Could use a defer after initing lastScreenshotURL, instead of duplicating the code 3 times, like so:

    defer {
      if !saveToFile {
        try? FileManager.default.removeItem(at: lastScreenshotURL)
      }
    }

I did not do that because I was worried that there was a reason the current code retains the file until all operations have completed. Since currently that happens asynchronously, deleting the file when exiting the method would create a race condition if there is a reason it must be retained until after it has been sent to the OSD.

How threading is handled between PlayerCore and MPVController is being refactored for the feature release. That will eliminate the "split processing" where some work occurs on the thread MPVController uses to read events and the main thread. This will simplify some of this code.