Peter Gerwinski
PULT

Repository



PULT is the ULTimate Learning/Teaching Tool

Contents

 What is PULT?                         
 Okay, more technically, what is PULT? 
 How does this look like in practice?  
 Licence                               
 Installation                          


What is PULT?


PULT is a video platform for learning and teaching.
There are a lot of video systems designed for conferencing,
which are commonly used for learning and teaching.
PULT is designed for learning and teaching.


PULT is simple.
To participate in a lecture you just go to a web page, type your
password, and watch.  As a lecturer you have a few buttons to
control whether something becomes full-screen or whether someone
may contribute something.  Focus on contents, not on the tool.


PULT is reliable.
Even when the network connection isn't the best, you still get
your lecture through.


PULT is 100% Free Software (Open Source).
You can run it on your own server for best-possible data
protection and privacy.  You can study how it works, adapt
it to your needs, and publish your improvements for everyone
to benefit.  Also, there are no licencing fees.


PULT husbands your CPU power and network bandwidth.
Neither the server nor the client computers need to be high-end.
PULT can even work when the lecturer's Internet access is rather
slow.


PULT integrates your favourite platform.
We didn't reinvent the wheel. When you like Jitsi Meet and you
want to use it to show your face to 120 participants, PULT
makes that possible – in a way which makes it even simpler
for your participants than if they joined Jitsi Meet.
When you like the shared whiteboard of OpenMeetings,
PULT enables you to present it to a big audience,
where only those who actually write on the whiteboard
need to join and to understand OpenMeetings.


Okay, more technically, what is PULT?
PULT is a collection of small programs, mostly Unix shell scripts.
It provides a console (in German: „Pult“ :–) where the lecturer can
select which visual content is offered to the audience via a web
interface, noVNC.  These visual contents can be a shared desktop,
a camera view, an uploaded image or screenshot, or some arbitrary
content provided by some other tool via a web interface, for
instance a BigBlueButton presentation or the shared whiteboard of
OpenMeetings.
PULT itself only handles video.  For the audio part and the chat
part it cooperates with Mumble.
The virtual “meeting rooms” in PULT are called channels.  For each
channel, there is one instance of noVNC, showing a virtual desktop,
provided by TigerVNC, to the audience.
Each channel is controlled by a deamon, pultd, a shell script,
which loads the modules configured for this channel, also shell
scripts.  The pultd takes the role of the window manager for the
channel's virtual desktop; the modules are the application software
running on it.
For each channel, the lecturer has a web interface with a row of
buttons for each module to start and stop it, to make it full-screen,
or to take a pre-configured window in the channel.  We intentionally
don't let the lecturer drag and drop the window with the mouse.
Pressing a button is by far less distracting.
The audience has, also intentionally, no control over the contents
of the desktop.  They just view their channel via noVNC.  That way
they can concentrate on the learning content rather than on the
viewing tool.
Currently we provide the following modules:


VNC
The lecturer can share a destkop content via VNC and/or invite
participants to share theirs.
VNC provides a pixel-correct transmission of the desktop contents
at a reasonable speed, using only moderate CPU resources and
network bandwidth.
For best performance, we recommand installing a VNC server on the
lecturer's computer.  For a quick solution, we provide yesVNC,
a VNC server via a web interface.


CVH-Camera
The lecturer or a participant can place a camera view in the
channel.
One of the videos provided this way can be transmitted via
the Janus WebRTC Gateway.  This allows for a high-quality
transmission at a moderate, and adjustable, network bandwidth.
(We are working on making this possible for all camera views.)


Upload
The lecturer or a participant can upload an image file or a
screenshot via a web interface.


BBB-Camera and JM-Camera
The lecturer or a participant can transmit a camera view via
BigBlueButton or Jitsi Meet, which then becomes visible in the
channel.


OM-Board and BBB-Board
OpenMeetings and BigBlueButton provide shared whiteboards, where
the lecturer and the participants can draw and upload presentations.
This module makes these boards visible in the channel.


Each channel is easily configurable to meet the needs of the
lecturer.  One lecturer might want as few buttons as possible
(see fig. 1), while another one might prefer to have all modules
enabled, just in case (see fig. 2).
For each configured module, the lecturer's console features a row
of buttons to start and stop the module, and to hide and show its
contents.  Modules can also be configured to get an additional
button to make them run in a pre-defined region of the screen
rather than full-screen.  For camera modules this is the default.
A typical application is to run a VNC shared desktop full-screen
and to show a camera view of the lecturer at the edge.


Figure 1: A minimalistic PULT console.
VNC gets started automatically.
The buttons are for switching a camera.


Figure 2: A PULT console with many features enabled
In this configuration, the lecturer can show 2 different
shared desktops (“VNC”), 5 different camera views (“Kamera”),
2 different shared presentations or boards (“Tafel”), plus
images or screenshots uploaded by participants (“Upload”).
The green colour indicates that the video source is currently
active. The yellow colour indicates that it has been started,
but is currently waiting for a feed.
Below the buttons, the PULT console shows the URLs and other
types of information how to feed visual data into the system.
These lines remain visible as long as they are needed.


