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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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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;
}
}