I was wanting to transfer a few videos from to my iPad that were on a USB Flash Drive for later viewing. I happened to have a Lightning to USB 3 “Camera” Adapter, and thought, “Hey, this will be handy!” I plugged the adaptor into my iPad and the flash drive into the adaptor. The iPad automatically launched Photos to import from the Flash Drive, but I was quickly told my flash drive was empty!
I googled the issue, and found that others were having the same issue.
Luckily, they proposed a solution: because the adaptor is a “Camera” adaptor it excepts files to be named using the DCF system. Simply put, the Flash Drive should have a folder called “DCIM”, and the name of the file should be exactly 8 characters long without the extension (no spaces), just like a camera created it. (For example, DCIM\my-movie.mp4.) Voilà, plug in the flash drive and now it allows me to import the videos!
Sadly, the video only import into the Photos app, rather than Videos. But, it still allows you to view the video.