The red border in the illustration represents the
overscan, the area of the active picture outside the action-safe area. It is not shown on most consumer television screens, unless the user modifies the television's settings. It is generally considered safe to have elements that shouldn't be seen by the viewers placed in this area, such as the edge of the
set or cables and other equipment. However, some television production personnel don't place anything in this area they don't want viewers to see because the red area is always transmitted and could potentially be seen by a viewer with the correct equipment. Television stations generally have professional-grade monitors that can be put into "underscan" mode. These monitors often include white lines showing where the title-safe and safe areas are located. In addition,
TV tuner cards and
DVD players for personal computers often show the entire picture. The action-safe area (green + yellow) and overscan area (red) make up the entire transmitted image, or
active picture. In addition to active picture, analog broadcast signals contain
blanking areas that provide timings and control. When applying digital compression such as
MPEG-4, it is only sensible to compress picture that actually exists, and
active picture is what is used — including areas not available in action-safe areas. Other formats such as MPEG-2 have many ties to analogue broadcasting, and employ only a few set sizes; thus always capturing
nominal analogue blanking in addition to the active picture next to it. Since there are such a wide variety of television screens that may display pictures slightly differently, programs produced in 4:3
aspect ratio are transmitted with picture information in the yellow and red areas to ensure the picture takes up the entire screen with no black area around the edges. Widescreen programs in 14:9 or 16:9 aspect ratio, on the other hand, are produced with zero overscan at the top and bottom of the picture, where the
letterbox bars appear on a 4:3 television. ==References==