Hi.
I am working with Final Cut Pro X 10.3.4 and i imported a video file that is showing me pixelation too.
With vlc and quicktime runs the video good without any problem (i checked frame by frame).
Final Cut Pro X 10.3.4 shows me this pixelation even in the preview import window.
I get the same result with the video in the project window then.
What may be the problem here?