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• to monitor or crowd control the target shall represent not less than 5 % of picture height (or more than 80 mm per pixel)

;

to detect the target shall represent not less than 10 % of picture height (or more than 40 mm per pixel);

to observe the target shall represent 25 % of picture height (or more than 16 mm per pixel);

to recognise the target shall represent not less than 50 % of picture height (or more than 8 mm per pixel);

to identify the target shall represent not less than 100 % of screen height (or more than 4 mm per pixel);

to inspect the target shall represent not less than 400 % of screen height (or more than 1 mm per pixel).

Figure 1

Since the influx of digital systems to the CCTV market there is now variability in the capture, recording and display resolution. So a “Recognise” requirement can no longer be simply equated to a 50 % screen height. For instance, through the use of megapixel cameras and high resolution displays it is now possible to provide the same image resolution as before using a smaller physical percentage of the screen.

Conversion tables have therefore been devised to show how the traditional percentage screen height criteria for the mentioned PAL (576i) system will look under a range of non-PAL resolutions. 576І has an equivalent progressive scan vertical resolution of approximately 400 pixels (see Kell factor), this figure has been used in the tables below. Table 2 shows the resolutions commonly encountered and Table 3 shows the equivalent screen heights needed to maintain the required resolution. These figures should be used only as a guideline to the proportion of the screen filled by the target as other factors also effect the available information in the image, see in particular 13.3.

Table 2 — Commonly encountered resolutions (in pixels)

Table 3 — Person screen height equivalent for different digital resolutions (in percent)

Camera placement shall be based on achieving an optimum view which shall not be compromised merely for ease of installation.

When setting up a camera field of view it is important to consider other environmental or scene specific content, for example:

Foliage: There is a seasonal variation in foliage, which could block the view. Trees and plants grow overtime which could also block the view.

Illumination: There might be spot lighting from external light sources and time controlled lighting which could impact the view.

Sunlight: Depending on time of day and seasonal variations the position of the sun could produce glare or provide poor illumination conditions.

Reflections: Windows, buildings, bodies of water or any other reflective objects can result in poor or excessive illumination conditions which can compromise the desired captured image.

Street furniture I signage: Temporary or new permanent structures such as signs or other buildings may block the field of view.

Scene activity: If a specific task is required ensure that other scene activity does not compromise the desired image capture, for example a busy footpath in front of a doorway could occlude an identification shot.

Where person identification is the main purpose of the camera, the camera should be mounted around head height; cameras mounted significantly above head height may not be able to provide a full view of a person’s face.

The existing lighting shall be evaluated for the level, direction and spectral content. Optimal light sources are those which have a spectrum that best matches the camera imaging device response.

If additional lighting is required, the number, type, siting and power of the light sources shall be determined taking the following parameters into consideration:

• light efficiency and photometric performance of the light source;

• shape of area to be surveyed by cameras: narrow or wide, spot or flood;

sensitivity and spectral response of the cameras, particularly colour cameras;

reflectance of the materials making up the majority of the surveyed area;

time delay to reach the specified light output of the lamp after application of power;

the loss of light output of the lamp due to ageing and lamp failure for example, LED-based illuminators can suffer degradation, in order to deliver a constant level of lighting performance throughout the life of the illuminator a compensation mechanism may be necessary;

the new or additional light source selected shall give acceptable pictures under all likely working conditions;

illumination over the scene being surveyed shall be as even as possible avoiding any area of very low light illumination. The ratio of maximum to minimum illumination within the covered area of any scene shall ideally be 4:1 or better;

where possible lights shall be mounted so that they do not impair the camera picture quality, for example by producing heat haze in the field of view. The preferred position for the light is above the camera. The camera shall not view the scene through intense beams of light;

where possible the light source should be a minimum of 2m from the camera. Light sources attract insects which can cause overexposed hot spots , as can objects such as raindrops, snowflakes and falling leaves, this is of particular importance where VCA / VMD is used;

the light sources should be located within a short distance to the object to be monitored;

all illuminators including non-visible shall be positioned observing the minimum safety distance to prevent eye damage;

there shall be safe access to the lamps for bulb changing;

particular attention shall be paid to the direction of illumination. The aim is to produce a maximum of contrast for intruder detection. An object can only be detected if its brightness is different to that of its background;

