[ogg-dev] Metadata

Silvia Pfeiffer silvia at silvia-pfeiffer.de
Mon Jul 22 16:43:41 PDT 2013

On Tue, Jul 23, 2013 at 5:36 AM, Ralph Giles <giles at thaumas.net> wrote:
> On 13-07-22 11:19 AM, Brendan Bolles wrote:
>> Hey everyone, according to Wikipedia's 4-year-old information, there is no standard for putting metadata into an Ogg file.  That metadata must be included in the codec.
> That's correct in that there's no container-level metadata. The
> 'mapping' specs for various sets of codecs embedded in Ogg describe how
> metadata is stored.
>> For example, what if I want to make a Theora movie and include information about the color space or embed an ICC profile?
> Theora only supports two fixed colourspaces--defined in the spec--and
> 'unspecified'. There's generic metadata, so you could do something
> custom with a base64-encoded ICC profile and an undefined colourspace
> flag if you want to track this, but we generally discourage that. Theora
> is a distribution format; it's best to convert to one of the fixed
> output colourspaces at encode time if care about calibration.
> See section 4.3 of http://theora.org/doc/Theora.pdf for details.

Other textual metadata that you can include into a Theora file go into
the Vorbiscomment header:

>> Or can I include general textual information, like copyright?  What about timecode?
> You can include standard tag information in theora videos like title,
> author, copyright and license; just put them in the theora metadata
> header. I'm not aware of a convention for timecode (if you mean timecode
> offset of the first frame; theora is a fixed-framerate codec so there's
> no need for per-frame timecode) but you could make something up for your
> application, or use the 'Basetime' of the skeleton spec.
> http://wiki.xiph.org/Ogg_Skeleton_4

Skeleton has so-called "message headers" which are name-value metadata
fields. Content-type, role and name are required per track in
skeleton4, and others are specified here:
http://wiki.xiph.org/SkeletonHeaders . Apart from the three required
ones, I am not sure what software supports the other headers.


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