Dolby Digital includes several similar technologies, which include Dolby Digital, Dolby Digital EX, Dolby Digital Live, Dolby Digital Surround EX, Dolby Digital Plus, and Dolby TrueHD.
Dolby Digital, or AC-3, is the common version containing up to six discrete channels of sound. The most elaborate mode in common usage involves five channels for normal-range speakers (20 Hz – 20,000 Hz) (right front, center, left front, right rear and left rear) and one channel (20 Hz – 120 Hz allotted audio) for the subwoofer driven low-frequency effects. Mono and stereo modes are also supported. AC-3 supports audio sample-rates up to 48 kHz. Batman Returns was the first film to use Dolby Digital technology when it premiered in theaters in Summer 1992. The Laserdisc version of Clear and Present Danger featured the first Home theater Dolby Digital mix in 1995.
This codec has several aliases, which are different names for the same codec:
* Dolby Digital (promotional name, not accepted by the ATSC)
* DD (an abbreviation of above, often combined with channel count: DD 5.1)
* Dolby Surround AC-3 Digital (second promotional name, as seen on early film releases and on home audio equipment until about 1995/1996)
* Dolby Stereo Digital (first promotional name, as seen on early releases, also seen on True Lies LaserDisc)
* Dolby SR-Digital (when the recording incorporates a Dolby SR-format recording for compatibility)
* SR-D (an abbreviation of above)
* Audio Coding 3 (relates to the bitstream format of Dolby Digital)
* AC-3 (an abbreviation of above)
* Audio Codec 3, Advanced Codec 3, Acoustic Coder 3 (These are backronyms. However, Adaptive Transform Acoustic Coding 3, or ATRAC3, is a separate format developed by Sony)
* ATSC A/52 (name of the standard, current version is A/52 Rev. B)