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Masking
From Chewiki Archive - YouChew:
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This article describes a recognised Poopism: a method of video editing that has been used by a number of poopers.
In Brief
Masking is using masking/cropping tools to cut out characters or objects to be moved around or placed in random locations. The masking tool is only avalible in pro versions of Sony Vegas.
Usage In Poop
Sometimes the masking tool is used to crop out a character and replace the backround. Sometimes the backround is left completely normal while the character or object has a bunch of effects unloaded on it. Other times the object is repeted across the screen to imitate a glitch.