Streaming screen capture under Wayland

README.md

Recipes

kmsgrab capture with ffmpeg

sudo LIBVA_DRIVER_NAME=iHD ffmpeg -crtc_id 69  -framerate 60 -f kmsgrab -i - -vaapi_device /dev/dri/renderD128 -filter:v hwmap,scale_vaapi=w=1920:h=1200:format=nv12 -c:v h264_vaapi -profile:v constrained_baseline -level:v 3.1 -b:v 20000k test.mp4

LIBVA_DRIVER_NAME=iHD ffmpeg -device /dev/dri/card0 -f kmsgrab -i - -vf 'hwmap=derive_device=vaapi,scale_vaapi=w=1920:h=1080:format=nv12' -c:v h264_vaapi -vstats output.mp4

Allow kmsgrab capture as non-root user

Unsafe but needed

sudo setcap cap_sys_admin+ep $(which ffmpeg)

Src: https://ffmpeg.org/pipermail/ffmpeg-user/2018-June/040338.html

Wishlist

kms capture to OBS (is there a plugin somewhere?)

Resources

• https://www.ffmpeg.org/ffmpeg-devices.html#kmsgrab
• https://trac.ffmpeg.org/wiki/Hardware/VAAPI#DeviceSelection
• https://gist.github.com/Brainiarc7/24de2edef08866c304080504877239a3

OBS

• https://wiki.archlinux.org/index.php/Streaming_to_twitch.tv

Hi, have you seen these things?

• https://github.com/atomnuker/wlstream
• https://github.com/swaywm/wlroots/blob/master/protocol/wlr-export-dmabuf-unstable-v1.xml

The wlroots/sway folks plan to address "window|region capture" in the future as well. There are a number of Wayland compositors using wlroots and it seems increasing collaboration between the wlroots and KDE folks.

My hope has been that someone would adapt wlstream to be an obs plugin. It seems that wlstream has done the hard parts of getting an ffmpeg-compatible stream, without root, but I don't know enough about OBS APIs, C, ffmpeg, etc, to be able to figure out how to adapt the frames from wlroots to whatever OBS wants.

I think there's also some wondering if someone should build a wlroots<->pipewire bridge and then a Pipewire bridge for OBS, but I don't know the merits of the various approaches.

It would be cool if there was a repo or a rallying point for various Wayland/OBS folks to collaborate...

just saw your comment @colemickens

Yeah, I'm aware of wlr-export-dmabuf-unstable-v1 (https://obsproject.com/mantis/view.php?id=719#c3754). I was just wanting to get something working for actual streaming to an RTMP server.

I wonder: could ffmpeg be manually pointed to the right surface for capturing without root via the protocol, as wlstream does, or will it need patching?

I was never able to get dmabuf-capture working, so i guess that's step 0.

https://github.com/ammen99/wf-recorder might be of help :)

@MonAaraj the difference is wf-recorder receives the video frames via the wlr-screencopy wayland protocol, while this uses dmabufs to avoid copying, see ammen99/wf-recorder#45

https://hg.sr.ht/~scoopta/wlrobs supports wlr-export-dmabuf for zero-copy capture.

Ah, I see! Thank you very much! The reason I commented that was because I was looking for screen recorders other than OBS for Wayland and I found it difficult - I only found wf-recorder and it got the job done, so I thought I might put it here for people who get it from Google like me. Nevertheless, wlrobs seems interesting.