WHY DVD?
By Richard Chycki
The most pervasive versatile medium for the movie, music and computer
industries are taking the world by storm. As a mixer, I’ve noticed
a profound increase in music industry-based DVDs. Naturally, any live
performance music product is far more enjoyable as a multimedia surround
presentation. With the CD portion of the industry in such serious flux,
it’s critical that consumers are given strong value for their dollar.
With DVD, you not only get the music in an interesting new environment,
you can get interviews, photo montages, DV footage from the making of
the music – really great stuff that truly personalizes and enhances
the overall experience. I’d like to share some tech info about the
origin and specs of the DVD format.
DVD Defined
Striking yet another death knell to the once eminent magnetic, media,
DVD is a next generation robust optical-based media using similar laser
reflection technology as the venerable compact disc. Originally dubbed
the ‘Digital Video Disc’, the format’s ability to pack
up to 17 GB of data onto a single double-sided disc has made it popular
for data purposes in the computer world too, hence the updated nonmenclature
‘Digital Versatile Disc.’
To achieve this impressive increase in data density while retaining the
same package dimensions as the CD, the DVD incorporates several improvements
in the current CD spec. Like a CD, the DVD uses tiny pits arranged in
tracks etched into substrate to modulate the reflection of a laser following
along the track of pits into a pattern of digital 1s and 0s. The increased
data density is achieved through these methods:
By reducing the length of the data pits from CD’s minimum size of
0.83 pm to 0.4 pm
By increasing the track density through the reduction of the intertrack
space from 1.6 pm to 0.74 pm
By writing data to both sides of the disc, Multilayer technology, where
data is written in the same lateral space.
CD and CD-ROM units use an infrared laser emission at a wavelength of
780 nm. DVD players/DVD-ROM drives use a laser with a red light emission
at shorter wavelength of 650//635 nm. A shorter wavelength is better suited
to reading the smaller, more densely packed pits as is the higher numerical
aperture lens built into the laser assembly to narrow and more tightly
focus the laser beam.
An increase in data density is useless if the storage media is unreliable.
DVD’s error correction and digital modulation schemes have been
enhanced to support the increase in data density over CD. The Reed Solomon
(RS-PC) error correction system incorporated in DVD is 10 times more robust
than the current CD system and the EFM Plus modulation scheme is both
efficient and ensures backward compatibility.
Audio Advantages
Current DVD-V standards allow for a stereo linear PCM data stream that
sonically exceeds the current compact disc standard. Indeed, DVD-A offers
more than double the bandwidth of a standard CD with an increase in wordbit
resolution to 24 bits. To conserve bandwidth for multiple language audio
tracks and multi-channel formats like 5.1 surround, loss y data compression
is used to reduce the overall audio file size while attempting to retain
as much quality as possible. Although Dolby’s AC-3 compression technology
is the current de facto standard, DTS is widely acknowledged as sonically
superior for music product. Both choices easily surpass VHS’ best
performance. The versatility to allow high quality multiple content/format
audio is a huge step forward over VHS tape. The DVD format reserves tracks
for a multitude of language tracks, greatly simplifying the international
proliferation of a DVD product.
Viewing Quality
Lines of resolution are the key factor here. The venerable VHS format
allows for a meager scanning resolution of 210 lines at its SP setting.
Raising the bar substantially, DVD allows for a scanning resolution of
540 lines – a 257% increase in video quality. In addition, widescreen,
letterbox or panned formats are easily accommodated.
Investment Protection
Content Scrambling System (CSS) is an encryption method optionally built
into DVDs to restrict access to the product in certain situations –
like unauthorized copying/duplicating or the export of the product to
an unintended geographical region. Regional coding was implemented to
better control the product flow and protects a film company’s investment
in new film product. Regions of distribution in the DVD coding are as
follows:
Region 1 – USA, Canada
Region 2 – Europe, Japan
Region 3 – India, Pakistan, Asian Pacific
Region 4 – Latin America, Australia, New Zealand
Region 5 – Africa, Russia, Eastern Europe
Region 6 – China, Hong Kong
Fortunately, the DVD format has yet to encounter the industry destructive
‘set-and-forget’ copy vehicles omnipresent in the troubled
CD world. Coupled with CSS, the hefty file size of encoded, compressed
audio and video makes proliferation somewhat impractical over the Internet,
without recompressing the material further and substantially degrading
the copy quality. Internet service providers generally bill a surcharge
once a client’s download quantity exceeds 5 GB/month – the
data contained in a single-sided, single layered DVD – so a casual
data pirate can expect substantial data overage charges for transmitting
a number of DVDs, after the hardware is purchased and the CSS is cracked
sans artifacts. In comparison, a CD is unprotected, uncompressed, and
converted to MP3 format amounts to roughly 45 MB of data. More than 100
CDs can be transmitted via the Internet per month without ISP intervention.
In The End, Who Wins?
According to the International Recording Media Association, DVD players
are already in over 37 million US homes. It’s the fastest-growing
consumer electronics product in history.
They’re robust, they’re versatile, they’re inconvenient
to pirate and they’re here to stay. With an advantage for almost
everyone, the development of new DVD product as well as the reissuing
of catalog material in this ubiquitous format is a most wise production
investment.
original link: www.professional-sound.com
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