1 /********************************************************************
3 * THIS FILE IS PART OF THE Ogg Vorbis SOFTWARE CODEC SOURCE CODE. *
4 * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
5 * THE GNU PUBLIC LICENSE 2, WHICH IS INCLUDED WITH THIS SOURCE. *
6 * PLEASE READ THESE TERMS DISTRIBUTING. *
8 * THE OggSQUISH SOURCE CODE IS (C) COPYRIGHT 1994-2000 *
9 * by Monty <monty@xiph.org> and The XIPHOPHORUS Company *
10 * http://www.xiph.org/ *
12 ********************************************************************
14 function: lookup based functions
15 last mod: $Id: lookup.c,v 1.2 2000/10/12 03:12:53 xiphmont Exp $
17 ********************************************************************/
21 #include "lookup_data.h"
25 /* interpolated lookup based cos function, domain 0 to PI only */
26 float vorbis_coslook(float a){
27 float d=a*(.31830989*(float)COS_LOOKUP_SZ);
29 return COS_LOOKUP[i]+ (d-i)*(COS_LOOKUP[i+1]-COS_LOOKUP[i]);
32 /* interpolated 1./sqrt(p) where .5 <= p < 1. */
33 float vorbis_invsqlook(float a){
34 float d=a*(2.*(float)INVSQ_LOOKUP_SZ)-(float)INVSQ_LOOKUP_SZ;
36 return INVSQ_LOOKUP[i]+ (d-i)*(INVSQ_LOOKUP[i+1]-INVSQ_LOOKUP[i]);
39 /* interpolated 1./sqrt(p) where .5 <= p < 1. */
40 float vorbis_invsq2explook(int a){
41 return INVSQ2EXP_LOOKUP[a-INVSQ2EXP_LOOKUP_MIN];
45 /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
46 float vorbis_fromdBlook(float a){
47 int i=a*((float)(-(1<<FROMdB2_SHIFT)));
49 ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.:
50 FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
56 /* interpolated 1./sqrt(p) where .5 <= a < 1. (.100000... to .111111...) in
59 returns in m.8 format */
60 long vorbis_invsqlook_i(long a,long e){
61 long i=(a&0x7fff)>>(INVSQ_LOOKUP_I_SHIFT-1);
62 long d=(a&INVSQ_LOOKUP_I_MASK)<<(16-INVSQ_LOOKUP_I_SHIFT); /* 0.16 */
63 long val=INVSQ_LOOKUP_I[i]- /* 1.16 */
64 (((INVSQ_LOOKUP_I[i]-INVSQ_LOOKUP_I[i+1])* /* 0.16 */
65 d)>>16); /* result 1.16 */
68 if(e&1)val=(val*5792)>>13; /* multiply val by 1/sqrt(2) */
74 /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
75 /* a is in n.12 format */
76 float vorbis_fromdBlook_i(long a){
77 int i=(-a)>>(12-FROMdB2_SHIFT);
79 ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.:
80 FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
83 /* interpolated lookup based cos function, domain 0 to PI only */
84 /* a is in 0.16 format, where 0==0, 2^^16-1==PI, return 0.14 */
85 long vorbis_coslook_i(long a){
86 int i=a>>COS_LOOKUP_I_SHIFT;
87 int d=a&COS_LOOKUP_I_MASK;
88 return COS_LOOKUP_I[i]- ((d*(COS_LOOKUP_I[i]-COS_LOOKUP_I[i+1]))>>