Since I have both the Sony FDR-AX100 and Premiere Pro CS6, I checked to see if Premiere Pro CS6 could ingest the h.264 (.MP4) files recorded in 4K by the AX100. I had no problems importing the files form the AX100 or playing them back with no dropped frames in Premiere Pro CS6. Note that I was using Premiere Pro CS6 on a late 2013 Mac Pro equipped with 12 cores, 64 GB of RAM, and two AMD D700 graphics cards
Tom