1JACKD(1) JACKD(1)
2
6 jackd - JACK Audio Connection Kit sound server
7
11 jackd [options] -d backend [backend-parameters]
12 jackd --help
13
17 jackd is the JACK audio server daemon that allows JACK client programs
18 to process and route audio and MIDI data in a synchronous, sample-accu‐
19 rate and low-latency manner. Originally written for the GNU/Linux oper‐
20 ating system, it also runs on various Unix platforms, Mac OS X and MS
21 Windows. JACK can connect a number of different client applications to
22 an audio device and also to each other. Most clients are external, run‐
23 ning in their own processes as normal applications. JACK also supports
24 internal clients, which run within the jackd process using a loadable
25 "plugin" interface.
26 JACK differs from other audio servers in being designed from the ground
28 up for professional audio work. It focuses on two key areas: synchro‐
29 nous execution of all clients and low latency operation.
30 The name JACK makes a reference to the classical way of patching audio
32 connections with physical audio jack cables. JACK is also a recursive
33 acronym, that is an abbreviation which is part of itself. JACK Audio
34 Connection Kit.
35 For the latest JACK information please consult the web site:
37 <http://www.jackaudio.org/>.
38
42 -d, --driver backend [backend-parameters ]
43 Select the audio interface backend. The current list of sup‐
44 ported backends is: alsa, coreaudio, dummy, firewire, oss sun
45 and portaudio. They are not all available on all platforms. All
46 backend-parameters are optional.
47 -h, --help
50 Print a brief usage message describing the main jackd options.
51 These do not include backend-parameters, which are listed using
52 the --help option for each specific backend. Examples below show
53 how to list them.
54 -a, --autoconnect modechar
57 Select how to handle self connect requests. They can be ignore
58 or fail, on all port or just external ones. Use the --help op‐
59 tion to know your system specific options. The default is to not
60 restrict self connect requests.
61 -m, --no-mlock
63 Do not attempt to lock memory, even if --realtime.
64 -n, --name server-name
67 Name this jackd instance server-name. If unspecified, this name
68 comes from the $JACK_DEFAULT_SERVER environment variable. (de‐
69 fault: "default")
70 -p, --port-max n
73 Set the maximum number of ports the JACK server can manage.
74 (default: 256)
75 --replace-registry
78 Remove the shared memory registry used by all JACK server in‐
79 stances before startup. This should rarely be used, and is in‐
80 tended only for occasions when the structure of this registry
81 changes in ways that are incompatible across JACK versions
82 (which is rare).
83 -R, --realtime
86 Use realtime scheduling. This is needed for reliable low-latency
87 performance. On many systems, it requires jackd to run with spe‐
88 cial scheduler and memory allocation privileges, which may be
89 obtained in several ways. (default: true)
90 -r, --no-realtime
93 Do not use realtime scheduling.
94 -P, --realtime-priority int
97 When running --realtime, set the scheduler priority to int.
98 --silent
101 Silence any output during operation.
102 -T, --temporary
106 Exit once all clients have closed their connections.
107 -t, --timeout int
110 Set client timeout limit in milliseconds. In realtime mode the
111 client timeout must be smaller than the watchdog timeout (5000
112 msec). (default: 500)
113 -Z, --nozombies
116 Prevent JACK from ever kicking out clients because they were too
117 slow. This cancels the effect any specified timeout value, but
118 JACK and its clients are still subject to the supervision of the
119 watchdog thread or its equivalent.
120 -C, --internal-session-file internal-session-file
123 Load internal clients and connections from internal-session-
124 file. Each line of this configuration file starts with a com‐
125 mand. The following commands are available:
126 l(oad) client-name lib-name client-args
127 With this command an internal JACK client will be instantiated.
128 client-name and lib-name cannot contain spaces. The rest of the
129 line will be interpreted as client-args and sent to the client
130 library.
