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How to choose videoconferencing equipment
Important Videoconferencing Specifications
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.
size of the monitor or projector
you will use relates closely to group size. Though
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.
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.
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.
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.
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
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.
camera will help you if your presenter might move around,
as such cameras can follow him or her automatically. This
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.
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.
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.
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.)
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.
interface will allow you to add PowerPoint slides, diagrams
or other computer images into your conferences.
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
Beyond the specifications
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
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.
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
Videoconferencing is a new enough technology that you can
expect some difficulties and service concerns from time to
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?