A while ago I made a AviSynth script "AutoRoto" that rotoscopes any object by its outline. simply using a 4,8, or 16 garbage matte.
automatically.
you can read whatever details I made about it on the Doom9 Forums
herethough sadly I'm still trying to make this script faster (rotoscopes a 10 sec clip in 3 minues).
it works... but its slow and crashes from time to time
this function uses VCMohan's Colorit's plugin. specifically the colordrops function.
and while the colordrops can allow multiple fills, the way my code is implemented you can only have one transparent area...
...
I still need to work on it some more but already it makes my rotoscoping that much faster. and I should be releasing it...
... soon....
I hope....