Going back through some old posts, I decided to follow up on a codec named Caiman’s Video Codec For Gameboy Advance (new MultimediaWiki page). The official site has a number of movie trailers and anime clips encoded with some custom video and audio codecs. The interesting thing is that the samples are encoded as .gba files which are apparently ROM images that are able to be played in an emulator such as VisualBoyAdvance. Therefore, there are no clean multimedia container files (e.g., AVI) for study.
Unsurprisingly, very few technical details are available. The technology page brags about how tweakable the parameters are, but mentions nothing about coding algorithms. Still, it’s interesting that these A/V codecs were designed and optimized for the Gameboy Advance.