Ten Steps to a Successful IP Surveillance Installation: Step 4

Understanding IP-based video storage and server systems, plus how to calculate storage needs


Recording and saving video in an IP surveillance environment requires the ability to store large amounts of data for sometimes unspecified lengths of time. There are a number of different factors to consider when selecting the appropriate storage system for an installation including scalability, redundancy and performance.

Similar to the way a PC can "save" documents and other files, video can be stored on a server or PC hard disk. Specialized equipment is not needed because a storage solution does not differentiate video data - it is viewed as any other large group of files that is stored, accessed and eventually deleted. However, video storage puts new strains on storage hardware because it may be required to operate on a continual basis, as opposed to during normal business hours with other types of files. In addition, video by nature generates very large amount of data creating high demand on the storage solution.

Calculating the storage needs

In order to appropriately calculate the storage requirements of a network surveillance system, there are a number of elements to factor in, such as the number of cameras required in your installation, the number of hours a day each camera will be recording, how long the data will be stored, and whether the system uses motion detection or continuous recording. Additional parameters like frame rate, compression, image quality and complexity should also be considered.

The type of video compression employed also effects storage calculations. Systems employing JPEG or Motion-JPEG compression vary storage requirements by changing the frame rate, resolution and compression. If MPEG compression is used, then bit rate is the key factor determining the corresponding storage requirements.

Storage is usually measured in Megabytes (MB) per hour or in Gigabytes (GB) per day. One MB equals one million bytes, and one GB is one billion bytes. There are eight bits per byte, and these bits are essentially small "pulses" of information.

Fortunately, there are very specific formulas available for calculating the proper amount of storage to buy. These formulas are different for Motion-JPEG and MPEG compression because Motion-JPEG consists of one individual file for each image, while MPEG is a stream of data, measured in bits per second. The formulas are as follows:

Motion JPEG

1. Image size x frames per second x 3600s = KB per hour / 1000 = MB per hour
2. MB per hour x hours of operation per day / 1000 = GB per day
3. GB per day x requested period of storage = Storage need

Camera Resolution Image size (KB) Frames per second MB/hour Hours of operation GB/day
No.1 CIF 13 5 234 8 1,9
No.2 CIF 13 15 702 8 5,6
No.3 4CIF 40 15 2160 12 26

Total for the 3 cameras and 30 days of storage=1002 GB

MPEG

1. Bit rate / 8(bits in a byte) x 3600s = KB per hour / 1000 = MB per hour
2. MB per hour x hours of operation per day / 1000 = GB per day
3. GB per day x requested period of storage = Storage need

Camera Resolution Bit Rate (kBit/s) Frames per second MB/hour Hours of operation GB/day
No.1 CIF 170 5 76,5 8 0,6
No.2 CIF 400 15 180 8 1,4
No.3 4CIF 880 15 396 12 5

Total for the 3 cameras and 30 days of storage= 204 GB

Storage Options

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