Can't get HW transcoding with HDR tone mapping to work (iGPU Gemini Lake)

Plex Media Server Desktops & Laptops
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Server Version#: 1.41.5.9522
CPU: Intel® Celeron(R) J4125
GPU: Intel® UHD Graphics 600 (GLK 2) Gemini Lake
System: Ubuntu 22.04.5 LTS
plexinstaller.log (806 Bytes)

Information from console when transcoding fails:

[Req#14b7/Transcode/54v476g704k207mnvm70ji0t/cf8ae7c7-70c8-4a69-8979-78a90629c24a] [AVHWDeviceContext @ 0x77cc58dbfdc0] No matching devices found.
[Req#14d1/Transcode/54v476g704k207mnvm70ji0t/cf8ae7c7-70c8-4a69-8979-78a90629c24a] [Parsed_tonemap_opencl_3 @ 0x77cc59d18a40] Failed to finish command queue: -5.
[Req#14d4/Transcode/54v476g704k207mnvm70ji0t/cf8ae7c7-70c8-4a69-8979-78a90629c24a] Error while filtering: I/O error
[Req#14d8/Transcode/54v476g704k207mnvm70ji0t/cf8ae7c7-70c8-4a69-8979-78a90629c24a] Failed to inject frame into filter network: I/O error
[Req#14db/Transcode/54v476g704k207mnvm70ji0t/cf8ae7c7-70c8-4a69-8979-78a90629c24a] Error while processing the decoded data for stream #0:0

Hello,
According to this, this iGPU should support HDR to SDR tone mapping under Linux, yet I cant get this to work.
I have tried Ubuntu 24.04; 24.10; 22.04. Have tried different drivers, tried to get transcoding to work via ffmpeg commands. Messed with permissions,
If I disable HDR tone mapping, hw transcoding starts working correctly.
Could someone please confirm that this iGPU cannot hw transcode together with HDR tone mapping?

2

Gemini Lake CPUs have a bad implementation problem with OpenCL (how tonemapping is done)

Is this a brand new machine?

I ask because, if possible, I strongly recommend a different mini PC platform.

I have a GeminiLake here for testing.

I also have a Beelink Mini PC, Mini S12 Pro Intel 12th N100 for testing.
I find it profoundly faster and better at all transcoding tasks.

The GPU in the BeeLink is an AlderLake GPU

3

Thank you for your answer. No, this machine is at least few years old, but this is first time I try to run Plex server on it.
Is tone mapping working on your GeminiLake?
So to sum up, I should just give up getting this thing to work and get newer mini PC platform?

4

We have been fighting with GeminiLake CPUs since they were released.

The best we can figure out is Intel Media Driver and the actual hardware are not communicating correctly.

For some machines, but NOT all, there is a hack you can try.

I’ve not tried it in a while because it’s dependent on the host OS runtime libraries (not PMS). It’s dependent on libva.

That hack is:

  1. Stop Plex
  2. Edit Preferences.xml
  3. Before the closing />, add
  4. VaapiDriver="i965" (space before and after)
  5. Save the file

This works for some of the older CPUs because those CPUs (pre -10xxx) still have an i965 interface ASIC to get to the QSV ASIC in the CPU.

For those which don’t work, the failure to work is due to the motherboard / bios actually blocking it.

That aside, YES, I would update to a newer box.
I have a huge library here (110TB DIY RAID box I built) and that AlderLake CPU can play everything with ease

The only real limitations you’ll run into are:

  1. Number of simultaneous audio transcodes (e.g. 7.1 → Stereo downmix)
  2. Total video bits/sec being transcoded (the bus can handle only so much). 600 Mbps is a safe bet on this CPU
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I tried this hack, unfortunately it did not work.
I’m now on AlderLake and everything seems to work fine. Thanks for help.

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Don’t forget to remove the “VaapiDriver” preference on the AlderLake.

In the line of succession, I find the KabyLake (-7xxx) and its refresh (-8xxx) followed by the AlderLake (-12xxx) to be the most stable of them all.

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