annotate src/samer/units/SpectralFIR.java @ 0:bf79fb79ee13

Initial Mercurial check in.

/*
 *	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.*;

public class SpectralFIR implements Task
{
	FFT				fft;
	Vec				spectrum;
	VVector	A;
	int				n, m;

	public SpectralFIR(int n, VVector input)
	{
		this.n = n;

		fft=new FFT(n);
		fft.setWindow(new Constant(1));
		fft.invert();

		spectrum = input;
		A=new VVector("coeffs",n);
	}

	public VVector coefficients() { return A; }

	public void dispose() { A.dispose(); }
	public void run() {
		Vec.Iterator it=spectrum.iterator();
		double [] _A=A.array();

		Mathx.zero(fft.real);
		Mathx.zero(fft.imag);

		fft.real[fft.bitrev[0]]=it.next();	 // zero frequency
		for (int i=1; it.more(); i++) {
			fft.real[fft.bitrev[i]] = fft.real[fft.bitrev[n-i]] = it.next(); // pos and neg freqs
		}
		fft.calculate();

		// copy FFT results to filter coefficients
		// with some reordering
		System.arraycopy( fft.real, n/2, _A, 0, n/2);
		System.arraycopy( fft.real, 0, _A, n/2, n/2);
		A.changed();
	}

	// private static double pos(double t) { if (t<0) return 0; else return t; }

	public void starting() {}
	public void stopping() {}
}