This is a small helper module that allows you to render a canvas to visualize audio from an audio or video element, or a getUserMedia stream. It uses the Web Audio API. This can be useful to display audio visually, or to track down when a video or audio element does not behave as you expect.
- Chrome is the only browser that has support for Web Audio & WebRTC
- works in Chrome for getUserMedia(), Audio(), audio and video elements
- broken in Chrome for PeerConnection, see https://code.google.com/p/chromium/issues/detail?id=121673
Usage with WebRTC
This was primarily written to work with the rtc-media library so here's an example of how it works there:
var media = ;var waveform = ;var localvideo = ;var videoElement = localvideo;var canvas = ;
Usage with Audio interface
This example shows how to pipe an audio file into the waveform display. The canvas will be added to the body element unless you provide a different element to attach it to.
var waveform = ;var audio = 'examples/media/Hydrate-Kenny_Beltrey.ogg';var canvas = ;audio;
Usage with a media element
This example shows how to create a waveform display for a video element. It also shows how to attach the waveform to a separate element.
var waveform = ;var body = document0;var div = document;var video = document;videosrc = 'examples/media/sintel_trailer.webm';videocontrols = 'controls';body;body;var canvas = ;video;
Parameters for waveform
- target : media element or Audio instance
- width : the width of the canvas
- height : the height of the canvas
- stream : if you're using WebRTC, you need to hand in the MediaStream directly
- play : if set to true, also route the audio to the output device
- attach : element to which the canvas will be added as a child
Running the examples
You can use beefy to run the examples, e.g.
$ beefy examples/rtc-media.js
Copyright 2014 National ICT Australia Limited (NICTA)
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
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