I just discovered that the Ogg Media format (OGM) is not a specification supported by Xiph Foundation. That’s right, OGM is not Ogg. OGM is an extension of Ogg which goes outside of the specification by adding support for DirectShow filters.
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…
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.
The Ogg specification supports video (.ogv extension) and use of Ogm is discouraged.