iMovie has been upgraded to support 4K video resolution as well as 1080p60 previously only unofficially supported.
It imports successfully from Sony XAVC and Panasonic 4K Mp4
The files are copied as is without conversion and can be converted in prores if you have the codec. The high quality output works at around 30 Mbps probably set for youtube optimised streaming. You can increase bitrate to 40 mbps
Release notes
What's New in Version 10.1
• Create and share movies at stunning 4K resolution (3840 x 2160) on compatible Mac computers (1)
• Create and share movies with 1080p HD video at 60 frames per second for smoother, more true-to-life action
• Import movies and trailers from iMovie for iOS (version 2.2 and later), so you can start editing on an iOS device and finish on your Mac
• Redesigned Media view lets you see more of your library while browsing videos and photos
• Projects view makes it easy to find and open your movies and trailers
• Tabs in the Browser give you faster access to titles, backgrounds, transitions, and music while editing a movie
• Option to hide Browser while editing a movie
• 10 additional video filters from iMovie for iOS
• View pixel-for-pixel 4K video while editing a movie on iMac with Retina 5K display
(1) 4K export requires a Mac from 2011 or later with at least 4 GB RAM. Full-resolution 4K playback is supported on iMac with Retina display and Mac Pro (2013 or later) when connected to a 4K display.
