Ultra Stereo

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Ultra Stereo is a cinematographic sound system that was developed by the year 1984^[1] in competition to the predominant format, Dolby Stereo, by former employees of that company. Four channels of information (Left, Center, Right and Surround) are matrix-encoded into two soundtracks on 35mm optical theatrical release prints, occupying the same area of the film which previously held the monophonic soundtrack. The matrix-encoded track is decoded by the cinema processor in the theater during exhibition.

Ultra Stereo Labs (USL), which had been concentrating on the manufacture of sound equipment for studio screening rooms, was drawn into the exhibition-end of the business quite by chance. A theater owner asked USL if they could produce a theatrical stereo sound system. The company developed a cinema processor, but according to USL founder Jack Cashin, nobody at USL was very happy with the performance of the unit. The "perfection bug" hit and over the next several years they kept improving it and eventually placed the processor in a couple of theaters and USL began getting interest in it. Specifically the USL cinema processor achieved greater channel separation than had been possible up to that time. Also, a balancing circuit was included which took care of film weave and some of the imbalances between the left and right soundtracks, a common problem with early optical systems, which caused voice leakage into the surround channel. For making improvements in film sound Ultra Stereo Labs won a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences in 1984.^[2]

Soon thereafter USL also became involved in encoding movie soundtracks. Since they had been manufacturing studio equipment for quite some time, people asked the company to develop encoding equipment for making print masters. Films encoded in Ultra Stereo can be also decoded on Dolby Cinema processors, as it was designed to be compatible with Dolby Stereo (with A-Type noise reduction) prints.

Ultra Stereo is a 4/2/4 photographic sound encoding and decoding procedure that has the same technical basic data, and similar audio quality, as Dolby Stereo. As of 2007, over 900 titles are listed on the Internet Movie Database as using this format, a high percentage of which are low-budget and independent films.