CCTV Systems Go Digital

July 1, 2005
Digital video delivers improved quality, which enables more details and changes in images.

With the introduction of network cameras and PC-based image processing and storage, Closed Circuit television systems are destined to become 100 percent digital.

As modern security management insists on more video surveillance, and legacy CCTV systems wear out and require repair and upgrades, the new video technologies are here to supply the solutions.

Digital video delivers improved image quality, which enables more details and changes in images, allowing faster decisions concerning the safety of people and property. Digital video also uses automated analysis and alarm tools, such as face recognition, with fewer false positives.

Unlike traditional analog cameras, digital network cameras are equipped with the processing power not only to capture and present images, but also to digitally manage and compress them for network transport.

The video camera is evolving into an intelligent sensor that can perform many functions in security management.

Besides these operational benefits to the end-user, the new video technology is readily available at lower price points. Additionally, since the hardware is trending towards being totally within the digital domain, the knowledge, tools and terminology employed in the deployment of these systems are similar to those used in the other digitally-dominated areas of security, such as access control, electronic security systems (burglar alarms) and even your own lock shop's PC.

Locks: Essential For Integrated Systems

You will hear and read the term "System Integration" being used more and more frequently when security plans are being discussed. The locksmith knows that physical security is the essential ingredient of all security.

In the past, there were obvious points of demarcation which separated the various elements of physical and electronic security. With the advent of electrically controlled locks, and now the growing availability of cameras, access controls and other electronic security components which all can speak to one another using generic network and PC protocols; locksmiths with an eye to the future are adapting to these new techniques and providing integrated security solutions.

The video industry has been going through the transformation to digital for several years. An important milestone was the introduction of solid-state image sensors, CCDs (charge-coupled devices).

The CCD has replaced the venerable Vidicon, the vacuum tube device which had traditionally been used in virtually every CCTV camera to capture the image as the first step in the process of displaying and recording video images.

The Image Sensor transforms light into electrical signals. There are two possible technologies used for the camera image sensors: CCD and CMOS.

CCD sensors were developed specifically for the camera industry and have been in use for over 20 years. Advantages of CCD include better light sensitivity than CMOS sensors therefore better images in low light conditions. In extremely bright conditions, CCD images may smear or bleed. Most high-quality cameras use CCD sensors, but CMOS sensors are improving.

CMOS (complementary metal oxide semiconductor) sensors are based on standard technology already in use in computer memory chips.

Cabling: The Next Link

The next link in the process, the interconnection between the camera and the rest of the surveillance system, also changes. Coaxial cable which was used to carry the analog video is being replaced with wired and wireless infrastructure, which conforms to the digital and network topology. Cables include those rated for network applications, such as those referred to as Cat 5 (Category 5 is a classification which defines data transmission capability of cable; there are numerous classifications) and UTP (plain old untwisted pair wire). Wireless infrastructures also abound, and include proprietary RF (Radio Frequency) protocols, the ubiquitous Wi-Fi (wireless network) and others.

Video display, recording and recording are the remaining processes involved in a video system. The hardware and software to accomplish these processes are going through a constant revolution with new developments being announced on just about a daily basis.

IP-Based Networks

IP is an abbreviation for Internet Protocol, the most common protocol for communication over computer networks and the Internet.

Network cameras are a fast-growing product category, another clear indicator that IP-based CCTV systems are poised to take over. Because of its scalability, IP-Surveillance is an attractive technology not only for enhancing or revitalizing existing surveillance and remote monitoring applications, but also for new installations.

Network cameras are connected directly to an IP-based network and integrate to applications on the network, enabling users to install cameras at remote locations and view, store and analyze live video from another location, or multiple locations, over the network/Internet.

An IP-Surveillance device creates digitized video streams that are transferred via a wired or wireless IP network, enabling monitoring and video recording as far away as the network reaches, as well as enabling integration with access control and other systems.

Digital Video Recorders (DVRs) are port-configured hardware solutions which may offer advanced features such as motion-detection, software matrix creation and network storage and connectivity (network borne input/output and control). Even as DVRs are replacing VCRs as the basic video component, DVRs themselves are being supplanted by network-based solutions. NVR & NVMS (Network Video Recorder / Management Systems) are software solutions which use generic computer and IT hardware.

This renders the limitations of NTSC and PAL irrelevant. Several new resolutions derived from the computer industry have been introduced, providing better flexibility. Moreover, they are worldwide standards.

Power Over Ethernet Technology

Power over Ethernet is an upcoming power solution for network video devices because it consolidates power and data and simplifies installation and deployment.

IEEE 802.3af standard defines the specifications to deliver power over standard Ethernet cables. It was approved on June 12, 2003, by the Institute of Electrical and Electronic Engineers (IEEE).

Power Over Ethernet technology allows appliances such as network cameras to receive power as well as data over existing LAN cabling, without needing to modify the existing Ethernet infrastructure.

NTSC and PAL Resolutions

In North America and Japan, the NTSC standard (National Television System Committee) is the predominant analog video standard, while in Europe the PAL standard (Phase Alternation by Line) is used. Both standards originate from the television industry. NTSC has a resolution of 480 horizontal lines, and a frame rate of 30 frames per second (fps). PAL has a higher resolution with 576 horizontal lines, but a lower frame rate of 25 fps. The total amount of information per second is the same in both standards.

When analog video is digitized, the maximum amount of pixels that can be created is based on the number of TV lines available to be digitized.

