NewTek 3Play 3P1, Руководство пользователя

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REVERSE KEYING
Figure 163
3P1’s Reverse Key feature is found in the Output A and Output B tabs. Let’s talk about the underlying
technology of this feature, which is generically called “chromakeying”, or simply “keying”.
Keying has become an essential tool in video and film production. Typically, foreground footage is shot in
front of a blue or green screen, and then that background color – the key color – is treated as transparent,
allowing another image to be inserted. For example, when you see a television meteorologist in front of
a weather map, that person is usually posed in front of a green screen. The green background is ‘keyed
out’ and replaced by computer generated imagery.
3P1 uses a more advanced version of this technology, referred to as ‘Reverse Keying’. Using a designated
background color as the key color, 3P1’s Reverse Key allows a DSK source (such as a Telestrator output or
graphic) to be ‘sandwiched’ behind foreground-colored pixels, but (unlike the weatherman application) in
front of the original background – rather than replacing it completely.
Hint: If the associated DSK is displayed (‘on’), Telestrator output will appear behind the foreground on
3P1’s output (A or B) when Reverse Key is enabled. When Reverse KEY is off, Telestrator output appears
in front of the source assigned to the output when the DSK is displayed.
The controls in the Reverse Key group allow you to toggle the feature on/off, and define and adjust the
key color values applied to the video output. These settings are discussed next.