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?
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 (