jackd - JACK Audio Connection Kit sound server
jackd [options] -d backend
[backend-parameters]
jackd --help
jackd is the JACK audio server daemon that allows JACK
client programs to process and route audio and MIDI data in a synchronous,
sample-accurate and low-latency manner. Originally written for the GNU/Linux
operating system, it also runs on various Unix platforms, Mac OS X and MS
Windows. JACK can connect a number of different client applications to an
audio device and also to each other. Most clients are external, running in
their own processes as normal applications. JACK also supports internal
clients, which run within the jackd process using a loadable
"plugin" interface.
JACK differs from other audio servers in being designed from the
ground up for professional audio work. It focuses on two key areas:
synchronous execution of all clients and low latency operation.
The name JACK makes a reference to the classical way of patching
audio connections with physical audio jack cables. JACK is also a recursive
acronym, that is an abbreviation which is part of itself. JACK
Audio Connection Kit.
For the latest JACK information please consult the web site:
<http://www.jackaudio.org/>.
- -d, --driver backend
[backend-parameters ]
-
Select the audio interface backend. The current list of supported backends
is: alsa, coreaudio, dummy, firewire,
oss sun and portaudio. They are not all available on
all platforms. All backend-parameters are optional.
- -h, --help
-
Print a brief usage message describing the main jackd options. These
do not include backend-parameters, which are listed using the
--help option for each specific backend. Examples below show how to
list them.
- -a, --autoconnect
modechar
- Select how to handle self connect requests. They can be ignore or fail, on
all port or just external ones. Use the --help option to know your
system specific options. The default is to not restrict self connect
requests.
- -m, --no-mlock
- Do not attempt to lock memory, even if --realtime.
- -n, --name
server-name
- Name this jackd instance server-name. If unspecified, this
name comes from the $JACK_DEFAULT_SERVER environment variable.
(default: "default")
- -p, --port-max
n
- Set the maximum number of ports the JACK server can manage. (default: 256)
- --replace-registry
-
Remove the shared memory registry used by all JACK server instances before
startup. This should rarely be used, and is intended only for occasions
when the structure of this registry changes in ways that are incompatible
across JACK versions (which is rare).
- -R, --realtime
-
Use realtime scheduling. This is needed for reliable low-latency
performance. On many systems, it requires jackd to run with special
scheduler and memory allocation privileges, which may be obtained in
several ways. (default: true)
- -r, --no-realtime
-
Do not use realtime scheduling.
- -P, --realtime-priority
int
- When running --realtime, set the scheduler priority to int.
- --silent
- Silence any output during operation.
- -T, --temporary
- Exit once all clients have closed their connections.
- -t, --timeout
int
-
Set client timeout limit in milliseconds. In realtime mode the client
timeout must be smaller than the watchdog timeout (5000 msec). (default:
500)
- -Z, --nozombies
-
Prevent JACK from ever kicking out clients because they were too slow. This
cancels the effect any specified timeout value, but JACK and its clients
are still subject to the supervision of the watchdog thread or its
equivalent.
- -C, --internal-session-file
internal-session-file
-
Load internal clients and connections from internal-session-file.
Each line of this configuration file starts with a command. The following
commands are available:
l(oad) client-name lib-name client-args
With this command an internal JACK client will be instantiated.
client-name and lib-name cannot contain spaces. The rest of
the line will be interpreted as client-args and sent to the client
library.
c(on) source-port destination-port
With this command a source port will be connected to a destination port.
source-port and destination-port cannot contain spaces.
Comments are allowed, they start with #.
An example configuration could look like the following:
l inprocess1 inprocess
l amp1 jalv http://lv2plug.in/plugins/eg-amp
c amp:out system:playback_1
- -u, --unlock
-
Unlock libraries GTK+, QT, FLTK, Wine.
- -v, --verbose
- Give verbose output.
- -c, --clocksource (
h(pet) | s(ystem) )
- Select a specific wall clock (HPET timer, System timer).
- -V, --version
- Print the current JACK version number and exit.
- -C, --capture [
name ]
- Provide only capture ports, unless combined with -D or -P. Optionally set
capture device name.
