UFC 4-021-02NF
27 September 2006
change 1, 23 October 2006
4-8
RECORDING
4-8.1
Recording of CCTV images is almost always done for retrieval of surveillance
information. Consideration must be given to the location and capacity of the recorders.
The bandwidth requirements for streaming video can be high (i.e. 3.07 Mbps for one
camera in alarm.) To reduce recurring cost of transmitting high bandwidth demands, it is
a good design practice to install recording equipment locally and transmit lower quality
images back to the Dispatch Center. For example, it is less costly to download camera
images at 15 frames per second (fps) at the local site and transmit a 2 fps image back
to the Dispatch Center. While the 2 fps image will be choppier, it can give sufficient
information to view what is going on at a remote site (i.e. there is an intruder). If
evidentiary information (i.e. identity of the intruder) is required that information can be
retrieved from the local site. Alternatively, more time can be used to download a higher
quality image if so needed.
4-8.2
Storage Requirements. This example demonstrates how to calculate
storage requirements. Assuming a typical camera image of 25 kbytes, the required
memory storage capability for 30 days of images at 6 frames per second is 389 Gb.
That storage requirement is calculated in Figure 4-9.
Figure 4-9. Calculation for Storage of Frame Size of 25 kbytes
Capacity = (Frame file size in bytes) x (frames per second) x (duration in
seconds)
Capacity = 25 kbytes x (6 frames per second) x (3600 sec/hr) = 540 Mb x (24
hr/day) x 30 days = 389 Gb
Thus, one camera transmitting camera images of 25 kbytes in size will require
389 Gb for 30 days of storage.
4-8.2.1 Quickly, it can be seen the memory requirements for a complex camera
system can be extensive. The ESS designer needs to specify sufficient recording
media/methods to archive the project's camera images using a methodology similar to
the one displayed in Figure 4-9.
4-8.3
Principle Technologies. There are four principal technologies for recording
CCTV video information: old-fashioned VHS, contemporary digital video recorders
(DVRs), network video storage, and data servers.
4-8.3.1 VHS Recording is an older technology. Banks of VHS recorders were
designed to download CCTV camera images. Tapes were frequently swapped out and
storage space had to be planned for record retention. Since VHS technology has been
made obsolete by current technology (i.e. DVRs), VHS units are not recommended for
new security projects.
4-8.3.2 Digital Video Recorders. Digital video recording provides a great
improvement in camera image storage. Benefits include eliminating consumable media
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