The Digital Lecture Board

A Teaching and Learning Tool for 
Synchronous, Collaborative, Remote Instruction
© 1998  University of Mannheim
LS Praktische Informatik IV
L 15, 16
D-68161 Mannheim

 

Installation

Setup

Type setup to start installation. The setup tool creates a  .dlbrc directory in your home directory and copies configuration files and files needed during runtime to this directory. If not available, a new .rtpDefaults file is created. Moreover, setup installs an sdr2 plugin if sdr is available.
 

Environment

The dlb supports two different ways of displaying postscript. You may either import postscript slides as images by using the built-in ImageMagick (tm) library or you can use gs for direct rendering inot dlb's workspace, which is much faster. In order to use the direct postscript rendering facility, you will need to have a newer version of gs installed on your system. It is important that your PATH contains the location of gs.

Add the path of the binary location of the dlb files to your PATH variable as well as the current local directory (.). Otherwise, sdr won't  recognize the dlb plugin and the dlb won't find smp and pssplit.
 

Starting the dlb

The digital lecture board can be used either in unicast or multicast mode. Select a multicast or unicast address and a port number. Then start the dlb as follows:

1. Just type  "dlb ip/port" in the dlb directory. The reliable multicast protocol smp is launched automatically with a default port. When finishing the dlb, smp is also automatically killed

2. Type    smp& once. Smp runs now in the background and can be reused several times. Then type   "dlb -a 0 ip/port"   to start the digital lecture board.

You may also want to use the dlb with the MBone session directory sdr. Please copy the sdr2.plugin.S22.whiteboard.udp.dlb.dlb plugin file to the  ~/.sdr/plugin  directory in your home directory. Make sure your PATH variable contains a path tp the dlb binaries otherwise sdr won't install the plugin. Note: If sdr is installed, the dlb setup tool automatically copies the plugin file to the plugin directory.

If you don't specify a destination address, dlb uses default values. The following further
 

Command line options

usage: dlb [-l {0,1}] [-a {0,1}] [-e{0,1}] [-p smpport] [-t ttl] [dest/port]

-l {0,1}           disable/enable late join (defaults to 1)
-a {0,1}         disable/enable automatic start-up of smp (defaults to 1)
-e {0,1}         disable/enable encryption on startup (defaults to 0)
-p smpport    set port number for the connection to the reliable multicast protocol smp (defaults to 5000)
-t   ttl              set time-to-live to ttl  (defaults to 16)
dest/port         set destination ip address and destination port  (defaults to 224.2.141.55/32460)

Example:   dlb -a 0 -p 6789 -t 63 224.2.3.4/50000

In this example, you need smp listening at port number 6789 prior to start the dlb.  To start smp with a different port, type:

smp -p 6789

You may also wish to disable the multicast loopback option of smp. To disable multicast loopback, use the -l command line option of smp:

-l {0,1}           disable/enable multicast loopback
 

Using the digital lecture board

Check our brief user guide available through dlb's user interface or the help file included in the package.

Known limitations and bugs

The grouping features does not work properly when scaling images.

Your help in improving this software is very much appreciated. Please send detailed bug reports to Werner Geyer (geyer@pi4.informatik.uni-mannheim.de).
 

Disclaimer

Permission to use, copy, and distribute this software and its documentation for any purpose and without fee is hereby granted. We make no representations about the suitability of this software for any purpose.  This Software is provided by the University of Mannheim and contributors  ``AS IS'' and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall the University of Mannheim or contributors be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage.