US Patent 7425981 Video pre-processing

A foreground object part is distinguished from a substantially static background part of each videoframe within a video sequence. Each video frame is divided into a number of video blocks each of which comprises one or more pixels. A mask frame is generated in respect of each video frame, each mask frame having a mask block corresponding to each video block in each respective video frame. Each mask block is then set to either an object value, indicating that the corresponding video block in the corresponding video frame includes one or more pixels depicting a foreground object part, or to another value.