DVD - The future of CD

        A look at DVD technology by Richard Hewison.

DVD has finally arrived in Europe, and about time too! For those
of you who are unfamiliar with this new CD format; DVD is
physically the same size as a standard CD but it can store seven
times as much data on a single sided single layer disc. DVD also
comes in single sided double layer and double sided double layer
formats.

DVD was originally an acronym for "Digital Video Disc". The
technology was developed so that Hollywood studios could fit an
entire movie onto one small CD. The search for this particular
'holy grail' began in the early 90s and for a while there were
two different groups developing rival formats. A 'format war'
along the lines of VHS and Betamax seemed inevitable until they
finally saw sense and united together, merging the ideas into one
product - DVD. The acronym was eventually changed to represent
"Digital Versatile Disc" because the technology could also be used
in the home computing sector.

Normal CDs are 1.2mm thick. A DVD disc consists of two 0.6mm
substrates bonded together. The pits that scatter the laser beam
have been reduced considerably, they are more densely packed than
a normal CD, the tracks are much closer together and they are also
much finer. You therefore need a laser operating at a much shorter
wavelength to read the discs. However, the result of all this
means that the lowest DVD format (single sided, single layer) can
store 4.7Gb of data compared to 650Mb on a normal CD. The highest
format (double sided, double layer) can store an enormous 17Gb!

Fitting movies onto CD has been tried before. Anyone with a CD-i
player will remember the VideoCD format. This used standard 650Mb
CDs to store films. To achieve this they had to use a compression
technique known as MPEG-1. MPEG is an acronym for the "Moving
Picture Experts Group" who worked in the US under the joint
direction of the International Standards Organisation (ISO) and
the International Electro-Technical Commission (IEC). MPEG-1
compression allowed up to 50 mins of sound and video to be stored
on a normal CD. The picture quality was acceptable but suffered
from 'artefacts' - blocky areas which moved as the action moved.
PCs could play the films but they needed to have an extra MPEG
card to run them at the required speed.

MPEG-1 movies were nothing more than an interim step. They failed
in the US, mainly due to the healthy state of the Laser disc
market.  They also failed in Europe thanks to the failure of the
CD-i machine which was required to play them. PCs could play the
movies but they needed extra hardware to run them at the
sufficient speed. Today, a mid-range Pentium should be able to
play a VideoCD without the need for extra hardware, although you
need to check that your CD-ROM drive can read 'White book' CDs.
This is the physical format used by VideoCDs. Normal audio CDs
use 'Red Book', CD-ROMs use 'Yellow book', etc.

DVD movies use MPEG-2 compression. This is a much improved
compression technique over the original. Not only is the
compression better, but the quality of the picture output can be
astonishing.  Throw in the enormous data storage capacity of the
DVD format into the mix and you should be able to see now how DVD
can fit an entire movie onto one side of a disc. For example,
"Jerry Maguire" starring Tom Cruise runs for 133 mins and fits on
one single sided DVD.

DVD movies actually comprise of five different elements; video,
audio, extra language soundtracks, subtitles and
closed-captioning, and interactive menus. Depending on the film
you might get both normal TV and original Widescreen versions on
the same disc. You might also get a choice of language
soundtracks, subtitles, film trailers, interviews with the stars,
behind the scenes documentaries etc.  Sound will probably be in
either AC-3 format (Dolby Digital 5.1) or MPEG-2 formats, although
you will still be able to hear them in stereo if your TV or Amp
doesn't conform to any of those. AC-3 is a high quality audio
coder which gives you six audio channels; left, centre, right,
left-surround, right-surround, and a low frequency sub-woofer
channel. In comparison, Dolby Pro-Logic (a.k.a. Dolby Surround

Sound) gives you left, centre, right and left & right rear
surround (mono).

DVD movies also have interactive menus where you can jump to a
particular section in the movie instantly. These are referred to
as chapters and have been a standard feature on Laser disc for
years.  You can also choose the language from these menus, as well
as access any other extras which have been placed on the disc.

