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Encyclopedia > Dolby Digital

Dolby Digital is the marketing name for a series of lossy audio compression technologies by Dolby Laboratories. A lossy data compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original, but is close enough to be useful in some way. ... Dolby Laboratories, Inc. ...

Contents

Versions

Dolby Digital includes several similar technologies. A digital system is one that uses discrete values (often electrical voltages), especially those representable as binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (ie, as in an analog system). ...


Dolby Digital

Dolby Digital logo that is sometimes shown on DVDs before the feature film starts
Dolby Digital logo that is sometimes shown on DVDs before the feature film starts

Dolby Digital, or AC-3, is the common version containing up to six discrete channels of sound, with 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) for the subwoofer driven low frequency effects. The Dolby Digital format supports mono and stereo usages as well. Batman Returns was the first film to use the Dolby Digital technology when it premiered in theaters in Summer 1992. The LaserDisc version of Clear and Present Danger featured the very first Home Theater Dolby Digital mix in 1995. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... a 12 subwoofer driver A subwoofer is a type of driver dedicated to the reproduction of bass frequencies, typically from about 20 Hz to perhaps 200 Hz in cone speakers, and in the case of a rotary woofer, all the way down to below 1 Hz. ... LFE is an abbreviation that is commonly used in describing an audio track contained within a 5. ... Monaural (often shortened to mono) sound reproduction is single-channel. ... Label for 2. ... Batman Returns is a 1992 motion picture based on the Batman character created by Bob Kane and Bill Finger. ... Clear and present danger is a term used in the case Schenck v. ...


This codec has several aliases, which are different names for the same codec: A codec is a device or program capable of performing encoding and decoding on a digital data stream or signal. ...

  • Dolby Digital (promotion 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)
  • Adaptive Transform Coder 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)

The Advanced Television Systems Committee (ATSC) is the group that helped to develop the new digital television standard for the United States, also adopted by Canada, Mexico, and South Korea and being considered by other countries. ... True Lies is a 1994 action/comedy remake of the 1991 French film La Totale!. It was directed by James Cameron, and stars Arnold Schwarzenegger, Jamie Lee Curtis, Tom Arnold, Bill Paxton, Tia Carrere, Charlton Heston and Art Malik. ... Dolby Analog SR or Dolby SR format (Spectral Recording), was developed by Dolby Laboratories and has been in common use in professional audio since 1986. ... A bitstream or bit stream is a time series of bits. ... A backronym or bacronym is a portmanteau of backward and acronym[1] coined in 1983. ... ATRAC (Adaptive TRansform Acoustic Coding) is an audio compression algorithm used to store information on Minidiscs and other Sony_branded audio players. ... Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $68. ...

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 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. However, the format is not considered a true 6.1 or 7.1 channel codec because it lacks the capability to support a discrete 6th channel unlike the competing DTS-ES codec. It has been suggested that this article or section be merged with Dolby Surround. ... In sound recording, a matrix can refer to a disc in the early stages of processing a record for mass production; see mastering and pressing process discussion at gramophone record. ... DTS DTS (formerly known as Digital Theater Systems), owned by DTS Inc (NASDAQ: DTSI), is a multi-channel surround sound format used for both commercial/theatrical and consumer grade applications (with significant technical differences between home and commercial/theatrical variants: the latter being a traditional ADPCM compression system and the...


Dolby Digital Live

Dolby Digital Live (DDL) is a real-time encoding technology for interactive media such as video games. It converts any audio signals on a PC or game console into the 5.1-channel Dolby Digital format and transports it via a single S/PDIF cable.[1] The SoundStorm, used for the Xbox game console and certain nForce2-based PCs, used an early form of this technology. Dolby Digital Live is currently available in sound cards from manufacturers such as Turtle Beach[2] and Auzentech[3] using C-Media chipsets, as well as on motherboards with codecs such as Realtek's ALC882D[4], ALC888DD and ALC888H [5] A similar technology known as DTS Connect is available from competitor DTS. This article is about computer and video games. ... The Altair 8800 was among the first microcomputers to be affordable by an individual, although it initially lacked peripherals and memory. ... Four different video game consoles from different generations. ... S/PDIF or S/P-DIF stands for Sony/Philips Digital Interface Format, also IEC 958 type II, part of IEC-60958. ... SoundStorm was an advanced integrated 5. ... The Xbox is a sixth generation era video game console produced by Microsoft Corporation. ... The nForce2 Chipset was released by NVIDIA in July of 2002 as a refresh to the original nForce product offering. ... A sound card is a computer expansion card that can input and output sound under control of computer programs. ... Turtle Beach Systems is a sound card and headphone manufacturer and direct competitor with Creative Labs-branded Sound Blaster. ... There are very few or no other articles that link to this one. ... Realtek Semiconductor Corp. ... DTS (formerly known as Digital Theater Systems), owned by DTS, Inc. ...


