Server Version#: plexmediaserver-1.22.1.4228-724c56e62.x86_64
Processor: Intel(R) Xeon(R) CPU E5-2470 0 @ 2.30GHz
OS: CentOS Linux release 7.9.2009 (Core)
So I’m running a server with a hardware raid controller w/ 8x 6TB, 8 core xeon proc, 48Gb of memory, fairly solid little machine. When I try to play some 4k videos, every core starts rockin at 100% and my roku alerts me that the server is insufficient to process the video. I’m only trying to play 4k video’s locally on my LAN over wifi, connecting using 5Ghz channel.
Is the issue with my proc? Or potentially the format of my 4k video file? I feel like my processor may be a little older, but seems like it should at least be able to handle 1x 4k video at a time.
It seems you are transcoding, transcoding 4k is not something you wanna do.
Your CPU is almost 8 years old, it’s likely it is not powerful enough for a single 4k transcode.
Divided across 16, that’s just over 500 Passmarks per thread.
H.264 transcoding will use about 3 threads and use about 2000 passmarks per 10 Mbps of video.
H.265 on the other hand is about 4000-5000 passmarks for the same 10 Mbps video.
Now add the overhead of audio (1-2 threads if 7.1 → Stereo conversion)
Also add one dedicated thread (this is where speed is of the essence) in burning subtitles (if needed).
Any subtitle burning must have a fast per-thread speed to keep up with burning the text image into each video frame being output.
This CPU is not fast enough for 4K. Combining 3 cores (HEVC is a 3-thread task) yields 3000 Passmarks which might allow for a 5 Mbps 4K video stream at most.
These older Xeon CPUs were designed for multi-threaded web & file server type operations , each of which were simple tasks. Video is computationally intense and not within what they excell at. The newer CPUs were / are designed to handle these loads.
I think you’ll be amazed at what a single Core i5-10xxx CPU can do at a fraction of power / heat & cost because it supports video transcoding in hardware.
Just to help clarify, if your CPU is being maxed the video is likely Transcoding. Transcoding generally happens when you’re trying to play a file on a device that’s not compatible. The Plex Server converts it on-the-fly to a video type that is compatible. In general you want to avoid Transcoding 4k videos as there will be some quality degradation on top of the very heavy CPU requirements
Your best bet is to figure out why exactly the file is being Transcoded in the first place. There’s something about the file that’s not compatible with your Roku. Some possibilities are the video codec, the H264/H265 profile level, the number of reference frames, and very often the subtitle format (if you have them enabled). If you post the text of the Plex Media Info XML for that file we might be able to help you pinpoint a possible cause (we just need the text before </Media>)
A screenshot of the expanded Now Playing info for the video also helps. Once you figure out why the file is Transcoding you’ll be able to better fine tune your setup. I once had to swap out an old Roku for an Amazon Firestick because the majority of my media library had a high amount of reference frames which were causing issues with that older device.
