[pulseaudio-discuss] Can PulseAudio "automatically start" jackd?

[Tanu Kaskinen]

On Sat, 2017-11-11 at 02:07 +0000, Jaime T wrote:
> Hi all.
> 
> As per "man jackd", "JACK is evolving a mechanism for automatically
> starting the server when needed. Any client started without a running
> JACK server will attempt to start one itself...". I've got a laptop
> running Debian 9 (Stretch) and this "automatic starting" mechanism for
> jack works perfectly. I know this because "ps aux | grep -i jackd"
> returns:
> 
> nonroot  10609  0.0  0.0   4728   852 pts/4    S+   01:08   0:00 grep -i jackd
> 
> before I run jack-play,
> 
> nonroot  10640  8.3  3.9  83412 82100 ?        SLsl 01:11   0:00
> /usr/bin/jackd -T -ndefault -T -d alsa
> nonroot  10650  0.0  0.0   4728   828 pts/4    S+   01:11   0:00 grep -i jackd
> 
> while I am running jack-play, and:
> 
> nonroot  10658  0.0  0.0   4728   836 pts/4    S+   01:12   0:00 grep -i jackd
> 
> (again) after jack-play has terminated.
> 
> I thought that pulseaudio might be able to use this autostart
> mechanism, so I've installed pulseaudio-module-jack, but when I run
> "pactl load-module module-jack-sink channels=2", I get either:
> "Failure: Module initialization failed" or "Module load failed.", and
> "tail -f /var/log/syslog" returns something like:
> 
> Nov 11 01:52:07 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >JACK died - calling shutdown handler<
> Nov 11 01:52:29 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >connect(2) call to
> /dev/shm/jack-1000/default/jack_0 failed (err=No such file or
> directory)<
> Nov 11 01:52:30 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >connect(2) call to
> /dev/shm/jack-1000/default/jack_0 failed (err=No such file or
> directory)<
> Nov 11 01:52:31 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >connect(2) call to
> /dev/shm/jack-1000/default/jack_0 failed (err=No such file or
> directory)<
> Nov 11 01:52:32 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >connect(2) call to
> /dev/shm/jack-1000/default/jack_0 failed (err=No such file or
> directory)<
> Nov 11 01:52:33 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >connect(2) call to
> /dev/shm/jack-1000/default/jack_0 failed (err=No such file or
> directory)<
> Nov 11 01:52:34 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >connect(2) call to
> /dev/shm/jack-1000/default/jack_0 failed (err=No such file or
> directory)<
> Nov 11 01:52:35 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: JACK error >attempt to connect to server failed<
> Nov 11 01:52:35 piano pulseaudio[887]: [pulseaudio]
> module-jack-sink.c: jack_client_open() failed.
> Nov 11 01:52:35 piano pulseaudio[887]: [pulseaudio] module.c: Failed
> to load module "module-jack-sink" (argument: "channels=2"):
> initialization failed.
> 
> Note that if I explicitly (manually) start jackd *before* running
> "pactl load-module module-jack-sink channels=2", then all is good.
> 
> I have also found
> https://docs-old.fedoraproject.org/en-US/Fedora/16/html/Musicians_Guide/sect-Musicians_Guide-Integrating_PulseAudio_with_JACK.html
> which makes me think that this *should* work (it includes the words
> "When PulseAudio starts JACK").
> 
> My question is: is pulseaudio's "not automatically starting" jackd
> expected, or is it a bug?

I believe jack_client_open() should start jackd, but apparently that's
not working. I'm not familiar with how the automatic starting works, I
can only tell that PulseAudio doesn't deliberately disable the
automatic jackd starting.

-- 
Tanu

https://www.patreon.com/tanuk