I'm looking for a program that I can use to preview a greenscreen chroma keyed, in real time. The main goal is for someone in front of the greenscreen to be able to see what they would be pointing at after post-production, but not to actually record footage with the program. I would be using one camera for recording footage to be manually chroma keyed later, and one for previewing on a monitor for the actor to view.
There are some programs that I've found that are designed for recording, have a live preview on the side, but show with a low framerate when viewing at any resolution beyond 800x600 (which makes it difficult to view anything that needs to be moderately sharp).
I'm primarily looking for something that crudely chroma keys out the green and being able to preview in at least 720p, but not necessarily for recording footage.