90 lines
2.7 KiB
C
90 lines
2.7 KiB
C
/********************************************************************
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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 https://xiph.org/ *
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* *
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********************************************************************
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function: linear scale -> dB, Bark and Mel scales
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********************************************************************/
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#ifndef _V_SCALES_H_
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#define _V_SCALES_H_
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#include <math.h>
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#include "os.h"
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#ifdef _MSC_VER
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/* MS Visual Studio doesn't have C99 inline keyword. */
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#define inline __inline
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#endif
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/* 20log10(x) */
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#define VORBIS_IEEE_FLOAT32 1
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#ifdef VORBIS_IEEE_FLOAT32
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static inline float unitnorm(float x){
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union {
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ogg_uint32_t i;
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float f;
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} ix;
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ix.f = x;
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ix.i = (ix.i & 0x80000000U) | (0x3f800000U);
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return ix.f;
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}
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/* Segher was off (too high) by ~ .3 decibel. Center the conversion correctly. */
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static inline float todB(const float *x){
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union {
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ogg_uint32_t i;
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float f;
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} ix;
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ix.f = *x;
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ix.i = ix.i&0x7fffffff;
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return (float)(ix.i * 7.17711438e-7f -764.6161886f);
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}
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#define todB_nn(x) todB(x)
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#else
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static float unitnorm(float x){
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if(x<0)return(-1.f);
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return(1.f);
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}
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#define todB(x) (*(x)==0?-400.f:log(*(x)**(x))*4.34294480f)
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#define todB_nn(x) (*(x)==0.f?-400.f:log(*(x))*8.6858896f)
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#endif
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#define fromdB(x) (exp((x)*.11512925f))
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/* The bark scale equations are approximations, since the original
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table was somewhat hand rolled. The below are chosen to have the
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best possible fit to the rolled tables, thus their somewhat odd
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appearance (these are more accurate and over a longer range than
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the oft-quoted bark equations found in the texts I have). The
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approximations are valid from 0 - 30kHz (nyquist) or so.
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all f in Hz, z in Bark */
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#define toBARK(n) (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
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#define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
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#define toMEL(n) (log(1.f+(n)*.001f)*1442.695f)
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#define fromMEL(m) (1000.f*exp((m)/1442.695f)-1000.f)
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/* Frequency to octave. We arbitrarily declare 63.5 Hz to be octave
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0.0 */
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#define toOC(n) (log(n)*1.442695f-5.965784f)
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#define fromOC(o) (exp(((o)+5.965784f)*.693147f))
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#endif
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