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What is CCTV?
CCTV (Closed-Circuit Television) is a system that allows you to record surveillance footage from security cameras to a recording device.
CCTV systems are used as a criminal deterrent and to monitor property, assets and staff. Systems will allow you to view both live and recorded footage – most modern systems will also allow you to view footage remotely from any device connected to the internet (laptop, smartphone, tablet).
A CCTV system can be as simple as a stand-alone single-camera device, or as complex as a centrally controlled hub which manages numerous cameras and combines security, automation and access control.
There are two types of CCTV:
- HD (high definition): HD CCTV uses IP (internet protocol) network cameras as the basis of the system, sending the image signal to an NVR (network video recorder).
- SD (standard definition): SD CCTV uses analog security cameras to record footage to a DVR (digital video recorder).
What is the difference between an analog and an IP system?
Both analog and IP (internet protocol) systems use cameras to record images onto a recording device.
In an analog system, this is a DVR (Digital Video Recorder), while in an IP system it is an NVR (Network Video Recorder). Both will record, playback and video footage which you can view remotely on another screen. All the same so far, right?
The differences come with the technologies being used – both how they’re set up and the actual camera system. An IP system is set up to operate from an IP (computer network), or one that is built for the CCTV system, while an analog system is set up independently from the computer network and will have its own cables and wiring.
But the biggest difference is how the camera lens sends the image to the recording device – and it’s ultimately the difference in how clear an image you will see.
In both technologies, the lens will send the image the camera sees (the signal) to a digital image sensor. In an analog system, however, the signal is converted to analog and sent to the DVR via copper wires, where it’s converted to digital, then compressed and recorded. (It starts out digital, is converted to analog, then converted back to digital.) This can mean a big loss of quality in the image – the very best analog CCTV cameras are limited to around 0.35 megapixels (see below for more about megapixels).
In an IP system, the camera itself will compress encode the signal, before sending it to NVR. The NVR then records or copies the video file from the camera – there’s no conversion back and forth, so there’s no loss in image quality. It runs on an existing IP (computer) network.
We tend to look at it as the difference between an old cellphone and a smartphone – analog is a bit outdated in the age of IP technology!
What do centralised and de-centralised mean?
A centralised CCTV is your more traditional system – the signals are sent back to a location where the DVR/NVR is connected, while a de-centralised system means the camera comes with the NVR functions on board. That means there’s no need for a central computer – the recorded video either happens on the camera itself or on a storage device attached to the IP network (such as a Network Attached Storage or NAS box).
What are pixels and why do they matter?
A pixel (picture element) is the smallest physical point of an image. Pixels describe the maximum size an image can be viewed at without a loss of image quality. (The bigger the number of megapixels, the more you can blow up an image.)
The reason pixels matter is simple: the more pixels an image has means it will capture greater detail and produce a bigger, higher quality image. Bigger images and greater detail means you can zoom in on certain images for clarity and identification.
The maximum resolution an analog camera will give you is 0.35 Mpx (megapixels) – pretty terrible when you realise that the camera on even the most basic smartphone will have 4 Mpx. By comparison, a basic IP camera starts at 1.3 Mpx – more than three times the resolution. (High end cameras will go up to 20 Mpx!)