Video Conferencing

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VIDEO CONFERENCING

Presented by:
A.M.Vignesh
“This new world of geographical togetherness has been brought about,
to a great extent, by man's scientific and technological genius. Man has
been able to dwarf distance, place time in chains and carve highways
through the stratosphere. Through our scientific genius, we have made
the world a neighborhood…”
-Martin Luther King, Jr., December, 1956

Introduction:
When people from different locations wish to conduct a meeting, Video
Conference facility provides a virtual feel as if all participants were physically there in
one room. Through Video Conference people from any where can join in the meeting
electronically. They can see each other, converse with each other, share power point
presentations, share documents during the meeting, and have access to white board
facility to aid the presenter to clarify any doubts the participants may have. Video
conferencing feature permits exchange of Video and Audio between the participants in
One-to-Many configuration. All participants can see the video image of the Presenter
alongside his own (local) video.
Videoconferencing is an interactive method of communication. It can substitute for
the actual physical presence of remote participants. This reduces travel costs as well as
travel time and makes meeting attendance more convenient. Videoconferencing provides
remote participants with much of the face-to-face familiarity that comes with physical
presence.
Video conferencing in its most basic form is the transmission of image and speech,
back and forth between two or more physically separate locations (Imagine a telephone
call where you can see the speaker or a television through which you can talk). Two-way
can be just sound or sound and images (moving images). Cameras simultaneously swap
live pictures between the TV screens in each location. Cameras can be set to show the
whole room zoom in on one person or focus on a whiteboard/overhead projector or a
special document camera can be set up to send shots of papers, graphs or overheads. You
can view pictures you are sending at the same time using the picture in picture function
on the screen. Videotaping of the entire meeting is also available if taping is required.
Three or more locations can be connected using multi point Videoconferencing.
These possibilities offer new opportunities for schools and adult education
institutions, especially in the field of international contacts and distance learning.

At this stage videoconferencing is mostly used in higher education and for
distance learning. The medium offers however also a lot opportunities for adult
education, particularly when they are involved in international partnerships.
Until now videoconferencing is sometimes considered to be rather impractical
because of high costs for hardware and communication, the limited quality of the images,
a reduced contact with the audience in the remote locations(s) and the technical threshold
for the user. However the hardware costs are dropping rapidly and the compression
techniques are getting better. The user friendliness of the system is also increasing and the
evolutions in the transmission of data (e.g. ISDN standard, IP) and the bandwidth of
carriers are very promising for the future. In the light of these evolutions adult education
institutions might reconsider the use of videoconferencing.
Pedagogically, a videoconferencing session should only be undertaken if there is
an underpinning educational reason for doing so. Educators should not be driven by the
excitement of the technology and the fact that communication in vision and sound can
actually take place electronically. Where there is no plan, no content and a thin
understanding of the technology there will be little benefit to staff and student alike.
Videoconferencing is expensive and most institutions are not in a position for
buying such a system. Therefore it can be useful to find out whether or not there are
institutions in your region (colleges, universities, private companies) with a
videoconference system and willing to let you use it for a fair price.

History:
Simple analog videoconferences could be established as early as the invention of
the television. Such videoconferencing systems usually consisted of two closed-circuit
television systems connected via coax cable or radio. An example of that was the German
Reich Postzentralamt (Post Office) network set up in Berlin and several other cities from
1936 to 1940.

During

the

first

manned space

flights, NASA used

two

radiofrequency

(UHF or VHF) links, one in each direction. TV channels routinely use this kind of
videoconferencing when reporting from distant locations, for instance. Then mobile links
to satellites using specially equipped trucks became rather common.
This technique was very expensive, though, and could not be used for applications
such as telemedicine, distance education, and business meetings. Attempts at using
normal telephony networks to transmit slow-scan video, such as the first systems
developed by AT&T, failed mostly due to the poor picture quality and the lack of
efficient video compression techniques. The greater 1 MHz bandwidth and 6 Mbit/s bit
rate of Picture-phone in the 1970s also did not cause the service to prosper.
It was only in the 1980’s that digital telephony transmission networks became
possible, such as ISDN, assuring a minimum bit rate (usually 128 kilobits/s) for
compressed video and audio transmission. During this time, there was also research into
other forms of digital video and audio communication. Many of these technologies, such
as the Media space, are not as widely used today as videoconferencing but were still an
important area of research. The first dedicated systems started to appear in the market as
ISDN networks were expanding throughout the world. One of the first commercial
Videoconferencing systems sold to companies came from Picture-Tel Corp., which had
an Initial Public Offering in November, 1984.
From 1984 to 1989, Concept Communication, Inc. of the United States replaced
the then 100 pound, US$100,000 computers necessary for teleconferencing with a
patented, $12,000 circuit board which doubled the video frame rate from 15 frames per
second to 30 frames per second, and which was reduced in size to a circuit board that fit
into standard personal computers. The company's founder, William J. Tobin also secured
a patent for a codec for full-motion videoconferencing, first demonstrated at AT&T Bell
Labs in 1986.

Videoconferencing systems throughout the 1990s rapidly evolved from very
expensive proprietary equipment, software and network requirements to standards based
technology that is readily available to the general public at a reasonable cost.
Finally, in the 1990’s, IP (Internet Protocol) based videoconferencing became
possible, and more efficient video compression technologies were developed, permitting
desktop, or personal computer (PC)-based videoconferencing. In 1992 CU-SeeMe was
developed at Cornell by Tim Dorcey et al. In 1995 the First public videoconference and
peace cast between the continents of North America and Africa took place, linking a
techno fair in San Francisco with a techno-rave and cyberdeli in Cape Town. At
the Winter Olympics opening ceremony in Nagano, Japan, Seiji Ozawa conducted
the Ode to Joy from Beethoven's Ninth Symphony simultaneously across five continents
in near-real time.
While videoconferencing technology was initially used primarily within internal
corporate communication networks, one of the first community service usages of the
technology started in 1992 through a unique partnership with Picture-Tel and IBM
Corporations which at the time were promoting a jointly developed desktop based
videoconferencing product known as the PCS/1. Over the next 15 years, Project
DIANE(Diversified Information and Assistance Network) grew to utilize a variety of
videoconferencing platforms to create a multistate cooperative public service and
distance education network consisting of several hundred schools, neighborhood centers,
libraries, science museums, zoos and parks, public assistance centers, and other
community oriented organizations.
In the 2000’s, video telephony was popularized via free Internet services such
as Skype and iChat, web plugins and on-line telecommunication programs which
promoted low cost, albeit low-quality, video conferencing to virtually every location with
an Internet connection.
In May 2005, the first high definition video conferencing systems, produced
by Life Size Communications, were displayed at the Interpol trade show in Las