How does this look like in practice?

Students S1, S2, ... want to take part in a lecture by lecturer L.
They connect to Mumble for the audio part. For the video part, they
go to the web page of the channel, type in the channel's password,
and see a welcome screen.


The welcome screen at the Bochum University of Applied Sciences


Lecturer L goes to another specific web page, the PULT console.
L presses the buttons labeled “VNC start” and “Camera start”.
L starts the VNC server software and connects to the server.
L's shared desktop appears in the channel.  L follows a link
from the PULT console to a separate web page to activate the
camera.  The camera view becomes visible in the lower right
corner of the channel.


PULT console with VNC and Camera started


The noVNC screen shows the lecturer's shared desktop in
full-screen mode and the camera view in the lower right corner.
The lecturer's desktop features a presentation on the left.


For welcoming the students, L presses the button labeled
“Camera max“.  The camera view becomes full-screen, hiding
the shared desktop.  After the welcoming, L presses “Camera min”
to switch back to the previous screen arrangement.


The camera in full-screen view


Now L wants to explain a source code. L uses the PULT console
to switch back from camera full-screen mode to the view of the
shared desktop with the camera view in the lower right corner.
L minimises the presentation on the desktop and presents the
source code.


The same arrangement with the desktop showing a smaller view of
the presentation on the right and a source code example on the
left.


Student S1 wants to ask a question.  For this purpose, S1 needs
to upload a screenshot.  L presses the “Upload start”.  The PULT
console displays a URL.  L forwards this URL to S1 via the Mumble
chat.  S1 follows the link and presses the “Screenshot” button.
S1's screenshot appears in the channel, hiding L's desktop, but
not the camera view.


While L answers S1's question, L presses “Upload hide” to switch to
L's desktop, and later “Upload show” to switch back to S1's uploaded
screenshot.  When the question is answered, L presses “Upload stop”.
S1's screenshot vanishes, we are back to the full-screen view of L's
desktop with a camera view in the corner.


L asks the students to present some mathematical calculations.
S2 volunteers and wants to use the OpenMeetings whiteboard for
this purpose. L presses “OM board start” on the PULT console.
S2 logs into OpenMeetings and draws the mathematical calculations
for everyone to see via noVNC.


A shared OpenMeetings whiteboard presented via noVNC.
The cameraa view still shows the lecturer.


S2 wants to share a camera view as well, using Jitsi Meet.
L enables the Jitsi Meet camera view via the PULT console.
S2 logs into Jitsi Meet, and the second camera view appears
on the noVNC screen.


A shared OpenMeetings whiteboard presented via noVNC, plus
two camera views. The upper one was sent via Jitsi Meet.


After a while, S3 wants to share a desktop to discuss some results.
L presses “VNC guest start”.  Since S3 does not have a VNC server
installed, L copies a URL from the PULT console to S3 in the Mumble
chat.  S3 follows the URL and presses a button.  S3's desktop is
presented full-screen in the channel, with L's camera view in the
corner.  L decides that the camera view hides important parts of
S3's desktop, and presses “Camera hide”.  The camera view vanishes.
After the discussion, L presses “VNC Guest stop”.  S3's desktop
vanishes; L's desktop is visible again.


At the end of the lecture, L presses “Camera max” to make the
camera view full-screen to say goodbye.  L presses “Camera stop”
and “VNC stop”.  The channel shows a welcome screen again.
To end the session, everyone closes their browser windows.


Licence
PULT is Free Software (Open Source) under the
 GNU Affero General Public License (AGPL) ,
either version 3 of the licence, or, at your option, any later version.
In short this means:


You are free to run the software, for any purpose.


You are free to study how the software works and to adopt it
to your needs.
To make this possible, you have, as a user of the software,
the right to obtain its source code, even if the software
runs on a server, and you only connect to that server.
(This “even on a server” clause is what distinguishes the
GNU Affero GPL from the “normal” GNU GNU GPL.)


You are free to redistribute copies of this software,
gratis or for a fee, provided that you don't deny
anyone the rights we gave to you.
(This “provided that” clause is the Copyleft
principle, an essential feature of the GNU licences.)


You are free to improve this software and to redistribute
your improvements, so everyone can benefit from them.
Again, you may do this as a charity service, but you are also
free to found a business providing this kind of service.


There is NO WARRANTY, unless you are paying someone
to provide a warranty for you.


The GNU AGPL applies to PULT itself.  Many components used by PULT
are under different licences.  However they are all Free Software,
and their licence conditions are essentially subsets of those of
the GNU AGPL.
A simplified list of the individual licences follows.
For details, please examine the individual software packages.


