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.TH JACKD "1" @VERSION@ "March 2003" |
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.SH NAME |
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jackd, jackstart \- JACK Audio Connection Kit sound server |
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.SH SYNOPSYS |
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\fBjackd\fR [ \fI options \fR ] \fB \-d \fI driver \fR |
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[\fI driver options \fR ] |
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.br |
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\fBjackstart\fR [ \fI options \fR ] \fB \-d \fI driver \fR |
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[\fI driver options \fR ] |
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.br |
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\fBjackd \-\-help\fR |
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.SH DESCRIPTION |
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\fBjackd\fR invokes the JACK audio server daemon. When using JACK's |
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built-in support for realtime capabilities, use the \fBjackstart\fR |
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command, instead. All options are the same. |
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JACK is a low-latency audio server, originally written for the |
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GNU/Linux operating system. It can connect a number of different JACK |
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client applications to an audio device, and also to each other. Most |
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clients are external, running in their own processes as normal |
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applications. JACK also supports internal clients, which run within |
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the \fBjackd\fR process using a loadable "plugin" interface. |
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JACK differs from other audio servers in being designed from the |
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ground up for professional audio work. It focuses on two key areas: |
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synchronous execution of all clients, and low latency operation. |
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For the latest JACK information, please consult the web site, |
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<\fBhttp://jackit.sourceforge.net\fR>. |
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.SH OPTIONS |
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.TP |
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\fB\-h, \-\-help\fR |
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.br |
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Print a brief usage message describing the main \fBjackd\fR options. |
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These do not include driver options, which are obtained using the |
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\fB\-\-help\fR option for that specific driver, instead. |
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.TP |
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\fB\-a, \-\-asio\fR |
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.br |
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Force absolute realtime behaviour on the system. Rather than allowing |
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clients to take a time determined by the kernel, they are determined |
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to have timed out on receipt of the next interrupt from the audio |
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interface. This only makes sense when used with an ASIO-style |
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configuration where there are 2 periods per buffer (see |
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\fB\-\-nperiods\fR). It is safe to omit this parameter, if you don't |
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need to enforce strict realtime limits. |
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.TP |
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\fB\-R, \-\-realtime\fR |
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.br |
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Use realtime scheduling. This is needed for reliable low-latency |
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performance. It requires \fBjackd\fR to run with special scheduler |
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and memory allocation privileges, which may be obtained in two ways. |
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The first method is to run \fBjackd\fR with root privileges, which |
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means that all JACK clients must also run as root. The second method |
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requires a kernel with "POSIX draft capabilities" enabled (see the |
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\fB<linux/capability.h>\fR include file). Then, an ordinary user can |
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invoke the daemon using \fBjackstart\fR, and later launch JACK clients |
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without running as root. |
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.TP |
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\fB\-P, \-\-realtime\-priority \fIint\fR |
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When running \fB\-\-realtime\fR, set the scheduler priority to |
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\fIint\fR. |
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.TP |
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\fB\-D, \-\-tmpdir \fIdirectory\fR |
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Set the \fIdirectory\fR to use for temporary files. |
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.TP |
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\fB\-v, \-\-verbose\fR |
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Give verbose output. |
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.TP |
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\fB\-V, \-\-version\fR |
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Print the current JACK version number and exit. |
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.TP |
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\fB\-d, \-\-driver \fI driver \fR [ \fI driver-options \fR ] |
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.br |
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Select the output driver. The only \fIdriver\fR currently documented |
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is \fBalsa\fR (see below). |
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.SS ALSA DRIVER OPTIONS |
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.TP |
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\fB\-h, \-\-help\fR Print a brief usage message describing only the |
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\fBalsa\fR driver options. |
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.TP |
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\fB\-d, \-\-device \fIname\fR |
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.br |
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The ALSA pcm device \fIname\fR to use ("default" if none specified). |
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.TP |
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\fB\-r, \-\-rate \fIint\fR |
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Specify the sample rate. The default is 48000. |
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.TP |
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\fB\-p, \-\-period \fIint\fR |
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.br |
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Specify the number of frames between JACK \fBprocess()\fR calls. The |
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default is 1024. If you need low latency, set \fB\-p\fR as low as you |
