Can we help?

Q: I have recently completed a major digital CCTV installation in a large block of flats situated in what police describe as a “troubled” area, to help combat local neighbourhood crime. Within the first week it captured a violent attack perpetrated by local youths.

The police have viewed the evidence end have asked me to hand over the digital recorder to them for identification purposes. However if I do this, the local authority will be left without any CCTV coverage.

What are my options for taking the images off the machine that provides the police with the evidential quality they need?

A: I think there are really two questions here: firstly what media is available for you to archive the images to, and secondly, what qualifies a digital image as being of evidential quality? Both are important areas and deserve substantial coverage.

I’ll start by giving you an overview of the various archiving options and will come back to the second question of digital images as evidence next time in the Can We Help? series.

Unfortunately, if your chosen DVR does not incorporate some sort of removable image archive facility, It leaves the end-user open to their DVR being confiscated by the police, particularly if you’ve captured images of a serious incident.

Many manufacturers offer built-in archive facilities and some offer the opportunity to extend your system capabilities by attaching a CD-burner etc. I’ll run through the various options here.

So what media can you archive to?

‘Hot-swappable’ disks
A system based on hot-swappable hard disks removes the need to archive to an external medium. Two integrated RAID1 storage hard disks (redundant array of independent disks) create two identical copies of all recorded data within the unit which means that one disk can be removed directly from the digital video recorder while recording continues entirely unaffected. Furthermore, users can continue using the system as normal during disk removal – and a failsafe backup is always in place if one disk fails.

The images from the hot-swapped disk may be reviewed on a PC which, depending on your model of PC, will require you to purchase a USB (universal serial bus) connected caddie-station. Alternatively, some newer PC’s have a hard disk caddie station built in. In conjunction with PC playback software, which should be provided by the DVR manufacturer, the archived disk may be reviewed easily from any location.

By using this type of system it is possible to remove up to six months of recorded data off site in an instant – without having to power down or interrupt viewing or recording in any way.

This represents an ideal storage solution for customers who want to archive very large amounts of digital video footage (such as town centre systems) and those who need to transfer data to the police quickly for evidential purposes.

Critical data can be made available instantly and in its entirety to the police or a law enforce-ment agency for analysis with no system disrup-tion or loss of performance. Sensitive data can be rapidly taken off a high -risk site, such as a prison of police custody suite, for safe storage or review.

CD-R
Some digital recorders have built in CD-ROM writers that can copy the images straight onto a CD. This copies the required images plus the digital watermark. If the digital recorder does not have a built in CD-ROM, it may be possible to purchase an external CD-ROM and connect it, normally via the SCSII port.

If your end user's DVR does not have some sort of removable image archive facility it is open to being confiscated by the police

CDs can be used to copy specific time frames of video, so that they can be viewed elsewhere. They are not really suitable for any kind of archiving or long-term storage .

The setup of the digital recorder, ie the time lapse mode and the picture quality, will determine exactly how much video can be stored on the CD. Some digital recorders will copy the images and playback software on to the CD, so that no extra software will need to be installed at the destination PC, making things nice and simple!

DVD
DVD burners have the advantage that they are able to store at least ten times more data than a CD. However, as yet, there is no standard recording format. DVD writers are quite expensive in comparison to CD-ROM burners but, as with most computer peripherals, the price will eventually decrease.

On the other hand, if you have a DVD burner connected to your PC, it may be possible to export the images over to your PC, then copy the images on to DVD using your PC, still copying over the digital signatures.

DDS tapes
Digital tapes are the most expensive and “tricky” way of copying information.

Each tape can cost up to £70, and you will require a DDS drive at the location where you wish to view the information. DDS drives can cost up to £800 and the tapes need to be replaced every 12 cycles.

A potential hazard also arises in that, because the tape is so small and fragile, extreme care must be taken and the tapes must be stored in the correct environment so the tape itself does not snap or become damaged. This solution is similar to a time-lapse VHS recorder.

Export over the network
One archive method worthy of a mention is the export of images over a shared network - either local or wide area.

Once viewing images on a PC via the manu-facturer’s network viewing software, you may save the images as industry standard JPEG or AVI files and download from any PC (presuming it has suitable archive media such as built in CD-burner) connected to that network.

Compact flash
Finally a glimpse of the future ... you will start to see manufacturers introducing integral compact flash cards to their DVR units. You may be familiar with the technology if you have a digital camera. In much the same way as an external caddie station, you’ll be able to connect the DVR to the PC usually via the USB port, enabling you to download and view sequences of images using the manufacturer’s PC playback software.

* If any readers have any CCTV questions they’d like to put to me, please email them to ahyder@cmpinformation.com who will pass them on. I’ll endeavour to answer all you questions as soon as possible. The best questions will be printed and the reader will receive a DM goody bag, so keep them coming in!

* Ian Barker brings a strong IT background to his role with Dedicated Micros’ technical support department, having spent eleven years in a wide range of IT support roles.