Overscan. Overscan is the term used to describe the situation when not all of a televised image is present on a viewing screen.
It exists because television sets from the 1930s through the 1990s were highly variable in how the video image was positioned within the borders of the cathode ray tube (CRT) screen. The solution was to have the monitor show less than the full image ie. with the edges "outside" the viewing area of the tube. In this way the image seen never showed black borders caused by either improper centering or non-linearity in the scanning circuits or variations in power supply voltage all of which could cause the image to "shrink" in size and reveal the edge of the picture. With the ending of CRT displays, this issue has largely (but not completely) disappeared. Origins of overscan[edit] Press Red Blog: Red Button and widescreen.
Press Red Blog: Support report: video aspect ratio issue on satellite Sport service.