#mix to file live PIP: melt A.mp4 -filter watermark:B.mp4 composite.geometry=10%,10%,20%,20% #live webcam stream PIP: melt A.mp4 -filter watermark:video4linux2:/dev/video0?width=320\&height=240\&frame_rate=15 composite.geometry=10%,10%,20%,20% #audio from both videos melt A.mp4 -filter watermark:B.avi composite.geometry=10%,10%,20%,20% -audio-track B.avi -transition mix