A sequence of input groups, each input group containing a number of input pixels, is received. A sequence of output frames is provided, where each output frame contains a number of output pixels to refresh a display screen. The pixels of each output frame include (1) a number of new pixels which are the input pixels of a respective input group, and (2) a number of old pixels which are the input pixels of a previous input group. The previous input group is one that's received previous to the respective input group.