THOMSON GRASS VALLEY KayakDD-1, Руководство пользователя

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KayakDD - Digital Production Switcher
2.10.2 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.
The appropriate key mode for this type of signal is the additive key.
If a key fill does not match the hole in the background (like in the matte key example
above), the key fill needs to be shaped by the switcher. By multiplying the key fill signal
with the key control signal the unwanted areas of the fill can be made black, shaping
the video to match the hole before it is summed with the background. Key fill video
must be shaped using the key cut signal actually used to create the hole in the
background. Video shaped with a different key cut signal will not key correctly.
The appropriate key mode for this type of signal is the Linear key or Luminance Key.
See section 2.10.17
Properly and Improperly Shaped Video for more information.
Note that an unshaped signal viewed directly will show harsh edge artifacts due to
dividing by a small number. This is normal and expected.
Keying this signal will clean up its appearance.
2.10.3 Key Control Signal Adjustment
During keying, the selected key cut signal can be converted into a key control signal. It
is the key control signal that actually cuts the hole in the background video. Adjusting
the key control signal (Clip and Gain) is essential in the keying process. The art of
setting up a good key is to use just enough Gain to suppress any imperfections in the
incoming key signals.
Setting Gain too high can cause ragged key edges.
The KayakDD system provides two methods for adjusting the key control signal, Clip
and Gain, and Clip Hi and Clip Lo. Note that the same basic keying process is
controlled by either of these methods.
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