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1 /*
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2
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3 Copyright (C) 2016 Queen Mary University of London
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4 Author: Fiore Martin
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5
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6 This file is part of Collidoscope.
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7
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8 Collidoscope is free software: you can redistribute it and/or modify
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9 it under the terms of the GNU General Public License as published by
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10 the Free Software Foundation, either version 3 of the License, or
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11 (at your option) any later version.
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12
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13 This program is distributed in the hope that it will be useful,
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14 but WITHOUT ANY WARRANTY; without even the implied warranty of
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15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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16 GNU General Public License for more details.
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17
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18 You should have received a copy of the GNU General Public License
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19 along with this program. If not, see <http://www.gnu.org/licenses/>.
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20 */
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21
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22 #pragma once
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23
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24 namespace collidoscope {
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25
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26
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27 /*
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28 * An ASR envelope with linear shape. It is modeled after the STK envelope classes.
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29 * The tick() method advances the computation of the envelope one sample and returns the computed sample
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30 * The class is templated for the type of the samples that each tick of the envelope produces.
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31 *
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32 * Client classes can set/get the current state of the envelope with the
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33 * respective getter/setter methods
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34 *
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35 */
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36 template <typename T>
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37 class EnvASR
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38 {
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39 public:
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40
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41 /** Possible states of the envelope. Idle means the envelope ouputs 0 */
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42 enum class State {
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43 eAttack,
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44 eSustain,
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45 eRelease,
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46 eIdle // before attack after release
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47 };
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48
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49 EnvASR( T sustainLevel, T attackTime, T releaseTime, std::size_t sampleRate ) :
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50 mSustainLevel( sustainLevel ),
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51 mState( State::eIdle ),
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52 mValue( 0 )
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53
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54 {
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55 if ( attackTime <= 0 )
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56 attackTime = T( 0.001 );
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57
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58 if ( releaseTime <= 0 )
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59 releaseTime = T( 0.001 );
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60
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61 mAttackRate = T( 1.0 ) / (attackTime * sampleRate);
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62 mReleaseRate = T( 1.0 ) / (releaseTime * sampleRate);
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63 }
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64
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65 /** Produces one sample worth of envelope */
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66 T tick()
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67 {
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68
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69 switch ( mState )
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70 {
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71
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72 case State::eIdle: {
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73 mValue = 0;
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74 };
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75 break;
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76
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77 case State::eAttack: {
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78 mValue += mAttackRate;
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79 if ( mValue >= mSustainLevel ){
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80 mValue = mSustainLevel;
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81 mState = State::eSustain;
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82 }
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83 };
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84 break;
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85
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86 case State::eRelease:
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87 mValue -= mReleaseRate;
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88 if ( mValue <= 0 ){
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89 mValue = 0;
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90 mState = State::eIdle;
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91 }
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92 break;
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93 default:
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94 break;
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95 }
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96
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97 return mValue;
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98
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99 }
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100
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101 State getState() const
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102 {
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103 return mState;
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104 }
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105
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106 void setState( State state )
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107 {
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108 mState = state;
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109 }
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110
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111 private:
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112 T mSustainLevel;
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113 T mAttackRate;
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114 T mReleaseRate;
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115
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116 // output
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117 T mValue;
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118
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119 State mState;
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120
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121 };
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122
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123
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124 }
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