Re: [Cellar] Depth offsets for subtitles in case of 3D MVC tracks in MKV files

2016-01-26 14:39 GMT+01:00 Nithin Mathew Kurien <[email protected]>:
> Hi,
>
> It's like this. Suppose the MVC video track has 8 frames. Also suppose it
> has 5 Offset Metadata Sequences embedded in it at the time of encoding.
> (Sequence entries are in pixels, positive if in front of the screen, and
> negative if behind.)
>
> Frame  1  2  3  4  5  6  7  8
> Seq1    5  1 -8 -2 -9  1 -3 -1
> Seq2    8  1  0  8 -4 -5  4 -1
> Seq3   -2  8 -3 -5  7  5 -5 -4
> Seq4    9  0  0 -5 -2  1 -4 -1
> Seq5   -9  3 -2 -4 -6  0 -3  6
>
> If the M2TS container has 2 subtitle tracks P1, P2 and 1 menu track I1, then
> a mapping can be defined in the M2TS container like this:
> P1 : Seq1
> P2 : Seq3
> I1  : Seq4

OK, so it seems it's both in the header and in the track (the GOP is
part of the stream, I think).

> So basically, the sequences are defined in the MVC track and the mapping is
> defined in the M2TS container. If this mapping is not defined in the
> container, the player would display the subtitle or menu track at the plane
> of the screen. Thus the outcome would be as if a sequence whose all entries
> are 0, is assigned to the subtitle or menu track. This has been a problem
> with the few hardware media players supporting MVC inside MKV, for example
> the Mede8er ones (http://www.mede8erforum.com/index.php?topic=9624.0).
>
> Ideally, a menu track should be displayed in front of the subtitle track,
> which should be in front of the video track. This can be done through the
> proper definitions of sequences and mappings. The free program
> MVCPlanes2OFS.exe from the package BD3D2MK3D
> (http://forum.doom9.org/showthread.php?t=170828) can display all Offset
> Metadata Sequences embedded in a .MVC file.
>
> Thanks and regards,
> Nithin
>
>
> On Tue, Jan 26, 2016 at 6:46 PM, madshi <[email protected]> wrote:
>>
>> 2016-01-26 13:34 GMT+01:00 Steve Lhomme via Matroska-devel
>> <[email protected]>:
>> > I'm not sure I understand. Is the offset per track or per frame for
>> > the subtitle ? If it's per track it should go in the Track Info. If
>> > not that means a mechanism to add that information for each frame.
>> > Maybe BlockGroup could help.
>>
>> The 3D Blu-Ray spec says:
>>
>> > P.9.3.3.6 Offset metadata
>> > The offset_metadata() shall be stored in the user data container
>> > (defined in 9.16.3.1) which is contained in MVC scalable nesting
>> > SEI message of the first view component of each GOP of MPEG-4
>> > MVC Dependent view video stream in decoding order.
>>
>> I'm not a big expert on these things, but doesn't that mean it's part
>> of the MVC video bitstream? In that case there's probably no need to
>> store it in separate MKV fields/properties?
>>
>> Best regards, Mathias.
>
>



-- 
Steve Lhomme
Matroska association Chairman
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