NEW AUDIO MEDIA
Digital audio is shaping the future of hi-fi but how will the new
technologies affect video movie making?
The days when sounds and pictures are represented by gently undulating
waveforms are rapidly coming to an end; in the digital age information is
recorded, and stored as streams of numerical data, and sooner, rather than
later, that will include domestic
camcorders. In some quarters it already does, Sony pioneered the use of digital
PCM (pulse code modulation) audio recording systems on the Betamax F1 portable
outfit back in the mid 1980's, and their PRO series camcorders have featured
PCM sound for the past four years.
Digital sound has had a dramatic effect on domestic hi-fi, Compact Disc
is now the prime carrier of music in the home, and sales of vinyl records have been falling like a stone for the past
three years, even the good old compact cassette is nearing the end of the line.
When you look back over the history of recorded sound it seems that on average
domestic audio formats have a 20 to 25 year life cycle. Depending upon your
point of view the worlds consumer electronics manufacturers either recognise or
engineer this trend, and somehow always seem to have a replacement ready and waiting, There are currently two
contenders poised to take over from compact cassette, actually there were three
but digital audio tape (DAT) which uses a rotary head recording system, very
similar to video in fact, was launched in 1988 and peaked a little too early. It
suffered by being too complex and expensive but it hasn't disappeared
altogether, though, and has since found
a niche for itself in professional and broadcast audio.
The battle is now on for the compact cassette mantle; in the red corner
we have Sony's optical Mini Disc or MD, in the blue corner is the tape-based
Digital Compact Cassette or DCC, developed by Philips. Both systems offer
broadly the same kind of recording and playback facilities, and, from a
consumer standpoint, sound pretty good, comparing favourably with Compact Disc.
DCC's main advantage is that the new generation of decks will be backwards
compatible and can play analogue compact cassettes. MD has immense gadget
appeal plus CD-like immediacy and rapid track access. Early sales figures
suggest that MD has taken an early lead but both systems face a long haul, and
in the end it will probably be the range and availability of software that will
decide the issue.
So does this have any relevance to video movie-making? Yes, is the simpler
answer, both DCC and Mini Disc used sophisticated psychoacoustic (try saying
that with a mouth full of toffees...) data compression techniques to cram a lot
of information into a relatively small space. They reduce the amount of data
going onto the disc or tape by discarding sounds that the engineers at Sony and
Philips have decided we either cannot hear, or would naturally ignore as
they're masked by other, louder sounds. PASC (precision adaptive sub-coding) on
DCC and ATRAC (adaptive transform acoustic coding) on MD both have promising
futures in other forms of digital sound recording and you can bet your bottom
dollar, or yen, that son of PASC or ATRAC will turn up on a camcorder near you
Of more immediate interest is what DCC and MD can do for you right now.
Of the two systems MD has the greatest potential for video movie-makers, not
for any technological reasons but simply because the first DCC machines are all
mains-powered audio components. Sony took the view that a portable Walkman-style
player/recorder would be more attractive, and judging by its early lead they
may well be right. We've managed to acquire one of a Sony MZ1 MD machine, to see what it can do, and we've also been
lucky enough to get hold of one of the first ECM-727 microphones in the
country, it's brand new and has been specially designed for this kind of
digital media. They're not cheap, the MZ1 costs £500 , and the mic a further
£100 , but if you cast your mind back ten years you may recall that the first
Sony Walkman personal stereos cost over £100, heaven knows what that would be
in today's money!
From the point of view of video movie-making one of the most potentially
useful features of this kind of system is speed accuracy. Camcorder transport
systems are already very stable, with wow and flutter both less than 0.1%, if
audio systems like DCC and MD can match that they could, in theory have
a useful role to play in recording and dubbing soundtracks, something most
analogue cassette decks have never been
very good at because of their relatively crude tape transport systems.
