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Kurkoko

Plex and Ryzen cores

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Hi,

I watched a video from "bite my bytes" youtuber about his new Ryzen build comparing a 3700x, 3900x and a P2000.

He claims being able to transcode lots of movies at the same time but I'm not sure about how many cores uses on the Plex dock.

 

Does someone here with Plex can share his experiences with Ryzen cores? I mean how many cores you use on Plex dock appliance and how many 1080p movies got able to transcode?

 

Thanks!!!

 

 

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TL;DR - I don't think his result is different from the expected performance of Ryzen.

 

You can actually get a pretty decent estimate from the passmark score and the relative complexity difference between 4k vs 1080p and H265 vs H264.

Each 4k H265 stream needs about 7500-8000 passmark => each 1080p H265 stream about 1800-2000 => each 1080p H264 stream about 1000.

 

Note: the above only applies to CPU after about 2015 when H265 hardware accelerated video became a thing.

For CPU before 2015, you need to multiply the passmark by 2, hence, the 2000 passmark per stream general advice.

I think there was also a period before 2015 that H264 was accelerated but H265 was not and AMD implementation was different from Intel etc. but that is overly complicating things. We are estimating, not calculating the trajectory of a nuclear missile.

 

So just to estimate from my 2990WX, which has about 23200 passmark.

  • I only use 1 bank of the hyper-threaded pairs for Plex and an additional hyper-threaded core adds about 30% performance so using 1 bank drops my (estimated) score to 17800.
  • I only use half of the cores (let's ignore NUMA problem for now), so I'm down to about 8900 passmark for my Plex.

So based on the estimate, I should be comfortable with 1x 4k stream or 4x 1080p streams - which is very much consistent with my own experience.

 

If I ever have to do more than 2 4k streams simultaneously, I will certainly get a P2000 and donate a few beers to Unraid Nvidia guys.

Edited by testdasi

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Thanks for your answer

So if I understood your post correctly, being a 3700X a 23860 passmark.
Using 1 of the 8 cores should be about 2982 passmark so about 3 h264 or 1 h265?

He performs 24 h264 streams on a 3700X that us about 994 passmark per core. So It seems correct.

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10 hours ago, testdasi said:

You can actually get a pretty decent estimate from the passmark score and the relative complexity difference between 4k vs 1080p and H265 vs H264.

Each 4k H265 stream needs about 7500-8000 passmark => each 1080p H265 stream about 1800-2000 => each 1080p H264 stream about 1000.

Double that values. Here you'll find the official Plex requirements:

 

https://support.plex.tv/articles/201774043-what-kind-of-cpu-do-i-need-for-my-server/

 

 

What you'll find there:

 

4K HDR (50Mbps, 10-bit HEVC) file: 17000 PassMark score (being transcoded to 10Mbps 1080p)
4K SDR (40Mbps, 8-bit HEVC) file: 12000 PassMark score (being transcoded to 10Mbps 1080p)
1080p (10Mbps, H.264) file: 2000 PassMark score
720p (4Mbps, H.264) file: 1500 PassMark score

 

 

I can confirm these official and higher values. And don't forget - lot's of new 4K material needs more than 50Mbps. I've seen one 4K movie with a peak of 100Mbps - that even maxes out the 100Mbps LAN port of traditional TVs and hardware players. And who the hell thinks that 1080p comes at 10Mbps? My library average for thet resolution is beyond 15Mbps.

 

My 2x 2860 v2 with a total of ~31,000 maxed out at two parallel 4K transcodes without a dedicated graphics card.

 

For example, with a dedicated Nvidia 1050ti two 4K transcodes can run on the graphics card. And the CPU cores are free for the rest.

 

Edited by hawihoney

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54 minutes ago, hawihoney said:

Double that values. Here you'll find the official Plex requirements:

 

I can confirm these official and higher values. And don't forget - lot's of new 4K material needs more than 50Mbps. I've seen one 4K movie with a peak of 100Mbps - that even maxes out the 100Mbps LAN port of traditional TVs and hardware players. And who the hell thinks that 1080p comes at 10Mbps? My library average for thet resolution is beyond 15Mbps.

 

My 2x 2860 v2 with a total of ~31,000 maxed out at two parallel 4K transcodes without a dedicated graphics card.

 

You didn't read my entire post, did you?

 

I specifically mentioned: "For CPU before 2015, you need to multiply the passmark by 2, hence, the 2000 passmark per stream general advice."

Your Xeon E5-2680 v2 (there wasn't a 2860 so probably a typo there) came out in 2013.

 

The OP asked specifically about Ryzen (which came out in 2017) so I am comfortable with providing the post-2015 estimate and, even so, tried to protect myself with a specific statement about CPU before 2015.

 

Your point about bit-rate, while valid, is also missing the point about the estimate.

  • The Plex 2000 passmark estimate is conservative to begin with because Plex doesn't want people who skim and blame their (official) guidance that their exactly-2000-passmark CPU can't handle a 20Mbps 1080p stream.
  • Peak bit rate is the reason why we have buffer. The passmark estimate is based on average because with a buffer, the peak is evened out by all the time that the bit rate doesn't reach 50Mbps.

Let me quote myself again: "We are estimating, not calculating the trajectory of a nuclear missile."

 

 

2 hours ago, Kurkoko said:

Thanks for your answer

So if I understood your post correctly, being a 3700X a 23860 passmark.
Using 1 of the 8 cores should be about 2982 passmark so about 3 h264 or 1 h265?

He performs 24 h264 streams on a 3700X that us about 994 passmark per core. So It seems correct.
 

I would say 1x H265 or 2x H264.

3x H264 depends on the actual vids.

 

My 2990WX on a single core (provided it is on the NUMA node with memory controller) can do 2x H264 1080p streams at about 95% load and its single core passmark is 2072 LOL.

Edited by testdasi

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Thanks for all your help!

I'm still thinking about upgrade my unraid server and needs to be green becouse here electricity is expensive.

Ryzen is a great option to my usage. But was scared to loose so much cores on my Plex. Just need 2 concurent transcoding. Actually using an old i7T 35w 4/8 and igpu manages Plex

With a 2700x with only 65w can manage my actual usage and leaves free cores for daily working Windows 10 VM.

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