I'm building a PyQt application where one widget is displaying a webcam video feed. For the widget I basically use a lightly altered code from the QCamera example from geeksforgeeks.com.

The (minimal version of the) code I'm using:

class Camera(QCameraViewfinder):
    def __init__(self, parent=None):
        super(Camera, self).__init__(parent)
        self.available_cameras = QCameraInfo.availableCameras()
        
    def select_camera(self, i):
        self.camera = QCamera(self.available_cameras[i])  
        self.camera.setViewfinder(self)
        self.camera.start() 

This works fine one my machine A (Arch on a notebook) but no available Cameras are detected one my machine B (freshly installed Debian on a Lenovo Thinkcentre). self.available_cameras is empty. I use the same webcam (and have tried two different ones), they show up in dmesg as a USB HD Camera and I can access the camera feed via VLC, guvcview, etc...

I would appreciate any help and pointers to what the problem is. It would be also insightful where PyQt gets its list of cameras from. thx!

UPDATE: I was able to fix the problem, ekhumoro pointed me in the right direction. There were some qt packages missing, I (re)installed all of them by running:

apt install qtmultimedia5-*

The result was a error of a missing gstreamer library, so I installed gstreamer:

apt install gstreamer1.0-plugins-*

Now the camera is discovered and the feed is displayed, however it lags a lot. But this is now a different problem.