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The projection of motion pictures is still based on technological principles that have remained essentially unchanged for the entire first century of cinema history. Even today, the most advanced projectors still rely on the 19th century medium of film, with sprocket holes for a
steady rate of projection at 24 frames per second; a powerful source of light to throw the magical light and shadow of the moving image; and a properly focused lens to maintain the clarity with which those images were originally photographed. Until digital technologies can create an image as large, bright and crisp as the projected motion picture, the images we see will not be as technically advanced as the sounds we hear in cinemas around the world. Indeed, the digital revolution has resulted in a constant, shifting improvement of theatrical sound systems since the mid-1970's. By the mid-1990's, theatres incorporating the most advanced digital sound systems had effectively restored the grandiose
experience of filmgoing, matching bright, crisp wide-screen images with multi-channelled stereo sound of astonishing dimension and clarity, virtually surrounding the audience in a carefully recorded, mixed, and amplified environment of sonic entertainment. And while many of these
advances were also applied to the improvement of home-theatre sound systems (which often exceed sub-standard theatres in overall quality), the 1990's introduced new and improved theatrical sound systems to ensure the continuing appeal of watching movies in public, with an audience, under the optimum conditions of grand-scale exhibition.
The following is a survey of sound systems and formats currently used in theatres around the world:

The first Cinerama film was This Is Cinerama in 1952.  In Cinerama, a magnetic sound filmstrip which contained 7 soundtracks, as well as the three picture film strips were all on separate pieces of 35mm film and all had to be interlocked to each other.  If any one element went out of synchronization, everything had to be stopped, appropriate frames for all for filmstrips had to be found and re-started again from a single, in-sync starting point.  The system even had a fifth, standard "non-sync" projector located in the center booth which was always on stand-by with a 15 min short that explained the complexities of the Cinerama process. This film could be run during a breakdown to pacify the audience....it was needed more than the designers, theatre owners or patrons would have liked.

The first Cinerama film was This Is Cinerama 1952

Widescreen is a very complex subject.  It all started when television became popular in the 1950s and Hollywood needed to bring moviegoers back to the cinemas.  They made their films look different than the television screen.  The first widescreen film was This Is Cinerama in 1952 with a huge screen curved at an angle of 165 degrees.  How The West Was Won, released in 1962, was the first feature film in Cinerama with an Aspect Ratio of 2.66:1. which is three times as wide as it is high, but how would this look on a regular television set?

Whenever movie industry people talk about CinemaScope, a wide screen process that produces an image two-and-a-half times as wide as it is high, they usually expound on the fact that Hollywood was motivated by fear of the new upstart rival television.  They contend that the studios had to find a presentation so much more spectacular so as to entice audiences out of their living rooms and back into theatre seats. There is some truth in this -- by the mid-fifties Hollywood was becoming quite paranoid by the threat of the fast-growing new free entertainment medium. They saw theatre attendance drop dramatically as the small magic box with its ghostly blue flickering image ferreted its way into more and more American living rooms. But that is only a half-truth. The fact is, that in 1951 the Cinerama company launched a spectacular wide screen process that so captured the public's imagination that the rest of Hollywood began running catch-up to get onto the wide-screen bandwagon.  It was was the fantastic success of Cinerama that motivated the major studios to find a way to mimic the wide-screen presentation that Cinerama provided.  The fact that such intense visual and sonic presentation would blow

In 1953 The Robe was released with Stereophonic magnetic sound

1955, and the introduction of the Todd-AO 70mm process with 6 track magnetic sound,  two magnetic tracks recorded on the left and right sides of the film outside the sprocket holes and one track each was recorded on either side of the image inside the sprocket holes.

