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scales.h (2761B)

      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 https://xiph.org/                     *
     10 *                                                                  *
     11 ********************************************************************
     12 
     13 function: linear scale -> dB, Bark and Mel scales
     14 
     15 ********************************************************************/
     16 
     17 #ifndef _V_SCALES_H_
     18 #define _V_SCALES_H_
     19 
     20 #include <math.h>
     21 #include "os.h"
     22 
     23 #ifdef _MSC_VER
     24 /* MS Visual Studio doesn't have C99 inline keyword. */
     25 #define inline __inline
     26 #endif
     27 
     28 /* 20log10(x) */
     29 #define VORBIS_IEEE_FLOAT32 1
     30 #ifdef VORBIS_IEEE_FLOAT32
     31 
     32 static inline float unitnorm(float x){
     33  union {
     34    ogg_uint32_t i;
     35    float f;
     36  } ix;
     37  ix.f = x;
     38  ix.i = (ix.i & 0x80000000U) | (0x3f800000U);
     39  return ix.f;
     40 }
     41 
     42 /* Segher was off (too high) by ~ .3 decibel.  Center the conversion correctly. */
     43 static inline float todB(const float *x){
     44  union {
     45    ogg_uint32_t i;
     46    float f;
     47  } ix;
     48  ix.f = *x;
     49  ix.i = ix.i&0x7fffffff;
     50  return (float)(ix.i * 7.17711438e-7f -764.6161886f);
     51 }
     52 
     53 #define todB_nn(x) todB(x)
     54 
     55 #else
     56 
     57 static float unitnorm(float x){
     58  if(x<0)return(-1.f);
     59  return(1.f);
     60 }
     61 
     62 #define todB(x)   (*(x)==0?-400.f:log(*(x)**(x))*4.34294480f)
     63 #define todB_nn(x)   (*(x)==0.f?-400.f:log(*(x))*8.6858896f)
     64 
     65 #endif
     66 
     67 #define fromdB(x) (exp((x)*.11512925f))
     68 
     69 /* The bark scale equations are approximations, since the original
     70   table was somewhat hand rolled.  The below are chosen to have the
     71   best possible fit to the rolled tables, thus their somewhat odd
     72   appearance (these are more accurate and over a longer range than
     73   the oft-quoted bark equations found in the texts I have).  The
     74   approximations are valid from 0 - 30kHz (nyquist) or so.
     75 
     76   all f in Hz, z in Bark */
     77 
     78 #define toBARK(n)   (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
     79 #define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
     80 #define toMEL(n)    (log(1.f+(n)*.001f)*1442.695f)
     81 #define fromMEL(m)  (1000.f*exp((m)/1442.695f)-1000.f)
     82 
     83 /* Frequency to octave.  We arbitrarily declare 63.5 Hz to be octave
     84   0.0 */
     85 
     86 #define toOC(n)     (log(n)*1.442695f-5.965784f)
     87 #define fromOC(o)   (exp(((o)+5.965784f)*.693147f))
     88 
     89 #endif