Since I can’t do anything but look at various codecs, I did exactly that. So here are some details about codecs nobody cares about.
First, I looked at a video codec used in videos (movies and TV series) for certain hand-held console. Despite it coming from Majesco, video data start with VXGB magic, reminding of a certain other codec for a slightly newer hand-held console with its data starting with VXDS. Structurally it’s very close to it as well, being simplified H.264 rip-off. My REing efforts were thwarted by the binary specification organisation: while code is supposed to reside in data segment, it constantly calls functions from fast RAM area with no apparent place where they are initialised. I expect it to be some of that code being duplicated there for performance reasons but I haven’t found the place where that copying is performed. Oh well, nobody cares about the format anyway, why should I be an exception?
Then, there’s a whole family of Pixar codecs. The Toy Story game made by them relied on a bunch of QuickTime codecs made by them. There are decoders provided for pix0–pix7 and pixA codecs while the game itself seems to have content only in pix0, pix3, pix4, pix5, pix7 and pixA formats. The binary specification causes Ghidra decompilation failures (mostly in the functions responsible for the decoding) so I could figure something out and something is left as an exercise to a masochist the reader.
All codecs are paletted and most of them operate on 4×4 tiles. Pixar codecs 0 and 4 are actually raw format (with data re-arranged into 4×4 tiles). Codecs 3 and 5 are similar, they maintain a list of tiles (transmitted in the beginning of the frame; frame can update some tiles in the list) and image data is coded as a series of opcodes meaning “draw tile number N”, “leave next N tiles unchanged” or “restore next N tiles from the background image” (that image is stored in some other file, likely compressed with codec 0 or 4). Codec 7 seems to employ static Huffman coding (and I don’t know much beside that fact). Codec A looks like some kind of RLE but I may be wrong.
P.S. I also started some code re-organisation and improvement. For example, I finally got rid of ByteReader/ByteWriter wrappers over I/O objects so it’s less boilerplate code—but unfortunately I’ll need to convert the existing codebase to the new way. I’ve done that for main NihAV repositories but na_game_tool is not yet updated. And I fear I’ll need to waste some time fixing and extending my MPEG-4 ASP decoder (so it can play all videos from my collection). All this leaves not so much time for researching (very) old codecs.