Choosing The Right File Format/Video
Typical video file formats are MPEG (.mpg or .mp4), QuickTime (.mov), RealVideo (.rv or .rm), Windows Media (.wmv) and Theora (usually .ogg).
MPEG file formats contain either MPEG 1, MPEG 2, or MPEG 4. MPEG is a ISO group. MP3 files are not MPEG 3; they are MPEG 1 Audio Layer 3. MPEG video has algorithm patents.
QuickTime is a file format created by Apple. Although it sounds like another codec, often it contains a licensed version of MPEG 4.
RealVideo is a partially proprietary format by RealNetworks. It is a codec and is often good quality. It is patented. However, an 'open' implementation is available from RealNetworks called 'Helix Player'.
Windows Media is a proprietary format by Microsoft. It is common and is often forced on people via the Windows operating system.
Theora is an open, non proprietary file format. It is often contained in an Ogg file. In this container the file is called 'Ogg Theora'. However, other containers are occasionally used, such as Matroska. Theora, Ogg and Matroska are patent free.
Ogg Theora is the recommended format because it is non proprietary, open and patent free.