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.
![Video files overlayed with ffmpeg video editor.](https://www.securitronlinux.com/wp-content/uploads/2019/07/vids-960x516.png)
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.