Vegas, Nevada, able to provide 30 frames per second at a 1280 by 720 display
resolution. Polycom introduced its first high definition video conferencing system to the
market in 2006. Currently, high definition resolution has now become a standard feature,
with most major suppliers in the videoconferencing market offering it.
Recent technological developments by Librestream have extended the capabilities
of video conferencing systems beyond the boardroom for use with hand-held mobile
devices that combine the use of video, audio and on-screen drawing capabilities
broadcasting in real-time over secure networks, independent of location. Mobile
collaboration systems allow multiple people in previously unreachable locations, such as
workers on an off-shore oil rig, the ability to view and discuss issues with colleagues
thousands of miles away.

Standards:
The International Telecommunications Union (ITU) (formerly: Consultative
Committee on International Telegraphy and Telephony (CCITT)) has some of standards
for videoconferencing.

Figure: The Tandberg E20 is an example of a SIP-only device. Such devices need to route
calls through a Video Communication Server to be able to reach H.323 systems, a process
known as "interworking".






H.310 – Broadband over Asynchronous Transfer Mode (ATM) networks.
H.320 – Narrowband over Integrated Services Digital Network (N-ISDN).
H.321 – Videoconferencing using ATM connections.
H.322 –Narrowband over LANs (Local Area Networks) that provide

Guaranteed Quality of Service (QoS), an improved method of Internet Protocol (IP)
transmission.

H.323 – Narrowband over Packet Based Networks (IP), that do not provide
guaranteed QoS.

H.324 –Very narrow bandwidth over the existing General Switched
Telephone Network (GSTN).

SIP – Multimedia multicast transmissions over IP – Currently used more in
Voice over IP transmissions, but slowly moving into the videoconferencing world.

H.264 SVC (Scalable Video Coding)
ITU H.320 is known as the standard for public switched telephone networks
(PSTN) or videoconferencing over integrated services digital networks. While still
prevalent in Europe, ISDN was never widely adopted in the United States of America and
Canada.
H.264 SVC is a compression standard that enables video conferencing systems to
achieve highly error resilient IP video transmission over the public Internet without
quality of service enhanced lines. This standard has enabled wide scale deployment of
high definition desktop video conferencing and made possible new architectures which
reduce latency between transmitting source and receiver, resulting in fluid
communication without pauses.
In addition, an attractive factor for IP videoconferencing is that it is easier to setup for use with a live videoconferencing call along with web conferencing for use in data
collaboration.

These

combined

technologies

enable

users

to

have

a

much

richer multimedia environment for live meetings, collaboration and presentations.
ITU V.80 Videoconferencing is generally compactable with H.324 standard pointto-point video telephony over regular phone lines.

Four basic types of endpoints:


Room systems



Desktop systems



Software-based systems



Tele-presence Systems

Room Systems:


All come with an intuitive GUI Interface



Almost all use remote controls or some other external interface



Most have one or more external microphone



Most hide the “administrative” features from the end user
–Many will password protect the administrative interface to avoid

users changing settings

Room Systems Examples:
 Polycom
– VSX line
– HDX line
 Tandberg
– Set-top Series
– Edge Series
 LifeSize
– No support for H.261 video
 VTEL IPanel

Desktop Endpoints:


Have built-in processors to handle some of the video encoding

 Most will rely on your PC’s monitor or will have a built-in monitor. Some with the

built in monitor can take the place of your current monitor or be used for dual
screen



Best to use only if you have one to three people at your site



Very few have external inputs for VGA, external cameras, etc.



Many have “strong arm” focusing which can be difficult to get the focus

exactly correct
Becoming less popular and expensive compared to software endpoints on



today’s faster processors
Most desktop endpoints with built in monitor are aimed at the “Executive”


level

Desktop Endpoints Examples:
 Polycom
– VSX 3000
– V700
– HDX 4000
 Tandberg 1000

Software Endpoints:


Most work only with Windows OS



Rely on your monitor for displaying video



Use USB or Firewire webcam for capturing video



Most software packages run in the $150 per endpoint range and offer a free

trial period download.

Software Endpoints Examples:
 Polycom PVX


www.polycom.com

 Xmeeting


http://xmeeting.sourceforge.net/

 RADVISION eConf


www.radvision.com

 Tandberg Movi
– http://www.tandberg.com/products/pc_videoconferencing.jsp

Telepresence Setups (H.323):


Multiple systems working together
o

Polycom

o

Tandberg

o

Lifesize



Specific room setup



Illusion of one single room

Techonology:

Dual

display: An

older Polycom

VSX

7000 system

and

camera

used

for

videoconferencing, with two displays for simultaneous broadcast from separate locations.
The core technology used in a video conferencing system is digital compression of
audio and video streams in real time. The hardware or software that performs
compression is called a codec (coder/decoder). Compression rates of up to 1:500 can be
achieved. The resulting digital stream of 1s and 0s is subdivided into labeled packets,
which are then transmitted through a digital network of some kind (usually ISDN or IP).
The use of audio modems in the transmission line allow for the use of POTS, or the Plain
Old Telephone System, in some low-speed applications, such as video telephony, because
they convert the digital pulses to/from analog waves in the audio spectrum range.

