Tektronix Grass Valley 3000 - Manual (Page 121)

3-13
Shaped and Unshaped Video
Shaped and Unshaped Video
Shaping and unshaping are generally involved only in keying and
compositing situations.
Whenever a key is performed, there are always three signals: the
key source, the key fill (fill video), and the background video. The
key signal cuts a hole in the background, into which the fill video
is inserted. Devices such as character generators often output both
the key signal and the fill video.
Shaped Video — Fill video that has been “multiplied” by a key
signal to produce a raster image to be inserted into a key hole cut
in background video by the same key signal. (An example of
shaped video is the fill video output of a character generator,
which consists of characters on a black matte.)
Unshaped Video — Previously-shaped fill or composited video
that has been unshaped by an unshaping processor which
“divides” the video by the key signal. The Model 2200, 3000, and
4000 switchers, as well as some Digital Picture Manipulators
(DPMs), have selectable unshaping circuits on their outputs.
Non-Shaped Video — Any full-raster (full-screen) video that has
not previously been processed by a key signal. This is also
sometimes loosely defined as Unshaped Video. Video sources
from devices such as cameras are usually full-raster video and
thus are non-shaped. These sources are not usually accompanied
by key signals.