Dolby Digital Surround EX

Dolby Digital Surround EX 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 Surround 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 equipped with Surround EX decoding and additional 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. Dolby Laboratories, Incorporated (Dolby Labs) is a company specializing in audio compression and reproduction. ... Lucasfilm Ltd. ... THX logo This article is about the sound-system standard promulgated by George Lucas company. ... Film poster for Star Wars Episode I: The Phantom Menace Star Wars Episode I: The Phantom Menace is a 1999 film by George Lucas starring Liam Neeson, Ewan McGregor, Natalie Portman, and Jake Lloyd. ... This article needs additional references or sources to facilitate its verification. ...


Dolby Digital Plus

Main article: Dolby Digital Plus

E-AC-3, more commonly known as 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), improved coding techniques to reduce compression artifacts, and backward compatibility with existing AC-3 hardware. Dolby Digital Plus (DD+), also known as E-AC-3, was developed specifically for the introduction of HDTV and HD-DVD/Blu-ray discs. ... A compression artifact is a particular type of data error that is typically the result of quantization in lossy data compression. ...


Dolby TrueHD

Main article: Dolby TrueHD

Dolby TrueHD, from Dolby Laboratories, is an advanced lossless audio codec based on Meridian Lossless Packing. Support for the codec is mandatory for HD DVD and optional for Blu-ray Disc hardware. TrueHD supports 24 bit, 96 kHz audio channels at up to 18 Mbit/s over 8 channels (although HD DVD and Blu-ray Disc standards currently limit their maximum number of audio channels to eight, Dolby TrueHD can output up to 14 sound channels simultaneously). It also supports extensive metadata, including dialog normalization and Dynamic Range Control. Dolby TrueHD logo Dolby TrueHD, from Dolby Laboratories, is an advanced lossless multi-channel audio codec, intended primarily for high-end home-entertainment equipment, such as Blu-ray Disc and HD DVD. In this application, Dolby TrueHD competes with DTS-HD Master Audio, another lossless codec from Digital Theater System. ... Meridian Lossless Packing is a proprietary lossless compression technique for compressing PCM audio data. ... A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital media, including high-definition video. ...


Channel configurations

Although most commonly associated with the 5.1 channel configuration, Dolby Digital allows a number of different channel selections. The full list of available options is:

  • Mono (Center only)
  • 2-channel stereo (Left + Right), optionally carrying matrixed Dolby Surround
  • 3-channel stereo (Left, Center, Right)
  • 2-channel stereo with mono surround (Left, Right, Surround)
  • 3-channel stereo with mono surround (Left, Center, Right, Surround)
  • 4-channel quadrophonic (Left, Right, Left Surround, Right Surround)
  • 5-channel surround (Left, Center, Right, Left Surround, Right Surround)

All of these configurations can optionally include the extra Low Frequency Effect (LFE) channel. The last two with stereo surrounds can optionally use Dolby Digital EX matrix encoding to add an extra Rear Surround channel.


Many Dolby Digital decoders are equipped with downmixing functionality to distribute encoded channels to available speakers. This includes such functions as playing surround information through the front speakers if surround speakers are unavailable, and distributing the center channel to left and right if no center speaker is available. When outputting to separate equipment over a 2-channel connection, a Dolby Digital decoder can optionally encode the output using Dolby Surround to preserve surround information.


The '.1' in 5.1, 7.1 etc. refers to the LFE channel, which is also a discrete channel. LFE is an abbreviation that is commonly used in describing an audio track contained within a 5. ...


Applications of Dolby Digital

Dolby Digital recording on 35 mm film (between the sprocket holes). Look very closely and you will see the Dolby "Double-D" logo in the middle of the code pattern. The blue edge track is SDDS, a competing system.
Dolby Digital recording on 35 mm film (between the sprocket holes). Look very closely and you will see the Dolby "Double-D" logo in the middle of the code pattern. The blue edge track is SDDS, a competing system.

Dolby Digital SR-D cinema soundtracks are optically recorded on a 35 mm release print using sequential data blocks placed between every perforation hole on the sound track side of the film. A CCD scanner in the projector picks up a scanned video image of this area, and a processor correlates the image area and extracts the digital data as an AC-3 bitstream. These data are finally decoded into a 5.1 channel audio source. Image File history File linksMetadata Download high resolution version (1914x1393, 459 KB) Summary Macro of 35mm film audio tracks, from left to right: Sony SDDS, Dolby Digital, analog Optical, and finally DTS time code. ... Image File history File linksMetadata Download high resolution version (1914x1393, 459 KB) Summary Macro of 35mm film audio tracks, from left to right: Sony SDDS, Dolby Digital, analog Optical, and finally DTS time code. ... SDDS stands for Sony Dynamic Digital Sound, which is a cinema sound system developed by Sony. ... // In film formats, the sound track is the physical area of the film which records the synchronized sound. ... Simulated 35 mm film with soundtracks _ The outermost strips (on either side) contain the SDDS soundtrack as an image of a digital signal. ... A release print is the reel of film that is sent to a movie theater for exhibition. ... Film is a term that encompasses individual motion pictures, the field of film as an art form, and the motion picture industry. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... Projectors are used for displaying an image on a projection screen or similar surface for the view of an audience. ... A digital system is one that uses discrete values (often electrical voltages), especially those representable as binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (ie, as in an analog system). ...


