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I have a Logitech C920 external webcam connected to my MacBook Air (13 inch, 2020) via a USB Type-C Hub.

I've been using it successfully to record videos using Photobooth until couple of days ago I upgraded the operating system to BigSur 11.1. Thereafter I started to experience following problem: In the middle of a recording, the blue indicator light on the webcam turns off and on again, and in the resulting video there are a couple of black frames.

I thought that maybe some device attached to the USB hub is getting too much power, so I removed all the devices (the mouse and the mobile router) from that hub so that the camera was the only one connected to the hub. This did not solve the problem.

I then downloaded and installed the Logitech settings app and currently I have following settings:

Settings of the camera in the settings app

Yesterday I turned off Auto focus and it seemed that it helped. However, today I again had those flashes.

I record videos that are between 6 and 15 minutes long. The problem gets worse towards the end of a video.

What can be the cause of this problem and how can I fix it?

Update 1: Here is a video where between 00:04 and 00:05 you can see how the blue indicator light of the camera turns off and on again.

Update 2: Today I tried to record a 10-minute video using the built-in camera and I had the same effect as with the external one.

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I'd first connect the camera directly, not via any hub. I have the same C920 & it can be sensitive to that. (Hmm, of course that may not be possible on USB-C… which would make eliminating the hub itself as a cause much tougher.)

Secondly, I would watch Activity Monitor whilst the recording is running, see if you can spot any jump in activity even on an unrelated process.

Thirdly, ensure as much as possible that any other user-controlled process isn't going to need resources at the same time. Video recording is resource-intensive, so try not to share the task with anything else that may be greedy.

Lastly, check you have lots of disk space so that you're not choking the process at write. As the issue increases with recording duration, this may be high on the list. Potentially video write & virtual memory may start to compete for the same space.

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