VIDEO SURVEILLANCE INFORMATION PORTAL FOR CCTV Closed circuit television (CCTV) CCTV is a collection of video cameras used for video surveillance. CCTV is different from broadcast television as all the equipment is directly connected together with cables or wireless transmitters that can not be received by standard television aerials or equipment. The transmissions of the video signals are only intended to be accessible by the equipment on its dedicated closed circuit. CCTV is generally used in areas where there is an increased need for security, such as banks, airports and town centres. CCTV was initially developed as a means to increase security for banks but over time it has developed into a cost effective means of general video surveillance and home security. A basic CCTV system comprises of the following; Camera, lens and power supply. Recording device, VCR or a digital video recorder. A monitor. Wiring CCTV Cameras CCTV Cameras are available in colour, monochrome or cameras that have the ability to switch between colour and monochrome (day/night cctv cameras). The cctv cameras that switch between colour and monochrome are intended for environments of low lighting at various times. There are 2 reasons for using a cctv camera that can switch between colour and monochrome, monochrome cctv cameras are much more sensitive to low lighting environments, and monochrome cctv cameras can also be used with Infra red lighting. When there is adequate available light there is the added advantage of using a colour cctv camera for recording colour information, for example the colour of a car or a person?s clothing. The primary function of a cctv camera is to convert light into a video signal, all cctv cameras require an optical lens to focus the light onto an image sensor located directly behind the lens inside the cctv camera. There are two types of image sensor available, a cctv camera with a CMOS (Complementary Metal- Oxide Semiconductor) image sensor chip and the other more common type that uses a CCD (Charge Coupled Device) imaging sensor chip. The majority of CCTV cameras and Video Camcorders use a CCD imaging sensor, whereas CMOS imaging sensors are more commonly used in webcams, budget home security cameras and digital photography cameras. CCD cameras are capable of creating a much clearer and higher resolution image. Different types of cctv cameras are Board Cameras,C Mount Cameras,IR Cameras,IP Cameras,Zoom Cameras,Speed Dome Cameras. All cctv cameras require a power supply, these are usually 12 volts DC, 24 volts AC or 240 volts AC. CCTV Lenses As mentioned in the section on cctv cameras, all cctv cameras require an optical lens. The job of the lens is to limit and focus light onto the image sensor of the cctv camera. A lens can also automatically control the amount of light that reaches the imaging sensor, these lenses are referred to as Auto Iris (AI) lenses and are generally used outdoors where the light changes constantly during the day, at night and also in varying weather conditions. It is also the job of the lens to control the depth of field of the image, either for a wide angle image or a narrow angle image depending on the distance of the object in question from the cctv camera. Where movable cctv cameras are used a zoom lens is usually fitted to allow varying points of a monitored area to be viewed. Zoom lenses are usually controlled by the CCTV operator. CCTV Recording Devices The recording device receives and stores the images from the cctv camera, previously time lapsed VCR?s and video multiplexers were generally used in CCTV systems, but due to developments in technology digital video recorders are now more commonly used. Time lapse VCR?s allow cctv camera images to be recorded for varying lengths of time on a single 3 hour video tape, from lengths of 3 hours to over 960 hours. The problem with time lapse video recorders is that the longer they are set to record for the less video information they can record per second, similar to taking a photograph from 25 every second to one photograph every 4 seconds for example. Digital video recorders use computer hard drives to store the recorded information and can however record for much longer depending on the size of the hard drive and the CODEC being used. A DVR combines and enhances the recording capabilities of a time lapse VCR and a multiplexer. CCTV VCR and CCTV Camera Switcher When there is a requirement for recording more than one cctv camera and video switcher can be used, the cameras are connected into the switcher and the switcher will automatically switch the image being fed to the monitor and the video. The disadvantage of using a switcher is that if there is an incident it is possible that the cctv camera image will change causing the incident to be missed. CCTV VCR and CCTV Video multiplexer A multiplexer is a device that takes multiple video images and lays them onto a VHS tape, it uses the properties of the PAL signal to record as many images from multiple cctv cameras every second as possible. The video information recorded is limited by the amount of cctv cameras on the system and the length of time the VCR is set to record for. CCTV Stand alone digital video recorder A stand alone DVR is designed specifically for CCTV systems. It uses computer hard drives to store video information and an embedded operating system to control the functions of the DVR, this type of recording device is most commonly used with current CCTV systems. CCTV Digital video recorders have various settings to enable more video information to be recorded at the required times using technology such as video motion detection, this means that the images from the cctv cameras are only recorded when the information of the image changes, for example a person walking in front of the cctv camera. As previously mentioned, CCTV DVRs have a multiplexer built in which enables the user to view multiple images on the screen at any given time by segregating the screen image. Many DVRs can also be connected to a network or a modem to allow remote access. CCTV DVR Comes with High Contrast LCD Display is called Media DVR. CCTV PC based digital recorder PC based cctv DVR operate much in the way as stand alone cctv DVRs, but use video capture cards and additional software to carry out the operations of the DVR, these types of DVR can easily be upgraded to accept additional cameras by adding more capture cards. As with the stand alone DVR?s, PC based recorders can also be connected to the internet for remote access to the DVR. CCTV Network video server Network video servers are designed for IP CCTV cameras over WAN or LAN computer networks where