I had a post on this earlier, and I thought I had it figured out. However, my latest silly App is landscape, and the same tricks don’t seem to work to force a nice 1920×1080 video.
After a little google work, I found this handy answer on SO:
Using FFPMEG, it’s possible to scale up the video. It seems you need to oversize it and then crop it. The following commands are from the SO answer:
ffmpeg -i video.mov -filter:v scale=1084:1924 -c:a copy video_1084.mov ffmpeg -i video_1084.mov -filter:v "crop=1080:1920:0:0" -c:a copy video_1080.mov
I ended up using slightly different commands, I was coming from a iPhone 6 landscaped video, so I needed to scale my output to 1928×1084 and then crop it to 1920×1080. I also used .mp4 as the extension, as this is what iMovie exported them as.
Just as a side note, I don’t like making a fake iPad video, so I just record the gameplay with Quicktime and knock out a specific iPad version. It’s limited to 30 seconds, so it’s not like its a ton of extra work.
Hope this helps someone else out there.