95 lines
3.2 KiB
C
95 lines
3.2 KiB
C
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/********************************************************************
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* *
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* THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE. *
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* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
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* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
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* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
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* *
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* THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009 *
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* by the Xiph.Org Foundation http://www.xiph.org/ *
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* *
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********************************************************************
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function: lookup based functions
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last mod: $Id: lookup.c 16227 2009-07-08 06:58:46Z xiphmont $
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********************************************************************/
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#include <math.h>
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#include "lookup.h"
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#include "lookup_data.h"
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#include "os.h"
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#include "misc.h"
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#ifdef FLOAT_LOOKUP
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/* interpolated lookup based cos function, domain 0 to PI only */
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float vorbis_coslook(float a){
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double d=a*(.31830989*(float)COS_LOOKUP_SZ);
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int i=vorbis_ftoi(d-.5);
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return COS_LOOKUP[i]+ (d-i)*(COS_LOOKUP[i+1]-COS_LOOKUP[i]);
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}
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/* interpolated 1./sqrt(p) where .5 <= p < 1. */
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float vorbis_invsqlook(float a){
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double d=a*(2.f*(float)INVSQ_LOOKUP_SZ)-(float)INVSQ_LOOKUP_SZ;
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int i=vorbis_ftoi(d-.5f);
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return INVSQ_LOOKUP[i]+ (d-i)*(INVSQ_LOOKUP[i+1]-INVSQ_LOOKUP[i]);
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}
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/* interpolated 1./sqrt(p) where .5 <= p < 1. */
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float vorbis_invsq2explook(int a){
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return INVSQ2EXP_LOOKUP[a-INVSQ2EXP_LOOKUP_MIN];
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}
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#include <stdio.h>
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/* interpolated lookup based fromdB function, domain -140dB to 0dB only */
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float vorbis_fromdBlook(float a){
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int i=vorbis_ftoi(a*((float)(-(1<<FROMdB2_SHIFT)))-.5f);
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return (i<0)?1.f:
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((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
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FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
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}
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#endif
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#ifdef INT_LOOKUP
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/* interpolated 1./sqrt(p) where .5 <= a < 1. (.100000... to .111111...) in
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16.16 format
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returns in m.8 format */
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long vorbis_invsqlook_i(long a,long e){
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long i=(a&0x7fff)>>(INVSQ_LOOKUP_I_SHIFT-1);
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long d=(a&INVSQ_LOOKUP_I_MASK)<<(16-INVSQ_LOOKUP_I_SHIFT); /* 0.16 */
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long val=INVSQ_LOOKUP_I[i]- /* 1.16 */
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(((INVSQ_LOOKUP_I[i]-INVSQ_LOOKUP_I[i+1])* /* 0.16 */
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d)>>16); /* result 1.16 */
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e+=32;
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if(e&1)val=(val*5792)>>13; /* multiply val by 1/sqrt(2) */
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e=(e>>1)-8;
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return(val>>e);
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}
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/* interpolated lookup based fromdB function, domain -140dB to 0dB only */
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/* a is in n.12 format */
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float vorbis_fromdBlook_i(long a){
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int i=(-a)>>(12-FROMdB2_SHIFT);
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return (i<0)?1.f:
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((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
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FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
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}
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/* interpolated lookup based cos function, domain 0 to PI only */
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/* a is in 0.16 format, where 0==0, 2^^16-1==PI, return 0.14 */
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long vorbis_coslook_i(long a){
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int i=a>>COS_LOOKUP_I_SHIFT;
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int d=a&COS_LOOKUP_I_MASK;
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return COS_LOOKUP_I[i]- ((d*(COS_LOOKUP_I[i]-COS_LOOKUP_I[i+1]))>>
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COS_LOOKUP_I_SHIFT);
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}
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#endif
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