Sending multiple streams of the same type from one client

Hi, Is it possible to send many videos from one client, for example one from webcam and one (or hopefully many) from mp4 file or video tag?

Because at first it seemed impossible, but then I thought it should be possible. But for now I couldn’t achieve it. So my question is it possible or is it just my incompetence?

You can send as many audio and video tracks as you need.