web-audio-assembler

web-audio-assembler

This is not even alpha software. It's an exploration of an idea

The aim of this project is answer the question: how to convert the highly imperative web audio api into something more compatible with a functional programming approach? In fact, the first purpose of this project is to access Web Audio API from Elm lang.

The idea it's old and popular: instead of use the API, create an object with the description of what you want and let web-audio-assembler to do the work.

Requirements:

• The node graph descriptor must be JSON serializable
• Create Web Audio API modules delcaratively
• Connect modules to modules or audio params
• Update and schedule updates of those node graphs
• Allow other software (for example, audio user interfaces) to discover properties and capabilities of node graph

You can see the Live Examples or read the generated API documentation

How-to

Assemble audio nodes

Create simple nodes

Use the assemble function to create a function that returns a node:

var ac = new AudioContext()
var Assembler = require('web-audio-assembler')

var Osc = Assembler.assemble({
  node: 'oscillator',
  type: 'sine',
  frequency: 400,
  connect: '$context'
})
var osc = Osc(ac)
osc.start()

Create more complex node graphs

You can create a complex node graph by using an object. Also you can use the connect property to connect one node to the other:

var Synth = Assembler.assemble({
  name: 'microsynth',
  amp: {
    node: 'gain',
    connect: '$context'
  },
  filter: {
    node: 'filter',
    type: 'lowpass',
    frequency: '500',
    connect: 'amp'
  },
  osc: {
    node: 'oscillator',
    type: 'sine'
    connect: 'filter'
  }
})
var synth = Synth(ac)
synth.osc.start(ac.currentTime)
// or
Assembler.start(synth, ac.currentTime) // start all startable nodes (oscillators, audio sources, envelopes)
Assembler.stop(synth, ac.currentTime)  // stop all stoppable nodes
Assembler.dispoase(synth) // dispose all nodes

Schedule updates

There's a way to schedule updates in the node. You pass an array with update objects with the form { target: <node.path>, time: <relative time in secs>, ...}:

Assembler.schedule(synth, ac.currentTime, [
  { target: 'filter.frequency', value: 400, time: 0 },
  { target: 'osc', trigger: 'start', time: 0 },
  { target: 'filter.frequency', value: 400, time: 1 }
])

Notice the time value of the update events are relative to the time passed to the schedule function.

TODO

• Currently only Oscillator, Gain, BiquadFilter and Delay nodes are implemented.
• Use custom nodes generators (envelopes, for example)
• Combine node graphs
• Describe node graphs (to generate synth UIs for example)
• Add yours...

Run tests and examples

Clone this repository and run npm install && npm test. You can open the .html files of the examples directory directly (no server required).

References, links and related projects

• Web Audio API, of course: https://www.w3.org/TR/webaudio/
• clojure.spec (I'm thinking in a kind of spec of web audio)
• A standardized framework for building and including Web Audio API instrument/effect "patches": https://github.com/h5bp/lazyweb-requests/issues/82
• Flocking uses a similar approach to build synths: https://github.com/colinbdclark/flocking
• https://github.com/charlieroberts/genish.js

License

MIT License