具有复杂输出的C/C++ Goertzel算法还是magnitude+phase？

Question

有人知道我可以从哪里获得代码或库来执行复杂输出的Goertzel算法吗？(或者其他任何1-bin-DFT算法？)

Answer 1

下面是几年前我写的代码。你可以随意使用它，只要有适当的属性。

goertzelfilter.h

/* goertzelfilter.h
*/

#ifndef GOERTZELFILTER_H_
#define GOERTZELFILTER_H_

#include <complex.h>

typedef struct goertzelfilterstruct {
  double coeff ;
  double sine ;
  double cosine ;
} GoertzelFilter;

GoertzelFilter goertzelSetup( double normalizedfreq );

double complex goertzelFilterC( double *sample, int nsamples, GoertzelFilter *g );

#endif

goerzelfilter.c

/* goertzelfilter.c
*/

#include <math.h>
#include <stdlib.h>
#include <complex.h>

#include "goertzelfilter.h"

GoertzelFilter goertzelSetup( double normalizedfreq )
{
  double w = 2*M_PI*normalizedfreq;
  double wr, wi;

  GoertzelFilter g;

  wr = cos(w);
  wi = sin(w);
  g.coeff = 2 * wr;
  g.cosine = wr;
  g.sine = wi;

  return g;
}

double complex goertzelFilterC( double *samples, int nsamples, GoertzelFilter *g )
{
  double sprev = 0.0;
  double sprev2 = 0.0;
  double s, imag, real;
  int n;

  for (n=0; n<nsamples; n++ ) {
    s = samples[n] + g->coeff * sprev - sprev2;
    sprev2 = sprev;
    sprev = s;
  }

  real = sprev*g->cosine - sprev2;
  imag = -sprev*g->sine;

  return real + I*imag;
}

作为测试，你可以试试这个，

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <complex.h>

#include "goertzelfilter.h"

#define LEN(a) (sizeof(a)/sizeof(a[0]) )

int main() {

  // This will hold our input and output data
  double data[1024] = { 0. };
  double complex filtered[1024] = { 0. };

  // This will hold the filter constants
  GoertzelFilter g = { 0. };

  int n;
  int nwindow = 16;

  double f = 4./LEN(data) ;

  // Generate data with noise
  for ( n = 0 ; n < LEN(data) ; n++ ) {
    data[n] = sin( n * (2.*M_PI) * f ) + 0.5*((float)rand()/RAND_MAX - 0.5);
  }

  // Set up the filter constants, note that we choose a frequency
  g = goertzelSetup( f );

  // Filter the data using a sliding window
  for( n = 0 ; n < LEN(data)-nwindow ; n++ ) {
    filtered[n+nwindow/2]  = goertzelFilterC( &data[n], nwindow, &g )/nwindow;
  }

  // Print the real Valued Data (1st column) and complex valued Goertzel output
  for( n = 0 ; n < LEN(data); n++ ) {
    printf( "%g %g %g\n", data[n], creal(filtered[n]), cimag(filtered[n]) );
  }

}

下面的图表显示了测试代码的输入和输出：

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