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- /********************************************************************
- * *
- * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE. *
- * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
- * THE GNU LESSER/LIBRARY PUBLIC LICENSE, WHICH IS INCLUDED WITH *
- * THIS SOURCE. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
- * *
- * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2000 *
- * by Monty <monty@xiph.org> and the XIPHOPHORUS Company *
- * http://www.xiph.org/ *
- * *
- ********************************************************************
- function: linear scale -> dB, Bark and Mel scales
- last mod: $Id: scales.h,v 1.6.2.1 2000/11/04 06:21:45 xiphmont Exp $
- ********************************************************************/
- #ifndef _V_SCALE_H_
- #define _V_SCALES_H_
- #include <math.h>
- /* 20log10(x) */
- #define DYNAMIC_RANGE_dB 200.
- #define todB(x) ((x)==0?-9.e38:log(fabs(x))*8.6858896)
- #define todB_nn(x) ((x)==0?-9.e38:log(x)*8.6858896)
- #define fromdB(x) (exp((x)*.11512925))
- /* 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(f) (13.1*atan(.00074*(f))+2.24*atan((f)*(f)*1.85e-8)+1e-4*(f))
- #define fromBARK(z) (102.*(z)-2.*pow(z,2.)+.4*pow(z,3)+pow(1.46,z)-1.)
- #define toMEL(f) (log(1.+(f)*.001)*1442.695)
- #define fromMEL(m) (1000.*exp((m)/1442.695)-1000.)
- /* Frequency to octave. We arbitrarily declare 125.0 Hz to be octave
- 0.0 */
- #define toOC(f) (log(f)*1.442695-6.965784)
- #define fromOC(o) (exp(((o)+6.965784)*.693147))
- #endif
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