The digital lecture board

© 1998 LS Praktische Informatik IV
University of Mannheim

Using dlb-1.8

Starting the dlb

Command Line Options

Usage Modes

Drawing Modes

Page Selector

Participant Information


Keyboard and Mouse Bindings

About the dlb project

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". 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.

NOTICE: You need to set and export a DLB_HOME environment variable to the dlb installation directory in order to start the dlb. Also, the location of the dlb binaries has to be appended to your PATH variable.

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 from the distribution directory to the  ~/.sdr/plugin  directory in your home directory. Make sure your PATH variable contains a path to 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 are supported:

Command Line Options
dlb [-l {0,1}] [-a {0,1}] [-e{0,1}] [-p smpport] [-t ttl] [dest/port]

-l {0,1}           disable/enable late join
-a {0,1}         disable/enable automatic start-up of smp 
-e {0,1}         disable/enable encryption on startup
-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

Example:   dlb -a 0 -p 6789 -t 63

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

Usage Modes
The dlb supports different usage modes. Besides  the default mode (on-line), one can choose between off-line or annotation mode or combinations of those. Furthermore, you can enable or disable a telepointer.

  Click on this button to toggle between on-line and off-line mode. In the on-line mode, any dlb operation (drawing, creating pages etc.) is transmitted to the multicast group. In off-line mode, operations are only performed locally. This provides you with a private workspace. If you toggle back to on-line mode, the outcome of your private work can be transmitted to the group. Saving dlb documents includes public and private operations.

  Click on this button to enable/disable annotation mode. An annotation can be any graphical operation except images and page operations. Annotations are never transmitted to the group. Saving dlb documents includes annotations.

  Click on this button to enable/disable a telepointer which is a pointing device that can be seen by the whole group. The Tools menu provides you with further settings for this mode.

Drawing Modes
  Select items by mouse click or dragging. Selected items can be resized (if supported), grouped, raised, lowered, deleted, etc.

  Quick copy mode. Click on an item and drag mouse to copy the item. No select required.

  Quick delete mode. Click on an item to delete it. No select required.

  Insert and edit text item.

  Insert freehand line.

  Insert poly line. Terminate polyline by double clicking the left mouse button.

  Insert line.

  Insert arrow.

  Insert horizontal line.

  Insert vertical line.

   Insert filled rectangle. Hold the shift key pressed while dragging in order to get a square.

  Insert outlined rectangle. Hold the shift key pressed while dragging in order to get a square.

  Insert filled oval. Hold the shift key pressed while dragging in order to get a circle.

  Insert outlined oval. Hold the shift key pressed while dragging in order to get a circle.

  Insert a point (small filled circle).

  Insert filled polygon. Terminate polygon by double clicking the left mouse button.

  Insert outlined polygon. Terminate polygon by double clicking the left mouse button.

Page Selector

The page selector provides you with access to private and public pages by either clicking on the pages or by using the arrow buttons to browse through the pages. Pages of remote sites are marked with the canonical name (CNAME) behind. Page names can be changed by double clicking on the name. The most left button creates new blank pages. Furthermore, the page selector gives you access to the different usage modes of the dlb as described above. If you are working in the off-line mode (see left screen shot), private pages are created in a separate listbox below the listbox with the public (global) pages. When switching back to on-line mode, private pages can be transmitted to the group by clicking on the pages. The page selector can be hidden using the View menu.

The page info field below the drawing area displays information about the current page and zoom factor. The arrow buttons allow to change pages locally. The middle button switches back to the current global page.

Participant Information
The participant info displays a list of all participants currently joining the session. The information is based on RTCP protocol information. Clicking on single participants brings you more information. The data of the local participant can be modified. The participant information can be hidden by using the View menu.


Open ...
Save As ...

Open Pages ...
Save Pages
Open Selection ...
Save Selection ...

Open an existing dlb document 
Save current dlb document 
Save dlb document using a 
different name 
Open dlb pages 
Save selected pages 
Open a dlb selection 
Save selected items 
Exit dlb


Select All
New Page
Clear Page
Undo last operation 
Cut selected items to the clipboard 
Paste items from the clipboard 
Copy selected items to the clipboard 
Delete selected items 
Select all items on current page 
Create a new blank page 
Clear current page 
Group selected items 
Ungroup selected items


Image Orientation

Freeze Images

Use PS direct



Smooth Lines

Change orientation of images and 
ps slides
Freeze position of images/postscript 
Enable/disable direct postscript display 
when loading dlb documents which 
contain postscript
Change the zoom factor of the complete document 
Show/Hide certain control panels and 
Enable/disable snap to grid 
Enable/disable freehand line smoothing


Image ...
Text ...
Window ...

PS direct ...

Insert image (gif, pcx, ps, eps etc.) 
Insert ascii text
Insert the contents of an X window into
the shared workspace of the dlb 
Insert Postscript (uses gs for direct 
display) into the shared workspace, 
faster than Image ...)


Telepointer ...
Voting ...
Online Feedback ...

Attention ...
Chat ...

Insert/Change Telepointer 
Raise/Enable/Configure Voting facility
Raise/Enable/Configure Online 
Feedback facility
Raise/Enable Attention tool
Raise/Enable/Configure Chat Window


Middle Mouse
Right Mouse

Draw Width
Draw Color
Background Color

Font Type
Font Size
Font Style
Security ...

Snap ...

Save ...

Save Settings

Configure middle mouse button 
Configure right mouse button 
(uses per default a quick access menu)
Change draw width 
Change draw color 
Change background color of current
and future pages 
Change font type 
Change font size 
Change font style 
Set security options (enable/disable, 
user-profile, customize security, 
passphrase etc.) 
Change Snap settings (grid and snap 
Change save settings (currently only a 
renaming of pages is supported) 
Save current dlb settings
Help About ...
Usage ...
Display author and copyright information
Display this user guide by calling a 
web browser
Keyboard & Mouse Bindings
  • Left mouse button: choose drawing modes for left mouse button
  • Middle mouse button: can be configured in the Options menu (defaults to the select mode)
  • Right mouse button: can be configured in the Options menu (defaults to the quick access menu)

  • Ctrl-X                   Cut selected items to clipboard
  • Ctrl-Delete         Cut selected items to clipboard
  • Ctrl-d                    Delete selected items
  • Ctrl-a                    Select all items on current page
  • Ctrl-c                    Copy selected items to clipboard
  • Ctrl-v                    Paste clipboard items
  • Shift-Insert         Paste clipboard items
  • Shift pressed in rectangle or oval drawing mode produces squares or circles
  • Shift pressed in select mode extends the current selection
  • Shift pressed while scaling images, rectangles, ovals, lines keeps original width/length ratio
  • Page Up                 switch to previous page
  • Page down            switch to next page
    © 1998 Werner Geyer