Tektronix Grass Valley 3000 - Manual (Page 223)

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NOTE: This appendix applies specifically to the Model 2200,
Model 3000, and Model 4000 Switchers, but the general principals
discussed here may apply as well to other switchers and other devices.
Introduction
The purpose of this appendix is to explain what shaped video and
unshaped video are, where and why they are used, and what you
need to do so your equipment will handle them properly.
What are Shaped and Unshaped Video?
Shaping and unshaping are generally involved only in keying and
compositing situations.
Whenever a key is performed, there are always three signals: the
key source, the key fill (fill video), and the background video. The
key signal cuts a hole in the background, into which the fill video
is inserted. Devices such as character generators often output both
the key signal and the fill video.
Appendix A —
Shaped and Unshaped Video
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