November 8-10, 1991 - Klofas.com

This type of highly compressed digital video
motion signal has sufficient quality for Amateur
digital video (ADV) contacts, and it is far more
suitable for relay through an Amateur satellite
transponder than conventional analog Amateur
Television (ATV) signals. ADV would
provide an acceptable signal to noise ratio and
link margins for Amateur ground stations without
the need for excessive power levels as recently
indicated for even low earth orbit activities
during the SAREX space shuttle video reception
tests. This is animportant consideration
when planning such future Amateur activities
from the space station. ADV could also provide
a type ofterrestrial video communications which
is considerably more spectrum efficient than
ATV.
Video Compression Technology
The evolution of video compression
Fig. 2
90Mbps
45Mbps
6Mbps
1.544
!nt:nframc
Rembrandt
Rembrandt 56
Motion Compensated DXC
,768
,354 Rembrandtll106
.056
.0192
ax Videophone
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'1975 1982 1985 1987 ]990 1991
THE EFFICIENCY OF FACE-TO-FACE COMMUNICATIONS
Meeting face-to-face generally provides the most effective means of interpersonal communications
for many purposes. The apparent reason for this, as researchers have observed, is that as much
as 80% of the communications which takes place in such meetings is non-verbal in nature. This
important observation is one of the driving forces behind the explosive growth in the use of digital
video teleconferencing bybusiness. Developments in the area of very large scale integration (VL5I)
and digital video compression technology are approaching the stage where radical changes in the
economics ofthe situation are about to take place. The day of the video telephone for interpersonal
communications, envisioned long ago, is no longer that far off.
So, why doesn't everyone own a video telephone now? The answer is cost effectiveness. The
technology exists. The trick is making it reasonably affordable. Even businesses with far larger
telecommunications equipment budgets than the average Ham, are seeing a rapid growth in voice
only or audio teleconferencing for conducting meetings. The reason for this situation is that
although video teleconferencing is the obvious choice, audio teleconferencing is less expensive and
IIgood enough" for the moment. As we mentioned before, developments in the fields of VL51 and
digital video compression are about to radically change the economics of the situation.
WHY DIGITAL VIDEO?
You have been watching a wide bandwidth form of digital video for years and may not have
realized it! To digitize an analog video signal takes about 92 Mbps. The national TV broadcast
networks take this digitized video Signal, compress it 2:1, and broadcast it totheir affiliated stations.
The digitalization and com pression of television broadcasts allows networks to send their programing
over special terrestrial circuits that handle the resulting 45 Mbps digital video signal. Digital
video compression at this level, when converted back to analog, retains all of the characteristics of
the original NT5C video.
You're about to see a lot more digital video! The high definition television (HDTV) currently
under ind ustry development and FCC review for the consumer entertainment television broadcasting
field is essentially a form of high bandwidth digital video. Commercial direct digital video
satellite broadcasting of movies and other forms of video entertainment was proposed to start this
past summer, but has been delayed. There is also serious consideration being given to replacing
conventional private analog business television (BTV) broadcasts, generally via commercial Ku­
Band satellites, for university educational seminars, product announcements, training programs,
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