What technologies better use for a desktop application that plays video?

See more:

cross-platform

multimedia

GUI

Let's say it is necessary to build desktop application that should have a part of it's window filled with a video, with video controls. Like in a video editor.
What language, GUI library would you recommend for such purpose?
It shouldn't be tied to certain OS and with no license frees (like Qt).
I'm looking for the easiest way to go (less lines of code, ease of maintenance...).
Of course Java first comes to mind, but would it be the best choice?

What I have tried:

Thought to use Python, but there are often problems while installing libraries, even using venv.