Since upgrading to Catalina, my iMovie exports have random glitches - pixelation for about 1 sec or less. I reexport and get another glitch in another location. If I'm lucky, the 3rd or 4th try comes out clean. A post elsewhere suggests setting my iPhone transfer to Mac to Automatic. That was done long ago but the issue remains. Image here shows the glitch does not appear in iMovie preview window.
The pixelation issue has been brought up several times on this forum. It seems to have some correlation with iPhone photos or videos taken and exported in the HEVC format. The Automatic setting should have solved that, but apparently it did not in your case.
You might try using a video converter like the free download, Handbrake, to convert your clips to H.264, Mp4/AAC that Handbrake will do by default. Do this even if your clips are already in that format. Then import the converted clips into a new iMovie project and see if you can export without pixelation.
-- Rich
The pixelation issue has been brought up several times on this forum. It seems to have some correlation with iPhone photos or videos taken and exported in the HEVC format. The Automatic setting should have solved that, but apparently it did not in your case.
You might try using a video converter like the free download, Handbrake, to convert your clips to H.264, Mp4/AAC that Handbrake will do by default. Do this even if your clips are already in that format. Then import the converted clips into a new iMovie project and see if you can export without pixelation.
-- Rich
We had a long discussion about this issue here:
https://discussions.apple.com/thread/250751600?page=1
I was really hoping for a fix with today's updates for imovie (10.1.14) and Catalina (10.15.2), but the glitches are still there - anyone with different experiences?
Random pixelation in exported videos