The other components required for a videoconferencing system include:


Video input : video camera or webcam



Video output: computer monitor , television or projector



Audio input: microphones, CD/DVD player, cassette player, or any other

source of Pre Amp audio outlet.


Audio output: usually loudspeakers associated with the display device or

telephone


Data transfer: analog or digital telephone network, LAN or Internet



Computer: a data processing unit that ties together the other components,

does the compressing and decompressing, and initiates and maintains the data linkage via
the network.
There are basically two kinds of videoconferencing systems:
1.

Dedicated systems have all required components packaged into a single

piece of equipment, usually a console with a high quality remote controlled video
camera. These cameras can be controlled at a distance to pan left and right, tilt up and
down, and zoom. They became known as PTZ cameras. The console contains all
electrical interfaces, the control computer, and the software or hardware-based codec.
Omnidirectional microphones are connected to the console, as well as a TV monitor with
loudspeakers and/or a video projector. There are several types of dedicated
videoconferencing devices:
1. Large group videoconferencing is non-portable, large, more expensive
devices used for large rooms and auditoriums.
2. Small group videoconferencing is non-portable or portable, smaller,
less expensive devices used for small meeting rooms.

3. Individual videoconferencing are usually portable devices, meant for
single users, have fixed cameras, microphones and loudspeakers integrated into the
console.
2.

Desktop systems are add-ons (hardware boards, usually) to normal PCs,

transforming them into videoconferencing devices. A range of different cameras and
microphones can be used with the board, which contains the necessary codec and
transmission interfaces. Most of the desktops systems work with the H.323 standard.
Videoconferences carried out via dispersed PCs are also known as e-meetings.

Conferencing layers:
The components within a Conferencing System can be divided up into several
different layers: User Interface, Conference Control, Control or Signal Plane and Media
Plane.
Video Conferencing User Interfaces could either be graphical or voice
responsive. Many of us have encountered both types of interfaces; normally we encounter
graphical interfaces on the computer or television, and Voice Responsive we normally get
on the phone, where we are told to select a number of choices by either saying it or
pressing a number. User interfaces for conferencing have a number of different uses; it
could be used for scheduling, setup, and making the call. Through the User Interface the
administrator is able to control the other three layers of the system.
Conference Control performs resource allocation, management and routing. This
layer along with the User Interface creates meetings (scheduled or unscheduled) or adds
and removes participants from a conference.
Control (Signaling) Plane contains the stacks that signal different endpoints to
create a call and/or a conference. Signals can be, but aren’t limited to, H.323 and Session
Initiation Protocol (SIP) Protocols. These signals control incoming and outgoing
connections as well as session parameters.

The Media Plane controls the audio and video mixing and streaming. This layer
manages Real-Time Transport Protocols, User Datagram Packets (UDP) and Real-Time
Transport Control Protocols (RTCP). The RTP and UDP normally carry information such
the payload type which is the type of codec, frame rate, video size and many others.
RTCP on the other hand acts as a quality control Protocol for detecting errors during
streaming.

Multipoint videoconferencing:
Simultaneous videoconferencing among three or more remote points is possible by
means of a Multipoint Control Unit (MCU). This is a bridge that interconnects calls from
several sources (in a similar way to the audio conference call). All parties call the MCU
unit, or the MCU unit can also call the parties which are going to participate, in sequence.
There are MCU bridges for IP and ISDN-based videoconferencing. There are MCUs
which are pure software, and others which are a combination of hardware and software.
An MCU is characterized according to the number of simultaneous calls it can handle, its
ability to conduct transposing of data rates and protocols, and features such as
Continuous Presence, in which multiple parties can be seen on-screen at once. MCUs can
be stand-alone hardware devices, or they can be embedded into dedicated
videoconferencing units.
The MCU consists of two logical components:
1. A single multipoint controller (MC), and
2. Multipoint Processors (MP) sometimes referred to as the mixer.

The MC controls the conferencing while it is active on the signaling plane, which
is simply where the system manages conferencing creation, endpoint signaling and inconferencing controls. This component negotiates parameters with every endpoint in the
network and controls conferencing resources while the MC controls resources and
signaling negotiations, the MP operates on the media plane and receives media from each

endpoint. The MP generates output streams from each endpoint and redirects the
information to other endpoints in the conference.
Some systems are capable of multipoint conferencing with no MCU, stand-alone,
embedded or otherwise. These use a standards-based H.323 technique known as
"decentralized multipoint", where each station in a multipoint call exchanges video and
audio directly with the other stations with no central "manager" or other bottleneck. The
advantages of this technique are that the video and audio will generally be of higher
quality because they don't have to be relayed through a central point. Also, users can
make ad-hoc multipoint calls without any concern for the availability or control of an
MCU. This added convenience and quality comes at the expense of some increased
network bandwidth, because every station must transmit to every other station directly.

Videoconferencing modes:
Videoconferencing systems have several common operating modes that are used:
1. Voice-Activated Switch (VAS).
2. Continuous Presence.
In VAS mode, the MCU switches which endpoint can be seen by the other
endpoints by the levels of one’s voice. If there are four people in a conference, the only
one that will be seen in the conference is the site which is talking; the location with the
loudest voice will be seen by the other participants.
Continuous Presence mode displays multiple participants at the same time. The
MP in this mode puts together the streams from the different endpoints and puts them all
together into a single video image. In this mode, the MCU normally sends the same type
of images to all participants. Typically these types of images are called “layouts” and can
vary depending on the number of participants in a conference.

Echo cancellation:
A fundamental feature of professional videoconferencing systems is Acoustic
Echo Cancellation (AEC). Echo can be defined as the reflected source wave interference
with new wave created by source. AEC is an algorithm which is able to detect when
sounds or utterances reenter the audio input of the videoconferencing codec, which came
from the audio output of the same system, after some time delay. If unchecked, this can
lead to several problems including:
1.

the remote party hearing their own voice coming back at them (usually

significantly delayed)
2.

strong reverberation, rendering the voice channel useless as it becomes hard

to understand and
3.

