Operating instructions

G-5
analog track on the same 35 mm prints. This Dolby Digital format is yet
another significant step forward in film sound, providing independent
left, center, right, left surround, and right surround channels, plus a
sixth channel for bass effects.
In addition to multiple channels, the Dolby Digital track provides
extraordinary dynamic capability, wide frequency, range low distortion,
and relative immunity to wear and tear. The format has already proved
its unique combination of high quality, reliability, and practicality in
theaters around the world. And because the digital track is right on the
film, the format has none of the drawbacks of separate disc systems.
As with previous Dolby developments, Dolby Digital does not obsolete
existing theater installations. The prints can be played conventionally
in any theater, while the digital optical track can be reproduced by
adding digital readers to the projectors and a digital decoder which
interfaces with the theater’s existing Dolby cinema sound processor.
About Dolby AC-3
Conventional digital audio is coded by a technique called pulse code
modulation (PCM). As good as it sounds, however, PCM-coded audio
coded takes up so much more space than analog audio that it was
necessary to invent an entirely new medium, the Compact Disc, to bring
digital sound into the home.
It would be very difficult to provide even one channel of conventional
PCM digital audio on a movie print, let alone the 5.1 channels widely
regarded as ideal for proper cinema stereo. Yet for compatibility, ease
of distribution, economical release print manufacturing, and overall
cost-effectiveness, nothing beats the classic, on-film optical soundtrack.
Therefore, to make it possible to put a digital optical soundtrack on
release prints, Dolby Laboratories developed with a new, far more
efficient way to code digital audio, a technique which provides 5.1
channels of sound in less space than just one channel on a CD. This new
technique is called Dolby AC-3.
Just like the Dolby Surround technology developed originally for motion
picture sound, Dolby AC-3 can be used in a wide variety of other
applications, including consumer formats. For example, AC-3 will be
used to provide 5.1 channel surround sound with the U.S. HDTV system
and digital video discs. It is already being used on compatible Laser
Discs of movies, including many originally released in the Dolby Digital
format. Equipment for home Dolby AC-3 playback has come onto the
market as well.