Dolby Digital

Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories

Dolby Laboratories

Dolby Laboratories, Inc. , often shortened to Dolby Labs, is an American company specializing in audio noise reduction and audio encoding/compression.-History:...

. It was originally called Dolby Stereo
Dolby Stereo
Dolby Stereo, is the trade mark that Dolby Laboratories used for the various analogue stereo cinema sound formats that they produced.Two basic systems used this name. The first was the 'Dolby SVA' system used with optical soundtracks on 35mm film...

Digital until 1994

1994 in film

1994 was a significant year in film.The top grosser worldwide was The Lion King, which to date stands as the highest-grossing traditionally-animated film of all time...

. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints. It is now also used for other applications such as TV broadcast, DVD

DVD

A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....

s, Blu-ray disc

Blu-ray Disc

Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...

s and game consoles.

Dolby Digital in the cinema

Batman Returns
Batman Returns
Batman Returns is a 1992 American superhero film directed by Tim Burton. Based on the DC Comics character Batman, it is the sequel to Burton's Batman , and features Michael Keaton reprising the title role, with Danny DeVito as the Penguin and Michelle Pfeiffer as Catwoman.Burton originally did not...

was the first film to use Dolby Digital technology when it premiered in theaters in Summer 1992. Dolby Digital cinema soundtracks are optically recorded on a 35 mm release print

Release print

A release print is a copy of a film that is sent to a movie theater for exhibition.-Definitions:Release prints are not to be confused with the other types of print used in the photochemical post-production process:...

using sequential data blocks placed between every perforation hole on the sound track side of the film. A constant bit rate of 320kbit/s is used. A CCD

Charge-coupled device

A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...

scanner in the projector

Image projector

An image projector is an optical device that projects an image onto a surface, commonly a projection screen.Most projectors creates an image by shining a light through a small transparent image, but some newer types of projectors can project the image directly, by using lasers...

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

Bitstream

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 regarded as a special case of a bitstream....

. This data is finally decoded into a 5.1 channel audio source. All film prints with Dolby Digital data also have Dolby Stereo

Dolby Stereo

Dolby Stereo, is the trade mark that Dolby Laboratories used for the various analogue stereo cinema sound formats that they produced.Two basic systems used this name. The first was the 'Dolby SVA' system used with optical soundtracks on 35mm film...

analogue soundtracks using Dolby SR noise reduction and such prints are known as Dolby SR-D prints. The analogue soundtrack provides a fall-back option in case of damage to the digital data or failure of the digital decoding, it also provides compatibility with projectors not equipped with digital soundheads. Almost all current release cinema prints are of this type and will probably also include SDDS data and a timecode track to synchronise CDROMs carrying DTS soundtracks.

The simplest way of converting existing projectors is to add a so-called "penthouse" digital soundhead above the projector head. However for new projectors it made sense to use dual analogue/digital soundheads in the normal optical soundhead position under the projector head. To allow for the dual-soundhead arrangement the digital data is recorded 26 frames ahead of the picture. If a penthouse soundhead is used then the data must be delayed in the processor for the required amount of time, around 2 seconds. This delay can be adjusted in steps of the time between perforations, (approximately 10.4msec)

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.

Dolby Digital is the common version containing up to six discrete channels of sound. The most elaborate mode in common usage 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

Subwoofer

A subwoofer is a woofer, or a complete loudspeaker, which is dedicated to the reproduction of low-pitched audio frequencies known as the "bass". The typical frequency range for a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound, and below...

driven low-frequency effects. Mono

Monaural

Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...

and stereo

Stereophonic sound

The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...

modes are also supported. AC-3 supports audio sample-rates up to 48 kHz.
The Laserdisc

Laserdisc

LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...

version of Clear and Present Danger
Clear and Present Danger (film)
Clear and Present Danger is a 1994 film directed by Phillip Noyce, based on the book of the same name by Tom Clancy. It is a subsequent release to the 1992 film Patriot Games, which in itself is a subsequent release to the 1990 film The Hunt for Red October.It is the last film to feature Harrison...

featured the first Home theater

Home cinema

Home cinema, also commonly called home theater, are home entertainment set-ups that seek to reproduce a movie theater experience and mood with the help of video and audio equipment in a private home....

Dolby Digital mix in 1995.

This format has different names:

Dolby Digital
DD (an abbreviation for Dolby Digital, often combined with channel count; for instance, DD 2.0, DD 5.1)
AC-3 (Audio Codec 3, Advanced Codec 3, Acoustic Coder 3. These are backronym
Backronym
A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....

s. However, Adaptive Transform Acoustic Coding 3, or ATRAC3, is a separate format developed by Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

)
ATSC A/52 (name of the standard)

Dolby Digital EX

Dolby Digital EX is similar in practice to Dolby's earlier Pro-Logic

Dolby Pro Logic

Dolby Pro Logic is a surround sound processing technology developed by Dolby Laboratories, designed to decode soundtracks encoded with Dolby Surround. Dolby Stereo was originally developed by Dolby in 1976 for analog cinema sound systems...

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

Surround sound

Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...

or 7.1 channel output.

Dolby Digital Surround EX

The Cinema Version of "Dolby Digital EX" is called Dolby Digital Surround Ex and works similarly. Dolby Digital Surround EX was co-developed by Dolby and Lucasfilm

Lucasfilm

Lucasfilm Limited is an American film production company founded by George Lucas in 1971, based in San Francisco, California. Lucas is the company's current chairman and CEO, and Micheline Chau is the president and COO....

THX

THX is a trade name of a high-fidelity audio/visual reproduction standard for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, and car audio systems. The current THX was created in 2001 when it spun off from Lucasfilm Ltd...

in time for the release in May 1999 of Star Wars Episode I: The Phantom Menace
Star Wars Episode I: The Phantom Menace
Star Wars Episode I: The Phantom Menace is a 1999 American epic space opera film written and directed by George Lucas. It is the fourth film to be released in the Star Wars saga, as the first of a three-part prequel to the original Star Wars trilogy, as well as the first film in the saga in terms...

. 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

Center channel

Center channel refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or fully, dedicated to the reproduction of the dialogue of an audiovisual program...

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 additional speakers.
Dolby Digital Surround EX has since been used for the Star Wars

Star Wars

Star Wars is an American epic space opera film series created by George Lucas. The first film in the series was originally released on May 25, 1977, under the title Star Wars, by 20th Century Fox, and became a worldwide pop culture phenomenon, followed by two sequels, released at three-year...

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 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 a 5.1-channel 16-bit/48 kHz Dolby Digital format at 640 kbit/s and transports it via a single S/PDIF

S/PDIF

S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...

cable. A similar technology known as DTS Connect is available from competitor DTS

Digital Theater System

DTS is a series of multichannel audio technologies owned by DTS, Inc. , an American company specializing in digital surround sound formats used for both commercial/theatrical and consumer grade applications...

. 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 digital PCM

Pulse-code modulation

Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...

stereo or analog multichannel sound because S/PDIF over RCA, BNC, and TOSLINK can only support two-channel PCM, Dolby Digital multichannel audio, and DTS multichannel audio. HDMI

HDMI

HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...

was later introduced, and it can carry uncompressed multichannel PCM, lossless compressed multichannel audio, and lossy compressed digital audio. However, Dolby Digital Live is still useful with HDMI to allow transport of multichannel audio over HDMI to devices that are unable to handle uncompressed multichannel PCM.

Dolby Digital Live is available in sound cards using various manufacturers' audio chipsets. The SoundStorm

SoundStorm

SoundStorm was an advanced integrated 5.1 sound technology certification developed by Nvidia for the nForce and nForce2 platforms based on the nForce audio processing unit .-Certification:...

, used for the Xbox

Xbox

The Xbox is a sixth-generation video game console manufactured by Microsoft. It was released on November 15, 2001 in North America, February 22, 2002 in Japan, and March 14, 2002 in Australia and Europe and is the predecessor to the Xbox 360. It was Microsoft's first foray into the gaming console...

game console and certain nForce2

NForce2

The nForce2 chipset was released by Nvidia in July 2002 as a refresh to the original nForce product offering. The nForce2 chipset was a platform for motherboards supporting AMD's Socket A CPUs along with DDR SDRAM...

motherboards, used an early form of this technology. DDL is available on motherboards with codecs such as Realtek

Realtek

Realtek Semiconductor Corp. , a fabless IC design house situated in the Hsinchu Science Park, Hsinchu, Taiwan, was founded in October 1987, and subsequently approved as a listed company on the Taiwan Stock Exchange in 1998...

