microphone

Tiny coffeescript/javascript library to process live audio input in the browser. Right now, this only works in Chrome.

I created this to make it easy to perform arbitrary computations using raw, streaming audio data.

A Microphone object takes two parameters- settings and a callback.

• settings:
  • unit: the length (in seconds) of audio to return in each callback (default: 1)
  • overlap: the amount of overlap in the audio data between successive callbacks (For example, overlap of .25 means the last 25% of the audio data from one callback will be the first 25% of the data in the next callback). (default: 0. Must be between 0 and 1, inclusive)
  • channels: 1 (mono) or 2 (stereo) (default: 1)
• callback: A function that takes an array with dimensions 2x(unit * recording sample rate) if stereo, and just (unit * recording sample rate) if mono. The callback will be called every (unit * (1 - overlap)) seconds.

Usage

Example: compute the RMS energy every half second with 50% overlap

Coffeescript:

mic = new Microphone unit: .5, overlap: .5, (data) ->
    v = (d * d for d in data).reduce (t, s) -> t + s
    v = Math.sqrt(v / data.length)
    console.log v

Javascript:

mic = new Microphone({
    unit: .5,
    overlap: .5
}, function (data) {
    v = data.map(function (d) { return d * d; });
    v = v.reduce(function (t, s) { return t + s; });
    v = Math.sqrt(v / data.length);
    console.log(v);
})