for inspection, identification and recognition purposes, illumination shall enable detailed features of the object as stated in the operational requirement to be observed. If an accurate personal identification is required, it is recommended to direct the light sources into the expected direction of movement i.e. the faces of the targets should be illuminated;

constant illumination or quickly changing lighting conditions, static or transient highlights in a uniform picture;

environmental influences on visibility like rain, fog, etc.;

if an additional light source is necessary, but illumination by white light is not desirable, IR spotlights and IR-sensitive b/w cameras or IR cameras can be used;

illuminators with asymmetric optics can be used to increase the range of infrared illumination, helping to avoid uneven exposure of the scene;

lights shall not be positioned such that they directly face cameras;

high sensitivity cameras or fast lenses with large aperture can be used to avoid the need for additional lighting.

The different functionalities of a CCTV system may be covered either by physically separate components or devices, which cover multiple functions. They may be distributed over an IP network.

The functionality of image encoding and streaming may reside in video encoders, or combined together with image capturing in IP cameras or megapixel cameras; image storage may be accomplished by NVRs or network storage devices; if combined with image encoding, a DVR may be used. Video content analysis (VCA) and video motion detection (VMD) may be offered by all of these devices or separately in VMD devices or VCA servers. The image presentation on video displays may be done by video decoders or PC based workstations. All of this equipment may be monitored and controlled by a supervising Video Management System (VMS).

Once the CCTV camera has been installed and commissioned it is essential to the successful operation of the CCTV system to maintain the agreed field of view. The camera shall be installed in such a way that it is difficult for an intruder to change the field of view for the camera. This should be achieved by installing in a suitable location/height, the use of appropriate physical mounting and possibly further by the use of security fixings. Furthermore the interconnections (e.g. cabling, antennae) should not be accessible and/or able to be torn off.

Depending on the security grade , if selected in the OR, of the CCTV system/camera, automatic methods shall be deployed to detect the change of field of view of the camera according to EN 50132-1:2010, 6.3.2.3.

Consideration shall be given to the detection of loss of signal and camera obscuring or blinding on any connected camera. An audible and/or visual system alarm shall be generated for acknowledgement by system operators and a facility shall exist where this alarm can be mapped to an alarm output for connection to an alarm system, if defined in the OR.

The primary method for protecting the centrally located components of a CCTV system, such as image storage, control equipment, from tampering is to install the system in a suitably secure location (see clause 12.6), with appropriate access controls to both the location of the system, and the system/equipment according to EN 50132-1:2010, 6.3.

For the combination and integration of other security systems into the CCTV system or vice versa the general requirements of CLC/TS 50398 should be applied.

For an individual integration of a CCTV system into any other system or vice versa, the integrator needs a full specification on the offered interfaces. In the next step an integrator needs to develop a programmatical implementation to operate the requested interfaces. This applies to systems with vendor specific interfaces.

Alternatively the integrator may choose different security applications from a single source, where all components are manufactured as a single brand by one vendor. The integration is limited to the offered products by this vendor and it is not possible to select the 'best of breed' or expand the system at a later time by other brands or upgrade to new equipment.

Open Video Management Systems (VMS) or Frameworks may be chosen, where components from several vendors may be integrated via plug-ins, drivers or open interfaces. These IP video devices and their interface should be compatible to the general IP requirements of EN 50132-5-1 in terms of: IP connectivity, video stream transport, video payload, stream control, eventing and device discovery and description. If the end­user selects a CCTV system or video components, which are based on interconnections compatible to EN 50132-5-2, either based on REST or on Web Services, the integrator only needs to take care that the integrating system is compatible to this EN 50132-5-2 implementation.

The integration of a CCTV system may include video streaming, control, eventing, configuration, discovery and description and other interfaces.

6. Image presentation

   1. Display types

The image presentation device(s) should be selected after taking account of the nature of the image viewing task, the conditions in the control room or other viewing space and whichever of the criteria in Table 3 are considered to be relevant. It should be considered whether displays are also used for viewing maps, floor plans, device lists, system status, alarm conditions, etc.

In simple terms displays come in two main forms, the CRT (Cathode Ray Tube) or the modern flat panel variety. Less commonly rear projection systems are used. The flat panel displays can either be LCD (liquid crystal display) or plasma. Examples for display technologies are shown in Table 4.

