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Chapter 13 LIVEMATTE
Although its controls are deceptively simple, TriCaster’s LiveMatte™ employs powerful
chromakeying technology capable of extremely high quality results. Used alone or in
conjunction with TriCaster’s DSKs, M/E Overlays and LiveSet features, you will find
LiveMatte can play a ‘key’ role in your live productions.
As we mentioned earlier, chromakeying –
or simply “keying” – is used
to combine images by
eliminating a portion of a
foreground image
(effectively cutting a digital
‘keyhole’ in it) to reveal
another background. TriCaster
®
also
relies on this method to insert talent
seamlessly into virtual sets via LiveSet™.
LiveMatte™ controls are located in the Input
Configuration panels for every Switcher
source. To access them, click the Configure
button (gear) that appears above an onscreen
monitor in the All Monitors tab. The second tab
in the (source) Configuration panel is labeled LiveMatte.
The method by which part of the image is defined as transparent is generically referred to as chromakeying,
for its dependence on the color values (chrominance) of the video stream.
(LiveMatte algorithms actually go well beyond simple chromakeying techniques to provide support realtime
results, but for our discussion it’s not necessary to get into all of the details; suffice to say it works very well,
and is easy to configure.)
Hint: Crop controls in the Input Settings tab can serve as a ‘garbage matte’ tool for chromakey sources.
SECTION 13.1 CHROMAKEYING
Chromakeying 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 almost certainly posed in front of a green
screen. The background is ‘keyed out’ and replaced by
computer generated imagery.
FIGURE 13-1, SHOWING TRICASTER 8000
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