Dolby Digital

Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. Originally named Dolby Stereo Digital until 1994, 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; today, it is now also used for other applications such as TV broadcast, radio broadcast via satellite, digital video streaming, DVDs, Blu-ray discs and game consoles.

Dolby-Digital
Dolby Digital logo

In the cinema

Batman Returns was the first film to use Dolby Digital technology when it premiered in theaters in the summer of 1992.[1] Dolby Digital 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 constant bit rate of 320 kbit/s is used. A charge-coupled device (CCD) scanner in the image 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. The data is then decoded into a 5.1 channel audio source. All film prints with Dolby Digital data also have Dolby Stereo 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 data area 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 may also include SDDS data and a timecode track to synchronize CD-ROMs carrying DTS soundtracks.

Dolby Digital track reader
A Dolby Digital Penthouse Soundhead mounted on a mid-1950s vintage Kalee model 20 projector
35mm film audio macro
A photo of a 35 mm film print featuring all four audio formats (or quad track)- from left to right: Sony Dynamic Digital Sound (SDDS) (blue area to the left of the sprocket holes), Dolby Digital (grey area between the sprocket holes labelled with the Dolby Double-D logo in the middle), analog optical sound (the two white lines to the right of the sprocket holes), and the DTS time code (the dashed line to the far right.)

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 data is recorded 26 frames ahead of the picture. If a penthouse soundhead is used, 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 10.4 ms).

As of 2019, Dolby Digital in film sound mixing is being gradually replaced with Dolby Surround 7.1, with the more advanced Dolby Atmos technology also gaining in popularity. While majority of movie theaters currently utilize Dolby Digital, virtually all films released today are mixed in Dolby Surround 7.1 and Dolby Atmos.

Versions

Dolby Digital[2] has similar technologies, included in Dolby Digital EX,[3] Dolby Digital Live,[4] Dolby Digital Plus,[5] Dolby Digital Surround EX,[6] Dolby Digital Recording,[7] Dolby Digital Cinema,[8] Dolby Digital Stereo Creator[9] and Dolby Digital 5.1 Creator.[10]

Dolby Digital

Dolbytrailerdvd07
Dolby Digital logo that is sometimes shown at the start of broadcasts, feature films, and video games
Dolby Digital old logo
The former Dolby Digital logo

Dolby 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, center, left, right surround, left surround) and one channel (20 Hz – 120 Hz allotted audio) for the subwoofer driven low-frequency effects.[11] Mono and stereo modes are also supported. AC-3 supports audio sample-rates up to 48 kHz.

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 backronyms. Adaptive Transform Acoustic Coding 3 is a separate format developed by Sony.])[12]
  • ATSC A/52 (name of the standard)[13]
  • Before 1996, was marketed as Dolby Surround AC-3, Dolby Stereo Digital, and Dolby SRD.[14]

In 1991, a limited experimental release of Star Trek VI: The Undiscovered Country in Dolby Digital played in 3 US theatres.[14] In 1992, Batman Returns is the first movie to be released in Dolby Digital.[15][16] In 1995, the LaserDisc version of Clear and Present Danger featured the first home theater Dolby Digital mix, quickly followed by True Lies, Stargate, Forrest Gump, and Interview with the Vampire among others.[17][18]

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.

Dolby Digital Surround EX

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 a Dolby Digital Surround EX audio option.

The cinema version of Dolby Digital EX was introduced in 1999, when Dolby and Skywalker Sound, a division of Lucasfilm Ltd., codeveloped Dolby Digital Surround EX™ for the release of Star Wars: Episode I – The Phantom Menace.[15][19] 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.[19]

Dolby Near
A Dolby home theater badge on a laptop

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 cable.[20] A similar technology known as DTS Connect is available from competitor DTS. 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 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 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, used for the Xbox game console and certain nForce2 motherboards, used an early form of this technology. DDL is available on motherboards with codecs such as Realtek's ALC882D,[21] ALC888DD and ALC888H. Other examples include some C-Media PCI sound cards and Creative Labs' X-Fi and Z series sound cards, whose drivers have enabled support for DDL.

