So I met someone last night from Entertainment Media Ventures and got the scoop on RealD, at least theatrically.
Theatrically, RealD’s technology adds polarization to the movie image. The projector itself doesn’t really speak 3d – it speaks 2D. But the RealD technology knows that even frames are for the right eye, and odd frames are for the left eye, and alternates polarization filter accordingly. Evens frame get a clockwise polarization, odd frames get a counterclockwise polarization (CCW). The RealD technology physically swaps the filter in front of the projector.
From there, it’s easy to isolate the left image for the left eye, and the right image for the right eye: your RealD glasses. CW for one eye, CCW for the other.
This same well informed friend was not entirely sure what technology RealD provides to Cablevision. I’m still working on it. 
