[Matroska-devel] adding a 'forced display' flag?

Moritz Bunkus moritz at bunkus.org
Wed Nov 17 11:58:46 CET 2004


> Anyway, Matroska's goal has always been to be feature rich. And at least 
> have the same one as on DVDs, just with more flexibility. So this force 
> flag is exactly what could achieve this. You could see the same content 
> as on your DVD, with the same features or with more freedom...

I agree. So the question is how exactly we'll handle these two flags. We
have to add that to the specs with a very clear description. Maybe even
provide some pseudo code like I've done earlier. I'll start with a
description of the "default track" flag:

  The "default track" flag is a hint for the playback application and
  SHOULD always be changeable by the user. If the user wants to see or
  hear a track of a certain kind (audio, video, subtitles) and she
  hasn't chosen a specific track then the player SHOULD use the first
  track of that kind whose "default track" flag is set to "1". If no
  such track is found then the first track of this kind SHOULD be

  Only one track of a kind MAY have its "default track" flag set in a
  segment. If a track entry does not contain the "default track" flag
  element then its default value "1" is to be used.

The last sentence is just a reminder that Matroska knows default values
even though most apps always write that field nowadays.

First try for the "forced display" flag:

  The "forced display" flag tells the playback application that it MUST
  display/play this track or another track of the same kind that also
  has its "forced display" flag set. The "forced display" flag overrides
  the "default track" flag.

  If more than one track of a kind has its "forced display" flag set
  then the playback application MAY chose one of those tracks based on
  the user's preferences (e.g. choice of language).

Thoughts? (Apart from "I don't like this flag at all". I think we all
agree that playback apps should always allow the user to switch off such
forced stuff even though it does negate the "forced" aspect.)


If Darl McBride was in charge, he'd probably make marriage
unconstitutional too, since clearly it de-emphasizes the commercial
nature of normal human interaction, and probably is a major impediment
to the commercial growth of prostitution. - Linus Torvalds

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