biquad

Tiny utility for creating biquad filter nodes.

Install via npm:

npm install biquad --save

This is designed to be used in a Web Audio API capable browser with browserify. See the excellent browserify handbook for information on how all of that works.

Example

In its simplest form, if you just need one biquad filter, you can use it like so:

var context = new AudioContext();
var biquad  = require('biquad');
 
// Create the biquadFilterNode
var lowpass = biquad.lowpass(context, { frequency: 20000 });
// And then connect it to your audio routing graph
lowpass.connect(context.destination);

If you find yourself creating more than one filter, you can set the AudioContext when you require biquad:

var context = new AudioContext();
var biquad  = require('biquad')(context);
 
// Now we can create multiple filters referring to our context variable
var lowpass  = biquad.lowpass({ frequency: 20000 });
var highpass = biquad.highpass({ frequency: 20000 });

API

biquad.filterType([context], options)

Each filterType is aliased here for convenience. For a full list see MDN's developer documentation. options is an object where you can set the Q, frequency and gain parameters. If we take the example from the documentation, these are equivalent:

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var biquadFilter = audioCtx.createBiquadFilter();
 
biquadFilter.type = "lowshelf";
biquadFilter.frequency.value = 1000;
biquadFilter.gain.value = 25;

In biquad:

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var biquad = require('biquad')(audioCtx);
 
var biquadFilter = biquad.lowshelf({
    frequency: 1000,
    gain: 25
});

License

MIT © Ben Briggs