[vorbis] xml stream formats

[robert at moon.eorbit.net]

Sorry for not responding sooner -- my team (FreeAmp) got laid off a
couple weeks back and I've been trying to salvage what's left.

     >We also talked about streaming issues a bit. Jack explained that
     >is going to (does?) insert the three pages of the vorbis header when a new 
     >client connects in the middle of a song. This is necessary to set up the 
     >decoder, but we get the comment page more-or-less for free. Something 
     >similar would have to be done with the timecoded xml streams, since 
     >well-formed xml has a header, and there will probably be a small amount of 
     >metadata associated with each stream: language, who translated it, 

     Ouch. Reading this made me remember something else that I hadn't thought of 
     in this context previously - it is NOT possible to stream well-formed XML, 
     in general. By limiting yourself in certain ways, you can get away with 
     just sending the start of the 'file' (as you've suggested here), then 
     streaming - but then you have some subset of XML, rather than XML. 

     Maybe we have to go back and think about this - is XML really what we need? 
     In fact, if we have seperate streams for most stuff, XML really isn't the 
     most suitable solution, since it's intrinsically tree-structured. If we 
     have seperate streams, isn't each one going to be basically just a sequence 
     of (whatever)? A lyrics stream might have a series of lines, each keyed to 
     a time, for example. 

I just checked out RDF (Resource Description Framework) which intends to
describe resources available on the net. I could see us using RDF as the
format inside the metadata stream, instead of using a full blown XML
DTD. I haven't used RDF -- Jack, is looks like you've used it. Do you
have any feedback on using RDF? 

In any case, using a complete RDF chunk to describe the time-coded
information seems like a great amount of overhead. Both XML and RDF seem
like inappropriate tools for use with time-coded information that is
in-line with the stream. However, XML and RDF are the best tools that I
can think of for maintaining the non-time-coded-metadata information.

Maybe the best approach is to use XML or RDF as part of the stream
header(s) and then to use some other format for the time-coded
information.

In any case, to answer Ralph's original question, the current TrackInfo
dtd does not take video into account, but it should be easy to extend
for use with video as well. But, it sounds as if we need to answer a few
other questions before we delve into the details of creating the overall
metadata solution.

--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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