Web Audio API

By  on  

The Web Audio API allows developers to load and decode audio on demand using JavaScript.  The more I evaluate awesome games for Firefox OS TVs, the more I get to learn about these APIs that I normally wouldn't touch.  The following is a very basic introduction to the WebAudio API, often used for JavaScript games or apps allowing modification of audio on the front end.

Let's start with a reduced Web Audio API code sample:

// Create an AudioContext instance for this sound
var audioContext = new (window.AudioContext || window.webkitAudioContext)();
// Create a buffer for the incoming sound content
var source = audioContext.createBufferSource();
// Create the XHR which will grab the audio contents
var request = new XMLHttpRequest();
// Set the audio file src here
request.open('GET', 'sound-effect.mp3', true);
// Setting the responseType to arraybuffer sets up the audio decoding
request.responseType = 'arraybuffer';
request.onload = function() {
  // Decode the audio once the require is complete
  audioContext.decodeAudioData(request.response, function(buffer) {
    source.buffer = buffer;
    // Connect the audio to source (multiple audio buffers can be connected!)
    source.connect(audioContext.destination);
    // Simple setting for the buffer
    source.loop = true;
    // Play the sound!
    source.start(0);
  }, function(e) {
    console.log('Audio error! ', e);
  });
}
// Send the request which kicks off 
request.send();

I've tried to comment within the code to describe the process as best as possible.  Remember that the above is a very reduced example; there's much more you can do with Web Audio.

I won't pretend to be an expert of all the nuances with Web Audio -- I was simply super excited to see all of this working.  Web Audio does way more than simply allow you to play the audio; you can modify the audio with filters, ramping, and a bunch more.  You can learn more about WebAudio from these awesome sources:

Have you done anything awesome with Web Audio?  Please share with the noobs like me!

Recent Features

  • By
    Page Visibility API

    One event that's always been lacking within the document is a signal for when the user is looking at a given tab, or another tab. When does the user switch off our site to look at something else? When do they come back?

  • By
    Send Text Messages with PHP

    Kids these days, I tell ya.  All they care about is the technology.  The video games.  The bottled water.  Oh, and the texting, always the texting.  Back in my day, all we had was...OK, I had all of these things too.  But I still don't get...

Incredible Demos

  • By
    Hot Effect: MooTools Drag Opacity

    As you should already know, the best visual features of a website are usually held within the most subtle of details. One simple trick that usually makes a big different is the use of opacity and fading. Another awesome MooTools functionality is...

  • By
    Create a Simple Slideshow Using MooTools

    One excellent way to add dynamism to any website is to implement a slideshow featuring images or sliding content. Of course there are numerous slideshow plugins available but many of them can be overkill if you want to do simple slideshow without controls or events.

Discussion

  1. Plopz

    Its funny that you commented every line except the most important.

    source.connect(audioContext.destination);
    

    The magic of the audio api is that you can connect, combine and chain together all of these different nodes which operate on I/O to manipulate the data. The Web Audio developer tools in firefox is helpful to visualize these node traversals.

  2. The Web Audio API also includes a built-in synthetiser that you can use to play sounds without using sound file. I worked on a musical game during a hackathon where you can compose music with strangers or friends: http://polytun.es/

    Also, Pizzicato is a great library to create to create and manipulate sounds with the Web Audio API : https://github.com/alemangui/pizzicato

  3. I made a synthesizer and sound visualizer using the full power of Web Audio API, called Comet. You can find it here:

    https://venerons.github.io/Comet

  4. David,

    We have done cool stuff with the web audio API in conjunction with SoundCTL audio API, doing real time audio streaming and routing.

  5. I made an audio mixer using the Web Audio API here: https://jamesfiltness.github.io/web-audio-mixer/ Have a go at mixing David Bowie’s Space Oddity!

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!