Ubuntu Manpage: jackd - JACK Audio Connection Kit sound server

NAME

       jackd - JACK Audio Connection Kit sound server

SYNOPSIS

       jackd [options] -d backend [backend-parameters]
       jackd --help

DESCRIPTION

       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/>.

OPTIONS

-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.

ALSA BACKEND OPTIONS
-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.

COREAUDIO BACKEND PARAMETERS
-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)

DUMMY BACKEND PARAMETERS
-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)

-w, --wait int
Number of usecs to wait between engine processes. (default: 21333)

NETONE BACKEND PARAMETERS
-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)

OSS BACKEND PARAMETERS
-r, --rate int
Sample rate. (default: 48000)

-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)

-e, --excl boolean
Request exclusive and direct access to the sound device. This avoids mixing and
automatic audio conversion in the OSS driver, and the extra latency that comes with
that. (default: false)

-I, --input-latency
Extra input latency (frames). (default: 0)

-O, --output-latency
Extra output latency (frames). (default: 0)

SUN BACKEND PARAMETERS
-r, --rate int
Sample rate. (default: 48000)

-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)

PORTAUDIO BACKEND PARAMETERS
-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)

FIREWIRE BACKEND PARAMETERS
-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)

-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.

EXAMPLES

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

ENVIRONMENT

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.

BUGS

       Please report bugs as issues to the corresponding repository:
       <http://www.github.com/jackaudio/>

AUTHORS

       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

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

ENVIRONMENT

SEE ALSO:

BUGS

AUTHORS