[ogg logo] the xiphophorus company


[an error occurred while processing this directive] OGM is not Ogg. Xiph.org does not support OGM.

What is this OGM stuff, anyway?

Once upon a time, a young named named Tobias created DirectShow filters for the Ogg Multimedia Format. They're great; You can use them to encode video into the Ogg format, as well as play Ogg Vorbis files on programs like Windows Media Player. This is a useful invention, because a lot of people want to use Ogg Vorbis for audio when they archive their DVD's or any other motion-picture oriented multimedia.

So, what's the problem?

The problem is that the DirectShow filters are an extension to the Ogg Multimedia Framework that lies outside of the Ogg specification. So, while it is certainly useful, it's not really 'Ogg.' Ogg is a trademark of the Xiph.Org Foundation, and it's used to delineate between 'within the specification' and 'outside of the specification.'

Why are you so crazy about the specification?

It is important to maintain control of the specification in these matters. The Xiph.org Foundation's mission is to produce open and free alternatives to closed-source and/or proprietary multimedia. In order to make sure everyone is on the same page in regards to patents, copyrights and other legal constructs, the specification needs to remain open and free. If it's from Xiph, it's open and free. It's important not to blur this line.

Aren't you going a little overboard with this? OGM is useful.

If it weren't useful, I wouldn't be talking about this! The problem is that people could be convinced that OGM is Ogg, when it isn't. This has already shown itself, and it's a bit distressing.

I think it's great that Tobias has used Ogg to make something useful. It's not an issue of performance or design, it's a problem of nomenclature.

So, it's just the name, right?

I wish it were that simple. The biggest problem is that people are using OGM primarily to encode DVD's with DivX video and Vorbis audio. I fear that people might be using OGM, and convince themselves that they're using completely free software, when they're not. After all, 'Ogg' is from Xiph, and Xiph only produces free stuff. DivX and XviD are MPEG-4 variants, and subject to any holds that the MPEG patents have on those technologies.

Again; Nothing wrong with DivX or XviD, they're just not completely open standards. Patents apply. It doesn't mean they're not useful, it just means that you might be getting more than you bargained for on the legal side of things.

So, contact the author of OGM, and ask him to stop calling it Ogg.

We've tried. He's not available.

Okay, then release something that people can use that will be open.

You can use Theora.

Aren't you just whining?

I don't think so. We get a lot of E-mail from people, demanding support for OGM. Of course they come to us, it's called 'Ogg.' We're the 'Ogg People.' We don't support OGM. We didn't write it, and we don't have the resources to help people with it. We barely have the resources to deal with all the E-mail just requesting more information about it. The proliferation of OGM equates to a measurable drain on our resources.

Tell me more about technical differences between Ogg ans OGM

Ogg Vs Ogm file format are 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.

In other words ogmtools provides the standard du jeur for encapsulating various common-in-avi codecs in an Ogg bitstream, like 'divx', 'mp3' and so on.

Okay, and what is status of OGM?

The original oggds codebase by Tobias is pretty stagnant, but i think some folk at doom9 have started maintaining it.

7th July, 2004. [an error occurred while processing this directive]