No root access and no custom ROM need even on Android 4.4/5.0 devices. Only you need is just install(and of course you need UVC web cam and OTG cable).
There are some devices that fail to start preview with specific combination of camera and resolutions. Please stop and restart preview again with ON/OFF button.
You can start/stop movie capturing by pressing capturing button placed at bottom center of screen(while you set a switch placed at right bottom of screen to the right position).
You can also save still image as a png file into DCIM/UsbWebCamera directory on the external strage by pressing the capturing button(while you set a switch placed at the right bottom of screen to the left position).
You can start interval capturing by long pressing the caputuring button.
UsbWebCameraPro v2.8.1 Android