Howling created by feedback. Echo cancellation is a processor-intensive

task that usually works over a narrow range of sound delays.

Basis requirements for video conferencing:
In order to videoconference you need audio-visual hardware (camera, monitor,
speakers …) the necessary software and a carrier for transmitting the information.

1. Hardware
There are three main types of videoconferencing systems: room systems, compact
systems and desktop systems
Room (roll-about) systems are big videoconferencing systems standing in a
room, usually containing one or two TV monitors (displaying outgoing and incoming
information), a camera (with pan, tilt and zoom options) on top of it and a codec. The
system is mostly used in bigger rooms and for a large audience, usually in a distance

learning programmer with a remote guest speaker. This type of system usually works
with a 1 - 3 ISDN connection and has good image and sound quality. Recently there is
compatibility with broadband IP (Internet Protocol) videoconferencing as well.

Compact videoconferencing systems are small boxes (the size of a video recorder)
containing the codec and more or less enlarged possibilities for connections: video,
audio and data input and output and different types of network connections. Most
systems have a camera (with pan, tilt and zoom options) on top. The system can be
used as a mobile system or as the core system in an existing audio/video setting.
These systems usually use ISDN protocol but evolve towards IP.
Desktop systems: A multi-media personal computer with special hardware and
software is another (and cheaper) option. The monitor is smaller and therefore not
suitable for a large audience. Also the small camera on top of the monitor can capture
2 to max. 5 people with workable quality images. The incoming and outgoing
information is displayed in two windows on the screen with picture in picture
options. This type of system is often used with 1 ISDN connection and as a
consequence can only transmit less information. IP videoconferencing with webcams
offers cheaper connections.
Extras: All systems can be embedded in extra video and audio equipment.
Audio: extra microphones and speakers can be added. Existing audio-mixers and hifi equipment in the room can be connected to the system (beware for echo and sound
loops). You can of course also have audio input via cassette deck and CD-player.
Video: One can add extra cameras. Especially for the desktop systems it is wise to
add an extra fixed camera with pan, tilt and zoom options (and presets) or/and a
handy video camera. Thanks to a switch box the number of extra cameras can go up
to four or more.
In all cases add a document camera. This is a camera fixed on a stand with extra
lights and a zoom system. A document camera is very useful to show documents, pictures
and small objects. Also a video player can be added. Both systems can be connected to a
data/video projector.

Data: In most cases a computer can be added to the system in order to give a
power point presentation for a remote audience. If you have desktop systems on both
sides you can also do “file sharing” (white boarding).

2. Compression:
Since the bandwidth of the connection usually is limited it is important to reduce
the information you send through the wires. Compression techniques are based on
limiting the number of frames/sec (ranging from 5-30 frames/sec), eliminating redundant
information – e.g. sending only the differences with the previous frame - or reducing the
resolution or the size of the images. It is the codec’s (stands for coder-decoder) task to do
the digitizing and compression of the analogue information that is going to be sent and to
do the decompression and de-digitizing of the received data. This, together with the
transmission time over long distances, causes a time delay, an element of
videoconferences that has to be taken into account. A smaller band-width and higher
compression reduces of course the quality of the images and it is important in all cases to
inform your audience that they will not deal with full motion video quality.

3. Transmission:
At this stage most (room and compact) videoconferencing systems use ISDN
(Integrated Services Digital Network) working over regular telephone lines in 1, 2 or 3
pairs of so called B channels with a bandwidth of 128 Kbps per pair.
3 ISDN lines (384 Kbps) deliver very good quality images and sound. 1 ISDN line
(used for most desktop systems) delivers good workable material but requires preparation
and “correct behavior”.

Audio/Video Transmitter:
The transmitter module is a JMF/RTP based application. JMF manager class is
used to create a merged data source object for audio and video. This data source object is

passed to the manager class to create a processor object. While the Processor is in the
configured state, its track control objects are obtained for the individual audio and video
tracks.
Codecs for compression and encryption are set to both of the audio and video
tracks. After setting the codecs both of the tracks, processors realize method is called.
While the processor is in realized state the output data source is created from the
processor. The output data source object is passed to the RTP manager object to create
RTP sessions for audio and video transmission. We developed our own RTP connecter
class to send RTP and RTCP packets to the remote participants over the network by
encapsulating them in UDP packets and to receive RTP and RTCP packets from the
remote participants. Since we are not using RTCP for getting feedbacks from the
receivers, we do not transmit RTCP data all the time. From our RTP connector class we
can control the amount of RTCP data to be transmitted. An object of RTP connector class
is passed to RTP manager class at the time of creation RTP manager object.

Video Transmitter:
We use IBM’s implementation of H.263 encoder for video compression. We
developed the CODECs for encryption and decryption the audio/video streams using
Triple-DES encrypted of Java’s crypto library. Video frames are generated by data source
in YUV format. Each YUV frame is compressed to H.263 frame. The compressed H.263
frames are encrypted using Triple- DES encrypted and are passed to the RTP manager
object. RTP manager encapsulates the encrypted H.263 frames in the RTP packets and
passes them to the RTP connector object which in send the RTP packets to the remote
participants by encapsulating them in UDP packets.
RTP connector sends a separate UDP packet for each RTP packet to each of the
remote participant. We can add or remove a recipient dynamically. H.263 encoder
provides some controls like bit Rate Control, key Frame Rate Control etc., that we can
use to control the QoS dynamically during the transmission.

Video Transmitter

Audio Transmitter:
We use IBM’s implementation of G.723 encoder for audio compression. G.723 is
very efficient compression technique. Using it we can transmit good quality audio data of
human voice at 6 to 7 kbps. Since G.723 encoder generates very small sized packets
G.723 packetizer is used to format packets of size 48 byte. The Encryption is done after
the packetizer. Rest of the process is exactly same as for video transmission.

Audio Transmitter

Audio/Video Receiver:
Video Receiver:

At the receiver side we get Encrypted H.263 frame from the RTP Manager. It is
decrypted using Triple-DES decrypter and then decoded back into YUV format using
Sun’s implementation of H.263 decoder. YUV frame converted into RGB frame and it is
then displayed into the receiver’s window using direct video renderer.

Video Receiver

Audio Receiver:
It is same as video receiver except that it uses G.723 decoder and sound renderer.

Audio Receiver

Client-Server Architecture:

The system includes a centralized server and distributed client. Distribution of
audio and video data between the client nodes is done using point-to-point connections
between clients. The server manages the connection between the clients. It server is also
responsible of distribution of session key for encryption of audio video streams and
controlling the QoS.

Client server authentication

Functions of the server:
Registration of the users:
Each user must be registered at the server in order to take part in the conference.
At the time of registration user will provide his information to the server along with
his/her public key. User will get a unique user-id and server’s public key. These public
keys will be used at the time of authentication.

Authentication of users:
At the time of joining a conference by a user the server and the user, both will
authenticate each other using their private-public key pairs.

Distribution of the session key:

After authenticating a user, the server will send the session key to the client
application running at the user side in a secure manner. This session key will be common
for all users taking part in a particular conference.

Maintaining the state of the conference:
Whenever a user will join or leave a conference the server will inform the other
users of that conference and provide them necessary information in order to maintain the
state of the conference.

Controlling QoS:
Server will also responsible of controlling quality of service (QoS) of the
audio/video data exchanged between the clients. In order to do that, the server gets the
feedbacks from the clients about every media stream they are receiving. For each client,
the server maintains QoS statistics from the feedbacks of all receivers of that client and
whenever required it sends the QoS control signals to the client to maintain the quality of
media stream being sent by that client.

Functions of the client:
Session setup:
The client application will interact with the server to get the session key and
information of other users to setup a conferencing session.

Capturing the audio/video stream:
The client application will be responsible of capturing user’s real time audio and
video streams from the capturing devices.

Compression and Encryption of the audio/video streams:
The client will compress the audio and video streams to reduce the bandwidth
requirements. It will also encrypt each packet of the audio video stream before
transmission using the session key got from the server.

Creation of RTP session:

The client application will create RTP sessions for transmitting real time
audio/video streams of the users to other users taking part in the conference. Two separate
sessions will be created for audio and video.

Opening RTP sessions:
The client application will open RTP sessions for each user whose audio/video
streams the user wants to receive.

Decryption and Decompression:
Decryption and Decompression will be done both audio and video streams of each
user to get the streams in their original form.

Rendering the audio/video stream:
Finally the incoming audio and video streams will be rendered and will be sent to
the speakers and display unit respectively.

Maintaining QoS:
The client application will monitor the incoming audio/video streams and will
send the feedbacks to the server. It will change the parameters of the media streams being
transmitted accordingly whenever it will get the QoS controls from the server for
example reducing the bit rate.

Security protocols:
The

RSA

public

key

algorithm

(with

2048

bit

key)

for

authentication of the users at the server and Triple-DES symmetric key
algorithm for encrypting audio video streams by the clients before
transmission. The symmetric key (called session key) is generated by
the server at commencement of every new conference and is
distributed in the clients. So every client taking part in a particular
conference will have the same session key. Both encryption and
decryption is done using same key.

Registration of the users:

Every user must be registered at server before they can take part in any
communication.
Since we don’t have any secure channel to pass the user’s authentic information to
the server via network we assume that the user itself will come at the server room and the
registration will be done in the presence of the administrator of the server. The user will
required to generate a RSA key pair on his/her own computer and will bring the public
part of the RSA key pair at the server. At the time of registration the user will submit
his/her public key and will get a unique user id and the server’s public key.

Authentication and key distribution:
In the first message time stamp is used to provide freshness guarantee of the user’s
request in order to guard against replay attack. The challange1 and challenge2 are long
random numbers freshly generated by the client and the server respectively. After getting
challenge1 back from the server, the client ensures the server’s authenticity because
nobody other than server can extract the challenge1 from first message. Similarly the
server ensures the authenticity of client after getting challenge2 back. After first three
messages both the client and the server have authenticated each other.

Authentication protocol

In the fourth message server sends the session key to the user. User’s challenge
(challenge1) is included in the fourth message to prevent replay attack. Every subsequent
message from this client to the server includes challange2 and every subsequent message
from the server to this client will include challenge1 because these random numbers are
freshly generated for current session and ensure the client and the server that message
having these number can’t be a copy of message of some previous session and hence
prevent the replay attack.

Maintaining the state of the conference:
Creating or joining a conference:
Every registered user can create a new conference at any time. There can be
multiple conferences running at the same time. Following are the steps for creating a new
conference:
1. Client program sends connect request to the server and both the client and
server authenticate each other.
2. Server sends list of conferences already running. User can select a conference to
join or he/she can choose to create a new conference. Client sends the user’s request to
the server.
3. If the request is for a new conference, the server starts a new conference thread
and adds that user in the conference. Server then generates a new session key for this
conference and sends a secure copy of this session key and a unique port base (every
client in a particular conference is assigned a unique port base for sending audio and
video streams) to the client.
4. If the request is for joining an existing conference the server sends the session
key of the conference and port base to the client and then sends following information:
a. If the user wants to join as active mode
i. The server sends the information (name, IP, port base) of all other
participants in the conference to this client.
ii. The server sends the information of this participant to all other clients.

b. If the user wants to join as passive mode (listener only)
i. The server sends the information of all other active participants in the
conference to this client.
ii. The server sends the information of this participant to all other active
clients.

Leaving the conference
Client sends a left request to the server. Server disconnects the connection to this
client and does one of the following:
1. If this user was the last user in the conference then server close the conference
and remove the conference from the list of conference.
2. If the user was an active participant the server sends the information about
leaving the conference by this client to all other participants in the conference.
3. If the user was a passive participant the server sends the information about
leaving the conference by this client to all other active participants in the conference.

Problems in video conferencing:
Some

observers

argue

that

three

outstanding

issues

have

prevented

videoconferencing from becoming a standard form of communication, despite the
ubiquity of videoconferencing-capable systems. These issues are:
1.

