Let’s have a look at the types of videoconferencing. For example point-to-point (between two people) videoconferencing functions more like a video telephone. Each participant has a video camera, microphone and speakers linked to their computers.
As the two people speak their voices are carried over and delivered to the others’ through the network, and the simultaneous images from the video camera along with the voices appear in monitors of either participants.
Similarly multipoint videoconferencing involves three or more participants to sit in a virtual conference room and interact with each other as if they were sitting in the same place.
History:
The videoconferencing technology has come along way since the simple analog videoconferences which existed as early as the invention of television. Such videoconferencing systems consisted of two closed-circuit television systems connected via cable.
During the space explorations NASA used two radiofrequency links (UHF or VHF) one in each direction. This sort of videoconferencing is also used by TV channels when reporting from far locations.
The first breakthrough in Video teleconferencing systems started in the 1990’s when some of the leading manufacturers like Picture Tel began launching them.
Since then along with a booming market of ISDN networks highly expensive Video teleconferencing systems became readily available to people at a reasonable price.
It was only in the 1990’s that the IP (Internet Protocol) based videoconferencing developed and enabling videoconferencing through Desk top or PC. With this came the free online services and software like MSN messenger, Yahoo messenger and Net meeting.
Technology:
Video teleconference (VTC) is based on compression of audio and video streams in real time with the help of a codec. This facilitates a compression rate of around to 1:500.
Then the resulting digital stream is subdivided into some kind of labeled packets which is then transmitted through a digital network of ISDN or IP.
The components involved in VTC are:
Video input video camera or web cam
Video output computer monitor or television
Audio input microphone
Audio output loudspeakers
Data transfer analog or digital telephone network, LAN or internet.
Types:
There are normally two types of VTC systems:
Dedicated systems:
It has all the required components assembled into single piece of equipment a console with a remote controlled video camera able to move in all directions.
Desktop systems:
They are add-ons or (hard ware boards) to normal PC’s transforming them to VTC devices. This board is connected to the necessary cameras, microphones, codec and transmission interfaces.
Video conferences conducted through PC’s are also known as e-meetings.
Some popular videoconferencing soft wares are-
AOL Instant, Messenger, Yahoo Messenger, MSN messenger, Microsoft Net meeting, iChat AV and Access Grid.
Acoustic Echo cancellation:
One of the main aspects of VTC systems is acoustic echo cancellation. It’s a method which is able to detect any sound reentering the audio input of the same VTC codec of which it came out.
Acoustic echo cancellation eliminates problems as reverberation-the other party’s sound thrown back at them, delayed transmission, or howling created while speaking.
Once the echo is detected it is deleted from the received or transmitted signal.
The general technique applied to echo cancel for improving the frequency of sound is a Digital Signal Processor (DSP) or it can be implemented using software.
Echo suppressors or echo cancellers are the devices used for acoustic echo cancellation.
The ITU (International Telecommunications Union) has three categories of standards for videoconferencing:
H.320- Used for public switched telephone networks (PSTN) or ISDN. Also used on dedicated networks like T1 and satellite-based networks.
H.323 – This is applicable for video over IP (Internet protocol) or voice over IP.
H.324-This is used in POTS (Plain Old Telephone System).
Impact of VTC:
Personal videoconferencing systems based on broad connection, web cams and software compression has become more affordable to people, so chat programs through free software has made video conferencing a popular option.
In the education field also VTC provides a platform to lecturers and students from all over the world to communicate and share information.
Children can also virtually visit places of interest and know about different cultures, nature and wild life.
Using VTC critical patients can consult doctors in case of medical emergency. Medical data and images could be transmitted using microscopes, video endoscopes, ultrasound imaging devices for quick treatment saving both life and money.
Standard VoIP in combination with desk top videoconferencing is used by businessmen to conduct meetings from any where without taking the pain to travel.
We look forward to various other scopes of growth that VTC has to offer us in the field of technology.