's ALC882D, ALC888DD and ALC888H. Other examples include some C-Media

C-Media

C-Media Electronics, Inc. is a Taiwanese computer hardware company that manufactures processors for PC audio and USB storage, and wireless audio devices.-Products:-PCI audio:*CMI8338*CMI8738-SX*CMI8738-LX*CMI8738-MX*CMI8768...

PCI sound cards and Creative Labs' X-Fi sound cards whose drivers have enabled support for DDL.

Since September 2008, all Creative X-Fi based sound cards support DDL (except the 'Xtreme Audio' and its based line such as Prodigy 7.1e, which is not capable of DDL in hardware). X-Fi

X-Fi (audio chip)

X-Fi is the commercial name for Creative Labs' E-MU 20K1 and E-MU 20K2 audio chips. The 20K1 chip was launched in August 2005, and ever since it has been used in a variety of audio solutions from Creative Labs, and more recently third-party manufacturers, such as Korean manufacturer Auzentech...

's case differs.

Initially no Creative X-Fi based sound cards supported DDL (2005~2007) but a collaboration of Creative and Auzentech resulted in the development of the Auzentech Prelude, the first X-Fi card to support DDL. Originally planned to extend DDL support to all X-Fi based sound cards (except the 'Xtreme Audio' line which is not capable of DDL hardware implementation), the plan was dropped because Dolby licensing would have required a royalty payment for all X-Fi cards and, problematically, those already sold.
In 2008 Creative released the X-Fi Titanium series of sound cards which fully supports Dolby Digital Live while leaving all PCI versions of Creative X-Fi still lacking support for DDL.

While they forgot about the plan, programmer Daniel Kawakami made a hot issue by applying Auzentech Prelude DDL module back to Creative X-Fi cards by disguising the hardware identity as Auzentech Prelude.

Creative Labs alleged Kawakami violated their intellectual property and demanded he cease distributing his modified drivers.
Eventually Creative struck an agreement with Dolby Laboratories regarding the Dolby license royalty by arranging that the licensing cost be folded into the purchase price of the Creative X-Fi PCI cards rather than as a royalty paid by Creative themselves. Based on the agreement, in September 2008 Creative began selling the "Dolby Digital Live" packs enabling Dolby Digital Live on Creative's X-Fi PCI series of sound cards. It can be purchased and downloaded from Creative. Subsequently Creative added their "DTS Connect" pack to the DDL pack at no additional cost.

Dolby Digital Plus

E-AC-3 (Dolby Digital Plus) is an enhanced coding system based on the AC-3 codec

Codec

A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

. It offers increased bitrate

Bitrate

In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....

s (up to 6.144 Mbit/s), support for more audio channels (up to 13.1), and improved coding techniques 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 decoder

Decoder

A decoder is a device which does the reverse operation of an encoder, undoing the encoding so that the original information can be retrieved. The same method used to encode is usually just reversed in order to decode...

s generally are capable of transcoding to AC-3 for equipment connected via S/PDIF

S/PDIF

. E-AC-3 decoders are also capable of decoding AC-3 bitstreams. Only the discontinued HD DVD

HD DVD

HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...

system directly supported E-AC-3, though Blu-ray Disc

Blu-ray Disc

offers E-AC-3 as an option to graft additional channels onto an otherwise 5.1

5.1 surround sound

5.1 is the common name for six channel surround sound multichannel audio systems. 5.1 is now the most commonly used layout in both commercial cinemas and home theaters. It uses five full bandwidth channels and one low frequency enhancement channel . Dolby Digital, Dolby Pro Logic II, DTS, and...

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.

Dolby TrueHD

Dolby TrueHD, developed by Dolby Laboratories, is an advanced lossless audio codec based on Meridian Lossless Packing

Meridian Lossless Packing

Meridian Lossless Packing, also known as Packed PCM , is a proprietary lossless compression technique for compressing PCM audio data developed by Meridian Audio, Ltd. MLP is the standard lossless compression method for DVD-Audio content and typically provides about 1.5:1 compression on most music...

. Support for the codec was mandatory for HD DVD and is optional for Blu-ray Disc

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.

