Closed circuit television (CCTV) has progressed rapidly in recent years, with all manufacturers and installers offering High Definition (HD) solutions at lower prices than previous lower resolution models. Justin Bentley introduces the basics of the technology, to allow facilities managers to understand specifications.
There are two common resolutions in HD cameras, 1080P (1920 pixels x 1080 pixels) and 720P (1280 pixels x 720 pixels). The numbers refers to the number of pixels vertically in the image. The “P” means that the image is progressively scanned as opposed to a conventional interlaced scan. For comparison, the common resolution for analogue cameras is 704 pixels by 576 pixels (known as “Full D1”). There are also cameras available with higher resolutions than 1920 x 1080, although frequently the increased resolution comes at a cost of reduced frame rate.
The rise of HD
The first HD cameras to arrive on the market are referred to as Internet protocol (IP) cameras and use the same standard network cabling as used by computer networks, with the images compressed and sent digitally. These cameras are sometimes referred to as H.264 cameras; however “H.264” is simply the compression format used by the cameras before transmitting images. In the majority of cases IP camera systems are connected to the existing computer network. While reducing installation costs, this means that the IP cameras are fighting for the finite bandwidth with other devices on the network, which can slow down access to Internet and network drives for computer users and create a time lag and/or frame judder for somebody watching the live CCTV images. In some cases the frame rate is reduced to lower the bandwidth usage by the CCTV system; security of footage also becomes an issue, with image encryption, or secure sub networks required to restrict access to CCTV data.
More recently, High Definition Serial Digital Interface or HD-SDI cameras have been developed and they transmit their images by coaxial cable. Although this is the same wiring used by analogue cameras, the information is transmitted in a digital format. This can offer multiple benefits, including using existing wiring when upgrading from previous analogue systems, not needing to involve IT departments or risk having an adverse effect on the computer network, and always receiving real time images. There are, however, some limitations: maximum cable runs are limited to approximately 100m, although this can be overcome if a greater distance is required by using signal repeater devices; quality of cable can also affect performance, so older or lower quality cables may need replacing. Unlike analogue signals, which gradually decrease over distance and can be affected by interference (electrical noise), as the signal is digital it will either arrive with the transmitted clarity or not arrive at all if the cable is too long. Newer XR (eXtended Reach™) technology coming onto the market will help increase future cable runs to 300m in some cases.
Recording and storage
The storing (recording) of images also creates options. Images from individual IP cameras can be viewed, subject to access permissions, theoretically from any personal computer using a web browser or specific software. To enable the viewing and recording of multiple IP cameras, you have the option of using a purpose-designed personal computer (PC), incorporating sufficient processing power, storage and appropriate software to allow monitoring of multiple cameras; alternatively there are purpose designed Network Video Recorders (NVRs). NVRs feature high performance components that are capable of processing video from numerous multi-megapixel cameras simultaneously in a stable environment.
HD-SDI cameras require similar equipment for recording, although it is normally more expensive as it requires additional technology to receive and convert the video feed from your security cameras into a format that can be viewed and stored. This is either built into purpose-designed equipment, in this case referred to as a Digital Video Recorder (DVR) or by adding a DVR capture card to a PC.
Where you wish to use a number of different camera technologies, eg where there is to be a partial system upgrade mixing newer HD cameras with existing older analogue equipment, many manufacturers offer hybrid recording solutions, which combine the different inputs into one storage and viewing device.
PC-based recording devices are frequently easier to use, especially as most people are familiar with navigating around different screens and software. In addition, they come with software that provides live view, remote access, and other administrative features that allow you to personalise your requirements and make your DVR more than just a recorder. PCs can also be more flexible as a system increases in size, with the option of adding additional or larger capture cards. The cost of high performance components, however, means that this is not a task for a budget PC and hence this may end up being an expensive solution. Many crashes, system lock-ups, and instabilities can be blamed on computers that do not have enough processing power for handling multi-camera video processing.
Standalone recording devices are not as feature-rich as their PC counterparts, but are a solid alternative for those less comfortable with PCs or for locations where the use of a PC is inconvenient.
When selecting a recording device, consideration should be given to both existing needs and the ability to expand the system. Storage should be sufficient for both current and future anticipated needs. Some systems allow storage for lengthier periods by reducing either the frame rate or the resolution of the image stored. If you specifically want to be able view recordings at full HD 1920 x 1080 resolution and with a high enough frame rate to create a smooth recording, make sure that this is specified and provided for, with both the recording device and any monitors.
It is not just the resolution of cameras that has improved in recent years. One example is where the area being viewed has suffered due to bright background lighting, leading to the persons or items being monitored appearing darkened. Some cameras now can compensate for this by using a dual-exposure process, originally used in still photography, which compensates and increases the amount of detail captured.
Camera sensitivity has also increased, allowing cameras to operate at lower light levels. Low power infrared LEDs are frequently built into cameras, allowing security cameras to discretely “see” in dark areas by flooding the area with infrared light. This light is not visible to the human eye, although it reflects off surfaces in the area and is picked up by the camera's sensor chip, which allows the camera to see as if the area were lit by visible light. Cameras or external infrared lights will normally specify an illumination range, ie the maximum distance at which an object is visible at night.
While technology has improved the quality of images that are possible, there are still issues that can negate these advancements. Camera locations should be firm to prevent camera shake, especially in windy conditions. Consideration when selecting locations should also be given to bright lights, which can blind a camera, whether these are natural lighting situations, eg sunrise or sunset, or night-time lighting, eg flood lights. Maintenance and regular cleaning, especially of the lens and housing, will ensure that images remain of the highest quality.
When the Data Protection Act 1998 was introduced, owners of CCTV systems examined their systems and procedures and put into place measures to ensure compliance with the legislation. With the improvements in technology, we should consider how this has changed the systems and whether any alterations to internal procedures are required in order to remain compliant.
The CCTV Code of Practice issued by the Information Commissioner’s Office advises that “image capture [be] restricted to ensure that they do not view areas that are not of interest and are not intended to be the subject of surveillance”. Therefore when replacing an existing camera, consideration should be given as to whether a higher resolution camera means that items in the background are now identifiable and hence surplus data is now being collected.
Another area that should be examined is access to the data, both in limiting who can access the images and being able to take a copy when required, eg for evidence. Where images are transmitted through the computer network, ie IP CCTV, the storage device is also connected to the network. It should be noted that many recording devices for HD-SDI and/or analogue cameras also have a network interface — this is not limited to IP CCTV equipment. Data security needs far more consideration; the data controller needs to check that any images transmitted over a network are encrypted, and that it is not possible for network users to access the storage location.
Advancements in technology have made it easier for images to be copied to portable permanent storage. With USB connections frequently used, data can be copied to an external hard drive or data stick. Persons with legitimate access to CCTV footage need to be aware of their responsibilities and it should be made clear that images should only be copied for legitimate reasons and that misuse of data is a disciplinary offence.
A clearer picture
It is not all negative, however, when looking at data protection and the latest equipment. When considering data as evidence, previously images were often of insufficient quality and the integrity of the evidence could be brought into question if time stamps were inaccurate. HD CCTV provides clearer and higher resolution images. Digital recordings as opposed to previous analogue recordings onto video tapes also mean that there is far less chance that an image will be corrupted due to the storage method. Equipment connected to networks, even if not using the network for transmission of images, will often automatically check and update the system clock, meaning that time stamps are accurate. Therefore images from modern equipment are more likely to be fit for purpose and able to be used in the event of a prosecution.
In October 2012, the Independent reported that the Government's surveillance commissioner Andrew Rennison had warned about CCTV systems capable of identifying and tracking a person's face from half a mile away, thus turning the UK into a “Big Brother” society. While this may be relevant to local authority CCTV, as far as security systems used in the private sector are concerned, the latest technology will be used to identify people in the same area as previously, only now it will be far better quality.
Last reviewed 2 July 2013