Apple Final Cut Pro X (10.1.2) - Manual (Page 372)

Chapter 11 Keying and compositing 372
Compositing
Compositing overview
Compositing refers to combining parts of two or more video clips into a single image.
There are a number of ways to combine video images in Final Cut Pro:
•
Transitions: All video transitions involve combining the end of one clip with the start of a
second clip, which results in a combination of the two clips appearing at the same time during
the transition.
•
Keying: All keys involve compositing a foreground image over a background image.
•
Alpha channels: Many computer-generated video clips have an alpha channel—a built-in
mask—that defines precisely the areas of the clip that are composited over a background
clip. These require no key setup and generally just automatically work. Many effects, such as
Transform and Distort; generators, such as Shapes and Timecode; and titles use alpha channels.
•
Compositing: Each video clip in the Timeline has a set of Compositing settings. These are used
when you want to combine clips without using the key effects.
Use alpha channels
Alpha channels provide an easy way to composite one image over another. Using an application
like Motion, an Apple application designed to work with Final Cut Pro, you can create still images
and video clips that have alpha channels. Alpha channels can be thought of as having a built-in
keyer—when you use the key effects you are creating a mask that is used in the same way a clip
with an alpha channel is used for compositing.
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