Web Audio API

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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!

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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!

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