A different video/audio input

I am developing a project in which you need to use a different video / audio input than the one that comes from default (webcam, microphone, etc). Could a file be set as a video / audio input? This file could be a video file for example.
I am using jitsi-meet and lib-jitsi-meet for the project.

Actually, what I need is to set an IP camera as a video source, and the audio from that camera as a microphone. Can anybody help me?