But here i need to start not ffmpeg, but "start" Windows utility with parameters. jShell does not work if to put whole command line into the single string.
Why can't understand what exactly you want?
Sorry may be ... my poor English again..
...May be need to add quotes... also see the InitializeDoNotHandleQuotes...
...and another question... if you run manually the utility ...you want is it looping? Running forever?...
If not.. you can put it into a batch file that in the end will run itself.. calling bat again (simple)
But if the utility is ffmpeg has loop parameters...
Other way is to see or wait jshell to end (wait for) and loop it..
Hope helped you