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 * 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.

 *

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package com.sun.media.sound;

/**

 * Hann windowed sinc interpolation resampler with anti-alias filtering.

 *

 * Using 30 points for the interpolation.

 *

 * @author Karl Helgason

 */

public final class SoftSincResampler extends SoftAbstractResampler {

    float[][][] sinc_table;

    int sinc_scale_size = 100;

    int sinc_table_fsize = 800;

    int sinc_table_size = 30;

    int sinc_table_center = sinc_table_size / 2;

    public SoftSincResampler() {

        super();

        sinc_table = new float[sinc_scale_size][sinc_table_fsize][];

        for (int s = 0; s < sinc_scale_size; s++) {

            float scale = (float) (1.0 / (1.0 + Math.pow(s, 1.1) / 10.0));

            for (int i = 0; i < sinc_table_fsize; i++) {

                sinc_table[s][i] = sincTable(sinc_table_size,

                        -i / ((float)sinc_table_fsize), scale);

            }

        }

    }

    // Normalized sinc function

    public static double sinc(double x) {

        return (x == 0.0) ? 1.0 : Math.sin(Math.PI * x) / (Math.PI * x);

    }

    // Generate hann window suitable for windowing sinc

    public static float[] wHanning(int size, float offset) {

        float[] window_table = new float[size];

        for (int k = 0; k < size; k++) {

            window_table[k] = (float)(-0.5

                    * Math.cos(2.0 * Math.PI * (double)(k + offset)

                        / (double) size) + 0.5);

        }

        return window_table;

    }

    // Generate sinc table

    public static float[] sincTable(int size, float offset, float scale) {

        int center = size / 2;

        float[] w = wHanning(size, offset);

        for (int k = 0; k < size; k++)

            w[k] *= sinc((-center + k + offset) * scale) * scale;

        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;

        int max_p = sinc_scale_size - 1;

        if (pitchstep == 0) {

            int p = (int) ((pitch - 1) * 10.0f);

            if (p < 0)

                p = 0;

            else if (p > max_p)

                p = max_p;

            float[][] sinc_table_f = this.sinc_table[p];

            while (ix < ix_end && ox < ox_end) {

                int iix = (int) ix;

                float[] sinc_table =

                        sinc_table_f[(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;

                int p = (int) ((pitch - 1) * 10.0f);

                if (p < 0)

                    p = 0;

                else if (p > max_p)

                    p = max_p;

                float[][] sinc_table_f = this.sinc_table[p];

                float[] sinc_table =

                        sinc_table_f[(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;

    }

}