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 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.sun.media.sound;

/**

 * Lanczos interpolation resampler.

 *

 * @author Karl Helgason

 */

public final class SoftLanczosResampler extends SoftAbstractResampler {

    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;

    }

}