The problem is that subtitles aren't all that intuitive in any case. An example is a typical anime episode. There are TWO subtitle tracks, rather than one. The assumption is that all subtitles are in one track, and those that would be displayed when listening to English audio (also referred to as "forced") will be flagged as such. Nope, not how they do it.
There is a "forced" track, and there is an "everything" track. There are then flags that select which one to play... that do not always work as intended, so playing the video as normal will get you English audio and the "everything" subtitle track, instead of the "forced" track (this is using VLC to play the MKV file as ripped).
Occasionally, you find a movie that actually handles subtitles correctly. Avatar is one. Subtitles are properly flagged (forced for those meant to be shown even when watching in English). But, they don't always come through in a way that VLC expects.
For me, I process everything through handbrake afterwards, moving the "forced" track to be the first subtitle track, THEN process the result through mkvtoolnix to add actual "forced" and "default" flags (missing from the original BD) to the MKV file, so that everything works as intended.
How to disable automatic subtitles
Re: How to disable automatic subtitles
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