web5design / node-web-audio-api

Node.js implementation of Web audio API

Node Web Audio API

This library implements the web audio API specification on node.js.

Why the hell doing that??? I know it sounds crazy, so I guess I'll have to build a case for it, and write some blog posts.

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

What's left to do

Most of the AudioNodes ... Most of many other things ... :(

Installation

npm install web-audio-api

Demo

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

node test/manual-testing/AudioContext-sound-output.js

Streaming audio

AudioContext just writes PCM data to a node writable stream. The default stream is a stream created with Speaker, which plays the audio back to your soundcard. But you can use any writable stream, file, including the stdin of a child process.

For example, here is an example for streaming audio to an icecast server, using ices :

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

Cool huh?

Extensions

Wow! The whole thing is not even half-done that there's already some extensions for it! See the list in the wiki.

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:

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 :

mocha

Manual testing

To test the sound output :

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.

Changelog

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