Applying ‘best practice’ to the use of Rapid Deployable systems, now seen as a viable solution to limited budgets available for ‘full-time’ CCTV cameras appears straight forwards, but consideration must be given to the down-side of utilising 3G:
- An efficient compression method, i.e., H.264 or similar is a must, when controlling moving domes – the ‘latency’, as in the time it takes for the remote operator to see the dome move in response to his request for move must be minimal. Following or tracking a person, or vehicle needs very small latency. In reality this will never be as fast as a faster leased line, and use of presets is invariably the most effective method of ‘jumping’ to a known position – i.e., a driveway zoomed in an around number plates.
- Another reality is that the ‘cell’ the 3G is operating in can vary in its performance from time to time, dependant upon usage by others. This brings about another very important consideration when it comes to producing good evidential images or video – frame rate. The recommended method is to have ‘at-the-edge’ recording as well as stream the live video back to the operator. And the operator can download any of this evidence at will.
It is preferred to have the highest evidential quality, in terms of quality and frame rate – preferably a ‘D1’ (720×576 pixels) resolution and 25FPS (Frames per second) at a good quality. In H.264 terms this is proportional to the ‘speed’ as bits per seconds. This could be anything between 1Mb/s to 8Mb/s.
- Introducing Dual Stream:
Having a good quality image of this rate would be impractical over 3G, even a good HSPDA 384kb/s connection – so it is advised the system offers ‘Dual-Stream’:
- Stream 1, very high quality, stored locally to a hard drive, continuously (non video motion detected) for at least 31 days, recycling.
- Stream 2, a lesser quality, i.e., CIF resolution, 320×240 pixel at a frame rate of 6 – 12 FPS and a bit stream of anything from 50kb/s (would be very grainy) to 300kb/s. (Full cost)
Read Part 1:3G CCTV and Rapid Deployable Equipment