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JACKD(1)							      JACKD(1)

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, a low-latency audio server.
       Originally written for the GNU/Linux operating system, it also supports
       Mac OS X and various Unix platforms.  JACK can connect a number of dif‐
       ferent 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:  synchro‐
       nous execution of all clients, and low latency operation.

       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  sup‐
	      ported backends is: alsa, coreaudio, dummy, freebob, 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.

       -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.  It
	      will be "default" if that is not defined.

       -p, --port-max  n
	      Set the maximum number of ports the JACK server can manage.  The
	      default value is 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	 (default  = true). This is needed for
	      reliable low-latency performance.	 On many systems, it  requires
	      jackd to run with special scheduler and memory allocation privi‐
	      leges, which may be obtained in several ways.

       -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.	 The  default  is  500
	      msec.   In realtime mode the client timeout must be smaller than
	      the watchdog timeout (5000 msec).

       -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.

       -u, --unlock
	      Unlock libraries GTK+, QT, FLTK, Wine.

       -v, --verbose
	      Give verbose output.

       -c, --clocksource ( c(ycle) |  h(pet)  |	 s(ystem) )
	      Select  a specific wall clock (Cycle Counter, 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.
	      Parameterally 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/mod‐
	      ules.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.

       -h, --help Print a brief usage message describing only the
	      alsa backend parameters.

       -M, --hwmeter
	      Enable  hardware	metering  for devices that support it.	Other‐
	      wise, 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 satis‐
	      fied by creating a direct signal path  between  audio  interface
	      input and output connectors, with no processing by the host com‐
	      puter 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 is maximum supported by
	      hardware.

       -n, --nperiods int
	      Specify the number of periods of playback latency.  In  seconds,
	      this corresponds to --nperiods times --period divided by --rate.
	      The default is 2, the  minimum  allowable.   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 real‐
	      time 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 is	maximum	 supported  by
	      hardware.

       -P, --playback [ name ]
	      Provide  only  playback  ports,  unless  combined with -D or -C.
	      Optionally set playback device name.

       -p, --period int
	      Specify the number of frames between JACK process() calls.  This
	      value  must  be  a  power of 2, and the default is 1024.	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.

       -r, --rate int
	      Specify the sample rate.	The default is 48000.

       -S, --shorts
	      Try  to  configure  card	for  16-bit samples first, only trying
	      32-bits if unsuccessful.	Default is to prefer 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]
	      Specify 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 (default: 128). Must be a power of 2.

       -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 to compensate clock drift in dynamically created	aggre‐
	      gate device (default: false)

   DUMMY BACKEND PARAMETERS
       -C, --capture int
	      Specify number of capture ports. The default value is 2.

       -P, --playback int
	      Specify number of playback ports. The default value is 2.

       -r, --rate int
	      Specify sample rate. The default value is 48000.

       -p, --period int
	      Specify the number of frames between JACK process() calls.  This
	      value must be a power of 2, and the default  is  1024.   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.

       -w, --wait int
	      Specify number of usecs to wait between engine  processes.   The
	      default value is 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 to slave the transport to the master transport (default:
	      true)

       -a, --autoconf int
	      Whether to use Autoconfig, or just start. (default: true)

       -R, --redundancy int
	      Send packets N times (default: 1)

       -e, --native-endian int
	      Dont 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
	      Specify the sample rate.	The default is 48000.

       -p, --period int
	      Specify the number of frames between JACK process() calls.  This
	      value  must  be  a  power of 2, and the default is 1024.	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.

       -n, --nperiods int
	      Specify  the  number  of	periods	 in  the hardware buffer.  The
	      default is 2.  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.

       -w, --wordlength int
	      Specify the sample size in bits. The default is 16.

       -i, --inchannels int
	      Specify how many channels to capture (default: 2)

       -o, --outchannels int
	      Specify number of playback channels (default: 2)

       -C, --capture device_file
	      Specify input device for capture (default: /dev/dsp)

       -P, --playback device_file
	      Specify output device for playback (default: /dev/dsp)

       -b, --ignorehwbuf boolean
	      Specify, whether to ignore hardware period size (default: false)

   SUN BACKEND PARAMETERS
       -r, --rate int
	      Specify the sample rate.	The default is 48000.

       -p, --period int
	      Specify the number of frames between JACK process() calls.  This
	      value  must  be  a  power of 2, and the default is 1024.	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.

       -n, --nperiods int
	      Specify  the  number  of	periods	 in  the hardware buffer.  The
	      default is 2.  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.

       -w, --wordlength int
	      Specify the sample size in bits. The default is 16.

       -i, --inchannels int
	      Specify how many channels to capture (default: 2)

       -o, --outchannels int
	      Specify number of playback channels (default: 2)

       -C, --capture device_file
	      Specify input device for capture (default: /dev/audio)

       -P, --playback device_file
	      Specify output device for playback (default: /dev/audio)

       -b, --ignorehwbuf boolean
	      Specify, whether 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	 hard‐
	      ware channels)

       -o --channelout
	      Maximum  number of output channels (default: all available hard‐
	      ware channels)

       -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 (default: 1024). Must be a power of 2.

       -n --name
	      Driver name (default: none)

       -z --dither
	      Dithering mode (default: none)

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 freebob --help
	      jackd -d oss --help
	      jackd -d sun --help
	      jackd -d portaudio --help

       Run the JACK daemon with realtime priority using the first  ALSA	 hard‐
       ware 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.  The JACK FAQ,  http://jackit.sourceforge.net/docs/faq.php
       has some useful 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 nei‐
       ther 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().

SEE ALSO:
       http://www.jackaudio.org
       The official JACK website with news, docs and a list of JACK clients.

       http://jackaudio.org/email
       The JACK developers' mailing list.  Subscribe, to take part in develop‐
       ment  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.

BUGS
       Please report bugs to
       http://trac.jackaudio.org/

AUTHORS
       Architect and original implementor: Paul Davis

       Original design Group: Paul Davis, David Olofson, Kai  Vehmanen,	 Benno
       Sennoner, Richard Guenther, and other members of the Linux Audio Devel‐
       opers group.

       Programming: Paul Davis, Jack O'Quin,  Taybin  Rutkin,  Stephane	 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 and Alexandre Prokou‐
       dine.

October 2013			    1.9.9.5			      JACKD(1)
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