Designing a IP CCTV System - Network Requirements
Manufacturers of IP Video equipment provide excellent tools for helping security and IT professionals design digital CCTV systems and in particular compute the bandwidth requirements of the network. It’s fundamentally a very simple process; decide how many cameras are required, decide what video quality for viewing and recording is required and decide how many days of recording are needed. These can then be used to calculate how much bandwidth and recording storage is required.
Each device connected to the network is then assigned an IP address, ensuring they are all on the same sub-net and can therefore ‘see’ each other. The ‘Site Builder’ software tools provided then interrogate the network and discover all the appropriate devices and automatically build a site database and recording schedule.
In many cases the bandwidth requirements can be easily accommodated on the existing corporate LAN/WAN, giving the proposed IP Video system another significant advantage over analog CCTV by removing the need for additional cabling. This also means the network can be shared with the normal IT traffic and facilities such as Voice-over-IP. IP Video has many clever features which ensure that the bandwidth impact is kept to a minimum. Positioning NVRs locally to relevant camera clusters can reduce network traffic and improve redundancy. The compressed video can be transmitted across the network using TCP, UDP Unicast or UDP Multicast protocols. The advantage of Multicast is that it uses the same amount of network traffic for 1000 operators to view a camera as it would for one operator.
Activity Controlled Framerate (ACF is another feature designed to reduce network traffic. This facility relies on processing data at the camera IP transmitter/receiver unit. If no movement is detected in the camera scene then the bandwidth used is dramatically reduced. This feature is most effective in places where low activity occurs, such as in corridors, on fire escapes, or in buildings which are unoccupied at night. Searching recorded video can be a time-consuming activity with a corresponding increase in network traffic. However, clever thumbnail search facilities can be provided by the video and alarm management The typical NVR solution simply requires a PC platform and hard disk storage. However, for more demanding fault tolerant applications NVRs can be packaged in stand-alone units with removable hard disk drives. Transmitter/receiver modules transmit MPEG-4 quality digital video, audio and control data over the IP Network. Software. The system can analyse movement in a scene and display thumbnail images that represent frames from recordings containing the specified movement. Clicking on one of the thumbnails then replays that section of video. This feature can search 24 hours of recorded video and display the thumbnails in just a few seconds. Changing the search variables allows the operator to sift through vast quantities of recorded material quickly and efficiently. The use of thumbnails allows a vast amount of video to be analysed with little extra impact on the network.
Don’t Throw Out the Old Cameras – Handling Legacy Systems:
It is clear to see the advantages of IP Video for large enterprise systems, with its underlying flexibility and scalability. However, it is also an ideal solution for smaller CCTV systems and in particular for upgrades to existing installations. When upgrading from an existing analog system the obsolete equipment such as the matrix and DVRs can be replaced, but all the cameras, domes, monitors and keyboards can be kept. Using IP transmitter/receiver units, all existing cameras and monitors can be interconnected; in fact existing control room configurations can largely remain unchanged. With the addition of a PC or two, all the advanced features of IP CCTV can be made available without the need to change the familiar surroundings of the control room. Once the migration is complete it’s very easy to expand the system in the future. It is now becoming common practice for IP Video systems to be used to expand existing analog CCTV systems based on cost alone – it’s often just too costly to cable in new cameras from remote locations.
Transmitter/receiver modules transmitMPEG-4 quality digital video, audio and control data over the IP network the typical NVR solution simply requiresa PC platform and hard disk storage. However, for more demanding fault tolerant applications NVRs can be packaged in stand-alone units with removable hard disk drives IP Video allows potential end users to easily trial the system at first-hand without commitment to large scale change from day one. Even though IP Video is an established technology, users will always want to convert to new technology at their own pace.
