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

From: Nithin Mathew Kurien <[email-masked]>
Date: Mon, 25 Jan 2016 19:39:32 +0530

Hi,

Playback of 3D MVC tracks in MKV files is now possible through LAV
splitter and madVR. I would like to request an information field in
Matroska that specifies the depth offsets for subtitles when playing
such video files. According to the Blu-ray whitepaper
(http://www.blu-raydisc.com/assets/Downloadablefile/BD-ROM-AV-WhitePaper_110712.pdf),
the way it is done in 3D Blu-rays is like this. The MVC track can have
up to 32 Offset Metadata Sequences (OFS, also called 3D offsets in
TSMuxer). An Offset Metadata Sequence has one depth offset (in pixels,
either in front of or behind the plane of the screen) for each video
frame. Each subtitle and menu track has one of these 32 Offset
Metadata Sequences assigned to it in the M2TS file. In this way, when
a 3D Blu-ray is being played, the subtitle or menu track can be
displayed at the proper depth in 3D space (otherwise it would cut
through the objects in the video, disrupting the viewing experience).
Currently, there is no means for specifying the 3D depth of subtitles
when playing 3D MVC MKVs. I would like to request support for the
same.

Thanks and regards,
Nithin

---

From: Steve Lhomme <[email-masked]>
Date: Tue, 26 Jan 2016 13:34:40 +0100

> splitter and madVR. I would like to request an information field in

Sounds great !

> when playing 3D MVC MKVs. I would like to request support for the

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.

> Thanks and regards,
> Nithin
>
> _______________________________________________
> Cellar mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/cellar

-- 
Steve Lhomme
Matroska association Chairman

---

From: Nithin Mathew Kurien <[email-masked]>
Date: Tue, 26 Jan 2016 19:09:21 +0530

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

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-masked]> wrote:

> 2016-01-26 13:34 GMT+01:00 Steve Lhomme via Matroska-devel
> <[email-masked]>:
> 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.
>

---

From: madshi <[email-masked]>
Date: Tue, 26 Jan 2016 14:16:39 +0100

Best regards, Mathias.