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https://github.com/audiojs/web-audio-api

Node.js implementation of Web audio API
https://github.com/audiojs/web-audio-api

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Node.js implementation of Web audio API

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# web-audio-api [![test](https://github.com/audiojs/web-audio-api/actions/workflows/test.yml/badge.svg)](https://github.com/audiojs/web-audio-api/actions/workflows/test.yml)



> Node.js implementation of Web audio API



This library implements the [Web Audio API specification](http://webaudio.github.io/web-audio-api/) (also know as WAA) on Node.js.



## What's Implemented



- [x] AudioContext (partially)

- [x] AudioParam (almost there)

- [x] AudioBufferSourceNode

- [x] ScriptProcessorNode

- [x] GainNode

- [ ] OscillatorNode

- [ ] DelayNode



## Installation



```shell

npm install --save web-audio-api

```



## Demo



Get ready, this is going to blow up your mind:



```

npm install

npm run test-speaker

```



## Audio Output



By default, **web-audio-api** doesn't play back the sound it generates. In fact, an `AudioContext` has no default output, and you need to give it a writable node stream to which it can write raw PCM audio. After creating an `AudioContext`, set its output stream like this : `audioContext.outStream = writableStream`.



### Example: Playing back sound with **node-speaker**



This is probably the simplest way to play back audio. Install **node-speaker** with `npm install speaker`, then do something like this :



```javascript

import { AudioContext } from 'web-audio-api'

import Speaker from 'speaker'



const context = new AudioContext



context.outStream = new Speaker({

  channels: context.format.numberOfChannels,

  bitDepth: context.format.bitDepth,

  sampleRate: context.sampleRate

})



// Create some audio nodes here to make some noise ...

```



### Example : playing back sound with **aplay**



Linux users can play back sound from **web-audio-api** by piping its output to [aplay](http://alsa.opensrc.org/Aplay). For this, simply send the generated sound straight to `stdout` like this :



```javascript

import { AudioContext } from 'web-audio-api'

const context = new AudioContext()



context.outStream = process.stdout



// Create some audio nodes here to make some noise ...

```



Then start your script, piping it to **aplay** like so :



```

node myScript.js | aplay -f cd

```



### Example : creating an audio stream with **icecast2**



[icecast](http://icecast.org/) is a open-source streaming server. It works great, and is very easy to setup. **icecast** accepts connections from [different source clients](http://icecast.org/apps/) which provide the sound to encode and stream. [ices](http://www.icecast.org/ices/) is a client for **icecast** which accepts raw PCM audio from its standard input, and you can send sound from **web-audio-api** to **ices** (which will send it to icecast) by simply doing :



```javascript

import { spawn } from 'child_process'

import { AudioContext } from 'web-audio-api'

 const context = new AudioContext()



var ices = spawn('ices', ['ices.xml'])

context.outStream = ices.stdin

```



A live example is available on [Sébastien's website](http://funktion.fm/#/projects/versificator-rubbish-stream)



## Using Gibber



[Gibber](https://github.com/charlieroberts/Gibber) is a great audiovisual live coding environment for the browser made by [Charlie Roberts](http://charlie-roberts.com). For audio, it uses Web Audio API, so you can run it on **web-audio-api**. First install gibber with npm :



`npm install gibber.audio.lib`



Then to you can run the following test to see that everything works:



`npm test gibber.audio.lib`



## Overall view of implementation



Each time you create an ```AudioNode``` (like for instance an ```AudioBufferSourceNode``` or a ```GainNode```), it inherits from ```DspObject``` which is in charge of two things:

- register schedule events with ```_schedule```

- compute the appropriate digital signal processing with ```_tick```



Each time you connect an ```AudioNode``` using ```source.connect(destination, output, input)``` it connects the relevant ```AudioOutput``` instances of ```source``` node to the relevant ```AudioInput``` instance of the ```destination``` node.



To instantiate all of these ```AudioNode```, you needed an overall ```AudioContext``` instance. This latter has a ```destination``` property (where the sound will flow out), instance of ```AudioDestinationNode```, which inherits from ```AudioNode```. The ```AudioContext``` instance keeps track of connections to the ```destination```. When that happens, it triggers the audio loop, calling ```_tick``` infinitely on the ```destination```, which will itself call ```_tick``` on its input ... and so forth go up on the whole audio graph.



## Running the debugger



Right now everything runs in one process, so if you set a break point in your code, there's going to be a lot of buffer underflows, and you won't be able to debug anything.



One trick is to kill the `AudioContext` right before the break point, like this:



```javascript

context[Symbol.dispose]()

debugger

```



that way the audio loop is stopped, and you can inspect your objects in peace.



## Alternatives



* [web-audio-engine](https://github.com/mohayonao/web-audio-engine) − JS implementation of web-audio-api.

* [web-audio-js](https://github.com/descriptinc/web-audio-js) − fork of web-audio-engine with extra nodes.

* [lab-sound](https://github.com/LabSound/LabSound)

* [node-audio](https://ghub.io/node-audio)

* [WAAPISim](https://github.com/g200kg/WAAPISim)

* [web-audio-api-rs](https://github.com/orottier/web-audio-api-rs)

* [node-web-audio-api](https://github.com/ircam-ismm/node-web-audio-api)



## License



MIT



🕉