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/********************************************************************
* *
* THIS FILE IS PART OF THE Ogg Vorbis SOFTWARE CODEC SOURCE CODE. *
* USE, DISTRIBUTION AND REPRODUCTION OF THIS SOURCE IS GOVERNED BY *
* THE GNU PUBLIC LICENSE 2, WHICH IS INCLUDED WITH THIS SOURCE. *
* PLEASE READ THESE TERMS DISTRIBUTING. *
* *
* THE OggSQUISH SOURCE CODE IS (C) COPYRIGHT 1994-2000 *
* by Monty <monty@xiph.org> and The XIPHOPHORUS Company *
* http://www.xiph.org/ *
* *
********************************************************************
function: linear x scale -> log x scale mappings (with bias)
last mod: $Id: xlogmap.h,v 1.2 1999/12/30 07:26:57 xiphmont Exp $
********************************************************************/
#ifndef _V_XLOGMAP_H_
#define _V_XLOGMAP_H_
#include <math.h>
/*
Bias = log_2( n / ( (2^octaves) - 1))
log_x = log_2( linear_x + 2^Bias ) - Bias
linear_x = 2^(Bias+log_x)-2^Bias;
*/
#define LOG_BIAS(n,o) (log((n)/(pow(2.,(o))-1))/log(2.))
#define LOG_X(x,b) (log((x)+pow(2.,(b)))/log(2.)-(b))
#define LINEAR_X(x,b) (pow(2.,((b)+(x)))-pow(2.,(b)))
#endif
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