Channel configurations

Although commonly associated with the 5.1 channel configuration, Dolby Digital allows a number of different channel selections. The options are:

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 quadraphonic (Left, Right, Left Surround, Right Surround)
5-channel surround
5.1 surround sound
5.1 is the common name for six channel surround sound multichannel audio systems. 5.1 is now the most commonly used layout in both commercial cinemas and home theaters. It uses five full bandwidth channels and one low frequency enhancement channel . Dolby Digital, Dolby Pro Logic II, DTS, and...

(Left, Center, Right, Left Surround, Right Surround)

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

Many Dolby Digital decoders are equipped with downmixing

Downmixing

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...

to distribute encoded channels to speakers. This includes such functions as playing surround information through the front speakers if surround speakers are unavailable, and distributing the center channel

Center channel

Center channel refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or fully, dedicated to the reproduction of the dialogue of an audiovisual program...

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.

Applications

Dolby Digital audio is 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 system is used in 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. Thirty-five millimeter film prints use a fixed rate of 320 kbit/s, which is the same as the maximum bit rate for 2-channel MP3

MP3

MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

. 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). HD DVD limits AC-3 to 448 kbit/s. ATSC and digital cable standards limit AC-3 to 448 kbit/s. Blu-ray Disc, the PlayStation 3 and the Xbox game console can output an AC-3 signal at a full 640 kbit/s. Some Sony PlayStation 2 console games are able to output AC-3 standard audio as well, mostly during pre-rendered cutscenes though.

Dolby is part of a group of organizations involved in the development of AAC

Advanced Audio Coding

Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....

(Advanced Audio Coding), part of MPEG specifications, and considered the successor to MP3. AAC outperforms MP3 at any bitrate, but is more complex.

Dolby Digital Plus (DD-Plus) and TrueHD are supported in HD DVD, as mandatory codecs, and in Blu-ray Disc, as optional codecs.

Dolby technologies in packaged media formats

HD DVD HD DVD HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...			Blu-ray Disc Blu-ray Disc Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...			DVD-Video DVD-Video DVD-Video is a consumer video format used to store digital video on DVD discs, and is currently the dominant consumer video format in Asia, North America, Europe, and Australia. Discs using the DVD-Video specification require a DVD drive and a MPEG-2 decoder...			DVD-Audio DVD-Audio DVD-Audio is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos....			Laserdisc Laserdisc LaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...
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	5.1	448 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 Dolby Digital Plus Dolby Digital Plus is a digital audio compression scheme. It is an incompatible development of the technologies used in the earlier Dolby Digital system. E-AC-3 has a number of improvements aimed at increasing quality at a given bitrate compared with legacy Dolby Digital...		7.1	3 Mbit/s	Optional	7.1	1.7 Mbit/s	N/A
Dolby TrueHD Dolby TrueHD Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc and HD DVD. It is the successor to the AC-3 Dolby Digital surround sound codec which was used as the...		8	18 Mbit/s	Optional	8	18 Mbit/s	N/A

Technical details

The data layout of AC-3 is described by simplified "C

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

-like" language in official specifications. An AC-3 stream is a series of frames; each with a fixed number of 6 audio blocks; each audio block contains 256 audio samples per channel. For example, a 5.1 AC-3 bitstream contains 1536 samples per audio block (6 channels × 256 samples/channel). Channel blocks can be either long, in which case the entire block is processed as single modified discrete cosine transform

Modified discrete cosine transform

The modified discrete cosine transform is a Fourier-related transform based on the type-IV discrete cosine transform , with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset,...

or short, in which case two half length transforms are performed on the block. Below is a simplified AC-3 header. A detailed description is in the ATSC "Digital Audio Compression (AC-3) (E-AC-3) Standard", section 5.4.

Field Name	# of bits	Description
syncword Syncword In computer networks, a syncword, sync character or preamble is used to synchronize a transmission by indicating the end of header information and the start of data.-Examples:For example an audio receiver is receiving a bit stream of data...	16	0x0B77 Transmission of data is left bit first (big endian).
CRC Cyclic redundancy check A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...	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.

liba52

A free ATSC A/52 stream decoder, liba52, is available under the GPL license.

External links

Dolby Laboratories
ATSC standards
Digital Audio Compression Standard (AC-3, E-AC-3) at the ATSC website

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Dolby Digital in the cinema

Versions

Dolby Digital

Dolby Digital EX

Dolby Digital Surround EX

Dolby Digital Live

Dolby Digital Plus

Dolby TrueHD

Channel configurations

Applications

Dolby technologies in packaged media formats

Technical details

liba52

See also

External links