Video conferencing allows people at different physical locations to conduct face-to-face meetings virtually. It works by using computer networks and audio-visual equipment to transmit video and audio data between two or more locations in real-time. Key components of video conferencing systems include video cameras, microphones, screens or monitors, speakers, a codec to compress and decompress the audio-visual data, and a network connection. Popular protocols for video conferencing include H.320 for ISDN networks and H.323 for internet-based video calls.

1. Video Conferencing

2. Introduction
Group of successful businesspeople
having a teleconference

3. Introduction
 What is Video Conferencing ?
 Video conferencing (or video conference) means to
conduct a conference between two or more participants
at different sites by using computer networks to transmit
audio and video data.
 In its most basic form , video conferencing is the
transmission of image (video) and speech (audio) back and
forth between two or more physically separate locations .

4. Introduction
 Videoconferencing uses audio and video
telecommunications to bring people at different sites
together.

5. Introduction
 This can be as simple as a conversation between people in
private offices (point-to-point)

6. Introduction
 Or may involve several (multipoint) sites in large rooms at
multiple locations.

7. Introduction
 Besides the audio and visual transmission of meeting activities,
allied videoconferencing technologies can be used to share
documents and display information on whiteboards.

8. MODES OF VIDEO CONFERENCING
 Point-to-Point: A videoconference that connects two
locations
 Multi-point: A videoconference that connects more than
two locations through a Multi-point Control Unit (MCU)

9. Components Required
 Video Input – 2 or more video cameras or web cams;
possibly digital projectors / whiteboards.
 Audio Input – microphones either centrally located or on
individuals.
 Video Output – monitor, computer screen, television
and/or projector.
 Audio Output – professional speakers, headphones or
laptop computer speakers.

10. Components Required
 Codec – hardware or software-based coder-decoder
technology that compresses analog video and audio data
into digital packets and decompresses the data on the
receiving end.
 Echo cancellation software – diminishes audio delays to
enable real-time conversation.
 Network for data transfer – today most video
conferencing is transmitted over a high-speed broadband
Internet connection, using similar technology as VoIP
(Voice over Internet Protocol) but LAN and occasionally
ISDN connections are used.

11. Requirements
 Data Size : Voice
• Band width: ~ 4 KHz
• Minimum Sampling Frequency: 8 KHz
• Bits per sample: 8 bits (for 256 levels)
• Minimum data rate: 8000x8 bits per second = 64 Kbps
 Data Size : Video
• Number of frames per second: 15 fps
• Resolution of a frame: 480 x 640 pixels
• Bits per pixel: 24 bits (for colored video)
• Data Rate: 480x640x15x24 bits per second = 110.6 Mbps

12. Technology
 The core technology used in a videoconferencing 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).

13. Codec
 In simplest form, a codec is a software algorithm that
transforms data from one format to another.
 Stands for coder-decoder or compressor-de-compressor.
 Codec used to compress file must be the same used to
decompress file .

14. Two types of Codec
 Lossy Codecs: Lossy codecs reduce quality by some
amount in order to achieve compression. Often, this type
of compression is virtually indistinguishable from the
original uncompressed sound or images, depending on the
codec and the settings used. Lower data rates also reduce
cost and improve performance when the data is
transmitted.
 Lossless Codecs: Lossless codecs are typically used for
archiving data in a compressed form while retaining all of
the information present in the original stream. If
preserving the original quality of the stream is more
important than eliminating the correspondingly larger
data sizes, lossless codecs are preferred.

15. Lossy Codecs
 File Formats - GIF & JPEG
 They are only approximations of the original image.
 Achieve much higher rates of file size reduction by
discarding data that is deemed unnecessary or redundant.
 Since information is discarded, recreating the original file
exactly is not possible when file is de-compressed.
 Ideally, some data can be discarded and not missed.

16. Lossless Codecs
 File Formats – ZIP files and StuffIt archives
 Original files can be recreated exactly.
 Takes advantage of redundant information representing
more efficiently
 AAAAAAAA becomes 8A – reducing storage by 75%
 Hyper Text Markup Language becomes HTML.

17. Lossless Codecs
 Huffman coding replaces frequently occurring sequences
with shorter code . The idea is to assign variable-length
codes to input characters, lengths of the assigned codes
are based on the frequencies of corresponding characters.
 When de-compressed HTML becomes Hyper Text Markup
Language .
 Great for quality concerns – but minimal compression
ratios.
 Would not work well for Streaming Media, for example.

18. Data Compression
Alternative description of data requiring less storage and
bandwidth.
Compressed (JPEG)
50 Kbyte (20:1)
Uncompressed
1 Mbyte

19. Components Required
Camera
Display DevicesCodec
Microphone
Streaming & Archiving
Equipment
Video
Codec compresses audio/video data
Small enough to be transmitted over
expensive network connections
Audio
Codec decompresses audio/video
data received and displays it on
the display devices

20. Network Choices
 ISDN - Connects sites utilizing the H.320 standard
 IP - Connects sites utilizing the H.323 standard
 The most cost effective speed for typical video
conferencing meetings is 384 Kbps or 512 Kbps

21. Protocols for VC
 H.320 ( 1990)
- ISDN
 H.323 (1996)
- IP
 SIP (Session Initiation Protocol)
- Used by most Voice Over IP (VOIP) solutions

22. H.323
H.323 contains several protocols:
 H.225.0 : Call Signaling between two H.323 endpoints
 Registration, Admission, and Status (RAS) : RAS is used
between an endpoint and a Gatekeeper.
 H.245 : Control protocol for opening and closing logical
channels for audio, video and data, capability exchange,
control and indications.
 H.450 : For various supplementary services

23. H.323
 H.235 : for security within H.323, including both signaling
and media security
 H.239 : describes dual stream use (usually for live video,
the other for presentation.)
 H.460 : optional extensions that might be implemented by
an endpoint or a Gatekeeper.
 In addition to those ITU recommendations, H.323 utilizes
various IETF RFCs for media transport and media
packetization, including RTP.

