https://github.com/mohayonao/adsr-envelope

ADSREnvelope for Web Audio API
https://github.com/mohayonao/adsr-envelope

Last synced: about 1 month ago
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ADSREnvelope for Web Audio API

• Host: GitHub
• URL: https://github.com/mohayonao/adsr-envelope
• Owner: mohayonao
• Created: 2015-09-02T11:03:21.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2015-11-06T02:29:28.000Z (about 9 years ago)
• Last Synced: 2024-10-02T09:46:37.887Z (2 months ago)
• Language: JavaScript
• Homepage: http://mohayonao.github.io/adsr-envelope/
• Size: 408 KB
• Stars: 39
• Watchers: 4
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

• awesome-javascript-audio - adsr-envelope - attack, delay, sustain, release and MORE, lots of options (Sound editing / ADSR envelopes)

README

        
# ADSR ENVELOPE

[![Build Status](http://img.shields.io/travis/mohayonao/adsr-envelope.svg?style=flat-square)](https://travis-ci.org/mohayonao/adsr-envelope)

[![NPM Version](http://img.shields.io/npm/v/adsr-envelope.svg?style=flat-square)](https://www.npmjs.org/package/adsr-envelope)

[![License](http://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](http://mohayonao.mit-license.org/)

> ADSR Envelope

## Installation

Node.js

```sh

npm install adsr-envelope

```

## Online Demo

- http://mohayonao.github.io/adsr-envelope/

## ADSR

![ADSREnvelope](https://github.com/mohayonao/adsr-envelope/wiki/images/ADSREnvelope.png)

## API

### ADSREnvelope

- `constructor(opts: object = {})`

  - `attackTime: number` _default: **0.01** (10msec)_

  - `decayTime: number` _default: **0.3** (300msec)_

  - `sustainLevel: number` _default: **0.5**_

  - `releaseTime: number` _default: **1** (1sec)_

  - `gateTime: number` _default: **Infinity**_

  - `sustainTime: number`

  - `duration: number`

  - `peakLevel: number` _default: **1**_

  - `epsilon: number` _default: **0.001**_

  - `attackCurve: string` _default: **lin**_

    - **lin** or **exp** (linear or exponential)

  - `decayCurve: string` _default: **lin**_

    - **lin** or **exp** (linear or exponential)

  - `releaseCurve: string` _default: **lin**_

    - **lin** or **exp** (linear or exponential)

#### Instance Attributes

- `duration: number`

- `attackTime: number`

- `decayTime: number`

- `sustainTime: number`

- `sustainLevel: number`

- `releaseTime: number`

- `gateTime: number`

- `peakLevel: number`

- `epsilon: number`

- `attackCurve: string`

- `decayCurve: string`

- `releaseCurve: string`

#### Instance Methods

- `valueAt(time: number = 0): number`

- `applyTo(audioParam: AudioParam, playbackTime: number = 0): self`

- `getWebAudioAPIMethods(playbackTime: number = 0): Array[]`

- `clone(): ADSREnvelope`

## Example

### sequencer style

```js

import ADSREnvelope from "adsr-envelope";

let audioContext = new AudioContext();

let oscillator = audioContext.createOscillator();

let gain = audioContext.createGain();

let adsr = new ADSREnvelope({

  attackTime: 0.5,

  decayTime: 0.25,

  sustainLevel: 0.8,

  releaseTime: 2.5,

  gateTime: 6,

  releaseCurve: "exp",

});

adsr.applyTo(gain.gain, audioContext.currentTime);

console.log(adsr.getWebAudioAPIMethods());

// [

//   [ "setValueAtTime", 0, 0 ],

//   [ "linearRampToValueAtTime", 1, 0.5 ],

//   [ "linearRampToValueAtTime", 0.8, 0.75],

//   [ "setValueAtTime", 0.8, 6 ],

//   [ "exponentialRampToValueAtTime", 0.001, 8.5 ],

// ]

oscillator.start(audioContext.currentTime);

oscillator.stop(audioContext.currentTime + adsr.duration);

oscillator.connect(gain);

gain.connect(audioContext.destination);

```

### noteOn / noteOff style

```js

import ADSREnvelope from "adsr-envelope";

let audioContext = new AudioContext();

let adsr = new ADSREnvelope({

  attackTime: 0.5,

  decayTime: 0.25,

  sustainLevel: 0.8,

  releaseTime: 2.5,

  gateTime: 6,

  releaseCurve: "exp",

});

let noteMap = {};

class Note {

  constructor(audioContext, noteNumber, envelope) {

    this.audioContext = audioContext;

    this.noteNumber = noteNumber;

    this.envelope = envelope;

    this.startTime = 0;

    this.oscillator = audioContext.createOscillator();

    this.gain = audioContext.createGain();

    this.oscillator.frequency.value = midicps(noteNumber);

    this.oscillator.onended = () => {

      this.oscillator.disconnect();

      this.gain.disconnect();

    };

    this.oscillator.connect(this.gain);

    this.gain.connect(audioContext.destination);

  }

  noteOn(playbackTime = this.audioContext.currentTime) {

    this.startTime = playbackTime;

    this.envelope.gateTime = Infinity;

    this.envelope.applyTo(this.gain.gain, playbackTime);

    this.oscillator.start(playbackTime);

  }

  noteOff(playbackTime = this.audioContext.currentTime) {

    this.gain.gain.cancelScheduledValues(this.startTime);

    this.envelope.gateTime = playbackTime - this.startTime;

    this.envelope.applyTo(this.gain.gain, this.startTime);

    this.oscillator.stop(this.startTime + this.envelope.duration);

  }

}

midiKeyboard.on("noteOn", ({ noteNumber }) => {

  if (noteMap[noteNumber]) {

    noteMap[noteNumber].noteOff();

  }

  noteMap[noteNumber] = new Note(audioContext, noteNumber, adsr.clone());

  noteMap[noteNumber].noteOn();

});

midiKeyboard.on("noteOff", ({ noteNumber }) => {

  if (noteMap[noteNumber]) {

    noteMap[noteNumber].noteOff();

  }

  noteMap[noteNumber] = null;

});

```

## License

MIT