SourceBuffer: mode property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Note: This feature is available in Dedicated Web Workers.

The mode property of the SourceBuffer interface controls whether media segments can be appended to the SourceBuffer in any order, or in a strict sequence.

The two available values are:

  • segments: The media segment timestamps determine the order in which the segments are played. The segments can be appended to the SourceBuffer in any order.
  • sequence: The order in which the segments are appended to the SourceBuffer determines the order in which they are played. Segment timestamps are generated automatically for the segments that observe this order.

The mode value is initially set when the SourceBuffer is created using MediaSource.addSourceBuffer(). If timestamps already exist for the media segments, then the value will be set to segments; if they don't, then the value will be set to sequence.

If you try to set the mode property value to segments when the initial value is sequence, an exception will be thrown. The existing segment order must be maintained in sequence mode. You can, however, change the value from segments to sequence. It just means the play order will be fixed, and new timestamps generated to reflect this.

This property cannot be changed during while the SourceBuffer is processing either an appendBuffer() or remove() call.

Value

A string.

Exceptions

The following exceptions may be thrown when setting a new value for this property:

InvalidAccessError DOMException

Thrown if an attempt was made to set the value to segments when the initial value is sequence.

InvalidStateError DOMException

Thrown if the SourceBuffer object is being updated (i.e. its SourceBuffer.updating property is currently true), the last media segment appended to this SourceBuffer is incomplete, or this SourceBuffer has been removed from the MediaSource.

Examples

This snippet sets the sourceBuffer mode to 'sequence' if it is currently set to 'segments', thus setting the play order to the sequence in which media segments are appended.

js
const curMode = sourceBuffer.mode;
if (curMode === "segments") {
  sourceBuffer.mode = "sequence";
}

Specifications

Specification
Media Source Extensions™
# dom-sourcebuffer-mode

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
mode
Available in workers
Experimental

Legend

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Full support
Full support
Partial support
Partial support
No support
No support
Experimental. Expect behavior to change in the future.

See also