1. A system for processing a raw video stream, comprising: a threshold detection stage comprising integrated circuitry configured to identify presence of activity in a given image frame, and to stop processing of that image frame by a subsequent processing stage if insufficient activity is identified; a target presence stage subsequent to the threshold detection stage and comprising integrated circuitry, the target presence stage configured to identify presence of a user in an image frame in which activity has been identified, by determining if that image frame includes skintone colored pixels, and in response to that image frame not including skintone colored pixels, the target presence stage is further configured to stop further processing of that image frame by a subsequent processing stage; and a segmentation stage implemented in a graphics processing unit subsequent to the target presence stage and configured to separate pixels of interest from pixels that are not of interest in an image frame in which presence of a user has been identified.