Chooses the text track that best matches the preferred language(s), or null
when none relate (or there is no preference / no tracks).
Language dominates: a track is ranked first by which preference it relates to
(earlier entries win) and how closely (see languageRelatedness).
Within a single language, a full track is preferred over a forced-only track
(a user asking for a caption language wants the full captions, not just the
forced foreign-dialogue cues), and a manifest-default track breaks any
remaining tie.
Chooses the text track that best matches the preferred language(s), or null when none relate (or there is no preference / no tracks).
Language dominates: a track is ranked first by which preference it relates to (earlier entries win) and how closely (see languageRelatedness). Within a single language, a full track is preferred over a forced-only track (a user asking for a caption language wants the full captions, not just the forced foreign-dialogue cues), and a manifest-default track breaks any remaining tie.