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/*
dsp/sinc.h
Copyright 2003-4 Tim Goetze <tim@quitte.de>
http://quitte.de/dsp/
computes the sinc function: sin (x * pi) / (x * pi).
*/
/*
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA or point your web browser to http://www.gnu.org.
*/
#ifndef _SINC_H_
#define _SINC_H_
#include "Sine.h"
namespace DSP {
/* sample sinc() with step size omega into s[], centered around s + n / 2 */
inline void
sinc (double omega, d_sample * s, int n)
{
/* initial phase */
double phi = (n / 2) * -omega;
Sine sine (omega, phi);
for (int i = 0; i < n; ++i, phi += omega)
{
double sin_phi = sine.get();
if (fabs (phi) < 0.000000001)
s[i] = 1.;
else
s[i] = sin_phi / phi;
}
}
}; /* namespace DSP */
#endif /* _SINC_H_ */
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