ÐÇ¿Õ´«Ã½

What our experts say...
Disk-based digital video recording for CCTV applications is very much a hot current issue. What we would all really like is a disk-based system that is capable of recording broadcast quality images from a few hundred cameras in real time, having an archive capability of at least 31 days, multiple format outputs to suit the requirements of police or other interested authority and at a cost that is no greater than an equivalent S-VHS based system.

Is this just a dream? Not entirely. Such a system spec is possible today with just one exception – the cost! And yet we are seeing the capacity of hard disk drives increase almost monthly while their cost continues to fall. So hopefully one day our dream will come true.

But in the meantime we have to be realistic. The cost of upgrading a large tape-based system to hard disk is still considerable, even if we only wish it to equal the performance of tape (with the given advantages of no tape management issues and a much improved search facility). However many of the CCTV installations in the UK (and abroad) are small scale, unattended systems requiring only a single VCR, and here at least we are now able to appreciate the advantages offered by digital technology.

All too often the timelapse VCR in smaller systems tends to be forgotten about by its owner until it is needed. Yes, the installing engineer will have told the owner of the need to rotate and replace tapes, but this is frequently overlooked within a very short space of time. What is needed for such systems is a reliable maintenance-free recorder offering reasonable picture update rates and recording quality. For this market, at least, we now have a range of affordable disk-based solutions, of which the D4 from Dedicated Micros is a good example.

The D4, like many of its contemporaries, is much more than just a digital video recorder. It also incorporates a four-channel digital multiplexer offering a range of display options and features such as zoom, activity detection, and OSD variations. The unit is designed with flexibility and expansion (within reason) in mind. Flexibility comes in the form of a number of external connection facilities including:

• Connection to a 10-base-T Ethernet network enabling control of the unit from a remote location. Using either Microsoft Internet Explorer or the in-built Network Viewing Software (downloadable from the D4) it is possible to view either live or recorded images
  
• An RS232 port which enables remote viewing via a dial-up modem.
  
• Five alarm inputs (one per camera input + global) with optional input polarity selection.
  
• Separate relay outputs responding to alarm input activation, activity detection and camera fail.

Expansion options come in the form of:

• A SCSI 2 port enabling extra CDR storage devices to be added.
  
• An RS485 port to enable the D4 to be connected directly to other DM compatible devices that use this protocol.

Other features include simultaneous live viewing, recording and playback, a friendly user interface with VCR-style function buttons, optional audio recording (mic or line input levels) on input 1, a schedule option to enable variable record rates at different times of the day, automatic copying of alarm events to a device connected to the SCSI port, password protection and infra-red remote control.

The power supply is external to the main unit and takes the form of a switch mode unit. This is well constructed and runs cool, although care should be taken to ensure that the vent for the small cooling fan is not obstructed as there is no other provision for ventilation and convection cooling within the case.

Installation and programming of the D4 is not difficult. The factory defaults have been set to enable a 'plug & play' approach for a basic four-camera installation having no network connections. As long as you ensure that all cameras are active at start-up, the D4 will automatically detect the inputs in use and set the display and recording sequences accordingly. Where programming is required, a simple to follow menu structure enables the installer to set up a unit with relative ease.

For the less initiated, the accompanying manual contains a step-by-step guide to the menus, interspersed with some fundamental training information. Programming is possible using either the front panel controls or the infra-red remote control unit. Perhaps one criticism is the size of the on-screen text. We looked at this on both a 14-inch and a nine-inch monitor. Where a larger screen is used the text is reasonably visible. However if you had to work with a small screen size you may struggle.

As with any on-screen menu, the text can be further obliterated by the picture information behind. A practical tip where this is a problem: select an input and place the lens cap over that camera to produce a black screen. Don't disconnect the camera as the auto input detection facility in the D4 will assume that the input is not in use and set-up may be impaired.

The unit has provision for assigning a title of up to 12-characters to each of the cameras. Apart from the 26 alphabetic characters, there is also available the digits 0 to 9 plus a wide range of other characters and symbols. Considering that character input is done by incrementing through the list rather than via a keypad, inputting is quite fast. However it is a shame that each time you move to a new character, the default is zero rather than A, which means you have to either scroll through all the digits and symbols or go backwards through the alphabet.

The activity detection set-up method is pretty much standard, using an array of spots on the screen which can be de-selected to disable parts of the image area. The sensitivity adjustments proved effective on our tests, with the walk test facility greatly simplifying verification. The only limitation is that it is not possible to vary the sensitivity for different areas of the image.