To find out we made a series of test recordings using a Panasonic NV-S20
and Sony TR camcorder, with the MZ1 and ECM-727 along to capture the sound for
later comparison. The recording were all made at the same time, under identical
conditions with all three machines suffering the same kind of physical
treatment. We'll get to how they fared in a moment, but first a few words on
what else the MZ1 can do.
It's a little larger and heavier than a normal Walkman, but it will still
fit comfortably into a coat pocket. The discs are loaded in a slot on the
front, and as soon as you push one in the motorised loading mechanism whips it
from your hand. Once inside the machine sets about telling you what's on the
disc by reading the TOC or table of contents, this is shown on an LCD panel on
the top of the machine. If it's a pre-recorded disc it will tell you the number
of tracks, title and running time. From then on it's pretty much like any other
CD player; press play and you'll hear the whole disc from start to finish, or
you can program in your own track selection. Track access is very fast, taking
no longer than three or four seconds to scan across up to 70 minutes worth of music.
As each disc plays the track title is shown in the display window, along with
track number and duration in minutes and seconds.
The MZ1 comes with it's own set of in-ear phones, but after having tried
the excellent new MDR-D55 headphones, which are an optional extra, we gave the
standard items a miss. Power comes from a 6 volt nicad pack, it has enough
juice to last for the length of one disc on playback, around 70-80 minutes, or
about an hour when recording. Recharging from flat takes around an hour.
External connections include a headphone socket, and dual mode optical
digital/line inputs and outputs, so it could just as easily be used a source
component in a hi-fi system or in-car player, with a suitable adaptor. Making a
recording is no harder than a normal tape machine but there are extra
enhancements, including the facility to give each track a title, using the set
of alphanumeric keys on the top panel. That's really all there is to it, so how
well did it perform?
First stability. If you've ever listened to one of those portable CD
players you'll know that portable is a
complete misnomer, no CD player can take more than a light tap without skipping
all over the place. MD is different, it has an ingenious buffer memory, so if
you give it a whack instead of hearing what's coming off the disc you hear the
contents of an unshakeable solid-state memory which holds up to ten seconds
worth of audio information, so there's no loss of sound, even if you treat it
like a cocktail shaker -- most impressive! Sound quality is pin-sharp, with
excellent clarity and definition.
Pre-recorded discs compare very well with their CD counterparts and it proved
quite difficult to tell MD and CD apart, in side by side comparisons. However,
the MZ1 really came into its own when used for recording. The RZ1 and 727 mike
are a cracking combination, sound quality is stunning, with no trace of
background hiss whatsoever, but it's the pin-sharp reproduction of everyday
sounds that really makes you sit up and take notice. One simple but very
effective test for any stereo recording system is to 'draw' sound shapes, by
shaking a matchbox around the microphone,
describing simple patterns or shapes in the air. On the RZ1 we found
most of our unprimed guinea pigs could 'see' those shapes, when they listened
to the replay, with their eye's closed.
And so we come to our camcorder compatibility tests. As there's no way of synchronising the
two machines the results are a little rough and ready but we found that in our
first test recording all three machines were in almost perfect synchronisation
after ten minutes. After 15 minutes the MZ1 and the Sony camcorder had drifted
apart by maybe a tenth of a second, the Panasonic S20 was still holding its
own. At the twenty minute mark there was no change between the MZ1 and Sony
camcorder but the Panasonic S20 had
started slip behind, though again probably by not much more than tenth of a
second or so. After thirty minutes the differences were still small, no more
than a couple of tenths of a second, with the Panasonic machine slightly
behind, and the Sony camcorder slight ahead. We repeated the tests a couple of
times; on the second test they all finished
together after 30 minutes. In the third and last test both camcorders lagged
behind the MZ1 by three or four tenths of a second.
It's difficult to draw too many meaningful conclusions from such simple
tests, though it is apparent that MD
speed stability is equal to, or possibly better than VHS-C and 8mm video and it
could indeed have a role to play in video movie-making, though without some
means of synchronisation it will have to stay on the sidelines as much still
depends on the user's reaction times.
(c) R.Maybury 1993 1803