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ANALOG
or DIGITAL RECORDING?
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We offer both types
and we want you to clearly
understand the differences before you specify or buy a system.
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Lets be
realistic, most analog or
digital time lapse recorders, closed circuit cameras and accessories
were not
built for field, lab, educational, scientific, industrial or wildlife
applications. They
were built for the security
industry which has enormously different requirements
than most of
your applications.
Most
digital time lapse video security systems are intended for short bursts
of
important data (i.e. the five minutes while a bank is being robbed) or
for some
few hours (i.e. while the robber is casing the bank without his mask
on). The
video data being stored on the digital hard drives(DHD) is immediately
available
to the police or security for downloading to the internet, digital
storage
cards, DVD's, etc. When
the event is
over and the small amount of critical data is archived off of the DHD,
the DHD
is then placed back on line to record new video data.
At some point in the future, depending on DHD
capacity, it will
start to write over the data previously recorded but the small
amount of
security critical data has been saved.
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HOW
SMALL (OR LARGE) IS THE AMOUNT OF YOUR CRITICAL DATA???
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With digital,
even if you swap out
dockable DHD's, you must do immediate and constant post processing
within the
time limit capacity of the DHD's you are using. To not post process
would
require a large number of DHD's (at roughly $300.00 per 80 gig DHD with
cassette). Even if
transferred to large
DHD's, the cost can
approach $1000.00
per terabyte.
GET THE PICTURE,
WHAT ARE YOU GOING TO DO WITH TERABYTES OF DATA?
With
analog recording systems, you simply eject the $3.00 tape and replace
it with a
new $3.00 tape. Archiving
is done and
no data can be lost! Now
you can
immediately review the tape or forget about it for 6 months or longer
while you
continue your work.
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| ANALOG RECORDING ADVANTAGES |
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No post processing required in the field/lab
Data storage is cheap ($2 - $3 /tape)
Changeout time in field is a fraction of that
for a DHD
Easily display output on analog monitors
Most television repair stations can service the
recorders
Sampling techniques can easily be implemented
Known compatibility with Noldus Video observer
pro,
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| ANALOG RECORDING DISADVANTAGES |
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Tape storage is relatively bulky
T120 and T160 tapes are about all that are available
Variety of available recorders are decreasing
because security industry doesn't need them
Systems generally require more power than
digital systems
Resolution degrades when tapes are copied
Moisture condensation on recorder heads can be a
problem
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| DIGITAL RECORDING ADVANTAGES |
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Various resolution levels are available to much
higher levels than most analog systems
Various compression schemes are available MPEG 2
, MPEG 4, etc.
Tremendous range of storage capacities from 20
gig to many terabytes
Variety of DHD recorders are growing
explosively, most are not suitable for field/lab use.
Systems generally require less power than analog
systems
Moisture generally less of a problem because
DHD's are sealed.
Pre-alarm recording is possible if triggered
system is used (not recommended unless calibrated)
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| DIGITAL RECORDING DISADVANTAGES |
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Post processing is a virtually certain
requirement for most field applications.
DHD changeout in field usually requires power
down, changeout and reboot
DHD's are expensive and a poor choice for large
digital storage
Transferring DHD's to DVD's is slow, expensive
and painful (you have keep track of 20 -30 DVD's for each 80 gig DHD download
DHD's are relatively more fragile than tapes
Active window area alarm triggers on DHD systems
are designed for human sized subjects and stable image backgrounds (a bank lobby on a Sunday afternoon)
and not the field where leaves blow, trees shake,clouds pass etc. etc. etc
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Which
leads me to my final statement concerning all recording systems:
IF YOU LIKE TO COLLECT LOTS OF INVALID DATA, USE
A TRIGGERED SYSTEM THAT HAS NOT BEEN CALIBRATED
To calibrate you must use a
continuously recording video system with a valid temporal interval (time
between images) so absolutely no data has been lost during the
calibration period.
I
invite your comments and suggestions. |
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Richard Fuhrman
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WE HAVE BUILT OVER 650 FIELDCAM™ CUSTOM MONITORING
AND INTERACTIVE SYSTEMS SINCE 1987!
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FUHRMAN DIVERSIFIED,
INC., 2912 BAYPORT BLVD., SEABROOK, TX 77585,
PHONE: (281) 474-1388, FAX: (281) 474-1390, e-mail: fdi@flash.net,
TECHNOLOGY AND TOOLS
FOR THE 21ST CENTURY.COM™ |
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