Quarter-Size Video on MacOS

Dear MPlayer Experts,

I'm trying out MPlayer 1.5 installed on MacOS 10.15.7 by Home Brew. When I play a video, any video, with MPlayer 1.5, a window opens up on my laptop's display (2560 x 1600 Retina) with the video playing in the bottom-left quadrant, and the remaining quadrants are black. I have a second display connected to my laptop, one of lower resolution (1920 x 1080). I drag the window over to this second display and the video expands to fill the entire window. I move the window back to the laptop display and the video continues to fill the entire window. When I do the same with MPlayer 1.4, the video always fills the window.

Is there a command line option I can use to tell Mplayer the display resolution so the video will be displayed correctly first time?

Best Wishes, Kevan

-- 
Kevan Hashemi, President
Open Source Instruments Inc.
www.opensourceinstruments.com