NVIDIA later decided to drop DDL support in their motherboards due to the cost of involved royalties, leaving an empty space in this regard in the sound cards market. Then in June 2005 came Auzentech, which with its X-Mystique PCI card, provided the first consumer sound card with Dolby Digital Live support.

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 incapable 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.[22] 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.

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 incapable of DDL in hardware). X-Fi's case differs.

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.[23]

Creative Labs alleged Kawakami violated their intellectual property and demanded he cease distributing his modified drivers. [24][25][26]

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.[22] 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 added cost.[27]

Dolby Digital Plus

E-AC-3 (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 even more audio channels (up to 15.1 discrete channels[28] in the future), 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 codecs generally are capable of transcoding to AC-3 for equipment connected via S/PDIF. E-AC-3 decoders can also decode AC-3 bitstreams. The fourth generation Apple TV supports E-AC-3.[29] The discontinued HD DVD system directly supported E-AC-3. 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.

Dolby AC-4

Dolby AC-4 is an audio compression standard supporting multiple audio channels and/or audio objects. Support for 5.1 channel audio is mandatory and additional channels up to 7.1.4 are optional.[30] AC-4 provides a 50% reduction in bit rate over AC-3/Dolby Digital Plus.[30]

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 bit depths and sample rates up to 192 kHz. Maximum bitrate is 18 MBit/s while it supports up to 16 audio 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:

  • Dolby Digital 1/0 - Mono (center only)
  • Dolby Digital 2/0 - 2-channel stereo (left + right), optionally carrying matrixed Dolby Surround
  • Dolby Digital 3/0 - 3-channel stereo (left, center, right)
  • Dolby Digital 2/1 - 2-channel stereo with mono surround (left, right, surround)
  • Dolby Digital 3/1 - 3-channel stereo with mono surround (left, center, right, surround)
  • Dolby Digital 2/2 - 4-channel quadraphonic (left, right, left surround, right surround)
  • Dolby Digital 3/2 - 5-channel surround (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 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 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. 35mm film prints use a fixed rate of 320 kbit/s, which is the same as the maximum bit rate for 2-channel MP3. 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, primarily during pre-rendered cutscenes.

Dolby is 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.

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 Blu-ray Disc DVD-Video 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 5.1 504 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 7.1 3 Mbit/s Optional 7.1 1.7 Mbit/s
N/A
Dolby TrueHD 7.1 18 Mbit/s 7.1 18 Mbit/s

Technical details

The data layout of AC-3 is described by simplified "C-like" language in official specifications. An AC-3 stream is a series of frames; The frame size code is used along with the sample rate code to determine the number of (2-byte) words before the next syncword. Channel blocks can be either long, in which case the entire block is processed as single modified discrete cosine transform 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 16 0x0B77, data transmission is left bit first: big endian
Cyclic redundancy check 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.

License

Audio codec AC3 is covered by patents (though these are now expired[31]). Patents are used to ask to pay a commercial license to publish an application that decodes AC3. This leads some audio app developers to ban AC3 from their apps, although the open source VLC media player supports AC-3 audio without having paid for any kind of patent license.[32]

In Dolby's 2005 original and amended S-1 filings with the SEC, Dolby acknowledged that "Patents relating to our Dolby Digital technologies expire between 2008 and 2017."[33][34][35]

The last patent covering AC-3 expired March 20, 2017, so it is now generally free to use.[36]

