Overscan

As an overscan area on the outer edges of a video picture is referred to, the visibility can not be guaranteed. Projections especially in CRT displays the image edges are covered by a mask or hood to inaccuracies and to be able to hide (for analog tubes practically unavoidable ) deviations in the geometry at the edge and guarantee a clean, straight image completion.

In the production of films, videos, DVDs and TV shows this overscan area of about 6 % has to be considered, which must not contain any relevant image elements (such as insertions or menus ).

For screens with active pixels (eg LCD or plasma), the image can be shown theoretically with pixel accuracy, so that actually no overscan area is necessary. But such display devices use an overscan. For example, some larger flat panel displays the delivered image by about 6 %, and then trim the edge by 6%. This means a loss of resolution, however, is hardly noticeable in film or video footage. For filigree elements such as text or fine lines but more or less strong scaling artifacts can occur.

The overscan area is in contrast to the blanking interval is not normally used for external signals. However, there are analog video production systems that display a digital time- code at the top that can slide as a " string of pearls " of white dots in the visible picture area when the overscan the screen is too short.

Generated as a computer or a TV compatible video signals, was also a precaution released on all four sides of the image that has not been described with information. On some computers, but it was quite possible the graphics hardware - partly through tricks - to program so that it also represented there desired content. On the Commodore C64, it was raised to an art to use overscan sprites in games. On the Commodore Amiga, the use of the overscan area in later OS versions was even officially supported by this. Likewise, Amstrad CPC. By use of the overscan areas can this achieve higher resolutions.

After the graphic output of computers is now displayed more and more of LCD monitors that do not require safety margin, the techniques around the overscan be virtually meaningless. In the field of digital flat panels for the TV area of the overscan has technically only a historical significance. Paradoxically, many manufacturers use it but still even with purely digital resources.