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Dolby
Trade name for an audio noise-reduction system.
Dolby Digital (DD/AC-3)
A digital audio compression system that uses auditory masking for compression. It works with from 1 to 5.1 channels for audio and can carry Dolby Surround coded two-channel material. It applies audio masking over all channels and dynamically allocates bandwidth from a ‘common pool’. Dolby Digital is a constant bit rate system supporting 64 kb/s to 640 kb/s rates; typically 64 kb/s mono, 192 kb/s two-channel, 320 kb/s 35 Cinema 5.1, 384 kb/s Laserdisc/DVD 5.1, and DVD 448 kb/s 5.1.
DVD players and ATSC receivers with Dolby Digital capability can provide a backward-compatible mix-down by extracting the five main channels and coding them into analogue Dolby Surround for Pro Logic playback.
References
Pank, B., Editor, 1998, The Digital Factbook, 9th Ed, Quantel, Newbury, UK
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