No noise please, we’re CCTV users

What is super noise reduction? In essence, super noise reduction technology works to improve the quality of images emanating from a given CCTV camera by significantly reducing both random and fixed noise in the picture. Not only does that generate clearer images in all lighting conditions, but also results in a significant reduction in the amount of data being recorded to the end user’s Digital Video Recorder (DVR).

There have been solutions available to aid low light level recording for a number of years. Colour/mono cameras take advantage of the higher resolution offered by the monochrome image (with the camera switching to this mode when light levels fall below that necessary to produce an acceptable colour image. Day/night cameras work in a similar way, switching over to an infra-red mode at night).

However, both of these solutions result in the same loss of colour information. Colour information which may contain crucial evidence. That being the case, the important issue here is the ability of the camera to remain in colour mode as the light fades for as long as possible before reverting to monochrome.

The anti-noise technology that has been specially developed by Samsung (defined as Samsung Super Noise Reduction, or SSNR) allows images to be viewed and recorded in colour, well below the normal operating conditions of other technologies.

Further advances in technology have allowed for greater light sensitivity. As light falls below the camera’s optimum operating level, Automatic Gain Control circuitry amplifies the video signal to maintain a higher signal level. In really low light situations, some cameras employ further circuitry to increase this sensitivity (commonly referred to as Sens-Up or Frame Integration processing).

While this means that CCTV cameras can now operate in very light levels, both of these artificial enhancements have drawbacks attached to them. They both reduce the image quality and, potentially, increase the amount of noise within the image (therefore increasing volumes of data sent to the DVR).

Evidence in the Courts

Noise in CCTV images is one of the most common causes of video material being considered as unreliable evidence, particularly in low light environments (although not exclusively, as noise is generated in all lighting conditions). Noise may be produced by differences in light levels within the field of view in all conditions as the in-built technology struggles to reconcile the ever-changing ambient lux (known as the dynamic range). This can cause more problems than permanent light levels – however low they may be – when it comes to ‘controlling’ what is rendered by CCTV cameras.

Noise manifests itself as static or moving grain, and can render CCTV images useless long before they become too dark to be of any genuine value. Sens-Up or Frame Integration processing works on a similar principle to slow shutter speed photography, combining a number of scans of the image in order to gain greater light exposure. This is fine for static subjects, but any movement within the image will result in what’s referred to as ‘ghosting’. Here, variations of movement can render an extremely blurred image.

An example of this can be seen where the end user is looking to employ ANPR (Automatic Number Plate Recognition) technology either as part of an integrated security system or for stand-alone identification purposes. The security operative’s ability to view a number plate on a moving vehicle may be rendered impossible if the technology effectively ‘blurs’ the image, rendering it unreadable to the software. Detail is often compromised by such technology, thus it’s only really of value under certain circumstances (notably where evidential recording is not required or for those applications that are non-‘security critical’).

Clearer images for end users

Once recorded, there is nothing that can be done to remove these types of noise. Tackling both of these issues is really what differentiates SSNR from other noise reduction solutions. The end result is a far clearer image with significantly reduced noise and ‘ghosting’, and much reduced file sizes for the DVR.

DVRs employ a number of compression technologies when recording images – as either a constant video stream (in the case of MPEG) or as individual JPEG images stored in sequence. MPEG compression saves data by only looking for the difference between consecutive frames in the video stream. A sequence of video with a lot of movement will result in a much larger MPEG file size than one in which there is no movement or change from frame to frame.

Noise can be produced by differences in light levels within the field of view in all conditions as the in-built technology struggles to reconcile the ever-changing ambient lux

While this is a solution for reducing file size, MPEG compression cannot distinguish between natural movement in the image and the artificial movement caused by noise.

The potential cost savings with regard to DVR investment and storage capabilities are easy to justify. They can represent a huge benefit for security managers trying to justify their budget and squeeze as much money out of the Board as possible for that spend! SSNR can reduce MPEG file sizes by up to 70%. End users can therefore record for longer periods or record at significantly enhanced numbers of frames per second using their existing DVR (or, alternatively, save money by opting for smaller capacity hard drives or storage).

Likewise, the detail recorded in a JPEG image also needs to be encoded. The more detail in the image, the more data is generated to store that image. In a similar vein to MPEG compression, JPEG cannot tell the difference between important detail and the offending noise created by low light recording.

Again, the use of SSNR technology can reduce JPEG file sizes by anything up to 40%. Not only does the end user benefit from clear, cleaner images, they also have the ability to record JPEG images at a greater frame rate without having to enhance storage capacity.

Buy-in from the installers

Samsung Techwin recently demonstrated its technology solution at the National Space Centre in Leicester.

Representatives of major installation companies, consultants, end users and members of the trade press were invited to see a demonstration of the SHC-730 camera (complete with SSNR capability) in action, and decide for themselves how it measured up when tested against various competitor products (including cameras currently specified by the invited installers).

All cameras were set to their respective factory defaults and then to optimum performance in order that a fair comparison would be rendered. One installer – Raysil Security Systems – was particularly impressed with the capabilities of the SHC-370, and has since gone on to install SSNR-based cameras at over 20 different sites, ranging from bus depots to Holmes Place Fitness Centres.

Holmes Place has a total of 60 sites nationwide that Raysil now maintain and upgrade as required. “Significant savings” have been made on its hard disk recorders, with IP technology used to monitor all of the locations.

Increased frame rates

Practitioners working in high security environments such as banks and airports will certainly appreciate the benefits to be had from increased frame rates. A major limitation of many systems has been the use of time lapse recording in order to artificially increase recording times. This has become less desirable in all sectors. It is totally unacceptable in high security environments.

As light pollution becomes an even greater issue (‘Blinded by the light’, SMT, June 2005), the ability to record without additional lighting – and yet still retain satisfactory image quality – will become a necessary requirement for CCTV managers.