Here is one way to rotate a video clip using Final Cut Pro:

The gist of it:

  • Create a new library
  • Import the movie
  • Note the current dimensions with the Inspector pane (Info tab): e.g., 640x480
  • Right-click clip in the browser and choose "New Compound Clip"
  • Video Properties -> Custom -> Custom -> 480 x 640 (note the swapped width/height)
  • Double click the new compound clip in the browser (or right-click and choose "Open in timeline"); this will open it in a timeline
  • Select "Transform" in the preview window
  • Rotate the clip: grab a top, bottom, or side handle; hold shift down; resize to fit into the new dimensions
  • File -> Send to Compressor
  • In Compressor, select the next highest size that will fit the video's widest dimension
  • Manually set the Video properties to exactly what they should be (e.g., 640x480)