Doktor Jons Guide to the "Use and Application of CCTV"
- This page is part of the "TRUSTED" CCTV Improvement Section -

- A Basic TRUSTED Assessment (2) -

How can you tell if your Video Surveillance System is 'TRUSTED'^©

Having looked at the general requirements for evaluating the CCTV cameras, we now have to consider the Monitoring & Display Systems, and the Recording equipment.

Monitoring and Display Equipment

In practice, the actual CCTV display system may have a number of additional pieces of equipment incorporated, such as a Video Switcher, a Picture in Picture (PIP) unit, a ‘Quad’ display unit, a Display Multiplexer that splits the screen up into lots of smaller images, and any one of these can variously affect the overall picture quality coming from the camera.

For the purposes of carrying out a basic evaluation, the following factors will need to be reviewed, and a qualitative judgement made of the actual performance:-

PICTURE QUALITY

This can be recorded on the TRUSTED check sheets, to take account of a whole range of factors including:-
The overall sharpness of the picture (resolution), Colour Reproduction, Brightness and Contrast, as well as more technical issues, such as picture Noise levels, Stability, Linearity (a bit heavy so we'll save that for later), and various Interference problems which can seriously degrade the image.

CAPTION DISPLAYS

It's quite common to have various bits of data displayed on the screen, including Time and Date displays (which must be accurate), a logo or caption information, all of which should be confined to a secondary portion of the screen, with small legible characters that do not overlay the key recognition area on the screen, and which do not in any way interefere with the overall quality of the display image.
 

Video Recording Equipment

The recording part of the system is probably the singular most technically complex piece of equipment in a CCTV system, but in a purely practical sense, it shouldn’t be too difficult to evaluate (although it might be well worth digging out the manufacturers Operating Manual for this bit of the exercise ... or maybe not!).

RECORDER TYPE

Firstly, we have to establish what type of recording system is in use? ...

... is it a conventional analogue VHS or S-VHS tape based machine, such as ...
... a basic “real time only” Video recorder?
... a continuously recording Time Lapse Video connected to a single or multiple cameras?
(using either a PIP, QUAD or Switcher unit, or perhaps a multi channel Recording Multiplexer)?
... a Time Lapse Video that only records when triggered by a movement sensor?
... or is it a tape or Hard Disc Drive (HDD) based 'Digital' machine (DVR), such as ...
... a basic “real time only” DVD removable disc recorder?
... a constant record Digital Video Recorder (DVR) either single or multiple input?
... a constant record Digital video server connected to a computer network (NVR)?
... a constant record PC based Video recording package (either 'dedicated' or 'shared')?
... a DVR or PC based systems that only records when triggered by a movement sensor?

RECORDING SPEED

Does your system record in “Real Time” (25ips) showing normal speed movement on playback?
If it's an analogue Time Lapse Video what record speed is normally used ...?
If a DVR, how many images per second is it recording for each connected camera?
If an NVR, typically how many images per second is it recording for each connected camera?

RECORDING / PLAYBACK QUALITY

For tape based recorders, it is important to gauge a number of factors that could affect overall picture quality, including dropout, playback stability, interference or lines in the picture, image break up etc.
With a digital DVR or NVR playback stability, compression, resolution settings, and noise, can all seriously affect the playback.

RECORDING CAPACITY

With tape or DVD based recording media, real time will only allow a maximum of perhaps four hours at normal speed, although Time Lapse machines can be set to record for longer periods on a single tape. A digital DVR or NVR will be limited by the size of the hard disc arrays; this will need to be evaluated on an individual basis.

RECORDING EXPORT

How does the operator save the video recordings:-
Remove and store individual video cassettes (if so, for how long ... 7 - 14 - 21 - 30/31 days)?
Are specific clips copied to CD / DVD / USB recording devices?
Can the entire contents or significant chunks of a hard disc be backed up to external media?
Is it possible to easily remove and store a hard disc, and replace it with another HDD?
Is material copied in part or in its entirety, to a remote network server (NVR)
It's also important to consider how easy it is to export essential video recordings, and take account of the number of persons on site capable of making copies when required.

Further information on the "TRUSTED" Basic CCTV assessment >>

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