1 /*
   2  * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package com.sun.media.sound;
  26 
  27 /**
  28  * Lanczos interpolation resampler.
  29  *
  30  * @author Karl Helgason
  31  */
  32 public final class SoftLanczosResampler extends SoftAbstractResampler {
  33 
  34     float[][] sinc_table;
  35     int sinc_table_fsize = 2000;
  36     int sinc_table_size = 5;
  37     int sinc_table_center = sinc_table_size / 2;
  38 
  39     public SoftLanczosResampler() {
  40         super();
  41         sinc_table = new float[sinc_table_fsize][];
  42         for (int i = 0; i < sinc_table_fsize; i++) {
  43             sinc_table[i] = sincTable(sinc_table_size, -i
  44                             / ((float) sinc_table_fsize));
  45         }
  46     }
  47 
  48     // Normalized sinc function
  49     public static double sinc(double x) {
  50         return (x == 0.0) ? 1.0 : Math.sin(Math.PI * x) / (Math.PI * x);
  51     }
  52 
  53     // Generate sinc table
  54     public static float[] sincTable(int size, float offset) {
  55         int center = size / 2;
  56         float[] w = new float[size];
  57         for (int k = 0; k < size; k++) {
  58             float x = (-center + k + offset);
  59             if (x < -2 || x > 2)
  60                 w[k] = 0;
  61             else if (x == 0)
  62                 w[k] = 1;
  63             else {
  64                 w[k] = (float)(2.0 * Math.sin(Math.PI * x)
  65                                 * Math.sin(Math.PI * x / 2.0)
  66                                 / ((Math.PI * x) * (Math.PI * x)));
  67             }
  68         }
  69         return w;
  70     }
  71 
  72     public int getPadding() // must be at least half of sinc_table_size
  73     {
  74         return sinc_table_size / 2 + 2;
  75     }
  76 
  77     public void interpolate(float[] in, float[] in_offset, float in_end,
  78             float[] startpitch, float pitchstep, float[] out, int[] out_offset,
  79             int out_end) {
  80         float pitch = startpitch[0];
  81         float ix = in_offset[0];
  82         int ox = out_offset[0];
  83         float ix_end = in_end;
  84         int ox_end = out_end;
  85 
  86         if (pitchstep == 0) {
  87             while (ix < ix_end && ox < ox_end) {
  88                 int iix = (int) ix;
  89                 float[] sinc_table
  90                         = this.sinc_table[(int) ((ix - iix) * sinc_table_fsize)];
  91                 int xx = iix - sinc_table_center;
  92                 float y = 0;
  93                 for (int i = 0; i < sinc_table_size; i++, xx++)
  94                     y += in[xx] * sinc_table[i];
  95                 out[ox++] = y;
  96                 ix += pitch;
  97             }
  98         } else {
  99             while (ix < ix_end && ox < ox_end) {
 100                 int iix = (int) ix;
 101                 float[] sinc_table
 102                         = this.sinc_table[(int) ((ix - iix) * sinc_table_fsize)];
 103                 int xx = iix - sinc_table_center;
 104                 float y = 0;
 105                 for (int i = 0; i < sinc_table_size; i++, xx++)
 106                     y += in[xx] * sinc_table[i];
 107                 out[ox++] = y;
 108 
 109                 ix += pitch;
 110                 pitch += pitchstep;
 111             }
 112         }
 113         in_offset[0] = ix;
 114         out_offset[0] = ox;
 115         startpitch[0] = pitch;
 116 
 117     }
 118 }