[PD] color keying using pd and Gem for OSX

[tim cleminson]

hi,
	i am having limited success achieving color keying using 2 stream of 
video. Have tried using the [pix_alpha] method and can achieve color 
keying using to picture sources
or using video as the background and an image as the keyed foreground, 
but replacing the foreground image with a movie does not work.
	tried converting the foreground movie using [pix_rgba] but no use, it 
just screws up the color. using  [pix_hsv2rgb] results in some sort of 
keying but not through the pix_alpha method just as a result of 
shifting the color fields around.
	i was wondering if
		a) what i am trying to do is just wrong
		b) some crucial step is missing
		c) GEM implementation on OS X is lacking

cheers, tim