I added the Jack audio kit to "autostarted applications" (the specific command I entered is 'jackd --realtime -d alsa') and marked it to be autostarted, but when I login to xfce it isn't started. That is, when I start and application that's supposed to work with it, like Amarok, it gives out a message that Jack... is not found and a quick 'pstree' or similar command will show indeed that there's no jackd process open.
Does it run properly if you run the same command from a terminal after Xfce starts up? The --realtime switch seems questionable to me. Unless jackd is setuid root, that will likely fail (assuming it does what I think it does), as regular users are not allowed to set realtime process priority.
Yes, it runs properly if I start it manually. That's what I usually do - open xfrun with alt+F2 and type exactly the same command. And maybe the realtime switch is really questionable, but it shouldn't stop it from working at all. It doesn't when I start it with xfrun anyway.
OK, it's a bit off-topic but you brought it up so I checked it: a normal user can start jackd with realtime priorities as long as PAM is configured to allow it. Check out http://jackaudio.org/faq
I was only asking about the --realtime bit because you gave no indication of whether or not the software worked at all normally. Just trying to gather information you left out. I really have no idea why this doesn't work. There's no reason it shouldn't. Do you have other apps in autostart that don't start up properly? Does jackd have any command-line options to enable verbose/debugging output? Try enabling them and check for console output.
I ran 'jackd --verbose...[other options as usual]'. Everything seems normal. I don't know about other autostarted apps, as I disabled all the rest. It used to autostart pulseaudio and thunar (as daemon) without any problems (until I unmarked them). Now it seems it does autostart jackd but something shortly goes wrong. Last time I logged in I ran pstree and saw that jackd is open, but when I opened amarok it complained and a second pstree showed no jackd - so somehow it got killed for some reason. But it never happens when I start jackd manually. Strange. I guess it could be a jackd bug rather than a xfce4-session issue, I don't know.
Reassign to xfce-bugs@xfce.org.
Closing this old bug report.