The integration with intruder alarm and access control systems is also providing advantages as they are now moving to IP networks as well. These systems are also seeing the benefits and flexibility of replacing cable with a network. The CCTV video and data from these systems can share the network without any problems, in fact this level of integration provides some interesting features. For example, a security alarm can provide an input to the IP Video system, which automatically moves a camera to cover the incident and displays the video feed on a monitor in the control room together with a map of the location providing multiple perspectives on the incident. Digital Video Recording – the NVR is important to differentiate between Digital Video Recorders and network Video recorders (NVRs), as both are often termed ‘digital’. A DVR digitally compresses analog video feeds and stores them on a hard-drive, the term ‘digital’ referring to the compression and storage technology, not the transmitted video images. The DVR therefore has to be located near the analog feeds. In contrast an NVR stores digital images directly from the IP Network.
Therefore the most obvious difference between the DVR and NVR is that the DVR records analog streams from analog cameras, whereas the NVR records video streams that have already been encoded at the cameras. Thus you find no video connectors anywhere on a NVR; its inputs and outputs are IP data, comprising of compressed and encoded video. NVRs can be either PC software based or dedicated stand-alone units.
The huge advantage of an architecture based on NVRs is that they can be located anywhere on a network – at the monitoring centre, adjacent to camera clusters, on the edge of a network or collected together in a hardened environment. In use their location is transparent to an operator; the recorded video stream from any camera can be viewed by any operator at any point on the network. NVRs record and replay simultaneously and recordings on any one machine can be remotely viewed by a number of authorised operators spread across the network simultaneously, all totally independently and without affecting each other. The independence of physical location is an important factor. By calculating the required network traffic and strategically placing NVRs accordingly, the impact of video streaming on bandwidth usage can be minimised. Typically an NVR might be placed near (in network terms, not necessarily physically) a camera cluster so that the load is carried by the local LAN capable of absorbing it easily, thus saving capacity on other, perhaps more restricted, parts of the network.
“Mirroring” techniques are now often used to duplicate the recording of video streams on additional NVRs located at different parts of the network, which provides a high level of protection against network failure; if one part goes down the other is there as a backup. You can have as many NVRs across a system as you like - there is no requirement for additional video cabling. Evidence from the NVR can be exported in the standard MPEG-4 format allowing it to be viewed by any 3rd party viewer such as QuickTime for Windows Media Player. However, the exported video includes encryption and watermarking to allow extremely secure detection of tampering such as frame removal, reordering or modification.
Advanced Analytics – The Future Analytics is the processing of video images to detect such events as congestion, stolen objects, cars parked too long outside a building, people moving the wrong way through security checkpoints, etc. Analytics are available as an add-on to analog systems which makes it difficult to realise the true benefits of this technology. In IP systems however, analytics can be completely integrated so their full benefits can be realised. IP-based analytics can be run in two modes: real time within the IP transmitter/receiver at the camera, and post-processing, on any operator’s PC. The real time mode allows the system to automatically identify events as they occur. Post processing allows operators to run many different scenarios on recorded video, e.g. look for cars parked for more than 2 minutes. These two modes offer the best of both worlds, using analytics to identify events as they occur, and also providing advanced search tools for operators to analyse previous situations. Human operators are particularly poor at watching video monitors for long periods of time, but are generally very good at confirming whether something is an incident or not, once it has been flagged automatically by the system.
Many of the latest developments in IP Video are centered on these types of features; here are just some of the analytics algorithms that are appearing on the market:
1. Congestion Detection - too many people in too small a space
2. Motion Detection - person or vehicle moving, say, from left to right across a scene
3. Abandoned Object Detection - suitcase abandoned in an airport terminal
4. Counter Flow - person moving against an immigration route
5. Virtual Tripwire - detection and alarm upon breach of a defined line
6. Shape-Based Detection – e.g. vehicle detection
7. Object Tracking and Theft Detection - object removed from a busy scene
Advanced analytics is one of the outstanding applications of IP Video that simply cannot be matched by traditional analog CCTV systems and offers so many advantages that this feature alone can often justify the IP solution. It can be expected that huge productivity improvements will result from using analytics software during the searching of recorded material in post-event analysis - and for this, the NVR is the key.
Sources:
http://www.gobeyondsecurity.com/forum/topics/designing-the-ip-cctv-system
http://www.gobeyondsecurity.com/forum/topics/what-is-a-dvr-what-is-a-nvr
