forcedPicturesWhenOff

While no subtitle is selected, draw the forced pictures of the Blu-ray or DVD subtitle track in the audio's language, as a disc player does with subtitles off (#513). The track is not selected by this: Tracks.selectedSubtitle stays null, and the choice follows the audio. Selecting any subtitle, a secondary one included, ends it; turning subtitles off brings it back. Off by default, so subtitles off draws nothing.