[vorbis-dev] ogg stream-id options

[Ali Abdin]

* Monty (xiphmont at xiph.org) wrote at 16:08 on 17/11/00:
> 
> > Right now, the only thing we produce are 'degenerate' ogg files. They
> > *only* contain a single vorbis audio stream. We've been telling people the
> > file extension is .ogg, to to magic detection on the initial OggS, and
> > that the mime-type is application/x-ogg.
> 
> A degenerate ogg file is any meta-header-less stream/link containing only
> one logical bitstream.
> 
> 
> > We reevaluated the extension issue (the answer was no) and the mime-type
> > issue (we were swayed) and decided we'd recommend multiple mimetypes when
> > we have the video codec working, and add efficient discrimiation to the
> > requirements for the toc/metadata substream we'd always planned on.
> 
> I'm swayed in that I agree with their functionality arguments
> (meaning, I agree with the end goal).  I'm not convinced mime is the
> sole way to do this.  Mime (to identify ogg) and magic (to identify
> container contents) is still my proposal.  Of course, we'll eventually
> agree to something.

Umm - so you are saying we should have one mime - "application/x-ogg" and have
multiple "magic" to identify the contents ?

Whats wrong with mapping different magics to different mime-types?
 
> > I'd proposed we combine the toc header with the kitchen-sink metadata
> > people have requested, and that we use xml-encoded rdf based on the Dublic
> > Core element set to do it.
> 
> No.  The metaheader is meant to be something *much* simpler.  No XML
> there (and I say this because I don't want a full blown XML parser,
> again, just to figure out what to do with a stream.  XML is alot of
> weight).  It's to be a single page with very basic arrangement
> information.

I kind of agree that XML is not the solution. Also XML is not appropriate for
"magic" - Theoretically you should parse XML not do a substring search on it or
whatever.

By the way, Havoc Pennington (gtk+/Red Hat hacker) recently added (or
invented) a "GMarkup" language for the latest development version of GLib. It
is a very simple leightweight "derivative" of XML (basically, you just have
tags). This is nice if you want XML but no the full "bloat" of it (entities,
namespaces, etc.). This is primarily useful for things like "embedded" devices
(imagine a Ogg Music Player (hardware) that would need to parse the metadata,
it shouldn't have to use libxml (for example) but could use the more
leightweight parser (GMarkup)). GMarkup is part of glib though, so if you
wanted to use it you would have to bust it out or something. I'm not saying
you should use GMarkup!!! its just some info I thought I'd share.
 
> > Note that this doesn't really allow mime magic detection of the 'sequence
> > x at offset n' type. What I meant earlier about substring searching is
> > that you first look for the initial OggS, then search for '<useage>' in
> > bytes 15-200 and case on whatever comes immediately after it.
> 
> > incorporate. The librarians think this is a hard problem too.
> 
> Except I want something simpler than what you propose.  Perhaps
> something more complex than what I'm thinking of now will become
> necessary (actually I expect that to be the case).  This is meant to
> be information for applications to use, not as much humans.

Regards,
Ali

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