[onyx00]

I run Kodi on a Dell Chrombox 3010 that I have had for many years and has worked great. My audio receiver (Pioneer Elite SC-05) and TV (Samsung F8500) only support 1080p. Recently many videos I'm wanting to play at 2160 (4k). As I suspected, the Chromebox can't handle the conversion to 1080p and the 4k videos stutter terribly.

I looked at the hardware recommendation thread but didn't see any mention of this.  Is there hardware that would support 4k -> 1080p on the fly for Kodi? Being able to bitstream digital audio is also a must for me (DD, Atmos, etc.).  Thanks in advance!

[Klojum]

As I suspected, the Chromebox can't handle the conversion to 1080p and the 4k videos stutter terribly.

It's not so much the conversion to fullhd, but the decoding of the HEVC video format which really requires dedicated hardware acceleration on the video chip. And right now the CPU of your Chromebox is doing all that hard work, and it's simply not up to the task.

Any hardware that can do the decoding of 4K can also display it at any lower resolution. I have had a 7-yr old Celeron 1037 which can render 4K video (h264 but still) just fine, and it displays the video perfectly.

[onyx00]

As I suspected, the Chromebox can't handle the conversion to 1080p and the 4k videos stutter terribly.

It's not so much the conversion to fullhd, but the decoding of the HEVC video format which really requires dedicated hardware acceleration on the video chip. And right now the CPU of your Chromebox is doing all that hard work, and it's simply not up to the task.

Any hardware that can do the decoding of 4K can also display it at any lower resolution. I have had a 7-yr old Celeron 1037 which can render 4K video (h264 but still) just fine, and it displays the video perfectly.

Got it, so basically if I get a new Chromebox I should be fine then?  Asus is coming out with their Chromebox 4 which comes with a 10th gen Intel processor (Celeron, i3, i5, i7) so thenI am guessing I would be fine if I follow what you are saying.

[noggin]

Just adding a caveat that if the 1080p results needs to be Rec 709 SDR (aka 'regular HD) and the h.265/HEVC sources are from UHD Blu-rays (and thus likely to be Rec 2020 HDR10 - i.e. HDR with a wide colour gamut) then you also have to take tone mapping into account (i.e. conversion between Rec 2020 HDR and Rec 709 SDR).  

Tonemapping HDR Rec 2020 to SDR Rec 709 is not an exact science, and is implemented differently on different platforms I believe.

If you playback HDR Rec 2020 2160p h.265/HEVC content and don't tonemap it to Rec 709 SDR and leave it untreated you will get very flat, washed out pictures with grey blacks, desaturated colours etc.

[jubilex]

The tonemapping is the big issue. So far Kodi only has good tonemapping (Hable and ACES Filmic) for D3D and OpenGL, and this doesn't include ARM devices like Odroid and Firestick etc, which would need these to be implemented in OpenGLES.

Without the good tonemapping, most 4k content, which tends to usually be HDR as well, will be very flat looking with un-saturated colors.

[fritsch]

Those named arm devices rely on mediacodec surface to be able to decode and especially output 4k content.

They are far too slow for doing proper tone mapping on the 3D GPU. While on windows and OpenGL world most of the time the GPU and the ipu are the same, this is exactly not the case on arm and getting decoded data back into the 3D GPU needs a full dma copy import.

[jubilex]

Those named arm devices rely on mediacodec surface to be able to decode and especially output 4k content.

They are far too slow for doing proper tone mapping on the 3D GPU. While on windows and OpenGL world most of the time the GPU and the ipu are the same, this is exactly not the case on arm and getting decoded data back into the 3D GPU needs a full dma copy import.

Ah, thank you, that's a bummer. I had thought since running the new algorithms on Windows showed no appreciable increase in CPU or GPU usage, that it wasn't too intensive. 

So I guess full PCs are still the only option if one wants to collect HDR content but still only has SDR displays to view it on.