131 c(on) source-port destination-port
132 With this command a source port will be connected to a destina‐
133 tion port. source-port and destination-port cannot contain spa‐
134 ces.
135 Comments are allowed, they start with #.
136 An example configuration could look like the following:
137 l inprocess1 inprocess
138 l amp1 jalv http://lv2plug.in/plugins/eg-amp
139 c amp:out system:playback_1
140 -u, --unlock
143 Unlock libraries GTK+, QT, FLTK, Wine.
144 -v, --verbose
147 Give verbose output.
148 -c, --clocksource ( h(pet) | s(ystem) )
151 Select a specific wall clock (HPET timer, System timer).
152 -V, --version
155 Print the current JACK version number and exit.
156 ALSA BACKEND OPTIONS
160 -C, --capture [ name ]
161 Provide only capture ports, unless combined with -D or -P. Op‐
162 tionally set capture device name.
163 -d, --device name
166 The ALSA pcm device name to use. If none is specified, JACK will
167 use "hw:0", the first hardware card defined in /etc/mod‐
168 ules.conf.
169 -z, --dither [rectangular,triangular,shaped,none]
172 Set dithering mode. If none or unspecified, dithering is off.
173 Only the first letter of the mode name is required.
174 -D, --duplex
177 Provide both capture and playback ports. Defaults to on unless
178 only one of -P or -C is specified. (default: true)
179 -h, --help Print a brief usage message describing only the
182 alsa backend parameters.
183 -M, --hwmeter
186 Enable hardware metering for devices that support it. Otherwise,
187 use software metering.
188 -H, --hwmon
191 Enable hardware monitoring of capture ports. This is a method
192 for obtaining "zero latency" monitoring of audio input. It re‐
193 quires support in hardware and from the underlying ALSA device
194 driver.
195 When enabled, requests to monitor capture ports will be satis‐
197 fied by creating a direct signal path between audio interface
198 input and output connectors, with no processing by the host com‐
199 puter at all. This offers the lowest possible latency for the
200 monitored signal.
201 Presently (March 2003), only the RME Hammerfall series and cards
203 based on the ICE1712 chipset (M-Audio Delta series, Terratec,
204 and others) support --hwmon. In the future, some consumer cards
205 may also be supported by modifying their mixer settings.
206 Without --hwmon, port monitoring requires JACK to read audio
208 into system memory, then copy it back out to the hardware again,
209 imposing the basic JACK system latency determined by the --pe‐
210 riod and --nperiods parameters.
211 -i, --inchannels int
214 Number of capture channels. (default: maximum supported by
215 hardware)
216 -I, --input-latency
219 Extra input latency (frames). (default: 0)
220 -n, --nperiods int
223 Number of periods of playback latency. In seconds, this corre‐
224 sponds to --nperiods times --period divided by --rate. The de‐
225 fault is 2, the minimum allowed. For most devices, there is no
226 need for any other value with the --realtime option. Without re‐
227 altime privileges or with boards providing unreliable interrupts
228 (like ymfpci), a larger value may yield fewer xruns. This can
229 also help if the system is not tuned for reliable realtime
230 scheduling.
231 For most ALSA devices, the hardware buffer has exactly --period
233 times --nperiods frames. Some devices demand a larger buffer. If
234 so, JACK will use the smallest possible buffer containing at
235 least --nperiods, but the playback latency does not increase.
236 For USB audio devices it is recommended to use -n 3. Firewire
238 devices supported by FFADO (formerly FreeBoB) are configured
239 with -n 3 by default.
240 -o, --outchannels int
243 Number of playback channels. (default: maximum supported by
244 hardware)
245 -O, --output-latency
248 Extra output latency (frames). (default: 0)
249 -P, --playback [ name ]
252 Provide only playback ports, unless combined with -D or -C. Op‐
253 tionally set playback device name.
254 -p, --period int
257 Number of frames between JACK process() calls. This value must
258 be a power of 2. If you need low latency, set -p as low as you
259 can go without seeing xruns. A larger period size yields higher
260 latency, but makes xruns less likely. The JACK capture latency
261 in seconds is --period divided by --rate. (default: 1024)
262 -r, --rate int
265 Sample rate. (default: 48000)
266 -S, --shorts
269 Try to configure card for 16-bit samples first, only trying
270 32-bits if unsuccessful. (default: 32-bit samples)
271 -s, --softmode
274 Ignore xruns reported by the ALSA driver. This makes JACK less
275 likely to disconnect unresponsive ports when running without
276 --realtime.
277 -X, --midi [seq|raw]
280 Which ALSA MIDI system to provide access to. Using raw will pro‐
281 vide a set of JACK MIDI ports that correspond to each raw ALSA
282 device on the machine. Using seq will provide a set of JACK MIDI
283 ports that correspond to each ALSA "sequencer" client (which in‐
284 cludes each hardware MIDI port on the machine). raw provides
285 slightly better performance but does not permit JACK MIDI commu‐
286 nication with software written to use the ALSA "sequencer" API.
287 COREAUDIO BACKEND PARAMETERS
291 -c, --channels
292 Maximum number of channels. (default: 2)
293 -i, --inchannels
296 Maximum number of input channels. (default: 2)
297 -o, --outchannels
300 Maximum number of output channels. (default: 2)
301 -C, --capture
304 Whether or not to capture. (default: true)
305 -P, --playback
308 Whether or not to playback. (default: true)
309 -D, --monitor
312 Provide monitor ports for the output. (default: false)
313 -D, --duplex
316 Capture and playback. (default: true)
317 -r, --rate
320 Sample rate. (default: 44100)
321 -p, --period
324 Frames per period, must be a power of 2. (default: 128)
325 -d, --device
328 CoreAudio device name. (default: none)
329 -I, --input-latency
332 Extra input latency (frames). (default: 0)
333 -O, --output-latency
336 Extra output latency (frames). (default: 0)
337 -l, --list-devices
340 Display available CoreAudio devices. (default: false)
341 -H, --hog
344 Take exclusive access of the audio device. (default: false)
345 -L, --async-latency
348 Extra output latency in asynchronous mode (percent). (default:
349 100)
350 -G, --grain
353 Computation grain in RT thread (percent). (default: 100)
354 -s, --clock-drift
357 Whether or not to compensate clock drift in dynamically created
358 aggregate device. (default: false)
359 DUMMY BACKEND PARAMETERS
363 -C, --capture int
364 Number of capture ports. (default: 2)
365 -P, --playback int
368 Number of playback ports. (default: 2)
369 -r, --rate int
372 Sample rate. (default: 48000)
373 -p, --period int
376 Number of frames between JACK process() calls. This value must
377 be a power of 2. If you need low latency, set -p as low as you
378 can go without seeing xruns. A larger period size yields higher
379 latency, but makes xruns less likely. The JACK capture latency
380 in seconds is --period divided by --rate. (default: 1024)
381 -w, --wait int
384 Number of usecs to wait between engine processes. (default:
385 21333)
386 NETONE BACKEND PARAMETERS
390 -i, --audio-ins int
391 Number of capture channels. (default: 2)
392 -o, --audio-outs int
395 Number of playback channels. (default: 2)
396 -I, --midi-ins int
399 Number of midi capture channels. (default: 1)
400 -O, --midi-outs int
403 Number of midi playback channels. (default: 1)
404 -r, --rate int
407 Sample rate. (default: 48000)
408 -p, --period int
411 Frames per period. (default: 1024)
412 -n, --num-periods int
415 Network latency setting in no. of periods. (default: 5)
416 -l, --listen-port int
419 The socket port we are listening on for sync packets. (default:
420 3000)
421 -f, --factor int
424 Factor for sample rate reduction. (default: 1)
425 -u, --upstream-factor int
428 Factor for sample rate reduction on the upstream. (default: 0)
429 -c, --celt int
432 Sets celt encoding and number of kbits per channel. (default:
433 0)
