101 lines
2.1 KiB
C
101 lines
2.1 KiB
C
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// window.c
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//
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// Author: J.A. de Jong -ASCEE
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//
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// Description:
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//
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//////////////////////////////////////////////////////////////////////
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#include "window.h"
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#include "signals.h"
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/**
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* Compute the Hann window
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*
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* @param i index
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* @param N Number of indices
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*/
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static d hann(us i,us N) {
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dbgassert(i<N,"Invalid index for window function Hann");
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return d_pow(d_sin(number_pi*i/(N-1)),2);
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}
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/**
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* Compute the Hamming window
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*
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* @param i index
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* @param N Number of indices
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*/
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static d hamming(us i,us N) {
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dbgassert(i<N,"Invalid index for window function Hamming");
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d alpha = 25.0/46.0;
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return alpha-(1-alpha)*d_cos(2*number_pi*i/(N-1));
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}
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/**
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* Compute the Blackman window
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*
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* @param i index
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* @param N Number of indices
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*/
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static d blackman(us i,us N) {
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dbgassert(i<N,"Invalid index for window function Blackman");
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d a0 = 7938./18608.;
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d a1 = 9240./18608.;
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d a2 = 1430./18608.;
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return a0-a1*d_cos(2*number_pi*i/(N-1))+a2*d_cos(4*number_pi*i/(N-1));
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}
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/**
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* Compute the Rectangular window
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*
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* @param i index
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* @param N Number of indices
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*/
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static d rectangle(us i,us N) {
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dbgassert(i<N,"Invalid index for window function Hann");
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return 1.0;
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}
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int window_create(const WindowType wintype,vd* result,d* win_pow) {
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us nfft = result->size;
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d (*win_fun)(us,us);
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switch (wintype) {
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case Hann: {
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win_fun = hann;
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break;
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}
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case Hamming: {
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win_fun = hamming;
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break;
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}
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case Blackman: {
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win_fun = blackman;
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break;
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}
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case Rectangular: {
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win_fun = rectangle;
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break;
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}
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default:
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WARN("Unkown window function");
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return FAILURE;
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break;
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}
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us index;
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for(index=0;index<nfft;index++) {
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/* Compute the window function value */
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d val = win_fun(index,nfft);
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/* Set the value in the vector */
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setvecval(result,index,val);
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}
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*win_pow = signal_power(result);
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/* Store window power in result */
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return SUCCESS;
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}
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//////////////////////////////////////////////////////////////////////
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