Hi I'm having trouble understanding how to give pix_chroma_key the colour I want to key out. Right now by playing with the value and range number inputs copied from the help patch gives me in effect a luma keyer. How can I key out a green screen?

Here's the patch I have been building on.. I tried to hook up a colour picker from the mtl abstractions but it doesn't seem to do much. Uses pix_video from 2 pci capture cards.