Dolby Digital is the marketing name for a series of lossy audio compression technologies developed by Dolby Laboratories. A lossy 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
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Versions
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. A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for
Dolby Digital
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. A subwoofer is a Woofer, or a complete Loudspeaker dedicated to the reproduction of bass audio frequencies, from perhaps 150 Hz down Low-Frequency Effects ( LFE) is the name of an audio track specifically intended for deep low-pitched sounds ranging from 3-200 Hz. Mono and stereo modes are also supported. Monaural (often shortened to mono) sound reproduction is single-channel Stereophonic sound, commonly called stereo, is the reproduction of Sound, using two or more independent audio channels through a Symmetrical AC-3 supports audio sample-rates up to 48kHz. Batman Returns was the first film to use Dolby Digital technology when it premiered in theaters in Summer 1992. Batman Returns is a 1992 Superhero film directed by Tim Burton. The LaserDisc version of Clear and Present Danger featured the very first Home theater Dolby Digital mix in 1995. Clear and Present Danger is a 1994 film directed by Phillip Noyce, based on the book of the same name by Tom Clancy. Home cinema, also called home theater, are entertainment systems that seek to reproduce cinema quality video and audio in a private home
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. A codec is a device or program capable of encoding and/or decoding a Digital Data stream or signal. The Advanced Television Systems Committee (ATSC is the group established in 1982 that developed the eponymous ATSC Standards for Digital television in the 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. For the video game see True Lies (video game. True Lies is a 1994 action - Comedy film. The Dolby SR noise reduction 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 Bytestream is a series of Bytes typically of 8 bits each and can be A backronym (or bacronym) is a Phrase that is constructed "after the fact" from a previously existing word or Abbreviation, the abbreviation 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. Adaptive Transform Acoustic Coding ( ATRAC) is a family of proprietary audio compression algorithms developed by Sony. is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with B)
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 Pro Logic is a Surround sound processing technology designed to decode soundtracks encoded with Dolby Surround. Matrix decoder is an audio technology where a finite number of discrete audio channels (e 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. DTS (also known as Digital Theater Systems) owned by DTS Inc ( is a multi-channel digital Surround sound format used for both commercial/theatrical
Dolby Digital Live
Dolby Digital Live (DDL) is a real-time encoding technology for interactive media such as video games. A video game is a Game that involves interaction with a User interface to generate visual feedback on a video device. It converts any audio signals on a PC or game console into the 5. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated 1-channel Dolby Digital format and transports it via a single S/PDIF cable. S/PDIF specifies a Data Link Layer protocol and choice of Physical Layer specifications for carrying Digital audio [1] A similar technology known as DTS Connect is available from competitor DTS. DTS (also known as Digital Theater Systems) owned by DTS Inc ( is a multi-channel digital Surround sound format used for both commercial/theatrical
Dolby Digital Live is currently available in sound cards from manufacturers such as Turtle Beach[2], HT OMEGA SYSTEM[3], Auzentech[4] and Asus[5] using C-Media chipsets. A sound card (also known as an audio card is a Computer Expansion card that facilitates the input and output of audio signals to/from a computer under Turtle Beach Systems is a Sound card and Headphone manufacturer and direct competitor with Creative Labs -branded Sound Blaster. ASUSTeK Computer Incorporated (Asus () ( is a Taiwan -based multinational company that produces Motherboards Graphics cards Optical drives C-Media Electronics Inc (驊訊電子 is a Taiwanese Computer hardware company that manufactures processors for PC audio and USB storage, and wireless The SoundStorm, used for the Xbox game console and certain nForce2-based PCs, used an early form of this technology. SoundStorm was an advanced integrated 51 sound technology certification developed by Nvidia for the NForce2 platform based on the nForce audio processing The Xbox is a sixth-generation Video game console produced by Microsoft Corporation. Development The nForce2 features two different southbridges the MCP and the MCP-T
DDL is also available on motherboards with codecs such as Realtek's ALC882D,[6] ALC888DD and ALC888H. Products Realtek manufactures and sells a wide variety of products throughout the world and its product lines can be broadly categorized into two subdivisions Communications Network
DDL is also supported by all Creative X-Fi based sound cards, but is intentionally disabled in the drivers by Creative on all but the Auzentech Prelude. A programmer by the name daniel_k has fixed these drivers in Windows Vista by un-crippling DDL and fixing other bugs and has subsequently been censored and censured by Creative for doing so. [7]
An important benefit of this technology is that it enables the use of digital multichannel sound with consumer sound cards, which are otherwise limited to PCM stereo or multichannel analog.
