Video's supporting cast also important

Cameras are just one part of the digital video picture. Other important components can include software for managing images, customizable interfaces for using video with other devices and types of data, and specialized storage management systems.

For example, Detroit's Metropolitan Airport uses analytic software from Verint Systems Inc. to mine video surveillance data, said Allison Gapter, Verint's senior marketing manager.

Users can write reports on specific security incidents and attach them to video clips or analyze peaks of activity. While analyzing activity, users can run live video while simultaneously showing video of events that happened five minutes before. The software can simultaneously display 16 video windows.

In addition, Verint's software enables agencies to use video in tandem with other data types. For example, at the U.S. Capitol, video is linked to employee badge readers and X-ray bag-screening machines.

"You can key in an employee's badge number to see [the video of] their bags going through X-ray," Gapter said. "You can marry video data to really anything, and then you can query on that other data resource and see the married video clip."

One practical challenge of video technology is the huge amount of data it creates, which often must be stored a long time. Storage management software, such as Storage Technology Corp.'s (StorageTek) Application Storage Manager, can automatically transfer large video files from expensive online disks to lower-cost tape, yet still keep it accessible to users for when they need it.

"We allow [managers] to set up their own business policy for how long they keep it on a spinning disk before archiving to a separate medium, like tape," said Steve Rice, StorageTek's practice manager for security surveillance. "You're archiving the video, and you don't know when you will need a piece of video — but when you need it, you need it now. Why store all the video on high-cost disk just for the rare occurrence of the segment of video you need to retrieve?"

In addition, the StorageTek software uses digital signatures when storing files to safeguard against someone tampering with a video image, for example, by using an image manipulation tool like Adobe Systems Inc.'s Photoshop.

"We provide the ability to make sure that anyone who tried to get into the system had the appropriate access level to do that," Rice said. "Digital signatures prove that the video is not altered. Once you write it to one of our tape libraries, you can't change it."

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Analog vs. digital video

n Analog, or magnetic tape-based systems, require the monitoring location to be close to the cameras. Digital systems, which can use standard IP networks, have no distance constraints.

n Analog offers little if any integration with other security mechanisms such as badge readers or intrusion-detection systems. Digital systems are designed to integrate seamlessly with many other security systems.

n Analog systems can transmit only one video signal at a time, so one cable is needed per camera. That can boost costs because of the need for additional lines, video recorders and muliplexers. Digital video from multiple sources can be carried over a single cable.