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view libs/vorbis/scales.h @ 1:e7ca128b8713

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looks nice :)
author John Tsiombikas <nuclear@member.fsf.org>
date Sun, 02 Feb 2014 00:35:22 +0200
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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: linear scale -> dB, Bark and Mel scales
14 last mod: $Id: scales.h 16227 2009-07-08 06:58:46Z xiphmont $
15
16 ********************************************************************/
17
18 #ifndef _V_SCALES_H_
19 #define _V_SCALES_H_
20
21 #include <math.h>
22 #include "os.h"
23
24 #ifdef _MSC_VER
25 /* MS Visual Studio doesn't have C99 inline keyword. */
26 #define inline __inline
27 #endif
28
29 /* 20log10(x) */
30 #define VORBIS_IEEE_FLOAT32 1
31 #ifdef VORBIS_IEEE_FLOAT32
32
33 static inline float unitnorm(float x){
34 union {
35 ogg_uint32_t i;
36 float f;
37 } ix;
38 ix.f = x;
39 ix.i = (ix.i & 0x80000000U) | (0x3f800000U);
40 return ix.f;
41 }
42
43 /* Segher was off (too high) by ~ .3 decibel. Center the conversion correctly. */
44 static inline float todB(const float *x){
45 union {
46 ogg_uint32_t i;
47 float f;
48 } ix;
49 ix.f = *x;
50 ix.i = ix.i&0x7fffffff;
51 return (float)(ix.i * 7.17711438e-7f -764.6161886f);
52 }
53
54 #define todB_nn(x) todB(x)
55
56 #else
57
58 static float unitnorm(float x){
59 if(x<0)return(-1.f);
60 return(1.f);
61 }
62
63 #define todB(x) (*(x)==0?-400.f:log(*(x)**(x))*4.34294480f)
64 #define todB_nn(x) (*(x)==0.f?-400.f:log(*(x))*8.6858896f)
65
66 #endif
67
68 #define fromdB(x) (exp((x)*.11512925f))
69
70 /* The bark scale equations are approximations, since the original
71 table was somewhat hand rolled. The below are chosen to have the
72 best possible fit to the rolled tables, thus their somewhat odd
73 appearance (these are more accurate and over a longer range than
74 the oft-quoted bark equations found in the texts I have). The
75 approximations are valid from 0 - 30kHz (nyquist) or so.
76
77 all f in Hz, z in Bark */
78
79 #define toBARK(n) (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
80 #define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
81 #define toMEL(n) (log(1.f+(n)*.001f)*1442.695f)
82 #define fromMEL(m) (1000.f*exp((m)/1442.695f)-1000.f)
83
84 /* Frequency to octave. We arbitrarily declare 63.5 Hz to be octave
85 0.0 */
86
87 #define toOC(n) (log(n)*1.442695f-5.965784f)
88 #define fromOC(o) (exp(((o)+5.965784f)*.693147f))
89
90 #endif