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1 #pragma once
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2
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3 namespace collidoscope {
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4
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5
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6 /*
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7 * An ASR envelope with linear shape. It is modeled after the STK envelope classes.
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8 * The tick() method advances the computation of the envelope one sample and returns the computed sample
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9 * The class is templated for the type of the samples that each tick of the envelope produces.
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10 *
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11 * Client classes can set/get the current state of the envelope with the
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12 * respective getter/setter methods
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13 *
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14 */
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15 template <typename T>
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16 class EnvASR
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17 {
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18 public:
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19
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20 /** Possible states of the envelope. Idle means the envelope ouputs 0 */
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21 enum class State {
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22 eAttack,
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23 eSustain,
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24 eRelease,
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25 eIdle // before attack after release
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26 };
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27
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28 EnvASR( T sustainLevel, T attackTime, T releaseTime, std::size_t sampleRate ) :
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29 mSustainLevel( sustainLevel ),
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30 mState( State::eIdle ),
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31 mValue( 0 )
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32
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33 {
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34 if ( attackTime <= 0 )
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35 attackTime = T( 0.001 );
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36
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37 if ( releaseTime <= 0 )
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38 releaseTime = T( 0.001 );
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39
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40 mAttackRate = T( 1.0 ) / (attackTime * sampleRate);
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41 mReleaseRate = T( 1.0 ) / (releaseTime * sampleRate);
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42 }
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43
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44 /** Produces one sample worth of envelope */
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45 T tick()
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46 {
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47
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48 switch ( mState )
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49 {
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50
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51 case State::eIdle: {
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52 mValue = 0;
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53 };
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54 break;
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55
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56 case State::eAttack: {
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57 mValue += mAttackRate;
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58 if ( mValue >= mSustainLevel ){
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59 mValue = mSustainLevel;
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60 mState = State::eSustain;
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61 }
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62 };
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63 break;
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64
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65 case State::eRelease:
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66 mValue -= mReleaseRate;
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67 if ( mValue <= 0 ){
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68 mValue = 0;
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69 mState = State::eIdle;
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70 }
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71 break;
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72 default:
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73 break;
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74 }
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75
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76 return mValue;
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77
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78 }
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79
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80 State getState() const
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81 {
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82 return mState;
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83 }
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84
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85 void setState( State state )
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86 {
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87 mState = state;
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88 }
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89
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90 private:
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91 T mSustainLevel;
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92 T mAttackRate;
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93 T mReleaseRate;
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94
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95 // output
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96 T mValue;
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97
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98 State mState;
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99
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100 };
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101
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102
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103 }
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