Dolby Digital audio is also used on DVD-Video and other purely digital media, like home cinema. In this format, the AC-3 bitstream is interleaved with the video and control bitstreams. The DVD-Video format logo. ... Bold textDigital media (as opposed to analog media) usually refers to electronic media that work on digital codes. ... A 3 metres/119 inch projection screen with a high-definition television image. ...


The system is used in many bandwidth-limited applications other than DVD-Video, such as digital TV. The AC-3 standard allows a maximum coded bit rate of 640 kbit/s. 35 mm film prints use a fixed rate of 320 kbit/s. HD-DVD and DVD-Video discs are limited to 448 kbit/s, although many players can successfully play higher-rate bitstreams (which are non-compliant with the DVD specification). ATSC and Digital cable TV standards limit AC-3 to 448 kbit/s. Both Blu-ray Disc, the Sony PlayStation 3 and the Microsoft Xbox game console can output an AC-3 signal at a full 640 kbit/s. Some Sony PlayStation 2 console games are also capable to output AC-3 standard audio as well. A kilobit per second (kbit/s or kbps or kBaud) is a unit of data transfer rate equal to 1,000 bits per second. ... The Advanced Television Systems Committee (ATSC) is the group that helped to develop the new digital television standard for the United States, also adopted by Canada, Mexico, and South Korea and being considered by other countries. ... Cable television or Community Antenna Television (CATV) (and often shortened to cable) is a system of providing television, FM radio programming and other services to consumers via radio waves transmitted directly to people’s televisions through fixed coaxial cables as opposed to the over-the-air method used in... A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital media, including high-definition video. ... Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $68. ... PlayStation 3 , trademarked PLAYSTATION®3,[7] commonly abbreviated PS3) is Sony Computer Entertainments third video game console. ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ... The Xbox is a sixth generation era video game console produced by Microsoft Corporation. ... The Nintendo GameCube is an example of a popular video game console. ... Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $68. ... The PlayStation 2 , abbreviated PS2) is Sonys second video game console, the successor to the PlayStation and the predecessor to the PlayStation 3. ...


In certain console and PC games, for example, games from the Sony PlayStation 2 console platform, is capable to output real time Dolby Pro Logic or Dolby Pro Logic II audio during game play. Sony Corporation ) is a Japanese multinational corporation and one of the worlds largest media conglomerates with revenue of $68. ... The PlayStation 2 , abbreviated PS2) is Sonys second video game console, the successor to the PlayStation and the predecessor to the PlayStation 3. ...


Dolby is part of a group of organizations involved in the development of AAC (Advanced Audio Coding), part of MPEG specifications, and also considered the successor to MP3. AAC outperforms AC-3 at any bitrate, but is more complex. The advantages of AAC become clearly audible at less than 400 kbit/s for 5.1 channels, and at less than 180 kbit/s for 2.0 channels. Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. ... The Moving Picture Experts Group or MPEG is a working group of ISO/IEC charged with the development of video and audio encoding standards. ... MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular digital audio encoding format. ...


Dolby Digital Plus (DD-Plus) is supported in HD DVD, as a mandatory codec, and in Blu-ray Disc, as an optional codec. HD-DVD disc HD DVD (for High Density Digital Versatile Disc) is a digital optical media format which is being developed as one standard for high-definition DVD. HD DVD is similar to the competing Blu-ray Disc, which also uses the same CD sized (120 mm diameter) optical data... A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital media, including high-definition video. ...


Dolby Technologies in packaged media formats

HD DVD Blu-ray DVD DVD-Audio
Codec Player support Channels (max) Max Bit Rate Player support Channels (max) Max Bit Rate Player support Channels (max) Max Bit Rate Player support Channels (max) Max Bit Rate
Dolby Digital Mandatory 5.1 504 kbit/s Mandatory 5.1 640 kbit/s Mandatory 5.1 448 kbit/s Optional in video zone for playback compatibility on DVD-Video players 5.1 448 kbit/s
Dolby Digital Plus 7.1 3 Mbit/s Optional 7.1 1.7 Mbit/s N/A
Dolby TrueHD 8 18 Mbit/s 8 18 Mbit/s