- -d, --device
name
-
The ALSA pcm device name to use. If none is specified, JACK will use
"hw:0", the first hardware card defined in
/etc/modules.conf.
- -z, --dither
[rectangular,triangular,shaped,none]
- Set dithering mode. If none or unspecified, dithering is off. Only
the first letter of the mode name is required.
- -D, --duplex
- Provide both capture and playback ports. Defaults to on unless only one of
-P or -C is specified. (default: true)
- -h, --help Print a
brief usage message describing only the
- alsa backend parameters.
- -M, --hwmeter
-
Enable hardware metering for devices that support it. Otherwise, use
software metering.
- -H, --hwmon
-
Enable hardware monitoring of capture ports. This is a method for obtaining
"zero latency" monitoring of audio input. It requires support in
hardware and from the underlying ALSA device driver.
When enabled, requests to monitor capture ports will be
satisfied by creating a direct signal path between audio interface input
and output connectors, with no processing by the host computer at all.
This offers the lowest possible latency for the monitored signal.
Presently (March 2003), only the RME Hammerfall series and
cards based on the ICE1712 chipset (M-Audio Delta series, Terratec, and
others) support --hwmon. In the future, some consumer cards may
also be supported by modifying their mixer settings.
Without --hwmon, port monitoring requires JACK to read
audio into system memory, then copy it back out to the hardware again,
imposing the basic JACK system latency determined by the --period
and --nperiods parameters.
- -i, --inchannels
int
-
Number of capture channels. (default: maximum supported by hardware)
- -I,
--input-latency
- Extra input latency (frames). (default: 0)
- -n, --nperiods
int
-
Number of periods of playback latency. In seconds, this corresponds to
--nperiods times --period divided by --rate. The
default is 2, the minimum allowed. For most devices, there is no need for
any other value with the --realtime option. Without realtime
privileges or with boards providing unreliable interrupts (like ymfpci), a
larger value may yield fewer xruns. This can also help if the system is
not tuned for reliable realtime scheduling.
For most ALSA devices, the hardware buffer has exactly
--period times --nperiods frames. Some devices demand a
larger buffer. If so, JACK will use the smallest possible buffer
containing at least --nperiods, but the playback latency does not
increase.
For USB audio devices it is recommended to use -n 3.
Firewire devices supported by FFADO (formerly FreeBoB) are configured
with -n 3 by default.
- -o, --outchannels
int
-
Number of playback channels. (default: maximum supported by hardware)
- -O,
--output-latency
- Extra output latency (frames). (default: 0)
- -P, --playback [
name ]
- Provide only playback ports, unless combined with -D or -C. Optionally set
playback device name.
- -p, --period
int
-
Number of frames between JACK process() calls. This value must be a
power of 2. If you need low latency, set -p as low as you can go
without seeing xruns. A larger period size yields higher latency, but
makes xruns less likely. The JACK capture latency in seconds is
--period divided by --rate. (default: 1024)
- -r, --rate
int
- Sample rate. (default: 48000)
- -S, --shorts
-
Try to configure card for 16-bit samples first, only trying 32-bits if
unsuccessful. (default: 32-bit samples)
- -s, --softmode
-
Ignore xruns reported by the ALSA driver. This makes JACK less likely to
disconnect unresponsive ports when running without --realtime.
- -X, --midi
[seq|raw]
-
Which ALSA MIDI system to provide access to. Using raw will provide a
set of JACK MIDI ports that correspond to each raw ALSA device on the
machine. Using seq will provide a set of JACK MIDI ports that
correspond to each ALSA "sequencer" client (which includes each
hardware MIDI port on the machine). raw provides slightly better
performance but does not permit JACK MIDI communication with software
written to use the ALSA "sequencer" API.
