Grains of Video Surveillance Cameras
We have the older generation CCTV cameras and modern IP cameras to choose from. Traditional cameras generate analogue signals to represent video images whereas IP cameras use computer binary methods. IP stands for Internet Protocol; it means the modern video surveillance cameras are built to work with the Internet. CCTV stands for closed circuit television; it is a category that should encompass both the older analogues and the newer IP cameras but people often say CCTV to mean analogue cameras.
The transition is abrupt in terms of technologies employed but very gradual in terms of deployment by the market. We estimate that over 80% of video surveillance systems installed in New Zealand in 2010 are based on analogue cameras. The penetration would be slightly higher in Western Europe and East Asia, and about the same in other OECD countries.
— Clarity of Videos —
Put an analogue camera and an IP camera side by side for the moment. Assume they have the same shape and colour and we will see that IP is obviously bigger than its analogue counterpart. This is because IP needs more space to accommodate the computing chips that convert analogue signals to IP. Are these computing chips justifiable for the increase in size, complexity and presumably price? Without going into technical details, the simple answer is that IP technologies have improved the resolution or clarity of video images significantly over analogue. The best commercial off-the-shelf (COTS) analogue camera has a resolution lower than the VGA equivalence whereas a good but not the best IP camera is SXGA. VGA has a resolution of 640 pixels x 480 pixels. SXGA has a resolution of 1280 x 1024. SXGA has 4 times of information density of VGA. When we multiple the 2 dimensions of SXGA, we get roughly 1.3 million. We use the term megapixels to denote SXGA.
— Video Enhancements —
IP cameras have intelligence to enhance the clarity of video images on top of the resolutions mentioned above. When we take a picture shot of a friend standing at the door of a house with his face looking at the camera inside the house, we know that his face will be quite dark if the outside is very bright. We can adjust the camera so that the face has more brightness. By then, the outside will become too bright to be illegible on the picture. If we use a good quality IP camera, it will do some brightness adjustments so that the face, the body, the inside and the outside have a reduced range of contrast and all objects on the picture will be clear and legible. Similarly, the colours of objects can be adjusted under different lighting conditions so that the display will be as close to reality as possible.
All objects emit Infrared whether it is day or night time. Infrared is welcome at night but may interfere with visible light recording if the latter is weak. Good IP cameras have Infrared filtering on/off ability. When the lighting intensity is good, a good IP camera will disable Infrared vision and produce video images in daylight colours. If the lighting intensity is weak such as at dusk, the camera will enable Infrared vision and produce clear video images in black and white. The clarity is as good as under bright light but colours are coded as greyness. The band for switching is between 0 and 10Lux roughly. Lux is a unit of illumination (one lumen per square metre).
When lighting is all gone and it is complete darkness, the camera will emit Infrared to assist image capturing. The Infrared rays may reach 30 metres and objects within the distance will be captured with clarity in black and white.
— Multiple Video Streams —
Some IP cameras, not all, are capable of sending 2 or more streams of video images to the connection fabric. Why would we want 2 or more streams as we know that a fixed location (not moving) and fixed oriented camera (not panning) does not see more than one scene at one time? The answer is 2 or more different frame rates or protocols (conventions) of packaging. One stream can go to the recorder which demands a high frame rate such as 8 fps (frames per second). One stream can go to a web server or a remote client for real time viewing at 1fps to fit within the bandwidth restriction. If the viewer is interested in some events, he or she can go to the recorder for higher frame rate images.
There is also a type of IP camera called PTZ. P stands for panning. T stands for tilting. Z stands for zooming. They cover 3 dimensions of space. They are good for live viewing but not as good as a fixed camera for recording evidence at a location.
— Deterrence or Evidence —
PTZ cameras are ideal for state of affairs monitoring as it covers a larger space than a fixed camera. Some models are capable of 180 degrees and some 360 degrees. The speed of rotation or movement can be adjusted and they have some deterrent effect due to their visible movements. However, burglars like Spiderman and Batman know how to avoid them.
A camera that is chunky and looks like a gun (like the one used by the police to check car speeds) would have the best deterrent effect. A signage with a camera icon and the words “video surveillance cameras in operation” would achieve the same level of deterrent effect in public places. Please smile as a camera is facing you. We will all behave whenever we read such signage. What about a dummy camera (camera body with no guts)? It would be fine too.
Whilst we want to catch criminals, criminals want to “catch cameras”. Many sites have reported loss or vandalism of installed cameras and most of those cameras were visibly intrusive or easily accessible. Dome shape cameras (dome housing) are the answer as they are not as easily stolen and are less intrusive than other shapes.
This brings us to evidence instead of deterrence- the clarity of evidence, the availability of evidence and the retrieval of it. Clarity rests with the camera as the camera is the device doing the image capturing- garbage in garbage out. The availability and retrieval aspects are dealt with by software in the server or recorder which is outside the scope of this paper.
— Cost of Installation —
Which type of camera is easier or cheaper to install? The answer is IP in most situations. Why? IP has 5 clear advantages over analogue cameras.
IP connects to the recorder through standard Ethernet local area network cabling. Analogue uses the more expensive BNC co-axial cable material which happens to incur higher cabling labour as well. IP can use an existing cabling structure. Analogue must use dedicated cabling and cannot be shared with another analogue camera.
When the connection distance is long, analogue may not work due to a high rate of signal deterioration. IP can use a standard and low cost Ethernet Switch as a signal booster in addition to the inherited advantage of surviving a longer distance than analogue in the first place.Tags: dedicated cabling, higher cabling labour