DS220+ can not transcode hdr hevc main10 files

Plex Media Server NAS & Devices
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Server Version#: 1.25.2.5319 (tried latest Plex package installed into DSM 7.1, tried also latest Docker image)
Player Version#: irrelevant, issue everywhere

Hi. I just bought new synology nas ds220+ with 6gb ram and 6tb hdd. I hoped that it is capable to transcode hdr movies on the fly, since this is mentioned in the excel provided by plex (should be capable of transcoding of UHD videos into h264 output using HW capabilities).

Unfortunatelly, if the video is HDR, the processor is used up to cca 60% (it is probably some artificial cap in case of HW transcoding, SW transcoding can achieve 100% utilization) and HW transcoding is so slow that it is unusable. This is happening both for 4k and 1080p hdr video streams (h265, main10 codec, hdr). So it is not currently capable to transcode hdr video. If the video is not hdr, it can transcode without problem (even 10 bit video is not a problem, if it is not hdr).

I tried downloading latest package from Plex and installing it as external source in package center, i also tried the Docker version with HW transcoding enabled (i am plex pass user). In both cases absolutly same behavior - transcoding everything EXCEPT for hdr.

My question is - what am i missing? Or this NAS with celeron processor is not capable enough to transcode even 1080p hdr video? (Then i dont understand why this excel from Plex says it can do UHD hdr).

Right now this server is no more capable than old ShieldTv which i wanted to replace (because it cant do hdr transcoding).

Any support highly appreciated! Thank you!

Btw just tried transcoding using Synology’s Videostation - it transcodes on the fly without any problem (cpu utilization around 40%). Just colors are off (but Plex cant do it even without Hdr tone mapping).
At least it is clear that this cpu is capable of HW transcoding of 4K HDR video. So it is probably up to the Plex team to add proper support for it…please

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Are you using subtitles? Subtitles require CPU utilization far beyond normal HW transcoding and will bottleneck because of the single-core limitations.

I use the Shield TV Pro 2019.

There is a huge difference. The Shield Pro 2019 will DirectPlay everything from PMS.

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I tried switching off subtitles and let transcode 1080p hdr video and nothing changed. 60% cpu utilization and transcoding on the fly not possible, so no, switching off subtitles had no effect (basically it should not have an effect since many plex players can play the subtitles separately from video, so video is transcoded without subtitles anyway).

Btw i am not trying to achieve direct playing using my shield tv as a player (there of course is no issue), i just would like to use my Nas for hdr transcoding in case i or somebody would stream hdr video on non hdr device, which i thought this nas is capable of (based on the list of plex supported nas servers).

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@zluzar

Do you have any files without subtitles in them?

I am asking because, if you have subtitles in the file (or external), the transcoder will still be active . it does this in case you want to enable the subtitles mid-playback.

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Hi @ChuckPa , thanks for the idea regarding subtitles. But It is not root cause here. I tested this official hdr demo video LG Colors of Journey HDR UHD 4K Demo.mkv which has no subtitles and Plex simply wont transcode it. The same behavior like i described above - CPU utilization jumps to 60% and stays there, transcoding so slow that it is not even close to real time.

I just tested the same file using Synology Video station app and it could handle transcoding into fullHd output stream without any problem (CPU utilization less then 20%). So the issue lies in a way how hdr video is being transcoded in Plex (i want also to point out that even switching off hdr tone mapping does not help).

So question is, whether there is a way to force synology to use same codec or something as used by Video Station for Plex transcoding?

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@zluzar

While checking your problem, I found a problem of my own making.

What I uncovered is : I still had the residual hidden preference VaapiDriver="i965" in my Preferences.xml

The encoding of the file (L5.2) is too high for the i965.

Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.2@Main
Codec ID                                 : V_MPEGH/ISO/HEVC

This caused initialization of the i965 to fail. 5.2 exceeds the upper limit of what it can do. This is a known age/design limit of the i965.

My solution:

  1. Stop Plex
  2. Remove VaapiDriver="i965" from Preferences.xml
  3. Saved the file
  4. Restarted Plex
  5. Played the file again in Plex/web

Plex/web on my system will HW transcode

Screenshot from 2021-12-14 07-41-56
Screenshot from 2021-12-14 07-41-561025×980 43.8 KB

Investigating your problem helped me resolve a problem I was also seeing on some files.

