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Video Conferencing

What is video conferencing?

Videoconferencing is a form of communication that allows real-time interaction between people at two or more physical locations - that is, it allows for two-way video and two-way audio interaction through the transfer of video and audio packets via telecommunications. Some types of videoconferencing equipment allows users the ability to send and/or share data during the videoconference.

How is videoconferencing different from teleconferencing?

Videoconferencing should not be confused with satellite teleconferencing as the two involve different transmission media and different modes of interaction. The most important distinction to remember between the two is that videoconferencing allows for real-time interaction among participants while teleconferencing allows for limited interaction. For more detailed information about teleconferencing, please visit the satellite teleconferencing page.

How does videoconferencing work?

Videoconferencing equipment allows audio and video (and perhaps data) packets to be exchanged through telecommunications lines between two or more sites. Videoconferencing can occur over ISDN lines or IP-based lines. ISDN-based videoconferencing conforms to the H.320 standard and IP-based videoconferencing conforms to the H.323 standard. If T1 lines are used for the videoconferencing network, they have the disadvantage of being dedicated to and from fixed points, whereas ISDN lines can dial in to other networks. While it is true that an IP-based network could videoconference over the public Internet, there is no guaranteed quality of service on the public Internet so videoconference quality may be inconsistent. One main benefit of IP-based videoconferencing are fixed monthly costs, as opposed to per minute long distance fees incurred by the use of ISDN lines.

Theoretically, any two videoconferencing systems with the same standard (regardless of brand/manufacturer) should be able to conduct a basic videoconference. If videoconferencing systems with opposing standards would like to videoconference with each other, another piece of equipment called a gateway must be used. In order for a videoconference to occur between more than two sites at one time, a piece of equipment called a Multipoint Control Unit (also known as a bridge or an MCU) must be used.

What is a point-to-point videoconference? What is a multipoint videoconference?

A videoconference between two sites is called a point-to-point videoconference. A videoconference between more than two sites is called a multipoint videoconference.

A multipoint videoconference is a videoconference involving more than two sites. This page contains more information about multipoint videoconferences and may be of special interest to presenters of multipoint workshops or moderators of multipoint meetings.

Multipoint Videoconferencing Modes

There are two modes, or formats, for multipoint videoconferences.

  • Continuous Presence (CP)
  • Voice Activated (VA)

The facilitator/presenter should indicate to participants which mode has been chosen for the event and participants should follow the tips for that mode accordingly.

Continuous Presence (CP) Mode

  • All sites in the videoconference can be seen at the same time on the far end monitor(s)
  • A site will see themselves (or any data that they present) on their right hand monitor AND they will see themselves IN ADDITION to everyone else represented in small sections on the far end monitor(s)
  • This mode IS NOT OPTIMAL for displaying data (document camera, smartboard, etcetera) as the data will not occupy an entire screen -- the data presented by a particular site will be limited to the screen size to which that site is relegated. Depending on the number of sites in the call, the data may be too small to be legible by other sites in this mode. If data must be relayed to the far end sites and the continuous presence mode must be used, it is best to send data via another method (email, fax, snail mail) to remote sites prior to the videoconference
  • If you begin a multipoint conference in CP mode and switch the mode of the conference to VA (voice activated mode) during the videoconference, the picture quality will be poor. It is better to terminate a continuous presence conference and re-connect it in voice activated mode to ensure best picture quality.
  • Microphones at all sites can be active, if needed, during a continuous presence conference but be aware that it can get quite "noisy" if too much sound is produced by all sites. If an echo becomes a problem, this means that one site has their volume turned up too high or their microphones are too close to the front units. The facilitator/presenter should have each site mute their microphones and bring sites back into the call one at a time until the site with the volume/microphone placement issue is identified and the problem can be corrected.

Voice Activated (VA) Mode

  • Only the remote site which produced the most recent audio will appear on the far end monitor(s)
  • All other remote sites in the call will be invisible but can appear on screen when they produce audio
  • You will see yourself (or any data you present) on the right monitor at all times
  • If you are the speaking site, you (or any data that you present) will appear on the remote sites' left monitor
  • When a site would like to speak in this mode, they should begin speaking but will need to realize that it will take a few seconds of audio production before the camera will switch to them. All other sites should remain muted to allow the screen to switch to the speaking site.
  • Microphone settings are CRITICAL in this mode -- sites should have microphones muted/inactive when they are not speaking in order to prevent themselves from appearing on screen due to insignificant "noise" such as paper rustling, sneezing, coughing, etcetera
  • Facilitation/moderation is highly recommended for large meetings or workshops in this mode as the moderator can call on particular sites to encourage participation. A moderator may introduce agenda items or topics and then call on each site individually to record comments from those sites. After the moderator has called on all sites, he/she can ask if there are additional comments before moving on to the next agenda item or topic.