web-audio-api

Node Web Audio API ===================== [![Build Status](https://travis-ci.org/sebpiq/node-web-audio-api.svg)](https://travis-ci.org/sebpiq/node-web-audio-api) [![Dependency Status](https://img.shields.io/gemnasium/sebpiq/node-web-audio-api.svg)](https://gemnasium.com/sebpiq/node-web-audio-api) [![Join the chat at https://gitter.im/sebpiq/node-web-audio-api](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/sebpiq/node-web-audio-api?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) This library implements the [web audio API specification](http://webaudio.github.io/web-audio-api/) on node.js. And this is not even alpha. Use this library only if you're the adventurous kind. What's implemented ------------------- - AudioContext(partially) - AudioParam (almost there) - AudioBufferSourceNode - ScriptProcessorNode - GainNode - OscillatorNode (coming soon) - DelayNode (coming soon) Installation -------------- ``` npm install web-audio-api ``` Demo ------ Get ready, this is going to blow up your mind : ``` npm install gulp default node test/manual-testing/AudioContext-sound-output.js ``` Audio output ----------------- By default, **node-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 var AudioContext = require('web-audio-api').AudioContext , context = new AudioContext , Speaker = require('speaker') 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 **node-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 var AudioContext = require('web-audio-api').AudioContext , 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 **node-web-audio-api** to **ices** (which will send it to icecast) by simply doing : ``` var spawn = require('child_process').spawn , AudioContext = require('web-audio-api').AudioContext , 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 **node-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 the 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._kill() debugger ``` that way the audio loop is stopped, and you can inspect your objects in peace. Running the tests ------------------ Tests are written with mocha. To run them, install mocha with : ``` npm install -g mocha ``` And in the root folder run : ``` npm test ``` Manual testing ---------------- To test the sound output, we need to install `node-speaker` (in addition of all the other dependencies), and build the library : ``` npm install npm install speaker gulp default node test/manual-testing/AudioContext-sound-output.js ``` To test `AudioParam` against `AudioParam` implemented in a browser, open `test/manual-testing/AudioParam-browser-plots.html` in that browser. Contributors ------------- ``` 61 Sébastien Piquemal 16 ouhouhsami 4 John Wnek 2 anprogrammer 1 Andrew Petersen ``` Changelog ----------- #### 0.2.2 - removed `node-speaker` and `mathjs` dependencies #### 0.2.1 - now use aurora installed from npm instead of distributing a built version of it. #### 0.2.0 - refactored to ES6 #### 0.1.5 - **AudioNode** and **AudioContext** bug fixes #### 0.1.4 - **audioports** : bug fixes #### 0.1.3 - **audioports** : implemented `channelInterpretation` 'speakers' - **AudioContext** : added support for mp3 to `decodeAudioData` #### 0.1.2 - **AudioBufferSourceNode** : handler `onended` implemented - **AudioContext** : method `decodeAudioData`, support only for wav #### 0.1.1 - **ScriptProcessorNode** - **AudioBufferSourceNode** - node is killed once it has finished playing - subsequent calls to `start` have no effect - **AudioContext** : method `collectNodes` - **audioports** : bug fixes #### 0.1.0 - **AudioContext** (partial implementation) - **AudioParam** (missing unschedule) - **AudioBufferSourceNode** (missing onended) - **GainNode**