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One of the issues cropping up in the migration from Xorg to Wayland is the desire to capture part or all of your screen for recording and/or streaming to others - in many cases, applications designed for Xorg simply capture a black screen, with few workarounds.

However, for games and applications that can run with the Vulkan API, there's a new plugin from David Rosca (nowrep) for OBS Studio called obs-vkcapture (OBS Plugin Forum | GitHub) that aims to work around the issue and get your gameplay ingested directly, bypassing the built-in Xorg 'Window Capture'.

Bonus - it should even work under Xorg, provided you have a new build of OBS with EGL support and pass it the environment variable:OBS_USE_EGL=1

Similarly, you'll need to run your game (or other Vulkan application), one at a time (e.g. in your Steam launch options), with:OBS_VKCAPTURE=1

Now, this is a very new development (nowrep's initial commits here are barely 4 days old as of writing), but in my initial testing last night, I managed to play a 4 hour session of 7 Days to Die (using the experimental Vulkan backend), while streaming and recording it just fine.  That said, I did compile and install it by hand myself, on a git master build of OBS, and it is of course still under active development, so the usual caveat holds here: Your Mileage May Vary.

Still, they're looking at potentially adding OpenGL support in the future, so this is definitely one to watch.

Article taken from GamingOnLinux.com.
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Xpander 26 Mar
Quoting: BrisseCool! Ultimately we need PipeWire-support though. Personally I have always been able to capture xwayland surfaces but for some reason the frame-rate in the captured footage is terrible. When I switch to GNOME on x.org I can capture smooth 60fps footage.

Whats wrong with pipewire? you mean direct support? Cause it work fine for me with pipewire atm. If i want to capture specific game audio only i will use qjackctl and connect the needed inputs/outputs with OBS.
Shmerl 26 Mar
Quoting: KithopSo I think that's why EGL comes into play, here.

I don't think Wayland is tied to EGL? Wayland is a protocol, it's not really tied to a specific implementation. It can work with WSI.

QuoteThe Vulkan WSI (Window System Interface) is a set of API calls serve a similar purpose as EGL does for OpenGL ES or GLX for OpenGL. Vulkan WSI includes support for Wayland from day one: VK_USE_PLATFORM_WAYLAND_KHR. Vulkan clients can run on unmodified Wayland servers, including Weston, GENIVI LayerManager, Mutter / GNOME Shell, Enlightenment, and more. The WSI allows applications to discover the different GPUs on the system, and display the results of GPU rendering to a window system.

https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)

So that's why I was asking why they are using EGL instead of let's say WSI.


Last edited by Shmerl on 26 March 2021 at 6:25 pm UTC
Kithop 26 Mar
Quoting: Shmerl
Quoting: KithopSo I think that's why EGL comes into play, here.

I don't think Wayland is tied to EGL? Wayland is a protocol, it's not really tied to a specific implementation. It can work with WSI.

QuoteThe Vulkan WSI (Window System Interface) is a set of API calls serve a similar purpose as EGL does for OpenGL ES or GLX for OpenGL. Vulkan WSI includes support for Wayland from day one: VK_USE_PLATFORM_WAYLAND_KHR. Vulkan clients can run on unmodified Wayland servers, including Weston, GENIVI LayerManager, Mutter / GNOME Shell, Enlightenment, and more. The WSI allows applications to discover the different GPUs on the system, and display the results of GPU rendering to a window system.

https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)

So that's why I was asking why they are using EGL instead of let's say WSI.

I'm not a developer, so I can't say I've looked at it in any sort of depth, but my hunch is that Vulkan + WSI would be used in e.g. a game wanting to draw its Vulkan backend to Wayland, without using XWayland as a path (i.e. a Vulkan + Wayland native game), while EGL is being used for 'normal day-to-day applications', i.e. OBS, to render *its* window and preview to Wayland.

I'm guessing that OBS could totally be written to support WSI, but that means having OBS itself use Vulkan to render its UI directly, and I have a feeling it's abstracting that out through Qt for the most part, so this is a function of 'OBS supports EGL output but not necessarily Vulkan (yet)', separate from whether the game you're *inputting* is on Vulkan or not. But again, just a semi-educated guess here.
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