Sony Dynamic Digital Sound
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is a cinema
sound In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...
system developed by
Sony is a Japanese multinational conglomerate (company), conglomerate headquartered at Sony City in Minato, Tokyo, Japan. The Sony Group encompasses various businesses, including Sony Corporation (electronics), Sony Semiconductor Solutions (i ...
, in which compressed digital sound information is recorded on both outer edges of the 35mm film release print. The system supports up to eight independent channels of sound: five front channels, two surround channels and a single sub-bass channel. The eight channel arrangement is similar to large format film magnetic sound formats such as Cinerama and Cinemiracle. The five front channels are useful for very large cinema auditoriums where the angular distance between center and left/right channels may be considerable. SDDS decoders provide the ability to downmix to fewer channels if required.


History

Although originally slated to premiere with 1991's ''
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'', the SDDS project was delayed and instead premiered on April 2, 1992. and on June 17, 1993 premiered it First Film
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. Since then, over 2000 movies have been mixed and remastered in Sony Dynamic Digital Sound, and as early as 1999 over 6,750 movie theaters were equipped with SDDS. The code name for the SDDS project was "Green Lantern", taken from the name of the comic book hero and the old term of "
magic lantern The magic lantern, also known by its Latin name , is an early type of image projector that uses pictures—paintings, prints, or photographs—on transparent plates (usually made of glass), one or more lens (optics), lenses, and a light source. ...
" used to describe the original projected pictures in the late 19th century. Green came to mind because the key to imprinting the 8
micrometre The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a uni ...
data bits was to use a green laser. Initial development efforts were conducted for Sony's
Columbia Pictures Columbia Pictures Industries, Inc., Trade name, doing business as Columbia Pictures, is an American film Production company, production and Film distributor, distribution company that is the flagship unit of the Sony Pictures Motion Picture Group ...
Sound Department under contract with Semetex Corp. of
Torrance, California Torrance is a coastal city in the Los Angeles metropolitan area located in southwestern Los Angeles County, California, United States. The city is part of what is known as the South Bay (Los Angeles County), South Bay region of the metropolitan ...
. At Semetex, the SDDS Chief Architect was Jaye Waas and the Chief Optical Engineer was Mark Waring. The Semetex prototype design actually had the eight channels of uncompressed data placed into three locations: data bordering both sides of the analog sound track and additional data tracks bordering the opposite edge of the picture frame. These locations were chosen to ensure the data were not placed into the sprocket perforation area of the film to prevent the known wear and degradation that occurs in the perforation area (due to the mechanical film sprockets) from degrading the data. Clocking and guide tracks were placed on each side of the film near the sprockets. The prototype sound camera imprinted the Digital audio and Analog audio 'at speed'. A companion digital reader was designed to form a complete system. After Sony received the prototype they enlarged the data bits from the original 8 micron (micrometer) size and moved the data locations; the eight digital audio channels are now recorded on (and recovered from) the edges of the film. As Sony engineers became more actively involved in the project, the design of the SDDS format evolved toward a more robust implementation, including the use of 5:1
ATRAC Adaptive Transform Acoustic Coding (ATRAC) is a family of proprietary audio compression algorithms developed by Sony. MiniDisc was the first commercial product to incorporate ATRAC, in 1992. ATRAC allowed a relatively small disc like MiniDisc t ...
data compression, extensive error detection and correction, and most critically redundancy. The redundancy allows data to be recovered substantially intact even in the presence of a film splice (common for repairing damaged film). The data bit size on film was enlarged from 8 micron (micrometer) to 24 micrometers square, and Semetex's green laser system for the sound camera was replaced with simpler LED/fiber optic assemblies which limited resolving to 24 micrometers. Using data compression allowed 24 micrometers square data bits to fit within the newly allocated areas. The SDDS development at Semetex took just 11 months from concept to working sound camera. When it came time for deployment, since Sony also owned the Sony Theaters chain (later sold to
Loews Theaters Loews Cineplex Entertainment, also known as Loews Incorporated, was an American theater chain operating in North America. The company was originally named "Loew's" after its founder Marcus Loew. In 1969, when the Tisch brothers acquired the com ...
), it was able to use SDDS in its own theaters. And via its highly successful Columbia/TriStar Studios arm, it was able to use SDDS as the exclusive digital soundtrack on its titles. In addition, in the early days of the "megaplex explosion", Sony struck a deal with
AMC Theatres AMC Entertainment Holdings, Inc. (doing business as AMC Theatres, originally an abbreviation for American Multi-Cinema; often referred to simply as AMC) is an American movie theater chain founded in Kansas City, Missouri, and now headquartered ...
in 1994 to include SDDS in all of their new auditoriums. This gave SDDS a much needed, kick-start. More than likely it would have garnered far less penetration had Sony not controlled both a theater chain and a film studio. SDDS was consistently the least popular of the three competing digital sound formats, the other two being Spectral Recording Dolby Stereo Digital and DTS. Along with being the most expensive to install (and the last to arrive), there were major reliability issues with SDDS due to the change from the prototype sound track placement to the very edges of the film stock where the film is subject to damage. SDDS tracks are prone to damage as are some other digital formats. With all the digital sound formats: any failure of the digital track could result in a "drop-out" of the digital format and possibly a switch to analog sound. Additionally a drop-out resulting in a switch to Analog (Analogue) may produce a slight loss of fidelity and high and low-ends, although it is more difficult to tell in a properly calibrated auditorium. SDDS's much-touted eight track playback capability never quite caught on, as it required that a separate eight channel sound mix be created in addition to the six channel mix that is needed for SRD and DTS, an additional expense for the studios. Out of the 1,400 plus films mixed in SDDS, only 97 of them to date have been mixed to support the full 8 channels, most of them Sony (Via Sony Pictures/Columbia/TriStar) releases. Because of the added installation expense, the majority of SDDS installations are 6 channel (5.1) installations, as opposed to 8 channel (7.1) installations. :''See also List of 8 channel SDDS films.'' While most major studios eventually began putting SDDS tracks on their releases, most independent films only came with Dolby Digital tracks, leaving many SDDS-equipped, or DTS theaters playing analog sound in otherwise state-of-the-art auditoriums. A few titles released under the
Kidtoon Films Kidtoon Films is a distributor of Children's film, children's animated films in the United States. The company is a subsidiary of The Bigger Picture, a Cineverse company. SD Entertainment previously owned it, which produced many of its earlier rel ...
program used SDDS tracks. As Dolby Digital (and to a lesser degree, DTS) began to emerge as the clear winner in the digital sound battle, Sony Cinema Products quit manufacturing SDDS encoders and decoders, although it will continue supporting equipment that is still deployed in the field. Out of the three competing formats, SDDS was the only format not to have a corresponding home-theater version, and Sony ceased production of new units in the early 2000s.


