ref: 21ae07faf06daee0ced8e6f8f9b8ae8dba006b96
dir: /src/FFT.h/
/*
* FFT.h
*
* 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.
*
* This file is now part of SoX, and is 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 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,
* Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
*/
/*
* 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 = 0, /* no window */
BARTLETT = 1, /* triangular */
HAMMING = 2,
HANNING = 3} windowfunc_t;
void WindowFunc(windowfunc_t whichFunction, int NumSamples, float *data);