/*
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.media.sound;

Hann windowed sinc interpolation resampler with anti-alias filtering. Using 30 points for the interpolation.
Author:Karl Helgason
/** * 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; } @Override public int getPadding() // must be at least half of sinc_table_size { return sinc_table_size / 2 + 2; } @Override 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; } }