See also

References

  1. ^ "COMPANY NEWS: A Sound Idea; Dolby Theater Format Adapted to Home Uses". The New York Times.
  2. ^ "Dolby - Dolby Digital Details". Dolby Laboratories.
  3. ^ "Dolby - What is Dolby Digital EX?". Dolby Laboratories.
  4. ^ "Dolby - What is Dolby Digital Live?". Dolby Laboratories.
  5. ^ "Dolby - Dolby Digital Plus Details". Dolby Laboratories.
  6. ^ "Dolby - What is Dolby Digital Surround EX?". Dolby Laboratories.
  7. ^ "Dolby - What is Dolby Digital Recording?". Dolby Laboratories.
  8. ^ "Dolby - Dolby Digital Cinema Details". Dolby Laboratories.
  9. ^ "Dolby - Dolby Digital Stereo Creator Details". Dolby Laboratories.
  10. ^ "Dolby - What is Dolby Digital 5.1 Creator?". Dolby Laboratories.
  11. ^ "Dolby-Frequently Asked Questions" (PDF). Dolby Laboratories.
  12. ^ "Sony USA". Sony.
  13. ^ "A/52B: Digital Audio Compression (AC-3) (E-AC-3) Standard, Rev. B". Advanced Television Systems Committee.
  14. ^ a b "Movie Sound Chronology". spannerworks.net. Retrieved 2017-04-02.
  15. ^ a b "History: 50 YEARS OF INNOVATION". Dolby Laboratories. Retrieved 2017-03-22.
  16. ^ "`Batman Returns` To Try Double Dolby". The Chicago Tribune. May 13, 1992. Retrieved 2017-03-22.
  17. ^ "Laserdisc Database Search By Date". Laserdisc Database. Retrieved 2017-04-02.
  18. ^ "LaserDisc Database Clear and Present Danger". LaserDisc Database. Retrieved 2017-04-02.
  19. ^ a b "Dolby Launches Dolby Digital Cinema in Theatres Worldwide with Star Wars Episode III: Revenge of the Sith". Dolby Investor Relations. Retrieved 2017-03-22.
  20. ^ "Dolby Digital Live". Dolby Laboratories.
  21. ^ Key, Gary (June 8, 2006). "Nvidia nForce 500: Biostar and MSI Aim for the Gold". AnandTech.
  22. ^ a b "A Korean reply comment (the fifth), which explains Dolby license royalty issue of X-Fi. Since the information leaked from SoundPrime, the Korean partner of Auzentech, all sources about this information are Korean".
  23. ^ "What Daniel_K wrote to the public is "This utility was written from scratch and does not contain any copyrighted code. Creative's director of developer relations, George Thorn told me, in a chat session, that is OK to provide mods as patches. It does not modify any executable or DLL, so it is NOT a crack." Daniel_K's driver MOD itself did not include any DDL module, until it began to support Creative's official DDL pack. Daniel_K's 'DDLUnlocker.exe' merely used disguise to install Auzentech Prelude DDL module".
  24. ^ Beschizza, Rob (April 1, 2008). "Daniel_K, Who Fixed Creative's Broken Vista Drivers, Speaks Out". Wired.com.
  25. ^ "There is BrokenBlaster blame about CL - Creative Labs, its much later than the issue but show common case who blame Creative Labs and admire Daniel_K". Creative Technology.
  26. ^ Beschizza, Rob (March 31, 2008). "Silence From Sound Card Maker After Customer Revolt". Wired.
  27. ^ "Dolby Digital Live pack, its DDL pack but also say "Get DTS Connect Pack FREE! for every purchase of Dolby Digital Live Pack."". Creative Technology.
  28. ^ "Dolby Digital Plus Audio Coding Tech Paper" (PDF).
  29. ^ "Apple TV - Tech Specs". Retrieved 1 January 2017.
  30. ^ a b "Dolby AC-4: Audio Delivery for Next-Generation Entertainment Services" (PDF). Dolby Laboratories. 2015-06-01. Retrieved 2016-04-26.
  31. ^ https://ac3freedomday.org/
  32. ^ VideoLAN. "VideoLAN - VLC - Features". Retrieved 1 January 2017.
  33. ^ "SEC Form S-1". ADOBE investor relations website. Retrieved 2017-03-22.
  34. ^ "SEC Form S-1". United States Securities and Exchange Commission (SEC) EDGAR system, filed November 19, 2004. Retrieved 2017-03-22.
  35. ^ "Amendment No. 1 to SEC Form S-1". United States Securities and Exchange Commission (SEC) EDGAR system, amended February 12, 2005. Retrieved 2017-03-22.
  36. ^ "The last patent on AC-3 (Dolby Digital) expires at midnight | Hacker News". news.ycombinator.com. Retrieved 2017-05-06.

