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Magnetic tape’s dominance, as the primary recording medium for video, is assured for a while yet, but it is clear that other media are beginning to make their presence felt. At the centre of what will become a fundamental change in video recording technology is digital processing and storage. Digital video systems have a number of important advantages over their analogue counterparts, and they pave the way for increased picture quality, advanced motion detection and image analysis systems, no-loss copying, plus improved flexibility for the installer and end-user.  


The first generation of digital video tape recorders have been very successful in the broadcasting and professional sectors, but currently have little to offer the surveillance and security industry, over and above what is already available from analogue equipment. However, that will change and it is likely that newly developed digital cassette formats, intended for low-end pro and domestic applications will find their way into the surveillance market by the end of the decade. Disc-based video recording systems have also been around for a while, and have enjoyed limited success in high-end video security but it now looks poised to reach a wider market, following the launch of the Geutebruck Multiscope Video disc recorder late last year.


This device combines many of the functions of a time-lapse video recorder with a switcher, multiplexer for up to four colour cameras and alarm handling, but instead of recording images in an analogue form on tape, they’re stored as compressed digital data on a 540 megabyte hard disc drive, identical to the type used in personal computers. Multiscope owes more to the computer industry than  VCRs or analogue video, though the concept of disc-based recording is far from new and Geuterbruck have a 25-year history with this technology. 



The core technology behind Multiscope is video compression. Digitally processed images contain vast amounts of information -- one seconds worth of video will typically contain around 27 megabytes worth of data -- Multiscope uses the JPEG  (Joint Photographic Experts Group) compression system, which can reduce the amount of data in a single frame of colour video to less than 20 kilobytes, at the high-level setting. The system has two alternative compression levels; medium with 20 to 25kB per frame, and low, at 30-35 kB per frame. JPEG compression works on the assumption that adjacent frames of video are almost identical, so to reduce the amount of data the system only processes the parts of the image that are changing. i.e. any movement. Multiscope’s 540 Mb disc drive can store a maximum of 29,760 frames, at the high-compression setting, or just under 8,000 low-compression pictures. In real terms that equates to over a fortnight’s worth of uninterrupted recording at the longest time-lapse intervals. We will be looking at how the system operates in a moment, but first a overview, and a summary of what else it can do.


Multiscope is housed inside standard rack-mount or desktop cases, the sample we’ve been evaluating is the latter type, the cabinet measuring 450 x 45 x 400mm. On the front there are four banks of buttons; the first fourteen are concerned with recording, camera sequencing and selection. next to that are the set-up controls. The next group are for selecting and controlling replay, and the last three buttons are for the alarm playback functions. The back panel has five pairs of BNC and S-Video connectors for the four camera inputs, the fifth is for the monitor output. There are three 15 pin D-sockets, one is for the four alarm inputs, the other two are for serial communications with external devices and PC control. The last multi-pin connector is a 50-pin Delta ribbon ‘scuzzy’ socket or SCSI (small computer system interface) for up to four additional external hard disc drives, to increase recording times, or an optional DAT (digital audio tape) recorder, for permanent data backup and storage.


The unit is controlled by a menu-driven on-screen displays and the initial set-up screen selects operating language, video system, camera inputs, date and time, compression level and various housekeeping functions. The options also include protection against unauthorised by an operator defined PIN code; alarm set parameters (interrupt sequence on alarm activation), set camera dwell time (0 to 99 seconds), plus compose and position text for the on-screen camera idents (1-line/24 characters).The record mode set-up menu defines the storage interval when the system is in the record mode, the options are for live or real-time recording or intervals of 0.1, 0.2. 0.3, 0.4, 0.5 and 0.8 second when using a single camera, or 1 to 10 seconds (in 1 second intervals) and 20 to 240 seconds (in 10 second steps) with multiple camera inputs. A second interval for each camera can be set following an alarm activation. Alarm options include quit with contact, (alarm terminated via the contacts), quit with timer (pre-set interval up to 9999 seconds), or quit by key, using the button mounted on the front panel. Alarm triggered recordings are tagged and displayed on the monitor screen.


Operation is fully automatic, once configured and powered up it goes directly to the chosen recording mode. The user has the option to be warned when the hard disc is full up, (or approaching full capacity), and manually re-initiate recording, or it can be set to automatically over-write previous information in a continuous cycle; an on-screen indicator appears when the disc is nearly full. Playback of recordings from any or all of the connected cameras can be initiated at any time, options include forward or reverse play at variable speed (the same intervals as the recording mode), this is shown graphically by the display as a horizontal bargraph. In addition to manual search the operator can also access a particular segment of the recording by specifying a time, date or alarm event.



Several of the major benefits of disc-based recording are immediately obvious during playback. The picture is stable at all recording speeds, direction changes are instant and totally seamless, moreover it can be stepped a frame at a time (in either direction) for detailed analysis with no noise bars or picture instability disrupting the picture. Image quality at the highest compression setting is fairly ragged and really only useful for gross area monitoring. The medium and low compression modes are better suited to critical identification and they compare very favourably with and in some circumstances is better than recordings made on conventional VHS tape machines, though clearly much will depend on the type of cameras used. The side-effects of compression are really only visible on highly compressed images, which look very blocky and contain a lot of digital artefacts. Moreover, during single-camera real-time recordings there is regular frame-jumping, giving movement a slightly jerky quality, though this would not be a problem in a multi-camera set-up making interval recordings.


Installation and operation are both very straightforward, though from an ergonomic point of view the skewed control buttons on the front panel make life unecessarily difficult. The only other minor quibble concerns access speed. The recording can be shuttled backwards and forwards at normal recording speeds, but there is no separate high-speed picture search facility, so to getting to a particular point on the recording can be quite time consuming. The options are to move through the recording at maximum replay speed, or manually input a time and/or date using the search menu. Alarm tagged events can be accessed directly, though, using a pair of buttons on the front panel.



Analogue video tape recording is not dead yet, far from it, but Geutebruck have convincingly demonstrated that it’s days are numbered. As it stands right now Multiscope is a viable, if somewhat costly alternative to tape-based time-lapse machines, though it is unwise to make too many direct comparisons. It comes into its own in  specialised multi-camera set-ups, where image quality is important, there is a need for continuous, unattended surveillance, and a very high level of reliability. Multiscope is just a taste of things to come!


End-user price £5200



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