Grass Valley Kayenne v.3.0 - Manual (Page 40)

40 KAYENNE — User Manual
Section 2 — Concepts
shape to cut a hole in the background video. The keyer then shapes the key
fill to precisely match the logo-shaped hole cut in the background and fills
it with green matte video. This creates a green logo inserted into the back-
ground (
Figure 13 ). Because luminance values of the key cut signal are
used to cut the hole in the background this is called a luminance key.
Figure 13. Matte Fill Luminance Keying Example
In this keying discussion illustrations rather than actual screen images are
used for simplicity, and because the printing process has difficulty cap-
turing the subtleties of soft key edges.
Shaping Video
In the matte key example above, the key fill signal was a full raster color
that did not match the shape of the key cut signal. This key fill signal is
accurately called non-shaped video, but may also be referred to as unshaped
video since both signal types are processed identically during keying.
Some external devices (e.g., character generators) provide a key cut signal
and an already processed companion key fill signal. A key fill signal that
correctly matches the key cut signal is called shaped video. During keying,
properly shaped key fill video can be summed with a background signal
(with a hole cut) and achieve the desired result. When the shaping is per-
formed by the source device, the Kayenne system can use a standard clip
and gain setting defined during system configuration to create the key cut
control signal, and so relieve the operator of having to adjust clip and gain
manually.
Key Cut
Key Fill
Background
Background with Matte Key Inserted
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LOGO LOGO
LOGO LOGO