annotate src/samer/units/FIRFilter.java @ 8:5e3cbbf173aa tip

Reorganise some more

/*
 *	Copyright (c) 2000, Samer Abdallah, King's College London.
 *	All rights reserved.
 *
 *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
 *	without even the implied warranty of MERCHANTABILITY or 
 *	FITNESS FOR A PARTICULAR PURPOSE.
 */

package samer.units;
import  samer.core.*;
import  samer.maths.*;
import  samer.tools.*;
import  java.util.*;

public class FIRFilter implements Filter
{
	int		N;			// order of filter
	double	A[];	// coefficients
	double	u[];		// circular buffer of previous values
	int		k;    		// current position in u buffer

	public FIRFilter( int n)
	{
		N=n;
		u=new double[n];
		A=new double[n];
		reset();
	}

	public FIRFilter( double [] A)
	{
		N=A.length;
		u=new double[N];
		this.A=A;
		reset();
	}

	public void dispose() {}
	public void reset() { Mathx.zero(u); k=0; }

	/** FIR filter using array of filter coefficients */
	public final double filter( double z)
	{
		if (k==0) k=N-1; else k--;
		double	y=0;
		u[k]=z;

		int i=0, j;
		for (j=k; j<N; j++) y += u[j]*A[i++];
		for (j=0; j<k; j++) y += u[j]*A[i++];

		return y;
	}
}