AOH :: P09-08.TXT

Introduction to Videoconferencing


                               ==Phrack Inc.==

                    Volume One, Issue Nine, Phile #8 of 10

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

                     "Introduction to Videoconferencing"

                             by Knight Lightning

                              Written On 10/3/86

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Hi, KL here welcoming you to a look at Videoconferencing.   This is a
relatively new field that definitely bears investigation as videoconferencing
is only a step away from everyone having video communication in the home. Well
enough is enough, I hope you enjoy the file --KL.
______________________________________________________________________________

Despite the growing use of videoconferencing, confusion still exists regarding
what it can and cannot do.  This file should begin to help answer some of the
questions about videoconferencing and perhaps formulate new ideas as well.
Videoconferencing is not just one thing.  It takes several different forms and
can be designed in many different ways.  Most of these ways are probably still
waiting to be discovered.

First of all, there are two main categories of videoconferencing.  There is
Point-to-Point and Point-to-Multipoint.


Point-to-point/Two-Way Videoconferencing
----------------------------------------
Two-way videoconferencing enables people to conduct meetings even though the
participants are in separate locations.  Using interactive video and audio
equipment, participants in one location can see, hear, and interact with
colleagues in another location.

The most familiar example occurs regularly on TV.  When a newscaster in
Washington interviews a head of state on the opposite side of the world
"live," that's point-to-point, full-motion, full-color videoconferencing.


Point-to-multipoint/One-Way Videoconferencing
---------------------------------------------
The one-way videoconference allows an organization to present video
information to large audiences in multiple locations at the same time.

One-way videoconferences are very different from two-way videoconferences in
purpose and in implementation.  Two-way videoconferences allow small groups in
two, or possibly several, locations to interact audio-visually.  In contrast,
one-way videoconferences are designed to provide a one-way audio-visual
presentation of information from an originating site to audiences at numerous
receiving locations.

The remote "audiences" are not seen by the initiators of the presentation.
However, since both types of videoconferencing take place in real time, live,
the audience can participate over the phone.

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

There are two variations on the above listed categories of videoconferencing;
Full-motion videoconferencing and freeze-frame videoconferencing.  Each
carries its own set of system requirements and each accomplishes quite
different tasks.


                        FULL-MOTION Videoconferencing
                        -----------------------------
Full-motion videoconferencing is like watching television.  You can see
participants in another location in color and in "real time" motion.  You can
identify who is present (provided that they are within camera range) and who
is speaking.  You can see facial expressions, hand gestures, and general body
language.  Motion video is used primarily for images of people.


Motion Transmission On Wideband Channels
----------------------------------------
There is far more information in moving pictures then in a still image.
Consequently, the size of the communications channel required to transmit and
receive motion is far greater than that required for a still image.

Transmission of a television signal in its original analog form (as it would
come from a TV camera), requires terrestrial television channels or a
satellite transponder.  Terrestrial television channels are not readily
available for occasional corporate use; satellite transponders are available.

Most systems therefore, incorporate digital compression techniques to reduce
the bandwidth required for motion videoconferences.  Example:  An image in
motion is refreshed on a television screen 30 times per second.  This means
that the bandwidth necessary to transmit the image is very high, usually 1.5
megabits per second (Mbps).

This bandwidth is beyond the capacity of the standard telephone cable.  A
device called a "codec" digitizes the analog television signal and compresses
it by eliminating redundant information.  Currently, codecs can reduce the
bandwidth to 56 kilobits per second (Kbps) and it is hoped that this bandwidth
can be compressed even further.

The resulting signal can be transmitted over less than full bandwidth
channels. The picture is of somewhat less quality than the original analog
image, but more than sufficient for most meetings.


                        FREEZE-FRAME Videoconferencing
                        ------------------------------
Freeze-frame videoconferencing is like a slide show.  It captures still images
either in color or black-and-white.  Freeze-frame "stills" of people seem
unnatural and can be distracting.  Yet, freeze-frame video is best for still
images of three-dimensional objects such as a product or a part, and for
charts, drawings, graphics, and specially prepared presentation material.