434 -b, --bit-depth int
437 Sample bit-depth (0 for float, 8 for 8bit and 16 for 16bit).
438 (default: 0)
439 -t, --transport-sync int
442 Whether or not to slave the transport to the master transport.
443 (default: true)
444 -a, --autoconf int
447 Whether or not to use Autoconfig, or just start. (default:
448 true)
449 -R, --redundancy int
452 Send packets N times. (default: 1)
453 -e, --native-endian int
456 Don't convert samples to network byte order. (default: false)
457 -J, --jitterval int
459 Attempted jitterbuffer microseconds on master. (default: 0)
460 -D, --always-deadline int
463 Always use deadline. (default: false)
464 OSS BACKEND PARAMETERS
468 -r, --rate int
469 Sample rate. (default: 48000)
470 -p, --period int
473 Number of frames between JACK process() calls. This value must
474 be a power of 2. If you need low latency, set -p as low as you
475 can go without seeing xruns. A larger period size yields higher
476 latency, but makes xruns less likely. The JACK capture latency
477 in seconds is --period divided by --rate. (default: 1024)
478 -n, --nperiods int
481 Number of periods in the hardware buffer. The period size (-p)
482 times --nperiods times four is the JACK buffer size in bytes.
483 The JACK output latency in seconds is --nperiods times --period
484 divided by --rate. (default: 2)
485 -w, --wordlength int
488 Sample size in bits. (default: 16)
489 -i, --inchannels int
492 Number of capture channels. (default: 2)
493 -o, --outchannels int
496 Number of playback channels. (default: 2)
497 -C, --capture device_file
500 Input device for capture. (default: /dev/dsp)
501 -P, --playback device_file
504 Output device for playback. (default: /dev/dsp)
505 -b, --ignorehwbuf boolean
508 Whether or not to ignore hardware period size. (default: false)
509 -I, --input-latency
512 Extra input latency (frames). (default: 0)
513 -O, --output-latency
516 Extra output latency (frames). (default: 0)
517 SUN BACKEND PARAMETERS
521 -r, --rate int
522 Sample rate. (default: 48000)
523 -p, --period int
526 Number of frames between JACK process() calls. This value must
527 be a power of 2. If you need low latency, set -p as low as you
528 can go without seeing xruns. A larger period size yields higher
529 latency, but makes xruns less likely. The JACK capture latency
530 in seconds is --period divided by --rate. (default: 1024)
531 -n, --nperiods int
534 Number of periods in the hardware buffer. The period size (-p)
535 times --nperiods times four (assuming 2 channels 16-bit samples)
536 is the JACK buffer size in bytes. The JACK output latency in
537 seconds is --nperiods times --period divided by --rate. (de‐
538 fault: 2)
539 -w, --wordlength int
542 Sample size in bits. (default: 16)
543 -i, --inchannels int
546 Number of capture channels. (default: 2)
547 -o, --outchannels int
550 Number of playback channels. (default: 2)
551 -C, --capture device_file
554 Input device for capture. (default: /dev/audio)
555 -P, --playback device_file
558 Output device for playback. (default: /dev/audio)
559 -b, --ignorehwbuf boolean
562 Whether or not to ignore hardware period size. (default: false)
563 PORTAUDIO BACKEND PARAMETERS
567 -c, --channel
568 Maximum number of channels. (default: all available hardware
569 channels)
570 -i, --channelin
573 Maximum number of input channels. (default: all available hard‐
574 ware channels)
575 -I, --input-latency
578 Extra input latency (frames). (default: 0)
579 -o, --channelout
582 Maximum number of output channels. (default: all available
583 hardware channels)
584 -O, --output-latency
587 Extra output latency (frames). (default: 0)
588 -C, --capture
591 Whether or not to capture. (default: true)
592 -P, --playback
595 Whether or not to playback. (default: true)
596 -D, --duplex
599 Capture and playback. (default: true)
600 -r, --rate
603 Sample rate. (default: 48000)
604 -p, --period
607 Frames per period, must be a power of 2. (default: 1024)
608 -n, --name
611 Driver name. (default: none)
612 -z, --dither
615 Dithering mode. (default: none)
616 FIREWIRE BACKEND PARAMETERS
620 -d, --device name
621 The Firewire device name to use. If none is specified, JACK will
622 try to use "hw:0". To get a list of available Firewire devices,
623 see ffado-test. It's recommended to use the GUID of a Firewire
624 device to rule out any ambiguities. Once the GUID of the device
625 is known ("ffado-test ListDevices"), it can be used like
626 -dguid:0xff2584e39b078a2e to tell JACK which interface to use.