- -c, --channels
- Maximum number of channels. (default: 2)
- -i,
--inchannels
- Maximum number of input channels. (default: 2)
- -o,
--outchannels
- Maximum number of output channels. (default: 2)
- -C, --capture
- Whether or not to capture. (default: true)
- -P, --playback
- Whether or not to playback. (default: true)
- -D, --monitor
- Provide monitor ports for the output. (default: false)
- -D, --duplex
- Capture and playback. (default: true)
- -r, --rate
- Sample rate. (default: 44100)
- -p, --period
- Frames per period, must be a power of 2. (default: 128)
- -d, --device
- CoreAudio device name. (default: none)
- -I,
--input-latency
- Extra input latency (frames). (default: 0)
- -O,
--output-latency
- Extra output latency (frames). (default: 0)
- -l, --list-devices
- Display available CoreAudio devices. (default: false)
- -H, --hog
- Take exclusive access of the audio device. (default: false)
- -L, --async-latency
- Extra output latency in asynchronous mode (percent). (default: 100)
- -G, --grain
- Computation grain in RT thread (percent). (default: 100)
- -s, --clock-drift
- Whether or not to compensate clock drift in dynamically created aggregate
device. (default: false)
- -C, --capture
int
- Number of capture ports. (default: 2)
- -P, --playback
int
- Number of playback ports. (default: 2)
- -r, --rate
int
- Sample rate. (default: 48000)
- -p, --period
int
- Number of frames between JACK process() calls. This value must be a
power of 2. If you need low latency, set -p as low as you can go
without seeing xruns. A larger period size yields higher latency, but
makes xruns less likely. The JACK capture latency in seconds is
--period divided by --rate. (default: 1024)
- -w, --wait
int
- Number of usecs to wait between engine processes. (default: 21333)
- -i, --audio-ins
int
- Number of capture channels. (default: 2)
- -o, --audio-outs
int
- Number of playback channels. (default: 2)
- -I, --midi-ins
int
- Number of midi capture channels. (default: 1)
- -O, --midi-outs
int
- Number of midi playback channels. (default: 1)
- -r, --rate
int
- Sample rate. (default: 48000)
- -p, --period
int
- Frames per period. (default: 1024)
- -n, --num-periods
int
- Network latency setting in no. of periods. (default: 5)
- -l, --listen-port
int
- The socket port we are listening on for sync packets. (default: 3000)
- -f, --factor
int
- Factor for sample rate reduction. (default: 1)
- -u, --upstream-factor
int
- Factor for sample rate reduction on the upstream. (default: 0)
- -c, --celt
int
- Sets celt encoding and number of kbits per channel. (default: 0)
- -b, --bit-depth
int
- Sample bit-depth (0 for float, 8 for 8bit and 16 for 16bit). (default: 0)
- -t, --transport-sync
int
- Whether or not to slave the transport to the master transport. (default:
true)
- -a, --autoconf
int
- Whether or not to use Autoconfig, or just start. (default: true)
- -R, --redundancy
int
- Send packets N times. (default: 1)
- -e, --native-endian
int
- Don't convert samples to network byte order. (default: false)
- -J, --jitterval
int
- Attempted jitterbuffer microseconds on master. (default: 0)
- -D, --always-deadline
int
- Always use deadline. (default: false)
- -r, --rate
int
- Sample rate. (default: 48000)
- -p, --period
int
- Number of frames between JACK process() calls. This value must be a
power of 2. If you need low latency, set -p as low as you can go
without seeing xruns. A larger period size yields higher latency, but
makes xruns less likely. The JACK capture latency in seconds is
--period divided by --rate. (default: 1024)
- -n, --nperiods
int
- Number of periods in the hardware buffer. The period size (-p)
times --nperiods times four is the JACK buffer size in bytes. The
JACK output latency in seconds is --nperiods times --period
divided by --rate. (default: 2)
- -w, --wordlength
int
- Sample size in bits. (default: 16)
- -i, --inchannels
int
- Number of capture channels. (default: 2)
- -o, --outchannels
int
- Number of playback channels. (default: 2)
- -C, --capture
device_file
- Input device for capture. (default: /dev/dsp)
- -P, --playback
device_file
- Output device for playback. (default: /dev/dsp)
- -b, --ignorehwbuf
boolean
- Whether or not to ignore hardware period size. (default: false)
- -I,
--input-latency
- Extra input latency (frames). (default: 0)
- -O,
--output-latency
- Extra output latency (frames). (default: 0)
- -r, --rate
int
- Sample rate. (default: 48000)
- -p, --period
int
- Number of frames between JACK process() calls. This value must be a
power of 2. If you need low latency, set -p as low as you can go
without seeing xruns. A larger period size yields higher latency, but
makes xruns less likely. The JACK capture latency in seconds is
--period divided by --rate. (default: 1024)
- -n, --nperiods
int
- Number of periods in the hardware buffer. The period size (-p)
times --nperiods times four (assuming 2 channels 16-bit samples) is
the JACK buffer size in bytes. The JACK output latency in seconds is
--nperiods times --period divided by --rate.
