Although expensive at their inception, technological advances made in the video surveillance arena in the last five to 10 years are now priced competitively, often costing the same or only slightly more than the protocols they were designed to replace. In fact, devices associated with the observation, recording, playback, and storage of events that were once considered “high end” are being used almost routinely in commercial building projects (Fig. 1). With closed-circuit television (CCTV) applications occurring more frequently, it's important for designers, specifiers, and installers to keep pace with the rapidly changing technologies involved with these systems.
In living color
In one such innovation, some manufacturers offer camera “packages” designed for use in specific applications — both indoors and out. These packaged camera systems include not only a camera and its appropriate lens, but also the housing, mounting device, and all applicable hardware. Shipped in a single box with the camera and lens already mounted in the enclosure, these “plug-and-play” packages simplify installation as well as the ordering process. Overall cost is usually the same as — and sometimes lower than — purchasing individual components separately. An added value is derived, as the variety of application-specific units simplifies the process of choosing the right camera and correct lens for use in a particular situation.
The development of color camera technology and the reduction in price of these units has resulted in their greater usage as the main component in a video surveillance system. Color offers improved resolution, sharper images, and a more true-to-life video presentation than that of a black and white camera. Their only drawback is that they require a higher level of illumination to create a visual image than does a black and white camera. This reality has led to the development of “day/night” or color/monochrome cameras.
Developed initially for outdoor use, these high-resolution cameras, which are priced only slightly higher than traditional color models, are also finding applications indoors. The units incorporate an infrared filter that automatically switches from color mode to black and white in response to decreasing ambient lighting levels, in order to maintain high-quality images regardless of light condition.
Another significant improvement in camera technology is the introduction of variable-speed camera positioning devices that provide both video signal transmission and remote control camera movement (pan-tilt) using a single coaxial cable, simplifying installation and reducing cost. Previously, a coaxial cable transmitted the video signal, and a separate set of conductors provided remote control of the camera's horizontal (pan) and vertical (tilt) movement.
Advancements in camera technology have also prompted the development of higher quality monitors both for live viewing and playback of recorded images. The 9-inch black and white model associated with earlier closed-circuit surveillance systems has been replaced with robust, super-high resolution color models, featuring larger flat panel LCD screens (up to 50 inches). Many incorporate Texas Instruments trademarked Digital Light Processing (DLP) technology, which features a single, all-digital display chip that makes use of an optical semiconductor to produce images of exceptionally high quality and fidelity. Other models use the same thin film transfer (TFT) LCD screens commonly found in laptop computers. These screens are comprised of a single sheet of glass that uses primary colors to produce an extremely sharp display without the appearance of faint duplicate or secondary images (ghosts) associated with previous generation LCD screens.
In addition to advancements in camera technology, the video surveillance industry has also made great strides on the recording front.
Demand for DVR on the rise
The introduction of the digital video recorder (DVR) has provided specifiers and designers with an important enhancement to the process of recording, storing, and reviewing of video images. A large percentage of the cameras sold today are equipped with a digital imager as a standard feature, making them compatible with a DVR even though the cameras themselves remain analog.
DVRs fall into one of two categories: those that are PC-based and those with an embedded operating system. The embedded operating system commonly uses either Windows or Linux, with recorder functions being accessed either from the controls on the face of the DVR itself, or through use of a handheld remote-control device. PC-based units rely on an associated mouse and keyboard to access control functions.
Although priced higher than its VCR counterpart, the PC-based DVR offers features and functions that easily offset any cost considerations (Fig. 2). Replacement of the VCR as a key component in a video surveillance system not only eliminates the purchase, changing, cataloging, and storage problems associated with VHS tapes, but also provides a major upgrade in the overall quality of video recording.
