Library items tagged:

Videoconferencing Traffic: Network Requirements

Anonymous
Saturday, January 21, 2012 - 16:09
Videoconferencing
H.323
This chapter aims to describe in some detail the demands that videoconferencing traffic places on the network, along with the metrics that can be used to predict – to a certain extent – the behaviour of a videoconference. Readers who may be less interested in the specifics of ‘Why is this important?’, and would like to move swiftly on to ‘What should I look at and do?’ are welcome to skip this section completely and move along to chapter 3.
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References / further information

Anonymous
Friday, January 20, 2012 - 17:49
Videoconferencing
standards
displays
formats
references
Digital Television by H Benoit, Published by Arnold ISBN 0-340-69190-5 The VGA standard: http://www.webopedia.com/TERM/V/VGA.html Plug and Display (P&D) interface: http://www.interfacebus.com/ The Digital Video Interface (DVI): 1. http://www.datapro.net/techinfo/dvi_info.html#Page01
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Displays within videoconferencing

Anonymous
Friday, January 20, 2012 - 17:48
Videoconferencing
displays
Room based systems generally use large picture and / or data monitors while lecture theatres will have projection systems. The CODEC (coder / decoder) will connect to these monitors either through a composite, an S-Video interface, or a SCART connector. Data displays for local and remote sites will normally use a VGA or DVI connection to the display device. Some monitors and most data projectors can handle both video and data signals.
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Display devices

Anonymous
Friday, January 20, 2012 - 17:48
Videoconferencing
display devices
The Video Display
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The video signal explained

Anonymous
Friday, January 20, 2012 - 17:48
Videoconferencing
signal
Video started life as an analogue signal and remained so for over 50 years. However, digital television via satellite, cable and terrestrial transmission is now rapidly replacing analogue. Digital signals are less expensive to transmit because more information can be carried within a given bandwidth using digital multiplex and compression techniques.
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Video displays, signals and formats

Anonymous
Friday, January 20, 2012 - 17:47
Videoconferencing
displays
signals
formats
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References

Anonymous
Friday, January 20, 2012 - 17:19
Videoconferencing
standards
references
H. Benoit Arnold, Digital Television. ISBN 0340691905 | 0471238104 GQOS: http://www.isi.edu/div7/rsvp/overview.html H.264: http://www.wipro.com/insights/mpeg4videocoding.htm IEC : http://www.iec.ch/ IETF : http://www.ietf.org/
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Guaranteed quality of service (GQoS)

Anonymous
Friday, January 20, 2012 - 17:18
Videoconferencing
standards
GQoS
quality of service
The increased popularity of IP (H.323) based services due mainly to the lower cost of connection has spawned a great deal of development to produce effective methods of delivering high quality videoconference (and telephone traffic) over the IP infrastructure. The Internet Engineering Task Force (IETF) has been particularly active in defining standards in this area while the major network equipment manufacturers have produced workable network solutions.
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Other standards

Anonymous
Friday, January 20, 2012 - 17:18
Videoconferencing
standards
other
The ISO and IEC standards bodies have formed two committees that have defined video/audio compression, namely the Joint Photographic Experts Group (JPEG) and the Moving Picture Experts Group (MPEG). These two committees have defined the JPEG, MPEG1, MPEG2 and MPEG4 standards. While these standards are more applicable to broadcasting and multimedia, some of the standards are used in videoconferencing.
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T.120 document and data sharing standards

Anonymous
Friday, January 20, 2012 - 17:17
Videoconferencing
standards
sharing
T.120
The main standard in use for data sharing within videoconferencing is T.120 Equipment that is T.120 compliant interleaves the data sharing information within the pass band of the H.320, H.323 etc. conferencing channel. This is an asset as sound, vision and data are shared across a single channel, but it can also be a hindrance as with low bandwidth channels, e.g. ISDN2, the T.120 data exchange part can degrade the audio and video signals to an unacceptable degree. For further information, see the VTAS guide, Data Sharing within Videoconferencing.
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