As most of us know that own either of these when you try to put a 4k video on your device from your Mavic you get a " Unsupported Video Format " so i have been looking online to see what is out there and found this. Play 4K video on your iPhone 7 – new method of 2017 | Softorino just plug your device in drag your 4k file into application and it loads in seconds then its in your video app on your ios device. you get a 14 day free trial then a lifetime license for £15.90 / $19.95. just thought id share this.

Sucks....def can view my 4k files when i transfer them too  my s8+

But your stuck with Android

4K videos playback fine on my iPad mini 2, however it does get downsampled.  but i have tested a 150mbps 4K file i made in premier...  its not terrible intense but it will choke out an i7-6700K's iGPU/software decoder..even if screen res is sub 1080P,  but somehow it runs fine on a SoC apple made in 2013, in a discontinued iPad mini 2...

that being said Apple's iDevices tend to be more picky about Codec's used on local storage (in library), only sure fire way around this i found is to resort to old school method of plugging iDevice into iTunes transferring the file that way..  other methods i found that can work is using google photos/drive upload from ur PC to that service then  on your iPad/iDevice select the file and download...its a super roundabout way, but it works..  and quality as long as you select original in settings not "hi quality"
it will be effectively 1:1 but without that annoying support issue..  

and luckily for me i have doubled down on promotions.. i have 250GB free on google drive.. one was LG promotions with my AMOLED 4K TV (no idea was even a promotion involved, 150GB free for 2 years) and other was samsung Galaxy S8 activation for 100GB free for 2 years..

What is the point of putting 4K onto an iPhone, you would notice the difference between 4k and 1080 on the display and is a hell of a lot nicer to manage / play with.

Used the same app to put HEVC videos on my iPad. But it seems like only WALTR 2 (second version) supports them. So this means you can even put 4K videos that are in h.265 on your iPhone.

There are 3 main reasons why you fail to play 4K video on iPhone or iPad:
1. No iPhone offer 4K resolution displays
2. iTunes can’t sync 4K video to iPhone
3. 4K video is too storage consuming

For those consideration, I think the best way to play 4K video on iPhone/iPad is to compress 4K to 1080p  720p or other file resolution according to your iPhone device display screen resolution for getting the optimal playback experience.

Shoot in 4K, download files to your phone with 'Sync for DJI' app, and then export files to iMovie or somewhere else.  The app supports all file types and works even in the background.Also app can trim a part of video before download and download only the best part of large video file.