Okalahoma released in 1955 was the first film with six track magnetic sound

http://www.rci.rutgers.edu/~dmorton/mag_rec_chrono.htm

Dolby Stereo: Although the advent of magnetic sound tracks improved the quality of film sound in the 1950's, it was often available only in the best-equipped theatres playing the most prestigious films, and the cost of magnetic-sound film prints was prohibitively high. By the
mid-1970's, most theatres were still showing films with low-fidelity, monophonic optical soundtracks. Developed by Dolby Laboratories, Dolby Stereo was a highly practical 35mm stereo optical release print format, replacing the conventional mono optical soundtrack (located in the
space between the filmed image and the sprocket holes) with two optical tracks, one track for carrying sound information for left- and right-channel sound, and the other for centre-screen channel sound and a then-unprecedented fourth channel for ambient sound and special effects.
(It was Dolby Stereo - with its advanced Dolby "A-type" noise reduction and equalization technology - that dazzled audiences during the 1977 release of STAR WARS and other major releases of the time, including 70mm prints using magnetic stereo sound.)

In 1976, A Star Is Born became the first Dolby Stereo film

Stereo Analogue Dolby A Track

http://www.dolby.com/

Dolby SR ("Spectral Recording"): Introduced in 1986, Dolby SR is, like Dolby noise reduction, a system used both when a soundtrack is recorded and when it is played back. Providing more than twice the noise reduction of Dolby "A-type," the SR system also permits the capturing of louder sounds with wider frequency response and lower distortion. The sound quality is superior in theatres equipped with Dolby SR processors, but films with SR optical soundtracks can be satisfactorily played in any theatre (a flexible condition known in the industry as "single
inventory," referring to film prints that can be played on all existing systems). Dolby Digital: This format puts a six-channel digital optical soundtrack—in addition to the four-channel Dolby SR analogue track—directly onto the same 35mm film prints, offering independent
left, centre, right, left surround, and right surround channels, in addition to a sixth channel for bass effects. Physically located in recorded blocks between the film print's sprocket holes, the Dolby Digital soundtrack provided considerable improvements in dynamic capability, frequency
range, low distortion and relative immunity to wear. With their analogue tracks as a back-up, Dolby Digital prints can play conventionally in any theatre, while the digital track can be reproduced by adding digital readers to the projectors, and a digital decoder which interfaces with the
theatre's existing Dolby cinema sound processor. First developed for theatrical sound, Dolby Digital is also used in home-theatre viewing formats such as laserdiscs and Digital Video Discs (DVD).

Robocop became the first Dolby SR Stereo film in 1987

Stereo Analogue Dolby SR Track

Cinema Digital Sound was the first digital sound format developed in a joint venture between Eastman Kodak and the Optical Radiation Corporation.  The CDS system encoded 5.1 channels of discrete audio and had a  typical set up of Left, Centre, Right, Right Surround, Left Surround, LFE channel format. CDS encoded 16-bit PCM audio in a compression process called Delta Modulation similar to normal PCM coding but with one major difference. PCM coding records the intensity of every sample to a zero db level. That requires 16-bits for each sample. Delta Modulation records the intensity differences of successive samples, and that doesn't require nearly as much data. The compression level of CDS ran approximately 4:1. The system sounded very good. Some sound designers have argued CDS sounded better than any of the current formats. For all that high quality audio a lot of data had to be put down on the film print in the form of very tiny spots.

The CDS digital data replaced the magnetic tracks on 70mm prints and the SVA tracks on 35mm prints. Of course, this meant CDS had no audio backup in case the digital system failed. It also meant theatre operators had to carry dual inventory prints in case of a hardware component failure or seriously degraded soundtrack. Failures did happen. The LED and CCD video technology was not at the level it is today for imaging more than 1 million printed spots per second. Film printing technology was also a good bit more primitive in 1990. The fatal flaw in CDS was the lack of an analogue backup soundtrack.

