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How to choose videoconferencing equipment


Important Videoconferencing Specifications

  • System type. One of the first decisions youíll make, in considering videoconferencing systems, is whether to buy a PC-based, portable, rollabout or installed system. These systems can be mixed on a network, and your choices will be determined largely by the size of the group participating at a given location. While any can be used by one or two people, the PC-based systems are meant for one; portables for two to eight; rollabouts for three or four to perhaps 15; and installed systems for five or six on up to 20 - 30 or more.

  • The size of the monitor or projector you will use relates closely to group size. PictureTel rollabout unitThough most videoconferences today take place using portable setups with 20" - 35" monitors, an economical, installed system using an LCD projector will be a much better solution for larger groups.

  • Bandwidth. In any teleconference, the video and audio signals must be compressed to move through telephone lines in real time. The quality of the image and sound you end up with are determined by the size, or bandwidth, of the telephone connection and the quality of the codec (or compression/decompression device) and the compression algorithm it employs.

    Most videoconferences today travel over two 64K ISDN lines, which moves data at 128 kilobytes per second (or 128K). At this bandwidth, decompressing to 15 frames per second video, you should expect a clean picture, but noticeable blurring of any person or object in motion. 384K is generally considered the minimum in applications where motion is critical, and 384K or higher at 30 frames per second is what you need if you will transmit videotape.

    More and more videoconferences are being held over wide-area computer networks using T1 or other digital lines. Bandwidths vary with the networks' capabilities, but it's not unusual to see transmissions at 768K or even 1.5 megabytes per second.

  • Compression algorithms are the software schemes that determine a codecís ability to fit what would be a huge amount of data into the relatively small capacity of an ISDN line. At one time, each codec manufacturer had its own proprietary standard and one brand of equipment could not talk to another. Today, however, the industry has come together to set standard algorithms, which allow smooth communication between systems. Some vendors, notably PictureTel, offer proprietary algorithms that operate in addition to the standard. Their codecs are set up to sense what systems they are linked to and choose the highest quality algorithm available to all.

    The algorithms your new system will recognize are an important consideration. Current systems all recognize the H.320 standard, but within that standard, H.261, H.263 AND H.263+ video compression standards may be recognized.

  • Audio quality. Research suggests that participants in a videoconference will perceive identical video pictures as of higher or lower quality, depending on the audio quality. Perceptions aside, in a lower-bandwidth transmission, in an acoustically imperfect room, or in a situation where one or two participants is connecting via a PC or telephone, audio quality can drop to the point where participants are just plain incomprehensible.

    To avoid these problems, you will want to be sure that your system includes full-duplex audio and digital echo cancellation (as do all of the systems in our on-line catalog). A critical specification for judging audio quality is frequency response, although, to a large degree, you'll need to judge a system's quality by hearing it during a demonstration.


Useful features

  • Multiple monitors or projectors. Generally speaking, you will want to be able to see two pictures at all times during your conference: one, the image of far-end participants and the second, a preview of what you're sending them. That way, you'll be able to maintain eye contact with the people you're conferencing with and be able to see how they see you or any documents you're sending. A single-monitor system will accomplish this with a picture-in-picture feature, putting the far end on the main image and the preview on the inset image. A two monitor setup separates the images onto separate monitors. That gives you larger images, which is always nice but especially useful as groups get larger.

  • In multiple location calls, you have two options. You can use a voice-activated switching device that will automatically show you the location where someone is speaking, or you can use "continuous presence" to split your screen and show a continuous image of each location in the conference. These choices are not a function of your system, but of the bridging system you'll use. Note, however, that if you expect to use the continuous presence option often, you'll want to plan for a larger than usual monitor or projected image, or the multi-screen images may get too small to be useful.

  • Multiple cameras can also be helpful, particularly if you have a situation (such as a distance learning classroom) where a presenter is in an area separate from the rest of the group.

  • A robotic camera will help you if your presenter might move around, as such cameras can follow him or her automatically. 3M VideoconferenceThis is normally an add-on to an installed system, but some portables and rollabouts use a voice activated camera to move the camera to the vicinity of the group member speaking.

  • Preset camera positions allow you to zoom and tilt your camera to four or more positions before your meeting begins, focusing in, say, on a particular speaker or zooming back to show the whole group. Then, with the touch of a button, you can move to that spot at the right times in your conference.

  • A document camera is a must in most videoconferences, allowing a presenter to make slides, transparencies, books or reports part of the flow of the meeting.

  • A telephone add-in allows audio-only participation by people using standard telephones. (Generally one person can connect using a standard phone line; multiple telephone connections are possible using a bridging service.)

  • A videotape input can also be quite useful, but remember, at lower bandwidths fast-moving images may be quite blurred at the far end of your conference.

  • A PC interface will allow you to add PowerPoint slides, diagrams or other computer images into your conferences.

  • A dataconferencing link allows conference participants to sit down at their own PCs and collaborate on a document or spreadsheet. An audio or audio and video connection completes the link and lets collaborators speak to each other and see each other while they work.

Beyond the specifications

  • Connectivity. Though most interoperability problems have been solved in recent years, mixing brands of videoconferencing equipment can be problematic. Before you purchase, itís important to make sure that the system you choose can connect to the systems you will commonly connect to.
  • Video and audio quality are difficult to judge from a spec sheet. Typically, the same-bandwidth systems will have very similar specifications, but they wonít all look or sound alike. Obviously, these are critical points to pay attention to in a demonstration.

  • The systemís controls should be easy, even intuitive, to use. They should put all devices at your fingertips, including near and far-end cameras and document cameras or other graphics devices. Remember that thereís a lot to control and that you may not always be able to train meeting participants in the use of the equipment in advance. Ask to try out all the controls during a demonstration and be sure you can easily become comfortable with them.

  • Reliability. Videoconferencing is a new enough technology that you can expect some difficulties and service concerns from time to time.

    You need to ask yourself the following questions:

    • Will your new system always work during a critical conference?
    • Does its manufacturer have a good reputation?
    • Is your dealer able to provide fast, reliable service?
    • If itís an integrated system, is your dealer able to service the projection, sound and control systems as well as the videoconferencing?
    • Do you have a supplier willing to take full responsibility for your system, rather than passing the buck to the telephone network supplier, manufacturer, or another systems integrator?

Videoconference