An array of instances of
AVVideo that specify how video frames from source tracks should be layered and composed.
- iOS 4.0+
- macOS 10.7+
- Mac Catalyst 13.0+
- tvOS 9.0+
Tracks are layered in the composition according to the top-to-bottom order of the
layer array; the track with trackID of the first instruction in the array will be layered on top, with the track with the trackID of the second instruction immediately underneath, and so on.
If the property value is
nil, the output is a fill of the background color.