samer@0: /*
samer@0:  *	Copyright (c) 2000, Samer Abdallah, King's College London.
samer@0:  *	All rights reserved.
samer@0:  *
samer@0:  *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
samer@0:  *	without even the implied warranty of MERCHANTABILITY or
samer@0:  *	FITNESS FOR A PARTICULAR PURPOSE.
samer@0:  */
samer@0: 
samer@0: package samer.units;
samer@0: import  samer.core.*;
samer@0: import  samer.maths.*;
samer@0: import  samer.tools.*;
samer@0: 
samer@0: public class SpectralFIR implements Task
samer@0: {
samer@0: 	FFT				fft;
samer@0: 	Vec				spectrum;
samer@0: 	VVector	A;
samer@0: 	int				n, m;
samer@0: 
samer@0: 	public SpectralFIR(int n, VVector input)
samer@0: 	{
samer@0: 		this.n = n;
samer@0: 
samer@0: 		fft=new FFT(n);
samer@0: 		fft.setWindow(new Constant(1));
samer@0: 		fft.invert();
samer@0: 
samer@0: 		spectrum = input;
samer@0: 		A=new VVector("coeffs",n);
samer@0: 	}
samer@0: 
samer@0: 	public VVector coefficients() { return A; }
samer@0: 
samer@0: 	public void dispose() { A.dispose(); }
samer@0: 	public void run() {
samer@0: 		Vec.Iterator it=spectrum.iterator();
samer@0: 		double [] _A=A.array();
samer@0: 
samer@0: 		Mathx.zero(fft.real);
samer@0: 		Mathx.zero(fft.imag);
samer@0: 
samer@0: 		fft.real[fft.bitrev[0]]=it.next();	 // zero frequency
samer@0: 		for (int i=1; it.more(); i++) {
samer@0: 			fft.real[fft.bitrev[i]] = fft.real[fft.bitrev[n-i]] = it.next(); // pos and neg freqs
samer@0: 		}
samer@0: 		fft.calculate();
samer@0: 
samer@0: 		// copy FFT results to filter coefficients
samer@0: 		// with some reordering
samer@0: 		System.arraycopy( fft.real, n/2, _A, 0, n/2);
samer@0: 		System.arraycopy( fft.real, 0, _A, n/2, n/2);
samer@0: 		A.changed();
samer@0: 	}
samer@0: 
samer@0: 	// private static double pos(double t) { if (t<0) return 0; else return t; }
samer@0: 
samer@0: 	public void starting() {}
samer@0: 	public void stopping() {}
samer@0: }
samer@0: