CCTV 4 channel DVR card

[ian.cant]

Your current set up is no use as evidence as far as i am aware as it has no time and date on the recording.

[Guest deefadog]

You mean the police will not act because there is no time and date, even if you can clearlly see the person doing a crime?

And what about the quality comparisom between a standard vcr and QCIF, CIF, 2CIF, DCIF,4CIF?

Thanks

[ian.cant]

You mean the police will not act because there is no time and date, even if you can clearlly see the person doing a crime?

And what about the quality comparisom between a standard vcr and QCIF, CIF, 2CIF, DCIF,4CIF?

Thanks

Well I would hope they would act on the recorded eveidence but they couldnt use it in court was what i meant.

As for Lee's abreviations, i have no idea either.

[Guest deefadog]

Thanks mate, just goes to show you can hand a criminal on a plate but because of the rediculous laws they can't be convicted! got to love our country!

[Rich]

CIF is common intermediate format, The pixel equivelent to a PAL video signal, NTSC are differnt.

QCIF / quarter common intermediate format = 176x144

CIF = 352x288

2CIF = 704 x 288

DCIF = 528 x 384

4CIF = 704 x 576

CIF would be the closest resolution to a domestic vcr recording I guess.

4 CIF is the PAL quality, or comparable to DVD quality.

http://en.wikipedia.org/wiki/Common_Intermediate_Format

[Guest deefadog]

Thanks Rich

The recoding resolution on the r200 machine is 720X240? so i am confused even more

so - 720 = number of pixels per line.

240 = the number of lines

So i guess i only need a camera with 240 tv lines as anything higher is not going to count?

Is there a link anywhere with an example of that image? or can it be recreated/simulated in photoshop?

Also another model i have been looking at is 640 X 272, now this has lower pixels per line but higher number of lines! whcih one would be better quality in you opinion.

Sorry for the questions btw

[Rich]

Thanks Rich

The recoding resolution on the r200 machine is 720X240? so i am confused even more

so - 720 = number of pixels per line.

240 = the number of lines

So i guess i only need a camera with 240 tv lines as anything higher is not going to count?

Is there a link anywhere with an example of that image? or can it be recreated/simulated in photoshop?

Also another model i have been looking at is 640 X 272, now this has lower pixels per line but higher number of lines! whcih one would be better quality in you opinion.

Sorry for the questions btw

Im not completely sure, but I think 2CIF doubles the horizontal line information, so would duplicate each field to make a frame. This would ensure the correct aspect ratio of the PAL signal. 4:3

[Rich]

I think you will find they will be pretty similar, it sounds like a DivX codec though.

Dont confuse TVL with the number of horizontal lines, TVL is the comparison to pixels per horizontal line(possible definable information per horizontal line).

A PAL frame is always 625 horizontal lines from the top to bottom of the picture, a field is half that 312.5 lines hence 2 fields make 1 frame.

DVR's are being described as fields per second or frames per second.

I cant say what would be the best quality without comparing the 2 side by side.

[Guest Rockford]

...Sounds to me like Mr. Tracey and I are of similar mind! I work in IT / IP and digital video. We deal with some police and their requirements are generally very specific.

I've even heard of a police force ONLY accepting CCTV evidence if its in MJPEG / JPEG still format since they consider everything else to be a WoT...

...you certainly make a lot of very interesting posts Mr. Tracey. Admitedly, I've understandibly not properly read them all in their entirety, but I am inclined to agree with your perspective on the state of CCTV today!

This I think has been the most enjoyable topic I've so far read on this forum! Nice to have access to so many smart people with such experiences that compliment and make up for any holes my own

Have nice weekend people!

[Doktor Jon]

Evening chaps,

I'm a bit cream crackered tonight, so my apologies in advance for not getting too technical in this posting.

First off, the issue of video recorded evidence admissability without time and date generation is in parts actually a bit of a grey area. As domestic CCTV is excluded from the Data Protection Act, there is no obvious implied legal compulsion on TDG being applied to domestic recordings. Desirable ... certainly, vital .... not necessarily.

My understanding is where it is a pre requisite for DPA compliant commercial systems (and remember, recent legal interpretations suggest that not every commercial systems is actually required to comply with the DPA), then accurate TDG is necessary, with the correct information being displayed.

Whilst incorrect or absent captions would provide significant difficulties on legal submission (particularly incorrect captions which are classified as corrupted data for the purposes of the DPA), it would ultimately be up to the judge on the day to decide whether the strength of the recorded material alone, could be accepted as trial evidence.

On the issue of image and recorded resolutions, this is also not necessarily as straightforward as looking at a simple engineering comparison.

Let me give you a couple of very simple examples:-

Take a ten year old black and white CCD camera with 280 lines resolution, fit it with a 4x telephoto lens, point it along a corridor and record the image on a standard VHS recorder (240 lines colour). If a target adult male is captured 10 metres away from the camera, the subjects head will occupy approx. 30% of the picture height - more than enough for a clear and identifiable evidential quality recording.

Now, if you take a "state of the art"(?) 540 line resolution colour camera, fit it with a wide angle lens, record it onto a 520 lines resolution digital recorder, again capture your average joe at 10 metres distance from the camera, the subjects head will probably only occupy about 3 > 4% of the picture height - almost certainly not enough to provide a conclusive identification.

Whilst the quality capabilities of the equipment are vital, the configuration of the system is paramount, if it is to provide the desired results.

My simplistic advice is often to source the best quality of equipment available within a budget, but not to assume that the quality issue is the only relevant solution.