Overlaying two other video files on to another is very easy with ffmpeg. I had two video files that are 640×360 pixels, and one that is 1920×1080. I used this command line with ffmpeg to overlay them.
ffmpeg -i controller_agroprom.mp4 -vf "movie=dbz120.mp4 [a]; movie=dbz121.mp4 [b]; [in][a] overlay=0:32 [c]; [c][b] overlay=0:448" out99.mp4 |
The two smaller video files are dbz120.mp4 and dbz121.mp4. These are arranged on top of the main video file and then are baked together as one file.
The above screenshot shows the result of this command, this type of trick could be very useful to overlay a video of someone talking on to another video without needing an expensive video editing program.