[Matroska-devel] multiple video streams stereo 3D mode broken

Steve Lhomme slhomme at matroska.org
Sun Jun 17 15:26:46 CEST 2012


On Wed, Jun 6, 2012 at 5:51 PM, Ben Humpert <ben at an3k.de> wrote:
> In reply to this post:
> http://lists.matroska.org/pipermail/matroska-devel/2011-February/003986.html
>
> 2011/2/27 Steve Lhomme <slhomme at matroska.org>:
>> Parsers that don't know about TrackOperation will not be able to play
>> these tracks. That's one of the reason for the bump to Matroska v3. A
>> file marked as readable by v3 (and up) compliant readers and can only
>> handle v2 may decide not to play the file. The left and right tracks
>> may be marked as NOT Enabled as well (0xB9) and then the player ens up
>> with just the virtual track that it can't play anyway.
>
> Does that mean that a mk3d using frame sequential with two separate
> video tracks cannot be played back in 2D on mkv v2 systems? If so this
> is a huge downside of matroska since the Bluray specification is able
> to do that.

These tracks are not played if the Enabled flag is set to false. But
there are many chances that such a player doesn't respect that flag
either and so the content would be available to the user anyway. There
is no reason for a player to honor this flag if there's not going to
be something in the player that can set it back (TrackOperation or
chapter codecs).

> Isn't it possible to add a fallback somehow like "if you can't read
> the end result (virtual track/trackoptions) fall back and simply read
> the first video track (specified by the virtual track)".

It's hard to make conditional fields in a file, to be interpreted
differently depending on the version of a player. In the end, as said
above, backward compatibility is not a real issue here.

> If v2 can't read 3D virtual tracks at all v2 should just read the
> first video track in the container instead of the unreadable 3D
> virtual track -> Since Frame Sequential always serves the left eye
> first the video track for the left eye should always be the first
> video track in the container.
> If creators want to play a trailer, fbi warning or whatever in front
> of the main 3D video they only have to make sure that the left eye
> video track is the first video track. Regardless where the trailer
> video tracks are placed in the container, the creators always have to
> use a virtual timeline to get first the trailers and the the main
> video played back, so this should not be a problem.
> For sure v2 has to ignore the "enabled/not enabled" setting for the
> first video track if the fallback is used!
>
> This may not add 3D fallback support to all players but to all
> frequently updated ones (eg. jailbreaked appletv).
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-- 
Steve Lhomme
Matroska association Chairman


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