MediaSource API as a node.js Writable stream

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13632.4.04 years ago9 years agoMinified + gzip package size for mediasource in KB


MediaSource API as a node.js Writable stream

Sauce Test Status
Stream video/audio into a <video> or <audio> tag by attaching node.js Writable streams.
This package is used by WebTorrent (along with other approaches) to support media streaming.


npm install mediasource


var MediaElementWrapper = require('mediasource')

function createElem (tagName) {
  var elem = document.createElement(tagName)
  elem.controls = true
  elem.autoplay = true // for chrome // for firefox
  return elem

var elem = createElem('video')

var readable = // ... get a readable stream from somewhere
var wrapper = new MediaElementWrapper(elem)
// The correct mime type, including codecs, must be provided
var writable = wrapper.createWriteStream('video/webm; codecs="vorbis, vp8"')

elem.addEventListener('error', function () {
  // listen for errors on the video/audio element directly
  var errorCode = elem.error
  var detailedError = wrapper.detailedError
  // wrapper.detailedError will often have a more detailed error message

writable.on('error', function (err) {
  // listening to the stream 'error' event is optional


// media should start playing now!

advanced usage

wrapper.createWriteStream() can be called multiple times if different tracks (e.g. audio and video) need to be passed in separate streams. Each call should be made with the correct mime type.
Instead of a mime type, an existing MediaSourceStream (as returned by wrapper.createWriteStream()) can be passed as the single argument to wrapper.createWriteStream(), which will cause the existing stream to be replaced by the newly returned stream. This is useful when you want to cancel the existing stream and replace it with a new one, e.g. when seeking.

should one use this package?

Naively using this package will not work for many video formats, nor will it support seeking. For an approach that is more likely to work for all video files, and supports seeking, take a look at videostream.
Or for a package that tries multiple approaches, including videostream and this package (mediasource), as well as a Blob API (non-streaming) approach, and works for many non-video file types, consider render-media.



Specify how many seconds of media should be put into the browser's buffer before applying backpressure.


Handle errors by listening to the 'error' event on the <video> or <audio> tag.
Some (but not all) errors will also cause wrapper.detailedError to be set to an error value that has a more informative error message.


MIT. Copyright (c) Feross Aboukhadijeh.