[Theora] OGG/OGM media container

Nilesh Bansal bansal
Tue Jul 6 03:51:17 PDT 2004

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

>> Is there a difference between ogg and ogm? I guess its only the extension
>> that is different and everything else is same.
> My understanding is, that the file format is exactly the same, the main
> difference is the first header in each stream... ogm uses several
> standardised header formats, audio, video and text, in order to make
> identifying unknown codecs easier in directshow (and subsequently other
> frameworks). ie with those three headers you can use any audio or video
> format you choose without have to write custom header parsing routines for
> each codec in the demuxer.

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.

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).

> OGM headers aren't "officially supported" by xiph. The best way to think of
> ogm is as a codec wrapper, to shield the demuxer from the imlpementation
> details of the codec headers. Kind of what an api does... it distills the

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

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.

> 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
Can you please explain.

Nilesh Bansal.

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