A Brief Glossary of Sound Formats and Related Elements Compiled by Karen Kalish
	CDS (Cinema Digital Sound) was a digital release format that was designed to replace the analog track with digital information. It was first released in a 70mm format in the 80s, however, it was short lived because the industry refused to give up the analog sound track.   Dolby Digital (SRD) is a digital release format which optically prints a 6 channel soundtrack between the sprocket holes, next to the stereo SR analog track on 35mm film   Dolby SR (Spectral Recording) is Dolby's most recent analog release format. It provides greater noise reduction than the Dolby A-type system and permits recording at a wider frequency range, particularly at high signal levels.   Dolby Stereo was introduced in the mid 1970s to replace 35mm mono optical sound tracks. Adapted from the "Quadraphonic" era of the record industry, this is a method of encoding 4 channels of audio (left, center, right & mono surround) into two stereo optical channels.   DTS (Digital Theater Systems) is a digital release format which is not printed directly on the film. The digital track of this 6-channel format is stored on a CD-ROM. Timecode data, which controls a CD-ROM player, is placed between the elements and the stereo optical track. DTS prints also have an analog track. (This system can accommodate an extra CD ROM drive capable of playing voice description of a film's actions for the visually impaired, which are transmitted to viewers through wireless headphones.)   SDDS (Sony Dynamic Digital Sound) is a digital release format, with an analog track as part of their system. The digital tracks are printed outside the sprocket holes along both outer edges of 35mm film. This system, which has the capability of playing 8 channels, was designed for all theater projection auditoriums - it has a fold-down mechanism that can play back from 8 channels down to six channels or mono, as needed.   Single Print Inventory refers to prints which have any number of digital formats, plus a conventional analog track, on the same print. They are also known as compatible prints.   Subwoofer is a loudspeaker dedicated to reproducing only the very low bass.   THX is a division of Lucasfilm Ltd., whose mandate is to ensure that the quality of the original picture and sound of a film is delivered into each venue. This is carried out through four THX operations which license the THX trademark when the performance parameters of Lucasfilm Ltd. are met. 1) The THX Theatre Program works with exhibitors on the building of THX-approved movie theaters. 2) The THX Theatre Alignment Program (TAP) offers quality assurance services to studios and filmmakers that address the print manufacturing and theatrical presentation stages of a film's release. 3) The Home THX Program licenses proprietary technology to audio video manufacturers who build the Home THX Theatre systems. 4) Like the TAP program, THX offers quality assurance services in the mastering and duplication process for films transferred onto laser discs and videotapes.   Ultra Stereo is a 2-track 4-channel analog encoding and decoding system. It is an alternative to the Dolby A system.   Variable Area is an analog optical track whose width varies with the sound. It is also used on 16mm prints.   Variable Density is an analog optical track which varies in photographic shading with the sound, rather than in width. It is not used much for modern prints. The numbers: Dolby digital screens worldwide have totaled 6,998 with North America totaling 2,445. The DTS worldwide total is 7,804 with North America totaling 4,514. The total of SDDS installations is 3,110 worldwide with North America totaling 2,603. (Data for 11/3/96.)
This glossary was compiled with the support of individuals from DTS, DOLBY Labs, Lucasfilm, N.T. Audio, SDDS, and Ultra Stereo. (To date, Disney, N.T. Audio and Warner Bros. have the capacity to shoot Dolby Digital, DTS and SDDS, in addition to the analog optical track, on one piece of film.) Karen Kalish works at N.T. Audio Video Film Labs.   Reprinted from The Motion Picture Editors Guild Newsletter Vol. 18, No. 1 - Jan/Feb 1997   Guild Home | Newsletter Home | Top of Page   Copyright © 1996, All Rights Reserved by The Motion Picture Editors Guild, IATSE Local 776