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CCTV
Systems
By John W. Colley
Grill
The CCTV Expert
September
2004 Issue
View
The Grill The CCTV Expert Archives
The digital recording industry has literally hundreds of manufactures
that are offering a digital recording from commodity to specialized
performance. When we look into the manufactures specifications
many of the specifications talk about CIF. First of all what
is a CIF and how do they effect performance specifications.
An explanation in broad terms and not getting to technical
CIF means Common Image Format. If we look at the best resolution
a CIF can produce you start to see the loss of resolution
proportionately. An example of resolution in the various formats
is as follows: D1 Resolution H480 X V330, CIF 4 Resolution
480H X V330, 2 CIF Resolution 480H X V162, CIF Resolution
H240 X V162, QCIF Resolution H20 X V80. Please note the horizontal
resolution remains high but the vertical resolution decreases
by a factor of two (2). The D1 format is presently the best
you can achieve. HDTV technology will challenge this quality
in the near future.
The
total number of pixels drops dramatically and effects computer
power, memory and bandwidth to compress, store and transmit.
Be
careful not to assume the image will be two, three or four
times better or worse. The human eye will notice the difference
but technically it is not a cut and dry equation.
If
you compare the Digital Recorder specification and then compare
them to the CCD camera specification you will notice a 500-pixel
camera are specified at about 330 lines of horizontal resolution
and the 720 pixel-camera produces approximately 480 of horizontal
resolution. The vertical resolution on all cameras is the
same since they all have 484 active raster lines in NTSC format,
which yields approximately 320 lines vertically.
How does compression of images factor into the quality and
bandwidth of the digital images being transmitted and recorded?
The industry has two standards of compression. Lossless and
Lossy are the compression techniques. One used most is the
"Lossy" compression that offers a large compression ratio.
This compression technique is used in two main groups called
Intra-frame and Inter-frame.
Intra-frame
is used to form a single image such as a photograph and is
most popular in the various video formats. Examples of compression
ranges are as follows: JPEG 10-20, Wavelet 15-30 and JPEG
2000 20-60 which is an improvement of Wavelet.
Our Company has been receiving many brochures about training
opportunities. Why is training and certification so important
in today security world?
The security industry is gaining many offerings for training
in our industry. This is good thing for our customers and
the profitability of your company. Training and certification
provides a way to distinguish between those system planners
and installers who have the knowledge, skills, and experience
required to perform the work properly, and those who do not.
Of course, more systems that are complex require more advance
skills than do simpler systems. For this reason you should
look for an organizations that has established multiple levels
of certification related to increasingly complex systems.
Video system buyers and contractors can specify a certification
level appropriate to the particular system.
View
The Grill The CCTV Expert Archives
John
W. Colley is president of Integrated Security Systems, Ltd.
and has been in the security industry for over 25 years, beginning
his experience in the CCTV segment of security and gaining
knowledge through field experience, manufacturer training
and designing systems to meet customer needs. Colley started
his security integration firm 18 years ago, providing design,
engineering, installation and service to commercial accounts
using integrated systems. Send your CCTV/Surveillance questions
to jwc@securityiss.com.
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