ref: c2749992b232e8459354dd4763155b1ff3e0d228
dir: /src/FFT.h/
/* libSoX FFT funtions copyright Ian Turner and others.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at
* your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*
* Based on FFT.h from Audacity, with the following permission from
* its author, Dominic Mazzoni (in particular, relicensing the code
* for use in SoX):
*
* I hereby license you under the LGPL all of the code in FFT.cpp
* from any version of Audacity, with the exception of the windowing
* function code, as I wrote the rest of the line [sic] that appears
* in any version of Audacity (or they are derived from Don Cross or
* NR, which is okay).
*
* -- Dominic Mazzoni <dominic@audacityteam.org>, 18th November 2006
*
* As regards the windowing function, WindowFunc, Dominic granted a
* license to it too, writing on the same day:
*
* OK, we're good. That's the original version that I wrote, before
* others contributed.
*
* 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 [no longer, it seems]
*
* The basic algorithm for his code was based on Numerical Recipes
* in Fortran.
*/
/* aliases */
#define gFFTBitTable lsx_gFFTBitTable
#define MaxFastBits lsx_MaxFastBits
#define FFT lsx_FFT
#define RealFFT lsx_RealFFT
#define PowerSpectrum lsx_PowerSpectrum
#define WindowFunc lsx_WindowFunc
/*
* 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(unsigned NumSamples, const 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 half
* the length of the input, and NumSamples must be a power of
* two.
*/
void RealFFT(unsigned NumSamples,
const float *RealIn, float *RealOut, float *ImagOut);
/*
* 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(unsigned NumSamples,
int InverseTransform,
const float *RealIn, float *ImagIn, float *RealOut, float *ImagOut);
/*
* Applies a windowing function to the data in place
*/
typedef enum {RECTANGULAR, /* no window */
BARTLETT, /* triangular */
HAMMING,
HANNING} windowfunc_t;
void WindowFunc(windowfunc_t whichFunction, int NumSamples, float *data);