Dispelling the Top 10 Myths of IP Surveillance: Myth #4

Myth #4: Transferring video over my network will overload it


[Editor's Note: The following is the fourth in a series of articles looking at the "myths" that surround the world of IP surveillance. Fredrik Nilsson, the general manager at IP surveillance manufacturer Axis Communications, has authored 10 articles dispelling these myths. In 2005, look for them monthly in SecurityInfoWatch.com and in the Security Frontline newsletter, and in the months of March, June and September in Security Technology & Design magazine.]

IP-based surveillance is rapidly replacing and upgrading traditional analog systems. Industry analyst, J.P. Freeman and Co., estimates that network camera sales will exceed those of analog cameras by 2007 and that network camera sales will more than double those of analog camera sales in the network video market by 2008.

When evaluating network video technology, one of the most common arguments against it is that transferring video over a network will overload the network, causing problems with other mission critical applications on the network. There is, in fact, some truth behind this myth. Video can consume large amounts of bandwidth, affecting the overall performance of network. However, with any size network video installation, users can take a few simple steps when designing their systems to ensure that their IP-based surveillance systems will not overload their networks.

For instance, how much bandwidth a network camera will use depends on several factors, including image size, compression, frame rate (images per second) and resolution. Network video products will utilize bandwidth based on how they are configured. Looking at resolution, a high-resolution picture (4CIF) contains four times as much data as a normal picture (CIF). A reduction of the frame rate to half (for example, 30 frames per second down to 15) will reduce the amount of data by half as well. Additionally, because of built-in intelligence, many network cameras will only send video over the network if the video is worth recording, which might only be 10 percent of the time. Ninety percent of the time nothing is being transferred over the network.

Small Wonders

Most small-scale installations - with only a few network cameras or video servers - can operate over an existing network. Because video runs on the same network as all other data transmissions, users should configure their cameras so that high-resolution images are not running at 30 frames a second over the network at all times. This would unnecessarily use up bandwidth and slow down other applications.

A professional network camera can send up to eight Mbps (megabits per second) of data over the network, depending on compression, size and frame rate. In order to reduce this, users can utilize the built-in intelligence in the network camera to reduce the size and speed of images transmitted over the network. A network camera can be configured to make "decisions" about video resolution and frame rate, depending on factors such as motion detection and time of day. For example, motion detected at 1 a.m. on Saturday morning - when no one should be in the office - can trigger the camera to transmit the highest resolution video at the highest frame rate. On the other hand, motion detected at 1 p.m. on Tuesday afternoon, would be considered "normal" and would not trigger an increase in resolution or frame rate.

Enterprise Deployments

Today, there are many examples of successful network video installations with hundreds, or even thousands, of cameras. For example, departments of transportation in Minnesota and New York use video servers to digitize the feeds from hundreds of analog cameras, enabling authorities to monitor roadways and commuters to view traffic conditions. School districts are also known for large-scale network video deployments. Districts often have several campuses that are spread out over large areas, which makes network video an ideal security and surveillance solution. Often times, schools piggyback network video onto underutilized data networks or even voice over IP (VoIP) systems.

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