External links

5.1 surround sound

5.1 surround sound ("five-point one") is the common name for six channel surround sound audio systems. 5.1 is the most commonly used layout in home theatre. It uses five full bandwidth channels and one low-frequency effects channel (the "point one"). Dolby Digital, Dolby Pro Logic II, DTS, SDDS, and THX are all common 5.1 systems. 5.1 is also the standard surround sound audio component of digital broadcast and music.All 5.1 systems use the same speaker channels and configuration, having a front left and right, a center channel, two surround channels and the low-frequency effects channel designed for a subwoofer.

Cinema Digital Sound

Cinema Digital Sound (CDS) was a multi-channel surround sound format used for theatrical films in the early 1990s. The system was developed by Eastman Kodak and Optical Radiation Corporation. CDS was quickly superseded by Digital Theatre System (DTS) and Dolby Digital formats.

CDS format replaced the analogue audio tracks on 35mm and 70mm prints with 5.1 discrete audio. The 5.1 tracks were encoded using 16-bit PCM audio in a delta modulation compression which resulted in a compression level of 4:1. The audio channels in CDS were arranged in the same way that most current 5.1 systems with Left, Center, Right, Left Surround, Right Surround and LFE. Not all films with CDS soundtracks used all 5.1 channels with some, such as Edward Scissorhands, using only the 4 channels that were supported by Dolby Stereo. Universal Soldier was the last film encoded with CDS.

The digital information was printed on the film, similar to Dolby Digital and SDDS. However, unlike those formats, there was no analog optical backup in 35mm and no magnetic backup in 70mm, meaning that if the digital information were damaged in some way, there would be no sound at all. This was one of the factors that contributed to its inevitable demise; the then-new Dolby Digital format moved its information to another area (in between the film sprocket holes), preserving the optical tracks.

DTS (sound system)

DTS, Inc. (originally Digital Theater Systems) is an American company that makes multichannel audio technologies for film and video. Based in Calabasas, California, the company introduced its DTS technology in 1993 as a higher-quality competitor to Dolby Laboratories, incorporating DTS in the film Jurassic Park. The DTS product is used in surround sound formats for both commercial/theatrical and consumer-grade applications. It was known as The Digital Experience until 1995. DTS licenses its technologies to consumer electronics manufacturers.

The DTS brand was bought by Tessera in December 2016, then Tessera changed its name to Xperi.

Dolby Digital Plus

Dolby Digital Plus, also known as Enhanced AC-3 (and commonly abbreviated as DD+ or E-AC-3, or EC-3) is a digital audio compression scheme developed by Dolby Labs for transport and storage of multi-channel digital audio. It is a successor to Dolby Digital (AC-3), also developed by Dolby, and has a number of improvements including support for a wider range of data rates (32 Kbit/s to 6144 Kbit/s), increased channel count and multi-program support (via substreams), and additional tools (algorithms) for representing compressed data and counteracting artifacts. While Dolby Digital (AC-3) supports up to 5 full-bandwidth audio channels at a maximum bitrate of 640 Kbit/s, E-AC-3 supports up to 15 full-bandwidth audio channels at a maximum bitrate of 6.144 Mbit/s.

The full set of technical specifications for E-AC-3 (and AC-3) are standardized and published in Annex E of ATSC A/52:2012, as well as Annex E of ETSI TS 102 366 V1.2.1 (2008–08), published by the Advanced Television Systems Committee.

Dolby Laboratories

Dolby Laboratories, Inc. (often shortened to Dolby Labs and known simply as Dolby) is an American company specializing in audio noise reduction and audio encoding/compression. Dolby licenses its technologies to consumer electronics manufacturers.

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 developed by Dolby in 1976 for analog cinema sound systems. The format was adapted for home use in 1982 as Dolby Surround when HiFi capable consumer VCRs were introduced. It was replaced by the improved Pro-Logic system in 1987.

The term "Dolby Surround" describes the encoding technology or matrix-encoded soundtrack, whereas Pro Logic refers to the decoding technology and processor.

