hi
we are using GEM/pd at DWI performance at siggraph2005 it's a REALLY REALLY simple keyer i worked on a few years ago got tons of help from CK and jamie on it as i recall. it's used in conjunction with the access grid
http://www.digitalworlds.ufl.edu/projects/CommonTime/overview.htm
cheers~
Patrick Pagano, B.S., M.F.A Digital Media Specialist University of Floirda Digital Worlds Institute 352-294-2082