Hi,
I just discovered that pd -jack will start a jackd if there is none running already.
In src/s_audio_jack.c I found a comment saying that
(If no JACK server exists, jack_client_open() will start uone up by
default. It's not clear whether or not this is desirable; see long Pd
list thread started by yvan volochine, June 2013)
I would hereby vote for not starting the jackd server automatically, as jackd would pick up any ~/.jackdrc present in the user's homedir, which might not fit the desired sound card setup as ~/.jackdrc gets rewritten by qjackctl with its most recently used settings.
Once users (such as me) start using multiple sound cards, at multiple sampling rats, with multiple other parameters, it becomes very hard to have Pd autostart jack with the desired settings automatically. It would start jackd, but with possibly confusing and unwanted settings.
I changed the line 340 in src/s_audio_jack.c to jack_client = jack_client_open (client_name, JackNoStartServer, &status, NULL) and recompiled and am happy with the new behavior.
cheers, P