音频处理：FFT与功率谱计算详解

#include "StdAfx.h"   
#include ".\waveconvertor.h"   
   
//////////////////////////////////////////////////////////////////////////   
// class CWaveConvertor   
//   
// 功能：  实现裸音频数据的FFT变换   
// 创建人： 陈文凯 (chwkai@gmail.com)   
// 创建日期:2005年5月19日   
// 修改人：   
// 修改日期：   
// 版本   
   
/* Pjotr '87.  */   
// As best as I can determine this is in the public domain. No license was found   
// withit what so ever. The author is listed as:   
// Peter Valkenburg (valke@cs.vu.nl).   
//   
// If there is some disagreement then contact Bruce Forsberg (forsberg@tns.net)   
#include <math.h>   
   
#define pi   3.1415926535897932384626434   
   
#define     c_re(c)     ((c).re)   
#define     c_im(c)     ((c).im)   
   
/* C_add_mul adds product of c1 and c2 to c.  */   
#define c_add_mul(c, c1, c2)    { COMPLEX C1, C2; C1 = (c1); C2 = (c2); \   
    c_re (c) += C1.re * C2.re - C1.im * C2.im; \   
    c_im (c) += C1.re * C2.im + C1.im * C2.re; }   

   
/* C_conj substitutes c by its complex conjugate. */   
#define c_conj(c)       { c_im (c) = -c_im (c); }   
   
/* C_realdiv divides complex c by real.  */   
#define c_realdiv(c, real)  { c_re (c) /= (real); c_im (c) /= (real); }   
   
/*  
* W gives the (already computed) Wn ^ k (= e ^ (2pi * i * k / n)).  
* Notice that the powerseries of Wn has period Nfactors.  
*/   
#define W(n, k)     (W_factors [((k) * (Nfactors / (n))) % Nfactors])   
   
   
   
/*! \brief Constructor.  
*/   
aflibFFT::aflibFFT()   
{   
    Nfactors = 0;   
    W_factors = NULL;   
}   
   
   
/*! \brief Destructor.  
*/   
aflibFFT::~aflibFFT()   
{   
    if (W_factors != NULL)   
    delete W_factors;