www.pudn.com > fftjd.rar > FOURIER.H

/*============================================================================ 
 
       fourier.h  -  Don Cross  
 
       http://www.intersrv.com/~dcross/fft.html 
 
       Contains definitions for doing Fourier transforms 
       and inverse Fourier transforms. 
 
============================================================================*/ 
 
#ifdef __cplusplus 
extern "C" { 
#endif 
 
/* 
**   fft() computes the Fourier transform or inverse transform 
**   of the complex inputs to produce the complex outputs. 
**   The number of samples must be a power of two to do the 
**   recursive decomposition of the FFT algorithm. 
**   See Chapter 12 of "Numerical Recipes in FORTRAN" by 
**   Press, Teukolsky, Vetterling, and Flannery, 
**   Cambridge University Press. 
** 
**   Notes:  If you pass ImaginaryIn = NULL, this function will "pretend" 
**           that it is an array of all zeroes.  This is convenient for 
**           transforming digital samples of real number data without 
**           wasting memory. 
*/ 
 
void fft_double ( 
    unsigned  NumSamples,          /* must be a power of 2 */ 
    int       InverseTransform,    /* 0=forward FFT, 1=inverse FFT */ 
    double   *RealIn,              /* array of input's real samples */ 
    double   *ImaginaryIn,         /* array of input's imag samples */ 
    double   *RealOut,             /* array of output's reals */ 
    double   *ImaginaryOut );      /* array of output's imaginaries */ 
 
 
void fft_float ( 
    unsigned  NumSamples,          /* must be a power of 2 */ 
    int       InverseTransform,    /* 0=forward FFT, 1=inverse FFT */ 
    float    *RealIn,              /* array of input's real samples */ 
    float    *ImaginaryIn,         /* array of input's imag samples */ 
    float    *RealOut,             /* array of output's reals */ 
    float    *ImaginaryOut );      /* array of output's imaginaries */ 
 
 
int IsPowerOfTwo ( unsigned x ); 
unsigned NumberOfBitsNeeded ( unsigned PowerOfTwo ); 
unsigned ReverseBits ( unsigned index, unsigned NumBits ); 
 
/* 
**   The following function returns an "abstract frequency" of a 
**   given index into a buffer with a given number of frequency samples. 
**   Multiply return value by sampling rate to get frequency expressed in Hz. 
*/ 
double Index_to_frequency ( unsigned NumSamples, unsigned Index ); 
 
#ifdef __cplusplus 
} 
#endif 
 
 
/*--- end of file fourier.h ---*/