This article describes how you can use the THEOplayer API to detect text track quality changes. A text track "change" is triggered by enabling (or disabling) a subtitle or closed captions track.
The TextTrack API provides this functionality.
More specifically, as a developer, you'll subscribe to the change
event in the TextTrack API.
Implementing this functionality is a common use-case for developers who want to build their own UI, and annotate the subtitle (or closed captions) track that is currently active.
Table of Contents
THEOplayer allows you to track text track changes on the following SDKs.
Web SDK | Android SDK | iOS SDK | tvOS SDK | Android TV SDK | Chromecast SDK | Roku SDK |
---|---|---|---|---|---|---|
Yes | Yes | Yes | Yes | Yes | Yes |
The TextTrack API is available across all of our 4 base SDKs. As described in the introduction,
to detect text track changes, you want to detect the change
event in the TextTrack
API.
The implementation of the Web SDK applies to all web-based platforms, including Tizen and webOS.
The Web SDK exposes the TextTrack API through player.textTracks
.
This textTracks
property is a TextTrackList
that inherits from the TrackList
.
This TrackList
dispatches the events from the TrackListEventMap
.
This TrackListEventMap
contains the change
event, as well as the addtrack
and removetrack
event.
The code below allows you to detect text track changes.
player.textTracks.addEventListener("change", function (event) {
const track = event.track
const isEnabled = track.mode == "showing"
console.log(track, track.label, track.kind, track.type, isEnabled)
})
The properties of a text track
(e.g. mode
, kind
) are described at https://docs.theoplayer.com/api-reference/web/theoplayer.texttrack.md.
The implementation of the Android SDK applies to all Android-based platforms, including Android TV and Fire TV.
The Android SDK exposes the TextTrack API through player.getTextTracks()
.
This getTextTracks()
method returns a TextTrackList
that inherits from the TrackList
.
This TrackList
dispatches the events from the TextTrackListEventTypes
.
The TextTrackListEventTypes
contains the TRACKLISTCHANGE
event, as well as the ADDTRACK
and REMOVETRACK
event.
The code below allows you to detect text track changes.
player.getTextTracks().addEventListener(TextTrackListEventTypes.TRACKLISTCHANGE, trackListChangeEvent -> {
TextTrack track = trackListChangeEvent.getTrack();
boolean isEnabled = (track.getMode().getMode().equals("showing"));
System.out.println(track.getLabel() + ", " + track.getKind() + ", " + track.getType().getType() + ", " + isEnabled);
});
The properties of a text track
(e.g. mode
, kind
) are described at https://docs.theoplayer.com/api-reference/android/com/theoplayer/android/api/player/track/texttrack/TextTrack.html and https://docs.theoplayer.com/api-reference/android/com/theoplayer/android/api/player/track/Track.html.
The implementation of the iOS SDK applies to all iOS-based platforms, including iPadOS and tvOS.
The iOS SDK exposes the TrackTrack API through player.textTracks
.
This textTracks
property is a TextTrackList
.
This TextTrackList
dispatches the events from the TextTrackListEventTypes
.
The TextTrackListEventTypes
contains the CHANGE
event, as well as the ADD_TRACK
and REMOVE_TRACK
event.
The code below allows you to detect text track changes.
player?.textTracks.addEventListener(type: TextTrackListEventTypes.CHANGE, listener: { (event) in
let track : TextTrack = event.track as! TextTrack
let isEnabled = (track.mode.rawValue == "showing")
print(track.label, track.kind, track.type, isEnabled)
})
The properties of a text track
(e.g. mode
, kind
) are described at https://docs.theoplayer.com/api-reference/ios/Protocols/TextTrack.html and https://docs.theoplayer.com/api-reference/ios/Protocols/Track.html.
This subsection is in maintenance. Reach out to our team if you need help.
Are you reading this article because you're interested in subtitles and closed captions? Continue reading below.
Refer to "How to track id3 cues" if you're interested in timed metadata (id3, emsg, EventStream, EXT-X-DATERANGE, ...).
Are you reading this article because you're implementing a custom UI? Then you'll find the following articles interesting: