With latest Kaby Lake line Intel introduced new HD630 graphics. This piece of hardware is capable of hardware decoding up to EIGHT simultaneous 4K 10b HEVC 30p streams. In other words: ~$200 CPU could do a better job than those extreme dual xeons setups.
But… it needs support from developers. Are you, creators of Plex, going to look into it?
I am really looking forward to get i5-7400 with B150 board for ~300 and call it a day. If H265 HEVC hardware encoding would work in Plex, then I wouldn’t have to worry about transcoding any movie I will drop at this CPU/iGPU combo for the next few years.
Don’t depend on hardware decoding if you care about video quality, though. You will be sorely disappointed.
I suppose it might be tolerable if you watch on tiny screens which hide the low quality, or if you’re so young that Youtube is the baseline now for you as to what “quality” is.
