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MIXED EMOTIONS
INTRO
Video mixers are the ultimate post-production
tool but most movie-makers can only dream of owning one. Now, maybe, Video Tech
will be making some of those dreams come true....
COPY
Until you’ve actually played around with a
video mixer it’s difficult to see what all the fuss is about, but it only takes
a moment to get hooked! The facility to mix or wipe between two images might
not seem that important, after all editing and other post production effects
are now so accessible, and it’s possible to create professional-looking video
movies with just a few inexpensive gadgets. Nevertheless a mix or wipe from one
source to another cannot be achieved any other way, and it is the one effect
that has remained stubbornly out of reach of most video movie-makers due to the
high cost of the equipment. It’s been over eight years since the first
‘domestic’ mixers from Panasonic appeared but in all that time the official
ticket price of new mixers has never dipped below £1000.
Video Tech have broken the log-jam with the
VMX410. This fully-featured 2-channel digital vision mixer/processor and
4-channel audio mixer, designed and built in the UK, is now reaching the shops
where it will be selling for just under £800. By any reckoning that’s still quite
a lot of money, but when you see what it can do, and compare it with the competition,
it might just look like a bargain!
The relatively high cost of digital vision
mixers, including the VMX410, can be directly attributed to the complex
circuitry needed to combine two free-running video sources. Mixing one video
signal with another depends on one of the inputs being temporarily stored in a
digital memory, and read out again, so that it is in perfect synchronisation
with the other one. That’s no mean feat, and Video Tech have had to use some heavy-duty
technology in order to do it.
Interestingly the front-end digital conversion
chips in the VMX410 are the same as those used on some rival mixers but the
rest of the circuitry, including the main effects processor, are all home-grown.
This is a no-compromise design. The cost-savings are not a result of any
corner-cutting but a welcome spin-off from the computer and multi-media
industries, where the increased supply of specialised digital video processing microchips
has driven prices down.
Once a video signal has been converted into
digital data you can do all sorts of interesting things with it. In the case of
the VMX410 that includes:
* 60 wipe patterns, with 4 stages of edge sharpness
* glitch-free switching between channels
* wipe or mix to each or both input channels or
one of 10 background colours
* picture-in-picture (PIP)
* five different sizes of PIP sub-screen, positionable
anywhere on the screen
* PIP screen ‘window’ through which the
second input channel can be viewed
* plain or bordered PIP screen
* chroma and luminance keying
* positive/negative chroma and luma switching
* brightness, contrast, saturation and detail
adjustment
* colour/mono switching
* digital still frame (frame or field mode)
* colour re-registration
* timebase correction
Some of those features might be unfamiliar
and deserve a little explanation. Colour re-registration can correct small
alignment errors that occur on recordings made on some VCRs and camcorders,
where colours appear to be displaced. The 410 can shift colours vertically by
up to 3 TV lines, and horizontally in seven 100nS steps, which should be enough
to get most recordings back into shape.
Video signals piped through the ‘A’ channel can be treated to a dose of timebase
correction. This regenerates weak or degraded synchronisation pulses, which
comes in handy when dealing with noisy or wonky source material. In fact the
timebase corrector on this device is unusually versatile and can even lock on to
video signals where the synch pulses are missing.
Chrominance and luminance keying can be used
to create the familiar ‘weather man’ effect, where the subject -- shot against
a coloured background -- is superimposed on top of an image coming from the
second input channel. The system used on the VMX410 is very flexible and can be
adjusted to key to almost any colour or brightness level. These are selected by
placing a moving cursor over a nominated section of the picture.
The video processor facility has four
memories, so picture adjustments on channel A can be stored and quickly changed
to suit different inputs. The still frame works in field or frame mode. Frame
stored images give the highest quality but if there’s any movement in the scene
this will show up as a judder, in which case the field mode can be selected,
for a rock solid, though slightly less well defined picture.
Wipe and mix effects can be controlled manually,
from the left hand fader (the one on the right is for audio), or triggered
automatically, with a programmable transition lasting up to 8 seconds.
Several additional facilities can be generated
by combining various effects modes. Some of them, like ‘feedback’ produce a tunnel of PIP screens of ever diminishing
size will have sci-fi enthusiasts in raptures. That’s just a quick run-through
of what it can do, we’d need rather more space than is available to do all of
the effects justice, so on now to more mundane matters.
