Linux Cross Reference
JACK/jackd/jackd.1.in

   .TH JACKD "1" @VERSION@ "October 2003"
   .SH NAME
   jackd, jackstart \- JACK Audio Connection Kit sound server
   .SH SYNOPSYS
   \fBjackd\fR [ \fI options \fR ] \fB \-d \fI driver \fR 
   [\fI driver options \fR ]
   .br
   \fBjackstart\fR [ \fI options \fR ] \fB \-d \fI driver \fR 
   [\fI driver options \fR ]
  .br
  \fBjackd \-\-help\fR
  .SH DESCRIPTION
  \fBjackd\fR invokes the JACK audio server daemon.  When using JACK's
  built-in support for realtime capabilities, use the \fBjackstart\fR
  command, instead.  All options are the same.
  
  JACK is a low-latency audio server, originally written for the
  GNU/Linux operating system.  It can connect a number of different JACK
  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 \fBjackd\fR 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.
  
  For the latest JACK information, please consult the web site,
  <\fBhttp://jackit.sourceforge.net\fR>.
  .SH OPTIONS
  .TP
  \fB\-d, \-\-driver \fI driver \fR [ \fI driver-options \fR ] 
  .br
  Select the output driver.  The only \fIdriver\fR currently documented
  is \fBalsa\fR (see below).  There are additional drivers named
  \fBdummy\fR and \fBportaudio\fR.  Examples below show how to list
  their parameters.
  .TP
  \fB\-h, \-\-help\fR
  .br
  Print a brief usage message describing the main \fBjackd\fR options.
  These do not include driver options, which are obtained using the
  \fB\-\-help\fR option for that specific driver, instead.
  .TP
  \fB\-R, \-\-realtime\fR 
  .br
  Use realtime scheduling.  This is needed for reliable low-latency
  performance.  It requires \fBjackd\fR to run with special scheduler
  and memory allocation privileges, which may be obtained in two ways.
  The first method is to run \fBjackd\fR with root privileges, which
  means that all JACK clients must also run as root.  The second method
  requires a kernel with "POSIX draft capabilities" enabled (see the
  \fB<linux/capability.h>\fR include file).  Then, an ordinary user can
  invoke the daemon using \fBjackstart\fR, and later launch JACK clients
  without running as root.
  .TP
  \fB\-P, \-\-realtime\-priority \fIint\fR
  When running \fB\-\-realtime\fR, set the scheduler priority to
  \fIint\fR.
  .TP
  \fB\-\-silent\fR
  Stops any output during operation.
  .TP
  \fB\-t, \-\-timeout \fIint\fR
  .br
  Set client timeout limit in microseconds.  The default is 500 msec
  when not in realtime mode (see: \-R).
  .TP
  \fB\-v, \-\-verbose\fR
  Give verbose output.
  .TP
  \fB\-V, \-\-version\fR
  Print the current JACK version number and exit.
  .SS ALSA DRIVER OPTIONS
  .TP
  \fB\-C, \-\-capture\fR [ \fIname\fR ]
  Provide only capture ports.  Optionally set device name.
  .TP
  \fB\-d, \-\-device \fIname\fR
  .br
  The ALSA pcm device \fIname\fR to use.  If none is specified, JACK will
  use "hw:0", the first hardware card defined in \fB/etc/modules.conf\fR.
  .TP
  \fB\-z, --dither [rectangular,triangular,shaped,none]
  Set dithering mode.  If \fBnone\fR or unspecified, dithering is off.
  Only the first letter of the mode name is required.
  .TP
  \fB\-D, \-\-duplex\fR
  Provide both capture and playback ports (the default).
  .TP
  \fB\-h, \-\-help\fR Print a brief usage message describing only the
  \fBalsa\fR driver options.
  .TP
  \fB\-M, \-\-hwmeter\fR
  .br
  Enable hardware metering for devices that support it.  Otherwise, use
  software metering.
  .TP
  \fB\-H, \-\-hwmon\fR
 .br
 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 \fB\-\-hwmon\fR.  In the future, some consumer cards may also
 be supported by modifying their mixer settings.
 
