ratDVD is a highly compressed file type that maintains all the contents of a Digital Versatile Disc (DVD) movie, while reducing significantly the overall size. A typical DVD (usually above 4 gigabytes) can be compressed to about 1 or 2 Gb.
It has been released only for the Microsoft Windows Operating system, and is apparently no longer being maintained by its creator, with the latest version dating from 2005. The official site (ratdvd.dk) has now been replaced with advertisements placed by a domain name selling company. There is speculation that ratDVD was only a preview version (albeit fully functional) of the now commercially sold fluxDVD. While ratDVD contained the features that allowed the home user to create their own archived DVDs, this function has been removed from fluxDVD, allowing only content owners to make and sell fluxDVD archives.
ratDVD works by compressing a full DVD using a proprietary codec named "XEB" . The resulting ratDVD file can then be played directly in a computer (as long as the needed codec has been installed) by a DirectShow-compatible DVD player, or converted back into standard DVD format.
The converting time (average of 3 hours for a standard movie on a 3 GHz P4 processor) has frequently been deemed as excessive. Also, the movie produced is of a lower quality (see lossy compression), thus to some critics it does not qualify for being a "true" DVD container. It has been commented frequently that other compressors were faster, produced better-quality compressed video, and were smaller.
The author has stated that he will release ratDVD as open source some time in the future, probably under the BSD license, but currently its closed-source nature has originated some discussion about possible license infringements related to the use of GPL'ed code such as libdvdnav. ratDVD has an option to not install both of the GPL modules it is shipped with, however playback of ratDVD files does not work in that case. It is controversial whether this can be interpreted under the GPL clause that states that "linking ABC statically or dynamically with other modules is making a combined work based on ABC. Thus, the terms and conditions of the GNU General Public License cover the whole combination."
Critics have also complained about ratDVD not being a standardized format.
ratDVD is available only for the Microsoft Windows operating system, and dependent on Microsoft DirectShow. Additionally, it is not directly supported in popular Windows DVD players, forcing people to use the ratDVD program or Windows Media Player to play ratDVD files. More recently, many users have reported being unable to reproduce their ratDVD files at all under Windows Vista.