/*
*
      
_______
                       
_____
   
_____ _____
  

*
     
|__
   
__|
                     
|
  
__ \ / ____|__ \
 

*
        
| | __ _ _ __ ___
  
______| || | (___ | |__) |
*
        
| |/ _` | '__/ __|/ _ \/ __| |
  
| |\___ \|___/
 

*
        
| | (_| | |
  
\__ \ (_) \__ \ |__| |____) | |
     

*
        
|_|\__,_|_|
  
|___/\___/|___/_____/|_____/|_|
     

*
                                                         

* -------------------------------------------------------------
*
* 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.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 };
  
}
}