Hi,
I mean black borders from “Add black borders on fullscreen” option.
I updated mpv to v0.27 and fullscreen video now looks like this https://i.imgur.com/4OWuoBi.png.
It doesn't matter which video output driver I select. Opengl, xv, vdpau makes green borders on fullscreen.
UPD:
mpv log adds following lines when SMPlayer switches to fullscreen mode:
Opening video filter: [expand aspect=1.25]
[expand] This filter is deprecated. Use lavfi pad instead.