Games like Snatcher and Lunar have no "real" FMV, this is no digitized video like in Double Switch, Night Trap or similar titles. It's more a real time animation similar to the GIF format. The video data for this kind of FMV is very small (the Lunar ISO is only ~30 MB and the files on the disk are only ~10MB). The biggest part is the audio, either compressed (Lunar 2, Popful Mail) or CDDA (Lunar 1) or both (Snatcher, Vay).