Power consumption of the display subsytem has
been a relatively less explored area compared to other components
of a mobile device including computing, storage, and
networking units, although the former often constitutes one
of the most power-hungry portions of the system. Typical
applications on a mobile device such as web browsing and text
editing tend to have rather static image content; each frame
hardly changes from the previous one. Efficiently detecting
and handling no-motion scenarios is thus critical to extend the
battery life. This paper focuses on image change detection.
We propose to use checksum to detect image changes. Specifically, CRC hardware is used to optimize the power consumption
of 1) refresh of a local display and 2) data compression for
wireless remote display. Compared with a traditional, pixel-by-pixel
comparison approach, using checksum for image change
detection is not only fast, but also reduces accesses to the frame
buffer, resulting in significant power savings. We have built a
FPGA prototype to verify that CRC can capture image changes
well enough to ensure a "visually lossless" quality.