Dolby ® Digital
Dolby ® Digital is currently the most widely used encoding/decoding surround sound format. It is used in over-the-air
TV broadcasts, digital cable and satellite broadcasts as well as DVD movies. Dolby ® Digital is a versatile format that can
be encoded/decoded as mono, stereo, or up to six distinct and independent channels in surround mode; Front
left and right, centre, left and right surround, as well as a low frequency
effects (LFE) channel, which is commonly referred to as the subwoofer channel. This format is commonly referenced as Dolby ® Digital 5.1 or just 5.1 to denote the five full range channels plus the additional LFE channel.
Dolby Digital EX
Dolby Digital EX extends the 5.1 channel setup of Dolby ® Digital by adding another channel. This channel which is the surround center channel can be deployed as a one or two speaker setup, which is denoted as 6.1 or 7.1 respectively. The additional channel adds to the realism and allows you to experience soundtracks more like they were meant to be heard.
Dolby Digital EX is identical to THX Surround EX. The format was
jointly developed by Dolby Laboratories and LucasFilm. Current films like
"Star Wars: The Phantom Menace”, that have been encoded with the Dolby Digital EX format places flags on DVD’s that will automatically activate the EX decoding on receivers that are equipped with a Dolby Digital EX processor. The centre surround channel is not a discrete channel; it is matrixed from
***with*** the left and right surround channels.
Dolby ®Digital Plus
Dolby ®Digital Plus is the next extension of the Digital Dolby format. This format features a higher data transfer rate, increased count of audio channels, utilizes the HDMI connections, can carry multiple languages on the same bitstream, and is backward compatible with other Dolby Digital
standards. Due to the current limitations of Blu-Ray and HD DVD formats, the number of discrete channels encoded will be limited to a 7.1 format. Dolby ®Digital Plus has been selected as a mandatory surround sound format to be encoded on HD DVD disc, and is
an optional encoding scheme for Blu-Ray Disc. It has also been selected by the Advanced Television Systems Committee (the governing body that develops standards for digital television) as the standard for future broadcast applications.
Dolby TrueHD is Dolby Laboratories next-generation lossless technology for use on high definition Blu-Ray discs, HD DVD discs and whatever comes next. The format extends on the capabilities of Dolby ®Digital Plus, but will use no compression whatsoever, so it will be bit-for-bit identical with the studio master. Dolby TrueHD is also a mandatory surround sound format for HD DVD disc as well as an optional format for Blu-Ray Disc. It will support 8 (the current limitation of Blu-Ray and HD DVD) or more full-range channels of 24-bit/96 kHz audio.