The picture quality of a DVD movie depends on the source material.
If the original print of the movie is flawed in some way then so
will the DVD. The quality control at the compression stage can
also result in a flawed DVD. It is possible for the quality of a
movie to vary within the movie itself. However, it seems that the
releases made so far have all scored highly on the picture quality
front so publishers and Hollywood studios have obviously made the
necessary commitments to ensure that DVD movies are not
compromised when it comes to quality. If possible, have a demo
before you buy one or read a couple of reviews beforehand.
However, DVD is much better than VHS in screen resolution terms.
VHS has a screen resolution of around 240-250 lines. DVD has
double the resolution, making the picture crystal clear instead of
soft and slightly smudgy. Remember that a modern UK TV has a
resolution of 625 lines to play with, and VHS uses less than half
of them to make up the picture.

Most DVD films have been regionally coded so that they can only be
played on a particular player.  There are six regions, with the US
being region 1 and Europe and Japan being region 2. The US use the
NTSC TV system so Region 1 is strictly NTSC only. Region 2 though
comes in two TV standards; namely NTSC (for Japan) and PAL for
Europe. Other regions include Australia (region 4). Officially a
player can only play region-free DVD or DVD for one particular
region. The reason for regional coding is related to the
difference in movie release dates around the world. Quite often, a
film is released on video in the US only weeks after it has been
released in the cinemas in the UK. By restricting the UK to PAL
only players, the Hollywood Studios have some control over which
films can be watched and when.

For movie collectors, the regional coding barrier is particularly
irritating. However, there are a number of ways around it. The
first method is to order an NTSC player and NTSC DVD movies from
the US.  Some players can then be physically modified to play any
region.  This is all strictly unofficial and will invalidate any
hardware manufacturers warranty on the player in question.
Apparently it usually involves cutting a wire to a chip or
soldering a custom chip to one of the circuit boards inside. It is
also rumoured that some players have simple dip switches inside
which can be set to a region free mode.

The second method for circumventing the regional coding is to buy
the new Creative Labs DVD Encore kit which gives you a CD-ROM
drive which can handle all your usual CDs (CD audio, CD-ROM, CD-R,
etc) but it can also read DVD movies. This kit comes with an
MPEG-2 card called the DXR2. It includes resolution doubling
software to improve the output to your PC monitor. The back of the
card has RCA phono and S-VHS connectors for sending the picture to
your TV instead. This kit is driven by software and there are
programs on the Internet which allow the drive to by-pass the
regional coding and thus let you play any DVD movie you like. The
only problem you might have will be related to your PC monitor or
TV. They must be able to display pictures at 50Hz and 60Hz
frequencies so they can handle both PAL and NTSC signals. Again
this 'fix' is highly unofficial but it's difficult to believe that
Creative Labs didn't leave the door half-open just so this kind of
thing could happen. Their official software allows you to change
the region five times before you are stuck with one region
setting. Why did they do this? They must have known how easy it
would be for someone to beat the system. Once it's been beaten,
Creative Labs can only benefit because more and more people will
buy their DVD Encore kits! Coincidence? Who knows?

The future of DVD is very bright. Over 1000 movies are available
in the US, and the UK has over a dozen available right now with
more due every week. Prices aren't bad either - between œ15 and
œ20 per movie. Older films will get re-released on DVD at the
lower price point and might also be region free.  The future will
see DVD-ROM take a hold in the home computer market (there is
already a DVD version of "Wing Commander IV" which comes on one
double-sided DVD) and further into the future we should also see
DVD-RAM. There is also the possibility of DVD-audio which should
wipe the floor with standard CD audio. After all, a standard CD
can only hold 74 mins of audio. A single sided single layer DVD
should be able to store over 500 mins (over eight hours!). I
suspect that the music industry will resist DVD audio for as long
as possible. After all, fitting seven CDs onto one DVD sounds
good but they won't get away with charging seven times the price
so they will lose out on revenue.

At the end of the day, the best way to become convinced of DVD is
to see it in action. PAL movies are already being sold in Virgin
Megastores and Sony Centres. DVD players are also popping up all
over the country from Toshiba, Pioneer and Sony to name just a
few.  The players retail at around œ450 - œ600 on average, whilst
the Creative Encore DXR2 kit can be found at under œ180 inclusive
if you know where to look. The future of home entertainment is has
finally arrived!

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