Follow these stabilization best practices to avoid video with black bars along the edges or upside down video.
- In the Video inspector, reduce the value in the appropriate smoothing parameter (Transition, Rotation, or Scale) in the Stabilization section.
- Cut the clip with the Blade tool or trim the clip in the Timeline to remove sections with most excessive shake or extreme camera moves. You can locate the sections of excessive shake in the Tags section of the Timeline Index. Click on the individual Excessive Shake tags to select the corresponding ranges in the Timeline.
From Final Cut Pro X Help: