jack1/jackd/jackd.1.in

.TH "JACKD" "1" "@VERSION@" "April 2006" ""
.SH "NAME"
jackd, jackstart \- JACK Audio Connection Kit sound server
.SH "SYNOPSYS"
\fBjackd\fR [\fIoptions\fR] \fB\-d\fI backend \fR 
[\fIbackend\-parameters\fR]
.br
\fBjackstart\fR [\fIoptions\fR] \fB\-d\fI backend \fR 
[\fIbackend\-parameters\fR]
.br
\fBjackd \-\-help\fR
.SH "DESCRIPTION"
\fBjackd\fR invokes the JACK audio server daemon.  The \fBjackstart\fR
command provides JACK's built\-in support for Linux 2.4.x kernels with
the realtime capabilities patch.  Use \fBjackd\fR for Linux 2.6.x and
all other systems.  All parameters are the same.

JACK is 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 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 \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://www.jackaudio.org\fR>.
.SH "OPTIONS"
.TP
\fB\-d, \-\-driver \fIbackend\fR [\fIbackend\-parameters\fR ]
.br
Select the audio interface backend.  The current list of supported
backends is: \fBalsa\fR, \fBcoreaudio\fR, \fBdummy\fR, \fBfreebob\fR,
\fBoss\fR and \fBportaudio\fR.  They are not all available on all
platforms.  All \fIbackend\-parameters\fR are optional.

.TP
\fB\-h, \-\-help\fR
.br
Print a brief usage message describing the main \fBjackd\fR options.
These do not include \fIbackend\-parameters\fR, which are listed using
the \fB\-\-help\fR option for each specific backend.  Examples below
show how to list them.
.TP
\fB\-m, \-\-no\-mlock\fR
Do not attempt to lock memory, even if \fB\-\-realtime\fR.
.TP
\fB\-n, \-\-name\fR \fIserver\-name\fR
Name this \fBjackd\fR instance \fIserver\-name\fR.  If unspecified,
this name comes from the \fB$JACK_DEFAULT_SERVER\fR environment
variable.  It will be "default" if that is not defined.
.TP
\fB\-p, \-\-port\-max \fI n\fR
Set the maximum number of ports the JACK server can manage.  
The default value is 128.
.TP
\fB\-R, \-\-realtime\fR 
.br
Use realtime scheduling.  This is needed for reliable low\-latency
performance.  On most systems, it requires \fBjackd\fR to run with
special scheduler and memory allocation privileges, which may be
obtained in several ways.  The simplest, and least-secure method is to
run \fBjackd\fR with root privileges.  This means that all JACK
clients must also run as root.  With a Linux 2.6 kernel, ordinary
users can run \fBjackd\fR and its clients using options of the
realtime LSM.  Linux 2.4 kernels need "POSIX draft capabilities"
enabled (see the \fB<linux/capability.h>\fR include file).  Using that
method, ordinary users who invoke the daemon using \fBjackstart\fR,
can later launch JACK clients without running them as root.  See
.I http://jackit.sourceforge.net/docs/faq.php#a52 
for more information.
.TP
\fB\-P, \-\-realtime\-priority \fIint\fR
When running \fB\-\-realtime\fR, set the scheduler priority to
\fIint\fR.
.TP
\fB\-\-silent\fR
Silence any output during operation.
.TP
\fB\-T, \-\-temporary\fR
Exit once all clients have closed their connections.
.TP
\fB\-t, \-\-timeout \fIint\fR
.br
Set client timeout limit in milliseconds.  The default is 500 msec
when not in realtime mode (see: \-R).
.TP
\fB\-u, \-\-unlock\fR
.br
Unlock libraries GTK+, QT, FLTK, Wine.
.TP
\fB\-v, \-\-verbose\fR
Give verbose output.
.TP
\fB\-V, \-\-version\fR
Print the current JACK version number and exit.
.SS ALSA BACKEND OPTIONS
.TP
\fB\-C, \-\-capture\fR [ \fIname\fR ]
Provide only capture ports, unless combined with \-D or \-P.  Parameterally set 
capture 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.  Defaults to on unless only one 
of \-P or \-C is specified.
.TP
\fB\-h, \-\-help\fR Print a brief usage message describing only the
\fBalsa\fR backend parameters.
.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 parameters.
.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 of playback latency.  In seconds, this
corresponds to \fB\-\-nperiods\fR times \fB\-\-period\fR divided by
\fB\-\-rate\fR.  The default is 2, the minimum allowable.  For most
devices, there is no need for any other value with the
\fB\-\-realtime\fR 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
\fB\-\-period\fR times \fB\-\-nperiods\fR frames.  Some devices demand
a larger buffer.  If so, JACK will use the smallest possible buffer
containing at least \fB\-\-nperiods\fR, but the playback latency does
not increase.
.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, unless combined with \-D or \-C.  Optionally set 
playback 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 capture 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.
.SS COREAUDIO BACKEND PARAMETERS
.TP
\fB\-c \-\-channel\fR
Maximum number of channels (default: 2)
.TP
\fB\-i \-\-channelin\fR
Maximum number of input channels (default: 2)
.TP
\fB\-o \-\-channelout\fR
Maximum number of output channels (default: 2)
.TP
\fB\-C \-\-capture\fR
Whether or not to capture (default: true)
.TP
\fB\-P \-\-playback\fR
Whether or not to playback (default: true)
.TP
\fB\-D \-\-duplex\fR
Capture and playback (default: true)
.TP
\fB\-r \-\-rate\fR
Sample rate (default: 44100)
.TP
\fB\-p \-\-period\fR
Frames per period (default: 128)
.TP
\fB\-n \-\-name\fR
Driver name (default: none)
.TP
\fB\-I \-\-id\fR
Audio Device ID (default: 0)
.SS DUMMY BACKEND PARAMETERS
.TP
\fB\-C, \-\-capture \fIint\fR
Specify number of capture ports. The default value is 2.
.TP
\fB\-P, \-\-playback \fIint\fR
Specify number of playback ports. The default value is 2.
.TP
\fB\-r, \-\-rate \fIint\fR
Specify sample rate. The default value is 48000.
.TP
\fB\-p, \-\-period \fIint\fR
Specify number of frames per period. The default value 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 capture latency in
seconds is \fB\-\-period\fR divided by \fB\-\-rate\fR.
.TP
\fB\-w, \-\-wait \fIint\fR 
Specify number of usecs to wait between engine processes. 
The default value is 21333.
.SS OSS BACKEND PARAMETERS
.TP
\fB\-r, \-\-rate \fIint\fR
Specify the sample rate.  The default is 48000.
.TP
\fB\-p, \-\-period \fIint\fR
Specify 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 capture latency in
seconds is \fB\-\-period\fR divided by \fB\-\-rate\fR.
.TP
\fB\-n, \-\-nperiods \fIint\fR
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\-w, \-\-wordlength \fIint\fR
Specify the sample size in bits. The default is 16.
.TP
\fB\-i, \-\-inchannels \fIint\fR
Specify how many channels to capture (default: 2)
.TP
\fB\-o, \-\-outchannels \fIint\fR
Specify number of playback channels (default: 2)
.TP
\fB\-C, \-\-capture \fIdevice_file\fR
Specify input device for capture (default: /dev/dsp)
.TP
\fB\-P, \-\-playback \fIdevice_file\fR
Specify output device for playback (default: /dev/dsp)
.TP
\fB\-b, \-\-ignorehwbuf \fIboolean\fR
Specify, whether to ignore hardware period size (default: false)
.SS PORTAUDIO BACKEND PARAMETERS
.TP
\fB\-c \-\-channel\fR
Maximum number of channels (default: all available hardware channels)
.TP
\fB\-i \-\-channelin\fR
Maximum number of input channels (default: all available hardware channels)
.TP
\fB\-o \-\-channelout\fR
Maximum number of output channels (default: all available hardware channels)
.TP
\fB\-C \-\-capture\fR
Whether or not to capture (default: true)
.TP
\fB\-P \-\-playback\fR
Whether or not to playback (default: true)
.TP
\fB\-D \-\-duplex\fR
Capture and playback (default: true)
.TP
\fB\-r \-\-rate\fR
Sample rate (default: 48000)
.TP
\fB\-p \-\-period\fR
Frames per period (default: 1024)
.TP
\fB\-n \-\-name\fR
Driver name (default: none)
.TP
\fB\-z \-\-dither\fR
Dithering mode (default: none)
.SH "EXAMPLES"
.PP
Print usage message for the parameters specific to each backend.
.IP
\fBjackd \-d alsa \-\-help\fR
.br
\fBjackd \-d coreaudio \-\-help\fR
.br
\fBjackd \-d dummy \-\-help\fR
.br
\fBjackd \-d freebob \-\-help\fR
.br
\fBjackd \-d oss \-\-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.
.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 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,
.I http://jackit.sourceforge.net/docs/faq.php\fR
has some useful suggestions.
.IP
\fBjackstart \-Rv \-d alsa \-p 128 \-n 2 \-r 44100\fR
.PP
Run \fBjackd\fR with realtime priority using the "sblive" ALSA device
defined in ~/.asoundrc.  Apply shaped dithering to playback audio.
.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 backend 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
.PP
Run \fBjackd\fR in full\-duplex mode using the ALSA hw:0,0 device for 
playback and the hw:0,2 device for capture.
.IP
\fBjackd \-d alsa \-P hw:0,0 \-C hw:0,2\fR
.PP
Run \fBjackd\fR in playback\-only mode using the ALSA hw:0,0 device. 
.IP
\fBjackd \-d alsa \-P hw:0,0\fR
.SH "ENVIRONMENT"
.br
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 \fB$HOME/.jackdrc\fR if it exists, or \fB/etc/jackdrc\fR if it
does not.  If neither file exists, a built\-in default command will be
used, including the \fB\-T\fR flag, which causes the server to shut
down when all clients have exited.

