Videos only shown in their own window

[dacq]

I installed smplayer 18.10 rev9144 from the debian 10.2 repository. When I view a video it's shown in its own window, not the main window. How do I show it in the main window?

[rvm]

Try a different video output (preferences -> general -> video).

[dacq]

It didn't work. I wasn't surprised.

[rvm]

Be sure the option to run mplayer in its own window, in preferences -> advanced -> mplayer is not enabled.

[dacq]

Major problem: the “run mplayer in its own window” box is NOT ticked.