Axis Network video - Calculating Storage Needs

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When implementing 10 or more cameras, the network load can be estimated using a few rules
of thumb:
> A camera that is congured to deliver high-quality images at high frame rates will use
approx. 2 to 3 Mbit/s of the available network bandwidth.
> With more than 12 to 15 cameras, consider using a switch with a gigabit backbone. If a
gigabit-supporting switch is used, the server that runs the video management software
should have a gigabit network adapter installed.
Technologies that enable the management of bandwidth consumption include the use of VLANs
on a switched network, Quality of Service and event-based recordings. For more on these topics,
see chapters 9 and 11.
12.1.2 Calculating storage needs
As mentioned earlier, the type of video compression used is one of the factors aecting storage
requirements. The H.264 compression format is by far the most ecient video compression
technique available today. Without compromising image quality, an H.264 encoder can reduce
the size of a digital video le by more than 80% compared with the Motion JPEG format and as
much as 50% more than with the MPEG-4 (Part 2) standard. This means much less network
bandwidth and storage space are required for an H.264 video le.
Sample storage calculations for all three compression formats are provided in the tables below.
Because of a number of variables that aect average bit rate levels, calculations are not so clear-
cut for H.264 and MPEG-4. With Motion JPEG, there is a clear formula because Motion JPEG
consists of one individual le for each image. Storage requirements for Motion JPEG recordings
vary depending on the frame rate, resolution and level of compression.
H.264 calculation:
Approx. bit rate / 8(bits in a byte) x 3600s = KB per hour / 1000 = MB per hour
MB per hour x hours of operation per day / 1000 = GB per day
GB per day x requested period of storage = Storage need
Table 12.1a The gures above are based on lots of motion in a scene. With fewer changes in a scene, the gures can
be 20% lower. The amount of motion in a scene can have a big impact on the amount of storage required.
Camera Resolution
Approx. bit rate
(Kbit/s)
Frames per
second
MB/
hour
Hours of
operation GB/day
No. 1 CIF 110 5 49.5 8 0.4
No. 2 CIF 250 15 112.5 8 0.9
No. 3 4CIF 600 15 270 12 3.2
Total for the 3 cameras and 30 days of storage = 135 GB
CHAPTER 12 - BANDWIDTH AND STORAGE CONSIDERATIONS