Cutting the cost of IP video

What is the cost of IP video?
IP based CCTV / surveillance systems are capable of producing very large amounts of data all of which must be reliably stored to a Hard Disc Drive (HDD). Servers with multiple HDDs dedicated to storing such data are often referred to as Network Video Recorders or NVRs.

In an IP video surveillance system, a typical MPEG4 video stream from an IP camera / video server can provide D1 (720 x 576) resolution video at 25 frames per second. To maintain picture quality a bit-rate of at least 1.5Mbps can be required for each camera. If an IP surveillance system has 16 cameras that record constantly for 31 days the data very quickly exceeds the storage capability of any single commercially available HDD as detailed below:

Camera bit-rate = 1.5Mbps
Number of seconds in 31 days = 2678400
Total number of bits of data from 1 camera = 4 x 1012 bits
Total number of Bytes of data from 1 camera = 500 x 109 Bytes
Bytes of data from 16 cameras in 1 month= 16 x 500 x 109 = 8TB
The table below provides indicative calculations for a single MPEG4 video server / IP camera.

calculations for a single MPEG4 video server / IP camera

disk arrays

Individual HDDs are commercially available up to 1TB with the best quality and most cost-effective RAID edition drives still currently at a capacity of 500GB. To produce multi-Terabyte servers, several HDDs need to be logically joined together to provide a drive of much greater capacity. The general term for describing multiple disks joined together is RAID or Redundant Array of Inexpensive Disks. RAID provides a storage solution that can increase data throughput and provide redundancy allowing you to recover video footage even in the event of a disk failure.

There are many levels of RAID that have been developed over time with only a few that make commercial sense for IP video applications.

RAID 0 - Striping. The data is "striped" across all HDDs providing improved performance. A basic solution for joining many drives together.
RAID 1 - Mirroring. All drives have a partner drive to which a duplicate copy of the data is written. High redundancy and very high cost.
RAID 5 - Striping with a rotating parity disk - high reliability & high throughput, the preferred choice for professional installations.
RAID 6 - Striping with 2 x rotating parity disks - as per RAID 5 but can offer redundancy even in the event of 2 disk failures in 1 array

If you would like more information on RAID levels, see the following online tutorial.

Amplicon's servers are capable of re-building a RAID 5 array automatically by using a "hot spare" (A HDD installed that is not part of the original array). The system can recognise if a drive has failed, disable the drive, re-build the array using the hot spare and then send you an email to tell you it has recovered from the failure. This system has the potential to save the cost of a site visit or can be used to economically schedule site visits as the server can advise of the relative health of HDDs in each array in the server.

Some IP video software packages support the concept of an extended disk array with RAID redundancy whilst others are dependent on a 'single disk' or JBOD (Just a Bunch of Disks) configuration. Whatever the requirement, Amplicon's servers have the flexibility to meet the needs of the application.

How to cut costs in IP video

A brief survey of the storage market indicates a (configured) cost of between 20p and 60p per GB of data. If we can limit the GigaBytes of data actually required in each application we can substantially reduce the cost of a digital solution and still reap the benefits of IP technology.

Reduce frame rate
It is often possible to justify a lower "frames per second" setting than originally planned. When the cost differential is made apparent, many end users may suddenly take a new approach to what they "really" need.

Reduce resolution
The IP CCTV system industry has worked un-questioningly with a 4CIF or D1 screen resolution as standard for many years. Could your application settle on CIF or 2CIF? Would this reduction seriously affect the end user experience? If not, thousands of pounds in storage costs can be saved in IP systems.

Reduce quality
It is possible to compromise the quality of an MPEG4 stream by lowering the overall bit-rate from the encoding device. If your system only needs to recognise the presence of an object but not any detail associated with it, then storage space hence money can again be saved.

Reduce RAID level
If cost is the most important feature of a storage system then it is possible to drop from RAID6 to RAID5 or perhaps even RAID 5 to RAID 0. This reduction in reliability will save at least the cost of one high capacity HDD - usually several hundred pounds..

Use MPEG4 not MJPEG
MPEG4 offers a more efficient trade-off between picture quality and required bandwidth / storage. For many security systems, MPEG4 can directly replace MJPEG with as much as 50% reduction in storage overhead.

Event-driven recording
Do you need to capture video all the time? In a stock-room you may only want to record when a door opens or a light turns on. People walking the wrong way along a platform or running could be another trigger for video recording. Modern video analytics systems are becoming increasingly intelligent. The additional cost of intelligent systems can be offset by the greatly reduced storage requirements.

Amplicon can advise on all aspects of security automation solutions. If you would like more information about out IP CCTV or IP video surveillance system, please call sales on 01273 570 220 or email security@amplicon.co.uk.