[MPlayer-users] -brightness and -contrast, how do they work?

[Anssi Saari]

How does one use the -brightness and -contrast options? I've tried xv, x11 and sdl output,
but I always get this:

Video attribute 'brightness' isn't supported by selected vo & vd! 
Video attribute 'contrast' isn't supported by selected vo & vd!

Is it for RGB formats only perhaps?

What I'm really hoping for is some way of setting XV_BRIGHTNESS and
XV_CONTRAST to a little higher values by default when using xv output,
since the output from my Radeon 7500 is a little dark.