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

Steve Lhomme steve.lhomme at free.fr
Mon Nov 15 10:20:23 CET 2004

Moritz Bunkus a écrit :
> Hey,
> after the confusion lately about the 'default track' flag I thought I'd
> post this on the ML.
> The situation: We have a 'default track' flag that says that this track
> is the default track for its kind. The usage of this flag from the POV
> of a player is:
> 1. Has the user selected a specific track for this kind? If yes, then
>    use that track. If not, goto 2.
> 2. Has the user chosen to view such tracks in general? If not, don't
>    display a track of this kind (!).
> 3. Does one of the tracks of this kind have its default flag set? If yes
>    display this track, don't display such a track otherwise.
> Remember that the default value for the 'default track' flag is '1'. So
> if it's not written in the file then it is implicitely set to '1'.
> The problem was that TCMP interpreted the presence of the 'default
> track' flag with a value of '1' as 'always show such a track' which is
> not what this flag was inteded for.
> Therefore we need a new flag, let's call it 'force display' for the
> time being. It's default value should be '0' obviously. One problem I
> see with it, however, is that it totally smashes 'default track' if it
> is set. Meaning that 'default track' simply has no meaning whatsoever if
> 'force display' is set to '1'. So maybe another option would be adding
> another value to 'default track':
> '0': nope, it isn't the default track,
> '1': yes, it is the default track, but only display it if the user wants
> tracks of this kind,
> '2': yes, definitely display it.
> Please also note that I personally don't like players forcing me to view
> stuff I haven't selected. I'm always in favour of a player giving the
> user the choice whether he wants to see something or not. This will
> weaken such a flag/option.
> Opinions?

Sorry for the lag. I'm just recovering from vacation time. :)

Well. The force feature should be like in DVDs for subtitles. You have 
no option to disable some kind of subs. But for subs it makes sense to 
have it in different languages (ie unlike what is done on DVD). So IMO 
many tracks could have the forced flag, depending on what language the 
user prefers (falling back to the "default track" if none is found).

So my preference goes to a separate flag.

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