4K resolution not working
You can make recordings in 4K quality with a 4K webcam, such as the Logitech BRIO. For this to work, you need a USB 3.0 port (or faster) on your computer; otherwise, for example, the Logitech BRIO on a Raspberry Pi will only transmit a maximum resolution of Full HD (1920 x 1080). USB 3.0 ports are usually identifiable by their blue interior.
The Raspberry Pi 4 is the first model in this series with a USB 3.0 port. Models released before the Raspberry Pi 4 do not support 4K transmission due to hardware limitations.
In our Raspberry Pi image, you can select the desired resolution in the Printer Settings under the Webcam section at the bottom. To avoid overburdening the hardware, we recommend significantly lowering the frame rate at high resolutions and not going for 25 or 30 FPS, but rather 5 FPS or less.
No image after restart
With some cameras, it may happen that no image is received after a restart of the computer or the MJPG-Streamer. In this case, unplug the webcam’s USB connector and then plug it back in.