I have been poking at RealVideo 4 lately. Who knows? We might be able to make a Google Summer of Code project out of it. If the FFmpeg project is accepted for the 2007 season.
Here’s a curious artifact I found: A method called Decoder::getBackdoorOptions(). The function turns out to be a NOP, though. In the original source, I imagine the guts were protected by an “#ifdef DEBUG…#endif” pair.
If you can play with encoder then you can try creating different images with 8×8 filled blocks and thus recovering DC codes (maybe) and DC difference codes, then create blocks with one AC coefficient. When you’ll have enough codes, Michael will look and say what the standard was used ;)
sounds easy.