627 Sometimes resetting the Firewire bus can help ("ffado-test Bus‐
628 Reset") if there is any problem. (default: hw:0)
629 -p, --period int
632 Number of frames between JACK process() calls. This value must
633 be a power of 2. If you need low latency, set -p as low as you
634 can go without seeing xruns. A larger period size yields higher
635 latency, but makes xruns less likely. The JACK capture latency
636 in seconds is --period divided by --rate. (default: 1024)
637 -n, --nperiods int
640 Number of periods of playback latency. Value must be greater or
641 equal 2. In seconds, this corresponds to --nperiods times --pe‐
642 riod divided by --rate. (default: 3)
643 -r, --rate int
646 Sample rate. (default: 48000)
647 -C, --capture [ name ]
650 Provide only capture ports, unless combined with -D or -P. Op‐
651 tionally set capture device name.
652 -P, --playback [ name ]
655 Provide only playback ports, unless combined with -D or -C. Op‐
656 tionally set playback device name.
657 -D, --duplex
660 Provide both capture and playback ports. This option is the de‐
661 fault behaviour and can normally be omitted. -D can not be com‐
662 bined with -P or -C.
663 -I, --input-latency
666 Extra input latency (frames). (default: 0)
667 -O, --output-latency
670 Extra output latency (frames). (default: 0)
671 -v, --verbose
674 libffado verbose level. (default: 3)
675 -X, --snoop
678 Snoop Firewire traffic. (default: false)
679 -h, --help Print a brief usage message describing only the
682 firewire backend parameters.
683
687 Print usage message for the parameters specific to each backend.
688 jackd -d alsa --help
691 jackd -d coreaudio --help
692 jackd -d net --help
693 jackd -d dummy --help
694 jackd -d firewire --help
695 jackd -d oss --help
696 jackd -d sun --help
697 jackd -d portaudio --help
698 Run the JACK daemon with realtime priority using the first ALSA hard‐
700 ware card defined in /etc/modules.conf.
701 jackstart --realtime --driver=alsa
704 Run the JACK daemon with low latency giving verbose output, which can
706 be helpful for trouble-shooting system latency problems. A reasonably
707 well-tuned system with a good sound card and a low-latency kernel can
708 handle these values reliably. Some can do better. If you get xrun mes‐
709 sages, try a larger buffer. Tuning a system for low latency can be
710 challenging. Please consult the JACK FAQ for more suggestions.
711 jackstart -Rv -d alsa -p 128 -n 2 -r 44100
714 Run jackd with realtime priority using the "sblive" ALSA device defined
716 in ~/.asoundrc. Apply shaped dithering to playback audio.
717 jackd -R -d alsa -d sblive --dither=shaped
720 Run jackd with no special privileges using the second ALSA hardware
722 card defined in /etc/modules.conf. Any xruns reported by the ALSA back‐
723 end will be ignored. The larger buffer helps reduce data loss. Rectan‐
724 gular dithering will be used for playback.
725 jackd -d alsa -d hw:1 -p2048 -n3 --softmode -zr
728 Run jackd in full-duplex mode using the ALSA hw:0,0 device for playback
730 and the hw:0,2 device for capture.
