No, maybe isn’t the entire answer. A device like this will transcode SDI or HDMI into a Thunderbolt input. An Apple Thunderbolt 2 to 3 adapter is needed to until early the USB-C port of a newer iMac. The data can be in the form of QuickTime and the Mini Recorder comes with software that will capture the input signal via the USB-C port. The software, BlackMagic Media Express is Mac compatible and should offer the quality you’re looking for at a fairly modest price.
The Blackmagic Design UltraStudio Mini Recorder allows you to capture an SDI or HDMI camera signal and transfer it to your computer for editing and other applications. The Mini Recorder features SDI and HDMI inputs and a Thunderbolt output, and supports resolutions up to 1080p30 / 1080i60. The Mini Recorder also comes with Blackmagic Media Express software, which will let you accept and encode incoming footage as best fits your workflow.
Note: A Thunderbolt-equipped computer is required for inputting the signal into your computer. Thunderbolt and SDI/HDMI cables (not included) are also required.
The "Capture" Aspect of a Capture and Playback Device
Connect to your camera by HDMI or SDI and output your footage to a computer by Thunderbolt to get the best quality footage possible into your editing system
3 Gb/s SDI Input
SDI input connection for decks, routers and cameras so you can record amazing quality 10-bit video in SD and HD
HDMI Input
HDMI input for amazing quality record direct from cameras, and set top boxes and gaming consoles
Thunderbolt Connection
Get blazing speeds for recording SD and HD up to 1080iHD