24. H.323
Codecs :
 Video codecs: H.261, H.263, H.264.
 Audio codecs: G.711, G.729, G.729a, G.723.1, G.726
 Text codecs: T.140

25. Network Servers for VC
 Gatekeeper
• Allows assignment of static numbers
• Allows use of MCUs, and Gateways
 Multi Point Control Unit(MCU)
• Allows more than two participants to be in the call at
the same time.
 Gateway
• Allows calls to and from telephones.
 Ridgeway Server
• Firewall/NAT solution.

26. Network Servers for VC
GateKeeper
MCU
H.323 Clients
INTERNET
Gateway
ISDN
POTS line
Telephone

27. Challenges in Internet VC
 When H.323 terminals communicate directly with each other,
they must have direct access to each other's IP address. But this
exposes key network information to a potential attacker. By
locating the endpoints behind a firewall only the public
addresses are exposed, keeping the majority of address
information hidden.
 However, conferencing successfully through a firewall depends
upon how well the firewall is capable of dealing with the
complexities of the H.323 protocol. If the firewall cannot
provide dynamic access control based on looking at the control
channel status, then NAT inside the firewall can be used to map
an endpoints internal non-routable IP address a public IP
address and hence provide access control.

28. Challenges in Internet VC
 When you specify that an endpoint should use NAT, it embeds
the outside world IP address of the firewall into its IP header.
This is how the far end system knows the outside world IP
address to return the call. The endpoint cannot use its internal
IP address as this is non-routable and you want it hidden. On
receiving inbound traffic, the firewall uses NAT to forward to
the traffic to the endpoint. But using NAT can cause issues if
you also want to connect over a VPN.
 Furthermore, NAT by itself with H.323 endpoints has two major
limitations. By definition, every H.323 endpoint uses port 1720
TCP to initiate a call; but you can only NAT one internal address
to one public address, so to use NAT by itself, you would need a
public IP address for every H.323 endpoint; which is clearly
impractical if you want to deploy several video conferencing
devices.

29. Challenges in Internet VC
 Also, using NAT by itself, even for just one endpoint, still leaves the
H.323 endpoint open to spam attacks or unwanted calls as it is
mapped directly to a public IP address.
 This is where an H.323 Gatekeeper can be used. The H.323
Gatekeeper is responsible for providing address translation between
an endpoints current internal IP address and its various H.323 aliases.
Inbound calls from the outside world, in the form of the Gatekeepers
public IP address followed by a delimiter and then the H.323
endpoints alias, are directed to the Gatekeeper, which then looks-up
the endpoints alias to determine its current internal IP address. The
call is then be routed to the specific endpoint.
 When you use register an H.323 endpoint with a Gatekeeper, you DO
NOT enable or configure it to use NAT.Since only the Gatekeeper, via
RAS on port 1719 and Call Setup on port 1720 are the only systems
that interact with H.323 device outside the firewall, access rules in
the firewall can be set to pass traffic destined for the Gatekeeper or
endpoint.

30. Quality of Service(QoS)
Three advanced functions to enhance QoS over network are:
 Forward Error Correction(FEC): FEC function that
corrects errors in transmission at the receiving end.
 Adaptive Rate Control(ARC): ARC function automatically
varies the video data transfer rate to meet changing
network conditions.
 Real-time Auto Repeat Request (ARQ):ARQ function
recovers lost IP packets.

31. Uses
 Business
 E-Meetings
 E-Learning and Presentations
 Chatting with friend and Family talk
 Telemedicine
 Transmission of medical images
 Diagnostics and medical consulting

32. Advantages
 VC impacts student learning in several ways :
• guest lecturers brought in classes from other institutions
• schools from two separate nations engaging in cross-
cultural exchanges
• student interviews with an employers in other cities
• Teleseminars
• Students have the opportunity to interact with the experts
in a particular field of study
• Improves students’ –
1. Presentation and speaking skills
2. Communication and management skills
3. Questioning and interviewing skills

33. Advantages
 Use of sign language communications for deaf, hard-of-hearing
and mute
 Can improve work quality and reduce costs
 Improves communication
 Critical meetings can be conducted in less time
 More faculty and staff can be involved

34. Limitations
 Initial cost of the equipment is high
 Blurred images seen when rapid movement occurs
 Audio echo effect seen when system is not properly installed
 Complexity of systems: Most users are not technical and want
a simple interface.
 Expense of commercial systems
 Self-consciousness about being on camera and lack of direct eye
contact

35. Thank You!