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Dolby Digital

Dolby Digital is a technology developed by Dolby Laboratories, Inc., a U.S. company, is famous by its lossy data compression, multimedia storage format technology.

  • 2.Versions


  • Dolby Digital has similar technologies, included in Dolby Digital EX, Dolby Digital Live, Dolby Digital Plus, Dolby Digital Surround EX, Dolby Digital Recording, Dolby Digital Cinema, Dolby Digital Stereo Creator and Dolby Digital 5.1 Creator.
    2.1 Dolby DigitalDolby Digital is the common version containing up to six discrete channels of sound. The most elaborate mode in common use involves five channels for normal-range speakers (20 Hz – 20,000 Hz) (right front, center, left front, rear right, rear left) 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. The Laserdisc version of Clear and Present Danger featured the first home theater Dolby Digital mix in 1995.
    This format got different names:
    • Dolby Digital
    • DD(Dolby Digital abbreviations are generally followed by the channel, or DD 5.1. Dolby standard does not comply with the abbreviation )
    • Dolby Surround AC-3 Digital (the second name of the standard release, only in the early (1995 and 1996))
    • Dolby Stereo Digital (the first name of the standard release, in early use)
    • Dolby SR-Digital (encoding combined with Dolby SR recording technology called)
    • SR-D (Dolby SR-Digital abbreviation)
    • Adaptive Transform Coder 3 (Dolby Digital bitstream format related)
    • AC-3 (short) of the above names
    • Audio Codec 3, 
    • Advanced Codec 3, Acoustic Coder 3 (These are backronyms. However, Adaptive Transform Acoustic Coding 3, or ATRAC3, developed by Sony another audio encoding format)
    • The ATSC A/52 (the name of the specifications, the existing version of A/52 Rev B)
  • 2.2 Dolby Digital EX
    Dolby Digital EX is similar in practice to Dolby's earlier Pro-Logic format, which utilized matrix technology to add a center surround channel and single rear surround channel to stereo soundtracks. EX adds an extension to the standard 5.1 channel Dolby Digital codec in the form of matrixed rear channels, creating 6.1 or 7.1 channel output.

  • 2.3 Dolby Digital Surround EX
    The cinema version of Dolby Digital EX is called Dolby Digital Surround Ex and works similarly. It was co-developed by Dolby and Lucasfilm THX in time for the release in May 1999 of Star Wars Episode I: The Phantom Menace. It provides an economical and backwards-compatible means for 5.1 soundtracks to carry a sixth, center back surround channel for improved localization of effects. The extra surround channel is matrix encoded onto the discrete left surround and right surround channels of the 5.1 mix, much like the front center channel on Dolby Pro Logic encoded stereo soundtracks. The result can be played without loss of information on standard 5.1 systems, or played in 6.1 or 7.1 on systems with Surround EX decoding and added speakers. Dolby Digital Surround EX has since been used for the Star Wars prequels on the DVD versions and also the remastered original Star Wars trilogy. A number of DVDs have Dolby Digital Surround EX audio option.

  • 2.4 Dolby Digital Live
  Dolby Digital Live, DDL is a real-time encoding technology applications in interactive media, such as electronic games. PC and console platforms, it encodes the audio into 5.1 channel output through the S / PDIF interface. SoundStorm, Xbox and nForce2 computer applications, the use of this technology prototype. Many use c-media sound card chip technologies such as Turtle Beach Turtle Beach and the Auzentech Prelude. In addition, the host version of the chip also has the use of this technology, such as Realtek's ALC882D for ALC888DD and ALC888H. DTS, Inc. also has the technology DTS Connect similar function. The benefits of this technology is it can make only supports analog output multichannel audio equipment to digital multi-channel output.
  • 2.5 Dolby Digital Plus
    Dolby Digital Plus is an enhanced coding system based on the AC-3 codec. It offers increased bitrates (up to 6.144 Mbit/s), support for more audio channels (up to 13.1), and improved coding techniques (only at low data rates) to reduce compression artifacts, enabling lower data rates than those supported by AC-3 (e.g. 5.1-channel audio at 256 kbit/s). It is not backward compatible with existing AC-3 hardware, though E-AC-3 decoders generally are capable of transcoding to AC-3 for equipment connected via S/PDIF. E-AC-3 decoders can also decode AC-3 bitstreams. Only the discontinued HD DVD system directly supported E-AC-3, though Blu-ray Disc offers E-AC-3 as an option to graft added channels onto an otherwise 5.1 AC-3 stream, as well as for delivery of secondary audio content (e.g. director's commentary) that is intended to be mixed with the primary audio soundtrack in the Blu-ray Disc player.

  • 2.6 Dolby TrueHD
    Dolby TrueHD, developed by Dolby Laboratories, is an advanced lossless audio codec based on Meridian Lossless Packing. Support for the codec was mandatory for HD DVD and is optional for Blu-ray Disc hardware. Dolby TrueHD supports 24-bit, 96 kHz audio channels at up to 18 Mbit/s over 14 channels (HD DVD and Blu-ray Disc standards currently limit the maximum number of audio channels to eight). It supports metadata, including dialog normalization and Dynamic Range Control.

  • 2.7 Dolby Surround 7.1
    Dolby Surround 7.1 was published in 2010, the latest format. In time for the release in the movie "Toy Story 3".
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