[vorbis-dev] Metadata streams

[rillian at telus.net]

On Monday, April 9, 2001, at 02:14 , Aaron Plattner wrote:

> I was looking at the Freeamp stuff and I looked at their RDF metadata 
> stream
> spec. (http://www.musicbrainz.org/MM).  I noticed on that page it says,
> "Furthermore, this format will hopefully be used by the Open Source 
> audio codec
> Vorbis to store audio/video metadata with the audio/video tracks."

Something like that. Robert and I worked on it a bit together last year, 
but I haven't written any code to support it in vorbis. We generally 
just agreed that sharing the work of writing a decent format and using 
it in both the database and distributed files would be a good thing. But 
yes, where things left off, this was the best candidate for the "kitchen 
sink" metadata features people have requested. It would be passed in a 
separate logical bitstream interleaved with the audio data.

The needs of the two applications are a bit different, however. For 
example, lyrics (sychronized or not) and the synchronized event tracks 
belong in separate logical bitstreams (and hence xml documents) from the 
static metadata. All of these would be interleaved with the vorbis audio 
data. Static data, and small bits of syncronized data would probably 
just come at the beginning of the stream, but in the later case one 
wants to allow dispersement throughout the stream to support live 
generation and longer texts.

As the page says, there are also some issues with the rdf-ness of the 
spec. RDF itself is somewhat in flux still, too, so I generally feel 
we're not ready to set anything in stone. Would be nice to have some 
experimental code though.

There's also a need for some sort of 'table-of-contents' for multi-track 
ogg streams, if only to functionally label the various pieces. I'd hoped 
to make the static metadata substream serve in this capacity as well, 
which will obviously require some element additions to the MM spec. 
Others felt a binary format would be better for this; mostly because of 
the parsing overhead for xml/rdf.

  -ralph

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