With digital cameras and imaging, the terms NTSC and PAL become irrelevant because analog video monitors are replaced with computer monitors.

Render Unto Video

Two different techniques are available to render the video: interlaced scanning and progressive scanning.

Interlaced scanning is a technique developed for CRT-based TV monitor displays. It is comprised of 576 visible horizontal lines across a standard TV screen. Interlacing divides these into odd and even lines and then alternately refreshes them at 30 frames per second. The slight delay between odd and even line refreshes creates some distortion or 'jaggedness.'

With the introduction and growing use of Liquid Crystal Display (LCD), Thin Film Transistor (TFT)-based monitors, DVDs and digital cameras and progressive scanning, an alternative method is becoming more common.

Progressive scanning scans the entire picture line by line every 16th of a second. This technology eliminates flickering and improves image detail, which is critical in surveillance applications. A high quality monitor is required to get the best out of this type of scan.

VGA is an abbreviation of Video Graphics Array, a graphics display system for PCs originally developed by IBM. The resolution is defined at 640x480 pixels, a very similar size to NTSC and PAL. The VGA resolution is normally better suited for network cameras since the video in most cases will be shown on computer screens, with resolutions in VGA or multiples of VGA. Quarter VGA (QVGA) with a resolution of 320x240 pixels is also a commonly used format, very similar in size to CIF. QVGA is sometimes called SIF (Standard Interchange Format) resolution, which can be easily confused with CIF.

Other VGA-based resolutions are XVGA (1024x768 pixels) and 1280x960 pixels, four times VGA, providing megapixel resolution.

Network Video Compression Standards

Without the use of image compression, most local area networks (LANs) are incapable of managing or transporting video data. Digital video is always compressed in order to speed up transmission and to save space on hard disks. Selection and use of the right compression is critical. Here is a listing of compression options.

MPEG-1: 352 x 240 pixels; 30 fps VCR Quality, MPEG-1 was released in 1993 and intended for storing digital video.

MPEG-2: 720 x 480 pixels/ 1280 x 720; 60 fps TV quality. MPEG-2 was approved in 1994 as a standard and was designed for high quality DVD, HDTV, interactive storage media (ISM), digital broadcast video (DBV), and cable TV (CATV). The MPEG-2 project focused on extending the MPEG-1 compression technique to cover larger pictures and higher quality at the expense of a lower compression ratio and higher bit-rate. The frame rate is locked at 25 (PAL)/30 (NTSC) fps, just as in MPEG-1.

MPEG-4: Wavelet based files designed to transmit video over less bandwidth and can combine video with text, graphics and animation. MPEG-4 is a major development from MPEG-2. There are many more tools in MPEG-4 to lower the bit-rate needed to achieve a certain image quality for a certain application or image scene. Furthermore, the frame rate is not locked at 25/30 fps. However, most of the tools used to lower the bit-rate are today only relevant for non real-time applications. This is because some of the new tools require so much processing power that the total time for encoding and decoding (i.e. the latency) makes them impractical for applications other than studio movie encoding, animated movie encoding, and the like. In fact, most of the tools in MPEG-4 that can be used in a real-time application are the same tools that are available in MPEG-1 and MPEG-2.

Motion-JPEG (M-JPEG): Compresses individual jpeg images at 16 - 30 images per second full motion video, depending on available bandwidth. (Individual image quality does vary with bandwidth, but frame rate does.)

Advanced Video Imaging: Mega pixel technology that permits more data and control features such as perspective correction; light level compensation; fixed field pan-tilt-zoom.

Megapixel Resolution

The higher the resolution, the more details can be seen in an image. This is a very important consideration in video surveillance applications because a high-resolution image can enable a criminal to be identified.

As a means of comparing technologies: the maximum resolution in NTSC and PAL, after the video signal has been digitized in a DVR or a video server, is 400,000 pixels (704x576 = 405504). 400000 equals 0.4 Megapixel.

Using the CIF format, i.e. a quarter of the image, the resolution is down to a mere 0.1 Megapixel.

Megapixel network cameras also bring the benefit of different aspect ratios. In a standard TV, an aspect ratio of 4:3 is used, while movies and wide-screen TV use 16:9. In a network camera, any aspect ratio can be used.

In addition, digital pan/tilt/zoom can be achieved, where the operator selects which part of the megapixel images should be shown. This does not imply any mechanical movement from the camera. It ensures much higher reliability and makes it possible for different operators to pan and tilt to different areas of the image simultaneously.

There are two different approaches to compression standards: still image compression and video compression.

All still image compression standards are focused only on one single picture at a time. The most well known and widespread standard is JPEG, short for Joint Photographic Experts Group international — a good and popular standard for still images that is supported by many modern programs. With JPEG, decompression and viewing can be done from standard Web browsers.

JPEG compression can be done at different user-defined compression levels, which determine how much an image is to be compressed. The compression level selected is directly related to the image quality requested.

Motion JPEG offers video as a sequence of JPEG images. Motion JPEG is the most commonly used standard in network video systems. A network camera, like a digital still picture camera, captures individual images and compresses them into JPEG format. The network camera can capture and compress, for example, 30 such individual images per second (30 fps — frames per second), and then make them available as a continuous flow of images over a network to a viewing station. At a frame rate of about 16 fps and above, the viewer perceives full motion video.

Automatic exposure technology is designed to adjust lightness of an image to appear as the human eye. It can be easily fooled by light sources like headlights, sun and glare moving into the camera's filed of view. Backlight compensation circuits are designed to ignore small areas of high illumination.