Emulating real Android device Camera output

I have a real (physical) Android device connected to my PC via USB cable. App under test has a QR scanning step, and I would like to hijack the camera output and feed a static image to it. That way the QR scanning procedure can be automated. It is possible to communicate with the device by Android Debug Bridge.

I am aware of all the solutions regarding VIRTUAL android device, but how can this be achieved with a physical device? Preferably with CLI and ADB.

Thanks!