Regression: Falkon doesn't detect webcam anymore since 5.15.3+dfsg-3ubuntu1

[Jan Rathmann]

Since the update of qtwebengine-opensource-src to 5.15.3+dfsg-3ubuntu1 my webcam is not detected anymore in Falkon.

With 5.15.2+dfsg-3ubuntu1 this was working fine.

Updating to 5.15.3+dfsg-5 didn't help.

My cam is an older model:

$lsusb
Bus 001 Device 004: ID 046d:0928 Logitech, Inc. QuickCam Express

Note that it seems to be necessary for this webcam to be working to start the application that should use the cam with an LD_PRELOAD of v4l1compat.so, e.g.:
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libv4l/v4l1compat.so falkon

But I'm not sure if this is related to this bug.

I have attached the terminal output from starting Falkon and trying to access the webcam (by opening a random room at meet.jit.si)

Kind regards,
Jan

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: libqt5webengine5 5.15.3+dfsg-5
ProcVersionSignature: Ubuntu 5.11.0-13.14-generic 5.11.7
Uname: Linux 5.11.0-13-generic x86_64
ApportVersion: 2.20.11-0ubuntu62
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: KDE
Date: Mon Apr 12 12:03:54 2021
InstallationDate: Installed on 2021-04-05 (6 days ago)
InstallationMedia: Kubuntu 21.04 "Hirsute Hippo" - Beta amd64 (20210405)
SourcePackage: qtwebengine-opensource-src
UpgradeStatus: No upgrade log present (probably fresh install)

[Dmitry Shachnev (mitya57)]

Sorry for the inconvenience this caused. We landed 5.15.3 quite late in the cycle, mostly because of the security fixes it brings.

Can you please clarify: with LD_PRELOAD it works now with 5.15.3, or LD_PRELOAD was needed previously with 5.15.2 and now it does not help?

Also maybe you can check if the cam works in the latest Google Chrome or Chromium?

[Jan Rathmann (kaiserclaudius)]

LD_PRELOAD was always necessary to make the cam work.
Yes, with 5.15.2 it worked (only) with LD_PRELOAD, with 5.15.3 even LD_PRELOAD doesn't help anymore (so currently I don't know any way how to make the cam be detected by Falkon).

Did a test with latest Google Chrome, seems to be the same as with Falkon (cam is not detected even when using LD_PRELOAD). I never used Google Chrome, so I unfortunately can't tell if it used to work on older Chrome versions.

With Chromium I can't test because it's only avaiable as a Snap or Flatpak where the LD_PRELOAD trick doesn't seem to be possible ( --> no way to use the cam in a snapped or flatpaked app).

On Firefox the cam still works when launching with LD_PRELOAD.

[Dmitry Shachnev (mitya57)]

I have forwarded your bug upstream to https://bugreports.qt.io/browse/QTBUG-92597. Let's see what the upstream developers say about it.

If you want, you can register on that site and follow it, maybe they will want some more information from you.

For me the webcam works fine with 5.15.3 and Falkon (I tested on https://webrtc.github.io/samples/src/content/devices/input-output/), so maybe it's an issue specific to v4l1compat.so or something else.

[Jan Rathmann (kaiserclaudius)]

Dmitry, thanks for forwarding, I've subscribed to the upstream report.