Why is an IP Network better than a CCTV system?
The answer is: for the sheer unbeatable flexibility and convenience it offers.
All new and most modern buildings have ‘structured cabling’ using CAT5 multi-purpose twisted pair cables. These can carry an Ethernet network throughout the business – and the LAN (local area network) in one building is easily linked across a WAN (wide area network) between buildings, often over long distances. Many businesses already have WANs linking their many offices.
Conventional cameras, DVRs and viewing workstations can all be connected through a LAN, completely avoiding new cable pulling. Further-more, once video is on the LAN, it can be sent anywhere in the world across the LAN or WAN: between buildings, cities or even continents. Once on IP, the world is literally your oyster and, more importantly, your customer’s oyster.
For example, Sirrus’ Washington DC video system for traffic congestion called Traffic Watch, shows live pictures covering 3,500 miles of different road. But this entire system is managed remotely … from Surrey.
‘Pure’ network-based systems
Two distinct approaches to using IP networks in CCTV are worth looking at.. The first can be called ‘Pure’ network-based design.
In such a system – which might suit any large physical environment where either a major refurbishment or new system fit is planned – the whole CCTV system, its operation, picture management (switching, steering, video recording, forwarding and so on) and display facilities, can be planned around the local area network.
It has the following features:
Note that standard cameras can still be used – there is no need to move to IP cameras to make use of the network. PAL cameras are easily interfaced to a LAN.
Hybrid systems
Hybrid systems link an existing PAL CCTV system to a Local Area Network. This second approach to networking video is one to which too little atten-tion has been paid in the past. Hybrid working takes the best of both worlds, allowing existing systems to take advantage of the new methods.
Many existing CCTV systems do their job admirably and need not be dismantled just to exploit the power of networks. Products such as Sirrus’ IPTX family are designed to make it easy for an installer to add IP “accessibility” to a PAL CCTV system without disrupting the existing rig. IPTX brings a mix of compression methods together with a video switch to allow it to “piggyback” on an existing matrix / multiplexer / DVR system.
This approach can “get the system on the LAN” from the point of view of making video viewable from anywhere in an organisation or remotely. IPTX can give remote access to standard VCRs or DVRs of various makes as well as to the live camera views.
DVRs and Networks
DVRs are the current fashion, essentially replacing multiplexers and VCRs with hard disk based multiplexer/recorders but still are all PAL-input machines.
In the future, recording will increasingly migrate on to standard IT-industry mass storage, in the form of such “blocks” as NAS (network attached storage) drives. These are commodity items in the IT world – networkable storage at a few pounds per gigabyte and falling. We should see a new breed of DVRs emerging which can record on external storage like NAS.
Many DVRs now have some network connectivity, so it is becoming simpler to play back recordings remotely across a LAN.
Eventually all recording will be ‘buried’ in the network, with not a DVR in sight. This is possible already, using IP cameras and codecs to convert PAL cameras to IP. DVRs can act as the ‘bridging science’ between today’s all-PAL environments, and the all-IP environments we will see increasingly widely designed.
To get video on and off a network, IP cameras and codecs are needed to convert from PAL video to IP. The image has to be digested, compressed and then converted to a stream of data packets. Several standards (and much controversy) prevail around the second two processes
Video compression
The truth is there is no one ‘best’ method. All the popular methods (MPEG2, MPEG4, MJPEG, H261, H263, Wavelet) have their strengths, weaknesses, and suit different situations better or worse. In system design, it is an exercise of choosing the right one for the job.
The transport of the packets of video is independ-ent of what compression method was used. Hence no rigid decisions on compression method need be made: the network will carry anything.
Compression is either carried out inside the camera (in the case of an IP camera) or in a box called a codec which converts a standard PAL signal to IP.
You don’t necessarily need IP cameras to go IP! If you have your favourite cameras that you use and they are not IP, you don’t need to give these up to network your CCTV system. Any camera can be put onto a network. A very important point to note in real installation design is that if an IP camera is chosen, then the compression has also been fixed as it is inside the camera. Later in the life of the site, you might wish it was something else, so in many situations, especially on larger systems which need a long life, stick to PAL cameras and codecs instead of IP cameras.
Ninety nine per cent of the world’s fine cameras are PAL or NTSC, not IP yet. Codecs will continue to evolve rapidly, and are already fairly low cost and very high performance.
Networked vs Composite PAL
Composite PAL
Networked
In five years time, there is no doubt the majority of CCTV will be carried over IP networks. So be smart and move now.
