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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 sub-bass channel. The eight channel arrangement is similar to large format film magnetic sound formats like 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 premier with ''Hook'', the SDDS project was delayed and instead premiered on June 17, 1993, with the Arnold Schwarzenegger film ''Last Action Hero''. Since then, over 1,400 movies have been mixed 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" used to describe the original projected pictures in the late 19th century. Green came to mind because the key to imprinting the 8 micrometre data bits was to use a green laser. Initial development efforts were conducted for Sony's Columbia Pictures Sound Department under contract with Semetex Corp. of Torrance, California, U.S.A.. At Semetex, the SDDS Chief Architect was Jaye Waas and the Chief Optical Engineer was Mark Waring. The Semetex prototype design actually had the 8 channels of uncompressed data placed into 3 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 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 along with data compression, then allowed 24 micrometers square data. The SDDS development took just 11 months from concept to working sound camera. When it came time for deployment, since Sony also owned the Sony Theatres chain (later sold to Loews Theatres), it was able use SDDS in its own theatres. 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 in 1994 to include SDDS in all of their new auditoriums. This gave SDDS a much needed, albeit artificial, kick-start. More than likely it would have garnered far less penetration had Sony not controlled both a theatre chain and a film studio. SDDS was consistently the least popular of the three competing digital sound formats, the other two being Dolby Digital (aka SRD) 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 placement to the very edges of the film stock, SDDS tracks are more prone to damage than the some other digital formats. As with other 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, similar to a "CD skipping", 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 (Universal exclusively supported DTS until 1998, Disney exclusively supported Dolby until 1997, and Paramount and Fox placed SDDS tracks on only their biggest releases until 2001–2002), most independent films only came with Dolby Digital tracks, leaving many SDDS-equipped theaters playing analog sound in otherwise state-of-the-art auditoriums. 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. Until the conversion to digital projection began to render 35mm film increasingly irrelevant, a majority of release prints for major studio films were created with all three digital tracks – Dolby Digital, DTS and Sony's SDDS (each digital track uses different film geography so all three, as well as the analog track, can coexist on one print). 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sony Dynamic Digital Sound」の詳細全文を読む スポンサード リンク
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