The two technologies are mostly identical but a change in marketing was needed so as not to confuse cinema stereo which is at least four channels of audio with home stereo which is only two.

Dolby Surround/Pro Logic is based on matrix technology. When a Dolby Surround soundtrack is created, four channels of sound are matrix-encoded into an ordinary stereo (two channel) sound track. The centre channel is encoded by placing it equally in the left and right channels; the rear channel is encoded using phase shift techniques, typically an out of phase stereo mixdown.

A Pro Logic decoder/processor "unfolds" the sound into the original 4.0 surround—left and right, center, and a single limited frequency-range (7 kHz low-pass filtered) mono rear channel—while systems lacking the decoder play back the audio as standard stereo.

Although Dolby Surround was introduced as an analog format, all Dolby Digital decoders incorporate a digitally implemented Dolby Surround Pro Logic decoder for digital stereo signals that carry matrix-encoded Dolby Surround. One of the first was the MSP400 surround sound receiver and amplifier by RCA for their high-end Dimensia brand. It was released in 1987 for the Digital Command Component System.

Dolby Surround 7.1

Dolby Surround 7.1 is a sound system by Dolby Laboratories which delivers theatrical 7.1 surround sound to movie-goers. It adds two new channels to current Dolby Digital 5.1. The first film to feature Dolby Surround 7.1 was 2010's Toy Story 3 by Disney and Pixar. While most theaters worldwide today, still exhibit mainly in Dolby Digital; virtually every film that is released, as of May 2018, is mixed into Dolby Surround 7.1; while some films are adopting more Dolby Atmos mixes. Dolby 7.1, is mainly exhibited in premium large-screen formats, such as AMC ETX, Cinemark XD, and Dolby Cinema. As James Cameron's Avatar 2 is slated for release on December 18, 2020, it will be solely released in Dolby Cinema, Dolby Atmos and Dolby Surround 7.1; becoming the first film not to have a Dolby Digital soundtrack. Movie theaters will also replace most Dolby Digital sound systems with Dolby Surround 7.1 systems.

Dolby TrueHD

Dolby TrueHD is a lossless multi-channel audio codec developed by Dolby Laboratories which is used in home-entertainment equipment such as Blu-ray Disc players and A/V receivers. It is one of the successors to the Dolby Digital (AC-3) surround sound codec, which is used as the audio standard for the DVD-Video format. In this application, Dolby TrueHD competes with DTS-HD Master Audio, a lossless codec from DTS.

Dolby TrueHD uses Meridian Lossless Packing (MLP) as its mathematical basis for compressing audio samples. MLP is also used in the DVD-Audio format, but details of Dolby TrueHD and the MLP Lossless format as used on DVD-Audio differ substantially. A Dolby TrueHD bitstream can carry up to 16 discrete audio channels. Sample depths up to 24 bits/sample and audio sample rates up to 192 kHz are supported. Like the more common legacy codec Dolby Digital, Dolby TrueHD bitstreams carry program metadata. Metadata is separate from the coding format and compressed audio samples, but stores relevant information about the audio waveform and provides control over the decoding process. For example, dialog normalization and dynamic range compression are controlled by metadata embedded in the Dolby TrueHD bitstream. Similarly, a Dolby Atmos encoded Dolby TrueHD stream contains metadata to extract and place the objects in relevant positions. Dolby TrueHD is a variable bit-rate codec.

Genesis Movie Box 1981–2007

Genesis Movie Box 1981–2007 is a box set by Genesis which includes the following DVDs:

Three Sides Live (1981), released before on Betamax, VHS and LaserDisc only;

The Mama Tour (1984), released before on VHS and LaserDisc only; featuring "The Making of the Mama Album", a home video filmed by Phil Collins during the making of Genesis.

Live at Wembley Stadium (1987);

The Way We Walk - Live in Concert (1992),

bonus disc containing an updated version of a VH1 Behind The Music documentary about Genesis, which originally aired in 1999, all containing new 2009 5.1 mixes in DTS and Dolby Digital.The box also has an empty jewel case to hold the discs of When in Rome 2007.

