Panasonic EURO 4 Chassis Technical Manual page 67

21. History Of Dolby Pro
21.1. General
For over a decade from Star Wars to Dance with
Wolves, Dolby Stereo has delighted cinema
audiences with multi-dimensional sound.
Dolby Stereo goes beyond mere two channel stereo,
so in addition to the left and right audio channels a
centre channel and rear channel are used.
The centre channel is used to sharpen sound
perspective and dialogue clarity while the rear
channel is used to immerse the audience in ambience
and special effects.
The difference between Dolby Stereo and Dolby
Surround is that Dolby Stereo refers to movies shown
at cinemas using equipment made by Dolby
laboratories. While Dolby Surround refers to the term
used with consumer entertainment equipment.
Dolby laboratories does not manufacture Dolby
Surround decoders for home use. Instead the
technology is licensed to manufacturers of consumer
electronic equipment.
This technology is now being incorporated in products
ranging from surround decoders to stereo TV sets.
When Dolby Stereo sound-track are made, four
channels of sound are combined into two audio tracks
like conventional stereo. When movies are copied
onto video tape, the encoded sound tracks are also
copied.
If you want to play-back Dolby Surround sound and
you already have a stereo amplifier and speakers the
main piece of equipment needed is the Dolby
Surround decoder, plus some additional speakers for
the surround sound.
There are however two types of Dolby Surround
Decoders. The Dolby Surround and Dolby Pro
Decoders, the goals of both these decoders however
are identical. The main difference between the two
decoders being Dolby Surround decoders do not use
a centre channel and are referred to as passive
decoders. With this type of decoder only the Front left
and right and surround channels are used.
.
The Pro Logic decoders however, which are referred
.
Logic
.
Logic
67
to as active decoders, uses a centre channel as well
as the front left, right and surround channels.
This means that the Dolby Pro
generates clearer positioning of sounds and provides
a full effect over a wider area of listening room. This,
together with built in electronically assisted set up,
.
makes Pro Logic easier to use.
As well as the many film titles already available on
video, there are now an increasing number of
programmes being produced for television in Dolby
Surround. These range from sports, dramas, talk
show programmes and now even commercials.
One of the main reasons why Dolby Surround video
and television programs are becoming more popular
is because it provides an additional dimension over
conventional stereo productions, by using a Dolby
Matrix encoder which combines four channels of
audio information onto the standard two channel
format, thus making it suitable for recording or
transmitting as regular stereo programs using the
already existing formats so widely available
One of the original goals of the Dolby encoder was to
enable Dolby Stereo sound-tracks to be successfully
played in cinemas equipped for mono or two channel
stereo sound. This allowed movies to be distributed
on a single format, which also resulted in complete
compatibility with home video media without requiring
separate sound-track mixes. Since the three front
channels of the encoder matrix are assembled in
virtually the same way as conventional stereo mixes,
with left into left, centre equally into left and right, and
right into right.
Playing a Dolby Stereo sound-track over two
speakers reproduces
sound-track. However there is one exception the
Surround signal, though audible it is not reproduced
in its proper spartial perspective. However with the
advent of the first home decoder which was
developed in 1982, its goal to restore this lone missing
dimension was realised.
3DQDVRQLF
.
Logic decoder
the entire encoded