Surveillance Systems

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Video surveillance systems started out as 100% analog systems and have gradually become digital, even though analog systems remain in use to some degree. Today’s fully digital systems, which are using network cameras and PC servers for video recording, have come a long way from the early analog tube cameras, which were connected to VCRs that required hand-operated tape switching. 

DVRs were eventually equipped with an Ethernet port for network connectivity. This introduced network DVRs to the market and enabled remote video of live or recorded video using PCs. 

Alternatives to the open platform, which is based on a PC with installed video management software, are different types of network video recorders (NVRs) and hybrid DVRs. An NVR or hybrid DVR is a proprietary hardware box with preinstalled video management software for managing video from video encoders or network cameras. The NVR handles only network video inputs, whereas the hybrid DVR can handle both network video and analog video inputs. Because recording and video management are available in a single unit, very much like the DVR, the benefit of using an NVR or hybrid DVR is the ease of installation. However, while they are often easy to install, NVRs and hybrid DVRs are often more difficult to maintain on a corporate IT network because they use proprietary platforms. 

As its name indicates, a network camera—commonly called an IP camera—is a camera with an IP network connection. In a network camera–based video system, video is transported over an IP network through network switches and is recorded to a PC server with video management software installed,this represents a fully digital network video system.

One of the greatest benefits of a network camera is that when images are captured, they are digitized only one time (inside the camera) and then remain digitized throughout the system. As a result, the image quality is consistently high. This is not the case with analog cameras. Though most analog cameras today are called digital, they have an analog output, which can lead to some confusion. Analog cameras do digitize captured images to provide image-enhancing functions. However, these images are then converted back to analog video. It is important to know that with every conversion from analog to digital, or from digital to analog, there is some loss of video quality. Analog signals also degrade when transported over long cables and over time if stored on tape. Ideally, therefore, video should be digitized once and remain digital throughout the system.

Another advantage of IP-based networks is that one can use the network for more than just transporting video. Besides allowing several network cameras to share the same physical cable, IP networks can carry

In addition, an IP network enables network cameras to be configured remotely and allows video and other data sent over the network to reach virtually any location without reductions in quality. To sum it up, IP networks provide an extremely flexible and cost-effective medium for all communications within a network video surveillance system. Network video is scalable; it offers opportunities to build any size of video surveillance system, from a single camera to thousands of cameras.

A network camera–based network video system offers many advantages:

• Access to high-resolution (HDTV and megapixel) cameras.

• Consistent image quality, regardless of distances in the network.

• The same cabling can be used for video, power, PTZ, audio, and digital input and output, and audio.

• Access to wireless functionality.

• Remote access to camera settings and focus adjustments over IP.

• Access to edge intelligence and edge storage (i.e., built into the camera).

• Full flexibility and scalability.

Though an analog camera connected to a video encoder can be compared to a network camera, a network camera can offer many more value-adding functionalities.

The network camera is a key driver in the network video revolution. Network cameras have more than caught up with analog camera technology. Not only do they greatly surpass analog video quality in many aspects, such as resolution and light sensitivity, but they also offer the advantages of built-in intelligence and storage.

To determine which types of network cameras are suitable and how many cameras are needed to cover an area, the scene, environment, and purpose must be determined first. Considerations include the following:

• Indoor or outdoor camera: If placing the camera outdoors, install it in an appropriate protective housing or use an outdoor-ready camera. Look for the IP rating (IP66 or better) or National Electrical Manufacturers Association (NEMA) rating (4X or better). The camera should also have auto-iris functionality.

• Pan, tilt, and zoom (PTZ) or fixed camera: PTZ cameras with a large optical zoom factor can give high-detail images and survey a big area. Keep in mind that to make full use of the capabilities of a PTZ camera, an operator needs to control the movements, or an automatic tour must be set up. For surveillance recordings without live monitoring, fixed network cameras are normally more cost effective.

• Light-sensitivity and lighting requirements: Consider adding external white lights or specialized lighting such as IR (infrared) lamps. Day-and-night functionality means you can get images in conditions that would otherwise be too dark. The light-sensitivity levels of a camera are important and should be evaluated. Do not go by the measurements on a datasheet as vendors measure in different ways. For more information on light-sensitivity measurements, 

• Complete darkness and perimeter protection: Thermal cameras can detect movement even in complete darkness and other difficult conditions. Generally, they can also detect movement at greater distances than conventional cameras.

• Tamper- or vandal-proof and other special housing requirements: Proper protection against water, dust, temperature, and vandalism is essential. 

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