AC-3

AC-3, also known as "Dolby® Digital,” is a form of lossy audio compression developed by Dolby Laboratories that compresses PCM audio into an encoded digital bitstream for use in various forms of digital media, (most commonly DVD video and digital TV broadcasts), where data capacity is limited. Dolby Digital streams are a required audio codec for DVD and a supported codec for Blu-ray® Discs.

A Dolby Digital bitstream can manage up to six channels of 5.1 discreet audio but is also capable of carrying Lt/Rt stereo (Dolby® Surround), 2.0 stereo/mono, and even 1.0 mono at bit rates from 640 kbps (max) down to 96 kbps (min). DVD video and ATSC broadcast specs only support up to 448 kbps, and this is the most common compression rate used in those mediums. Blu-ray Discs can carry bitstreams up to the maximum of 640 kbps.

Dolby Digital bitstreams require a Dolby Digital decoder to turn the bitstream back into actual audio. Dolby Digital decoders usually come standard on all home theater receivers, DVD, and Blu-ray Disc players.

DTS, which is a similar lossy audio compression codec, is Dolby Digital's only competition, (in terms of compressed audio data for film and television), at this time.

This control panel, which allows an audio engineer to specify down-mix parameters and other bitstream information, is one of many that an audio engineer encounters when creating AC-3 bitstreams.