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Dolby Digital

Dolby Digital
AbbreviationDD
Formation1986
TypeAudio compression format, lossy compression
Location
  • United States
Area served
Worldwide
Websiteprofessional.dolby.com/tv/dolby-digital/
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Dolby Digital, originally synonymous with Dolby AC-3, 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 TrueHD). The first use of Dolby Digital was to provide digital sound in cinemas from 35 mm film prints. It has since also been used for TV broadcast, radio broadcast via satellite, digital video streaming, DVDs, Blu-ray discs and game consoles.

The basis of the Dolby AC-3 multi-channel audio coding standard is the modified discrete cosine transform (MDCT), a lossy audio compression algorithm.[1] It is a modification of the discrete cosine transform (DCT) algorithm, which was proposed by Nasir Ahmed in 1972 for image compression.[2] The DCT was adapted into the MDCT by J.P. Princen, A.W. Johnson and Alan B. Bradley at the University of Surrey in 1987.[3]

Dolby Laboratories adapted the MDCT algorithm along with perceptual coding principles to develop the AC-3 audio format for cinema. The AC-3 format was released as the Dolby Digital standard in February 1991.[4][5] Dolby Digital was the earliest MDCT-based audio compression standard released, and was followed by others for home and portable usage, such as Sony's ATRAC (1992), the MP3 standard (1993) and AAC (1997).[6]

  1. ^ Andersen, Robert Loring; Crockett, Brett Graham; Davidson, Grant A.; Davis, Mark Franklin; Fielder, Louis D.; Turner, Stephen C.; Vinton, Mark S.; Williams, Phillip (October 2004). "Introduction to Dolby Digital Plus, an Enhancement to the Dolby Digital Coding System" (PDF). Audio Engineering Society Convention (117th AES Convention): 1–29. Retrieved 17 October 2019.
  2. ^ Ahmed, Nasir (January 1991). "How I Came Up With the Discrete Cosine Transform". Digital Signal Processing. 1 (1): 4–5. doi:10.1016/1051-2004(91)90086-Z.
  3. ^ Princen, J.P.; Johnson, A.W.; Bradley, Alan B. (1987). "Subband/Transform coding using filter bank designs based on time domain aliasing cancellation". ICASSP '87. IEEE International Conference on Acoustics, Speech, and Signal Processing. Vol. 12. pp. 2161–2164. doi:10.1109/ICASSP.1987.1169405. S2CID 58446992.
  4. ^ Britanak, V. (2011). "On Properties, Relations, and Simplified Implementation of Filter Banks in the Dolby Digital (Plus) AC-3 Audio Coding Standards". IEEE Transactions on Audio, Speech, and Language Processing. 19 (5): 1231–1241. doi:10.1109/TASL.2010.2087755. S2CID 897622.
  5. ^ "A Chronology of Dolby Laboratories: May 1965-May 1998" (PDF). Film-Tech. Dolby. Archived from the original (PDF) on 18 March 2006. Retrieved 15 May 2022.
  6. ^ Luo, Fa-Long (2008). Mobile Multimedia Broadcasting Standards: Technology and Practice. Springer Science & Business Media. p. 590. ISBN 9780387782638.