How to merge two video files into one, in automatic mode?

Question

Video

There are two synchronous video files (let's say a video of one person from two angles).
It is necessary to automatically reduce these two videos into one, according to the "picture in picture" principle, let's say that there is one video with a screen split in half.
Thanks for the valuable tips.

Answer 1

Here with examples: www.daniel-mitchell.com/blog/video-in-a-video-ffmpeg .