VideoTrack - Web APIs 编辑

The VideoTrack interface represents a single video track from a <video> element. The most common use for accessing a VideoTrack object is to toggle its selected property in order to make it the active video track for its <video> element.

Properties

selected

A Boolean value which controls whether or not the video track is active. Only a single video track can be active at any given time, so setting this property to true for one track while another track is active will make that other track inactive.

id Read only

A DOMString which uniquely identifies the track within the media. This ID can be used to locate a specific track within a video track list by calling VideoTrackList.getTrackById(). The ID can also be used as the fragment part of the URL if the media supports seeking by media fragment per the Media Fragments URI specification.

kind Read only

A DOMString specifying the category into which the track falls. For example, the main video track would have a kind of "main".

label Read only

A DOMString providing a human-readable label for the track. For example, a track whose kind is "sign" might have a label of "A sign-language interpretation". This string is empty if no label is provided.

language Read only

A DOMString specifying the video track's primary language, or an empty string if unknown. The language is specified as a BCP 47 (RFC 5646) language code, such as "en-US" or "pt-BR".

sourceBuffer Read only

The SourceBuffer that created the track. Returns null if the track was not created by a SourceBuffer or the SourceBuffer has been removed from the MediaSource.sourceBuffers attribute of its parent media source.

Usage notes

To get a VideoTrack for a given media element, use the element's videoTracks property, which returns a VideoTrackList object from which you can get the individual tracks contained in the media:

var el = document.querySelector("video");
var tracks = el.videoTracks;

You can then access the media's individual tracks using either array syntax or functions such as forEach().

This first example gets the first video track on the media:

var firstTrack = tracks[0];

The next example scans through all of the media's video tracks, activating the first video track that is in the user's preferred language (taken from a variable userLanguage).

for (var i = 0; i < tracks.length; i++) {
  if (tracks[i].language === userLanguage) {
    tracks[i].selected = true;
    break;
  }
});

The language is in standard (RFC 5646) format. For US English, this would be "en-US", for example.

Specifications

Browser compatibility

BCD tables only load in the browser