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previous chapter: the Rise of the Dolby Empire |
next chapter: a word on THX |
Digital
Fluorescentsound was one of the first
attemps to add digital sound to movies. The digitally
encoded soundtrack was placed on top of the picture.
During normal projection the digital data was not visible
on the screen. When the film was scanned with ultraviolet
light, the track emitted a bright blue, visible, image
that was picked up by a reader that replaced the
penthouse for magnetic tracks. The gathered data was
processed into 6 analog audio signals, ready for
amplification. These signals had low or no distortion or
noise. Digital Fluorescentsound
was developed in 1981-'82 by Peter Custer and Dr. George
Bird. They also patented the system but it was never
really put into use.
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CDS (Cinema
Digital Sound) : In the late 1980's Eastman Kodak
Corporation joined forces with Optical Radiation
Corporation to develop what would become the first
commercially available digital sound format.
It was a sound-on-film system for
35mm and 70mm film formats with the digital information
placed between the sprockets and the film frame, thus
replacing the analog optical tracks on 35mm and the
magstripes on 70mm releases. CDS
featured 6 discrete audiochannels: 5 of them with full
bandwith (Left, Center, Right, Left and Right Surround)
and one low frequency only channel (LFE).
The compression technique used on CDS
was Delta Modulation, a variation of standard
16-bit PCM coding. Instead of recording every sample to a
0dB level as PCM does, Delta Modulation records
the difference in intensity between 2 successive samples.
This method needs less than the 16 bits needed for a PCM
sample and a compression ration of approximately 4:1
could be achieved without loss of information. The system
used Reed-Solomon burst error correction with cyclic
redundancy check character backup as an error correction
and detection strategy. Besides the digital audio track a
standard SMTP Time Code track was included to provide
synchronization between the sound and the picure and a
computer could control peripherals like lights and
curtains using the MIDI (Musical Instrument Digital
Interface) control channel.
Athough the system sounded great it quickly got the
reputation of being faulty. Back in 1990, when the system
was introduced, it was a pioneer in its field and LED and
CCD technology (see How does
digital sound-on-film work?) weren't as
developed as they are now. Printing the dense digital
track on the film proved to be a problem, too. As the
digital soundtrack wasn't reliable, prints degrade anyway
and hardware failures could occur, a second print, with
analog sound, had to be kept ready at all times.
CDS debuted in June 1990 on
70mm film prints with release of "Dick
Tracy" and in March 1991 on
35mm prints with "The
Doors". In July 1991 "Terminator
2: Judgement Day" was released with CDS
on both 70mm and 35mm; it was the sound system's
brightest moment. But distributors were reluctant to
release movies in CDS because
of its playback problems and the expensive system
couldn't convince theater owners enough. Also all
releases had to be available in standard analog optical
sound too as a back-up for the CDS
release and for theaters not equipped with the digital
system. Above that, Dolby Labs. announced in early 1991
their own digital format, Dolby
Stereo SR Digital, more than a year
before the actual release.
The last picture to feature a CDS
soundtrack was "Final
Approach" released in November
1991. The other movies released in CDS
were "Days of
Thunder" (6/1990, 70mm), "Flatliners" (10/1990, 70mm) and "Hudson
Hawk" (5/1991, 35mm). "For
the Boys" (11/1991) and "Universal
Soldier" (7/1992) were
announced to feature a CDS
soundtrack but the actual releases had analog ones.
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L.C.Concept was the
first digital
sound-on-disk system available.
The soundtrack was placed on 2 5"1/4 rewritable
magneto-optical disks manufactured by Sony. The 2 disks
were capable of storing 300MB of data each, equivalent to
90 minutes of soundtrack so the system could handle films
of maximum 3 hours. The sound-mix with 4 or 5.1 discrete
channels was compressed with the MUSICAM-algorithm
(Masking Pattern Universal Subband Integrated Coding and
Multiplexing). It was a variation on ISO/MPEG Layer
2 (MP2)lossy coding
algorithm and provided a 6:1
compression ratio. The standard SMPTE time-code track,
located on the analog soundtrack side of the film,
provided synchronization. In order to avoid the need to
restart the setting process each time the system was
transferred to a other theater, several settings could be
stored in the processor.
L.C.Concept, developed by
Frenchman Pascal Chedeville, was first demonstrated in
1991 with a experimental re-release of the 1990 film "Cyrano
de Bergerac". The first
commercial release was done in late 1991 with "Bis
ans Ende der Welt", only in France. In
1994 the system was modified for use with CD-ROMs instead
of magneto-optical disks but it was never put to use
commercially.
The system had no technical drawbacks (unlike CDS) but the
L.C.Concept company failed in 1994 mainly because of a
lack of financial strength caused by large companies not
supporting the system in anticipation of Dolby's
announced digital system in 1991.
Pascal Chedeville received in 1995 an Technical
Achievement Academy Award. In total some 20 theaters in
France, Switzerland and Belgium were equipped with the
system and about 30 films featured a L.C.Concept
soundtrack.
