1904615 - [pipewire] bad handling of pw_buffer with only cursor metadata

Status: RESOLVED DUPLICATE of bug 1896575

(Core :: WebRTC: Audio/Video, defect)

Description

[Martin Bednar]

This is a follow up from KDE bug: https://bugs.kde.org/show_bug.cgi?id=487300
When screencasting with firefox, and there is only cursor movement (window in question is minimized) , firefox displays garbled images.
kwin 6.1.0, wayland, radeonsi driver.
Do note that this might no longer be easily reproducible once https://bugs.kde.org/show_bug.cgi?id=487294 is fixed.

steps:
1 minimize a window
2 share only window to firefox
3 move cursor over original place of window

comment from kwin developer:
"I believe it's either a webrtc or a firefox bug. It looks like it doesn't handle well pw_buffer's that contain only cursor metadata. Things work fine in obs and chromium."

Comment 1

[Andreas Pehrson [:pehrsons]]

Jan, would you mind taking a look?

S2 because the screenshot in the KDE bug indicates we're reading bad memory.
Sec-bug because we could be leaking unrelated memory to content this way.

Comment 2

[Jan Grulich]

Sure, I will look into this once I'm back from vacation (on Thursday). I'm surprised it works in Chromium since the code for screen sharing should be identical. Unless https://bugzilla.mozilla.org/show_bug.cgi?id=1896575 fixes it, because it was backported to M126 in Chromium and therefore released recently, while in Firefox it's only in FF 128 and thus not released yet.

Comment 3

[Andreas Pehrson [:pehrsons]]

Sounds relevant! Martin, could you test in >= 128, i.e beta/nightly?

Comment 4

[Martin Bednar]

Attachment: ff 127 vs 128b7

Just tried side by side ff 127 / 128b7, and indeed in 128b7 it doesn't happen, and the cursor moves correctly.

Comment 5

[Andreas Pehrson [:pehrsons]]

Great, thanks for confirming.