731 jackd -d alsa -P hw:0,0 -C hw:0,2
734 Run jackd in playback-only mode using the ALSA hw:0,0 device.
736 jackd -d alsa -P hw:0,0
739
743 JACK is evolving a mechanism for automatically starting the server when
744 needed. Any client started without a running JACK server will attempt
745 to start one itself using the command line found in the first line of
746 $HOME/.jackdrc if it exists, or /etc/jackdrc if it does not. If neither
747 file exists, a built-in default command will be used, including the -T
748 flag, which causes the server to shut down when all clients have ex‐
749 ited.
750 As a transition, this only happens when $JACK_START_SERVER is defined
752 in the environment of the calling process. In the future this will be‐
753 come normal behavior. In either case, defining $JACK_NO_START_SERVER
754 disables this feature.
755 To change where JACK looks for the backend drivers, set
757 $JACK_DRIVER_DIR.
758 $JACK_DEFAULT_SERVER specifies the default server name. If not defined,
760 the string "default" is used. If set in their respective environments,
761 this affects jackd unless its --name parameter is set, and all JACK
762 clients unless they pass an explicit name to jack_client_open().
763 Defining $JACK_NO_AUDIO_RESERVATION will bypass audio device reserva‐
765 tion via session bus (DBus). This can be useful if JACK was compiled
766 with DBus support but should run on a headless system.
767 $JACK_PROMISCUOUS_SERVER enables an alternate way of handling the vari‐
769 ous shared resources (Unix sockets, semaphores, ...). In this mode, the
770 generated names will not contain the user id anymore, and the permis‐
771 sions of those resources will be relaxed, allowing clients from differ‐
772 ent users to talk with the same server. Moreover, on platforms that
773 support it (all POSIX variants), if set to a valid Unix group name or
774 id, the permissions will be restricted to that group, so only members
775 of that group will be able to launch clients that talk to this server.
776 Important note: it must be set with the same value for both server and
777 clients to work as expected.
778
781 <http://www.jackaudio.org/>
782 The official JACK website with news, docs and a list of JACK clients.
783 <http://www.github.com/jackaudio/>
785 The official JACK github code repository. Pull requests are welcome.
786 <http://lists.jackaudio.org/listinfo.cgi/jack-devel-jackaudio.org>
788 The JACK developers' mailing list. Subscribe to take part in develop‐
789 ment of JACK or JACK clients. User questions are also welcome, there is
790 no user-specific mailing list.
791 <http://www.jackosx.com/>
793 Tools specific to the Mac OS X version of JACK.
794 <http://www.alsa-project.org/>
796 The Advanced Linux Sound Architecture.
797 <http://www.ffado.org/>
799 The Free Firewire Audio Drivers (FFADO) Site.
800 <irc.freenode.net#jack>
802 Join the JACK community with your favourite IRC client.
803
807 Please report bugs as issues to the corresponding repository:
808 <http://www.github.com/jackaudio/>
809
813 Architect and original implementer: Paul Davis
814 Original design group: Paul Davis, David Olofson, Kai Vehmanen, Benno
816 Sennoner, Richard Guenther and other members of the Linux Audio Devel‐
817 opers group.
818 Programming: Paul Davis, Jack O'Quin, Taybin Rutkin, Stéphane Letz,
820 Fernando Pablo Lopez-Lezcano, Steve Harris, Jeremy Hall, Andy Wingo,
821 Kai Vehmanen, Melanie Thielker, Jussi Laako, Tilman Linneweh, Johnny
822 Petrantoni, Torben Hohn.
823 Manpage written by Stefan Schwandter, Jack O'Quin, Alexandre Prokoudine
825 and Thomas Brand.
826 Create a PDF file from this manpage:
828 man -t jackd | ps2pdf - > jackd.pdf
8301.9.19 July 2021 JACKD(1)