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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 http://www.xiph.org/                  *
     10  *                                                                  *
     11  ********************************************************************
     12 
     13   function: lookup based functions
     14   last mod: $Id: lookup.c 16227 2009-07-08 06:58:46Z xiphmont $
     15 
     16  ********************************************************************/
     17 
     18 #include <math.h>
     19 #include "lookup.h"
     20 #include "lookup_data.h"
     21 #include "os.h"
     22 #include "misc.h"
     23 
     24 #ifdef FLOAT_LOOKUP
     25 
     26 /* interpolated lookup based cos function, domain 0 to PI only */
     27 float vorbis_coslook(float a){
     28   double d=a*(.31830989*(float)COS_LOOKUP_SZ);
     29   int i=vorbis_ftoi(d-.5);
     30 
     31   return COS_LOOKUP[i]+ (d-i)*(COS_LOOKUP[i+1]-COS_LOOKUP[i]);
     32 }
     33 
     34 /* interpolated 1./sqrt(p) where .5 <= p < 1. */
     35 float vorbis_invsqlook(float a){
     36   double d=a*(2.f*(float)INVSQ_LOOKUP_SZ)-(float)INVSQ_LOOKUP_SZ;
     37   int i=vorbis_ftoi(d-.5f);
     38   return INVSQ_LOOKUP[i]+ (d-i)*(INVSQ_LOOKUP[i+1]-INVSQ_LOOKUP[i]);
     39 }
     40 
     41 /* interpolated 1./sqrt(p) where .5 <= p < 1. */
     42 float vorbis_invsq2explook(int a){
     43   return INVSQ2EXP_LOOKUP[a-INVSQ2EXP_LOOKUP_MIN];
     44 }
     45 
     46 #include <stdio.h>
     47 /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
     48 float vorbis_fromdBlook(float a){
     49   int i=vorbis_ftoi(a*((float)(-(1<<FROMdB2_SHIFT)))-.5f);
     50   return (i<0)?1.f:
     51     ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
     52      FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
     53 }
     54 
     55 #endif
     56 
     57 #ifdef INT_LOOKUP
     58 /* interpolated 1./sqrt(p) where .5 <= a < 1. (.100000... to .111111...) in
     59    16.16 format
     60 
     61    returns in m.8 format */
     62 long vorbis_invsqlook_i(long a,long e){
     63   long i=(a&0x7fff)>>(INVSQ_LOOKUP_I_SHIFT-1);
     64   long d=(a&INVSQ_LOOKUP_I_MASK)<<(16-INVSQ_LOOKUP_I_SHIFT); /*  0.16 */
     65   long val=INVSQ_LOOKUP_I[i]-                                /*  1.16 */
     66     (((INVSQ_LOOKUP_I[i]-INVSQ_LOOKUP_I[i+1])*               /*  0.16 */
     67       d)>>16);                                               /* result 1.16 */
     68 
     69   e+=32;
     70   if(e&1)val=(val*5792)>>13; /* multiply val by 1/sqrt(2) */
     71   e=(e>>1)-8;
     72 
     73   return(val>>e);
     74 }
     75 
     76 /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
     77 /* a is in n.12 format */
     78 float vorbis_fromdBlook_i(long a){
     79   int i=(-a)>>(12-FROMdB2_SHIFT);
     80   return (i<0)?1.f:
     81     ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
     82      FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
     83 }
     84 
     85 /* interpolated lookup based cos function, domain 0 to PI only */
     86 /* a is in 0.16 format, where 0==0, 2^^16-1==PI, return 0.14 */
     87 long vorbis_coslook_i(long a){
     88   int i=a>>COS_LOOKUP_I_SHIFT;
     89   int d=a&COS_LOOKUP_I_MASK;
     90   return COS_LOOKUP_I[i]- ((d*(COS_LOOKUP_I[i]-COS_LOOKUP_I[i+1]))>>
     91                            COS_LOOKUP_I_SHIFT);
     92 }
     93 
     94 #endif
     95