Brightness/contrast not working in mpv

when i watch a video using mpv in Qubes os, and I use the number keys to change the brightness or contrast nothing happens. Is this broken in Qubes? I can do it in VLC using the menu.

The mpv manpage doesn’t list this caveat in the Keyboard Control section, but if you look up the --brightness and --contrast command line options they say “Not supported by all video output drivers”. Apparently that’s the case for both of the mpv video output drivers that are relevant in a Qubes OS context (the slow default --vo=sdl, and the fast --vo=x11).