What is DVR?
|Previous method for
recording CC-TV on tape with tape-recording
equipment is an analog type. Therefore, it is very
inconvenient to change the tapes frequently and it
lowers the quality of image. However, a Digital
Video Recorder or DVR, digitally records the video
image so it provides clear image like a picture. It
also has a function to record continuously so you
don't have to worry about the frequent change of
tapes. DVR, therefore, is a video recording
surveillance system for the next generation and it
is growing very rapidly. In addition to that, it has
communication function which enables you to detect
remoteness screen even from household and it
contains a multi branch of up-to-date function.
Do I still need a VCR if
I purchase a DVR?
||There is no need for
the video cassette recorder unless you wish to store
video on cassette for your own reasons. You can
record on the VCR as well the DVR at the same time.
Does learning how to
operate a DVR require knowledge of PC's?
||While knowledge of
using a mouse and keyboard is helpful it is not
required. Anyone can learn to operate and program
any of the DVRs functions, as the systems were
designed with the non-PC friendly person in mind.
How many days of
recording can I expect the DVR to store?
||This is probably the
single most difficult question with the most
confusing of answers and where one needs to be very
analytical and read the fine print. The answer is,
there is no individual answer. So we need to break
down the answer into components.
. Hard drive space
. Video compression method (MPEG, MJPEG, wavelet,
. Video compression rate
. Number of frames per second being recorded on each
. Resolution of frames being recorded (320 x 240,
640 x 480, etc.)
. Is video being recorded full time or only on
. How many cameras are being recorded
A DVR stores the video images on hard drives.
Storage capacity is dependent upon the amount of
hard drive space. Hard drives come in a variety of
sizes. A DVR may have from a single to multiple hard
drives built-in. The DVR can be attached to external
PC-like devices called RAID (Redundant Array
Inexpensive Disks), which can virtually supply an
unlimited number of hard drives.
The file size of the video images, vary radically
from one video compression method to another. To
further confuse the issue there are different
flavors of the same video compression methods, and
as such the different flavors produce different file
Video compression rates can be adjusted within most
DVR programs. The more you compress the video the
poorer the quality of the video, but the faster the
transmission speed since the packet is smaller.
Video can be compressed as many as 300 times.
If you require real motion video on a camera you are
recording 30 images per second. If you do not need
to record in real motion you obviously can save hard
drive space proportionately by reducing the number
of images per second being recorded.
Images are made up of little dots (pixels). The
pixels in an image make up what is known as the
resolution. The more pixels in an image (the higher
the resolution); the higher the quality of the image
and the larger the size of the file to be stored.
If video is being recorded only when motion is
detected (if that feature is available on a DVR)
then you reduce the amount of storage requirements.
If you are recording on multiple cameras then you
increase proportionately the amount of data being
stored up to the maximum capacity of the video
capture board. If the video board capacity is 120
frames per second then it can never exceed that
In a corporate or retail environment that is not
high security and does not require the highest of
video image quality and utilizes motion detection,
using a 60 image per second video capture board,
where they operate 8 - 12 hours a day, a 40GB hard
drive should provide 3 - 4 weeks of storage.
Remember, certain things can skew these numbers
significantly, such as blinking lights or something
that causes the video to continually record that may
not be obvious to the eye.
The other extreme is recording using MJPEG, real
motion, high resolution recording, on a 240 frame
per second video capture board, which can chew up as
much as 30GB - 40GB per hour.
Most claims for video storage capacity are usually
accompanied by a statement in parentheses that
states "under normal conditions." Good luck defining
what are normal conditions!
What happens in the
event of a power outage?
||To protect the DVR
you want to use a power backup, which serves as a
surge protection device and a power source for a
limited period of time in the event of a power
failure. If the power failure continues for an
extended period of time, the DVR will intelligently
shut itself down. When the power returns it will
return to its mode immediately prior to the
interruption of power.
Can I view the DVR from somewhere other than the
physical DVR location?
With the majority of DVR’s you can connect via a
Internet connection, Local or Wide-Area-Network.
How do I view
the camera images from my PC, laptop or PDA?
come with remote client software that has to be
installed on your computer. The remote software
allows you to view the cameras once you are
connected to the DVR via a phone line modem,
Internet connection, or Local or Wide-Area-Network
access DVR through web browser as well if you have
Can I use my existing cameras?
||Yes. Your existing cameras will work and simply plug into the back of the
DVR which replaces the VCR. If your cameras are not so current you may want to investigate some of the newer
cameras which are higher in resolution and may have more features. Typically, higher resolution cameras mean
higher quality images.
How do I control a camera with Pan/Tilt and Zoom functions?
||TOPS DVRs have some sort of control on the monitor that operates
like a joystick and by clicking the mouse over the appropriate function the camera responds.
You can fully control DVRs if you use a TOPS joystick or TOPS certified joystick.