Eye Contact:
Eye contact plays a large role in conversational turn-taking, perceived attention

and intent, and other aspects of group communication. While traditional telephone
conversations give no eye contact cues, many videoconferencing systems are arguably
worse in that they provide an incorrect impression that the remote interlocutor is avoiding
eye contact. Some Tele-presence systems have cameras located in the screens that reduce
the amount of parallax observed by the users. This issue is also being addressed through
research that generates a synthetic image with eye contact using stereo reconstruction.
Telcordia Technologies, formerly Bell Communications Research, owns a patent for eyeto-eye videoconferencing using rear projection screens with the video camera behind it,

evolved from a 1960s U.S. military system that provided videoconferencing services
between the White House and various other government and military facilities. This
technique eliminates the need for special cameras or image processing.
2.
Appearance Consciousness:
A second psychological problem with videoconferencing is being on camera, with
the video stream possibly even being recorded. The burden of presenting an acceptable
on-screen appearance is not present in audio-only communication. Early studies by
Alphonse Chapanis found that the addition of video actually impaired communication,
possibly because of the consciousness of being on camera.
3.
Signal latency:
The information transport of digital signals in many steps needs time. In a
telecommunicated conversation, an increased latency larger than about 150–300 ms
becomes noticeable and is soon observed as unnatural and distracting. Therefore, next to
a stable large bandwidth, a small total round-trip time is another major technical
requirement for the communication channel for interactive videoconferencing.
The issue of eye-contact may be solved with advancing technology, and presumably the
issue of appearance consciousness will fade as people become accustomed to
videoconferencing.

Social and institutional impact:
Impact on the general public:
High speed Internet connectivity has become more widely available at a
reasonable cost and the cost of video capture and display technology has decreased.
Consequently, personal videoconferencing systems based on a webcam, personal
computer system, software compression and broadband Internet connectivity have
become affordable to the general public. Also, the hardware used for this technology has
continued to improve in quality, and prices have dropped dramatically. The availability of
freeware (often as part of chat programs) has made software based videoconferencing
accessible to many.

For over a century, futurists have envisioned a future where telephone
conversations will take place as actual face-to-face encounters with video as well as
audio. Sometimes it is simply not possible or practical to have face-to-face meetings with
two or more people. Sometimes a telephone conversation or conference call is adequate.
Other times, e-mail exchanges are adequate. However, videoconferencing adds another
possible alternative, and can be considered when:


a live conversation is needed;



visual information is an important component of the conversation;



the parties of the conversation can't physically come to the same location;



the expense or time of travel is a consideration.

Deaf, hard-of-hearing and mute individuals have a particular interest in the
development of affordable high-quality videoconferencing as a means of communicating
with each other in sign language. Unlike Video Relay Service, which is intended to
support communication between a caller using sign language and another party using
spoken language, videoconferencing can be used between two signers.
Mass adoption and use of videoconferencing is still relatively low, with the
following often claimed as causes:


Complexity of systems: Most users are not technical and want a simple

interface. In hardware systems an unplugged cord or a flat battery in a remote control is
seen as failure, contributing to perceived unreliability which drives users back to
traditional meetings. Successful systems are backed by support teams who can proactively support and provide fast assistance when required.


Perceived lack of interoperability: not all systems can readily

interconnect, for example ISDN and IP systems require a gateway. Popular software
solutions cannot easily connect to hardware systems. Some systems use different

standards, features and qualities which can require additional configuration when
connecting to dissimilar systems.


Bandwidth and quality of service: In some countries it is difficult or

expensive to get a high quality connection that is fast enough for good-quality video
conferencing. Technologies such as ADSL have limited upload speeds and cannot upload
and download simultaneously at full speed. As Internet speeds increase higher quality and
high definition video conferencing will become more readily available.


Expense of commercial systems - a well-designed system requires a

specially designed room and can cost hundreds of thousands of dollars to fit out the room
with codecs, integration equipment and furniture.


Participants being self-conscious about being on camera, especially new

users and older generations.
For these reasons many hardware systems are often used for internal corporate use
only, as they are less likely to run into problems and lose a sale. An alternative is
companies that hire out videoconferencing-equipped meeting rooms in cities around the
world. Customers simply book the rooms and turn up for the meeting - everything else is
arranged and support is readily available if anything should go wrong.

Impact on sign language communications:
One of the first demonstrations of the ability for telecommunications to help sign
language

users

communicate

with

each

other

occurred

when AT&T's videophone (trademarked as the "Picture phone") was introduced to the
public at the 1964 New York World's Fair –two deaf users were able to communicate
freely with each other between the fair and another city. Various other organizations,
including British Telecom's Martlesham facility and several universities have also
conducted extensive research on signing via video telephony. The use of sign language
via video telephony was hampered for many years due to the difficulty of using it

over regular analogue phone lines coupled with the high cost of better quality data phone
lines, factors which largely disappeared with the advent of high-speed ISDN and IP
Internet services in the last decade of the 20th Century.
21st century improvements:
Significant improvements in video call quality of service for the deaf occurred in
the United States in 2003 when Sorenson Media Inc. (formerly Sorenson Vision Inc.), a
video compression software coding company, developed its VP-100 model standalone videophone specifically for the deaf community. It was designed to output its video
to the user's television in order to lower the cost of acquisition, and to offer remote
control and a powerful video compression codec for unequaled video quality and ease of
use with video relay services. Favorable reviews quickly led to its popular usage at
educational facilities for the deaf, and from there to the greater deaf community.
Coupled with similar high-quality videophones introduced by other electronics
manufacturers, the availability of high speed Internet, and sponsored video relay
services authorized by the U.S. Federal Communications Commission in 2002, VRS
services for the deaf underwent rapid growth in that country.
Present day usage:
Using such video equipment in the present day, the deaf, hard-of-hearing and
speech-impaired can communicate between themselves and with hearing individuals
using sign language. The United States and several other countries compensate
companies to provide 'Video Relay Services' (VRS). Telecommunication equipment can
be used to talk to others via a sign language interpreter, who uses a conventional
telephone at the same time to communicate with the deaf person's party. Video equipment
is also used to do on-site sign language translation via Video Remote Interpreting (VRI).
The relative low cost and widespread availability of 3G mobile phone technology with
video calling capabilities have given deaf and speech-impaired users a greater ability to
communicate with the same ease as others. Some wireless operators have even started
free sign language gateways.

