Video Surveillance Bandwidth And Storage Considerations

Network bandwidth and storage requirements are important considerations when designing a video surveillance system. The factors include the number of cameras, the image resolution used, the compression type and ratio, frame rates and scene complexity.

MPEG-4 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
Note: The formula does not take into account the amount of motion, which is an important factor that can influence the size of storage required.

Motion JPEG calculation

Image size x frames per second x 3600s = Kilobyte (KB) per hour/1000 = Megabyte (MB) per hour
MB per hour x hours of operation per day / 1000 = Gigabyte (GB) per day
GB per day x requested period of storage = Storage need

Bandwidth and storage calculations

Network video products utilize network bandwidth and storage space based on their configuration. As mentioned earlier, this depends on the following:

Number of cameras
Whether recording will be continuous or event-based
Number of hours per day the camera will be recording
Frames per second
Image resolution
Video compression type: Motion JPEG, MPEG-4, H.264
Scenery: Image complexity (e.g. gray wall or a forest), lighting conditions and amount of motion (office environment or crowded train stations)
How long data must be stored

Bandwidth needs

In a small surveillance system involving 8 to 10 cameras, a basic 100-megabit (Mbit) network switch can be used without having to consider bandwidth limitations. Most companies can implement a surveillance system of this size using their existing network.

When implementing 10 or more cameras, the network load can be estimated using a few rules of thumb:

A camera that is configured 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.