As a transition, this only happens when \fB$JACK_START_SERVER\fR is
defined in the environment of the calling process.  In the future this
will become normal behavior.  In either case, defining
\fB$JACK_NO_START_SERVER\fR disables this feature.

To change where JACK looks for the backend drivers, set
\fB$JACK_DRIVER_DIR\fR.

\fB$JACK_DEFAULT_SERVER\fR specifies the default server name.  If not
defined, the string "default" is used.  If set in their respective
environments, this affects \fBjackd\fR unless its \fB\-\-name\fR
parameter is set, and all JACK clients unless they pass an explicit
name to \fBjack_client_open()\fR.

.SH "SEE ALSO:"
.PP
.I http://www.jackaudio.org
.br
The official JACK website with news, docs and a list of JACK clients.
.PP
.I http://lists.sourceforge.net/mailman/listinfo/jackit\-devel
.br
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.
.PP
.I http://www.jackosx.com/
.br
Tools specific to the Mac OS X version of JACK.
.PP
.I http://www.alsa\-project.org
.br
The Advanced Linux Sound Architecture.
.SH "BUGS"
Please report bugs to
.br
.I http://jackit.sourceforge.net/mantis/main_page.php
.SH "AUTHORS"
Architect and original implementor: Paul Davis
.PP
Original design Group: Paul Davis, David Olofson, Kai Vehmanen, Benno Sennoner,
Richard Guenther, and other members of the Linux Audio Developers group.
.PP
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.
.PP
Manpage written by Stefan Schwandter, Jack O'Quin and Alexandre
Prokoudine.