DVR systems are more reliable since there are no tapes to jam. They offer better video quality as they do not have tape wear problems. They have a low risk of degaussing or signal loss. They can store significantly more images — from weeks to years worth of data. They also eliminated the need for multiplexers as they provided that capability built into the DVR itself. The most important enhancement is that they are effectively automated so that you do not need a human resource to rotate tapes or remember to push the recording button.
The primary reasons for DVR implementations were to address the above issues; however they still have limitations. They still were primarily connected to analog cameras and were therefore still implemented local to the cameras themselves, making remote viewing problematic. They still were limited in the number of camera ports available, as most of them allowed up to 16 channels or video ports. They also tended to be based on a proprietary analog-to-digital conversion capture cards which were not interchangeable with another manufacturer's DVR. Components and accessories were also proprietary. This also meant that the DVR manufacturer was your only real option for service and replacement — limiting the security director's options for consolidating service contracts. Backup and recovery of recorded images is typically not available — if you lose the device, you usually lose the images recorded on the disk.
The advent of the DVR provided advantages over tape-based systems, but more was needed to respond to security industry requirements.
The Impact of IP Based Systems: the NVR
The convergence of IT systems with physical security applications has been widely described. Suffice to say that the incredible growth of IP-based solutions is in parallel with the explosive growth of the Internet and browser technologies. Companies started to see the opportunities presented by using IT networks for more than business applications. Building management systems, fire control systems, HVAC, alarm and access controls, elevator controls, lighting controls, telecommunications, PA Systems, e-commerce applications, and many other previously siloed systems have joined this technological revolution. Physical security is no exception. The move to IP-based solutions on open architectures is under way. IP solutions open a wide variety of options and advantages to the security industry.
The advantages of using IP-based technology are a significant leap forward over previous systems. First and foremost is the simple ability to connect the IP-enabled camera systems to your IT network, eliminating the coax cables. It also means that the ability to transmit those images across geographic areas is now only limited by your network's limitations. Local storage is no longer required. Getting power to an analog camera has always been a major obstacle and cost. The IEEE 802.3af standard for Power over Ethernet (PoE) was designed to address this problem, leading to significant cost savings in deployment of IP cameras. PoE means that networking devices get power from a PoE-enabled switch over the same kind of Category 5 cable that transmits data and video. It also means that cameras can get centralized backup power from the computer room backup power systems, so in the event of a power failure, they will continue to operate. Legacy analog cameras can be connected via a video server (which converts the analog to digital format) to the IP network to allow for migration plans and capital expenditures to be planned within budgets. IP digital cameras do not need to be converted.
One of the drivers in this industry is the sheer volume of video that is being captured. Security directors need to be sure that they record the information that is critical, and not capture information that is of little value. A camera watching an empty hallway is only valued when activity is presented. Intelligent video is one of the next big trends. Network cameras can have built-in motion detection and alarm management at the camera itself. The camera decides when to send video, at what frame rate and resolution, and when to alert a specific operator for monitoring or response. Intelligent algorithms for license plate recognition, people counting, facial recognition, etc., are being integrated into network cameras.