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Dolby Digital : In 1987 Dolby Labs. began to work on a proposal for a sound system for HDTV (High
Definition Television), the next generation TV
system. At first it was it intended to harbour on 2
channels but by using new and advanced encoding schemes,
it was possible to store up to 6 discrete channels of
audio. (5 of them full width and 1 for low frequencies
only). The 
system was named AC-3 (Audio Coder 3). Because HDTV
wouldn't become available for commercial use for several
years, Dolby Labs. used AC-3 for the development
of a digital cinema sound system with the now standard
5.1-channel configuration of Left, Center, Right channels
behind the screen, Left and Right Surround in the back of
the theatre and one low frequency only channel (LFE).
It was decided to create a digital sound-on-film format with the digital track
placed between 
the sprockets instead of replacing
the analog Dolby Stereo SR track, like CDS did. By keeping the analog track available the system had important advantages over CDS: the track could provide a back-up in case the digital system failed due to a
damaged digital track or hardware failure. By putting the digital track between the sprockets, it's better protected against damage. Because both a
digital and an analog track are located on one print,
there was also no need to keep a double inventory. The
format was compatible with all previous optical playback
equipment if exhibitors chose not to upgrade.
The system, originally designated Dolby
Stereo SR Digital (Dolby SR*D)
but now known as Dolby Digital,
was announced in early 1991 but the first movie to
feature the new format was "Batman Returns" in 1992. By now Dolby
Digital has become the de facto standard in
digital audio as most releases with a digital soundtrack
feature at least a Dolby SR*D
one because the system has some advantages over competing
formats DTS and SDDS.
The sound-on-film system is more convenient than DTS'
sound-on-disk and the reader and decoder are cheaper than
SDDS.
Dolby Digital Surround EX : Early 1999 Dolby and Lucasfilm THX announced a further development of Dolby Digital. An extra channel would be added
to the surrounds, thus
creating a 6.1-channel system. Gary Rydstrom, while
working on the sound mix for "Star Wars: Episode I - The
Phantom Menace", had proposed the new set-up because he
felt that an extra rear channel could provide a better
placement of effects sounds.
Dolby
Digital Surround EX's center
surround-channel was encoded in the existing 2 surround
channels by applying the same techniques as on with Dolby
Stereo. (see "How does Dolby's matrixed
sound work?")
By adding an adapter (and some additional wiring) any Dolby
Digital-theatre could be easily upgraded.
In the press release that announced the system it stated
that "Star
Wars: Episode I - The Phantom Menace" would be the first to feature a Surround
EX soundtrack and the hype surrounding the
film made sure the system was a success as many
exhibitors wanted to upgrade their installations. Dolby
Digital Surround EX soundtracks are usually
found only on big budget action packed movies, where
sound effects an important part of the experience are.
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DTS
Digital Sound & DTS-ES :
Under Construction !!
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SDDS, short for Sony Dynamic Digital Sound, is a digital sound-on-film system capable of
harbouring 
soundtracks
of up to 8 discrete channels. The digital track is locate
outside the sprockets on either side of the 35mm print. A
Dolby
Stereo SR-compatible analog
soundtrack is available in case the digital system fails.
The SDDS soundtrack is treated
with the ATRAC (Audio Transform Acoustic Coding)
lossy
encoding algorithm,
originally developed for MiniDisc which has a 5:1
compression ratio.
Because the soundtrack is located on the edges of a film
it is more susceptible to scratches and wear. Several
measures are taken to cope with the problems. First, the
soundtrack is recorded on the cyan layer of the film,
which is 3 layers down from the surface. All data is
stored redundant on both sides so that when the data is
corrupted on one side, the data on the other side is
processed. A 17 frame offset in recording time makes sure
that, when the film breaks, no data is lost. The ATRAC
also provides error correction and if everything else
fails there's still the analog stereo track.
The system is able to reproduce sound-mixes with 7.1, 5.1
or 4.0 discrete channels. The 7.1 setup has 5 screen channels
(Left, Left Center, Center, Right Center and Right), 2
surround channels and a subwoofer channel. The 5.1 setup
is the present standard for digital formats with 3 screen
channels, 2 surround channels and a LFE (Low Frequency
Effects) channel. 4.0 is the discrete version of the
matrixed Dolby
Stereo format and its
compatibles with 3 screen channels and mono surrounds.
Exhibitors can choose which of the 3 types they want to
install. If the soundtrack is a 7.1 mix and only a 5.1 or
4.0 system is installed, the processor mixes the 2 extra
channels (Left & Right Center) into the 3 available
ones. When a 8 channel system is installed but only a 5.1
or 4.0 mix is included, the processor distributes the 3
screen channels over the available 5.
SDDS premiered in 1994 with the
film "Last Action
Hero". Although the system
can handle 7.1 mixes most releases are done in the
standard 5.1 format. A SDDS-system
is more expensive to install than a DTS or a Dolby
Digital one and therefore it
has worldwide a lower screen penetration than the
competing formats. The format will stick arround, though,
as most major films feature soundmixes in all 3
dominating digital formats and all releases from the
Columbia Picture Studios have at least a SDDS
mix, as Columbia is a division of Sony.
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