Table 4 — Examples of display technologies

Size: Large size and high resolution flat panel displays can be effective as matrix displays for multiple cameras. High screen resolution will not improve the capture resolution. Rear projection video walls adds seamless display of a mix of cameras and graphical canvas containing mapping, floor plans.

Heat: The amount of heat a unit generates becomes significant as the size of the facility and number of displays increases and can impact not only on operator comfort but also on machine efficiency and air conditioning cost.

Colour: Modern displays of all types have similar quality colour reproduction.

Brightness: The light output of a display in Cd/m². The brightness of a display shall be adapted to the lighting conditions of the environment. As a rule of thumb, the brightness level of bright content on a display should correspond to the brightness of a white sheet of paper held in front of the display. This is to avoid eye-strain due to brightness variations.

• Contrast: The ratio between white and black measured in a dark environment. This eliminates the influence of lighting in the room. As such, contrast has only an indirect influence on picture quality (see black level).

• Black level: The ‘black level’ of a screen refers to how well black image content is perceived in a normal lit environment.

A good lighting layout in the room and the use of anti-glare technology on LCD screens or dedicated rear-projection screens is required to maintain good image quality.

• Burn in: Most screens can suffer from ‘burn in’ or image retention, where if the same background is displayed continuously for a long period, this can leave a permanent mark on the screen. Plasma and CRT screens have permanent burn-in. LCD shows reversible image retention on static content in a few months. Rear projection (using DLP technology) is image retention free.

7.2 Resolution

Display screens have different resolution depending on set-up and type. Display resolution shall be selected to match and complement the camera resolution and resultant video resolution. For larger display surfaces, the efficient display resolution can be defined according to the minimum visible size of a pixel.

The size and resolution of display screens should be considered together with the recommended display sizes in 12.4. An operator placed at a large distance may not be able to discern the details of a small high resolution monitor.

A 50” full HD display has a pixel size of 0,57 mm. A person with average eyesight can discern a single pixel up to a distance of 1,98 m. Table 5 contains a few additional values.

Table 5 — Resolutions

Rule of thumb: Distance (mm) = Pixel size (mm) / 0,000 290 7

8 Transmission

Video can be transmitted and consumed either as an analogue or digital stream, it may be compressed or uncompressed. Each video type can be converted to the other. Conversions should be kept at an absolute minimum to preserve video quality throughout the whole CCTV system.

The purpose of the transmission subsystem in a closed circuit television (CCTV) installation is to provide reliable transmission of video signals between the various CCTV equipments in security, safety and monitoring applications.

The video transmission subsystem needs in a security application to transport not only the video content itself, but also video related control (e.g. for replay), event and status signals.

The end user, installer and integrator need to decide on the adequate video transmission subsystem. Today different kinds of video types and ways to transmit video exist: Analogue, Digital and IP; compressed and uncompressed; standard and high resolution; dedicated and shared interconnections; wired and wireless, short, long distance and remote:

For analogue non compressed video signals the transmission subsystems may consist of dedicated cable transmission media such as coaxial cable, twisted pair cable, Fibre optic cable. Wireless transmission methods may include microwave, Infra red or radio transmission. Multiple analogue video signals may be combined in one physical transmission path using multiplexing techniques.

For analogue high resolution video transmission a dedicated cabling for VESA and VGA signals is recommended; for uncompressed digital high resolution video a transmission according to the HDMI and DVI standard is recommended. These types of video transmission are quite common for the connection of high quality video displays over a short range of about 15 m or more.

The analogue video transmission subsystem including video transmission devices such as transmitter, receiver or intermediate devices associated with the selected transmission media shall be selected by the installer and integrator in accordance with the signal and performance requirements of EN 50132-5-3.

For remote accessibility, high image resolutions, digital recording and replay, integration, scalability and other purposes of the video transmission subsystem it is recommended to use IP video. When considering IP video the most important requirement is that the IP network is able to deliver the required amount of information, especially video streams, with minimum delay, loss and jitter. These performance requirements for IP networks define the design principles of the network. A video transmission subsystem in surveillance applications needs to comply with the minimum requirements of EN 50132-5-1, Video Transmission - General Requirements. To guarantee this performance a detailed ip video design guide is given in EN 50132-5-1. Integrators and Installers should follow the network planning of this standard. It is recommended that a network specialist is consulted early in any system design.