GRASS VALLEY zodiak, User Manual

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Zodiak User Manual 51
Keying
S-Shaped Key Signals
On the Zodiak system, an S-shaping function is applied to the edges of
luminance keys. S-shaping smooths the sharp corners of a luminance key
control signal, which helps prevent banding artifacts. S-shaping a signal
minimally affects the key edges, and does not move key thresholds or affect
the overall gain of the key (
Figure 19 ).
Figure 19. S-Shaped Luminance Key Control Signal
S-shaping is generally not applied to linear keys because the external
device usually applies an S-shaping function when it generates the key cut
and key fill signals. S-shaping should not be applied twice.
Additional Keying Controls
The following additional controls are available for keying.
Key Invert
Keys can be inverted, causing holes to be cut in the background where a
normal key retains the background, and vice versa. Key invert makes the
white areas of the key cut signal produce transparency, and the black areas
produce opacity, the opposite of a standard key.
Masking
Masking defines areas that are protected from keying (Inhibit Mask) or
always key (Force Mask). The shape of the mask can originate from a wipe
pattern generator or by a selected mask signal (typically a key fill signal
delivered via one of the Utility buses).
With the Zodiak Still Store, the mask signal can be a frozen page of video
or a key fill. Complex mask shapes are often easier to draw by hand than to
create with multiple wipe patterns.
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Key Control Signal
S-Shaped
Key Control Signal