tremor/window.c

   1 /********************************************************************
   2  *                                                                  *
   3  * THIS FILE IS PART OF THE OggVorbis 'TREMOR' CODEC SOURCE CODE.   *
   4  *                                                                  *
   5  * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
   6  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
   7  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
   8  *                                                                  *
   9  * THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2002    *
  10  * BY THE Xiph.Org FOUNDATION http://www.xiph.org/                  *
  11  *                                                                  *
  12  ********************************************************************
  13
  14  function: window functions
  15
  16  ********************************************************************/
  17
  18 #include <stdlib.h>
  19 #include <math.h>
  20 #include "os.h"
  21 #include "misc.h"
  22 #include "window.h"
  23 #include "window_lookup.h"
  24
  25 const void *_vorbis_window(int type, int left){
  26
  27   switch(type){
  28   case 0:
  29
  30     switch(left){
  31     case 32:
  32       return vwin64;
  33     case 64:
  34       return vwin128;
  35     case 128:
  36       return vwin256;
  37     case 256:
  38       return vwin512;
  39     case 512:
  40       return vwin1024;
  41     case 1024:
  42       return vwin2048;
  43     case 2048:
  44       return vwin4096;
  45     case 4096:
  46       return vwin8192;
  47     default:
  48       return(0);
  49     }
  50     break;
  51   default:
  52     return(0);
  53   }
  54 }
  55
  56 void _vorbis_apply_window(ogg_int32_t *d,const void *window_p[2],
  57                           long *blocksizes,
  58                           int lW,int W,int nW){
  59
  60   LOOKUP_T *window[2]={window_p[0],window_p[1]};
  61   long n=blocksizes[W];
  62   long ln=blocksizes[lW];
  63   long rn=blocksizes[nW];
  64
  65   long leftbegin=n/4-ln/4;
  66   long leftend=leftbegin+ln/2;
  67
  68   long rightbegin=n/2+n/4-rn/4;
  69   long rightend=rightbegin+rn/2;
  70
  71   int i,p;
  72
  73   for(i=0;i<leftbegin;i++)
  74     d[i]=0;
  75
  76   for(p=0;i<leftend;i++,p++)
  77     d[i]=MULT31(d[i],window[lW][p]);
  78
  79   for(i=rightbegin,p=rn/2-1;i<rightend;i++,p--)
  80     d[i]=MULT31(d[i],window[nW][p]);
  81
  82   for(;i<n;i++)
  83     d[i]=0;
  84 }