This is a question I had when I was putting a server together: how well will an i3-7100 (HD 630 graphics) handle transcoding and particularly, tone mapping under Linux? Well I assembled the server and tried it so I figured I should answer my own question for the benefit of future searchers.
Using a 47 Mbps 4k HDR remux as the test subject, I opened many Plex browser windows and tried playing the movie back in parallel, at 1080p SDR 20 Mbps. Plex server and the NAS with the files and the playback computer were all on gigabit Ethernet.
Short version: Rock solid playback with 3 or fewer simultaneous tone mapped + transcoded streams. Tautulli speed numbers ranged from 1.5 to “throttled.” (They changed frequently.)
Longer version: Playback at 4 streams looked OK but the Tautulli Speed rating on one or another stream was usually below 1.0, others were around 1.5. However, I didn’t SEE any problems. It may have been on the ragged edge, though. At 5 streams there were occasional pauses so it was unwatchable.
Other notes: The image quality of the hardware accelerated tone mapping was not as good as non-accelerated CPU mode. Color and contrast were a bit more muted. It’s OK overall but I would welcome any way to turn knobs and adjust the final image, if that was possible. If anyone can comment about more recent CPUs having an improved appearance I would like to hear that too.
And lastly, I set the transcoder directory to ramdisk (/dev/shm) and saw that each concurrent stream took up about 800 MB RAM. On a 8 GB i3-7100 system I ran out of Quick Sync tone mapping performance well before I ran out of ramdisk.
