Ogg Media (OGM), meaning Ogg Media File, is a container format (for video, audio and subtitle streams). It was developed by Tobias Waldvogel and can do a few things the common AVI format cannot. OGM's features include in particular:
* Chapter support
* Multiple subtitle tracks
* Multiple audio tracks of various formats (MP3, AC3, AAC, Vorbis, LPCM)
* Vorbis audio support (there is no "correct" way for AVI to support Vorbis, making any attempt potentially incompatible and unreliable)
OGM support for Windows (Including Microsoft's Windows Media Player) is available via Tobias's own OggDS, Haali Media Splitter, VLC, or RadLight's Ogg Media filters (the last of which can also decode Theora video). On Unix-based systems OGM support is available in MPlayer, xine and VLC.
Fundamentally, the format is a hack of the Ogg container format, which had only been designed to support encoders endorsed by Xiph.org (website), the creators of Ogg. It is most likely going to be viewed as a temporary solution, to be phased out when other media container formats (for example, Matroska) mature and come to support the same services.
Originally, a major drawback of OGM was that it was not free software / open source, even though it was based on the open-source Ogg framework. The reason was that Tobias was embarrassed about the quick-dirty-hack quality of his code, wanting to improve it before releasing it to the keen eyes of the Xiph.org people. Tobias has officially joined the Xiph.org team since, and has donated all the code of his DirectShow filters — including format manipulation and playback — to their BSD-style free software licensed repository. It is available, though without documentation, in the "oggds" module of the repository. Another implementation is available in Moritz Bunkus' ogmtools package.
OGM files most often carry video encoded in the MPEG-4 ASP format and audio in Vorbis or AC-3 (Dolby Digital).
You can use mpcstar to open files with this suffix. http://www.mpcstar.com/