each camera has its own unique IP address. CCTV Monitor There are two main types of monitor; the analogue monitor referred to as a CRT ( Cathode Ray Tube) and the digital monitor which is the commonly used PC monitor known as the TFT ( Thin Film Transistor) monitor. There are advantages and disadvantages for both monitors, A TFT monitor is less space consuming than a CRT monitor. A CRT monitor will display a better image of low and medium resolution cameras than a TFT monitor. For high resolution cameras, a TFT monitor can be more cost effective than using a high resolution CRT monitor. CRT monitors are usually specifically designed for CCTV systems and come fitted with a composite video input BNC (Bayonet Nut Coupling) plug. CCTV monitors are also designed for long term use compared to standard TVs and cater for higher screen resolutions. Developed in the late 1940?s as a miniature version of the Type C connector, Bayonet Neil-Concelman (sometimes erroneously called a British Naval Connector or Bayonet Nut Connector). A connector widely used in the CCTV industry, usually for coaxial cable. Easy to install and reliable with little video signal loss. A rotating ring outside the tube locks the cable to any female connector. CCTV Lighting All cctv cameras require a degree of lighting to be able to pick up an image, monochrome cameras generally work well in darker environments than colour cctv cameras. Infrared lighting can also be used with monochrome cctv cameras. There are various types or infrared lighting available, standard bulbs or LED ( Light Emitting Diode) types. Infra red lighting can illuminate areas at different frequencies, although invisible to the naked eye, CCTV cameras can see the light emitted. Depending on the frequency range that the IR lamp operates, depends on how visible the lamp glow is to the naked eye. Note however, not all cameras are sensitive enough to pick up all frequencies of infra red. Covert CCTV Camera Covert CCTV is the practice of using video cameras in locations that are not made obvious to the persons being monitored in the specific cctv camera coverage area, but it is recommended that there is reasonable cause for the purpose of covert surveillance and that its primary objectives are clearly noted, only used for the purposes of preventing crime and are not used for longer than intended. Remote CCTV Remote CCTV is the means of accessing CCTV images over a computer network or standard telephone networks. Software is used on the local PC that allows access to the digital video recorder. CCTV IP CAMERA IP CCTV refers to Internet Protocol Closed Circuit Television; traditional CCTV systems use digital or analogue cameras using analogue cables that connect to a recording device such as a digital video recorder. IP cctv cameras are designed to plug onto any existing wired or wireless computer TCP/IP network, or directly onto a broadband connection so that the cctv camera can be accessed by any computer connected to the network, this includes over the internet. Computers are used on the network to store the cctv camera images but with the flexibility of IP CCTV, the cctv cameras could be located on opposite sides of the world. Although IP Cctv Cameras can be connected directly to an existing network, bandwidth is always a consideration as the data sent from the cctv camera is likely to be much larger than standard data transferred over usual office networks which if not planned correctly can slow down the entire network. CCTV Video Signal The video signal is known as the moving image information signal produced from a video camera, we use a video signal standard called PAL (Phase Alternate Line) this is a colour or monochrome video signal that comprises of 25 images or frames per second. A new breed of CCTV cameras referred to as IP CCTV Cameras (Internet Protocol Closed Circuit TeleVision) uses a data signal which comprises of a series of computer readable still images. These cctv cameras are generally connected directly to a computer or a computer network and are accessed by software to enable the live viewing, recording and playback of the video images. One format for this moving video data is called MPEG (Moving Pictures Experts Group). CCTV Video Transmission Video transmission is the means of getting the video signal from the camera to the recording or monitoring device. The transmission can be carried over wires or over the airwaves via radio transmission. The most commonly used cable for wired transmission is RG6 coaxial cable. Network cable is being used more commonly as video is able to travel further along twisted pair cables than standard coax. Other forms of video transmission include fibre optic cables, microwave transmission and licence free radio transmission. CCTV Resolution Resolution refers to the number of definable parts of the horizontal image produced by a camera, recorded by the video or digital video recorder and displayed on the monitor. CCTV equipment manufacturers refer to this as TVL (TeleVision Lines). Minimum of 420 TVL is recommandable. The TVL of the analogue PAL video information is closely compared to the pixels of a digital image. VHS (Video Home System) recorders are capable of recording 300 lines of a monochrome image or 240 lines of a colour image, SVHS (Super Video Home System) is capable of recording 400 lines of monochrome image and 340 lines of a colour image. The recording device should be the deciding factor when choosing the resolution of a camera as a 520 TVL camera being recorded on a VHS recorder will only record 240 lines out of the available 520 lines. Digital Video Recorders (DVRs) have the advantage of being able to convert the analogue PAL signal into a digital signal at various resolutions, the downside is, that the higher the resolution of the image recorded, the larger the file size of that digital image. The conversion of the analogue PAL signal to a digital image is done using a CODEC (COmpressor-DECompressor). CCTV Codec’s A CODEC is used to convert an analogue video signal to a digital video signal either using hardware or software. Codec’s play an important role in digital video recorders; they are not only used to convert the analogue signal to a digital signal but to also produce the best quality video information at the smallest file size. This makes a big difference to the amount of video that can be recorded on a DVRs hard drive. There are many standards of CODEC, those used for video compression that you may come across are MPEG-2, MPEG-4, JPEG 2000, AVI and H. 264, H. 264 is the latest codec being introduced into the CCTV market, deriving from video conferencing equipment.
