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Potential of IP CCTV for modern video surveillance of cities
Video surveillance systems based on Internet Protocol (IP) provide remarkable improvement of functionality, including live monitoring, recording the video, and playing back the archives.
Preview, recording, playback
The heart of every CCTV system is Digital Video Recorder (DVR) that processes camera signals (video) for live monitoring, recording, and playing back. Systems based on DVRs have a limited number of video channels - further extension of such a system will require to employ next DVR/DVRs. DVRs can operate as independent units, or can be manged via IP network by an external managing software. An inconvenience of non-IP systems is limited number of frames per second that can be processed/viewed/recorded and limited image resolution of the recorded material. It is especially troublesome e.g. when certain area is monitored by a single camera and image resolution is insufficient for identification purposes.

CCTV system based on DVR
IP CCTV systems are based on PC servers. Their potential is limited only by the features of the components used. In case of higher requirements, it will be enough to change the components that restrict the system capacity. Normally, an extension of the system consists in license upgrade (next channels), and the new hardware does not disturb the structure of the system.
Another important feature of IP CCTV systems is scalability, connected with their distributed structure. The system can be based on a number of servers and client stations. Operational properties of such a system depend on its configuration and access rights of the users. The recording servers and client stations can be physically located anywhere in the system.
IP CCTV system: multi-server - multi-client structure
Cameras
The main quality feature of a camera is image resolution. Due to TV standard requirements, e.g. in PAL systems it is limited to 720 x 576. Digital systems do not impose such restrictions - image size/resolution can be shaped freely. Aside from popular D1 equipment (PAL-compatible:720 x 576), megapixel cameras rapidly increase market share. 1.3 Mpix camera (1280 x 1024) provides three times the pixels than standard PAL camera. Depending on requirements, there may be used 2 Mpix, 3.1 Mpix or even 5 Mpix cameras.
Megapixel cameras allow to monitor much larger area than standard devices, or - with other lens / lens adjustment - can provide much more detailed images. It is especially important e.g. in the case of identification of license plates.
Large and efficient video surveillance systems are using "intelligent" cameras that relieve the main part of the system of some functions. The DVRs/NVRs only record the video streams that are already compressed in the cameras (and the recording process is triggered e.g. by motion detection performed also by the cameras). Such "distributed intelligence" makes the system more reliable and effective - the server does not have to process all the information, the transmission is limited to the pre-processed data.
Comparison of various resolutions
Video data transmission
Analog monitoring systems were built on the principle "one camera - one cable", so that a 50-camera system required to use 50 cables which had to be connected to the DVRs. Packet transmission allows to change the structure of the system completely. Depending on the transmission media and other factors, there is available certain bandwidth which cannot be exceeded. This is practically the only restriction. If, for example, the bandwidth is 50 Mbps and a single camera is streaming 5 Mbps, it means that the total capacity of the link allows to use 10 such cameras at the same time. The technology does not require star-shaped structure - it may take form of an Ethernet bus, fiber-optic ring, or popular wireless network.
Of course, there is no obstacle to combining different kinds of transmission. As an example - the cameras that are connected to a system wirelessly (via several nodes of local network) can also stream video to the monitoring center via fiber-optic ring, doubled by Ethernet cable.
The architecture of analog CCTV sytem
The architecture of IP CCTV sytem
Client stations
Client stations are the control points of the system. They have to ensure operational control of the system, but cannot influence the core functions that are essential for security and reliability. It reduces a risk of sabotage. The operators have access to images from cameras, can control PTZ cameras, can play back the archives, export some data to external storage media, but they cannot stop recording operations, or switch off the cameras. The control of the system does not change its main configuration, which guarantees safety and stability of the system.
Client stations are often equipped with consoles that make it easy to control PTZ cameras, printers and DVD recorders for archiving purposes.
IP video surveillance system with two client stations
Alarm points
In some situations audio transmission can add a new functionality to the system. In many cases sound information can have key significance. The system can be, for example, equipped with sound level detector, responding to shout, scream, explosion.
Bidirectional audio transmission can be used for communication between the operator and the staff / services or other people on the spot. This intercom function can be expanded by public address information. It allows to react immediately to minor transgressions, without a need of involving the staff / services that should be reserved for more serious incidents.
IP CCTV system with alarm point and audio channel
Internet marketing / promotion
A video surveillance system based on IP technology can provide a very interesting marketing function. Such a system can be equipped with the camera/s that will be used only for presentation purposes - to post the video on a website. Generally, it should not be one of the regular CCTV cameras, but additional low-resolution device presenting a wider view of the place to be promoted. It will be posted as a small window on the website, to make it possible for the users to watch it even with older equipment or slow Internet connection. As the streaming server there can be used the recording server with such a function (often called sub-streaming).
Video presentation on the Internet
Hybrid systems
Implementations of IP CCTV systems also include effective cooperation with DVRs used in connection with analog cameras. The latest DVRs, employing H.264 compression, can provide IP video streams with very good parameters. Due to considerably lower prices of the analog subsystems, they are often used in IP systems called hybrid systems.
Modern hybrid system allows to connect such local CCTV installations to the IP core system. The DVRs are used as video servers that stream the video from analog cameras.

Analog installation as a part of IP CCTV system (hybrid solution)
System development
Analog CCTV systems are limited by the "magical numbers": 4, 8, or 16. So there is the problem when one needs to install the fifth, ninth or seventeenth camera... In the former two instances he can use a "higher-number" DVR, in the latter case - he will need another DVR, another cable between the DVR and the camera, and - also another CCTV monitor.
IP CCTV systems based on packet transmission and PC servers do not cause such problems. To extend such a system one has to:
  • mount the camera in the new location,
  • provide power supply,
  • connect the camera to any node of the IP CCTV network, having in mind network capacity,
  • adjust server parameters to the new total number of cameras,
  • if needed - upgrade software license (for the total number of cameras/channels).
Adding cameras to the system
Of course, at the planning stage of system development one can reserve adequate parameters of the network and server/s, so that it will be enough to perform the first three steps.
Mobile systems
Similarly to system developing, it is easy to reconstruct or extend IP CCTV systems on a temporary basis. It is needed e.g. in the case of occasional events that should be monitored to ensure public safety, for monitoring of construction sites etc. To fulfill safety requirements one can install for some time additional camera/s, or even client station. Of course the simplest and quickest implementation of the means is wireless link with the main monitoring system. The installation work consists in connecting power and running the link (antenna adjustment). A mobile client station (monitoring center) can be run even in a patrol car equipped with a mobile computer. To ensure smooth monitoring the network capacity has to allow additional traffic (both locally and in the system as a whole).
Mobile camera and monitoring center
Summary
Unlimited potential of IP CCTV systems includes new functions, not available in analog CCTV. Aside from video streaming there is possibility of voice and data transmission. IP technology allows to decentralize the system, both in the case of data recording and system control (client stations). The system can be easily developed or reconstructed and image quality can be adjusted to the actual needs.
Modern city IP video surveillance system
Due to flexibility of modern IP CCTV systems, the designing process and implementation should precisely fulfill the customer requirements, such as camera deployment (fixed and mobile cameras), image parameters (depending on the needs in every location), additional functionality (voice transmission, advanced control of the system etc).
 
 
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