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lookup.c
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lookup.c
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/********************************************************************
* *
* THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE. *
* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
* *
* THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009 *
* by the Xiph.Org Foundation http://www.xiph.org/ *
* *
********************************************************************
function: lookup based functions
********************************************************************/
#include <math.h>
#include "lookup.h"
#include "lookup_data.h"
#include "os.h"
#include "misc.h"
#ifdef FLOAT_LOOKUP
/* interpolated lookup based cos function, domain 0 to PI only */
float vorbis_coslook(float a){
double d=a*(.31830989*(float)COS_LOOKUP_SZ);
int i=vorbis_ftoi(d-.5);
return COS_LOOKUP[i]+ (d-i)*(COS_LOOKUP[i+1]-COS_LOOKUP[i]);
}
/* interpolated 1./sqrt(p) where .5 <= p < 1. */
float vorbis_invsqlook(float a){
double d=a*(2.f*(float)INVSQ_LOOKUP_SZ)-(float)INVSQ_LOOKUP_SZ;
int i=vorbis_ftoi(d-.5f);
return INVSQ_LOOKUP[i]+ (d-i)*(INVSQ_LOOKUP[i+1]-INVSQ_LOOKUP[i]);
}
/* interpolated 1./sqrt(p) where .5 <= p < 1. */
float vorbis_invsq2explook(int a){
return INVSQ2EXP_LOOKUP[a-INVSQ2EXP_LOOKUP_MIN];
}
#include <stdio.h>
/* interpolated lookup based fromdB function, domain -140dB to 0dB only */
float vorbis_fromdBlook(float a){
int i=vorbis_ftoi(a*((float)(-(1<<FROMdB2_SHIFT)))-.5f);
return (i<0)?1.f:
((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
}
#endif
#ifdef INT_LOOKUP
/* interpolated 1./sqrt(p) where .5 <= a < 1. (.100000... to .111111...) in
16.16 format
returns in m.8 format */
long vorbis_invsqlook_i(long a,long e){
long i=(a&0x7fff)>>(INVSQ_LOOKUP_I_SHIFT-1);
long d=(a&INVSQ_LOOKUP_I_MASK)<<(16-INVSQ_LOOKUP_I_SHIFT); /* 0.16 */
long val=INVSQ_LOOKUP_I[i]- /* 1.16 */
(((INVSQ_LOOKUP_I[i]-INVSQ_LOOKUP_I[i+1])* /* 0.16 */
d)>>16); /* result 1.16 */
e+=32;
if(e&1)val=(val*5792)>>13; /* multiply val by 1/sqrt(2) */
e=(e>>1)-8;
return(val>>e);
}
/* interpolated lookup based fromdB function, domain -140dB to 0dB only */
/* a is in n.12 format */
float vorbis_fromdBlook_i(long a){
int i=(-a)>>(12-FROMdB2_SHIFT);
return (i<0)?1.f:
((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
}
/* interpolated lookup based cos function, domain 0 to PI only */
/* a is in 0.16 format, where 0==0, 2^^16-1==PI, return 0.14 */
long vorbis_coslook_i(long a){
int i=a>>COS_LOOKUP_I_SHIFT;
int d=a&COS_LOOKUP_I_MASK;
return COS_LOOKUP_I[i]- ((d*(COS_LOOKUP_I[i]-COS_LOOKUP_I[i+1]))>>
COS_LOOKUP_I_SHIFT);
}
#endif