(default: 2)
- -w, --wordlength
int
- Sample size in bits. (default: 16)
- -i, --inchannels
int
- Number of capture channels. (default: 2)
- -o, --outchannels
int
- Number of playback channels. (default: 2)
- -C, --capture
device_file
- Input device for capture. (default: /dev/audio)
- -P, --playback
device_file
- Output device for playback. (default: /dev/audio)
- -b, --ignorehwbuf
boolean
- Whether or not to ignore hardware period size. (default: false)
- -c, --channel
- Maximum number of channels. (default: all available hardware channels)
- -i,
--channelin
- Maximum number of input channels. (default: all available hardware
channels)
- -I,
--input-latency
- Extra input latency (frames). (default: 0)
- -o,
--channelout
- Maximum number of output channels. (default: all available hardware
channels)
- -O,
--output-latency
- Extra output latency (frames). (default: 0)
- -C, --capture
- Whether or not to capture. (default: true)
- -P, --playback
- Whether or not to playback. (default: true)
- -D, --duplex
- Capture and playback. (default: true)
- -r, --rate
- Sample rate. (default: 48000)
- -p, --period
- Frames per period, must be a power of 2. (default: 1024)
- -n, --name
- Driver name. (default: none)
- -z, --dither
- Dithering mode. (default: none)
- -d, --device
name
-
The Firewire device name to use. If none is specified, JACK will try
to use "hw:0". To get a list of available Firewire devices, see
ffado-test. It's recommended to use the GUID of a Firewire device
to rule out any ambiguities. Once the GUID of the device is known
("ffado-test ListDevices"), it can be used like
-dguid:0xff2584e39b078a2e to tell JACK which interface to use.
Sometimes resetting the Firewire bus can help ("ffado-test
BusReset") if there is any problem. (default: hw:0)
- -p, --period
int
-
Number of frames between JACK process() calls. This value must be a
power of 2. If you need low latency, set -p as low as you can go
without seeing xruns. A larger period size yields higher latency, but
makes xruns less likely. The JACK capture latency in seconds is
--period divided by --rate. (default: 1024)
- -n, --nperiods
int
-
Number of periods of playback latency. Value must be greater or equal 2. In
seconds, this corresponds to --nperiods times --period
divided by --rate. (default: 3)
- -r, --rate
int
- Sample rate. (default: 48000)
- -C, --capture [
name ]
- Provide only capture ports, unless combined with -D or -P. Optionally set
capture device name.
- -P, --playback [
name ]
- Provide only playback ports, unless combined with -D or -C. Optionally set
playback device name.
- -D, --duplex
- Provide both capture and playback ports. This option is the default
behaviour and can normally be omitted. -D can not be combined with -P or
-C.
- -I,
--input-latency
- Extra input latency (frames). (default: 0)
- -O,
--output-latency
- Extra output latency (frames). (default: 0)
- -v, --verbose
-
libffado verbose level. (default: 3)
- -X, --snoop
-
Snoop Firewire traffic. (default: false)
- -h, --help Print a
brief usage message describing only the
- firewire backend parameters.
Print usage message for the parameters specific to each
backend.
- jackd -d alsa --help
jackd -d coreaudio --help
jackd -d net --help
jackd -d dummy --help
jackd -d firewire --help
jackd -d oss --help
jackd -d sun --help
jackd -d portaudio --help
Run the JACK daemon with realtime priority using the first ALSA
hardware card defined in /etc/modules.conf.
