[...] A high-level JavaScript API for processing
and synthesizing audio in web applications. The primary paradigm is of
an audio routing graph, where a number of AudioNode objects are
connected together to define the overall audio rendering.
var ac = new AudioContext();
ac.decodeAudioData(ogg_arraybuffer, function(audiobuffer) {
var source = ac.createBufferSource();
source.buffer = audiobuffer;
var d = ac.createDelay()
var osc = ac.createOscillator();
osc.type = "square";
osc.frequency.value = 100; // Hzvar g = ac.createGain();
source.connect(d);
source.connect(ac.destination);
d.connect(ac.destination);
g.connect(d);
d.connect(g);
osc.connect(g);
}, function error() { alert("This is broken"); });
Use cases
Games
Audio visualization
Web Application audio feedback
Musical applications
DEMOS
Fancy streaming music player (until we have MediaSource Extension widely
available Firefox
bug, spec)
(Ideally) Anything on the web that makes non-trivial noises
(including offline rendering)
Feature Overview
Asynchronous compressed audio decoding to
ArrayBuffers (formats: same as <audio>)
Precise timing for sample playback
Arbitrary audio routing/mixing
Effect transition, scheduling (automation)
Ability to analyse audio (e.g. FFT)
Low-latency playback
Nodes
Input nodes: produce audio -- audio sources
Output nodes: receive audio -- audio sinks
Processing nodes: process incoming audio, output processed signal
Source Nodes
AudioBufferSourceNode, sample player, plays
AudioBuffer. One shot, but cheap to create
OscillatorNode, sine, square, saw, triangle, custom
from FFT. One shot (use a GainNode)
ScriptProcessorNode (with no input) to generate
arbitrary waveforms using JavaScript (but
beware, it's deprecated !)
MediaElementAudioSourceNode to pipe the audio from
<audio> or <video> in an
AudioContext
MediaStreamAudioSourceNode, from
PeerConnection, getUserMedia.
Processing Nodes
GainNode: Change the volume
DelayNode: Delays the input, in time. Needed for
cycles.
ScriptProcessorNode (with both input and output
connected): arbitrary processing (but
beware, it's deprecated)
PannerNode: Position a source and a listener in 3D
and get the sound panned accordingly
Channel{Splitter,Merger}Node: Merge or Split
multi-channel audio from/to mono
ConvolverNode: Perform one-dimensional convolution
between an AudioBuffer and the input (e.g. reverb)
Paul Adenot, DemoJS, Paris, 2014-10-11