I too am new to OLED. I have been ripping some of my discs again and upgrading to the 4K UHD stream native.

Removing the hold-over VaapiDriver setting immediately put everything as it should be.

Check your Preferences.xml

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@ChuckPa

Thanks for this advice, now we moved forward a little bit. After deleting this vaapiDriver my actual observations are:

HDR video without subtitles (e.g. LG Colors of Journey HDR UHD 4K Demo.mkv):

  • it now can transcode if i switch off Hdr tone mapping. Colors are very saturated, highlights are melted into white, but video is watchable, transcoded on the fly. However output defaults to SD output (cca 2mb/s) and it cannot be changed unlike yours 1080p. CPU utilization is good, under 20%.
  • if HDR tone mapping switched on, CPU stays at 60%, unable to transcode on the fly.

HDR video with subtitles:

  • still unable to transcode even 1080p x.265 main 10 video, regardles HDR mapping is switched on or off (cpu gets stuck at 60%).

So for me actual state is unsatisfactory. Basically, i could live with lower bitrate (SD) output without HDR mapping, it is not ideal, but acceptable. However almost all my videos have some kind of subtitles, it is quite common that videorips have subtitles already included, so being limited just to videos vithout subtitles is a dealbreaker (i guess even for native english crowd who will also have rips with subtitles in their collections).

Is there any chance that this issue regarding subtitles will change? To be honest i can´t understand why subtitles should limit video transcoding. Maybe i would get it a little bit if the subtitles were burned into the video, but why is it impacting transcoding in other cases? I think this is an issue plex team should focuse on, since really majority of todays mkv´s have some subtitles within the container. And being able to transcode only some hdr demo videos without subtitles is quite limited use case for being a Plex subscriber :slight_smile:

Or is there something else what can be done to overcome this issue?

Anyway thanks @ChuckPa a lot!

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There is no tonemapping on the native NAS packages yet.

(We keep asking but Engineering has not yet completed the task of making what is needed for everything)

I do have an alternative for you which works PERFECTLY

That solution overlays the Docker package (which is desktop Linux Plex in the container) on top of your Syno DSM 7-based metadata (PlexMediaServer shared folder)

This will give you the HDR tone mapping you desire and be controllable through the Synology Docker GUI.

Is this acceptable?

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That would be great @ChuckPa !

But as i wrote earlier, most import that the solution is capable of transcoding hdr videos with subtitles. This is much more important than HDR tone mapping since all of my hdr videos will contain some subtitles in whatever form (external or within mkv).

Btw i already have created Docker container based on the manual i found from you (so i can easily switch between package Plex or Docker Plex, both are using same metadata, which is great!). Unfortunatelly even this Dockerized Plex cant transcode hdr videos properly (with subtitles).

Anyway lets share your solution and lets see if it helps in my case! Thanks a lot for your effort! :slight_smile:

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Nothing on Synology can transcode AND BURN subtitles.

The CPU isn’t strong enough.

The HW transcoding is more than strong enough but the CPU is abysmal.

The trick here is curating the file.

  1. Player settings – They drive what happens (allow and limit)
  2. MP4 container (so there’s no remux)
  3. Make sure it only contains the streams you need (with proper default set)
  4. Only SRT subtitles. No PGS, VOBSUB, or DVDRIP (image based)
  5. Audio which you know the TV can play or PMS can convert (DirectStream) without touching the video.

It will take a bit of experimentation to find the sweet spot for your CPU

NOTE: The player subtitle choices for this are either : Automatic -OR- Only image formats. (it depends on what you have)

MKVToolnix (GUI) will make curation a breeze. It doesn’t do any encoding. It’s just a filter + repackage

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@ChuckPa i did some more testing with Dockerized Plex and it looks it is working properly! :slight_smile: It can also transcode my hdr movies which has subtitles, the only problem is with subtitles which cant be displayed independetly to video and need to be burned into video - in this specific use case it fails. Otherwise it is working just fine so far, even with HDR tone mapping switched ON.

So this Docker Plex version seems to be solution until proper Synology package version is downloadable from Plex.

Basically, it seems that all was related to this old VaapiDriver which was used in Preferences.xml - its simple deletion solved most of issues.

So i will play more with this Dockerized Plex version and if something else comes up i will share with you.

Thank you very much @ChuckPa for your help!!!

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That bit me too… Could not believe I still had it.

When I went looking, I was immediate :man_facepalming: LOL

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