as_909 Jan 2, 2018 1:43 AM
Finally able to conduct some tests today with a 3 minute, 18-second H.264 clip (1080p, 8-bit 4:2:0, 29.97 fps).
Old Mac (2012 12-Core Mac Pro, 32 GB RAM, Radeon HD 5870 1 GB). Source drive read speed of 100 MBps. Destination drive (separate) a write speed of around 120 MBps. Conversion would have taken around 45 minutes (I stopped it at the 6-minute mark and it had around 40 minutes left to go).
New Mac (2017 10-Core iMac Pro. 64 GB RAM, Radeon Pro Vega 56 8 GB). Source RAID read speed of 600 MBps. Destination RAID (separate unit) a write speed of 400 MBps. Conversion took around 56 seconds.
I just used Apple's 'QuickTime Player' to do an export to 1080p while checking the HEVC checkbox. Both systems also running the same macOS (10.13.2).
Thus, you'll really want a Mac with hardware acceleration for HEVC. And while my new storage is drastically faster in the new Mac, this test wasn't I/O bound. But, I wanted to reveal all the details.