When I launch media using the mouse or MIDI command, I receive feedback with approximately the following content:
/millumin/layer:layer/mediaStarted : (
"<OSCVal i 4>",
"<OSCVal s \"hybrid-office-blog.png\">"
and can use it (for example, to change the color of the Stream Deck buttons).
If I start media using the OSC command ( /layer:layer/startMedia/ ) I do not receive feedback