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Security Video Utilizing A LAN: The
Network Camera
Digital
video is already ubiquitous in our society.
It started with satellite TV. It
was not feasible to broadcast their product in analog format. Signal compression techniques (MPEG), which
are now commonly used to broadcast HDTV and show video on the Internet, were
pioneered by the satellite TV companies.
Digital
video has also been introduced in video security. Unless you buy old equipment, you are
unlikely to deploy a completely analog video security system today. Digital technology has made pure analog video
security technology virtually obsolete.
The digital video recorder (DVR) replaces what would have been a VCR a
few years ago. Almost all systems now
include the ability to view the video from your cameras over a computer network,
including the Internet.
The
current debate concerns the Internet Protocol (IP) camera. It is important to note the difference
between a “web camera” and an “IP camera”.
A web camera generally connects to the USB port of a computer and
utilizes the resources of the computer to function, but an IP camera is
independent of a host computer, at least to a degree.
IP Cameras: The Future?
There
is a certain amount of inevitability to the IP camera. The question is when, not if, the IP camera
will come to dominate the security camera market. IP camera installation is easier because the
network cabling is less expensive and much less bulky than the coaxial cable
normally used for analog cameras. There
is a certain presumption that anything digital will be better than its analog
alternative, but in this case, the reality is more complicated. Like most new technologies, a certain amount
of “oversell” by the IP camera companies marketing their products should be
expected. It is important to recognize
the issues associated with IP cameras.
IP Cameras:
Problems with Current Implementation
IP
camera technology does have its problems.
The first issue is expense. IP
cameras with comparable image quality are still significantly more expensive
than an analog alternative. The second
issue is that the bandwidth needed to communicate the video is a challenge for
conventional networks if more than one or two cameras are employed. When making comparisons between analog and IP
cameras, similar image quality specifications should be used, otherwise the
decision will based on the novelty of the technology, not the performance.

An IP
camera can be found at about the same price as an analog camera, but not if the
two cameras have comparable performance.
For example, IP cameras generally have less impressive low-light
sensitivity specifications (1-4 Lux typical) than analog cameras (0.001-0.8 Lux
typical). Excellent quality IP cameras
are available. The Cisco 2500 has a sensitivity of 0.4 Lux with more than 100
dB dynamic range, but the Cisco 2500 retails for more than $800. A comparable analog camera would sell for
less than $300.
The
other problem with IP cameras is the signal bandwidth needed to link the camera
to the system network. It is feasible to
install an IP camera on an existing network, but the impact multiple cameras
will have on your system’s network performance should be considered, especially
if many cameras are to be installed. If
a dedicated star network topology (home runs) is to be installed solely for the
use of the cameras, then this problem may be avoided.
A single video camera with a resolution of 640x480 pixels at 30 frames per second (M-JPEG) requires about 8 Mbit/second of bandwidth. For comparison, the Ethernet (10BASE-X) specification is 10 Mbit/s maximum.
There
are two approaches to the use of IP cameras.
The first approach converts the video signal from analog to digital at
the camera. This camera will incorporate
enough computational ability to function in a network environment, including an
operating system stored on a small flash memory module.
The
second approach takes the first approach a step further. This approach digitizes the video, but in a
decentralized macro system design. This
camera includes the ability to truly operate independently. It can store video until needed, and it has
true video analytic capability (artificial intelligence). With this artificial intelligence, if an
alarm condition exists, the camera can make this determination, and contact the
host.
IP Alternative:
Digitized Video
Digitized
video is the more common approach currently.
With this design the digital camera captures the image, and constantly
communicates the video as a digitized signal over a computer network to a video
server (computer). The server owns the
responsibility for processing and storing the video. Even though the camera must have some
computation capability to communicate over a network, it has little if any
on-board capability for logic functions and storage. Remember that video will require a
significant microprocessor, RAM, and video storage for even limited
manipulation.
IP Alternative: Decentralized Logic
If
sophisticated decentralized processing (video analytics) could be
cost-effectively deployed on IP cameras, the transition to IP cameras would be
dramatically accelerated. A few
companies have introduced digital cameras that have integrated web servers so
that no external computers are needed for communication, but this is different
from the ability to analyze at the point of capture and store the video
locally.
On-board
logic and video storage would eliminate the need for all video to be constantly
communicated to the host, and would solve the bandwidth problem. Video that needed to be reviewed could be
requested by the host only when needed.
There
are cameras available with these features, but they can be very expensive. Sometimes these functions are added in a
separate module local to the camera called an “Intelligent Video Server”. An example of a design with logic and
storage are some of the cameras offered by the Swedish company Axis
Communications (Note: not all cameras
from Axis are suitable for a decentralized logic system).
When
large systems of IP cameras are employed, if a dedicated star topology network
is not employed, compromises will need to be made to reduce costs and bandwidth
requirements. The resolution and
frame-rate are the most common compromises.
A
survey of technology professionals estimates that the IP camera will become
dominant when there is less than $100 difference from the analog camera. As the price of technology continues to drop,
the IP camera will be more competitive, but it could take many years.
About
the Author: Brian Bradshaw is
General Manager of B.V. Technology. He
is an InfoComm Certified Technology Specialist (
Website: B.V. Technology