core.be.tarsos.dsp.filters.BandPass Maven / Gradle / Ivy
The newest version!
/*
* _______ _____ _____ _____
* |__ __| | __ \ / ____| __ \
* | | __ _ _ __ ___ ___ ___| | | | (___ | |__) |
* | |/ _` | '__/ __|/ _ \/ __| | | |\___ \| ___/
* | | (_| | | \__ \ (_) \__ \ |__| |____) | |
* |_|\__,_|_| |___/\___/|___/_____/|_____/|_|
*
* -------------------------------------------------------------
*
* 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
*
* 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.filters;
/**
* A band pass filter is a filter that filters out all frequencies except for
* those in a band centered on the current frequency of the filter.
*
* @author Damien Di Fede
*
*/
public class BandPass extends IIRFilter
{
private float bw;
/**
* Constructs a band pass filter with the requested center frequency,
* bandwidth and sample rate.
*
* @param freq
* the center frequency of the band to pass (in Hz)
* @param bandWidth
* the width of the band to pass (in Hz)
* @param sampleRate
* the sample rate of audio that will be filtered by this filter
*/
public BandPass(float freq, float bandWidth, float sampleRate)
{
super(freq, sampleRate);
setBandWidth(bandWidth);
}
/**
* Sets the band width of the filter. Doing this will cause the coefficients
* to be recalculated.
*
* @param bandWidth
* the band width (in Hz)
*/
public void setBandWidth(float bandWidth)
{
bw = bandWidth / getSampleRate();
calcCoeff();
}
/**
* Returns the band width of this filter.
*
* @return the band width (in Hz)
*/
public float getBandWidth()
{
return bw * getSampleRate();
}
protected void calcCoeff()
{
float R = 1 - 3 * bw;
float fracFreq = getFrequency() / getSampleRate();
float T = 2 * (float) Math.cos(2 * Math.PI * fracFreq);
float K = (1 - R * T + R * R) / (2 - T);
a = new float[] { 1 - K, (K - R) * T, R * R - K };
b = new float[] { R * T, -R * R };
}
}