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Re: OGG container

From: Thierry MICHEL <tmichel@w3.org>
Date: Tue, 21 Sep 2010 15:22:12 +0200
Message-ID: <4C98B184.7030809@w3.org>
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
CC: "public-media-annotation@w3.org" <public-media-annotation@w3.org>

I think you are misunderstanding/missing what we have decided during our 
last F2F in Sophia.

Your contribution is still included in the latest draft of the Ontology 

Your OGG table is included in the following section
5.2.2 Multimedia metadata formats mapping tables

but we have created a new section for
5.2.3 Multimedia container formats mapping tables

where we have added these containers: 3gp, flv, mov, mp4, ogg, webm

Feel free to update the OGG container table, if you have expertize on 
this container,
the file is at:


Le 21/09/2010 14:55, Silvia Pfeiffer a écrit :
> I think you misunderstand some of the way in which Ogg works. Skeleton is
> actually part of the container format and thus all the metadata that
> skeleton supports has to be attributed to Ogg.  See:
> http://github.com/cpearce/OggIndex/blob/master/Skeleton-4.0-Index-Specification.txt
> May I ask what happened to the Ogg mapping table that I previously
> contributed and why that is not being used? I have contributed a mapping
> table for Ogg files, which I think is now at
> http://dev.w3.org/2008/video/mediaann/mediaont-1.0/mediaont-1.0.html#d0e8203.
> It includes the skeleton metadata, which should be counted as
> container-level metadata.
> Cheers,
> Silvia.
> On Tue, Sep 21, 2010 at 8:28 PM, Thierry MICHEL<tmichel@w3.org>  wrote:
>> I have investigated into the OGG container to fill our OGG mapping table
>> [1]
>> Ogg does not know anything about the content it carries and leaves it to
>> the media mapping of each codec to declare and describe itself. There is no
>> meta information available at the Ogg level about the content tracks
>> encapsulated within an Ogg physical bitstream.
>>
>> http://www.xiph.org/ogg/doc/skeleton.html
>> Ogg does not replicate codec-specific metadata into the mux layer in an
>> attempt to make the mux and codec layer implementations 'fully separable'.
>> Things like specific timebase, keyframing strategy, frame duration, etc, do
>> not appear in the Ogg container. The mux layer is, instead, expected to
>> query a codec through a centralized interface, left to the implementation,
>> for this data when it is needed.
>> Though modern design wisdom usually prefers to predict all possible needs
>> of current and future codecs then embed these dependencies and the required
>> metadata into the container itself, this strategy increases container
>> specification complexity, fragility, and rigidity.
>>
>> http://www.xiph.org/ogg/doc/oggstream.html
>> Therfore I guess there is not much to fill in our OGG mapping table.
>> Thierry
>> [1]
>> http://dev.w3.org/2008/video/mediaann/mediaont-1.0/mediaont-1.0.html#d0e12764
Received on Tuesday, 21 September 2010 13:22:41 UTC

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