Tonemapping HDR content to SDR on RPI4

Murdock8741 · January 1, 2022 at 11:37 PM

Hi everyone, happy new year !

I have a question, I'm watching 4K content, which use HDR colors, on a TV without HDR support and colors appears "wash out". I was using an old version of Librelec (with Kodi Leia 18.9), so I have upgraded to last release of Librelec (10.0.1) but problems still appear...

I found out via Kodi github repository that a pull request was merged for Nexus v20 with better tonemapping support : https://github.com/xbmc/xbmc/pull/20157.

So I'm currently using nightly build "LibreELEC-RPi4.arm-11.0-nightly-20211231-9a279e4.img.gz" but I don't see differences with previous versions.

Do I need to configure something specific for better HDR->SDR convertion ?

Or maybe, that pull request is not appliable for RPI4 ?

Thank you for your response.

Have a nice day !

**chewitt** · January 2, 2022 at 10:16 PM

HDR to SDR tonemapping is not currently implemented, so nothing to enable. It's something in the to-do list for the future.

**HiassofT** · January 2, 2022 at 10:44 PM

Don't hold your breath on that - RPi4 doesn't have a dedicated hardware block to do tonemapping and the GPU is rather slow so it's unlikely it would work for anything above 720p.

If you have (4k) HDR files but not a HDR capable TV the best solution is to use Handbrake on your PC to recode those files to SDR on your PC.

so long,

Hias

Murdock8741 · January 3, 2022 at 9:06 AM

Thank you for respond to my post, I was thinking it was already on with this pull request. I'm gonna followed this, thank you guys for all your hard work !

HiassofT , I don't want t re-encode all my files, one day I'm gonna have a "good" tv

I understand that RPI4 can be limited on this feature but do we have another solution (except buying an android box, I really enjoy LibreELEC), maybe an external device which can be plug on the RPI ?

Murdock8741 · January 23, 2022 at 4:43 PM

Sorry for re-opening this post, but I'm still "blocked" with this HDR->SDR conversion.

Do you have an hardware to recommend that actually support this feature ? Allwiner, rockchip, amlogic, does any of those board have the required specs ? I'm searching to replace my RPI4 in order to solve this issue.

Thank you for your time,

Murdock

**chewitt** · January 24, 2022 at 2:38 AM

Things that use the Amlogic vendor kernel (and suitably hacked versions of Kodi) support HDR > SDR tonemapping - on Linux or on Android using devices. Otherwise you are waiting for Kodi to support it, and drivers to be written for other ARM hardware that has hardware modules that can do it. Or you need to re-rip original media without HDR (which would have made sense since you don't have an HDR capable TV) .. or use a TV that supports HDR.

Murdock8741 · January 24, 2022 at 8:29 AM

Thank you chewitt for taking time to respond.

I know, buying new TV with HDR support will solved my issues, this is on schedule but for the end of the year :p

I understand the issue, I was not sure if this feature wasn't supported at all on LibreElec, or if that was available for some board. I'm gonna look for temporary solution in the meantime.

Thank you all for your work !

EDIT : this post is solved for me, I have informations that I was looking for but can't find button to mark this as "resolved"

Tonemapping HDR content to SDR on RPI4

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