splitting 2videos on the CLI with ffmpeg.

ffmpeg-splitter.sh

ffmpeg -i video1.mp4 -i video2.mp4 \
 -filter_complex \
    "[0:v]pad=iw*2:ih[int]; \
     [int][1:v]overlay=W/2:0[vid]" \
-map "[vid]" \
-c:v libx264 -crf 23 \
  video3.mp4

further reading:

• https://superuser.com/questions/153160/join-videos-with-split-screen
• https://www.ffmpeg.org/documentation.html