cog/Audio/Helper.m

/*
 *  Helper.c
 *  CogAudio
 *
 *  Created by Andre Reffhaug on 2/17/08.
 *  Copyright 2008 __MyCompanyName__. All rights reserved.
 *
 */

#include "Helper.h"
#include <math.h>

// These functions are helpers for the process of converting volume from a linear to logarithmic scale.
// Numbers that goes in to audioPlayer should be logarithmic. Numbers that are displayed to the user should be linear.
// Here's why: http://www.dr-lex.34sp.com/info-stuff/volumecontrols.html
// We are using the approximation of X^2 when volume is limited to 100% and X^4 when volume is limited to 800%.
// Input/Output values are in percents.
double logarithmicToLinear(const double logarithmic, double MAX_VOLUME) {
	return (MAX_VOLUME == 100.0) ? pow((logarithmic / MAX_VOLUME), 0.5) * 100.0 : pow((logarithmic / MAX_VOLUME), 0.25) * 100.0;
}

double linearToLogarithmic(const double linear, double MAX_VOLUME) {
	return (MAX_VOLUME == 100.0) ? (linear / 100.0) * (linear / 100.0) * MAX_VOLUME : (linear / 100.0) * (linear / 100.0) * (linear / 100.0) * (linear / 100.0) * MAX_VOLUME;
}
// End helper volume function thingies. ONWARDS TO GLORY!