Can anyone tell me how to detect egde or any small operation on a real time video processing from a webcam

Actually I want to to do a small project on a real time video ,in which I am capturing a video from a webcam, preview and then a small kind of operation like background subtraction or edge detection without saving the preview or if save as .avi but continuously capturing and simultaneously do the operation on video frames and showing input and output video.CAn it be possible if yes,how? If not then what is the alternative?