Posts Tagged ‘Systems’
CCTV Security Systems Chennai India
Sunday, October 11th, 2009Choosing Analog Or IP Camera Systems For Video Surveillance (CCTV)
Friday, October 2nd, 2009The discussion among security and surveillance video manufacturers, systems integrators, and end-users about the relative advantages and indications for different kinds of video installations is easy to oversimplify. Simplification aids end-user decision-making and furthers the business interests of equipment manufacturers and systems integrators. Industry writers also have good incentive to simplify information. The many motives include making a larger point, supporting a specific-case argument, and getting and keeping readers’ attention. Simplification most often leads to statements like “IP video is more expensive than analog video,” which are true with so many exceptions that they are not actually true at all – studies sponsored by interested parties have shown the opposite to be true, and editors and bloggers have covered the studies’ findings widely. In fact, oversimplification often leads to an assertion and its opposite both being true. Another manifestation of oversimplification is the argument that each installation is so unique that no useful rules-of-thumb can be developed. In this paper we provide as simple as possible an explanation of the factors which indicate analog, IP, and hybrid IP/analog video systems respectively. This paper seeks to provide a reference for editors, end-users, and integrators who may need to evaluate a specific case or understand the general principles. Indications for choosing a pure IP camera system Ability to use an existing IT network – In some cases, digital video video systems with IP cameras can be plugged into the existing IP infrastructure. And other times the cost for the upgrade to the network to make it viable for video is easily managed. A user with an existing Ethernet network which is able to handle large amounts of data, who just needs a few cameras or plans to record low frame rates or low resolution, is a good case for a pure IP system. Recording at the “edge” of the network with only occasional requests for video over the main network may also provide a way to implement IP video on existing infrastructure. Quick and easy data protection – In many mission-critical recording environments, lost or missing data is not acceptable. IP systems can shorten response times and speed up DVR reassignments. In cases where a DVR goes offline, the user can use software to reassign the camera to a different DVR without making any wiring changes. Response times recording problems are also fast, since the recording systems are monitored at the IT network management level alongside all the other servers, routers, switches, and network applications. Ability to move and add cameras easily – Users with fluctuating camera counts and locations can avoid the need to power down recording servers to add, move, or remove cameras. This means seamless, pain-free recording from existing cameras, rather than scheduled downtime with alternate-server recording or missed recording. Ability to collect megapixel images – Users who need really high-resolution imagery want the ability to selectively deploy network cameras providing images with resolutions at least four times higher than analog images – which means much more detail than an analog camera (which is limited to standard image dimensions that do not exceed 704×576 pixels (PAL) or 720 x 480 pixels (NTSC) image after the signal has been digitized in a DVR or a video server). Megapixel cameras can collect so much information that you can zoom in to catch the smallest, subtlest detail of a video frame. Megapixel IP cameras can provide superior, unambiguous images of point-of-sales transactions and other events that can be used for business intelligence, loss prevention, and security. Ability to use facial recognition analytics – Facial recognition software depends on high-resolution images to be effective. Any camera being filtered for facial recognition should have more than the 704×576 pixels (PAL) or 720 x 480 pixels (NTSC) provided by an analog camera. Minimum disruption and installation expense – Even in cases where a new Ethernet network needs to be installed to handle video traffic, pure IP surveillance systems are less disruptive to install than their pure analog counterparts. Unlike IP systems, analog systems require the installation of a direct coaxial, Fiber, or UTP cable running from every camera to a DVR, as well as additional encoding hardware to be installed on the DVR itself. IP systems can also distribute the power and HVAC loads to help users avoid expensive and disruptive site modifications to HVAC and other site features. Need for video transmission over wide geographical range – Putting video on the IT network makes it possible to use switches, hubs, and routers to expand the network to a broader range. Analog cameras have significant transmission limits over wide surveillance areas, and they are not appropriate for some wide-area installations due to their need to be physically cabled to a DVR. Need for advanced features like digital zoom, which are not available in analog cameras – Many new IP cameras have on-board encoding and analytics as well as sought-after features that certain users need to successfully implement their surveillance plan. Need for camera-level redundant recording – Some IP cameras can provide redundancy by recording onto built-in memory cards. Indications for choosing a pure analog system Analog can meet user’s