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source: downloads/libvorbis-1.2.0/lib/scales.h @ 52

Last change on this file since 52 was 16, checked in by landauf, 17 years ago

added libvorbis

File size: 2.6 KB
Line 
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 1994-2007             *
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 13293 2007-07-24 00:09:47Z 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/* 20log10(x) */
25#define VORBIS_IEEE_FLOAT32 1
26#ifdef VORBIS_IEEE_FLOAT32
27
28static float unitnorm(float x){
29  union {
30    ogg_uint32_t i;
31    float f;
32  } ix;
33  ix.f = x;
34  ix.i = (ix.i & 0x80000000U) | (0x3f800000U);
35  return ix.f;
36}
37
38/* Segher was off (too high) by ~ .3 decibel.  Center the conversion correctly. */
39static float todB(const float *x){
40  union {
41    ogg_uint32_t i;
42    float f;
43  } ix;
44  ix.f = *x;
45  ix.i = ix.i&0x7fffffff;
46  return (float)(ix.i * 7.17711438e-7f -764.6161886f);
47}
48
49#define todB_nn(x) todB(x)
50
51#else
52
53static float unitnorm(float x){
54  if(x<0)return(-1.f);
55  return(1.f);
56}
57
58#define todB(x)   (*(x)==0?-400.f:log(*(x)**(x))*4.34294480f)
59#define todB_nn(x)   (*(x)==0.f?-400.f:log(*(x))*8.6858896f)
60
61#endif
62
63#define fromdB(x) (exp((x)*.11512925f)) 
64
65/* The bark scale equations are approximations, since the original
66   table was somewhat hand rolled.  The below are chosen to have the
67   best possible fit to the rolled tables, thus their somewhat odd
68   appearance (these are more accurate and over a longer range than
69   the oft-quoted bark equations found in the texts I have).  The
70   approximations are valid from 0 - 30kHz (nyquist) or so.
71
72   all f in Hz, z in Bark */
73
74#define toBARK(n)   (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
75#define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
76#define toMEL(n)    (log(1.f+(n)*.001f)*1442.695f)
77#define fromMEL(m)  (1000.f*exp((m)/1442.695f)-1000.f)
78
79/* Frequency to octave.  We arbitrarily declare 63.5 Hz to be octave
80   0.0 */
81
82#define toOC(n)     (log(n)*1.442695f-5.965784f)
83#define fromOC(o)   (exp(((o)+5.965784f)*.693147f))
84
85#endif
86
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