[vorbis] Desirable Properties of a Real Metadata Format

[Geoff Shang]

On Thu, 16 Oct 2003, Nathan I. Sharfi 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.
> >
> > jack.
>
> Evidently I didn't convey 1) that in my mind this would be in one huge lump
> at the beginning of the stream before the Vorbis/FLAC/Speex/whatever data or
> 2) my nearly boundless naivete (I don't really know how Ogg handles random
> blobs of what is text or base64'd binary things (I can imagine that would
> cause quite a few people to cringe...))
>
> That said,  why won't it work?

Oh it will work if what you want is metadata.  But it won't give you
streamable interleaved metadata, and having it as a big blob at the
beginning firstly ignores/overlooks a lot of the flexibility contained in
the OGG format, and secondly may mean a lot of data having to be streamed
before you get to the content (depending on the amount of metadata).

I'm guessing the reason it won't work is due to the nature of XML.  You'd
have to read all the XML data before you could process any of it, because
the closing tag would be the last piece of data.  The only way I'm thinking
you could get around it is to have lots of small XML chunks, each
containing its own piece of metadata.  But this would seem to me to be
somewhat untidy, just to achieve streamability.

I vaguely recall Ralph having a webpage discussing metadata and listing
pros and cons for various approaches, but I can't find it.

Geoff.

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