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

Cross-posted to 2 groups.

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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

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Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2025-12-02 17:50 +0100
  Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-02 18:50 +0100
    Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-08 19:50 +0100
    Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-17 14:20 +0100
      Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2025-12-17 20:30 +0100
        Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-17 20:40 +0100
          Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2025-12-18 14:20 +0100
      Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-02 14:30 +0100
        Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Salvatore Bonaccorso <carnil@debian.org> - 2026-01-02 15:10 +0100
          Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-02 17:40 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-05 16:50 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Laurent Pinchart <laurent.pinchart@ideasonboard.com> - 2026-01-05 19:10 +0100
            Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-05 20:30 +0100
              Bug#1121718: linux-image-6.17.8+deb14-amd64: Logitech C920 HD Pro Webcam shows flickering artifacts (sometimes) Ralf Jung <post@ralfj.de> - 2026-01-20 15:30 +0100

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