[Theora] OGG/OGM media container

Ralph Giles giles
Tue Jul 6 05:02:02 PDT 2004

<00ff01c46343$827aa190$0100000a at tiger>
<Pine.LNX.4.60.0407060338450.18715 at albani.cs.ubc.ca>
Message-ID: <20040706120202.GC1234 at ghostscript.com>

On Tue, Jul 06, 2004 at 03:51:17AM -0700, Nilesh Bansal wrote:

> So this means ogg/ogm are actually same but ogm uses some standard headers
> while ogg does not put any such restrictions. That is ogm is a ogg, but
> not vice-versa.

Correct. I would also say that the ogmtools provides the standard du
jeur for encapsulating various common-in-avi codecs in an Ogg bitstream,
like 'divx', 'mp3' and so on.

As far as I know, the ogmtools source is the best documentation
available for those encapsulations

> And saying
>   ogg       -    extension for for audio only files
>   ogm       -    extension for audio + video files
> is _wrong_, as the 2 extensions are not just conventions but also differ
> technically (though they are more-or-less similar).

Yes, this is very wrong. I suppose the ogm extension just implies the
presence of the AVI stream headers in the logical bitstreams.

> So xiph "officialy support" ogg and not ogm. But i am not able to find any
> tool to create ogg files. www.xiph.org provide no information about
> either.

Ogg is documented at http://xiph.org/ogg/doc/ (which looks like it needs
some webmaster help)

The main documents are in http://svn.xiph.org/trunk/ogg/doc
and the Ogg format (aside from some of the multiplexing details) are
also documented in RFC 3533.

> Also, what is status of OGM? Is that stable and usable? If yes why
> mencoder etc, dont provide a option to produce a OGM instead of AVI.

I understand it's in wide use by the anime fansub community. We
officially and actively don't recommend it, both because it doesn't
match our technical philosophy for Ogg, and because our whole raison
d'etre is to provide free alternatives to mp3 and divx. So please don't
encourage people to add support. :)

> >Matroska is a different project group... i think they represent two
> >different philosophies... matroska is more a kitchen sink format, whereas
> >ogg is an absolute bare bones format. Which you think is better really

I think that's a nice way of saying that the the matroska folks didn't
like (or didn't understand) what we were trying to do with the ogg
design. I believe their idea was to make a hierarchically searchable
file format with the idea that that would work better than ogg for
editing. Ogg is designed as a streaming format only, although one could
easily build an editing system on top of it.


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