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Proceedings Paper

AC-3 audio coder
Author(s): Craig Todd
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Paper Abstract

AC-3 is a system for coding up to 3.1 channels of audio into a low bit-rate data stream. High quality may be obtained with compression ratios approaching 12-1 for multichannel audio programs. The high compression ratio is achieved by methods which do not increase decoder memory, and thus cost. The methods employed include: the transmission of a high frequency resolution spectral envelope; and a novel forward/backward adaptive bit allocation algorithm. In order to satisfy practical requirements of an emissions coder, the AC-3 syntax includes a number of features useful to broadcasters and consumers. These features include: loudness uniformity between programs; dynamic range control; and broadcaster control of downmix coefficients. The AC-3 coder has been formally selected for inclusion in the U.S. HDTV broadcast standard, and has been informally selected for several additional applications.

Paper Details

Date Published: 25 October 1995
PDF: 12 pages
Proc. SPIE 10282, Standards and Common Interfaces for Video Information Systems: A Critical Review, 1028203 (25 October 1995); doi: 10.1117/12.227958
Show Author Affiliations
Craig Todd, Dolby Labs. (United States)


Published in SPIE Proceedings Vol. 10282:
Standards and Common Interfaces for Video Information Systems: A Critical Review
K. R. Rao, Editor(s)

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