ClearVideo was the most widespread codec in the old days. One cannot name any other codec that was present in AVI, MOV and RealMedia simultaneously. Oh, and it presumably uses fractals.
Recently I’ve discovered one rather funny thing: ClearVideo intraframes are very simply coded. You have standard 16×16 macroblocks, some DCT, one static codeset for DC, one static codeset for AC. It’s simpler than baseline JPEG (well, maybe except for the fact there’s a set of flags signalling if ACs are present in the block at all).
My main problem with it was that I could not find out where are those codes are stored or generated. Well, it turns out that it’s stored in binary form in wrapper DLLs in resources section (so if you use some resource explorer on it you can find the codes in resource TABLE/DCT or modify RAW/*BRAND to remove that annoying watermark but who cares?).
Maybe one day I’ll deal with interframes and RealMedia demuxer support…