– Demarcation between a Large and Small System –
What constitutes a large system and a small system respectively? There is no absolute answer and there is only a relative one based on market economics. Let us base it on well published pricing information as a start. We know that analogue cameras are a lot cheaper than IP cameras. We know that DVR (digital video recorder for analogue cameras) is cheaper than NVR (network video recorder for IP cameras). Can we use analogue cameras and DVR for large systems?
Analogue cameras are cheaper than IP cameras because of the lack of high resolutions and functions that are based on IP technologies such as compression and power over Ethernet. Resolution is a key quality criterion but a good analogue camera for a large system has no lesser resolution than the same camera if installed in a small system. This is an important assumption. If it is not true, then the proposition in this paper will not work. That is, the resolution of analogue cameras will not deteriorate when the number of cameras in the same system becomes larger.
Why is DVR cheaper than NVR? It is most likely due to a cost called R&D Recovery. DVR has been around for a long time, and DVR vendors should have earned enough revenues to pay off the initial investments in research and development. NVR is a relatively new beast and more powerful. Presumably NVR pricing has included some R&D Recovery premium.
DVR has advanced over time to become a hybrid machine- half analogue and half digital. It takes analogue video streams from cameras and converts the signals to digital for storage and display. Owing to the need for video signal conversion, DVR products are normally built for 4, 8, 16 or 32 cameras.
You will find that an 8 camera DVR has a price tag of less than half of a 16 camera DVR, and similarly 16 is cheaper than half of 32. On the other hand, it is likely that an 8 camera DVR is less than double the price of a 4 camera DVR unit. This situation will make the 8 camera DVR the “sweet spot” and the most popular size among various capacities of DVR products. Any system larger than 8 cameras will fall into the category of large systems. Of-course the quantity of 8 here is arbitrary. The number can be 4, 16 or 32 because it is dictated by market economics and time.
In summary, there is a slight premium to go for a larger system within the ceiling of DVR technologies and there is a higher premium to go for a larger system based on NVR with more powerful functions.
– Low Cost Large Systems –
The word hybrid as used on DVR gives us the hint. DVR accepts analogue camera video signals and converts the signals into digital for further processing. Hybrid DVR maintains its low cost appeal but opens a path to large system size through its digital processing capability.
Suppose a sweet spot DVR takes 8 cameras. Instead of using a more expensive DVR to take 16 cameras or a much more expensive DVR to take 32 cameras, we can deploy 2 or 4 low cost 8 camera DVR units. We can even deploy 6, 8 or 10 low cost DVR units for 48, 64 or 80 cameras respectively. We will then use a PC based software package to provide a unified view of all cameras by connecting all DVR units to the PC. There is a hierarchy with the PC at the central station, DVR in various regions, and cameras in scattered locations. We normally refer the PC software as Central Management System (CMS).
To your surprise, the biggest cost saving comes from cabling for the above approach. Analogue cameras require point to point cabling to the DVR using coaxial cables which are laid by technicians from the well paid video audio industry. If we divide one big area into 2, 3, 4 or any number of small areas, obviously the distances for cabling will reduce substantially and so will the cost of cabling.
We can install a large system using low cost sub-systems. In theory there is no limit to the number of DVR units to be connected to the Central Management System. The limit will be imposed by the bandwidth of connections and the processing power of the PC.
There is a cost for CMS and the PC that runs the CMS. This additional cost would not be substantial in most cases.
– What are the Functional Limitations? –
Limitations here are in a relative sense. Limitations of analogue cameras and DVR relative to IP cameras and NVR are carried forward to large systems made up of analogue cameras and DVR.
Such a system will stay at VGA level of resolutions (640 x 480). For sure, high definition analogue cameras are available but they are not cheap. We can deploy them with the same approach if we want to.
Analogue cameras are not capable of producing dual streams feeding the central station and a mobile phone simultaneously for example.
DVR is certainly not as flexible as NVR due to the self-imposed culture of closed architecture. In the NVR world, there are independent software developers who develop NVR software for all brands of IP cameras. Their software features have to be better and are indeed better than those produced by IP camera vendors. Examples are more efficient footage storage arrangements and faster searching facilities. This situation is not seen in the DVR world.
The PC or the top level of hierarchy is an added layer. It incurs latency which is the time taken to transfer videos from DVR to the PC. It does not incur quality loss unless it requires further compression of videos for economic reasons. We can assume that the CMS does not add further functional limitation to the system.
– Does this Approach Change the World? –
It does not but the CMS approach does allow analogue based systems to be larger whilst maintaining low cost benefits. It does not change the world but it does give the world a good option.
When a system is large, the user would have more expectations from it than smaller systems. The CMS approach may or may not satisfy the user depending on individual definition of fitness for purpose and cost benefit evaluation results.
As time goes on, IP cameras and NVR units will become cheaper and eventually reach the same price point as analogue cameras and DVR respectively. This will happen as this has happened consistently as far as technology development is concerned. When this happens, the CMS for analogue camera approach would become redundant. That is, it is a plug gap approach for the next 3 years (2011-2014).
Nothing has changed the world yet.
TN Chan is the system architect of Compucon New Zealand http://www.compucon.co.nz and Computers New Zealand http://www.cnz.co.nz. He is a Chartered Engineer and has 17 years of power station engineering experience and 18 years of computer system hardware and video surveillance experience. His current roles are business management, knowledge transfer, technology appraisal, quality assurance and IPVS project management. He can be reached at tn@compucon.co.nz.
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