[theora] theora and xml

[ogg.k.ogg.k at googlemail.com]

> In any case: what I said earlier still holds - the best way to include
> such XML into Ogg is through a Ogg Kate track, but you have to
> serialise the data and write an encoder (or at minimum a transcoder to
> the Kate input format).

If it is timed (eg, different portions of XML correspond to various
temporal segments), then I think a good way would be to include it as
metadata to each of these temporal segments in a Kate stream. Metadata
attached to timed segments, or other objects, is something that is not
in a release of libkate yet, however (the bitstream is still backward
compatible of course).
If this is done in this way, then there are two possibilities:
- include each timed portion of XML as a separate metadata (metadatum
?) in XML format (upon decoding, one can then retrieve this metadatum
along with start/end times, and parse it as XML)
- decompose each timed portion of XML into more basic blocks and
include those as separate metadata for the same temporal segment
(means you get a set of tag/value pairs, rather than XML, on
decoding).

If it's not timed (eg, it applies to the whole track), then it's best
added as Vorbis comment(s) to the Theora track.

In any case, whatever you do, you'll need some software to retrieve
the metadata at decode time, and do with it what it is one does with
timed metadata.