- jackstart --realtime --driver=alsa
Run the JACK daemon with low latency giving verbose output, which
can be helpful for trouble-shooting system latency problems. A reasonably
well-tuned system with a good sound card and a low-latency kernel can handle
these values reliably. Some can do better. If you get xrun messages, try a
larger buffer. Tuning a system for low latency can be challenging. Please
consult the JACK FAQ for more suggestions.
- jackstart -Rv -d alsa -p 128 -n 2 -r 44100
Run jackd with realtime priority using the
"sblive" ALSA device defined in ~/.asoundrc. Apply shaped
dithering to playback audio.
- jackd -R -d alsa -d sblive --dither=shaped
Run jackd with no special privileges using the second ALSA
hardware card defined in /etc/modules.conf. Any xruns reported by the
ALSA backend will be ignored. The larger buffer helps reduce data loss.
Rectangular dithering will be used for playback.
- jackd -d alsa -d hw:1 -p2048 -n3 --softmode -zr
Run jackd in full-duplex mode using the ALSA hw:0,0 device
for playback and the hw:0,2 device for capture.
- jackd -d alsa -P hw:0,0 -C hw:0,2
Run jackd in playback-only mode using the ALSA hw:0,0
device.
- jackd -d alsa -P hw:0,0
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 using the command line found in the first line of
$HOME/.jackdrc if it exists, or /etc/jackdrc if it does not.
If neither file exists, a built-in default command will be used, including
the -T flag, which causes the server to shut down when all clients
have exited.
As a transition, this only happens when $JACK_START_SERVER
is defined in the environment of the calling process. In the future this
will become normal behavior. In either case, defining
$JACK_NO_START_SERVER disables this feature.
To change where JACK looks for the backend drivers, set
$JACK_DRIVER_DIR.
$JACK_DEFAULT_SERVER specifies the default server name. If
not defined, the string "default" is used. If set in their
respective environments, this affects jackd unless its --name
parameter is set, and all JACK clients unless they pass an explicit name to
jack_client_open().
Defining $JACK_NO_AUDIO_RESERVATION will bypass audio
device reservation via session bus (DBus). This can be useful if JACK was
compiled with DBus support but should run on a headless system.
$JACK_PROMISCUOUS_SERVER enables an alternate way of
handling the various shared resources (Unix sockets, semaphores, ...). In
this mode, the generated names will not contain the user id anymore, and the
permissions of those resources will be relaxed, allowing clients from
different users to talk with the same server. Moreover, on platforms that
support it (all POSIX variants), if set to a valid Unix group name or id,
the permissions will be restricted to that group, so only members of that
group will be able to launch clients that talk to this server. Important
note: it must be set with the same value for both server and clients to work
as expected.
<http://www.jackaudio.org/>
The official JACK website with news, docs and a list of JACK clients.
<http://www.github.com/jackaudio/>
The official JACK github code repository. Pull requests are welcome.
<http://lists.jackaudio.org/listinfo.cgi/jack-devel-jackaudio.org>
The JACK developers' mailing list. Subscribe to take part in development of
JACK or JACK clients. User questions are also welcome, there is no
user-specific mailing list.
<http://www.jackosx.com/>
Tools specific to the Mac OS X version of JACK.
<http://www.alsa-project.org/>
The Advanced Linux Sound Architecture.
<http://www.ffado.org/>
The Free Firewire Audio Drivers (FFADO) Site.
<irc.freenode.net#jack>
Join the JACK community with your favourite IRC client.
Please report bugs as issues to the corresponding repository:
<http://www.github.com/jackaudio/>
Architect and original implementer: Paul Davis
Original design group: Paul Davis, David Olofson, Kai Vehmanen,
Benno Sennoner, Richard Guenther and other members of the Linux Audio
Developers group.
Programming: Paul Davis, Jack O'Quin, Taybin Rutkin,
Stéphane Letz, Fernando Pablo Lopez-Lezcano, Steve Harris, Jeremy
Hall, Andy Wingo, Kai Vehmanen, Melanie Thielker, Jussi Laako, Tilman
Linneweh, Johnny Petrantoni, Torben Hohn.
Manpage written by Stefan Schwandter, Jack O'Quin, Alexandre
Prokoudine and Thomas Brand.
Create a PDF file from this manpage:
- man -t jackd | ps2pdf - > jackd.pdf