/*
*
      
_______
                       
_____
   
_____ _____
  

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

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

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

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

*
                                                         

* -------------------------------------------------------------
*
* 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;

/**
 
* Four stage low pass filter.
 
*
 
*/
public class LowPassFS extends IIRFilter{
	

	
public LowPassFS(float freq, float sampleRate) {
		
//minimum frequency is 60Hz!
		
super(freq>60?freq:60, sampleRate);
	
}

	
@Override
	
protected void calcCoeff() {
		
float freqFrac = getFrequency() / getSampleRate();
		
float x = (float) Math.exp(-14.445 * freqFrac);
		
a = new float[] { (float) Math.pow(1 - x, 4) };
		
b = new float[] { 4 * x, -6 * x * x, 4 * x * x * x, -x * x * x * x };
	
}


}