 Without \fB\-\-hwmon\fR, 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
 \fB\-\-period\fR and \fB\-\-nperiods\fR options.
 .TP
 \fB\-i, \-\-inchannels \fIint\fR
 .br
 Number of capture channels.  Default is maximum supported by hardware.
 .TP
 \fB\-n, \-\-nperiods \fIint\fR
 .br
 Specify the number of periods in the hardware buffer.  The default is
 2.  The period size (\fB\-p\fR) times \fB\-\-nperiods\fR times four is
 the JACK buffer size in bytes.  The JACK output latency in seconds is
 \fB\-\-nperiods\fR times \fB\-\-period\fR divided by \fB\-\-rate\fR.
 .TP
 \fB\-o, \-\-outchannels \fIint\fR
 .br
 Number of playback channels.  Default is maximum supported by hardware.
 .TP
 \fB\-P, \-\-playback\fR [ \fIname\fR ]
 Provide only playback ports.  Optionally set device name.
 .TP
 \fB\-p, \-\-period \fIint\fR
 .br
 Specify the number of frames between JACK \fBprocess()\fR calls.  The
 default is 1024.  If you need low latency, set \fB\-p\fR as low as you
 can go without seeing xruns.  A larger period size yields higher
 latency, but makes xruns less likely.  The JACK input latency in
 seconds is \fB\-\-period\fR divided by \fB\-\-rate\fR.
 .TP
 \fB\-r, \-\-rate \fIint\fR
 Specify the sample rate.  The default is 48000.
 .TP
 \fB\-S, \-\-shorts
 .br
 Try to configure card for 16-bit samples first, only trying 32-bits if
 unsuccessful.  Default is to prefer 32-bit samples.
 .TP
 \fB\-s, \-\-softmode\fR 
 .br
 Ignore xruns reported by the ALSA driver.  This makes JACK less likely
 to disconnect unresponsive ports when running without
 \fB\-\-realtime\fR.
 .SH EXAMPLES
 .PP
 Print usage message for options specific to each driver.
 .IP
 \fBjackd \-d alsa \-\-help\fR
 .br
 \fBjackd \-d dummy \-\-help\fR
 .br
 \fBjackd \-d portaudio \-\-help\fR
 .PP
 Run the JACK daemon with realtime priority using the first ALSA
 hardware card defined in \fB/etc/modules.conf\fR.  This must be run on
 a kernel with capabilities enabled.
 .IP 
 \fBjackstart \-\-realtime \-\-driver=alsa\fR
 .PP
 Run the JACK daemon with low latency giving verbose output, which can
 be helpful for trouble-shooting system latency problems.  A reasonably
 well-tuned current-generation system with a decent sound card and a
 low-latency kernel with capabilities enabled can handle these values
 reliably.  Some can do better.  If you get xrun messages, try a larger
 buffer.  Tuning a system for low latency is challenging.  The JACK
 FAQ, <\fBhttp://jackit.sourceforge.net/docs/faq.php\fR> has some
 useful suggestions.
 .IP 
 \fBjackstart \-Rv \-d alsa \-p 128 \-n 3 \-r 44100\fR
 .PP
 Run \fBjackd\fR with realtime priority using the "sblive" ALSA device
 defined in ~/.asoundrc.  Apply shaped dithering to playback audio.
 This must be run as root.
 .IP 
 \fBjackd \-R \-d alsa \-d sblive \-\-dither=shaped\fR
 .PP
 Run \fBjackd\fR with no special privileges using the second ALSA
 hardware card defined in \fB/etc/modules.conf\fR.  Any xruns reported
 by the ALSA driver will be ignored.  The larger buffer helps reduce
 data loss.  Rectangular dithering will be used for playback.
 .IP 
 \fBjackd \-d alsa \-d hw:1 \-p2048 \-n3 \-\-softmode \-zr\fR
 .SH SEE ALSO:
 .br
 <\fBjackit-devel@lists.sourceforge.net\fR>
 .br 
 <\fBhttp://www.alsa-project.org\fR>
 .SH BUGS
 Please report bugs to
 .br
 <\fBhttp://jackit.sourceforge.net/mantis/main_page.php\fR>
 .SH AUTHORS
 Paul Davis and others.
 .PP
 Manpage originally written by Stefan Schwandter
 <e9925373@student.tuwien.ac.at>, later adapted by Jack O'Quin
 <joq@joq.us>.