IP Digital Video Systems (DVS), also known as IP CCTV is the logical extension of the continuing development of analogue (and later digital) CCTV.
In a Digital Video Recorder or Digital Video Server, we see that an analogue picture is compressed and encoded into a digital format at the recorder or encoder for storage onto hard drives. Using remote client applications or software, these digitised pictures are transmitted to remote monitors where cameras and recordings can be viewed and controlled.
With IP DVS, the picture is compressed and encoded into IP (internet protocol) data packets at the camera instead of producing an analogue or digital signal. These data packets are transmitted over an IP network and received by an Network Video Recorder (NVR) or Network Video Sever (NVS), then encoded into a digital format for storage onto hard drives.
IP camera systems use standard IP network cabling to transmit the IP data packets between the camera and Network Video Recorder (NVR). These data packets are packaged at set pre-programmed sizes by the camera with a view to balancing maximum picture quality with the available space (bandwidth) on the network and drive storage capacity. Once the data reaches the NVR, the NVR must unpack the data packets and present them as a picture on the monitor, which is very processor intensive. For this reason there can sometimes be a time lag between the picture being captured by the camera and it’s display on the monitor.
This can become much more pronounced on busy networks, or systems with poor quality equipment or with a flawed configuration. Even so, over the last 15 years, IP digital video systems have evolved and improved along with advances in digital storage to form a viable alternative to traditional analogue or digital CCTV systems. With the advent of plug and play NVRs and cloud computing, these systems have even entered the domestic DIY market.
Initially, there were large negative cost implications in opting for IP Digital Video. However over time, and with the continued development of Power over Ethernet (PoE, PoE+, PoE++), these cost differences have been eroded to such a degree that IP systems are now at least on an equal footing with traditional CCTV systems.
Digital Video
Over the last 20 years, from the introduction of the first Digital Video Recorders, there has been a gradual trend away from purely traditional, analogue CCTV systems and towards a fully integrated, networked digital infrastructure where not only CCTV but, for example, Access Control and Building Management Systems can run on the same IP network. This has been fuelled by the falling costs of IP equipment coupled with the increasing capability of these systems.
The benefits of Digital Systems
A fully integrated digital network has some inherent advantages:
Provided that there is a good quality pre-installed IT infrastructure, it may be possible to add IP digital video to it without overloading the bandwidth. Digital networks are usually easier to expand, by virtue of the fact that often new commercial buildings are pre-wired with the appropriate cable, in readiness for future growth. This means that new devices could be added with the minimum of disruption.
Sometimes buildings are fitted at the outset with provision for separate network cabling for ‘non-IT’ networked systems. In this instance the cabling may be led to separate termination cabinets and/or network switches. However it has become increasingly common for security companies to install their own network cabling and equipment at the build stage.
With the ability to join small networks together to form larger ones, using various techniques including routers or VLANs, distributed networks can easily be configured, enabling access from anywhere to anywhere. High Definition (HD) and Ultra HD (UHD) image recording is now also available using digital systems, with the consequent improvement in image quality and the ability to search and retrieve images from anywhere on the network.
Lastly, with a single infrastructure, adding other systems is simpler, with the whole being managed by a single team: the inclusion of access control, intruder alarms, public address, Voice over IP, radio broadcast and so on becomes easier.
What are the Pros and Cons?
The building-in of system resilience is unusual in a network designed solely to carry corporate data - LANs are not normally resilient systems, so extra measures are needed to provide that resilience for a mission-critical network. This can however have an effect on infrastructure cost.
The issue of bandwidth is important. A LAN designed merely to carry corporate data may have insufficient capacity to carry bandwidth-hungry CCTV without additional spending on the appropriate technology to support the higher demands. It is also a requirement to attempt to predict and allow for a foreseeable amount of expanded demand to ‘future proof’ the system. For instance, a client has IP CCTV and Access Control, running to a single viewing PC. Over time, the system has expanded to include many more access doors, and they have added a further three Viewing PCs – this possibility was not taken into account in the original design, which would cause system performance to suffer in consequence.
Delay. It is a fact that a digital camera using any version of compression will demonstrate delay in the production of video images. This is initially caused by the processes within the camera itself, which will be dealt with in more detail later. In addition, the connection of cameras to a LAN will in itself create further delay.
Much of your work in commissioning a Digital Video System or integrated IP system will be to configure all of the system devices optimally to reduce delays (known as latency), whilst ensuring system operation and image quality remains acceptable.