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. Lucasfilm Limited' is an American Film production company founded by George Lucas in 1971, based in San Francisco California THX is a trade name of a high-fidelity sound reproduction standard for movie theaters screening rooms home theaters computer speakers gaming consoles and car audio systems Star Wars Episode I Phantom Menace is a 1999 military sci-fi film written and directed by George Lucas. 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. Star Wars is an epic Space opera franchise initially conceived by George Lucas during the 1970s and significantly expanded A number of DVDs have Dolby Digital Surround EX audio option.
Dolby Digital Plus
E-AC-3, more commonly known as Dolby Digital Plus, is an enhanced coding system based on the AC-3 codec. Dolby Digital Plus ( DD+ or E-AC-3) is a digital audio compression scheme developed specifically for the introduction of HD DVD and Blu-ray 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. A compression artifact (or artefact) is the result of an aggressive Data compression scheme applied to an Image, audio, or Video
Dolby TrueHD
Dolby TrueHD, developed by Dolby Laboratories, is an advanced lossless audio codec based on Meridian Lossless Packing. Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment Meridian Lossless Packing, also known as Packed PCM (PPCM is a proprietary Lossless compression technique for compressing PCM audio data developed by Meridian 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 14 channels (HD DVD and Blu-ray Disc standards currently limit the maximum number of audio channels to eight). It also supports extensive metadata, including dialog normalization and Dynamic Range Control.
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. Low-Frequency Effects ( LFE) is the name of an audio track specifically intended for deep low-pitched sounds ranging from 3-200 Hz. 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. Downmixing is a general term used for manipulating Audio where a number of distinct audio channels are mixed together to produce a lower number of channels 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. Low-Frequency Effects ( LFE) is the name of an audio track specifically intended for deep low-pitched sounds ranging from 3-200 Hz.
Applications of Dolby Digital
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. 35 mm film is the basic Film gauge most commonly used for both still Photography and Motion pictures, and remains relatively unchanged since its A release print is the reel of film that is sent to a movie theater for exhibition 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. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for These data are finally decoded into a 5. 1 channel audio source.
Dolby Digital audio is also used on DVD-Video and other purely digital media, like home cinema. DVD-Video is a consumer video format used to store digital video on DVD (DVD-ROM discs and is currently the dominant form of consumer video formats in the United Digital media (as opposed to analog media) usually refers to Electronic media that work on digital Codes. Home cinema, also called home theater, are entertainment systems that seek to reproduce cinema quality video and audio in a private home In this format, the AC-3 bitstream is interleaved with the video and control bitstreams.
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. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission 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 standards limit AC-3 to 448 kbit/s. Digital cable is a type of Cable television distribution using Digital Video compression. 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. is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer The Xbox is a sixth-generation Video game console produced by Microsoft Corporation. Some Sony PlayStation 2 console games are also capable to output AC-3 standard audio as well. is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with
Dolby is also part of a group of organizations involved in the development of AAC (Advanced Audio Coding), part of MPEG specifications, and considered the successor to MP3. Advanced Audio Coding ( AAC) is a standardized lossy compression and encoding scheme for Digital audio. The Moving Picture Experts Group, commonly referred to as simply MPEG, is a Working group of ISO / IEC charged with the development of video and MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a Digital audio encoding format using a form of Lossy data compression AAC outperforms AC-3 at any bitrate, but is more complex. [8]
Dolby Digital Plus (DD-Plus) is supported in HD DVD, as a mandatory codec, and in Blu-ray Disc, as an optional codec. not insert the publicly disclosed HD DVD key into this article for the time being
Dolby Technologies in packaged media formats
| HD DVD | Blu-ray | DVD | DVD-Audio | Laserdisc | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 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 | Player support | Channels (max) | Max Bit Rate |
| Dolby Digital | Mandatory | 5. not insert the publicly disclosed HD DVD key into this article for the time being DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering very High-fidelity audio content on a DVD. The Laserdisc (LD is an obsolete Home video disc format and was the first commercial Optical disc storage medium 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 | Optional | 5. 1 | 384 kbit/s |
| Dolby Digital Plus | 7. Dolby Digital Plus ( DD+ or E-AC-3) is a digital audio compression scheme developed specifically for the introduction of HD DVD and Blu-ray 1 | 3 Mbit/s | Optional | 7. 1 | 1. 7 Mbit/s | ||||||||||
| Dolby TrueHD | 8 | 18 Mbit/s | 8 | 18 Mbit/s | |||||||||||
Technical details
The data layout of AC-3 is described by simplified "C-like" language in official specifications. Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment tags please moot on the talk page first! --> In Computing, C is a general-purpose cross-platform block structured 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.
