Character Animator doesn't currently support non-webcam video capture devices for camera input.
That said, if the device drivers for your video capture device support webcam output then it can sometimes work.
If you are on Windows:
One test for compatability is to use the built-in Windows "Camera" app. (Go to the Windows Search bar and enter "Camera" and click on the app to launch it.) If your camera shows up in the Windows Camera app then it should be compatible with Character Animator.
If you are on Mac this is usually less of an issue. MacOS generally does a better job handling video capture devices as cameras.