videoComposition
A video composition to use when extracting images from assets with multiple video tracks.
Declaration
@NSCopying var videoComposition: AVVideoComposition? { get set }Discussion
If you don’t specify a video composition, the generator only uses the first enabled video track.
If specify a video composition, the image generator ignores the value of the appliesPreferredTrackTransform property.
Setting a video composition with any of the following attributes generates an exception:
A renderScale not equal to
1.0.A renderSize with a width or height less than
0.A frameDuration that’s invalid, or less than or equal to zero.
A sourceTrackIDForFrameTiming less than zero.