Cinema Digital Sound (CDS) was a multi-channel
surround sound
Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener (surround channels). Its first application was in movie theaters. Prior to sur ...
format used for theatrical films in the early 1990s. The system was developed by
Eastman Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
and Optical Radiation Corporation. CDS was quickly superseded by
Digital Theatre Systems (DTS) and
Dolby Digital
Dolby Digital, originally synonymous with Dolby AC-3, is the name for what has now become a family of audio compression (data), audio compression technologies developed by Dolby Laboratories. Formerly named Dolby Stereo Digital until 1995 in film, ...
formats.
CDS replaced the analogue audio tracks on
35 mm and
70 mm film prints with 5.1 discrete audio. The 5.1 tracks were encoded using 16-bit PCM audio in a delta modulation compression which resulted in a compression level of 4:1. The
audio channel
An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals, or a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of ro ...
s in CDS were arranged in the same way that most current 5.1 systems with Left, Center, Right, Left Surround, Right Surround and
LFE. ''
Dick Tracy
''Dick Tracy'' is an American comic strip featuring Dick Tracy (character), Dick Tracy (originally Plainclothes Tracy), a tough and intelligent police detective created by Chester Gould. It made its debut on Sunday, October 4, 1931, in the ''De ...
'' (1990) was the first film encoded with CDS. Not all films with CDS soundtracks used all 5.1 channels; some, such as ''
Edward Scissorhands
''Edward Scissorhands'' is a 1990 American fantasy romance film directed by Tim Burton. It was produced by Burton and Denise Di Novi, written by Caroline Thompson from a story by her and Burton, and starring Johnny Depp, Winona Ryder, Anthony ...
'' (1990), used only the 4 channels that were supported by
Dolby Stereo
Dolby Stereo is a sound format made by Dolby Laboratories. It is a unified brand for two completely different basic systems: the Dolby SVA (stereo variable-area) 1976 system used with optical sound tracks on 35mm film, and Dolby Stereo 70mm nois ...
. ''
Universal Soldier'' (1992) was the last film encoded with CDS.
The digital information was printed on the film, similar to
Dolby Digital
Dolby Digital, originally synonymous with Dolby AC-3, is the name for what has now become a family of audio compression (data), audio compression technologies developed by Dolby Laboratories. Formerly named Dolby Stereo Digital until 1995 in film, ...
and
SDDS. However, unlike those formats, there was no analog optical backup in 35 mm and no magnetic backup in 70 mm, meaning that if the digital information were damaged in some way, there would be no sound at all. This was one of the factors that contributed to its inevitable demise; the then-new
Dolby Digital
Dolby Digital, originally synonymous with Dolby AC-3, is the name for what has now become a family of audio compression (data), audio compression technologies developed by Dolby Laboratories. Formerly named Dolby Stereo Digital until 1995 in film, ...
format moved its information to another area (in between the film sprocket holes), preserving the optical tracks.
Development and technical aspects
Prior to the development of Cinema Digital Sound, a six-track, optically read, sound-on-film system using PCM digital encoding was thought, by most in the industry, to be impractical. However, in a joint effort over a three-year period, and with a $5 million total investment, Kodak developed a special fine-grained, high-resolution negative film capable of holding more information than previous films and Optical Radiation Corporation developed a special audio coding and error correction system, resulting in the Cinema Digital Sound system.
Initial tests proved that packing densities necessary to achieve high-fidelity digital sound and error rates comparable to the Compact Disc format were possible using Kodak's new high-resolution negative film and that wear on the film during normal playback was not significant. In a controversial move (ORC's engineers fought against it but management overruled them), it was decided to utilize the area typically reserved for sound in the 35 mm optical and 70 mm magnetic film standards, for the new CDS digital audio and data tracks. Six audio channels were implemented; Five full-bandwidth audio channels (three behind screen and two surround channels) were applied to the input of the system as linear 16-bit samples at a 44.1 kHz sample rate. Samples were data compressed into 12-bit words via Delta-Modulation, with one in every 32 samples retaining its original linear 16-bit form to provide an accurate reference every 726μm. The subwoofer (.1 Low Frequency Effects) channel did not employ Delta-Modulation. Instead the 44.1 kHz sample rate was decreased to 1378 Hz, which yielded an upper audio bandwidth of 114 Hz with anti-aliasing and anti-imaging strategies applied in the remainder of the frequency range.
In addition to the six digital audio channels, three data/control channels were provided. One SMPTE time code channel and another channel for MIDI control signals offered flexibility for performing theater automation or external synchronization of equipment. The third data channel, an identification track, could be used to record a variety of user-defined parameters specific to the film (such as curtain opening/closing, seat movement or lighting effects.) In view of the fact that the CDS system was available for only two years before its complete withdrawal from the market, no use of the SMPTE time code or MIDI channels was ever implemented.
