media/libvorbis/lib/scales.h
 author David Anderson Thu, 05 Jan 2012 13:49:23 -0800 changeset 112384 47b0a1dab4d23d9d8a6ff38cdcb4f0ba4b735b7b parent 31034 c6692a8f3f2725faadef43edd3142e533b452e62 child 415560 6ac27d7a3fe4fafb98e93e84739e8205900b5298 permissions -rw-r--r--
Follow-up nits to bug 714393.
```
/********************************************************************
*                                                                  *
* THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
*                                                                  *
* THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009             *
* by the Xiph.Org Foundation http://www.xiph.org/                  *
*                                                                  *
********************************************************************

function: linear scale -> dB, Bark and Mel scales
last mod: \$Id: scales.h 16227 2009-07-08 06:58:46Z xiphmont \$

********************************************************************/

#ifndef _V_SCALES_H_
#define _V_SCALES_H_

#include <math.h>
#include "os.h"

#ifdef _MSC_VER
/* MS Visual Studio doesn't have C99 inline keyword. */
#define inline __inline
#endif

/* 20log10(x) */
#define VORBIS_IEEE_FLOAT32 1
#ifdef VORBIS_IEEE_FLOAT32

static inline float unitnorm(float x){
union {
ogg_uint32_t i;
float f;
} ix;
ix.f = x;
ix.i = (ix.i & 0x80000000U) | (0x3f800000U);
return ix.f;
}

/* Segher was off (too high) by ~ .3 decibel.  Center the conversion correctly. */
static inline float todB(const float *x){
union {
ogg_uint32_t i;
float f;
} ix;
ix.f = *x;
ix.i = ix.i&0x7fffffff;
return (float)(ix.i * 7.17711438e-7f -764.6161886f);
}

#define todB_nn(x) todB(x)

#else

static float unitnorm(float x){
if(x<0)return(-1.f);
return(1.f);
}

#define todB(x)   (*(x)==0?-400.f:log(*(x)**(x))*4.34294480f)
#define todB_nn(x)   (*(x)==0.f?-400.f:log(*(x))*8.6858896f)

#endif

#define fromdB(x) (exp((x)*.11512925f))

/* The bark scale equations are approximations, since the original
table was somewhat hand rolled.  The below are chosen to have the
best possible fit to the rolled tables, thus their somewhat odd
appearance (these are more accurate and over a longer range than
the oft-quoted bark equations found in the texts I have).  The
approximations are valid from 0 - 30kHz (nyquist) or so.

all f in Hz, z in Bark */

#define toBARK(n)   (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
#define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
#define toMEL(n)    (log(1.f+(n)*.001f)*1442.695f)
#define fromMEL(m)  (1000.f*exp((m)/1442.695f)-1000.f)

/* Frequency to octave.  We arbitrarily declare 63.5 Hz to be octave
0.0 */

#define toOC(n)     (log(n)*1.442695f-5.965784f)
#define fromOC(o)   (exp(((o)+5.965784f)*.693147f))

#endif
```