Freeze-Frame Transmission On Narrow Band Channels
-------------------------------------------------
A freeze-frame system captures an image by stopping, or freezing any motion
that might be present.  The image can be transmitted via analog or digital
signals over narrow channels.  These channels are considerably narrower than
those used for full-motion video conferencing.  In its simplest form,
freeze-frame video can utilize ordinary telephone line transmission.  A single
freeze-frame image will require at least 30 seconds to a minute or more for
transmission.

In some systems, the freeze-frame image is displayed line by line as it is
received.  This creates a vertical "waterfall" effect or a horizontal scanning
effect.  In other systems, the incoming lines of picture information are
stored in a buffer until the completed picture can be displayed as a whole.
In still other systems, an image emerges in successively better resolution as
additional picture information is received.


Enhancements To Freeze-Frame Video Systems
------------------------------------------
There are a number of ways to expand a freeze-frame video system's
capabilities.  One enhancement is telewriting.  With a "pen" connected to a
telewriting device, users can point out a portion of a freeze-frame video
image, overlaying lines and markings in various colors that are displayed at
all locations as they are drawn.  Some telewriting devices include stored
geometric shapes, logos, and symbols that can be transmitted as overlays to a
freeze-frame image.  Zoom capability enables close-up analysis of portions of
a display.

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

               Personal Computers and Desktop Videoconferencing
               ------------------------------------------------
Personal computers are beginning to be increasingly used with freeze-frame
videoconferencing.   PCs are used for control, for the creation of graphics,
and for storage and retrieval of graphics material.  There are signs that this
evolution towards desktop videoconferencing has already begun.

The MINX (Multimedia Information Network Exchange) work station, recently
announced by Datapoint Corporation, combines a camera and speakerphone with a
high-resolution-color video graphics display screen.

The MINX can be configured with Datapoint's Vista-PC or with the IBM PC, AT,
or XT, in which case the PC monitor is replaced by the MINX.  A mode key on
the workstation permits the user to shift between the video communications
mode and the normal PC mode.

Another indication of this revolution is provided by Northern Telecom
(creators of DMS-100, 200, & 250), which recently added Meeting Communications
Services (MCS) to its Meridian DV-1 voice/data system.  This option allows up
to 24 participants to conduct simultaneous audio communication and up to eight
participants to view, modify, and exchange data using Meridian M4000
integrated terminals.

A third and final example is the Luma phone from Luma Telecom.  This device,
which uses regular phone lines, combines audio with black-and-white
freeze-frame video on a three-inch-diagonal screen.  Strictly a telephone
product, the Luma phone has no computer features and will not transmit data.
For more information on the Luma phone, please see the November, 1986 issue of
The Sharper Image catalog.

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Videoconferencing is the way of the future and its only drawback is that of
economic cost.   Increased use of videoconferencing will depend a lot on the
adoption of the Integrated Services Digital Network (ISDN), a standard,
all-digital communications service promised by the regional Bell Operating
Companies (BOCs).

ISDN will offer users 144 Kbs or more which can be allocated among various
communications tasks--data, voice, or video--in whatever proportion is
necessary.  This means that the available bandwidth could support simultaneous
audio and video communication.
______________________________________________________________________________

References:
----------
"Electronic Meetings:  Substitutes With Substance?," by Sam Dickey, Today's
 Office, July 1986.

"Getting The Full Picture On Corporate Videoconferencing," by Marita Thomas,
 Facilities Design & Management, June 1986.

"The Lid Is Off ISDN," Tomorrow's Communication Connection, April 1986

"Videoconferencing;  An Alternative Solution," Corporate Informations Systems,
 General Electric (GE).
______________________________________________________________________________

Onto the next generation... --KL

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


===============================================================================


AOH Site layout & design copyright © 2006 AOH