play-with-mpv python server problem
Got it working. Here's the full solution:

Plist: ~/Library/LaunchAgents/play.with.mpv.plist

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
    &lt;key&gt;Disabled&lt;/key&gt;
    &lt;false/&gt;
    &lt;key&gt;EnvironmentVariables&lt;/key&gt;
    &lt;dict&gt;
        &lt;key&gt;PATH&lt;/key&gt;
        &lt;string&gt;/Users/e/Library/Python/3.7/bin:/usr/local/bin&lt;/string&gt;
    &lt;/dict&gt;
    &lt;key&gt;KeepAlive&lt;/key&gt;
    &lt;true/&gt;
    &lt;key&gt;Label&lt;/key&gt;
    &lt;string&gt;play.with.mpv&lt;/string&gt;
    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
        &lt;string&gt;/usr/local/bin/python3&lt;/string&gt;
        &lt;string&gt;/Users/e/Library/Python/3.7/bin/play-with-mpv&lt;/string&gt;
    &lt;/array&gt;
    &lt;key&gt;RunAtLoad&lt;/key&gt;
    &lt;true/&gt;
    &lt;key&gt;StandardErrorPath&lt;/key&gt;
    &lt;string&gt;/tmp/play.with.mpv.stderr&lt;/string&gt;
    &lt;key&gt;StandardOutPath&lt;/key&gt;
    &lt;string&gt;/tmp/play.with.mpv.stdout&lt;/string&gt;
&lt;/dict&gt;
&lt;/plist&gt;


Mind the PATH to python3 - find it with which python3 and the play-with-mpv python script!

Load plist:

launchctl load ~/Library/LaunchAgents/play.with.mpv.plist


mpv config in ~/.config/mpv/mpv.conf

video-sync=display-resample


if this does not help, try this instead

opengl-early-flush=no


That video-sync parameter was the key - not a single dropped frame anymore.