It is important to identify your business needs when selecting a security video system so that the system can be tailored to meet those needs. Consider the primary purpose of the system i.e. is it to identify possible offenders or to guard against staff theft? Rarely will the placement of a single camera be effective in performing both these tasks well.
To get the most out of your system, choose a supplier that will provide you with both training and ongoing technical support.
All surveillance systems consist of two main parts - the camera system and the recording system:
It is important to note that the very best recording system can never make up for a poor camera set-up. Also, that the installation of a security video system is most effective when used in conjunction with a range of crime prevention measures.
For additional information on CCTV you can visit the following sites:
- Standards Australia
- Australian Security Industry Association Limited
- Managing Closed Circuit Television (CCTV) Records
- Western Australia Closed Circuit Television (CCTV) Guidelines
The Camera System
To maximise the benefits of a video surveillance system, it is important to set the camera up correctly. The recording system can only record what the camera system gives it - a poor image from a camera will be stored as a poor image on a recorder. Minimal enhancement can be applied to video images, as a finite amount of picture information is captured and stored. For example, zooming in does not reveal any further information - it will only turn a small pixelated image into a large pixelated image. To get the best results from your system, consider the following.
It is recommended that you assess your surveillance requirements to ensure adequate coverage. Consider:
- Where are the main entrances/exits?
- What are the main target areas?
- Where would best offender identification be obtained?
The best images to identify offenders are front-on and close up. High angled cameras mostly capture the tops of heads, and offender’s often wears hats, beanies or head dress to mask or obscure their faces.
A wide image is good for viewing overall movement or action, but poor for offender identification, as offenders are too small to be identified. The installation of multiple cameras allows for both areas to be covered.
Cameras within easy reach can become targets for vandals. Cameras can't see through physical obstacles such as chewing gum, paint or dirt, so placement out of view and/or out of reach is ideal. Poorly placed banners, advertising, shelving, and decorations can also obstruct camera views.
Camera resolution, lens type, focus and exposure are all important considerations when installing the system.
The minimum recommended camera resolution is 320 television lines. (This is roughly half the resolution of a broadcast television image).
The lens itself must be compatible with the camera, display minimum image distortion (i.e. bending/warping), display minimum image discolouration, and provide adequate coverage of the target area.
Focus is paramount. Nothing can compensate for a poorly focused camera system - it will produce blurry, unusable images.
The camera should be able to cope with the range of variable lighting conditions in its field of view over 24hours per day, 365 days of the year.
Camera viewing doors that open and close into the outside world must be able to quickly vary their amount of light intake in order to maintain a useful image.
To ensure the correct exposure of an image, controlling the camera's environment is often necessary. The camera may need assistance through the addition of extra lighting - this is often the case after hours, or in poorly lit areas. Images lit predominantly from behind appear as silhouettes. In this situation, compensation from other lighting sources is required to produce neutral lighting and resolve picture information. Conversely, strong light sources (e.g. the afternoon sun) sometimes need to be shut out to preserve optimum lighting conditions.
Tape-based recording systems are being superseded by digital systems, however a large number of the tape systems are still in use. There are a number of ways you can make the most of your tape-based system.
Recording onto the best format will assist in the preservation of image quality.
The number of images recorded per second affects the fluency of motion upon playback. Standard video records 25 frames (images) per second.
Timelapse recorders and multiplex systems fit long periods of time and/or multiple onto a recording device at the expense of fluency of motion/image updates.
Multiple Camera Systems
Multiscreen (most often quad screen)
Multiple cameras are broken into a multiscreen (often quadscreen) arranged and recorded so that all cameras are seen at one time. These systems are not recommended for recording, as the resolution of each image is greatly reduced (by at least a quarter). Any system that sacrifices resolution will greatly diminish the possibility of offender identification, as resolution is often the most important factor in identification of a suspect.
In switching systems, multiple cameras are constantly being switched so that only a short section (e.g. 5 seconds) from a single camera at a time is recorded. Whilst fluency and image resolution can be maintained when the selected camera is being recorded, an offender may appear on another camera that is not being recorded at all.
Multiplex systems use encoders to switch multiple cameras at very high speed into a jumbled image stream. Upon playback, the image stream is played through a decoder to isolate a single camera at a time for viewing. Some resolution and fluency is lost in the encoding process. Multiplex systems are recommended over multiscreen and switching camera systems.
Tape Maintenance (If you still use tapes)
It is important not to reuse the tapes an excessive amount of times, as the magnetic surface that stores the images becomes worn away, resulting in unacceptable image quality. Most manufacturers state that the life expectancy for videotape is thirty (30) playback viewings and twelve (12) record passes.
Avoid pausing your tape too often as the magnetic surface will become worn and can become irreversibly damaged.
Touching the surface of tapes
Oils and dirt from fingertips can make replay impossible. Likewise, don't place any other foreign substance on the surface.
If an offence has been recorded, do not replay the tape excessively, as it will degrade the quality. To avoid losing the data, remove the record inhibit tabs and store the tape in a secure place for the police.
Attempting to repair tapes
Damaged tapes should not be reused. Folded or wrinkled tapes or tapes "repaired" with sticky tape are irreversibly damaged. If a damaged tape contains footage relevant to a police investigation, store the tape and police will assist with the repair and retrieval of relevant footage. Further, if the tape is jammed inside a machine, do not attempt to remove it - police will assist.
All surveillance systems require regular maintenance. Regular cleaning of the video heads and checks to ensure the machine is recording correctly are vital.
Logging of Tapes
At a minimum, your log should include starting and finishing times and the date of recording. An up to date and accurate log aids the identification of the correct tape when an offence has occurred.
Time and Date Recording
Recording the time and date onscreen as part of the picture information assists in the location of offences and examination of offender movements, however, care should be taken that the onscreen time and date do not interfere with the image content.
The time and date should be located in the least crucial area of the image (e.g. close to the roof, close to the floor). If the time and date cannot be recorded on your system, it is suggested that a clock on the wall is situated in the target area.
Image resolution is a major contributing factor to image quality. Higher resolution means that more information is stored about an image, therefore more information can be read about an image. The number of pixels used to represent the image determines the resolution of an image. Digital video for television broadcast is represented by 768 x 576 pixels. The minimum recommended resolution for surveillance systems is 320 x 240 pixels.
Digital video creates large files, so compression is crucial for the storage of this data intensive information. A high amount of compression will result in less detail in the image. In extreme cases, the picture displays compression artefacts such as pixelation (large blocks of pixels). This should be avoided as the image is degraded beyond its usefulness.
Most DVR over-record their data after a set period of time. It is strongly recommended that the DVR you choose has the capacity to archive footage to a removable hard disk and/or export any relevant sections to CD or DVD. Preferably the files should be exported in a standard format that will replay on other computers (e.g. mov, .avi, .mpg, .wmv, .asf). The exported footage should be accompanied by the corresponding decoding software or viewer application if necessary.
Replay and Viewers
Often DVR designers incorporate proprietary software into their systems that inhibits files from being viewed on other computers, and with common media players such as Windows Media Player and QuickTime. Unless a DVR-specific viewer is made available, the video files cannot be opened or viewed. This adds a layer of difficulty for police who need to replay recordings on their systems for interviews, investigations and in court. Likewise, systems that require specific hardware to enable replay or viewing of files are not recommended, as there is difficulty in converting these files into a format that is viewable on police systems and in the courts.