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usrp/fft.c: made window function user-selectable, added hann, blackman, rect

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- fft.c (window, usage, main): added command line option -w window to
  select window function
- fft.c (window_rectangle, window_hann, window_hamming, window_blackman):
  increased choice of window functions
This commit is contained in:
Werner Almesberger 2011-03-03 16:00:28 -03:00
parent fff1e1ed2f
commit 95a9e12e2e
1 changed files with 41 additions and 4 deletions
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45
usrp/fft.c
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@ -1,6 +1,7 @@
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <math.h>
#include <sys/types.h>
@ -12,12 +13,33 @@
static int alg = 0;
static double window(int i, int n)
static double window_rectangle(int i, int n)
{
return 1;
}
static double window_hann(int i, int n)
{
return 0.5-0.5*cos(M_PI*2*i/(n-1));
}
static double window_hamming(int i, int n)
{
return 0.54-0.46*cos(M_PI*2*i/(n-1));
}
static double window_blackman(int i, int n)
{
return 0.42-0.5*cos(M_PI*2*i/(n-1))+0.08*cos(M_PI*4*i/(n-1));
}
static double (*window)(int i, int n) = window_rectangle;
static void fft_complex(int n, const float *re, const float *im, double *res)
{
fftw_complex *in, *out;
@ -30,6 +52,7 @@ static void fft_complex(int n, const float *re, const float *im, double *res)
for (i = 0; i != n; i++) {
double w = window(i, n);
in[i][0] = re[i]*w;
in[i][1] = im[i]*w;
}
@ -165,13 +188,15 @@ static void do_fft(int skip, int dump, int low, int high, double threshold)
static void usage(const char *name)
{
fprintf(stderr,
"usage: %s [-s skip] low high [threshold]\n"
" %s [-s skip] -d\n\n"
"usage: %s [-s skip] [-w window] low high [threshold]\n"
" %s [-s skip] [-w window] -d\n\n"
" threshold only use frequency bins with at least this power, in - dB.\n"
" E.g., a threshold value of 60 would be -60 dB. (default: %d\n"
" dB)\n"
" -d dump frequency-domain \n"
" -s skip skip this number of samples from the beginning (default: 0)\n"
" -w window use the specified window function. Available: blackman, hann,\n"
" hamming, rectangle. Default is rectangle.\n"
, name, name, -DEFAULT_THRESHOLD);
exit(1);
}
@ -184,7 +209,7 @@ int main(int argc, char **argv)
double threshold = DEFAULT_THRESHOLD;
int c;
while ((c = getopt(argc, argv, "a:ds:")) != EOF)
while ((c = getopt(argc, argv, "a:ds:w:")) != EOF)
switch (c) {
case 'a':
alg = atoi(optarg);
@ -195,6 +220,18 @@ int main(int argc, char **argv)
case 's':
skip = atoi(optarg);
break;
case 'w':
if (!strcmp(optarg, "blackman"))
window = window_blackman;
else if (!strcmp(optarg, "hann"))
window = window_hann;
else if (!strcmp(optarg, "hamming"))
window = window_hamming;
else if (!strcmp(optarg, "rectangle"))
window = window_rectangle;
else
usage(*argv);
break;
default:
usage(*argv);
}