112 lines
2.4 KiB
C
112 lines
2.4 KiB
C
// window.c
|
|
//
|
|
// Author: J.A. de Jong -ASCEE
|
|
//
|
|
// Description:
|
|
//
|
|
//////////////////////////////////////////////////////////////////////
|
|
|
|
#include "lasp_window.h"
|
|
#include "lasp_signals.h"
|
|
#include <stdlib.h>
|
|
/**
|
|
* Compute the Hann window
|
|
*
|
|
* @param i index
|
|
* @param N Number of indices
|
|
*/
|
|
static d hann(us i,us N) {
|
|
dbgassert(i<N,"Invalid index for window function Hann");
|
|
return d_pow(d_sin(number_pi*i/(N-1)),2);
|
|
}
|
|
/**
|
|
* Compute the Hamming window
|
|
*
|
|
* @param i index
|
|
* @param N Number of indices
|
|
*/
|
|
static d hamming(us i,us N) {
|
|
dbgassert(i<N,"Invalid index for window function Hamming");
|
|
d alpha = 25.0/46.0;
|
|
return alpha-(1-alpha)*d_cos(2*number_pi*i/(N-1));
|
|
}
|
|
/**
|
|
* Compute the Blackman window
|
|
*
|
|
* @param i index
|
|
* @param N Number of indices
|
|
*/
|
|
static d blackman(us i,us N) {
|
|
dbgassert(i<N,"Invalid index for window function Blackman");
|
|
d a0 = 7938./18608.;
|
|
d a1 = 9240./18608.;
|
|
d a2 = 1430./18608.;
|
|
return a0-a1*d_cos(2*number_pi*i/(N-1))+a2*d_cos(4*number_pi*i/(N-1));
|
|
}
|
|
/**
|
|
* Compute the Rectangular window
|
|
*
|
|
* @param i index
|
|
* @param N Number of indices
|
|
*/
|
|
static d rectangle(us i,us N) {
|
|
dbgassert(i<N,"Invalid index for window function Hann");
|
|
return 1.0;
|
|
}
|
|
static d bartlett(us n,us N) {
|
|
dbgassert(n<N,"Invalid index for window function Bartlett");
|
|
return 1 - d_abs(2*(n - (N-1)/2.)/(N-1));
|
|
}
|
|
int window_create(const WindowType wintype,vd* result,d* win_pow) {
|
|
fsTRACE(15);
|
|
dbgassert(result && win_pow,NULLPTRDEREF);
|
|
assert_vx(result);
|
|
|
|
us nfft = result->n_rows;
|
|
d (*win_fun)(us,us);
|
|
switch (wintype) {
|
|
case Hann: {
|
|
win_fun = hann;
|
|
break;
|
|
}
|
|
case Hamming: {
|
|
win_fun = hamming;
|
|
break;
|
|
}
|
|
case Rectangular: {
|
|
win_fun = rectangle;
|
|
break;
|
|
}
|
|
case Bartlett: {
|
|
win_fun = bartlett;
|
|
break;
|
|
}
|
|
case Blackman: {
|
|
win_fun = blackman;
|
|
break;
|
|
}
|
|
default:
|
|
DBGWARN("BUG: Unknown window function");
|
|
abort();
|
|
break;
|
|
}
|
|
us index;
|
|
for(index=0;index<nfft;index++) {
|
|
|
|
/* Compute the window function value */
|
|
d val = win_fun(index,nfft);
|
|
|
|
/* Set the value in the vector */
|
|
setvecval(result,index,val);
|
|
}
|
|
|
|
/* Store window power in result */
|
|
*win_pow = signal_power(result);
|
|
|
|
feTRACE(15);
|
|
return LASP_SUCCESS;
|
|
}
|
|
|
|
|
|
//////////////////////////////////////////////////////////////////////
|