I have been sitting on this for too long. I am now working on a document for the Gremlin Digital Video (GDV) format based on reverse engineering efforts by Vladimir “VAG” Gneushev. This format was most notably used in Realms of the Haunting.
Some select samples from Realms of the Haunting are here:
http://www.multimedia.cx/samples/gdv/
You might think I would hear about these things sooner. Here is a project that has been around since last May that I just learned about yesterday:
From what I gather based on the website, it is a container format that allows complete encapsulation of a DVD for internet distribution. It can retain menus, navigation, subtitles, special features, etc. It apparently also transcodes video to a custom format named XEB. It also uses some custom variant of the Dolby AC-3 codec called AC-3 VS (virtual surround). These details are a bit sketchy since there is not much code available. The developer claims to want to work with the Linux community to come up with a suitable playback solution.
My first impulse at seeing this was similar to my reaction towards Matroska: Special Microsoft operatives attempting to distract open source multimedia hackers from focusing on more important matters. Not to be outdone in the more-work-for-the-community department, the Matroska developers have a draft of a similarly capable system.
An impromptu search on BitTorrent networks reveals that people are already pressing ratDVD into service for its stated purpose, e.g., making available for P2P distribution such niche-interest media content as Star Wars Episode III and full seasons of 24. So I imagine the demand for this format will eventually grow.
Exploiting capabilities/limitations of available video hardware is nothing new in terms of multimedia programming. The old IBM VGA hardware had a 320×200 resolution mode that could display 256 unique colors. For years, that drove many graphic-heavy applications (notably games but also certain video applications such as FLIC files originally generated by Autodesk software). Back when I was hacking on the Sega Dreamcast I started to brainstorm about a vector quantizer video codec that could take advantage of the PowerVR 3D graphics hardware present in the console.
This article is maintained in Wiki format at http://wiki.multimedia.cx/index.php?title=Frame_Types.
Ultimately, encoded video data needs to be decoded to 2-dimensional arrays of pixel values and presented to the user (or perhaps transcoded to a different format). All of these frames look complete to the user. But the frames often can not stand by themselves. They usually need information from other frames in order to make their presentation complete.
Let’s talk basic video frame terminology. First, there is the intraframe. This is also known as a keyframe. An intraframe is one that can stand on its own. It requires no other frames. It carries with it all the information needed to be decoded.