset: 3