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This is kinda a technology preview in order to see if we can ship features like this enabled by default in a lot more apps in the ecosystem.

Thus I'd be very super happy if you'll try it on lots of hardware - be Intel/AMD laptops or ARM64 devices (with V4L2 stateless decoders, such as most #LinuxMobile devices).

Chances that you really hit a zero-copy path are highest with a recent #Wayland compositor - i.e. if you are using #GNOME46, #kde6 or a recent version of #sway, #weston, #cosmic etc.

Note that there are still a number of limitations to offloading to KMS/display controllers. In these cases Livi should fall back just fine and will just be less efficient.
I hope we can lift them step by step. A few of them being:
- only hardware decoded video, not sw decoded
- only VA-API or V4L2-stateless, no V4L2-stateful or Vulkan yet (but at least the later should fall in place naturally)
- depending on the compositor and hw: only if the display dimensions match the video, e.g. 16:9

As well as only working when nothing is rendered on top of the video, like overlays, subtitles etc. Note that this limitation comes purely from HW/compositors - from the app side it is supported and works quite well on e.g. #weston, which already implements sophisticated hw plane management.

I guess I should have elaborated a bit more why and what for I'm asking for testing. So my main goal is to find remaining cases where the output looks like one of the attached images, which are complete deal breakers for users.

These are usually driver bugs - in Mesa or the kernel - and optimally should get reported accordingly. But if you see something like this are you are not sure where to report it - please feel free to DM me!

@rmader What "Live CD" distros with GNOME 46 etc. can be used for easy testing? I booted a nightly Fedora Workstation 40 from an USB stick but there's apparently a bug that makes it impossible to install Livi from Flathub because there's not enough space (https://discussion.fedoraproject.org/t/fedora-liveos-root-system-and-available-ram/82531) - any alternatives that should work out of the box?

@simran If I understand you correctly your question is which live-CD with Gnome 46 allows you to install a flatpak from flathub? Can't say for sure, but I guess if Fedora doesn't work you could try https://os.gnome.org/ or Ubuntu 24.04.

@rmader Yes, I'd like to test the video offloading on various devices (that have Windows or macOS installed) quickly, but installing Livi on a live Fedora looks like a major rabbit hole. I didn't find anything about running Gnome OS from a stick but I will try Ubuntu next. Thanks!

@simran Nice, looking forward to hear back about the results! Competing with or rather outperforming Win and MacOS is exactly the goal here :)

Note that there are further improvements in the pipe, notably lifting the restriction that the videos width/height ratio has to match the screen for zero-copy (https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/7057). I.e. testing devices with 16:10 screens or unusual video sizes is expected to not be optimal yet.

@rmader That's a good reminder, I need to check what the aspect ratios are of some of the devices and get matching test videos!

@rmader Live Ubuntu allows me to install Livi. Was able to run it after `sudo chmod u+s /usr/bin/bwrap`. Can't play AVC videos though under X11 (expected?). Commented out `WaylandEnable=false` in /etc/gdm3/custom.conf and ran `systemctl restart gdm3` - wayland is reported by `echo $XDG_SESSION_TYPE`. Livi does play the files but it's broken, 3x black and white. Terminal msgs might indicate use of iGPU instead of Nvidia card. Driver is nouveau, can't seem to install Nvidia drivers using live USB.

@simran Uff, interesting!
First of all: zero-copy playback is a #Wayland only feature - in fact it's one of the things that originally motivated its creation in the first place as it's not feasible on #X11 desktops.

Secondly: If your driver is blocklisted for Wayland, then I wouldn't expect anything to work, especially no advanced features.

That being said, it would be interesting if the issue you are seeing is actually even related to zero-copy playback - or if this is regular gl.

@rmader In my test, the Intel iGPU was apparently used (Clapper, MPV, and Glide show Video activity in intel_gpu_top), but with the display connected to the dGPU. With BIOS settings to use the dedicated Nvidia card only, Livi works okay but warns that it doesn't use HW accel and gives up as soon as it encounters a glitch in one of my test files whereas other players show artifacts but continue playback. I have yet to try iGPU-only with the cable plugged into the mainboard.

@rmader Under X11, Celluloid and QMPlay2 didn't show anything in intel_gpu_top. nvtop seems to require the proprietary drivers, unfortunately. Videos/Totem didn't play any of my test files (Intel iGPU and Nvidia dGPU), partially due to missing plugins (even after `sudo apt install ubuntu-restricted-extras`), but other times not even reporting an error and only showing a broken camera icon. Clapper crashes under Wayland, MPV Wayland as well with my own footage but not a Big Buck Bunny sample.

@simran Thank for that feedback - unfortunately I have to say that I don't think it makes sense to test much more on devices where things are so broken. It only makes sense on setups where the basics are in place - i.e. where most players can already properly play with hw decoding.

@rmader Yeah, the Intel driver seems kinda bad. GTK menus glitch out every now and then, for instance (not limited to Livi). With the BIOS set to the iGPU and one display connected to the mainboard, players behave differently, e.g. intel_gpu_top no longer reports Video activity for any of the apps that previously did. Now it's a lot of Render/3D. Livi rejected most files because of missing plugins suddenly. The green overlay disappeared in fullscreen mode with multiple players, though.