The bench test 2: Big is beautiful

We have grown accustomed to video recording devices getting smaller and lighter, so the Mitsubishi DX-TL5000 16-channel digital video recorder comes as something of a revelation. It is huge, tipping the scales at a hefty 13.5kg and measuring 425 x 390 x 185mm, which is between two and three times the size of many rival DVRs. This must be some kind of record.

At first glance there appears to be no good reason for its considerable bulk. Many key internal components are standard off the shelf PC parts and together they occupy no more than a third of the available volume. They're not exactly packed close together either, but Mitsubishi are clearly taking no chances. The case is hewn from heavy gauge steel and apparently designed by the same people that make aircraft black box flight recorders, so even if the building it is used in collapses around it there is a better than average chance that it will survive to tell the tale.

In fact there is a more down to earth reason for its size and it can be summed up in just one word: cooling. DVRs get warm, worryingly so in some cases, and this can have implications for reliability and life expectancy. The TL5000 should avoid any such problems; the case and power supplies are very well ventilated and the oversize housing means that there is plenty of room for air to circulate, so the temperature inside the case never rises much above ambient levels.

As befits its size the TL5000 has an extensive range of features. It begins with a 16-channel triplex recording system with dual multiplexed monitor outputs, capable of simultaneous recording, playback and live display (on two monitor screens if required). There is a choice of five screen display modes showing single, 4, 9, 10, 11, 13 or all 16 cameras channels.

Mitsubishi has opted for the increasingly popular and highly efficient JPEG 2000 compression system for smoother, more detailed recording and playback. Image data is stored on a pair of 250Gb drives – supplied as standard – with provision inside the case for an optional third 250Gb drive. For the record, it uses a custom version of the Linux operating system, which bodes well for stability.

There is a choice of six quality modes, (frame or field recording); this determines the amount of detail in video images and as a consequence the duration of the recordings that are stored on the drives. In Field recording mode resolution is 720 x 288 pixels, and this rises to 720 x 576 pixels in Frame mode.

Maximum recording time varies according to the configuration, but to give you an idea, at the highest (Super) quality setting in Field mode at 50fps, with all camera inputs in use a single 250Gb drive fills up and starts to overwrite recorded data in a little under 34 hours. Switching to a recording rate of 1fps increases recording capacity to 65 days. Reducing the quality setting to the midway (High) setting increases recording times to two days and 99 days respectively. The TL5000 also has a 4-channel PCM audio recording capability (with an optional sound card). This also has an impact on recording times, which are displayed in the setup menus when changes to quality and picture mode settings are applied.

Each video channel has its own motion detection, alarm and 'emergency' recording facilities (the latter activated by hard wired Panic buttons) with variable pre-alarm recording – up to 60 minutes in the case of motion and emergency triggered recordings. Alarm and emergency recordings are stored on a separate protected partition on the hard disc drive so they cannot be accidentally erased or overwritten.

Recordings may be archived and exported by a variety of means. The machine has a built-in CD/DVD writer drive and it can be connected to a removable memory module or external hard drive via one or more of its six USP ports (two on the front, four on the rear).

The machine automatically records a small image viewer utility onto the storage media so that recordings can be replayed on any Windows XP/2K PC. Recordings can also be copied to tape using the DVRs analogue video output. There is a provision to export system settings to disk or memory module as a means of preserving setup data or to configure a multi-DVR system where several units may need to share the same settings.

In common with most recent DVRs the TL5000 has 10/100 Ethernet network connectivity and a built-in video server so live and recorded images can be viewed across a LAN on a PC web browser (Internet Explorer only, unfortunately). The network connection also provides remote access to a number of setup and configuration settings. Moreover it can be programmed to send alerts by email in response to alarm or motion detector activation.

TL500s can be used as a stand-alone DVR or 'cascaded' with up to 16 other units, providing coverage for up to 256 cameras, controlled from one 'master' DVR. It doesn't end there and expandability has been given a high priority. The three internal drives can be supplemented with dedicated external extension units (DZ-XD5UE); each one provides an extra 500Gb storage on two drives. Extension units can be daisy-chained together, giving a theoretical maximum storage capacity of an incredible 34 terabytes. When pressed a Mitsubishi spokesperson admitted that such a configuration had never actually been attempted, or is ever likely to happen in the real world, but it's there if you need it...

We'll round off the main features now and playback speed and direction is controlled by a jog/shuttle dial. Stored recordings can be searched by time/date and start/end points, alarm list and motion detection. Recordings can also be 'bookmarked' for rapid retrieval. There's full PTZ camera control from the front panel or an optional keyboard with telemetry data sent via camera cables or a network connection.

