Hmm. maybe thats a plan. You can write scripts to do it, rather than an overlay. I'll see what i can do for you. Basically, if you set a command for "key/R4_FRAME+" preference value, that is executed every frame. You can use the standard 'find next available file' command in the script language, but it may be slow so i'd suggest incrementing x.
Anyway, at some point i'll implement this.
AVI out requires a whole load of stuff with streams - i may have a poke with VFW and see if thats easier, but i'm afraid for now thats not high priority
- Gordon