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lookup.c (3290B)
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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 1994-2002 *
9 * by the XIPHOPHORUS Company http://www.xiph.org/ *
10 * *
11 ********************************************************************
12
13 function: lookup based functions
14 last mod: $Id: lookup.c 1919 2005-07-24 14:18:04Z baford $
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