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MidiSynth / src / com.example.android.common.midi / synth /

EnvelopeADSR.java

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/*
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 * Copyright (C) 2015 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.common.midi.synth;
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/**
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 * Very simple Attack, Decay, Sustain, Release envelope with linear ramps.
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 *
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 * Times are in seconds.
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 */
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public class EnvelopeADSR extends SynthUnit {
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    private static final int IDLE = 0;
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    private static final int ATTACK = 1;
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    private static final int DECAY = 2;
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    private static final int SUSTAIN = 3;
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    private static final int RELEASE = 4;
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    private static final int FINISHED = 5;
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    private static final float MIN_TIME = 0.001f;
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    private float mAttackRate;
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    private float mRreleaseRate;
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    private float mSustainLevel;
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    private float mDecayRate;
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    private float mCurrent;
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    private int mSstate = IDLE;
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    public EnvelopeADSR() {
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        setAttackTime(0.003f);
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        setDecayTime(0.08f);
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        setSustainLevel(0.3f);
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        setReleaseTime(1.0f);
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    }
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    public void setAttackTime(float time) {
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        if (time < MIN_TIME)
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            time = MIN_TIME;
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        mAttackRate = 1.0f / (SynthEngine.FRAME_RATE * time);
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    }
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    public void setDecayTime(float time) {
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        if (time < MIN_TIME)
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            time = MIN_TIME;
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        mDecayRate = 1.0f / (SynthEngine.FRAME_RATE * time);
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    }
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    public void setSustainLevel(float level) {
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        if (level < 0.0f)
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            level = 0.0f;
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        mSustainLevel = level;
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    }
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    public void setReleaseTime(float time) {
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        if (time < MIN_TIME)
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            time = MIN_TIME;
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        mRreleaseRate = 1.0f / (SynthEngine.FRAME_RATE * time);
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    }
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    public void on() {
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        mSstate = ATTACK;
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    }
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    public void off() {
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        mSstate = RELEASE;
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    }
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    @Override
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    public float render() {
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        switch (mSstate) {
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        case ATTACK:
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            mCurrent += mAttackRate;
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            if (mCurrent > 1.0f) {
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                mCurrent = 1.0f;
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                mSstate = DECAY;
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            }
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            break;
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        case DECAY:
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            mCurrent -= mDecayRate;
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            if (mCurrent < mSustainLevel) {
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                mCurrent = mSustainLevel;
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                mSstate = SUSTAIN;
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            }
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            break;
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        case RELEASE:
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            mCurrent -= mRreleaseRate;
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            if (mCurrent < 0.0f) {
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                mCurrent = 0.0f;
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                mSstate = FINISHED;
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            }
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            break;
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        }
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        return mCurrent;
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    }
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    public boolean isDone() {
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        return mSstate == FINISHED;
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    }
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}
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