[Matroska-users] "Forced" flag utility

Rodger Combs rodger.combs at gmail.com
Thu Jul 20 07:20:17 CEST 2017

Currently, the "forced" flag's documentation describes a feature that wouldn't be particularly useful as defined, and doesn't match any implementation's behavior I know of (though if any implementation actually does overlay a forced track alongside a normal one, please let me know). I'd like to propose an updated definition of the default and forced flags:

- Default:
For audio or video, set if that track SHOULD be active if no language found matches the user preference; this can be used to specify the original content language. For subtitles, set if that track SHOULD be chosen if there are multiple tracks which match the user's language preferences. (1 bit)

- Forced:
Applies only to subtitles. Set if that track SHOULD be active during playback, even if the user's preferences would normally not enable subtitles with the selected audio stream; this can be used for tracks containing only translations of foreign-language audio or onscreen text. (1 bit)

These definitions better match the intent of the flags on DVD and BD, without implying user-hostile behavior or overlays of multiple tracks, and I think they do a better job of carrying information about the relevant streams. They also match at least some existing implementation behavior.

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