MPV HDR support on Linux

[laichiaheng]

I saw a line in ArchWiki: https://wiki.archlinux.org/title/HDR_video_playback#mpv
HDR support is native and all the configurations are set to correct values by default. You can adjust the peak brightness using --target-peak.

1. Does that mean MPV player can show HDR effect on a HDR capable TV in SDR mode now?
2. According to that article, does it mean we can watch HDR content natively on Linux Xorg now?
3. How can Gnome and KDE be so poor at supporting HDR color profile in Wayland?
4. MPV still can have HDR color profile support even GDM and SDDM don't support it, does it correct? How about the 10bit color?
5. According to the MPV manual, target-peak should not be used to SDR content, so we need to change the config every time we watch videos?

[lavilao]

I was going to say the typical "linux does not have hdr support" answer but after reading the page it seems to imply that there IS experimental support for hdr on linux, ironically I always though it was going to be a wayland exclusive thing but is only on x11 for now.

[laichiaheng]

@lavilao Does it mean that MPV can passthrough HDR videos by adding '--vo=gpu-next' on X11?

[LaserEyess]

• Does that mean MPV player can show HDR effect on a HDR capable TV in SDR mode now?

No

• According to that article, does it mean we can watch HDR content natively on Linux Xorg now?

No

• How can Gnome and KDE be so poor at supporting HDR color profile in Wayland?

It needs standardization via a protocol. They are Working On It™

• MPV still can have HDR color profile support even GDM and SDDM don't support it, does it correct? How about the 10bit color?

ICC support is completely separate from HDR, also a login manager has nothing to do with it so I don't understand the question. mpv can do 10bit already, it's up to the display and your DE to support it.

• According to the MPV manual, target-peak should not be used to SDR content, so we need to change the config every time we watch videos?

Target peak is only relevant if an HDR is detected and tonemapping is active.

There's a lot of misinformation here about what "Linux" supports and does not support, so I'll try to break it down:

• The Linux kernel and most DRM drivers (intel, amd) have support for passing HDR metadata to a display, this is a kernel feature, it has nothing to do with userspace. In other words: just because the kernel can do it doesn't mean wayland or Xorg can
• In order for a userspace program like mpv to pass HDR metadata to the kernel and then ultimately to the display, there must be a userspace API for doing thatt. This API does not exist for Xorg or Wayland, but there is an API for drm directly
• mpv has a PR for supporting the DRM API only (--vo=gpu{,-next} --gpu-context=drm) at drm: add --drm-send-hdr-meta option to send HDR metadata #8648, but this will not work for Wayland or Xorg, see also: Add HDR passthrough support to gpu-context=drm #8219
• None of this has anything to do with actually playing HDR files, that will work just fine and it will tonemap the HDR to SDR

So, if you want to do HDR passthrough that is currently not possible in mpv. There could be support for --gpu-context=drm but it's not finished yet. It is completely out of mpv's control for Xorg and Wayland. I would not hold your breath on either, but there is active Wayland work being done at the very least.

[LaserEyess]

That entire arch wiki article is completely wrong, you can tell in the first paragraph it is just making shit up:

Red Hat has hired people to work on improving HDR and developers at X.org are also working on improving HDR on Linux. See the roadmap.

That link says absolutely nothing that bullet point says at all. It is about Wayland, not Xorg, and no one there even works for redhat.

[laichiaheng]

@LaserEyess But it still can look like HDR with target-peak if TV brightness is high enough in SDR mode, although it has been transferred to SDR, right?

[LaserEyess]

--target-peak controls tonemapping, which in this case would be HDR->SDR, but the TV brightness really doesn't affect anything. It's not HDR, it's SDR.

[laichiaheng]

@LaserEyess Should we change the target-peak if TV brightness is over 203nits? In the manual, it says that it leads to very unexpected results for SDR content.
I'm confused now, I thought that we would see similar HDR effect on SDR mode if TV brightness were high enough.

[LaserEyess]

You're confusing a few different things here. There is no "HDR Effect" here, you are playing back content as tonemapped HDR->SDR. What happens when you set --target-peak is that you are telling mpv to ignore whatever display capabilities are present and just assume that a peak is a certain amount of nits. See also: https://mpv.io/manual/master/#options-target-peak

And, as an aside, I also should have RTFM, setting --target-peak on SDR displays may do bad things, but the default, auto, should be fine. This is pretty much the limit of my knowledge of HDR so maybe someone else can chime in. Bottomline is: just play the video on your monitor, it will work and tonemapping will make it look as good as possible.

[lavilao]

sorry @laichiaheng acording to @LaserEyess the arch wiki article is wrong (wich makes sense otherwise reddit would be full of "linux supports hdr now" posts) so no hdr on linux for now. I guess we are all humans, even archlinux users that write on the wiki can make mistakes xD

[Doofussy2]

--target-peak controls tonemapping, which in this case would be HDR->SDR, but the TV brightness really doesn't affect anything. It's not HDR, it's SDR.

That's a little ambiguous. If an HDR video is mastered at 1000 nits and you specify target-peak=1001, there shouldn't be any peak adjustments by the player, and as long as the color gamut isn't changed, tone-mapping shouldn't happen. And if there is, that would be bad. The video should be passed to the swapchain (provided it supports the media).

[Traneptora]

It appears this question is answered. If tonemapping is broken then please open a separate issue for that.

[laichiaheng]

@LaserEyess Hi, I have another question. Am I able to play HDR videos in SDR mode with high peak brightness and high contrast instead of low contrast flat image?