View Full Version : CCTV Technology

6th Aug 2001, 21:29
Damn poor, given today's technological (computer) standards. Ealing bombers, Oz perp, Bulger killers, shop recording. Given the photograhic standards expected today, perfect on speed cameras, but apparently horrible on everything else?? Or is the poor stuff only what is released to the public?

tony draper
6th Aug 2001, 21:52
Have to declare a interest here Draper earns his living installing and maintaining these systems.
Most city center type camera's because of the shear number of them, are recorded on time lapse Vcr's thru a piece of kit called a digital multi plexer, ths enables up to 16 camera's to be recorded similtaniously onto one standard 180 cassette, these vcr, are generaly set to record these camera's for 24 hrs, then the tape is changed, and kept for a fixed period, tapes are never re used, or should I say they are not supposed to be re used, only one pass over recording heads is the rule.
It is possible to call up display and record individual camera's,on a separate VCR in three hour mode, this gives a much better quality recording, this is fine if the camera is covering some area where it is likely that something will happen in front of it, ie covering the outside of pubs clubs at throwing out time,
It is possible to take a number of digitised frames from any of the hundreds of camera's that are recorded, and to a certain extent clean them up.
The systems you see in banks and building societies on the whole far superior as with less numbers of camera's being recorded, the better the quality of the of the output.
These scratchy black and white stuff you see tend to come from older systems in corner shops where they have been sticking the same tape back in the machine for months on end and the kit is never serviced.
Modern hi resolution colour security camera's are incredibly good, up to broadcast quality now, its the recording method that limits the quality.
OOps mebbee I shouldn't have told you lot this.

6th Aug 2001, 22:27
Hey, Draper, you & me also!

I live in another part of the world, and I'm constantly trying to explain to people why you DON'T need "broadcast quality" for security cameras. The recent footage of the "school shooting" in USA shows that; the camera was being recorded at about 1 frame per second ("broadcast is 25 or 30 frames) but the essence of "what went down" was still there.

Recording many cameras (like in a city centre) in high frame rates, needs a lot of hardware, and I often show people a video of a guy approaching a security fence, climbing over it, and running towards a "target" - recorded at 1 frame per second - and ask "now what did you miss?"

These days, instead of VCRs, we have the option of computer hard disks in "Digital Video Recorders", which can record up to 16 cameras for a long time, with none of the problems of "over-used worn tapes", and we can get 15 frames per second if we want, but 1 or 2 frames per second still provide evidence of what happened, and give us a much longer history of recorded data. If anyone wants the figures, check out www.telexiscorp.com and try out the "time stored calculator" ("Robot/Sensormatic" have a similar product, as have many others - but I'm a "Telexis" agent!)

You DON'T need "broadcast quality" for security applications - only if you want to sell the gruesome video to the tabloids - or their TV equivalent!

(if you want to talk "cockpit cameras", I would suggest about 3 frames/second, at the risk of alienating some of my "driver" friends, as things can happen a lot faster "up front" in emergencies - again, "full broadcast quality" would only be needed for the bloodthirsty sensationalists)

tony draper
6th Aug 2001, 22:45
Roger that Mr G, Stuff we install in banks and such are connected to the raid system and switch the VCR'S TO 3Hr mode should any scullduggary occur.
Got a magic system on my house, with a FORA motion detection rack I know its old technology but if anybody walks up to my car they are nabbed on tape got two Mitsubishi hires colour camera's front and back, about 700 line I think , full ptz on the front one, Scallywags spar well clear of Drapers dwelling.

6th Aug 2001, 22:53
TD: if your photos are as sharp as your spelling you will never catch anyone.

I am only a special constable in the spelling police, but enough is enough, surely.

tony draper
6th Aug 2001, 23:55
Beware Mr J, Draper is a dangerous man to provoke,he will secrete camera's around your bailywick, and nab you cold ;)
I am deeply hurt, I thought my spelling had improved greatly since I started to lurk here and was deprived of the spellchecker supplied on most sites and had to relearn the art.

7th Aug 2001, 22:32
**** me mate...!!! What kind of car do you drive..??????????? :eek:

8th Aug 2001, 00:23
Isn't half the fun of PPRuNE being allowed to spell badly, and seeing if people can decipher it?


tony draper
8th Aug 2001, 01:40
Well Mr L, you probably get free travel, Draper gets free camera's, perk of the job. ;)