[vorbis] xml stream formats

[robert at moon.eorbit.net]

On 10 Jul, Ralph Giles wrote:
> No, I don't think we should use RDF for the time coded data. The two
> proposals I see as viable are: 
> 
> Generalized xml documents which include timecode tags. This is what I've
> been arguing for.

XML (RDF?) at the beginning of the stream that covers all the time-coded
metadata for the entire stream?
 
> A "chunk" format with external timecode information. The chunks may or may
> not include xml or another kind of markup. (I'd go with plain utf-8 text
> here, myself.)

And these chunks would be interleaved into the actual stream so that
they get transmitted as the stream gets transmitted?

> We don't have a consensus on which of the two is better.

If I understand your summaries correctly, I really like the latter one
for its flexibility, but I really don't like having to come up with a
completely seperate infrastructure for them.

>> If we decide to go with RDF, I think it makes sense to define an RDF
>> 'vocabulary' that acts as the guideline for encoding the common pieces
>> of metadata. Even though RDF allows the user to make up the properies at
>> will, this probably isn't desired. The players will then have to deal
>> with the age old issue of 'what of this information do I really need?'.
>> If there is only one way to encode the name of the artist then the
>> players will know what data chunks to look for, no?
> 
> Absolutely. We need something like the Dublin Core (http://purl.org/DC/)
> for media metadata. I'd suggest that we stay name-compatible with dc where
> we have overlap and just add what's missing.

100% agreement here. My plans for later today are to take a stab at
   converting my TrackInfo.dtd into a RDF definition that uses the
   Dublin Core. 

> How small can expat be? Michael's argument is that Winamp won't take a
> player plugin over 70-100 KB into the main distribution, so if we could
> get one in 20K we might have a chance. My interest (see above) in getting
> in a general parser had as much to do with the abitrary associated xml
> streams proposal above as metadata in particular.

Expat is small, but not that small. I was unaware of the size
limitations that WinAmp puts in place. I would be inclined to ignore
WinAmp's size restriction and create a full fledged plug-in -- WinAmp
will include that plugin when Vorbis gets popular enough. But, you've
got a chicken and egg problem with that approach: You need ubiquitous
support (read: winamp) in order for Vorbis to become popular.

> I've also been assured that by making some reasonable limitations and
> assuming a particular dtd/schema we can write a parser for our RDF
> metadata in one or two thousand lines of C. I don't think there would be a
> significant space issue in that case.

It can be done in far less than 2000 lines of C. However, that approach
opens a gigantic can of worms as far as compatibility is concerned. And
RDF parser has the same requirements as an XML parser, and any parser we
could create in a few hundres/thousand lines of C would be incompatible
with XML.

I really don't like this option because of the troubles and nightmares
it will cause in the future. But, I don't really have a solution to the
WinAmp problem either. :-( 

Oh yeah, I do: use FreeAmp. :-)

> Ah, I didn't realize the imdb made its data available (well, I haven't
> read the license, but at least you can download a snapshot). They still
> don't seem to provide a machinable query interface, and afaik don't track
> individual releases (on vhs, dvd, film, etc.) so I still think there's a
> need for this, even if you got your primary data from them.

I don't think they make the data available -- it would be nice if they
did. It just a large amount of work that needs to get duplicated if you
can't get the data...

--ruaok         Freezerburn! All else is only icing. -- Soul Coughing

Robert Kaye -- robert at moon.eorbit.net  http://moon.eorbit.net/~robert

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