Is there a program or way to watermark videos?

Question

Video

In general, the task is to have a video, I sell it, and I need to put personal "watermarks" on it (preferably quickly).
In different places and with different delays, an inscription will appear, similar to a serial key for a split second.
It seems like the closest thing to solving this problem is Virtualdub with the logo filter.

Answer 1

or ffmpeg with its overlay filter
. For example, overlay video.mp4 with the logo from image logo.png for the first 30 seconds:

ffmpeg -i video.mp4 -i logo.png -filter_complex \
  "[0:v][1:v]overlay=10:10:enable=between(t\,0\,30)" -codec:a copy out.mp4