I got the same thing. Looking at the MPV website/change log it would appear that the command "osd" has been deprecated. As a workaround you can add: --osd-level=x
in SMPlayer -> Preferences -> Advanced -> MPlayer/mpv -> Options.
--osd-level=<0-3>
Specifies which mode the OSD should start in.
0: OSD completely disabled (subtitles only)
1: enabled (shows up only on user interaction)
2: enabled + current time visible by default
3: enabled + --osd-status-msg (current time and status by default)
Works for me.
