My server is a bit up there in age.  Running and AMD 1045T 6 core server, playing back on Roku 3.  I know the roku 3 is not technically compatible with 4k video, so I have set plex to transcode as low as 720p and it still buffers every minute or so.  But I can't figure out if this is a result of the Server, the cache drive transcode location, the roku itself, or a network issue.

 

From a CPU standpoint, I do not see the CPU hitting 100% utilization during the transcode process

 

The cache drive transcode location is an SSD

 

My AP is a Cisco 3700 That should have no issues serving up this content.

 

 

So I am appealing to the minds of the unraid community, hoping someone has seen this before.

 

Oh, there is one more thing.  I am still using that supermicro AOC HBA that was in every unraid build 10 years ago.  I know people have been moving away from those.  Could that be causing this behavior?

Edited June 19, 20188 yr by wisem2540

It's more than likely the CPU, IMO. If you can serve up regular H264 content wirelessly without buffering, then yeah, I'd say it's the CPU.

You may want to ssh into your unRAID server before it serves up the 4k video and run htop and sort by CPU. Then start playback of your file. If you see your CPU usage skyrocket, then it's the CPU.

Just as a frame of reference, my unRAID 6.5.3 server is an i3-8100, 32GB 2400MHz, and has the iGPU transcoding hack enabled, and it still pegs the server at around 20% on each core with a 50Mb/s HEVC file going.

6 hours ago, anhloc said:

You may want to ssh into your unRAID server before it serves up the 4k video and run htop and sort by CPU. Then start playback of your file. If you see your CPU usage skyrocket, then it's the CPU.

Just as a frame of reference, my unRAID 6.5.3 server is an i3-8100, 32GB 2400MHz, and has the iGPU transcoding hack enabled, and it still pegs the server at around 20% on each core with a 50Mb/s HEVC file going.

 

 

Thanks.  I just tried a 1080p h264 rip @ 10.7M and it does the same thing.  I ran Htop just to see and unsurprisingly, it did not get out of whack.  So I definitely have a deeper issue that just started cropping up.  

 

We also tried this from one of our mobile phones, so that rules out the roku, and I don't have any reason to believe that my router or AP are having any issues.

 

However, two things I have noticed in the not-so-distant past were my Supermicro controller "crashing" during a parity rebuild and also occasionally my windows VM will error out on large file copies and I have to use putty to do them through command line. 

 

So this leads me down the path of either a controller issue perhaps, or maybe even a bad SSD

Edited June 20, 20188 yr by wisem2540

@wisem2540 -

 

Your CPU has a passmark of about 4800. That would make transcoding HEVC streams in real time very unlikely. But you should be seeing the CPU getting heavily utilized. If you are not you are likely having other issues.

 

Just for reference, I have an i9 7920x (12 core / 24 thread), each running at 4.5Ghz. I am able to transcode one 4k HEVC stream using between 1/3 to 1/2 of the CPU. Have never tried 2 at a time, but might be possible. The passmark is estimated at about 29,000. (Note my CPU was delidded to improve cooling, and able to run at 4.5GHz with all cores active, unlike stock chip that is limited to 2.9Ghz when all cores are active).

 

If the CPU is not hitting high utilization, the first thing you might want to check is where the transcoded output is stored. The best place is to have it stored in RAM. (See HERE). If you are transcoding to an SSD, it might be slowing the transcode mildly to moderately impacted. Worst if the SSD routinely gets a lot of writes and has not been TRIMmed in a while. And if you are transcoding to an array disk, you could definitely expect a very significant performance hit that would result in lower CPU utilization due to waiting on the disk I/O.

 

If you are transcoding to RAM and still not seeing high CPU usage, it could be that the number of cores available to the PLEX docker container is limited. I tend to give Plex access to all the cores (except Core0), and also give my Windows VM access to all cores (except Core0). Since it is rare that my VM is going to be doing something processing intensive while I am watching a movie, and vice versa, this is basically giving both Plex and my VM access to 11/12ths of the processing horsepower of my CPU.

 

A third thing to check - sometimes a player may "advertise" to Plex that it has the capability to directly play back an HEVC stream, when it is really not able to do so in real time without glitching. You can look at Plex Web GUI while an HEVC video is playing and see if it is transcoding or doing direct play. I was seeing HEVC streams lagging and couldn't understand why, and found that Plex was NOT transcoding, and instead depending on my old Brasswell NUC to be able to play it back - which it is not able to do with 10bit HEVC. Disabling direct play in the player made Plex do the transcode, and then my full server horsepower was available to transcode, and the NUC could play it back perfectly smoothly.

 

Can't really think of other reasons your CPU would not be pegged trying to transcode an HEVC steam.

If you have the RAM free for it, can you try transcoding to RAM?

If not, have you run TRIM on your SSD (if it's supported?)

7 hours ago, anhloc said:

If you have the RAM free for it, can you try transcoding to RAM?

 

As I recall, the real-time transcoding does not store the entire transcoded file, but only a buffer to support the playback.  Might want to confirm, but that's what I remember, so the RAM needed is not outrageous.

 

12 hours ago, SSD said:

 

As I recall, the real-time transcoding does not store the entire transcoded file, but only a buffer to support the playback.  Might want to confirm, but that's what I remember, so the RAM needed is not outrageous.

 

 

That's good. In that case, it should still work well to help find the issue here.

Thanks guys.  I will try transcoding to RAM to rule out the SSD.  I can confirm on the actual 4k video is definitely a CPU issue.  For the 1080p video I mentioned earlier, im betting that is an SSD problem

Any update on this wisem2540?