Because the data rate was 5.8 million bits-per-second (5.8mbp/s), significant error detection and correction was required. A custom designed Reed-Solomon block code, was used with additional CRC characters for error correction. Interleaving of odd and even audio samples was performed to protect against burst errors. Just as in audio tape machines, transport problems with tension, guides, and supply and take-up reels could result in vertical or horizontal weave, and as bit sizes were only 14μm, precise timing and tracking was essential, thus the CDS system required installation of special projector modifications to smooth the film path travel and steady the take-up speed. It was found later, however, that modifications to the projectors were not needed and that the CDS systems sensitivity to improper film speed was due to a diode installed incorrectly in the CDS decoder module. Horizontal tracking was provided by a 76-MHz digital servo, while vertical timing was accomplished with an algorithm written into the data format itself. Rows of data were scanned horizontally, thus a self-clocking run-length-limited code was used for this error correction. A 6-to-8-bit mapping was performed upon encoding to ensure that each 8-bit word contained exactly four ones. This form of parity worked well in correcting errors upon decoding.
Films distributed with CDS
*''
Dick Tracy
''Dick Tracy'' is an American comic strip featuring Dick Tracy (character), Dick Tracy (originally Plainclothes Tracy), a tough and intelligent police detective created by Chester Gould. It made its debut on Sunday, October 4, 1931, in the ''De ...
'' (1990) (
Buena Vista Pictures
Walt Disney Studios Motion Pictures, formerly known as Buena Vista Pictures Distribution, Inc. until 2007, is an American film distribution studio within the Disney Media and Entertainment Distribution division of The Walt Disney Company. It ha ...
)
*''
Days of Thunder
''Days of Thunder'' is a 1990 American sports action drama film released by Paramount Pictures, produced by Don Simpson and Jerry Bruckheimer and directed by Tony Scott. The cast includes Tom Cruise, Nicole Kidman, Robert Duvall, Randy Qua ...
'' (1990) (
Paramount Pictures
Paramount Pictures Corporation is an American film and television production company, production and Distribution (marketing), distribution company and the main namesake division of Paramount Global (formerly ViacomCBS). It is the fifth-oldes ...
)
*''
Flatliners
''Flatliners'' is a 1990 American psychological horror film directed by Joel Schumacher, produced by Michael Douglas and Rick Bieber, and written by Peter Filardi. It stars Kiefer Sutherland, Julia Roberts, William Baldwin, Oliver Platt, a ...
'' (1990) (
Columbia Pictures
Columbia Pictures Industries, Inc. is an American film production studio that is a member of the Sony Pictures Motion Picture Group, a division of Sony Pictures Entertainment, which is one of the Big Five studios and a subsidiary of the multi ...
)
*''
Edward Scissorhands
''Edward Scissorhands'' is a 1990 American fantasy romance film directed by Tim Burton. It was produced by Burton and Denise Di Novi, written by Caroline Thompson from a story by her and Burton, and starring Johnny Depp, Winona Ryder, Anthony ...
'' (1990) (
20th Century Fox
20th Century Studios, Inc. (previously known as 20th Century Fox) is an American film studio, film production company headquartered at the Fox Studio Lot in the Century City area of Los Angeles. As of 2019, it serves as a film production arm o ...
)
*''
The Doors
The Doors were an American rock band formed in Los Angeles in 1965, with vocalist Jim Morrison, keyboardist Ray Manzarek, guitarist Robby Krieger, and drummer John Densmore. They were among the most controversial and influential rock acts ...
'' (1991) (
Carolco Pictures
Carolco Pictures, Inc. was an American independent film studio that existed from 1976 to 1995, founded by Mario Kassar and Andrew G. Vajna. Kassar and Vajna ran Carolco together until 1989, when Vajna left to form Cinergi Pictures. Carolco hit ...
)
*''
Hudson Hawk
''Hudson Hawk'' is a 1991 American action comedy film directed by Michael Lehmann. Bruce Willis stars in the title role and also co-wrote both the story and the theme song. Danny Aiello, Andie MacDowell, James Coburn, David Caruso, Lorraine T ...
'' (1991) (
TriStar Pictures
TriStar Pictures, Inc. (spelled as Tri-Star until 1991) is an American film studio and production company that is a member of the Sony Pictures Motion Picture Group, part of the multinational conglomerate Sony. It is a corporate sibling of Sony ...
)
*''
Terminator 2: Judgment Day'' (1991) (Carolco)
* ''
For the Boys'' (1991) (20th Century Fox)
*''
Final Approach
In aeronautics, the final approach (also called the final leg and final approach leg) is the last leg in an aircraft's approach to landing, when the aircraft is lined up with the runway and descending for landing.Crane, Dale: ''Dictionary of ...
'' (1991) (
Trimark Pictures
Trimark Pictures was an American production company that specialized in the production and distribution of television and home video motion pictures. The company was formed in 1984 by Mark Amin as Vidmark Entertainment with Vidmark Inc. (later ...
)
*''
Universal Soldier'' (1992) (Carolco)
External links
Web-converted version of original CDS brochure
{{Audio formats
Audiovisual introductions in 1990
Film sound production
Surround sound
Kodak
Development organizations