1 /********************************************************************
3 * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE. *
4 * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
5 * THE GNU LESSER/LIBRARY PUBLIC LICENSE, WHICH IS INCLUDED WITH *
6 * THIS SOURCE. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
8 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2001 *
9 * by the XIPHOPHORUS Company http://www.xiph.org/ *
11 ********************************************************************
13 function: linear scale -> dB, Bark and Mel scales
14 last mod: $Id: scales.h,v 1.12 2001/02/02 03:51:57 xiphmont Exp $
16 ********************************************************************/
24 #define DYNAMIC_RANGE_dB 200.f
25 #define todB(x) ((x)==0?-400.f:log((x)*(x))*4.34294480f)
26 #define todB_nn(x) ((x)==0.f?-400.f:log(x)*8.6858896f)
27 #define fromdB(x) (exp((x)*.11512925f))
29 /* The bark scale equations are approximations, since the original
30 table was somewhat hand rolled. The below are chosen to have the
31 best possible fit to the rolled tables, thus their somewhat odd
32 appearance (these are more accurate and over a longer range than
33 the oft-quoted bark equations found in the texts I have). The
34 approximations are valid from 0 - 30kHz (nyquist) or so.
36 all f in Hz, z in Bark */
38 #define toBARK(n) (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
39 #define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
40 #define toMEL(n) (log(1.f+(n)*.001f)*1442.695f)
41 #define fromMEL(m) (1000.f*exp((m)/1442.695f)-1000.f)
43 /* Frequency to octave. We arbitrarily declare 63.5 Hz to be octave
46 #define toOC(n) (log(n)*1.442695f-5.965784f)
47 #define fromOC(o) (exp(((o)+5.965784f)*.693147f))