Action safe
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Action safe or safe action, in television broadcasting, is a rectangular area in which the viewer can expect to see action. This represents a requirement unique to television, where an image with reasonable quality is expected to exist where (some) customers won't see it. This is the same concept as used in widescreen cropping.
This is as opposed to active picture or active lines, which is actually the way to refer to all of the available image — but not the available signal, since many broadcast standards contain "black" areas that provide timings and control. When applying digital compression such as MPEG-2, 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. (However MPEG-2 is a bad example, since it has many ties to analogue broadcasting, and employs only a few set sizes; this is why it will always capture nominal analogue blanking in addition to the active picture next to it).
Action safe area is applied against a worst case of on-screen location and display type. The size of the area is typically specified in pixels or percent. For more details, please see Overscan in Television. Suggested amounts are given in the technical specifications (of which there are none, at least officially).
