/*
 * Copyright 2007 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.media.sound;

/**
 * Lanczos interpolation resampler.
 * 
 * @version %I%, %E%
 * @author Karl Helgason
 */
public class SoftLanczosResampler extends SoftAbstractResampler {

	double[] din;

	float[][] sinc_table;

	int sinc_table_fsize = 2000;

	int sinc_table_size = 5;

	int sinc_table_center = sinc_table_size / 2;

	public SoftLanczosResampler() {
		super();
		sinc_table = new float[sinc_table_fsize][];
		for (int i = 0; i < sinc_table_fsize; i++)
			sinc_table[i] = sincTable(sinc_table_size, -i
					/ ((float) sinc_table_fsize));
	}

	// Normalized sinc function
	public static double sinc(double x) {
		return (x == 0.0) ? 1.0 : Math.sin(Math.PI * x) / (Math.PI * x);
	}

	// Generate sinc table
	public static float[] sincTable(int size, float offset) {
		int center = size / 2;
		float[] w = new float[size];
		for (int k = 0; k < size; k++) {
			float x = (-center + k + offset);
			if (x < -2 || x > 2)
				w[k] = 0;
			else if (x == 0)
				w[k] = 1;
			else
				w[k] = (float) (2.0 * Math.sin(Math.PI * x)
						* Math.sin(Math.PI * x / 2.0) / ((Math.PI * x) * (Math.PI * x)));
		}
		return w;
	}

	public int getPadding() // must be at least half of sinc_table_size
	{
		return sinc_table_size / 2 + 2;
	}

	public void interpolate(float[] in, float[] in_offset, float in_end,
			float[] startpitch, float pitchstep, float[] out, int[] out_offset,
			int out_end) {
		float pitch = startpitch[0];
		float ix = in_offset[0];
		int ox = out_offset[0];
		float ix_end = in_end;
		int ox_end = out_end;

		if (pitchstep == 0) {
			while (ix < ix_end && ox < ox_end) {
				int iix = (int) ix;
				float[] sinc_table = this.sinc_table[(int) ((ix - iix) * sinc_table_fsize)];
				int xx = iix - sinc_table_center;
				float y = 0;
				for (int i = 0; i < sinc_table_size; i++, xx++)
					y += in[xx] * sinc_table[i];
				out[ox++] = y;
				ix += pitch;
			}
		} else {
			while (ix < ix_end && ox < ox_end) {
				int iix = (int) ix;
				float[] sinc_table = this.sinc_table[(int) ((ix - iix) * sinc_table_fsize)];
				int xx = iix - sinc_table_center;
				float y = 0;
				for (int i = 0; i < sinc_table_size; i++, xx++)
					y += in[xx] * sinc_table[i];
				out[ox++] = y;

				ix += pitch;
				pitch += pitchstep;
			}
		}
		in_offset[0] = ix;
		out_offset[0] = ox;
		startpitch[0] = pitch;

	}

}