Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes)

[Ralf Jung <post@ralfj.de>]

Dear Uwe,

> On Tue, Dec 02, 2025 at 06:36:38PM +0100, Ralf Jung wrote:
> > > If you reliably can reproduce the issue then (although I realize that
> > > each testing step is time consuming), I would suggest to start a
> > > bisect.
> >
> > Unfortunately I cannot reproduce it alone, I need someone else to be in the
> > Zoom room. Also, I only have that webcam in the office, and I shouldn't
> > spend hours of my employer's time on bisects. ;)  I guess I could take it
> > home over a weekend or so, but I'd still need a way to reproduce the issue
> > alone, and find a weekend day where I have nothing else to do.
>
> I would try to wireshark the USB traffic. I guess that results in quite
> some amount of logs, but someone who is more familiar with USB and
> webcams might spot the relevant USB transfer that triggers the issue.

I think I managed to capture USB traffic from around the time when the webcam 
starts to show this issue:
- I joined the zoom room and activated the camera
- I started capturing
- Someone else joined the zoom
- The camera changed its "mode" and started flickering
- I stopped capturing

Then I filtered the result to only include the packets for the camera. I hope I 
did this correctly. I uploaded the result to:
<http://ralfj.de/upload/webcam.pcapng>

Kind regards,
Ralf

> And even if that doesn't help to immediately spot the problem it might
> help to reproduce the problem and thus make a bisection possible.
>
> Best regards
> Uwe

F