comparison 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() {}
+}
+