[vorbis] Desirable Properties of a Real Metadata Format

[Ralph Giles]

On Thu, Oct 16, 2003 at 11:54:31PM -0600, Jack Moffitt wrote:

> You cannot use XML for streamable metadata, at least not without
> changing what you mean by XML.  I wish people would please stop bringing
> this up.

I'm not sure it's as bad as all that. It's possible to design the 
packetizer so that missing interior packets still result in valid xml. 
On-the-fly parsing in the expat model gets you the data when you need 
it. There's also some precedent in jabber's notion of xml "fragments".

Dealing with a missing end-of-stream packet is more of a hack. If the 
packetizer is DTD-specific it can try and substitute the expected 
closing tags, but there is no general solution. However in the expat 
model this isn't a practical limitation since we'll need to tear 
down the parser at the chain boundary in any case. XML's 'completeness' 
detection mechanism has still served its purpose, if only in the 
negative sense.

The opening packet(s) remain essential, but that's the case for all our 
codecs.

I certainly hope streamable XML is possible, SVG is really attractive 
for overlays at HD resolutions.

Cheers,
 -r
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