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GEUTEBRUCK MULTISCOPE
COPY
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 NUMBERS GAME
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.
PERFORMANCE
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.
OVERALL ASSESSMENT
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
PRODUCT
ASSESSMENT
Design and
design features ****
Circuitry and
components *****
Ease of
installation and wiring *****
Range and
variety of functions ****
Accompanying
instructions ****
Technical
advice and backup ****
Value for money ***
---end---
© R.Maybury 1995 1402
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