A DVR is essentially a dedicated computer that digitally records and stores the visual images transmitted from the video surveillance cameras linked to it. The DVR shares the same data compression technology as a computer, enhancing the amount of information it can save for future use. The amount of actual storage space depends on the size of the unit's disk drive, which may range from 80 GB (1 gigabyte is equal to 1024 megabytes) to 1 TB (1 terabyte is equal to 1024 gigabytes), depending upon the manufacturer and model chosen. Some manufacturers offer “unlimited” storage through the use of a redundant arrays of independent disks (RAID) server. With this option, recorded images can be partitioned over several different disk storage drives. Upon the loss or failure of a single drive, the data can be automatically reconstructed using information stored on the unaffected drives. Similar technology also allows several DVRs to be linked, through use of a computer network, to support and record an unlimited number of cameras.
The advantages of using a DVR instead of the traditional VCR are numerous. Unlike VHS tapes, which lose picture quality when reused and recorded over on several occasions, digital images recorded by the DVR never degrade. Instead, they maintain a crisp, sharp presentation, regardless of the number of times they're played or reviewed. Additionally, problems associated with videotape stretching, tearing, or breaking due to repeated use are avoided.
Digital images recorded by a DVR are stored by both date and time and can be easily recalled for playback, while the search for a specific recorded event associated with a VCR is very time consuming. Both the PC-based and embedded operating system styles of digital video recorders provide functions usually related to computer networks, including remote recording, viewing, and playback without compromising image quality during the transfer and receipt of video images.
Another feature associated with DVRs is their ability to record at higher frame rates than those associated with a VCR, providing enhanced visual quality and image definition. At 30 frames per second, the DVR captures events in the same manner as the human eye sees and processes information, which led to the term “real-time” video.
With DVRs constantly being improved, many models now include functions previously associated with separate system components, such as a matrix switcher or a multiplexer. These features include: the ability to display multiple cameras on a single monitor (usually ranging from four to 32 cameras) while recording each camera individually; duplex operation, which allows playback and review of an individual camera or groups of cameras while continuing to record each individual camera; and use of multiple monitors. This feature uses one monitor for live viewing of a multiple camera display, with a second monitor for full screen viewing of any one camera, and a third monitor for playback of previously recorded images.
Based on the popularity of DVRs, it's no surprise consumers have come to expect a “digital” experience. However, what most end-users don't know is that there's more to digital than meets the eye.
Defining digital
While digital recorders, cameras, and monitors are available, their use as components in a video surveillance system doesn't automatically make that system digital. There is a common misconception in the industry that using these devices constitutes a “digital” system, and one could argue that this is indeed correct. However, many define a digital system solely by the method of video transmission between the camera and the “head-end” components used for viewing and recording its images.
By this definition, any system using a hard-wired connection, such as coaxial cable, unshielded twisted pair copper conductor, or fiber-optic cabling to connect cameras to head-end equipment, is an analog system. Therefore, because the majority of video surveillance systems currently in use rely on a hard-wired connection for the transmission of video signals, they are still considered analog, regardless of individual components that use some form of digital technology.
A truly digital system uses network-based Internet Protocol (IP) components for the transmission of all-digital, 8-bit (or higher) video signals at a wavelength of 1,310 nanometers from digital IP cameras with built-in Ethernet interface to a network video recorder (NVR). This leading-edge technology, in its early stages of development, is expensive and often requires a separate, dedicated network to function properly. However, it's often proving to be the best choice for large video surveillance systems or those requiring transmission of video images over extended distances.
True digital video surveillance systems using IP technology will be refined and developed further in the near future. Today, they are what color cameras were to their black and white counterparts, or DVRs were to VCRs, just a few short years ago. It may be several years before these systems capture a large market share, but their use continues to grow. In anticipation of their increasing role, some manufacturers are now offering hybrid DVRs that will accept both analog (hard-wired) camera inputs and digital (IP) camera inputs.
The emergence of video surveillance systems as an integral part of overall commercial building design, as well as the rapidly changing technology associated with those systems, will continue to challenge specifiers, designers, and installers to keep abreast of their growing usage and development. Keeping a watchful eye on the latest improvements in video surveillance technology will be vital in choosing appropriate products and applications for future projects.
Shaver holds a NICET Level IV certification in Fire Protection Engineering Technology — Fire Alarm Systems and serves as an engineering associate, CET IV for Stanley Consultants in Muscatine, Iowa.
