SourceBuffer

The SourceBuffer interface represents a chunk of media to be passed into an HTMLMediaElement and played, via a MediaSource object. This can be made up of one or several media segments.

Properties

SourceBuffer.appendWindowEnd
Controls the timestamp for the end of the append window.
SourceBuffer.appendWindowStart
Controls the timestamp for the start of the append window. This is a timestamp range that can be used to filter what media data is appended to the SourceBuffer. Coded media frames with timestamps within this range will be appended, whereas those outside the range will be filtered out.
SourceBuffer.audioTracks Read only
A list of the audio tracks currently contained inside the SourceBuffer.
SourceBuffer.buffered Read only
Returns the time ranges that are currently buffered in the SourceBuffer.
SourceBuffer.mode
Controls how the order of media segments in the SourceBuffer is handled, in terms of whether they can be appended in any order, or they have to be kept in a strict sequence.
SourceBuffer.textTracks Read only
A list of the text tracks currently contained inside the SourceBuffer.
SourceBuffer.timestampOffset
Controls the offset applied to timestamps inside media segments that are subsequently appended to the SourceBuffer.
SourceBuffer.trackDefaults
Specifies the default values to use if kind, label, and/or language information is not available in the initialization segment of the media to be appended to the SourceBuffer.
SourceBuffer.updating Read only
A boolean indicating whether the SourceBuffer is currently being updated — i.e. whether an SourceBuffer.appendBuffer(), SourceBuffer.appendStream(), or SourceBuffer.remove() operation is currently in progress.
SourceBuffer.videoTracks Read only
A list of the video tracks currently contained inside the SourceBuffer.

Event handlers

SourceBuffer.onabort
Fired whenever SourceBuffer.appendBuffer() or SourceBuffer.appendStream() is ended by a call to SourceBuffer.abort()SourceBuffer.updating changes from true to false.
SourceBuffer.onerror
Fired whenever an error occurs during SourceBuffer.appendBuffer() or SourceBuffer.appendStream()SourceBuffer.updating changes from true to false.
SourceBuffer.onupdate
Fired whenever SourceBuffer.appendBuffer() method or the SourceBuffer.remove() completes. SourceBuffer.updating changes from true to false. This event is fired before onupdateend.
SourceBuffer.onupdateend
Fired whenever SourceBuffer.appendBuffer() method or the SourceBuffer.remove() has ended. This event is fired after onupdate.
SourceBuffer.onupdatestart
Fired whenever the value of SourceBuffer.updating transitions from false to true.

Methods

Inherits methods from its parent interface, EventTarget.

SourceBuffer.abort()
Aborts the current segment and resets the segment parser.
SourceBuffer.appendBuffer()
Appends media segment data from an ArrayBuffer or ArrayBufferView object to the SourceBuffer.
SourceBuffer.appendBufferAsync()
Starts the process of asynchronously appending the specified buffer to the SourceBuffer. Returns a Promise which is fulfilled once the buffer has been appended.
SourceBuffer.appendStream()
Appends media segment data from a ReadableStream object to the SourceBuffer.
SourceBuffer.changeType()
Changes the MIME type that future calls to appendBuffer() will expect the new data to conform to.
SourceBuffer.remove()
Removes media segments within a specific time range from the SourceBuffer.
SourceBuffer.removeAsync()
Starts the process of asynchronously removing media segments in the specified range from the SourceBuffer. Returns a Promise which is fulfilled once all matching segments have been removed.

