Windows of the first type and windows of the second type are identified within a frame using energy associated with each short window within the frame. The short windows of the first type and the short windows of the second type are then grouped into two preliminary groups based on the window type of each short window. Further, if the number of short windows in any of the two preliminary groups exceeds a threshold number, the short windows in this large preliminary group are further grouped into at least two more groups.
