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    1   /*
    2    * Copyright (c) 2007, 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 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   }

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