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.