Cinema Digital Sound had a short history, but one that scored a number of film firsts. CDS was the first to encode digital sound on a 70mm release print. CDS was the first to put digital sound on 35mm with "The Doors", released March 1, 1991. "Hudson Hawk" was the first film to put six track audio into theatres without any 70mm release prints. CDS was the first digital system used on a Best Sound/Best Sound Effects Editing Oscar winning film, "Terminator 2: Judgement Day". T2 was also the first box office champ of the year to use digital sound release prints. T2 also remains the only film to have both 70mm and 35mm digital sound prints in its original release. DTS is the only current active format that supports 70mm film, but the 70mm system has so far only been used on film restorations and special venue films. Finally, CDS was the release format used on "Final Approach," the first film with 100% of its audio digitally recorded.

When CDS launched their 35mm system they were hit with two problems. The 35mm system ran into reliability problems. To make matters much worse, Dolby introduced the other problem with their February 1991 announcement of Dolby Stereo Digital, a full sixteen months before the format was actually released. Distributors held off CDS releases because of the playback problems. Movie theatre operators looked at the $20,000 price tag along with the system's problems and then thought long and hard about the vaporware Dolby was selling.

"Terminator 2" was CDS's brightest moment, but after that everything fell apart. "Final Approach" was the last actual CDS release. "For the Boys" and "Universal Soldier" were both announced as CDS releases, but CDS prints never made it into the theatres. Dolby Digital debuted one week before "Universal Soldier" on the release of "Batman Returns". . At the same time, DTS and SDDS were getting ready to appear.

The CDS ultimately failed in 1900 with the release of Final Approach, Eastman Kodak and ORC abandoned the CDS effort and sold off assets in April of 1993. although the format did pioneer motion picture digital sound. and provided valuable experience for DTS, Dolby, and Sony systems.

Dick Tracy was the first film released in CDS (1990)

CDS Track

http://www.kodak.com/US/en/motion/digital/system.shtml

First introduced to moviegoers in 1992 with Batman Returns, and heard on almost a thousand films around the world since then, Dolby Digital is the latest sound innovation from Dolby Laboratories.

Dolby revolutionized tape recording in the late 1960s and early 1970s with Dolby A-type (for professional applications) and Dolby B-type (for consumer applications) noise reduction. Later in the 1970s Dolby revolutionized film sound with the Dolby Stereo analogue sound system. Dolby Stereo brought 4 channel sound to the movie theatre with three channels of sound in the front (left and right for music and effects and centre for dialog) and a surround channel for effects and atmospheres. Then in the 1980s both tape recording and film sound saw significant improvements through the use of Dolby SR ("Spectral Recording").

Dolby also revolutionized home entertainment in the late 1980s and early 1990s with the Dolby Surround and later Dolby Pro Logic home theatre systems (basically using the Dolby Stereo technology in the home environment for video tapes and laser discs). This allowed home viewers to create the same 4 channel theatre-type setup in the home.

Today's Dolby Digital system takes the next step, providing six channels of crystal clear digital surround sound. Left, centre and right channels in front of you provide precise, clear positioning of dialogue. Separate or "discrete" left and right surround channels on the side and in the rear immerse you in the film with atmospherics and ambient sounds. And a subwoofer/bass effects channel contributes extra punch to action and special effects sequences.

The principles of Dolby Digital follow from the analogue noise reduction work that Dolby has been engaged in for more than 30 years. Dolby noise reduction works by lowering the noise when no audio signal is present, while allowing strong audio signals to cover or mask the noise at other times. Thus it takes advantage of the psycho acoustic phenomenon known as auditory masking. Even when audio signals are present in some parts of the spectrum, Dolby noise reduction reduces the noise in the other parts so the noise remains imperceptible. This is because audio signals can only mask noise that occurs at nearby frequencies.

When moving from analogue recording to a digital recording medium like the compact disc, one finds that the digital audio coding used on CDs yields an amount of data often too immense to store or transmit economically, especially when multiple channels are required. As a result, new forms of digital audio coding - often known as "perceptual coding" - have been developed to allow the use of lower data rates with a minimum of perceived degradation of sound quality. Dolby's third generation audio coding algorithm (AC-3) is such a coder.