Sign language interpretation services via VRS or by VRI are useful in the presentday where one of the parties is deaf, hard-of-hearing or speech-impaired (mute). In such
cases the interpretation flow is normally within the same principal language, such
as French Sign Language (LSF) to spoken French, Spanish Sign Language (LSE) to
spoken Spanish, British Sign Language(BSL) to spoken English, and American Sign
Language (ASL) also to spoken English (since BSL and ASL are completely distinct to
each other), and so on

.
A deaf or hard-of-hearing person at his workplace using a VRS to communicate with a
hearing person in London.
Multilingual sign language interpreters, who can also translate as well across
principal languages (such as to and from SSL, to and from spoken English), are also
available, albeit less frequently. Such activities involve considerable effort on the part of
the

translator, since

sign

languages

are

distinct natural

languages with their

own construction, semantics and syntax, different from the aural version of the same
principal language.
With video interpreting, sign language interpreters work remotely with
live video and audio feeds, so that the interpreter can see the deaf or mute party, and
converse with the hearing party, and vice versa. Much like telephone interpreting, video
interpreting can be used for situations in which no on-site interpreters are available.
However, video interpreting cannot be used for situations in which all parties are

speaking via telephone alone. VRS and VRI interpretation requires all parties to have
the necessary equipment. Some advanced equipment enables interpreters to control the
video camera remotely, in order to zoom in and out or to point the camera toward the
party that is signing.

A Video Interpreter (V.I.) assisting an on-screen client.

Impact on education:
Videoconferencing provides students with the opportunity to learn by participating
in two-way communication forums. Furthermore, teachers and lecturers worldwide can
be brought to remote or otherwise isolated educational facilities. Students from diverse
communities and backgrounds can come together to learn about one another,
although language barriers will continue to persist. Such students are able to explore,
communicate, analyze and share information and ideas with one another. Through
videoconferencing students can visit other parts of the world to speak with their peers,
and visit museums and educational facilities. Such virtual field trips can provide enriched
learning opportunities to students, especially those in geographically isolated locations,
and to the economically disadvantaged. Small schools can use these technologies to pool
resources and provide courses, such as in foreign languages, which could not otherwise
be offered.
A few examples of benefits that videoconferencing can provide in campus
environments include:



faculty members keeping in touch with classes while attending conferences;



guest lecturers brought in classes from other institutions;



researchers collaborating with colleagues at other institutions on a regular

basis without loss of time due to travel;


schools with multiple campuses collaborating and sharing professors;



faculty members participating in thesis defenses at other institutions;



administrators on tight schedules collaborating on budget preparation from

different parts of campus;


faculty committee auditioning scholarship candidates;



researchers answering questions about grant proposals from agencies or

review committees;


student interviews with an employers in other cities, and



Tele-seminars.

Impact on medicine and health:
Videoconferencing

useful

technology

time telemedicine and Tele-nursing applications,

such

as diagnosis,

transmission

videoconferencing,

of medical

is
images,

a

highly
etc...

With

contact nurses and physicians in emergency or

routine

situations;

for

real-

consulting,
patients

may

physicians

and

other paramedical professionals can discuss cases across large distances. Rural areas can
use this technology for diagnostic purposes, thus saving lives and making more efficient
use of health care money. For example, a rural medical center in Ohio, United States,
used videoconferencing to successfully cut the number of transfers of sick infants to
a hospital 70 miles (110 km) away. This had previously cost nearly $10,000 per transfer.

Special peripherals

such as microscopes fitted with digital cameras, video

endoscopes, medical ultrasound imaging devices, otoscopes, etc., can be used in
conjunction with videoconferencing equipment to transmit data about a patient. Recent
developments in mobile collaboration on hand-held mobile devices have also extended
video-conferencing capabilities to locations previously unreachable, such as a remote
community, long-term care facility, or a patient's home.

Impact on business:
Videoconferencing can enable individuals in distant locations to participate in
meetings on short notice, with time and money savings. Technology such as VoIP can be
used in conjunction with desktop videoconferencing to enable low-cost face-to-face
business meetings without leaving the desk, especially for businesses with widespread
offices. The technology is also used for telecommuting, in which employees work from
home. One research report based on a sampling of 1,800 corporate employees showed
that, as of June 2010, 54% of the respondents with access to video conferencing used it
“all of the time” or “frequently”.
Videoconferencing is also currently being introduced on online networking
websites, in order to help businesses form profitable relationships quickly and efficiently
without leaving their place of work. This has been leveraged by banks to connect busy
banking

professionals

with

customers

in

various

locations

using video

banking technology.
Videoconferencing

on

hand-held

mobile

devices

(mobile

collaboration technology) is being used in industries such as manufacturing, energy,
healthcare, insurance, government and public safety. Live, visual interaction removes
traditional restrictions of distance and time, often in locations previously unreachable,
such as a manufacturing plant floor a continent away.
Although videoconferencing has frequently proven its value, research has shown
that some non-managerial employees prefer not to use it due to several factors, including

anxiety. Some such anxieties can be avoided if managers use the technology as part of the
normal course of business.
Researchers also find that attendees of business and medical videoconferences
must work harder to interpret information delivered during a conference than they would
if they attended face-to-face. They recommend that those coordinating videoconferences
make adjustments to their conferencing procedures and equipment.

