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  1. /********************************************************************
  2.  *                                                                  *
  3.  * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
  4.  * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
  5.  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
  6.  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
  7.  *                                                                  *
  8.  * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009             *
  9.  * by the Xiph.Org Foundation https://xiph.org/                     *
  10.  *                                                                  *
  11.  ********************************************************************
  12.  
  13.   function: lookup based functions
  14.  
  15.  ********************************************************************/
  16.  
  17. #include <math.h>
  18. #include "lookup.h"
  19. #include "lookup_data.h"
  20. #include "os.h"
  21. #include "misc.h"
  22.  
  23. #ifdef FLOAT_LOOKUP
  24.  
  25. /* interpolated lookup based cos function, domain 0 to PI only */
  26. float vorbis_coslook(float a){
  27.   double d=a*(.31830989*(float)COS_LOOKUP_SZ);
  28.   int i=vorbis_ftoi(d-.5);
  29.  
  30.   return COS_LOOKUP[i]+ (d-i)*(COS_LOOKUP[i+1]-COS_LOOKUP[i]);
  31. }
  32.  
  33. /* interpolated 1./sqrt(p) where .5 <= p < 1. */
  34. float vorbis_invsqlook(float a){
  35.   double d=a*(2.f*(float)INVSQ_LOOKUP_SZ)-(float)INVSQ_LOOKUP_SZ;
  36.   int i=vorbis_ftoi(d-.5f);
  37.   return INVSQ_LOOKUP[i]+ (d-i)*(INVSQ_LOOKUP[i+1]-INVSQ_LOOKUP[i]);
  38. }
  39.  
  40. /* interpolated 1./sqrt(p) where .5 <= p < 1. */
  41. float vorbis_invsq2explook(int a){
  42.   return INVSQ2EXP_LOOKUP[a-INVSQ2EXP_LOOKUP_MIN];
  43. }
  44.  
  45. #include <stdio.h>
  46. /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
  47. float vorbis_fromdBlook(float a){
  48.   int i=vorbis_ftoi(a*((float)(-(1<<FROMdB2_SHIFT)))-.5f);
  49.   return (i<0)?1.f:
  50.     ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
  51.      FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
  52. }
  53.  
  54. #endif
  55.  
  56. #ifdef INT_LOOKUP
  57. /* interpolated 1./sqrt(p) where .5 <= a < 1. (.100000... to .111111...) in
  58.    16.16 format
  59.  
  60.    returns in m.8 format */
  61. long vorbis_invsqlook_i(long a,long e){
  62.   long i=(a&0x7fff)>>(INVSQ_LOOKUP_I_SHIFT-1);
  63.   long d=(a&INVSQ_LOOKUP_I_MASK)<<(16-INVSQ_LOOKUP_I_SHIFT); /*  0.16 */
  64.   long val=INVSQ_LOOKUP_I[i]-                                /*  1.16 */
  65.     (((INVSQ_LOOKUP_I[i]-INVSQ_LOOKUP_I[i+1])*               /*  0.16 */
  66.       d)>>16);                                               /* result 1.16 */
  67.  
  68.   e+=32;
  69.   if(e&1)val=(val*5792)>>13; /* multiply val by 1/sqrt(2) */
  70.   e=(e>>1)-8;
  71.  
  72.   return(val>>e);
  73. }
  74.  
  75. /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
  76. /* a is in n.12 format */
  77. float vorbis_fromdBlook_i(long a){
  78.   int i=(-a)>>(12-FROMdB2_SHIFT);
  79.   return (i<0)?1.f:
  80.     ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
  81.      FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
  82. }
  83.  
  84. /* interpolated lookup based cos function, domain 0 to PI only */
  85. /* a is in 0.16 format, where 0==0, 2^^16-1==PI, return 0.14 */
  86. long vorbis_coslook_i(long a){
  87.   int i=a>>COS_LOOKUP_I_SHIFT;
  88.   int d=a&COS_LOOKUP_I_MASK;
  89.   return COS_LOOKUP_I[i]- ((d*(COS_LOOKUP_I[i]-COS_LOOKUP_I[i+1]))>>
  90.                            COS_LOOKUP_I_SHIFT);
  91. }
  92.  
  93. #endif
  94.