Difference Matte Keying software I would like to know if anyone out there knows of any free software, or software not as expensive as Adobe After Effects, that can do Difference Matte Keying? I have searched the web a little and have not come up with any promising results. Note: Chroma Keying is not an option. I am on a Windows 7 computer.

Thank you in advance for your time, and possible help.
Blender, which is free and open-source, can do difference matte keying.

I don't know if it's better or worse than After Effects' keyer because I haven't used it before.