Sound-on-film
Sound-on-film is a class of sound film processes where the sound accompanying a picture is recorded on photographic film, usually, but not always, the same strip of film carrying the picture. Sound-on-film processes can either record an analog sound track or digital sound track, and may record the signal either optically or magnetically. Earlier technologies were sound-on-disc, meaning the film's soundtrack would be on a separate phonograph record.[1]
History[edit]
Sound on film can be dated back to the early 1880s, when Charles E. Fritts filed a patent claiming the idea. In 1923 a patent was filed by E. E. Ries, for a variable density soundtrack recording, which was submitted to the SMPE (now SMPTE), which used the mercury vapor lamp as a modulating device to create a variable-density soundtrack. Later, Case Laboratories and Lee De Forest attempted to commercialize this process, when they developed an Aeolite glow lamp, which was deployed at Movietone Newsreel at the Roxy Theatre in 1927. In 1928, Fox Film purchased Case Laboratories and produced its first talking film In Old Arizona using the Aeolite system. The variable-density sound system was popular until the mid-1940s.[2]
Opposite with variable-density, in the early 1920s, variable-area sound recording was first experimented on by the General Electric Company, and later was applied by RCA which refined GE's technology. After the mid-1940s, variable-area system superseded the variable-density system, and became the major analog sound-on-film system until modern day.
Digital sound-on-film formats[edit]
Three different digital soundtrack systems for 35 mm cinema release prints were introduced during the 1990s. They are: Dolby Digital, which is stored between the perforations on the sound side; SDDS, stored in two redundant strips along the outside edges (beyond the perforations); and DTS, in which sound data is stored on separate compact discs synchronized by a timecode track on the film just to the right of the analog soundtrack and left of the frame[3] (sound-on-disc). Because these soundtrack systems appear on different parts of the print, one movie can contain all of them, allowing broad distribution without regard for the sound system installed at individual theatres.