Physically it is an imposing beast and the front panel is dominated by a centrally mounted backlit LCD showing status information. To the right of that is the jog/shuttle dial, a bank of illuminated camera selection buttons and display mode keys. On the left of the display is the CD/DVD writer. Below that is a row of status indicator LEDs, the playback controls, mode buttons plus a pair of USB ports and a video output socket. The latter are hidden from view by a hinged flap.

The back panel is a veritable forest of sockets for the camera inputs and loop throughs (BNC), twin video monitor outputs (BNC and S-Video), LAN sockets for network and external drive connections and audio inputs and outputs (RCA phono). There are also banks of spring terminals for the alarm inputs and outputs, a D-Sub (RS232) socket for an external keyboard and a pair of RS485 sockets for cameras control and cascade connection to other TL5000s.

Setup and operation

Promo literature for the TL500 somewhat optimistically suggests that the initial setup Wizard and on-screen menus 'make everything so easy that you can forget the manual'. Whilst it is true the DVR can be up and running straight out of the box without too much fuss, most changes to the factory defaults are best carried out with the manual close at hand.

Part of the problem is the on-screen display. Some aspects of the OSD are quite good. For example the menus are semi transparent so you can still see the camera image and a PC mouse is used to move a pointer, to make and change menu selections. The alternative is to use the front panel buttons but this method is painfully slow and best avoided. The relevant keys are widely separated and due to the panel cosmetics and labelling (black printing on a dark grey background) are almost impossible to see unless the front of the machine is very well lit.

Clicking the mouse in the lower part of the screen brings up the first of three menu pages, each one with six on-screen buttons leading to further sub menus. The button labelling and sub-menu wording and layout is at best ambiguous; in places it is downright confusing. Menus look cluttered and buttons are also labelled alphabetically or numbered, to correspond with the front panel keys. On the plus side each menu page has a Help icon that displays a short (though not always very enlightening) explanation of the options on each page.

Other little annoyances include having the Exit button for each menu page at the top of a numbered (in reverse order) list. It may be that a cynical observer (not us, of course...) might conclude that the OSD was originally designed to appear at the top of the screen with 'drop-down' sub-menus, until someone pointed out that it would obscure important detail so the decision was taken to flip it over and move it to the bottom of the screen.

It took us a while to work out where some quite basic functions were tucked away, though in practice once you've deciphered the buttons and figured out the way menus work most operations are reasonably straightforward. The same cannot be said for playback and the Search facility. What the TL5000 really needs is more on-screen information and simply pressing the Play button, in the hope of navigating your way to view part of a recording, will almost certainly result in you getting quickly and comprehensively lost.

The Search facility works well enough when you have a good idea of the time and date of a particular event. Even so the cumbersome menu display makes it heavy going, requiring the user to click on a succession of boxes, and if you make a mistake you have to wade through a sequence of menus to go back and change the settings.

Things improve slightly when using the network connection; the browser display and menus are a good deal more intuitive and easier to use. The first step is to type in the DVR's IP address in the browser window, and this displays a login screen.

Switching to the live display initiates the download of a small Active X plug-in from the DVR, which only takes a few moments. The browser window can be configured to show live images from up to 16 cameras in the full range of display formats and replay stored recordings using a simple time search facility and Alarm list. There's also an abbreviated set of configuration settings and the email setup menu. One or two dialogue boxes could do with a quick grammar check; we particularly like the one that says 'Acquisition of an image was failed'.

Initially we had a few problems exporting recordings to CD/DVD and USB memory modules. This was mostly due to the scant instructions, which are not terribly helpful in this respect.

It took several attempts and a handful of dud disks before we fathomed it out but the good news is that perseverance pays off and once you've got the hang of it the process is actually quite simple.

Performance

The decision to use the JPEG 2000 compression scheme has certainly paid off. Image quality on the TL5000 is at or close to being the best we've seen on a top-end DVR - only a side by side comparison with one or two other machines we've tested recently will tell - but the bottom line is that in the top quality settings it is able to capture and reproduce a lot of fine detail. Colours are accurately rendered and look pin-sharp with good balance. Images have a wide contrast range and there's virtually no picture noise.

Lowering the quality level makes small incremental reductions in resolution and a slight softening of edges but this doesn't become significant until you get to the 'basic' and 'standard' quality settings, at which point picture artefacts can become quite noticeable. The jog/shuttle dial provides very precise control over playback speed and direction, from fast search to stepping forwards or backwards a single frame at a time.

Playback controls via a network connection on a web browser are not as sophisticated and picture quality is degraded slightly though it helps that images are displayed in a window that occupies about a quarter of the screen area. Losses can also be offset to some extent by adjusting the local settings and the data transfer rate.

Build quality is outstanding and nothing short of an earthquake or an argument with a sledgehammer is going to trouble this beast. By the way, Mitsubishi appears reasonably confident that the TL5000 will continue to function for at least the next 22 years, judging by a small footnote in the manual, which warns that the internal clock is programmed up until the 31st of December 2037...