The two input channels can handle either
composite or S-Video configured signals, or a combination of the two, converting
between one format and the other. The quoted bandwidth is in the order of 500-lines,
which means it can comfortably accommodate video inputs from the latest digital
camcorders. By the way, did we mention it has an audio mixer as well? This has
four input channels, including one for a microphone, and there’s a headphone
monitor socket, with variable output.
Several effects and processor settings can be
triggered externally, using the mixer’s GPI (general purpose interface) socket.
Video Tech thoughtfully provide full details of the control protocols, for
those who may wish to use it with other items of post-production equipment.
The whole caboodle is housed inside a
neat-looking sloping console, with all of the input and output sockets on the
back panel. The various effect and option buttons are laid out logically, with
LED displays showing which modes have been selected. At first this approach
appears a tad cumbersome, and it has to be said that moving from one option to
another can involve a fair amount of button prodding, but you quickly get used
to it. One word of warning though, the unit comes with a crib-sheet, detailing
all of the various wipe patterns, don’t loose it otherwise you’ll be lost...
PERFORMANCE
Normally we expect to find a few rough edges
on ‘domestic’ video mixers but the VMX410 has one of the cleanest repertories
of effects we’ve seen, with impressively few tell-tale signs of the digital
processing taking place. Transitions are very smooth, with no instability at
the changeover points. Colours are noiseless and uniform, and PIP screens have
none of the digital artefacts commonly seen on other types of processor.
However, top honours go to the chroma key facility, which compares very
favourably with professional systems. With care, and good, even lighting it’s
possible to get almost perfect superimposition’s, with none of the whiskery
edges that usually give the game away. Low-band and S-Video signals passed
through the processor without any additional noise and colours remained
unaffected.
The audio mixer is a bog-standard design, the
VU meters are a useful touch, but really there’s not a lot to say except that
it works well, the faders are smooth and progressive, and (so far) noiseless.
VERDICT
Apparently Video Tech have been working on a
video mixer for several years. We’ve known about the VMX410 for a while, but it
sounded too good to be true. Launch dates kept on being put back so we’ve been loath
to say anything about it until we saw one in the flesh. Well, it’s here now and
it has definitely been well worth the wait. Performance is outstanding, equal
to or better than anything else we’ve seen in the past eight years, and the
very attractive price must put it at the top of any ambitious video-maker wish-list.
We just hope Video Tech can make enough of them to satisfy demand. Recommended
THE RIVALS
This is a small market and the VMX410 has few
serious rivals, at least as far as performance and facilities are concerned.
The main competition comes from the excellent Videonics MX1 and if you shop
around you can pick one up for around £1100. Panasonic have just launched the
WJ-AVE55 production mixer, it looks very well specified with several
interesting effects, but we haven’t had a chance to fully evaluate it yet, but
the list price of £1100 rules it out as a direct competitor. We liked Vivanco’s
VM-500 (see April VC), but again the price at £1200 is quite a lot more than
the VMX410. If funds are limited then it’s well worth a trawl through the ads
for the ageing and relatively unsophisticated Panasonic WJ-AVE5 which we’ve
seen selling for less than £500; it’s bigger brother the AJ-AVE7 has been
advertised for just £700, though if you’ve managed to scrape together that much
we’d strongly suggest you try to find another £100 for a VMX410.
SPECIFICATIONS
Make/model: Video Tech VMX410
Typical price: £800
Features: 2-channel vision mixer with timebase
corrector & 4-channel audio mixer
Effects: 60-wipe patterns and fade/mix to
background colour or second input,
chroma and luma keying, picture in picture (PIP), freeze, video
processing with 4 setting memory (contrast,
saturation, brightness, pos/neg), auto fade (variable speed), colour
re-registration,
Sockets: AV in/out (phono & S-Video), headphone & microphone (jack),
external control (mini DIN), DC Power in
Dimensions: 410 x 70 x 265 mm
PERFORMANCE
Effects definition excellent
Effect
stability very good
Audio mixing very
good
VC RATINGS
Value for money *****
Ease of use ****
Performance *****
Features *****
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Ó R. Maybury 1996 0904
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