Techniques are disclosed for processing a video stream to reduce platform power by employing a stepped and distributed pipeline process, wherein CPU-intensive processing is selectively performed. The techniques are particularly well-suited for hand-based navigational gesture processing. In one example case, for instance, the techniques are implemented in a computer system wherein initial threshold detection (image disturbance) and optionally user presence (hand image) processing components are proximate to or within the system's camera, and the camera is located in or proximate to the system's primary display. In some cases, image processing and communication of pixel information between various processing stages which lies outside a markered region is eliminated. In some embodiments, the markered region is aligned with a mouse pad, desk area, or a user input device (e.g., keyboard). Pixels evaluated by the system can be limited to a subset of markered region. A simplified skintone detection process can be employed.