Although I have two 128G XQD cards for my FS7 (still waiting for another 2) recording XAVC I on 4K 50p is time limiting so I use LongGOP which almost doubles your card time. FCPX does not look at XAVC L footage so you have to bring it in using 3rd party software.
I took my 4K footage into Sony’s Catalyst Prepare expecting to transcode to ProRes 4K 50p to discover your maximum ProRes render preset is full HD !
Not to be outdone I hunted Catalyst and remembered FCPX takes XAVC I frame footage…the answer…till I discovered after about an hours transcoding 8 files that I was ending up with document files !!! Sony have been made aware of this but it does not stop here…
As a back-up I have my Ultra Studio 4K running Media Express, now the latest firmware upgrade 10.3.7 brought 4k 50p…no problem I was covered. Sadly as I discovered it does not work, yet. Blackmagic told me they were aware of this and are updating the drivers this month to 10.4.7, so I hope I will have a solution to my problem.
I am using 4K to cut in and out of during an interview, making it look like a 2 camera shoot, this saves using 2 cameras cutting down on production costs.