Files
IronCodeStudios 377547fa11 scrap/wayland: insert videoconvert to fix screencast on COSMIC / DMA-BUF portals (#15063)
On Wayland compositors whose xdg-desktop-portal backend exposes screencast
frames as DMA-BUF buffers — notably xdg-desktop-portal-cosmic 0.1.0 on
Pop!_OS 24.04 / COSMIC — inbound screen capture fails. PipeWireRecorder
links pipewiresrc directly to an appsink whose caps only accept
video/x-raw BGRx/RGBx in system memory. That format set is too narrow for
the portal's buffer-type / modifier negotiation, which collapses with:

  pw.link: negotiating -> error no more output formats (-22)
  gstpipewiresrc: stream error: no more output formats
  gstbasesrc: streaming stopped, reason not-negotiated (-4)
  ERROR src/server/wayland.rs: Failed scrap Element failed to change its state

Inserting a videoconvert element between pipewiresrc and appsink widens
the negotiable format set to any system-memory video/x-raw format, giving
the portal room to settle on a format it can deliver via its SHM path.
videoconvert then converts to the BGRx/RGBx the appsink expects.

Verified on Pop!_OS 24.04 / COSMIC with gst-launch, before and after:

  # fails (current behaviour):
  gst-launch-1.0 pipewiresrc path=N ! video/x-raw,format=BGRx ! fakesink
  # works (with this change):
  gst-launch-1.0 pipewiresrc path=N ! videoconvert ! video/x-raw,format=BGRx ! fakesink

After the change, inbound connections capture and stream the desktop
normally and the "Failed scrap" error no longer occurs.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-17 16:02:23 +08:00
..
2021-07-23 17:54:16 +08:00

About

Derived from https://github.com/H-M-H/Weylus/tree/master/src/capturable with the author's consent, https://github.com/rustdesk/rustdesk/issues/56#issuecomment-882727967

Dep

Works fine on Ubuntu 21.04 with pipewire 3 and xdg-desktop-portal 1.8

apt install -y libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev