Video Security System (VSS) Design Guide
This guide has
been developed to assist customers with those decisions that are needed to
successfully plan a video security system.
The guide does not pretend to be comprehensive, but rather, the goal is
to provide a tool that initiates a fruitful conversation between the customer
and the professional.
Video security
has changed dramatically in recent years.
The events of 9/11 have led to dramatic improvements in the
technology. Coupled with the growth of
computer technologies, the industry, once dominated by “burglar alarm”
companies, is increasingly supported by the IT professional.
Questions that are
Relevant to Almost Every Video Security Application:
What
is the purpose of the project?
How
many cameras will be needed?
What
type of camera is the best for each application?
What
type of video management system is appropriate?
What is the Purpose of
the Project?
Too often, a
video security project is begun without a clear objective. It is normal to have multiple
objectives.
An example of a
video security project is the use as a “Vehicle
License Plate Recorder”. This is an
example where what would seem to be a clear objective, still needs
clarification. The folks operating the
some of the nation’s toll roads use automatic license plate cameras on some
roads to document the vehicle’s use.
This application is much different than a project whose aim is take
pictures of each vehicle entering a parking lot, so that this video could be
reviewed later if needed. If one had the
second objective, and priced a system for the first objective, he would likely
be discouraged (more
information on License Plate Cameras).
How Many Cameras will be
needed?
The number of
cameras will directly affect the attributes of the video management
system. The design of video security
systems is usually based on monitoring key assets and chokepoints, for example
building entrances.
Chokepoints are
an efficient method of documenting the movement of individuals. Chokepoints can include hallways, parking
lot driveways, and entrances to common areas.
Key assets
include items that are both of significant value, and are subject to
abuse. For example, one customer used a
manufacturing process for their production that used a platinum “target” that
weighed several pounds. The machine that
used this component, as well as the storage of spare components was monitored
by their video security system. Even
though the component was worth more than a year’s wages for most of the
workers, the monitoring system kept honest people honest.
The number of
cameras will directly affect the video management plan. For these purposes, it is better to “pad” the
estimate, as it is normal for new needs to evolve.
What Camera Technology is
the Best Choice for each Application?
Conventional
vs. Infrared (IR): The night-vision (IR) camera is
currently very fashionable. Countless
packages from the manufacturers include a set of IR cameras. There are applications that are best solved
with this technology, but it is currently a common mistake for the IR camera to
be used indiscriminately. Most IR
cameras have a range of only 50-60 feet in night-vision mode. The range is proportionate to the amount of
IR illumination provided by the camera, usually with IR LEDs (more
information on night-vision). If
your field of view has at least a little light, a conventional camera with
auto-iris functionality can offer superior performance (demonstration).
Fixed vs.
IP
vs. Analog: Most modern
video security systems are now digital. The difference with the IP camera is that the
video signal is digitized within the camera.
This makes it possible to interface with the camera with
Lens: The
first decision is whether to use a manual iris or an automatic iris lens. If the camera is indoors with constant
lighting, a manual iris is fine (and less expensive); otherwise an automatic
iris is strongly recommended. Outdoor
lighting intensity can typically vary by a factor of 10,000. Focal length is the other important lens
decision. As the focal length gets
smaller, the field of view increases, but makes for a more distant view. Adjustable focal length lens can be
varied.
*
The selection of cameras is critical to the success of your
project. Everything else in the project can
be done well, but with the wrong cameras, it is a wasted effort.
What
Type of Video Management System is Appropriate?
Video
management systems are the logical center of the video surveillance system,
receiving data from the cameras, storing the video, and interfacing with the
rest of your information system. At
installation, this system’s importance will not be obvious, but as you utilize
the system, this module will become very familiar.
All modern
video management systems have at their core a computer. Some systems use a generic P.C. with video
acquisition hardware added. This is
usually the cheapest and most versatile option, but is also the most
maintenance intensive, and least reliable.
The other
option is a digital video recorder (DVR), which indeed includes a
computer, but the computer is not a generic P.C., but is instead is an embedded
computer with hardware and software designed specifically for the job of
managing a video security system. A DVR
is unlikely to be compromised by a computer virus, or conflict with other
installed software. Most modern DVR
systems support Internet protocol, which means that the system can be connected
and share video with the organization’s information network.
If you choose a
DVR, the software will be bundled with the hardware, and the software
attributes should be a prime consideration in the selection. If you choose to utilize a P.C. as the host
of your video management system, then the software used to process the video
should be chosen carefully. It is
important to understand how your system will be utilized. The most common use of surveillance video is
for historical investigation. Well
designed software can prove invaluable during this work.
The use of
computer software to identify possible important events is called Video
Analytics. At large airports and
other venues, sophisticated software looks for suspicious behavior, such as the
abandonment of a package, or even someone unusually nervous. A more common (and less complex) application
for the average user is motion detection (more
information on video motion detection). With a motion detection log, the review of
video of a normally quiet environment can be performed much more quickly (more
information on video analytics).
Video data
storage design is an important decision.
Video storage will account for a significant portion of total system
cost. The software used for the storage
will allow the efficiency of the storage to be increased dramatically. MPEG-4 (and a subset of MPEG-4, H.264)
is the most common algorithm used (more
information on video compression).
A single camera can consume 7 GB of storage per day. Most organizations store 30-60 days of
video. If the system has 10 cameras, 60 days
of storage could account for more than 4 terabyte of memory consumed (more
information on video storage).
About
the Author: Brian Bradshaw is
General Manager of B.V. Technology. He
is an InfoComm Certified Technology Specialist (