Super Slow iMovie Rendering

When I movie exports a project it deposits small temporary files on the desktop to assist in the rendering. The temporary files will disappear shortly after the rendering is completed, at which time the full file will appear on the desktop. Sometimes the temporary files remain for awhile. Is it possible that what you are seeing are the temporary files before they have disappeared? Sometimes they remain for awhile.

If the above is not the issue, try deleting preferences. To delete preferences, open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

You could also try creating a new project and exporting from there.

Another thing is to open in a new library by holding down the Option key as you open iMovie. You can choose a different or new library from the box that appears.

-- Rich

There might be some corruption in one of the frames or clips that is causing the export to abort. Or maybe some legacy clip that is unsupported.

Try scrolling through your timeline and look for black frames, white flashes, aritifacts and other signs of corruption Cut out any that you find, and then see if you can export fully. It helps to first use the slider above and to the right of the timeline to expand out the timeline.

You can also try redownloading iMovie from the purchases list under your account at the online app store.

-- Rich