A non-square pixel used on TV screens. Pixels used in the North American TV standard (NTSC) are slightly wider than they are tall (12:11 aspect ratio). Pixels in the PAL and SECAM systems used throughout the world are slightly taller than they are wide (10:11 ratio).
Computer screens use square pixels. Thus, when the computer is used to create menus and graphics for DVDs, an adjustment has to be made. If video and image editors do not provide automatic compensation, the graphics artist or video editor must compensate manually. For example, a 720x540 frame might be used for graphics creation, but it is scaled down to 720x480 to output to DVD or 720x486 to output to the D1 format. See DVD