Mumble (server and client): 3-clause BSD licence


Mumble web interface mumble-web: ISC licence


Web server: nginx: 2-clause BSD licence,
or Apache: Apache licence 2.0


noVNC: MPL 2.0


yesVNC: GNU APGL 3+ (part of PULT)


websockify: GNU GPL 3


TigerVNC: GNU GPL 2.0


TightVNC: GNU GPL 2.0+


x11vnc: GNU GPL 2.0


ssvnc: GNU GPL 2.0


OpenSSH: 3-clause BSD licence


PuTTY: MIT/Expat licence


Janus WebRTC Gateway: GNU GPL 3


Firefox web browser and geckodriver: MPL 2.0


Chromium web browser and chromedriver: 3-clause BSD licence


Selenium: Apache licence 2.0


Python: PSF licence


Node.js: MIT/Expat licence


Netcat: 3-clause BSD licence


Bash: GNU GPL 3+


botamusique: MIT/Expat licence


For an overview about the licences themselves, see
 https://www.gnu.org/licenses/license-list.html .

Installation
Detailed installation instructions ar being written right now.
We are also planning to provide a ready-to-run PULT installation
as a Docker container. That way you can install it in just a few
minutes.
This section gives a brief overview.
The PULT server was desiged to run on GNU/Linux.  However it should
not be difficult to make it run on other Unix-like systems.
PULT consists of several parts to be installed separately.  You can
choose which ones you want to use.  Most of them make use of other
software which is well-established and probably included in your
GNU/Linux distribution for easy installation.


Mumble
PULT itself only handles video.  For a useful system you need
something which handles the audio part.  We highly recommend
Mumble for its stability and quality.  Mumble also provides a
chat function which has proven very useful.
PULT comes with some utilites which are designed to cooperate
with Mumble.
For the audience, the most efficient way to participate in Mumble
is to install a Mumble client.  If you want to provide an easier,
albeit less efficient access method, you can install mumble-web,
a web interface for Mumble.
The Mumble server (Murmur) is included in many GNU/Linux
distributions.  The Mumble client (for the audience) for
vaious platforms can be downloaded from
 https://www.mumble.com/ .
The Mumble web interface is available at
 https://github.com/Johni0702/mumble-web .


VNC
Almost everything the audience can watch is conveyed via noVNC.
For sharing a desktop via VNC, the most efficient way is to
install a VNC server on the lecturer's computer.  If you want
to provide an easier, albeit less efficient method, you can
install yesVNC, a web interface for VNC, developed as part of
PULT.
The VNC server and client software, including the noVNC web
interface, is included in many GNU/Linux distributions.
Lecturers who want to install a VNC server can use TightVNC,
 https://tightvnc.com/download.php .
Lecturers who want to use an SSH tunnel but cannot easily use
OpenSSH, can use PuTTY, available at
 https://www.chiark.greenend.org.uk/~sgtatham/putty/ .


PULT Itself
PULT itself is a collection of small programs, mostly shell
scripts, to control everything.  This includes start/stop scripts
for systemd, HTML files, CGI scripts for web interfaces, and
configuration templates for your web server (Apache or nginx).
There is a shell script, pult-install, in the same directory as
this file.  When you run it with root privileges, it will copy
the files which make up PULT to their directories and give them
appropriate permissions.  However, this script is incomplete,
leaving important tasks such as creating user accounts and
enabling systemd services as manual tasks.


CVH-Camera
We have developed a native camera subsystem for PULT, CVH-Camera.
It provides a simple web interface to share a camera view and
uses the Janus WebRTC gateway to distribute it to the audience.
That way, CVH-Camera provides high quality at a reasonably low
consumption of CPU power and network bandwidth.
CVH-Camera is available at
 https://gitlab.cvh-server.de/sdoering/cvh-camera .
Parts of it are included in the PULT sources and get installed
via the pult-install shell script.


Browser-Based Video Contents
PULT can use Selenium, Python, and the web browsers Chromium and
Firefox for accessing web contents provided by other systems.
In particular, PULT can extract a camera view out of an external
Jitsi Meet or BigBlueButton, as an alternative to CVH-Camera.
The browser method requires more CPU power and network bandwidth
at a lower quality, but it provides the same level of reliability
as CVH-Camera.
The required software, Selenium, Python, Chromium, ChromeDriver,
and Firefox, is included in most GNU/Linux distributions.
One additional  component, GecokDriver, can be downloaded from
 https://github.com/mozilla/geckodriver/releases .


External Conference Systems
If you want to use a shared whiteboard, we recommend to
install OpenMeetings and to import its whiteboard into
PULT as a browser-based content (see above).  The same
is possible for BigBlueButton.
It is straightforward to import contents from other external
systems.  Just copy and modify one of the existing modules,
for instance bbb-camera.


Other Useful Tools
We also provide CVH-Bot, a bot which joins the Mumble chat and
makes it easy to conduct polls.  CVH-Bot is available at
 https://gitlab.cvh-server.de/jvongehr/cvh-bot .
Speaking of Mumble bots, we can recommend botamusique for
playing music in Mumble – for your events, for fun and for
testing purposes.  You can find botamusique at
 https://github.com/azlux/botamusique .
At the Bochum University of Applied Sciences, we provide a web
page which allows for quick access to a virtual room, i.e.
a combination of a Mumble channel and a VNC channel in PULT,
see the subdirectory www/virtual-rooms/ of the PULT sources.
Be welcome to copy it and to adapt it to your room structure.


Viel Erfolg und viel Spaß!

Have success and enjoy!