I’m using iMovie 10.3.3 on a MBP running Monterey to edit an MP4 file that was provided to me. The resolution of the file is 1922×804.
I created a new iMovie project and then imported the file.
When I drag the content from the project media section to the timeline and then simply export to a file (even without before performing any edits), the resulting MP4 file is missing a substantial portion of the left and right edges. (The Export File window’s resolution defaults to 720p; 540p can be selected; 1080p is disabled. 4K does not appear. Using the default 720p resolution, the resulting file is 1280×720.)
If I instead select the original imported content in the project media section and then export to a file, the content on the left and right edges is not lost. (The Export File window’s resolution defaults to 1280×535; among the other choices is 1920×803 — which is nearly identical to the resolution of the original MP4 file.)
It seems that the act of simply dragging the content to the timeline is causing the aspect ratio to be messed up.
How can I export from the *timeline* without losing portions of the left and right edges?
—–
Chris Waters
It is just a matter of cropping the video properly. 1922x804 is an odd size, but if it is Cropped to "Fill" then the top and bottom of the video will match the top and bottom of the frame, and the parts on the left and right will not be visible. If you Crop to "Fit" then it will all be put in the frame and you'll end up with some blank space at the top and bottom, as would be necessary.
The reason 1080 and 4K are not available is that 1080 is literally 1080 pixel high, and your video has only 804 pixels vertically.
Check out https://macmost.com/how-to-crop-photos-and-videos-in-imovie.html to learn more about cropping.
Thanks for the explanation and for the link to your video. Resolved my issue!