HD-DVD disc HD DVD (for High Density Digital Versatile Disc) is a digital optical media format which is being developed as one standard for high-definition DVD. HD DVD is similar to the competing Blu-ray Disc, which also uses the same CD sized (120 mm diameter) optical data... Blu-ray discs Blu-ray Disc is a next-generation optical disc format jointly developed by a group of leading consumer electronics and PC companies called the Blu_ray Disc Association (BDA), which succeeds the Blu_ray Disc Founders (BDF). ... DVD (also known as Digital Versatile Disc or Digital Video Disc) is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. ... The DVD-Audio logo. ... Dolby Digital Plus (DD+), also known as E-AC-3, was developed specifically for the introduction of HDTV and HD-DVD/Blu-ray discs. ... Dolby TrueHD logo Dolby TrueHD, from Dolby Laboratories, is an advanced lossless multi-channel audio codec, intended primarily for high-end home-entertainment equipment, such as Blu-ray Disc and HD DVD. In this application, Dolby TrueHD competes with DTS-HD Master Audio, another lossless codec from Digital Theater System. ...

See also

Dialnorm is the meta-data parameter that controls decoder gain within the proprietary Dolby Laboratories Dolby Digital (AC-3) audio compression system. ... Dolby Laboratories, Inc. ... Dolby NR is a noise reduction system developed by Dolby Laboratories for use in analogue magnetic tape recording. ... Typical 60-minute Compact Cassette. ... Sign for Dolby Stereo Dolby Stereo (or Dolby Analog) was the original analog optical technology developed by Dolby Laboratories for 35 mm prints in 1976. ... It has been suggested that this article or section be merged with Dolby Surround. ... Dolby TrueHD logo Dolby TrueHD, from Dolby Laboratories, is an advanced lossless multi-channel audio codec, intended primarily for high-end home-entertainment equipment, such as Blu-ray Disc and HD DVD. In this application, Dolby TrueHD competes with DTS-HD Master Audio, another lossless codec from Digital Theater System. ... HD-DVD disc HD DVD (for High Density Digital Versatile Disc) is a digital optical media format which is being developed as one standard for high-definition DVD. HD DVD is similar to the competing Blu-ray Disc, which also uses the same CD sized (120 mm diameter) optical data... A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital media, including high-definition video. ... A 3 metres/119 inch projection screen with a high-definition television image. ... This article or section needs copy editing for grammar, style, cohesion, tone and/or spelling. ... SoundStorm was an advanced integrated 5. ... The nForce2 Chipset was released by NVIDIA in July of 2002 as a refresh to the original nForce product offering. ... There are very few or no other articles that link to this one. ...

Technical details

The data layout of AC-3 is described by simplified "C" like language in official specifications. An AC-3 stream is made up by a series of synchronization frames, which are composed of six audio blocks. Each audio block contains 256 audio samples per channel. Note 6×256 = 1536 = Audio frame size. Below is a simplified AC-3 header intended to give an introduction into the data syntax. A detailed description of the header can be found in the ATSC "Digital Audio Compression (AC-3) Standard", section 5.4. C is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...

Field Name # of bits Description
syncword 16 0x0B77   Transmission of data is left bit first also known as Big Endian.
CRC 16
Sampling frequency 2 '11'=reserved '10'=32 kHz '01'=44.1 '00'=48
Frame Size Code 6
Bit Stream Identification 5
Bit Stream Mode 3 '000'=main audio service
Audio Coding Mode 3 '010'=left, right channel ordering
Center Mix level 2
Surround Mix Level 2
Dolby Surround Mode 2 '00'=not indicated '01'=Not surround encoded '10'=Yes, surround encoded.

In computing a syncword is used to synchronize data. ... When integers or any other data are represented with multiple bytes, there is no unique way of ordering of those bytes in memory or in a transmission over some medium, and so the order is subject to arbitrary convention. ... A cyclic redundancy check (CRC) is a type of hash function used to produce a checksum – a small, fixed number of bits – against a block of data, such as a packet of network traffic or a block of a computer file. ... The sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. ...

References

  1. ^ Dolby Digital Live. Dolby.com.
  2. ^ Montego DDL. Turtlebeach.com.
  3. ^ HDA X-Plosion 7.1 DTS Connect. Auzentech.com.
  4. ^ anandtech.com. Jun 8, 2006.
  5. ^ Realtek ALC888.

External links


  Results from FactBites:
 
Dolby Digital - Wikipedia, the free encyclopedia (806 words)
Dolby Digital, or AC-3, is the common version containing 6 total channels of sound, with 5 channels for normal-range speakers (Right front, Center, Left Front, Right Rear and Left Rear) and one channel for the LFE, or subwoofer.
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 and single rear surround channel to stereo soundtracks.
Dolby is part of a group of organizations involved in the development of AAC (Advanced Audio Coding), part of MPEG specifications, and also considered the successor to MP3.
  More results at FactBites »

 
 

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