This coder has been designed to take maximum advantage of human auditory masking in that it divides the audio spectrum of each channel into narrow frequency bands of different sizes optimized with respect to the frequency selectivity of human hearing. This makes it possible to sharply filter coding noise so that it is forced to stay very close in frequency to the frequency components of the audio signal being coded. By reducing or eliminating coding noise wherever there are no audio signals to mask it, the sound quality of the original signal can be subjectively preserved. In this key respect, a coding system like AC-3 is essentially a form of very selective and powerful noise reduction.

Indeed, Dolby Laboratories' unique experience with audio noise reduction is essential to AC-3's effective data rate reduction: the fewer the bits used to describe an audio signal, the greater the noise.

In the film industry, the Dolby Digital soundtrack is optically encoded right on the filmstrip, in the space between the sprocket holes. Having the soundtrack directly on the film allows it to coexist with the analogue track without involving any other media like a CD - this not only makes it simple for film distributors and theatre owners to handle, but also allows Dolby Digital prints to be prepared at virtually no additional cost. The sprocket hole area has also proven highly resistant to wear and tear, so that a Dolby Digital soundtrack will remain free of pops and hiss for the useful life of the print.

In the consumer electronics industry the Dolby Digital soundtrack can be found on the latest generation of laser discs (in space where one of the analogue tracks used to be), can be found as the standard audio track on Digital Versatile Discs (DVD), is the standard audio format for High Definition Television (HDTV), and is being used for digital cable and satellite transmissions.

Batman Returns was the first Dolby Digital film (1992)

Dolby Digital Track

http://www.dolby.com/digital/

SDDS, Sony Dynamic Digital Sound  was introduced in 1993.  SDDS is a sound-on-film system in which the digital information is printed on both edges of the 35mm film, this allows a greater amount of digital data storage space, and avoiding the need for separate
CD-ROM soundtracks and synchronization codes. Like other digital systems, SDDS technology is used in both recording and playback of film soundtracks. For playback, an SDDS digital decoding system is added for processing through the existing theatre sound system, and an SDDS "reader" unit is mounted to the projector to read the digital information from the film. Capable of delivering eight discrete channels of digital sound, the SDDS data is recorded on the cyan layer of the film print, three emulsion layers below the film's surface, to protect the
digital tracks from scratches and wear. To ensure error-free replay, each side of the film contains the back-up information for the track on the opposite side of the film, so that any damage on one side is automatically corrected by the back-up data recorded on the opposite side.
In the event of a splice or film break across the entire width of the film, the digital data on opposite sides is off-set by about 17 frames so properly synchronized sound can be maintained (via the projector's digital "reader") without noticeable reversions to the standard  Analogue soundtrack, which serves as a last-resort back-up when both sides of the film have suffered sustained damage.

In 1993 The Last Action Hero was the first Sony SDDS film

SDDS Track

http://www.sdds.com/

1993 also saw the introduction of DTS Digital Sound, Developed by Digital Theatre Systems, Inc. in California.   DTS Digital Sound was designed to create full-range digital sound reproduction using a theatre's existing sound system, DTS utilizes a digital soundtrack recorded not on the film itself, but on two separate CD-ROM discs capable of holding a combined total of three and a half hours of digital sound. Using an optical time-code track printed on the film print itself, the DTS system controls the operation of a separate CD-ROM player, which processes up to six channels of digital sound. (Specially equipped theatres can use the DTS system to process eight or more channels.) The time-code automatically synchronizes with the CD-ROM to match the correct sound with each frame of the film projected.  It involves synchronizing a CD-ROM with the film by using an optical Timecode Track between the picture and the optical analogue soundtrack

Jurassic Park in 1993 was the first DTS Film

DTS Timecode Track

http://www.dts.com/

35mm Film today has four sound tracks, Dolby Optical Stereo, Dolby Digital, DTS, and SDDS.

Today, film credits show the three major sound tracks.  SDDS, Dolby Digital and DTS