[Matroska-devel] How to select the appropriate video track(s)?

David Duffy davidnduffy at yahoo.co.uk
Thu Oct 19 18:56:12 CEST 2006

I understand the spec. to indicate the following priorities when selecting which track to play, please correct me where I may be wrong:

Forced + matching language + default
Forced + matching language
Matching language
Forced + default

So now what happens when there are stereo video streams for left and right eyes?  Are there going to be two default tracks, a default left and a default right?  How do you decided which one(s) to play if there is a stronger match for a mono track but you have 3D hardware and selecting two stereo tracks might seem more logical?

I realise that realistically a "normal" file won't have many video tracks but to be compliant with the spec. in the scenario if this ever did occur what should win?  Of all the possible permutations how do you select the correct video track(s)?

Also, the spec states that "overlay may happen between a forced and non-forced track of the same kind"; is it supposed to happen or is it simply allowed?  How do you tell if overlaying the tracks is required for proper playback or if it should not be done?  Furthermore, the "TrackOverlay" section of the spec. seems to indicate that it is not a true overlay but only to fill in the gaps in silent tracks, how should this be interpreted?


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