<s>
JACK	B-Application
Audio	I-Application
Connection	I-Application
Kit	I-Application
(	O
or	O
JACK	O
;	O
a	O
recursive	O
acronym	O
)	O
is	O
a	O
professional	O
sound	B-Application
server	I-Application
API	B-Application
and	O
pair	O
of	O
daemon	B-Operating_System
implementations	O
to	O
provide	O
real-time	B-Operating_System
,	O
low-latency	O
connections	O
for	O
both	O
audio	O
and	O
MIDI	O
data	O
between	O
applications	O
.	O
</s>
<s>
JACK	O
was	O
developed	O
by	O
a	O
community	O
of	O
open-source	O
developers	O
led	O
by	O
Paul	O
Davis	O
(	O
who	O
won	O
an	O
Open	O
Source	O
Award	O
in	O
2004	O
for	O
this	O
work	O
)	O
and	O
has	O
been	O
a	O
key	O
piece	O
of	O
infrastructure	O
and	O
the	O
de	O
facto	O
standard	O
for	O
professional	O
audio	O
software	O
on	O
Linux	B-Operating_System
since	O
its	O
inception	O
in	O
2002	O
.	O
</s>
<s>
The	O
server	O
is	O
free	B-Application
software	I-Application
,	O
licensed	O
under	O
GPL-2.0-or-later	B-License
,	O
while	O
the	O
library	O
is	O
licensed	O
under	O
LGPL-2.1-or-later	B-Application
.	O
</s>
<s>
The	O
JACK	O
API	B-Application
is	O
standardized	O
by	O
consensus	O
,	O
and	O
two	O
compatible	O
implementations	O
exist	O
:	O
jack1	O
,	O
which	O
is	O
implemented	O
in	O
plain	O
C	B-Language
and	O
has	O
been	O
in	O
maintenance	O
mode	O
for	O
a	O
while	O
,	O
and	O
jack2	O
(	O
originally	O
jackdmp	O
)	O
,	O
a	O
re-implementation	O
in	O
C++	B-Language
originally	O
led	O
by	O
Stéphane	O
Letz	O
,	O
which	O
introduced	O
multi-processor	O
scalability	O
and	O
support	O
for	O
operating	O
systems	O
other	O
than	O
Linux	B-Operating_System
.	O
</s>
<s>
JACK	O
can	O
be	O
used	O
with	O
ALSA	B-Application
,	O
PortAudio	B-Language
,	O
CoreAudio	B-Operating_System
,	O
FFADO	B-Application
and	O
OSS	B-Library
as	O
hardware	O
back-ends	B-Architecture
.	O
</s>
<s>
One	O
or	O
both	O
implementations	O
can	O
run	O
on	O
Linux	B-Operating_System
,	O
macOS	B-Application
,	O
Solaris	B-Application
,	O
Windows	B-Application
,	O
iOS	B-Application
,	O
FreeBSD	B-Operating_System
,	O
OpenBSD	B-Operating_System
and	O
NetBSD	B-Device
.	O
</s>
<s>
The	O
JACK	O
API	B-Application
is	O
also	O
implemented	O
by	O
PipeWire	B-Application
,	O
which	O
is	O
able	O
to	O
act	O
as	O
a	O
complete	O
drop-in	O
replacement	O
provider	O
for	O
JACK	O
clients	O
,	O
mapping	O
JACK	O
API	B-Application
calls	O
to	O
equivalent	O
PipeWire	B-Application
calls	O
.	O
</s>
<s>
If	O
used	O
as	O
a	O
replacement	O
for	O
ALSA	B-Application
and	O
PulseAudio	B-Library
as	O
well	O
,	O
it	O
can	O
unify	O
the	O
different	O
sound	B-Application
servers	I-Application
and	O
APIs	B-Application
that	O
might	O
be	O
typically	O
found	O
on	O
a	O
machine	O
,	O
and	O
allow	O
better	O
integration	O
between	O
different	O
software	O
.	O
</s>
<s>
PipeWire	B-Application
also	O
claims	O
to	O
add	O
a	O
number	O
of	O
features	O
and	O
fix	O
a	O
number	O
of	O
limitations	O
compared	O
to	O
JACK	O
.	O
</s>
<s>
The	O
use	O
of	O
PipeWire	B-Application
as	O
the	O
default	O
implementation	O
of	O
JACK	O
is	O
the	O
default	O
on	O
Fedora	O
34	O
and	O
newer	O
.	O
</s>
<s>
The	O
scheduling	O
requirements	O
of	O
JACK	O
to	O
achieve	O
sufficiently	O
low	O
latencies	O
were	O
one	O
of	O
the	O
driving	O
forces	O
behind	O
the	O
real-time	B-Operating_System
optimization	O
effort	O
for	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
2.6	I-Operating_System
series	O
,	O
whose	O
initial	O
latency	O
performance	O
had	O
been	O
disappointing	O
compared	O
to	O
the	O
older	O
2.4	O
series	O
.	O
</s>
<s>
Real-time	B-Operating_System
tuning	O
work	O
culminated	O
in	O
numerous	O
scheduling	O
improvements	O
to	O
the	O
mainline	O
kernel	B-Operating_System
and	O
the	O
creation	O
of	O
an	O
-rt	O
branch	O
for	O
more	O
intrusive	O
optimizations	O
in	O
the	O
release	O
2.6.24	O
,	O
and	O
later	O
the	O
CONFIG_PREEMPT_RT	O
patch	O
.	O
</s>