Technical

*Original format used: 8 micron (micrometre) square data bits, 16 bit per audio channel, 8 audio channels, 2 clock tracks, 2 guide tracks for alignment with the film. *Final format used: 24 micrometre square data bits. The format carries up to 8 channels of Dynamic Digital Sound (DDS) encoded using Sony's
ATRAC Adaptive Transform Acoustic Coding (ATRAC) is a family of proprietary audio compression algorithms developed by Sony. MiniDisc was the first commercial product to incorporate ATRAC, in 1992. ATRAC allowed a relatively small disc like MiniDisc t ...
codec with a compression ratio of about 5:1 and a sampling rate of 44.1 kHz. The channels are: *5 screen channels **Left **Left center **Center **Right center **Right *2 surround channels **Left surround **Right surround *Subwoofer channel Additionally there are 4 backup channels encoded – in case of damage to one side of the film or the other. These are: *Center *Subwoofer *Left + left center *Right + right center This gives a total of 12 channels, for which the total bitrate of 2.2 megabits per second. This is more than the maximum 1.536 megabits per second DTS format bitrate, and far greater than the cinema
Dolby Digital Dolby Digital, originally synonymous with Dolby AC-3 (see below), is the name for a family of audio compression technologies developed by Dolby Laboratories. Called Dolby Stereo Digital until 1995, it is lossy compression (except for Dolby Tr ...
bitrate of 320 kilobits (0.32 megabits) per second. For additional data reliability the two sides of the film are separated by 17 frames and half, so a single splice or series of missing frames will not result in a total loss of data.


Reader

The SDDS reader is mounted on top of a 35mm
projector A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a small transparent lens, but some newer type ...
. The film is threaded through the reader before it passes through the picture aperture. As the film runs, red LEDs are used to illuminate the SDDS
soundtrack A soundtrack is a recorded audio signal accompanying and synchronised to the images of a book, drama, motion picture, radio program, television show, television program, or video game; colloquially, a commercially released soundtrack album of m ...
. CCDs ( Charge-Coupled Devices) read the SDDS data and convert the stream of dots on the film into
digital information Digital data, in information theory and information systems, is information represented as a string of Discrete mathematics, discrete symbols, each of which can take on one of only a finite number of values from some alphabet (formal languages ...
. This information is pre-processed in the reader and passed on to the SDDS decoder.


Decoder

The SDDS decoder is installed in the sound equipment rack. The decoder receives the information from the reader and translates it into
audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...
signals routed to the cinema's power
amplifiers An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power suppl ...
. The decoder is responsible for a series of processes that must be performed before the audio is recovered. Next, errors caused by scratches or damage to the film are corrected using redundant error recovery data. Since SDDS is read at the top of the projector, the data is delayed slightly to restore synchronization with the picture. And finally, adjustments in tonal balance and playback level are made to match the specific auditorium's sound system and acoustics. SDDS is designed to process sound entirely in the digital domain, bypassing any existing analog processor, preserving clarity and providing full dynamic range.


References


External links


Official SDDS site
at the
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* {{Audio formats Audio codecs Audiovisual introductions in 1992 Film sound production Sony Surround sound Development organizations