Impact on law:
In the United States, videoconferencing has allowed testimony to be used for an
individual who is unable or prefers not to attend the physical legal settings, or would be
subjected to severe psychological stress in doing so, however there is a controversy on
the use of testimony by foreign or unavailable witnesses via video transmission,
regarding the violation of the Confrontation Clause of the Sixth Amendment of the U.S.
Constitution.
In a military investigation in State of North Carolina, Afghan witnesses have
testified via videoconferencing.
In Hall County, Georgia, videoconferencing systems are used for initial court
appearances. The systems link jails with court rooms, reducing the expenses and security
risks of transporting prisoners to the courtroom.
The U.S. Social Security Administration (SSA), which oversees the largest
administrative judicial system in the world, under its Office of Disability Adjudication
and Review (ODAR), has made extensive use of video teleconferencing (VTC) to
conduct hearings at remote locations. In FY 2009, SSA conducted 86,320 VTC hearings,
a 55% increase over FY 2008. In August 2010, the SSA opened its fifth and largest videoonly National Hearing Center (NHC), in St. Louis, Missouri. This continues SSA's effort
to use video hearings as a means to clear its substantial hearing backlog. Since 2007, the
SSA has also established NHCs in Albuquerque, New Mexico, Baltimore, Maryland,
Falls Church, Virginia, and Chicago, Illinois.

Impact on media relations:
The concept of press videoconferencing was developed in October 2007 by the
Pan African Press Association (APPA), a Paris France based non-governmental
organization, to allow African journalists to participate in international press
conferences on developmental and good governance issues.
Press

videoconferencing

permits

international

press

conferences

via

videoconferencing over the Internet. Journalists can participate on an international press
conference from any location, without leaving their offices or countries. They need only
be seated by a computer connected to the Internet in order to ask their questions to the
speaker.
In 2004, the International Monetary Fund introduced the Online Media Briefing
Center, a password-protected site available only to professional journalists. The site
enables the IMF to present press briefings globally and facilitates direct questions to
briefers from the press. The site has been copied by other international organizations
since its inception. More than 4,000 journalists worldwide are currently registered with
the IMF.

Future of video conferencing:
The most important development in videoconference will be the result of increased
bandwidth on Internet based communications. To date, Internet video conferencing
products such as Microsoft’s NetMeeting and White Pine’s CuSee Me have allowed
restricted communications over the Internet with restricted quality video and audio.
However this is about to change. These products, and an increasing number of new ones,
are about to benefit from the increased bandwidth that ADSL, satellite, optical and radio
are going to offer. The net result will be the integration of the two solutions.
These developments will offer educationalists a wealth of new opportunities that
will include:



Lower connection charges – the costs of ISDN connection charges will

disappear as the connections will be via the Internet. At worst, these will be local
telephone charges. This will dramatically reduce ‘on line’ charges especially in
International videoconferences where, using ISDN, two- six International calls are
charged. As the Internet offers Global connectivity, users will no longer have to worry
about which country they connect with as the connection charge will be uniform.

‘Multipoint’ videoconferencing will be as cost effective as ‘point to point’
using Internet ‘reflector’ sites. Education Authorities should now be assessing the future
development and hosting of such reflectors with a view to offering password protected
‘safe’ videoconferencing areas to education. The potential of Distance Learning is
enormous as the bandwidth increases, offering schools the opportunity to offer elective or
required courses for which certified teachers are not available or in situations where
student numbers are not sufficient to hire a full time teacher in one campus.

Videoconference solutions will be easily integrated into existing PC’s
allowing communication across an existing LAN, WAN or the Internet. This will allow
organizations to implement a flexible solution to internal and external communications
using the same equipment. The development of GPRS and UMTS will further enhance
communications by allowing the integration of mobile telephony into the system. Groups
on a field trip will be able to videoconference with students back at school or with any
group of learners anywhere in the World. This flexibility, coupled with the advantages of
application sharing and collaborative software will offer an unprecedented degree of
communication.
Thanks to the new bandwidth offered by these new technologies, the WWW will
dramatically change in communication style. Video and multimedia are becoming more
widespread on the Internet. Video, as a medium, will become more common place as
developers utilize it in sites. Web TV and radio will be areas where schools and educators
can disseminate information. Whoever said video is dead did not read the small print.

Summary:
Video conferencing applications can be classified according to a matrix of network
type and number of participants. The network types are primarily LAN (Local Area
Network, i.e., Internet connectivity) and ISDN (phone system); the participant number is
person-to-person or group. Often the determination of whether to videoconference with a
remote site must be based on whether that site uses H.323 (LAN) or not. ISDN is still
very prevalent at commercial sites and even in some educational sites.
While desktop video conferencing itself may not be sufficiently mature to warrant
investment of large amounts of resources for wide deployment, desktop collaboration is
evolving as a valuable tool for the workplace. Desktop video still may be very
appropriate in some cases. A person who is considering use of desktop videoconferencing
needs to be aware of the current shortfalls imposed by network bandwidth restrictions
and the impact of other network usage. In general, a site that uses Internet 2 will not
experience the same network congestion as a site on the commercial Internet. This is an
area that is continuing to evolve. Early adopters may gain valuable experience, but also
may need to make equipment and hardware upgrades regularly to take advantage of
advances in the field.
Video conferencing is now certainly growing very rapidly. It saves significant
amount of money in terms of both travel and time. During the last decade availability of
the equipment’s and internet connections at the reasonable cost make it affordable to a
much wider group of users. It is now widely used in the fields of education, collaborative
work between researchers and business communities, telemedicine and in many other
fields. On the other hand recent terrorist activities have forced many organizations and
government agencies to re-examine their existing security policies and mechanisms. The

government agencies must now carefully safeguard their sensitive data transmission, for
example transmission of voice, video and other data during videoconference meetings.

Reference:
www.wikipedia.org
www.global-leap.org/newspaper/vc_case_studies_ summary_report.pdf
www.webex.co.in › Large Business › Overview › Intro to WebEx
www.webopedia.com/TERM/V/ videoconferencing.html
www-td.fnal.gov/atwork/conference/ib2_tutorial/Tutorial.doc
www.facweb.iitkgp.ernet.in/~jay/slides/vid_conf_ws.ppt

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