/*
* _______ _____ _____ _____
* |__ __| | __ \ / ____| __ \
* | | __ _ _ __ ___ ___ ___| | | | (___ | |__) |
* | |/ _` | '__/ __|/ _ \/ __| | | |\___ \| ___/
* | | (_| | | \__ \ (_) \__ \ |__| |____) | |
* |_|\__,_|_| |___/\___/|___/_____/|_____/|_|
*
* -------------------------------------------------------------
*
* TarsosDSP is developed by Joren Six at IPEM, University Ghent
*
* -------------------------------------------------------------
*
* Info: http://0110.be/tag/TarsosDSP
* Github: https://github.com/JorenSix/TarsosDSP
* Releases: http://0110.be/releases/TarsosDSP/
*
* TarsosDSP includes modified source code by various authors,
* for credits and info, see README.
*
*/
/*
* Copyright (c) 2007 - 2008 by Damien Di Fede <ddf@compartmental.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library 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 Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
package be.tarsos.dsp.util.fft;
/**
* A Blackman window function.
*
* @author Damien Di Fede
* @author Corban Brook
* @see <a href="http://en.wikipedia.org/wiki/Window_function#Blackman_windows">The Blackman Window</a>
*/
public class BlackmanWindow extends WindowFunction {
protected float alpha;
/**
* Constructs a Blackman window.
*
* @param alpha
*/
public BlackmanWindow(float alpha) {
this.alpha = alpha;
}
/** Constructs a Blackman window with a default alpha value of 0.16 */
public BlackmanWindow() {
this(0.16f);
}
protected float value(int length, int index){
float a0 = (1 - this.alpha) / 2f;
float a1 = 0.5f;
float a2 = this.alpha / 2f;
return a0 - a1 * (float) Math.cos(TWO_PI * index / (length - 1)) + a2 * (float) Math.cos(4 * Math.PI * index / (length - 1));
}
}