| Field Name | # of bits | Description |
|---|---|---|
| syncword | 16 | 0x0B77 Transmission of data is left bit first also known as Big Endian. In computing a syncword is used to synchronize data For example an audio receiver is receiving a bit stream of data |
| CRC | 16 | |
| Sampling frequency | 2 | '11'=reserved '10'=32 kHz '01'=44. A cyclic redundancy check (CRC is a type of function that takes as input a data stream of any length and produces as output a value of a certain space commonly a 32-bit integer Sampling theorem The Nyquist–Shannon sampling theorem states that perfect reconstruction 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. |
See also
- Dialnorm – Dolby Digital metadata parameter controlling decoder gain. Dialnorm is the meta-data parameter that controls decoder gain within the proprietary Dolby Laboratories Dolby Digital (AC-3 audio compression system
- Dolby Laboratories – company history and technology development.
- Dolby noise reduction systems for analogue recorded magnetic tape cassettes. Dolby NR is the name given to a series of noise reduction systems developed by Dolby Laboratories for use in analogue Magnetic tape recording The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a Magnetic tape sound
- Dolby Stereo – first cinema analogue surround sound system
- Dolby Pro Logic – consumer version of the Dolby Stereo analogue surround sound system. Dolby Stereo (or Dolby Analog) was the original analog optical technology developed by Dolby Laboratories for 35 mm film prints in 1976 Dolby Pro Logic is a Surround sound processing technology designed to decode soundtracks encoded with Dolby Surround.
- Dolby TrueHD – lossless codec for HD DVD and Blu-ray Disc
- Home cinema
- Loudspeaker
- SoundStorm – a real-time AC3 encoder for nForce2-based computers. Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment not insert the publicly disclosed HD DVD key into this article for the time being Home cinema, also called home theater, are entertainment systems that seek to reproduce cinema quality video and audio in a private home For the Marty Friedman album see Loudspeaker (album A loudspeaker, speaker, or speaker system is an electroacoustical SoundStorm was an advanced integrated 51 sound technology certification developed by Nvidia for the NForce2 platform based on the nForce audio processing Development The nForce2 features two different southbridges the MCP and the MCP-T
- C-Media – Producer of DDL audio chipsets used in many sound cards and motherboards. C-Media Electronics Inc (驊訊電子 is a Taiwanese Computer hardware company that manufactures processors for PC audio and USB storage, and wireless
References
- ^ Dolby Digital Live – Dolby. com
- ^ Montego DDL – Turtlebeach. com
- ^ [1] – Htomega. com
- ^ HDA X-Plosion 7.1 DTS Connect – Auzentech. com
- ^ [2] – techreport. com
- ^ NVIDIA nForce 500 motherboard reviews – AnandTech. com, June 8, 2006
- ^ Daniel_K, Who Fixed Creative's Broken Vista Drivers, Speaks Out Wired. Events 68 - The Roman Senate accepts emperor Galba. 536 - St Silverius becomes Pope (probable Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. com
- ^ http://www.ebu.ch/CMSimages/en/tec_doc_t3324-2007_tcm6-53801.pdf
External links
- Dolby Laboratories
- Dolby Chart
- AC3Filter - open source DirectShow AC3 decoder
- Open source liba52 dolby digital decoder
- ATSC standards, from which the A/52B "Digital Audio Compression (AC-3) Standard" may be downloaded
- A52Codec QuickTime codec, enables QuickTime to play back AC3 streams on PPC and Intel Macs
- Dolby Digital 5.1 television programs
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