Cinema Digital Sound
Encyclopedia
Cinema Digital Sound is a multi-channel surround sound
format used for theatrical films in the early 1990s. The system was developed by Eastman Kodak
and Optical Radiation Corporation
. CDS was quickly superseded by Digital Theatre System (DTS) and Dolby Digital
formats.
CDS format replaced the analogue audio tracks on 35mm and 70mm 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 channels in CDS were arranged in the same way that most current 5.1 systems with Left, Center, Right, Left Surround, Right Surround and LFE. Not all films with CDS soundtracks used all 5.1 channels with some, such as Edward Scissorhands
, using only the 4 channels that were supported by Dolby Stereo
. Universal Soldier
was the last film encoded with CDS.
The digital information was printed on the film, similar to Dolby Digital
and SDDS
. However, unlike those formats, there was no analog optical backup in 35mm and no magnetic backup in 70mm, 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
format moved its information to another area (in between the film sprocket holes), preserving the optical tracks.
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 dollar 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 35mm optical and 70mm 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 726ųm. 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 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 14ųm, 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 one’s. This form of parity worked well in correcting errors upon decoding.
Surround sound
Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...
format used for theatrical films in the early 1990s. The system was developed by Eastman Kodak
Eastman Kodak
Eastman Kodak Company is a multinational imaging and photographic equipment, materials and services company headquarted in Rochester, New York, United States. It was founded by George Eastman in 1892....
and Optical Radiation Corporation
Optical Radiation Corporation
Optical Radiation Corporation is an American company that produces a range of UV exposure systems used in the manufacture of PCBs. ORC was founded in 1969 to design and manufacture optoelectronic and optical products....
. CDS was quickly superseded by Digital Theatre System (DTS) and Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
formats.
CDS format replaced the analogue audio tracks on 35mm and 70mm 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 channels in CDS were arranged in the same way that most current 5.1 systems with Left, Center, Right, Left Surround, Right Surround and LFE. Not all films with CDS soundtracks used all 5.1 channels with some, such as Edward Scissorhands
Edward Scissorhands
Edward Scissorhands is a 1990 romantic fantasy film directed by Tim Burton and starring Johnny Depp. The film shows the story of an artificial man named Edward, an unfinished creation, who has scissors for hands. Edward is taken in by a suburban family and falls in love with their teenage daughter...
, using only the 4 channels that were supported by Dolby Stereo
Dolby Stereo
Dolby Stereo, is the trade mark that Dolby Laboratories used for the various analogue stereo cinema sound formats that they produced.Two basic systems used this name. The first was the 'Dolby SVA' system used with optical soundtracks on 35mm film...
. Universal Soldier
Universal Soldier (1992 film)
Universal Soldier is a 1992 American science fiction action film directed by Roland Emmerich and starring Jean-Claude Van Damme and Dolph Lundgren as soldiers who kill each other in Vietnam but are reanimated in a secret Army project along with a large group of other previously dead...
was the last film encoded with CDS.
The digital information was printed on the film, similar to Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
and SDDS
SDDS
Sony Dynamic Digital Sound is a cinema sound system developed by Sony. Compressed digital sound information is recorded on both outer edges of the 35 mm film release print. The system supports up to eight independent channels of sound: five front channels, two surround channels and a single...
. However, unlike those formats, there was no analog optical backup in 35mm and no magnetic backup in 70mm, 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
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
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 encodingwas thought, by most in the industry, to be impractical. However, in a joint effort over a three year period, and with a
$5 million dollar 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 35mm optical and 70mm 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 726ųm. 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 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 14ųm, 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 one’s. This form of parity worked well in correcting errors upon decoding.
Films distributed with CDS
- Days of ThunderDays of ThunderDays of Thunder is a 1990 American auto racing 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 Quaid, Cary Elwes and Michael Rooker. The film also features appearances...
- Dick Tracy
- Edward ScissorhandsEdward ScissorhandsEdward Scissorhands is a 1990 romantic fantasy film directed by Tim Burton and starring Johnny Depp. The film shows the story of an artificial man named Edward, an unfinished creation, who has scissors for hands. Edward is taken in by a suburban family and falls in love with their teenage daughter...
- Final Approach
- FlatlinersFlatlinersFlatliners is a 1990 American thriller film starring Kiefer Sutherland, Julia Roberts, Kevin Bacon, William Baldwin and Oliver Platt as medical students using physical science in an attempt to find out if there's anything out there beyond death by conducting clandestine experiments with near-death...
- Hudson HawkHudson HawkHudson Hawk is a 1991 American action comedy film directed by Michael Lehmann. Bruce Willis stars in the title role and also co-wrote the story. Danny Aiello, Andie MacDowell, James Coburn, David Caruso, Lorraine Toussaint, Frank Stallone, Sandra Bernhard, and Richard E...
- Terminator 2: Judgment DayTerminator 2: Judgment DayTerminator 2: Judgment Day is a 1991 science fiction action film directed by James Cameron and written by Cameron and William Wisher Jr.. It stars Arnold Schwarzenegger, Linda Hamilton, Robert Patrick, and Edward Furlong...
- The DoorsThe Doors (film)The Doors is a 1991 biopic about the 1960s-1970s rock band of the same name which emphasizes the life of its lead singer, Jim Morrison. It was directed by Oliver Stone, and stars Val Kilmer as Morrison, Meg Ryan as Pamela Courson , Kyle MacLachlan as Ray Manzarek, Frank Whaley as Robby Krieger,...
- Universal SoldierUniversal Soldier (1992 film)Universal Soldier is a 1992 American science fiction action film directed by Roland Emmerich and starring Jean-Claude Van Damme and Dolph Lundgren as soldiers who kill each other in Vietnam but are reanimated in a secret Army project along with a large group of other previously dead...