isDefault

Specifies whether the Track is considered the default track.

The exact meaning depends on the track type and source.

Audio tracks

For AudioTrack, this marks the audio track the player considers the default for the source. For tracks discovered from playback, this is the initially selected audio track chosen by the player and the underlying track selector.

Subtitle tracks

For SubtitleTrack, this is true for subtitle tracks configured with isDefault = true and for manifest subtitle tracks that carry default selection metadata, such as the DEFAULT attribute of an HLS EXT-X-MEDIA tag.

This flag is informational only. The player does not automatically enable subtitle tracks where isDefault is true. To select such a track, listen for SourceEvent.SubtitleTracksChanged, find the default subtitle track, and select it explicitly via Source.setSubtitleTrack:

player.on<SourceEvent.SubtitleTracksChanged> { event ->
    event.newSubtitleTracks.firstOrNull { it.isDefault }?.let { defaultTrack ->
        player.source?.setSubtitleTrack(defaultTrack.id)
    }
}

Thumbnail tracks

For ThumbnailTrack, this is false for tracks created by the player.