1 /********************************************************************
3 * THIS FILE IS PART OF THE Ogg Vorbis SOFTWARE CODEC SOURCE CODE. *
4 * USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
5 * THE GNU PUBLIC LICENSE 2, WHICH IS INCLUDED WITH THIS SOURCE. *
6 * PLEASE READ THESE TERMS DISTRIBUTING. *
8 * THE OggSQUISH SOURCE CODE IS (C) COPYRIGHT 1994-2000 *
9 * by Monty <monty@xiph.org> and The XIPHOPHORUS Company *
10 * http://www.xiph.org/ *
12 ********************************************************************
14 function: linear scale -> dB, Bark and Mel scales
15 last mod: $Id: scales.h,v 1.6 2000/10/12 03:12:54 xiphmont Exp $
17 ********************************************************************/
25 #define DYNAMIC_RANGE_dB 200.
26 #define todB(x) ((x)==0?-9.e38:log(fabs(x))*8.6858896)
27 #define todB_nn(x) ((x)==0?-9.e38:log(x)*8.6858896)
28 #define fromdB(x) (exp((x)*.11512925))
31 /* The bark scale equations are approximations, since the original
32 table was somewhat hand rolled. The below are chosen to have the
33 best possible fit to the rolled tables, thus their somewhat odd
34 appearance (these are more accurate and over a longer range than
35 the oft-quoted bark equations found in the texts I have). The
36 approximations are valid from 0 - 30kHz (nyquist) or so.
38 all f in Hz, z in Bark */
40 #define toBARK(f) (13.1*atan(.00074*(f))+2.24*atan((f)*(f)*1.85e-8)+1e-4*(f))
41 #define fromBARK(z) (102.*(z)-2.*pow(z,2.)+.4*pow(z,3)+pow(1.46,z)-1.)
42 #define toMEL(f) (log(1.+(f)*.001)*1442.695)
43 #define fromMEL(m) (1000.*exp((m)/1442.695)-1000.)
45 /* Frequency to octave. We arbitrarily declare 125.0 Hz to be octave
48 #define toOC(f) (log(f)*1.442695-6.965784)
49 #define fromOC(o) (exp(((o)+6.965784)*.693147))