robert@464: //
robert@464: //  ADSR.cpp
robert@464: //
robert@464: //  Created by Nigel Redmon on 12/18/12.
robert@464: //  EarLevel Engineering: earlevel.com
robert@464: //  Copyright 2012 Nigel Redmon
robert@464: //
robert@464: //  For a complete explanation of the ADSR envelope generator and code,
robert@464: //  read the series of articles by the author, starting here:
robert@464: //  http://www.earlevel.com/main/2013/06/01/envelope-generators/
robert@464: //
robert@464: //  License:
robert@464: //
robert@464: //  This source code is provided as is, without warranty.
robert@464: //  You may copy and distribute verbatim copies of this document.
robert@464: //  You may modify and use this source code to create binary code for your own purposes, free or commercial.
robert@464: //
robert@464: 
robert@464: #include "ADSR.h"
robert@464: #include <math.h>
robert@464: 
robert@464: 
robert@464: ADSR::ADSR(void) {
robert@464:     reset();
robert@464:     setAttackRate(0);
robert@464:     setDecayRate(0);
robert@464:     setReleaseRate(0);
robert@464:     setSustainLevel(1.0);
robert@464:     setTargetRatioA(0.3);
robert@464:     setTargetRatioDR(0.0001);
robert@464: }
robert@464: 
robert@464: ADSR::~ADSR(void) {
robert@464: }
robert@464: 
robert@464: void ADSR::setAttackRate(float rate) {
robert@464:     attackRate = rate;
robert@464:     attackCoef = calcCoef(rate, targetRatioA);
robert@464:     attackBase = (1.0 + targetRatioA) * (1.0 - attackCoef);
robert@464: }
robert@464: 
robert@464: void ADSR::setDecayRate(float rate) {
robert@464:     decayRate = rate;
robert@464:     decayCoef = calcCoef(rate, targetRatioDR);
robert@464:     decayBase = (sustainLevel - targetRatioDR) * (1.0 - decayCoef);
robert@464: }
robert@464: 
robert@464: void ADSR::setReleaseRate(float rate) {
robert@464:     releaseRate = rate;
robert@464:     releaseCoef = calcCoef(rate, targetRatioDR);
robert@464:     releaseBase = -targetRatioDR * (1.0 - releaseCoef);
robert@464: }
robert@464: 
robert@464: float ADSR::calcCoef(float rate, float targetRatio) {
robert@464:     return exp(-log((1.0 + targetRatio) / targetRatio) / rate);
robert@464: }
robert@464: 
robert@464: void ADSR::setSustainLevel(float level) {
robert@464:     sustainLevel = level;
robert@464:     decayBase = (sustainLevel - targetRatioDR) * (1.0 - decayCoef);
robert@464: }
robert@464: 
robert@464: void ADSR::setTargetRatioA(float targetRatio) {
robert@464:     if (targetRatio < 0.000000001)
robert@464:         targetRatio = 0.000000001;  // -180 dB
robert@464:     targetRatioA = targetRatio;
robert@464:     attackBase = (1.0 + targetRatioA) * (1.0 - attackCoef);
robert@464: }
robert@464: 
robert@464: void ADSR::setTargetRatioDR(float targetRatio) {
robert@464:     if (targetRatio < 0.000000001)
robert@464:         targetRatio = 0.000000001;  // -180 dB
robert@464:     targetRatioDR = targetRatio;
robert@464:     decayBase = (sustainLevel - targetRatioDR) * (1.0 - decayCoef);
robert@464:     releaseBase = -targetRatioDR * (1.0 - releaseCoef);
robert@464: }