ogg dev - Jul 2013 - Metadata

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.

For example, what if I want to make a Theora movie and include information about
the color space or embed an ICC profile?  Or can I include general textual
information, like copyright?  What about timecode?


Brendan

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.
> 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

HTH,
 -r

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:
http://wiki.xiph.org/VorbisComment

>> 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.

HTH,
Silvia.