26 lines
1.1 KiB
Objective-C
26 lines
1.1 KiB
Objective-C
/*
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* Helper.c
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* CogAudio
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*
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* Created by Andre Reffhaug on 2/17/08.
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* Copyright 2008 __MyCompanyName__. All rights reserved.
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*
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*/
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#include "Helper.h"
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#include <math.h>
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// These functions are helpers for the process of converting volume from a linear to logarithmic scale.
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// Numbers that goes in to audioPlayer should be logarithmic. Numbers that are displayed to the user should be linear.
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// Here's why: http://www.dr-lex.34sp.com/info-stuff/volumecontrols.html
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// We are using the approximation of X^2 when volume is limited to 100% and X^4 when volume is limited to 800%.
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// Input/Output values are in percents.
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double logarithmicToLinear(const double logarithmic, double MAX_VOLUME) {
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return (MAX_VOLUME == 100.0) ? pow((logarithmic / MAX_VOLUME), 0.5) * 100.0 : pow((logarithmic / MAX_VOLUME), 0.25) * 100.0;
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}
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double linearToLogarithmic(const double linear, double MAX_VOLUME) {
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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;
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}
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// End helper volume function thingies. ONWARDS TO GLORY!
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