recording needs for a lower cost – There are many lower-end, low resolution IP cameras that are low in cost. But high-end IP and megapixel cameras are very expensive, and the disk capacity required to store the higher volume of video data is a very significant increased expense. Across a network array of hundreds or thousands of cameras this cost can be prohibitive. A large network of IP cameras will usually require the installation of a separate network so traffic doesn’t exceed bandwidth. An installation of just 40 cameras of 1000 Kbps-1 Mbps each will overtax many existing corporate networks. Many high-end analog cameras, though limited in resolution to 704×576 pixels (PAL) or 720 x 480 pixels (NTSC), use image processing, automatic back focus and imager sensitivity to produce images that are superior in quality and clarity to a similarly or higher-priced IP camera. The cost advantage of analog recording is especially true for users who already have a legacy coaxial or UTP wiring in place and do not need to install a large number of cameras (analog cameras require a lot of wiring, which can be expensive and disruptive in terms of site modifications). Network traffic exceeds the user’s existing capacity – IP camera recording and viewing will increase network traffic, especially with lots of IP cameras or with or megapixel cameras. If recording will exceed the existing network capacity, a user will need to add the costs of installing an additional network for the video to the operational and equipment costs of pure IP when comparing it to analog and analog-IP hybrid options. Ability to avoid hardware upgrade expenses – IP cameras tend to rely on the processing power of the CPU. Many analog systems use additional processors to share the video processing with the CPU. But an IP camera stream comes into the network port and requires the CPU to be recorded and viewed. This limits the number of IP cameras that can be added the load the server systems are able to process. These factors depend on bitrate and video encoding format (MJPG, H. 264, MPEG). And most IP cameras send large files (MJPEG) to the server to process and store. These files provide a good image but are very large and consume large amounts of storage very quickly. Newer compression formats on the horizon for IP cameras will help address this issue. Need for minimum latency – Latency is defined as the time it takes for an image captured at a camera source to be presented to a system user. Every camera has latency to a degree, because the data travels from one location to another. It is much greater for IP systems, however, because their signals need to be encoded at the source and then must travel through the network to the decoder in order to be presented to the user. Because analog signals are point-to-point (camera-to-monitor), they don’t have the additional latency caused by network routing and the encoding and the decoding process. Because of this they are typically preferred in industries such as gaming and corrections. Need for system to suit staff abilities – Many businesses operate without complex or extensive computer systems and do not have a need for the dedicated IT professional(s) required to provide timely and effective response to network emergencies on a system of any size or complexity. Wider camera variety and choice – There are a large variety of Analog cameras (for instance, mini covert cameras and pan-tilt-zoom cameras in various sizes and shapes) to choose from. With IP cameras, not every vendor has many varieties and not every vendor’s surveillance software supports others’ cameras. In many organizations, physical security staff takes care of the surveillance system administration as well as the overall security plan design and implementation, and there are no existing IT needs that require IT professionals. Vendor relationships and support – Vendor relationships have the power to greatly enhance or greatly damage the user experience and dissolve the integrator’s margin. Integrators and users at installations that already have analog cameras have an existing relationship with the manufacturer, so support and trust in the product are already in place. If the camera or DVR manufacturer with whom a relationship exists doesn’t have/support IP cameras, a new relationship of trust and access to support must to be developed. Indications for choosing a hybrid IP/analog system (A hybrid system will provide many of the advantages of the pure systems on a per-camera basis. The following are true only of hybrid systems. ) Ability to add IP camera recording to existing investments in analog – Where there is existing analog infrastructure, the hybrid approach allows the user to avoid expensive replacement of their existing analog cameras and wiring. Instead, the user can add IP cameras to their surveillance resources and record from both analog and IP cameras in the same DVR. The right camera for the each site – Hybrid recording allows the user to choose analog cameras or IP cameras according to the recording requirements and conditions of each camera site. A site requiring the lowest possible latency will call for an analog camera, whereas a site using facial recognition or other data-hungry analytics will need an P camera source. Minimal retraining expenses – Surveillance operators familiar with an existing analog-system user interface will be able to manage new IP cameras without disruptive and expensive retraining. Using hybrid DVR/NVR recording allows integration of IP cameras with little change to the end user’s normal routine.