Jon's Top 5: IP system design

09 Nov 09

By Jon Hill

Are you designing an IP CCTV system? What are the main points to bear in mind? In his regular column, Jon Hill of Mirasys UK gives his top five tips on IP system design...

1. Centralised Recording Solutions

As we transition from analogue to network based recording, it is common to adopt the familiar 'centralised' approach. In many cases, a dedicated security network is installed along with IP cameras and POE switchgear to simplify power distribution.

A key difference between NVR solutions and a standard DVR is the need to factor in graphics processing, to allow system monitoring. NVR solutions tend to adopt the true client/server approach where remote workstations are used for display purposes.

This frees up more processing power for recording purposes. The alternative to a dedicated network is to stream video data over a shared network, using for example a VPN. This approach has proven problematic in many cases due to bandwidth requirements.

2. Distributed Recording Solutions

Taking a distributed approach to network recording seems like a more logical option in some cases and is particularly well suited to a shared network scenario. Dual NIC recorders are strategically positioned as recording 'nodes', collecting streams from a small number of local cameras.

Workstations are then used to integrate each recording node (or several nodes) as required. Recorded and/or live material is thus streamed from a second NIC at the recorder that is connected to either a shared or dedicated network.

This is more efficient in terms of network resource and more secure than a centralised solution. The downside is housing the remote recording devices and any switchgear.

3. Hybrid Combinations

One of the most common requirements within the UK security market is to amalgamate legacy analogue solutions with new IP systems. Increasingly, megapixel cameras are being added to existing CCTV systems in problem areas, with clients often expressing reluctance to replace existing hardware.

With a desire to make the most of any existing camera hardware and minimise upgrade costs, it's important to look for a solution that will seamlessly integrate both technologies.

4. PTZ over IP

The Achilles Heel of most Network-based solutions is latency. No matter how you dress it up, latency is part and parcel of almost any system that incorporates a network.

Varying degrees of latency are seen with most IP based CCTV solutions, but the use of PTZ heads exposes this issue all too clearly. The question is, can this be eradicated with greater attention to detail at the design stage?

Much of the latency can be avoided by correctly calculating the required bandwidth and using the most efficient network protocols, such as RTP (Real-time Transport Protocol) and implementing QoS. Use managed switches in larger systems.

5. IP Monitor Walls

In spite of our ability to transmit video signals, there is still a need for live monitoring using a collection of camera views on a number of display monitors.

Existing analogue systems are either wired through video amplification to static monitor walls or fed through large video matrix switchers. We are all familiar with dual graphics cards where the windows desktop is stretched to cover both screens. For smaller systems, this concept can be extended using either graphics cards or USB devices.

The windows desktop is either cloned or stretched to cover all of the monitors, and the preferred display configured. This may use 'internal' processing that is not limitless and needs careful design.

A more robust method is an external graphics processor connected to either a large LCD screen or video cubes. The result is a very open and flexible wall, highly configured either independently or from within the recording device.