[ogg-dev] The use for an XML based metadata format

Ian Malone ibmalone at gmail.com
Mon Sep 10 05:19:05 PDT 2007

On 09/09/2007, Silvia Pfeiffer <silviapfeiffer1 at gmail.com> wrote:
> Daniel,

> A similar argument goes for the encoding quality description and digital rights.
> In contrast, the improved description of the content as in: artist,
> band name, title, organisation involved, and people involved are
> things that improve upon vorbiscomment and should probably be included
> there directly.

There are arguments against simply using vorbiscomment for this,
beyond simply the fact that the Vorbis spec says it should only be
used for short 'jotted on the CD' type notes.  First it is based on
value pairs, this makes it hard to describe relationships in detail;
you must either choose a field name that will not be widely
understood ('drummer', 'sound engineer', even 'composer' won't
get you far) or use a funny way of refining it in the value (such
as artist=(composer) Beethoven), I think cast lists for films present
a similar problem.  There is consistency and indexability to be
addressed (Ludvig van Beethoven; Beethoven, Ludvig van;
Beethoven).  Finally complex relationships are even harder to
handle such as specifying a resource's relationship to the rest
of a collection.

> All I ask for is *not* to reinvent the wheel when there are already
> working, semi-complete metadata formats for Ogg that have been
> carefully prepared to fit with the existing Ogg framework. It would be
> a sheer nightmare to create another new one that does not fit with any
> of the existing ones and is not supported by any media application.

Yes, any attempt to add a metadata format should leverage
what exists already.  I see it like this: Skeleton describes the
technical aspects of the stream, CMML splits it into temporal
parts, but describing the contents is left to Vorbiscomments,
which were by design only sufficient for simple descriptions
(and are tied to a logical stream).  Looking back through
the list archives it was always intended there should be a
metadata format to go beyond what Vorbis comments
could do.

I suppose I should draw attention to some of the stuff I did
before I discovered I didn't have enough time to get some
kind of working application together:
I got a bit sidetracked by the multiplexed streams
compatibility stuff at the time, that and trying to learn XPCOM
to produce a FF plugin (something which was going to take
far more time than I had).  A Rhythmbox plugin is probably the
easiest target, though something Windows based would get
a wider audience, Songbird might be good as it's built on
top of a platform which is designed to handle XML.

P.S. does anyone know what XMP actually does?  Whenever
I look at it all I can find are descriptions of how the embedding
is done.


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