Videoconferencing FAQs

What standard has been selected?

The H.323 standard for Internet Protocol (IP) videoconferencing has been selected as the standard for the statewide network. However, all other videoconferencing standards such as Analog, MPEG 2, and H.320 will be able to communicate through the use of video bridges (multipoint control units) and gateways.

Why was this standard selected?

H.323 is a relatively new videoconferencing standard that can be delivered over the Internet at an economical cost. H.323 systems can connect with each other for point-to-point conferences, or they can be scheduled on a network such as the North Dakota Interactive Video Network (IVN) for point-to-point or multipoint conferences.

How does it work?

The H.323 standard works very much like the other videoconferencing standards. The main difference is that H.323 uses the Internet to establish connectivity. Conference systems that are easy to use and provide good quality audio and video are also available at a moderate cost.

What is the difference between Analog, MPEG 2, H.320 and H.323 video?

Analog - is high quality audio and video similar to standard television today. In contrast to new digital systems, analog cannot be transported long distances without using repeaters, which tend to result in degradation of the signal. Analog video requires high bandwidth because the image from the video camera is transmitted directly to the TV monitors at the receiving sites. K-12 consortiums, which use analog video usually have a full fiber optic cable (dark fiber) dedicated to that use.

MPEG 2 - (Moving Picture Experts Groups) is a series of standards for digital video and audio designed for different uses and data rates. It is high quality, but requires at least two T1 telephone lines for the minimum bandwidth (800 MB). Higher quality MPEG 2 video can be achieved if more bandwidth such as a DS3 is available to connect each site. MPEG 2 is the standard used in DVD video players and in the new North American Digital TV system.

H.320 - this standard is a suite of specifications that define how video conferencing systems communicate over dedicated lines such as ISDN (dial-up), T1 or Switched-56 lines. H.320 is excellent quality digital compressed video that requires less bandwidth than Analog or MPEG 2 and can be transported easily over long distances.The standard can be used at a variety of data rates ranging from 112 KB to full T1.

H.323 - this standard extends the H.320 digital standard for use with Internet
Protocol (IP) videoconferencing. It can be used on an ATM network (similar to STAGEnet) at various data rates (124 KB to ½ T1). Good quality audio and video is achieved with this standard at ¼ T1(384 KB) if Quality of Service (QoS) is provided for the sites that are connected into the videoconference. Without QoS, the quality of the audio and video often fluctuates dramatically depending upon the traffic on the Internet circuits being used for video at that time. An advantage of H.323 is the ability to utilize a portion of a T1 circuit for video and simultaneously use another part of the circuit for other data such as Internet access and E-mail. Another advantage is the ability to utilize a personal computer or a moderately priced conference system for H.323 video.

How many sites can be connected at one time?

The number of sites that can be connected depends upon the number of events scheduled during that time and the number of ports on a bridge. It is not practical to schedule more than six to eight sites for a class or meeting if you plan to encourage participation at each site. Maximum number of sites for a single event is 12.

How many sites can be viewed?

Typical videoconferencing is set to the voice activated mode. Sites will switch on the monitor when someone at another site speaks. Another format that can be used upon request is the continuous presence format. A number of sites can be viewed on one screen depending upon the number of sites in the connection.

Quality of Service

What is Quality of Service (QoS)?

Quality of Service (QoS) refers to the ability of the network to guarantee that packets in a video stream will be delivered to their destination without delay and arrive in the proper sequence. This allows for high quality audio and video between all endpoints (sites) in the IP videoconference. Without QoS video competes with data for bandwidth and the quality of the video can be seriously impacted.

How does my site ensure Quality of Service?

Arrangements must be made with ITD to assure Quality of Service. At the school site you can assure maintaining QoS by following some simple guidelines that will be provided by ITD. They will include connecting the video equipment directly to the equipment the state provides and by using high quality wire such as CAT6 or better.