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can go without seeing xruns. A larger period size yields higher |
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latency, but makes xruns less likely. |
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.TP |
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\fB\-n, \-\-nperiods \fIint\fR |
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.br |
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Specify the number of periods in the hardware buffer. The default is |
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2. The period size (\fB\-p\fR) times \fB\-\-nperiods\fR times four is |
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the JACK buffer size in bytes. |
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.TP |
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\fB\-D, \-\-duplex\fR |
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Provide both capture and playback ports (the default). |
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.TP |
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\fB\-C, \-\-capture\fR |
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Provide only capture ports. |
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.TP |
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\fB\-P, \-\-playback\fR |
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Provide only playback ports. |
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.TP |
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\fB\-H, \-\-hwmon\fR |
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.br |
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Enable hardware monitoring of capture ports. This is a method for |
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obtaining "zero latency" monitoring of audio input. It requires |
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support in hardware and from the underlying ALSA device driver. |
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When enabled, requests to monitor capture ports will be satisfied by |
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creating a direct signal path between audio interface input and output |
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connectors, with no processing by the host computer at all. This |
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offers the lowest possible latency for the monitored signal. |
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Presently (March 2003), only the RME Hammerfall series and cards based |
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on the ICE1712 chipset (M-Audio Delta series, Terratec, and others) |
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support \fB\-\-hwmon\fR. In the future, some consumer cards may also |
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be supported by modifying their mixer settings. |
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Without \fB\-\-hwmon\fR, port monitoring requires JACK to read audio |
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into system memory, then copy it back out to the hardware again, |
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imposing the basic JACK system latency determined by the |
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\fB\-\-period\fR and \fB\-\-nperiods\fR options. |
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.TP |
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\fB\-s, \-\-softmode\fR |
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.br |
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Ignore xruns reported by the ALSA driver. This makes JACK less likely |
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to disconnect unresponsive ports when running without |
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\fB\-\-realtime\fR. |
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.TP |
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\fB\-z, --dither [rectangular,triangular,shaped,-] |
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Set dithering mode. If \fB\-\fR or unspecified, dithering is off. |
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Only the first letter of the mode name is required. |
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.SH EXAMPLES |
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.PP |
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Print usage message for options specific to the \fBalsa\fR driver. |
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.IP |
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\fBjackd \-d alsa \-\-help\fR |
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.PP |
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Run the JACK daemon with realtime priority using the first ALSA |
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hardware card defined in \fB/etc/modules.conf\fR. This must be run on |
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a kernel with capabilities enabled. |
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.IP |
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\fBjackstart \-\-realtime \-\-driver=alsa \-\-device=hw:0\fR |
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.PP |
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Run the JACK daemon with low latency. A reasonably well-tuned |
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current-generation system with a decent sound card and a low-latency |
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kernel with capabilities enabled can handle these values reliably. |
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Some can do better. If you get xrun messages, try a larger buffer. |
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Tuning a system for low latency is challenging. The JACK FAQ, |
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<\fBhttp://jackit.sourceforge.net/docs/faq.php\fR> has some useful |
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suggestions. |
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.IP |
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\fBjackstart \-R \-d alsa \-d hw:0 \-p 128 \-n 3 \-r 44100\fR |
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.PP |
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Run \fBjackd\fR with realtime priority using the "sblive" ALSA device |
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defined in ~/.asoundrc. Apply shaped dithering to playback audio. |
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This must be run as root. |
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.IP |
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\fBjackd \-R \-d alsa \-d sblive \-\-dither=shaped\fR |
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.PP |
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Run \fBjackd\fR with no special privileges using the "sblive" ALSA |
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device defined in ~/.asoundrc. Any xruns reported by the ALSA driver |
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will be ignored. The larger buffer helps reduce data loss. |
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Rectangular dithering will be used for playback. |
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.IP |
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\fBjackd \-d alsa \-d sblive \-p1024 \-n3 \-\-softmode \-zr\fR |
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.SH SEE ALSO: |
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.BR <\fBhttp://www.alsa-project.org\fR> |
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.SH BUGS |
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Please send bug reports to <\fBjackit-devel@lists.sourceforge.net\fR>. |
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.SH AUTHORS |
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Paul Davis and others. |
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.PP |
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Manpage originally written by Stefan Schwandter |
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<e9925373@student.tuwien.ac.at> and later adapted by Jack O'Quin |
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<joq@joq.us>. |
trutkin
21 years ago