For each camera input, the menu provides for individual setting up of input termination, colour/monochrome camera, alarm input polarity and signal loss alarm. It is worth bearing in mind that input termination is not automatic but is set from the camera set-up menu. Although this is made clear in the installer manual, it is not mentioned if you only use the quick start guide – a point which could catch out the installer who is used to equipment having auto termination detection. Similarly, if monochrome cameras are being employed you would need to move the input setting from the default 'colour' position, otherwise colour 'noise' will be evident on any colour monitors.

In addition to these settings there is also a contrast and colour adjustment (colour is disabled when 'mono' camera is selected) for each camera. These are a useful tool, however installers should ensure that the camera itself has been set up for optimum performance before attempting to correct image problems using these controls. Also note that adjustment of these affects the recorded picture, but not the loop out signal.

Where network connections are required, the manual contains step-by-step instructions on how these may be established. However if you have never been involved in networking it would be advisable to work with someone who has experience in this field; there are many variables with network technology which would be very difficult to cover in any installation manual. But it is helpful to know that the technical support desk at Dedicated Micros is available to talk you through the awkward problems.

At the time of writing, the D4 is available with either a 40GB (Gigabyte), 80GB, or 160GB hard disk drive. We tested a 160GB version. If the settings are left at their default recording interval of three pictures per second (3PPS) and file size of 18kB (which is said to offer similar performance to that of S-VHS), then a recording period of around 34 days will be achieved. Our tests showed that increasing the file size to 25kB reduced the recording period to 24 days, however subjective viewing of these images revealed only a moderate improvement over the 18kB performance. Therefore, for most situations the 34-day archive period would probably be preferable to having a marginal improvement in picture resolution.

Even at 18kB some MPEG artefacts were discernible on certain areas of (high resolution) picture information, these artefacts being manifest as the now familiar 'block' effect which occurs when fine picture detail is effectively thrown out in the MPEG signal compression process. This effect became more noticeable when the file size was reduced to around 14kB (approximately VHS performance), but nevertheless a useful image could still be obtained, and the recording period was extended to 43 days.

Below 14kB the block effect becomes so great that most images become unusable for anything other than verification of the presence of objects or persons. In terms of output options, in addition to the SCSI output for CDR connection the D4 offers two composite video outputs; a main monitor and a spot monitor. Perhaps it is a shame that there is no S-VHS output connector to provide for situations where the user still wishes to download onto S-VHS for either archiving or evidential purposes.

The D4 can be password protected, although there are no separate user and installer menu options and therefore giving the user the password will allow him access to all settings. Unfortunately, withholding the password prevents him from accessing low level adjustments such as time, date format and daylight saving time.

The unit itself is of a robust construction and comprises a single PCB, a hard disk drive, a front control panel and a small cooling fan. The front controls (all push buttons) appear to be sound enough to withstand the wear and tear of industrial use. The rear connectors are not board mounted but rather are fixed to the rear metal chassis which is a much sturdier form of construction; board mounted connectors are prone to having dry joints form. The D4 does not produce a lot of heat and the small cooling fan provides sufficient airflow to keep the unit cool without excessive noise.

A simple user guide comprising a single card provides the user with the necessary information to operate the unit. The installer manual is generally well written and follows a logical sequence, however we did discover a couple of errors, which could cause confusion whilst setting the unit up. These errors were checked with the technical support desk at DM who told us the information would be fed back. As usual, the technical support people were extremely helpful.

What the manufacturer says ...
The new D4 is a cost-effective entry level four-channel digital multiplex recorder that combines video multiplexing, digital video recording, remote viewing and audio recording in a single easy to use and install package.

The D4 has a price and feature set that now makes digital technology accessible to small business applications where a dedicated CCTV system is required.

Designed to have the look and feel of a traditional CCTV system, D4 offers familiar multiplexer and VCR style control keys, and combines all the benefits of digital with the features you would expect from a traditional multiplexer including main and spot monitor, hidden cameras and built-in activity detection.

The D4 provides up to one month's on-board high quality, digitally signed recording. Images can be accessed by the user at the simple touch of one button, or via powerful GOTO and event preview facilities. Digitally signed events can also be copied to external CD-R. Supplied free with every D4, the new IR remote provides the user with front panel control of the unit for operator ease of use.

The D4 supports two remote viewing options – PPP and Ethernet – using the Dedicated Micros free network viewer software or via a standard Internet browser.

Where there is no PC network available the user is still able to dial in and view images on the unit at any time with the use of a standard modem and telephone line.

In networked applications D4 uses a standard Ethernet connection to provide remote viewing capabilities either on a LAN, WAN or the Internet.

D4's remote network support provides password-protected access to the menu system on the unit. System adjustments can then be made remotely – in many cases eliminating the need for a site visit.