List of HD channels in India

Template:Se Indian English

This is a list of High Definition channels in India.

List of SpongeBob SquarePants merchandise

This is a list of SpongeBob SquarePants merchandise, including home videos and DVDs, CDs, video games, and books.

List of cinemas in Metro Manila

This is a list of cinemas that exist or have existed in Metro Manila, Philippines.

MPEG Multichannel

MPEG Multichannel is an extension to the MPEG-1 Layer II audio compression specification, as defined in the MPEG-2 Audio standard (ISO/IEC 13818-3) which allows it provide up to 5.1-channels (surround sound) of audio. To maintain backwards compatibility with the older 2-channel (stereo) audio specification, it uses a channel matrixing scheme, where the additional channels are mixed into the two backwards compatible channels. Extra information in the data stream (ignored by older hardware) contains signals to process extra channels from the matrix.It was originally a mandatory part of the DVD specification for European DVDs, but was dropped in late 1997, and is rarely used as a result.

The Super Video CD (SVCD) standard supports MPEG Multichannel. Player support for this audio format is nearly non-existent however, and it is rarely used.

MPEG Multichannel audio was proposed for use in the ATSC digital TV broadcasting standard, but Dolby Digital (aka. AC-3, A/52) was chosen instead. This is a matter of significant controversy, as it has been revealed that the organizations (The Massachusetts Institute of Technology and Zenith Electronics) behind 2 of the 4 voting board members received tens of millions of dollars of compensation from secret deals with Dolby Laboratories in exchange for their votes.MPEG Multichannel–compatible equipment would bear either the MPEG Multichannel or MPEG Empowered logos.

Mother Earth Tour

Mother Earth Tour is Dutch metal band Within Temptation's first live DVD. It was released as a double DVD, including a live CD with the track list of the first DVD. The first disc features a live concert with footage from the 2002 rock festivals Rock Werchter, Pukkelpop and Lowlands.

Songs from this live DVD were also used in singles, and special editions of Mother Earth.

The video album was a winner of the 2003 Dutch Edison Award and reached Gold status in the Netherlands.The DVD was released with three audio options: 5.1 Dolby Digital; 2.0 Dolby Digital; DTS.

Movie projector

A movie projector is an opto-mechanical device for displaying motion picture film by projecting it onto a screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras.

River Cottage

River Cottage is a brand used for a number of ventures by television chef Hugh Fearnley-Whittingstall. These include a long-running Channel 4 television series, cookery courses, events, restaurants and products such as beer and yogurt.

TOSLINK

TOSLINK (from Toshiba Link) is a standardized optical fiber connector system. Also known generically as an "optical audio cable" or just "optical cable", its most common use is in consumer audio equipment (via a "digital optical" socket), where it carries a digital audio stream from components such as CD and DVD players, DAT recorders, computers, and modern video game consoles, to an AV receiver that can decode two channels of uncompressed lossless PCM audio or compressed 5.1/7.1 surround sound such as Dolby Digital or DTS Surround System. Unlike HDMI, TOSLINK does not have the bandwidth to carry the lossless versions of Dolby TrueHD, DTS-HD Master Audio, or more than two channels of PCM audio.

Although TOSLINK supports several different media formats and physical standards, digital audio connections using the rectangular EIAJ/JEITA RC-5720 (also CP-1201 and JIS C5974-1993 F05) connector are by far the most common. The optical signal is a red light with a peak wavelength of 650 nm. Depending on the type of modulated signal being carried, other optical wavelengths may be present.

The Videos 1994–2001

The Videos 1994–2001 is a music video compilation by the Dave Matthews Band, released on August 21, 2001 on VHS and DVD. The compilation features all of the band's 12 music videos from their first four albums, from "What Would You Say" to "The Space Between", with the earliest released in 1995, contrary to the compilation's title. Each video features a Dolby Digital stereo and 5.1 surround sound mix, as well as an audio commentary by the video's director. The compilation also features a behind-the-scenes documentary for "Don't Drink the Water", "Stay (Wasting Time)", and "I Did It".

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