pipewire: Add support for HDR streams

[flibitijibibo]

Feature request

PipeWire 1.6 and newer finally provides support for BT2020/ST2084 video capture/streaming.

There's already a draft to support this in kwin, for example:

https://invent.kde.org/plasma/kwin/-/merge_requests/8293

This should help pave the way for Steam Remote Play to add HDR streaming support for Linux hosts.

[flibitijibibo]

For testing purposes, upcoming builds of Sunshine will support this feature:

LizardByte/Sunshine@017ce49

Only issue is that Sunshine expects some method to get a PW node, while Remote Play just grabs the node directly... not sure what's harder, making a portal passthrough or adding gamescopegrab to their client backends.

[flibitijibibo]

Sunshine feature request for grabbing the gamescope PW node https://github.com/orgs/LizardByte/discussions/1007

[flibitijibibo]

A workaround for the XDG portal issue may be to use this third-party service:

https://github.com/Jovian-Experiments/xdg-desktop-portal-gamescope/tree/main

I have not yet tested this personally, but if it does actually work then this would be the last piece needed to get HDR streaming working with Sunshine.

[IceDBorn]

I managed true headless hdr, by patching gamescope to provide hdr metadata for the pipewire capture path and by utilizing a desktop portal for gamescope, made by Jovian-Experiments for SteamOS like experience under NixOS. Here's the commit and source.

@flibitijibibo Thanks for the portal idea. I've used jovian nixos for several years, I should have thought of it, a long time ago!

[flibitijibibo]

Good to know that it all works - for gamescope did you need to do anything besides adding the SPA_ enums for xBGR1010102 with ST2084 colorspace? I have that scribbled in locally but couldn't get the desktop portal to cooperate with my jank gamescope session, so I haven't been able to test a PR for upstream.

[IceDBorn]

@flibitijibibo I patch nixpkgs unstable's gamescope (3.16.24) with this file and with this postPatch substitute script. Also, the portal needs a patch to not crash on headless, also custom portal files.

[flibitijibibo]

The changes look pretty much like what I had, so I'd +1 a PR if you're comfortable submitting one.

My version, for historical purposes... notable is that your version properly checks for HDREnabled which mine didn't, and I spent an extra commit consolidating some of the format enumeration stuff:

gamescope-hdr.patch

[IceDBorn]

I'm not even sure if the changes are correct. It just looks ok on my TV, if more people tested this and confirmed it is working. I would love to investigate more into this and make a proper PR.

[flibitijibibo]

Quick update: There are a number of holes in the Sunshine path, some of which have solutions but not all:

• The gamescope compositor does not expose xdg_output information, just standard wl_output. This isn't a huge deal but for Sunshine it is, ticket is at wayland: monitor_t enumeration requires xdg_output LizardByte/Sunshine#5406 and a related issue is filed at 🧩 Feature Request: Implement wl_subcompositor in the internal Wayland compositor to enable Wine Wayland driver support #2194
• The gamescope xdg portal doesn't expose a stream size. This is fixed in @IceDBorn's local changes, which might be worth opening as a Draft PR even if it's not air-tight, so that maintainers are aware of the issue
• Even with --expose-wayland systemd services seem to have trouble picking up on WAYLAND_DISPLAY; for now I've been manually setting this in the script that launches gamescope via systemctl --user set-environment. This is less a question for gamescope and more for the SteamOS services and whoever's in charge of the contents of /usr/lib/steamos/, since eventually we may want to expose the display to stuff running in gamescope.

[IceDBorn]

I've made more patches to gamescope, to support vibrance/color temperature control both in sdr and hdr. Also, got SDR brightness slider and Enable HDR toggle to work. Right now, most color related features of steam integrated with gamescope are somewhat supported. Tldr, you can toggle HDR directly through the steam UI and moonlight will pickup the change.

[flibitijibibo]

Patch for xdg_output fallback: LizardByte/Sunshine#5411

Ticket for ScreenCast size property: Jovian-Experiments/xdg-desktop-portal-gamescope#1