iMovie can't handle iPhone X App Preview size?

If you have ffmpeg on your system here is an Automator app that you can drag your iPhone X captured 60 fps video and convert it to 30 fps:

https://drive.google.com/open?id=19tZxbvIv3WJpriXPQhVcJvbkxS28D0oF

For those interested in the code, here is the applescript:

on remove_extension(this_name)

if this_name contains "." then

set this_name to (the reverse of every character of this_name) as string

set x to the offset of "." in this_name

set this_name to (text (x + 1) thru -1 of this_name)

set this_name to (the reverse of every character of this_name) as string

end if

return this_name

end remove_extension

on run {input, parameters}

repeat with file_ in input

tell application "System Events"

set inputFilename to name of (get properties of file_)

end tell

set inputFilePath to quoted form of (POSIX path of file_)

set outputFilePath to quoted form of (my remove_extension(POSIX path of file_) & "_30.mp4")

tell application "Terminal"

activate

do script "ffmpeg -y -i " & inputFilePath & " -vf 'setpts=1.0*PTS' -r 30 " & outputFilePath

end tell

end repeat

return input

end run

It appears that oniPhone X a preview video from a different size of iPhone will be seen to play in the list of apps, but it is not available if you tap on the app for more information. (Thus you can't see it fullscreen, or hear it.)

I have used handbrake (www.handbrake.fr), it's a free, useful video editing tool, to change the resolution of my iMovie file to be 886 x 1920 and then upload it to the app store. This isn't a perfect solution since it will alter the aspect ratio, but may be sufficient for some app previews e.g. games etc and some may find it less hassle than some other methods. The interface is not super user friendly, but it is quite a powerful tool and there is a tab for altering the output resolution. I'm not affiliated with handbrake - I used it years ago to rip my personal DVDs to video files, however I believe in recent years it has lost some of it's ability to circumvent DVD copy protection, so isn't as "popular" as it once was in the video editing scene.