Examples

The following simple example loads a video chunk by chunk as fast as possible, playing it as soon as it can. This example was written by Nick Desaulniers and can be viewed live here (you can also download the source for further investigation.)

var video = document.querySelector('video');

var assetURL = 'frag_bunny.mp4';
// Need to be specific for Blink regarding codecs
// ./mp4info frag_bunny.mp4 | grep Codec
var mimeCodec = 'video/mp4; codecs="avc1.42E01E, mp4a.40.2"';

if ('MediaSource' in window && MediaSource.isTypeSupported(mimeCodec)) {
  var mediaSource = new MediaSource;
  //console.log(mediaSource.readyState); // closed
  video.src = URL.createObjectURL(mediaSource);
  mediaSource.addEventListener('sourceopen', sourceOpen);
} else {
  console.error('Unsupported MIME type or codec: ', mimeCodec);
}

function sourceOpen (_) {
  //console.log(this.readyState); // open
  var mediaSource = this;
  var sourceBuffer = mediaSource.addSourceBuffer(mimeCodec);
  fetchAB(assetURL, function (buf) {
    sourceBuffer.addEventListener('updateend', function (_) {
      mediaSource.endOfStream();
      video.play();
      //console.log(mediaSource.readyState); // ended
    });
    sourceBuffer.appendBuffer(buf);
  });
}

function fetchAB (url, cb) {
  console.log(url);
  var xhr = new XMLHttpRequest;
  xhr.open('get', url);
  xhr.responseType = 'arraybuffer';
  xhr.onload = function () {
    cb(xhr.response);
  };
  xhr.send();
}

Specifications

Specification Status Comment
Media Source Extensions
The definition of 'SourceBuffer' in that specification.
Recommendation Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support

31

23 — 31 -webkit-

Yes

42

25 — 421 2

113158
mode

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
updating

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
buffered

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
changeType

70

69 — 704

No

63

61 — 635

? ? ?
timestampOffset

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
audioTracks

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
videoTracks

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
textTracks

31

23 — 31 -webkit-

Yes

42

25 — 421 2

113158
appendWindowStart

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
appendWindowEnd

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
trackDefaults ? ? No ? ? ?
onabort5317

42

25 — 421 2

113158
onerror5317

42

25 — 421 2

113158
onupdate5317

42

25 — 421 2

113158
onupdatestart5317

42

25 — 421 2

113158
onupdateend5317

42

25 — 421 2

113158
appendBuffer

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
appendBufferAsync No No626 No No No
appendStream No12 No ? No ?
abort

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
remove

31

23 — 31 -webkit-

12

42

25 — 421 2

113158
removeAsync No No626 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support33 ? Yes No30 No ?
mode33 ? Yes No30 No ?
updating33 ? Yes No30 No ?
buffered33 ? Yes No30 No ?
changeType ?

70

69 — 704

No

63

61 — 635

? ? ?
timestampOffset33 ? Yes No30 No ?
audioTracks33 ? Yes No30 No ?
videoTracks33 ? Yes No30 No ?
textTracks33 ? Yes No30 No ?
appendWindowStart33 ? Yes No30 No ?
appendWindowEnd33 ? Yes No30 No ?
trackDefaults ? ? ? No ? No ?
onabort33 ?17 No30 No ?
onerror33 ?17 No30 No ?
onupdate33 ?17 No30 No ?
onupdatestart33 ?17 No30 No ?
onupdateend33 ?17 No30 No ?
appendBuffer33 ? Yes No30 No ?
appendBufferAsync No Yes No626 No No ?
appendStream ? ? ? No ? No ?
abort33 ? Yes No30 No ?
remove33 ? Yes No30 No ?
removeAsync No Yes No626 No No ?

1. Limited support to a whitelist of sites, for example YouTube, Netflix, and other popular streaming sites. The whitelist was removed when Media Source Extensions was enabled by default in Firefox 42.

2. From version 25 until version 42 (exclusive): this feature is behind the media.mediasource.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

3. Only works on Windows 8+.

4. From version 69 until version 70 (exclusive): this feature is behind the MediaSourceExperimental preference (needs to be set to true). To change preferences in Chrome, visit chrome://flags.

5. From version 61 until version 63 (exclusive): this feature is behind the media.mediasource.experimental.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

6. From version 62: this feature is behind the media.mediasource.experimental.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

See also

Document Tags and Contributors

Last updated by: Sheppy,