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

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Sun Sep 9 08:59:40 PDT 2007


these are all good ideas and worth progressing. However, it may be
better not to merge too many goals in one format (MPEG-7 did that and
ended up as a big mess). So, I suggest to start by structuring the
types of things you want - then finding out which parts belong where
into existing formats such as vorbis comment, Skeleton and CMML, and
only then start to develop a new format.

For example: the relationships between the logical bitstreams is a
very semantic description - it needs to be broad enough to enable
different types of applications to do different things with it. E.g. a
video editor will need to know that there are 3 audio channels in a
file and how they overlap each other and also the video channel, while
in contrast a speech recognizer might just want to be able to know
about the one audio channel in there that is speech and a music player
would be totally ignorant of the video channel. Just solving this
generically would be a big feat. It would possibly need to find a
place in skeleton.

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.

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.

OTOH, we could. undertake this cleaning exercise also at the end of
your process when you have all the fields together that you're after.
We would then sit down and discuss where they are best suitable, if
you prefer that. This should be made clear though.


 than the artist and or organisation descriptions.

On 9/9/07, Daniel Aleksandersen <aleksandersen+xiphlists at runbox.com> wrote:
> On 2007-09-09, Silvia wrote:
> > Daniel,
> Hi Silvia,
> I realise I should have started with this. I got a little carried on with my
> ideas. Apparently I am no good when it comes to sharing an idea.
> Short answer: The format should describe media content and relation between
> them in an Ogg stream. Intended usage is media management and sorting
> trough search and media manager software.
> Long answer: See below.
> > before you step over everything that has been done before, we need to
> > determine what exactly is the use case for your new specification.
> >
> > What concerns metadata, we currently have:
> >
> > * vorbiscomment - this is a header at the beginning of a logical
> > bitstream which has metadata that refers to the complete file; there
> > is a specification, which has been public for a long time and is the
> > de-facto standard that is (or should be) used by all software (see
> > http://xiph.org/vorbis/doc/v-comment.html)
> >
> > * cmml - this is a logical bitstream for time-continuous textual
> > annotations (metadata) for ogg files (see
> > http://wiki.xiph.org/index.php/CMML)
> >
> > * skeleton - this is an extension to the ogg bitstream format, which
> > has all the encapsulation-specific low-level metadata (see
> > http://wiki.xiph.org/index.php/Ogg_Skeleton)
> >
> > All of these are supported by xiph and may need further
> > work/extensions or potentially a replacement if they are not fit to
> > provide what is required.
> >
> > Before throwing out more random specifications, could we please look
> > at what you are trying to achieve with the new format? Can you tell us
> > where the existing technologies are lacking?
> What I want is a format to give a detailed description of the content in an
> Ogg stream. The usage would be improved searchability on local machines
> (possibly even on the web and file sharing clients too) and sorting in
> media management software such as Apple iPhoto, Amarok, and WinAmp.
> Currently only Vorbis comment describe the content. What I aim to is to
> replace Vorbis comments. Vorbis comments are very limited to a few field
> names for describing content. There is only a poorly developed look-a-like
> standard for describing audio files; and all other media formats are left
> alone. End users may indeed slap on additional field names, but no media
> management software no search engine know to look for them.
> Another thing this format describes is relations between media in an Ogg
> stream. See the audio:collection:artwork element for instance. (Imagine an
> audio:lyrics element too.)
> This random specification was intended to start development for a real
> metadata/content description format. This XML based thing I have put
> together in a few hours might not be the best. But it does provide a better
> way to detail describe
> I have no doubt that others can do this better. But as no one seamed to be
> working on a description format; I took it upon myself to start working on
> *something*.
> Hope this clarifies things.
> --
> Daniel Aleksandersen

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