AN ISDN VIDEO APPLICATION (long) Plugging In the Info Highway - Here and Now

[David Farber <farber () central cis upenn edu>]

From: kirsh () io org (Harris Kirshenbaum)


The following article is about to published in a couple of magazines, and it
is uploaded here for anyone who might be interested.  It discusses the FIRST
(to be best of our knowledge) application of ISDN to carry live, full-time
color video monitoring.  The authors welcome any questions to this e-mail
address.














Plugging In the Info Highway - Here and Now


 Andrew Young and Harris Kirshenbaum - 1994






"It can't be done.  Or at least, you won't like the results."


That's been the traditional response to those looking to send video over phone
lines.  And as talk of the Information Superhighway fills the daily press, we
keep reading of its ability to deliver all of data, text, audio and video at
very high speeds.  Our company, KM Video and Security of Toronto, was
fortunate to find a customer who needed an unconventional solution, a local
telco willing to cooperate, and a supplier on the leading edge of video
communications, and to bring them together into a successful new application.


GO Transit, an extensive commuter bus and rail network serving the City of
Toronto and surrounding areas, is operated by the Government of Ontario.
Already a user of conventional CCTV systems at their 50 outlying stations in a
50-mile radius, the customer wanted to expand the system to monitor remote
stations from their operations center in downtown Toronto. While the basic
CCTV systems were installed primarily for local staff to monitor platforms,
escalators and tunnels, this expansion would allow central monitoring of the
stations and, more importantly, of the trains themselves.  Since operators
would have to quickly and accurately read identification numbers from the
sides of moving trains, system requirements would be rigid indeed.


Color was deemed essential to the system, as the identification of moving
trains needed the extra information offered by a color picture.  The majority
of cameras in the security side of the system are already color.  GO Transit
has many examples of the information delivered by color CCTV assisting in
their security operations.


Pictures would also have to be sharp and clean, with refresh rates high enough
to deal with large objects moving rapidly and still provide details of vehicle
speed, passenger load and track safety conditions.


Many of the existing systems had upwards of 16 color cameras each (Panasonic)
utilizing matrix switching (American Dynamics) and/or multiplex recording
(Panasonic). In addition, consideration had to be given to add pan/tilt and
zoom capability in the future.






GETTING THE PICTURES ON LINE


The transmission of high quality video signals over long distances via
telephone lines presents a huge challenge.  The challenge can be better
understood when we take a look at what is involved.  One second of high
resolution color video, when digitized, can occupy in excess of 90 Mb on a
computer hard drive. It would require over 1000 digital telephone lines to
transmit this signal in real time.  Economically this is out of the question.
Various techniques have to be used to reduce the information in the video
signal before transmission.


In the early days of slowscan, signals were moved by transmitting one frame of
reduced resolution video about every 20-30 seconds in black and white only. In
those systems for every frame transmitted approximately 900 frames were
ignored (30 frames per second x 30 seconds).  If a faster update time was
offered resolution suffered still further.


Over the years, technology improved and demand for remote video monitoring
increased. This led to more manufacturers becoming actively involved in
developing new equipment. Today, we see systems from Robot Research Inc. and
American Dynamics (among others) that are capable of transmitting black and
white full screen images in under a second when connected to the new digital
networks such as ISDN (Integrated Services Digital Network).


ISDN is a dial-up digital service presently offered by the telephone companies
(telcos).  It represents a dramatic improvement when compared to the slowscan
equipment mentioned above, which operated on standard voice grade phone lines.
 By comparison, ISDN offers greater bandwidth and therefore higher speed of
data flow.  As the backbone of the telco's approach to the Information
Highway, ISDN is economical (a fraction of the voice line rate), reliable in
that it is all modern and utilizes digital switching, and available in a
surprising number of locations.


Diane Tosh, Product Manager for ISDN with Stentor (the association of Canada's
major telcos) said, "We are now experiencing sizeable demand for the
applications best suited to ISDN such as video conferencing and monitoring,
remote access to LANs and desktop multimedia.  As a result, hardware and
software vendors are generating products to satify this demand.  The Stentor
Alliance Companies are deploying ISDN capabilities at a faster rate."






THE PIVOTAL DEVICE - A CODEC


Still, CCTV applications like the one for GO Transit require even better
performance than the traditionally CCTV-only oriented manufacturers have to
offer. A codec may be the answer. A codec is a piece of equipment normally
used in video conferencing systems. Codec stands for CODer-DECoder, and is
equivalent to a modem which connects computers through phone lines by
converting data to audible signals.  The Codec simultaneously transmits and
receives the video, audio and control signals required for a video conference,
arranging all the data into packets that can be handled by the ISDN network.


For some, the term video conferencing conjures up thoughts of highly
sophisticated boardroom environments using complicated equipment connected to
even more complicated high speed networks.  There are many video conferencing
systems on the market today that range from the much talked-about desktop type
(PC based) up to systems capable of full motion broadcast-quality
transmission. Codecs convert analog video signals into a digital format
represented by ones and zeros.  Mathematical codes known as algorithms are
then used to represent the original signal in a compressed form.  Hence the
term compression.


In the past, the high capacity digital telephone lines required for video
conferencing were prohibitively expensive. In addition, these lines did not
offer dial-up capability so important for remote CCTV monitoring. In short,
video conferencing codecs did not lend themselves well to CCTV applications.
Several elements have fallen into place to change that situation.


The availability of ISDN service together with the new WG-V510 Codec from
Panasonic were combined to solve the video transmission problem at GO Transit.
 Installed and operating, the system automatically establishes its connection,
and delivers color motion pictures at the required level of resolution to
serve the purpose.






DEMANDING REQUIREMENTS


All the parameters that push any video transmission system to its limits were
present in GO Transit's requirement. i.e.


Transmission of color.


Fast, full-frame switching between cameras.


Viewing scenes where movement fills the screen.






Color requires more bandwidth than black and white, since there is more
information in each frame of video.  Fast, full-frame switching between
cameras means the initial transmission of completely different scenes must be
almost instantaneous.  The system cannot rely on a compression mode that
assumes only slight alteration between pictures, as earlier ones did.  Viewing
scenes where movement virtually fills the screen, and even more demanding
panning, tilting, zooming and focusing of cameras, tests motion handling
capability, again because of the way early compression schemes worked between
successive frames, rather than only within individual frames.


The Panasonic WG-V510 Video Codec connects directly with up to 3 BRI (Basic
Rate Interface) lines on the ISDN service, allowing dial-up operation at
speeds from 64Kbps up to 384Kbps.  Each BRI provides two "B" channels that
transmit video, audio and data at 64Kbps each, and one "D" channel that
transmits signaling and control for the "B" channels at 16Kbps.  BRI is often
referred to as 2B+D for this reason. This transmission speed, in addition to
the sophisticated video compression techniques of the codec, provided the
technical solution to GO Transit's remote monitoring problem.


> From an operating cost viewpoint, BRI lines are also much cheaper than the
older technology Switch 56 or T1 lines which are other services offered by
telephone companies and used for video conferencing.  It is ironic that the
less expensive ISDN service also offers higher quality.






OPERATING COSTS COMPARISON (in Cdn $ at 1.40 to $1 US)










                            ISDN @ 128 kbps            Switch 56 @ 112 kbps


Monthly Rate                $78.00                     $152.00


MT-1 Terminators            $17.00/month               n/a


56 kbps Data Units          n/a                        $110.00/month


Telco Install Charge        $261.50                    $790.00






1st year Costs Total        $1401.50                   $3934.00










Notes:1. Some codecs may require additional CSU, MUX, I-MUX
              other accessories.


2. Rates in effect as of March, 1994 for Metropolitan Toronto.


3. In Canada "Microlink" is Stentor's trademark for BRI Service.






Control of the remote CCTV systems is straightforward.  As mentioned earlier,
matrix switchers from American Dynamics were already being used in the
systems.  These are the AD-2150 type with RS-232 inputs.  By connecting an
AD1678CM keyboard to the serial port of the Panasonic Codec at the receiving
site, and connecting the codec and matrix switcher in the same fashion at the
transmitting site, full remote control of the CCTV system was a reality (see
system block diagram).  One of the monitor outputs of the matrix switcher is
connected directly to the codec.  Through programming, local operation of the
system remains unaffected by the distant site.


Installation of the system took place in November 1993. With 24-hour daily
operation now into its 7th month, the system has exceeded the customer's
expectations with regard to picture quality, reliability and ease of use.  The
GO Transit system has become a model for other commuter rail operators, and is
the first full-time use of the ISDN network for video monitoring in North
America.


This affordable method of transfer of information at high speed is now a
reality.  Manufacturers of phoneline video transmission systems from both the
security and video conferencing industries are well aware of this. Indeed,
some now mention the connection to ISDN in their product specifications. This
comes as great news to both users and video systems professionals involved in
CCTV and all modes of video communications.






- end -






Andrew Young is Codec Product Manager for KM Video and Security


in Toronto Canada.  He has over 17 years experience in the electronics


and CCTV fields.  He works with end users and manufacturers designing


effective surveillance and other video solutions.






Harris Kirshenbaum is a Toronto writer and communications consultant


who contributes regularly to magazines for Multimedia and


Video Professionals




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