Grand Alliance (HDTV)
Encyclopedia
The Grand Alliance was a consortium
created in 1993 at the behest of the Federal Communications Commission
(FCC) to develop the American digital television
(SDTV
, EDTV
) and HDTV
specification, with the aim of pooling the best work from different companies. It consisted of AT&T
, General Instrument Corporation
, Massachusetts Institute of Technology
, Philips Consumer Electronics
, David Sarnoff Research Center, Thomson Consumer Electronics
, and Zenith Electronics Corporation
. The Grand Alliance DTV
system is the basis for the ATSC standard.
Recognizing that earlier proposed systems demonstrated particular strengths in the Advisory Committee on Advanced Television Service (ACATS) testing and evaluation process, the Grand Alliance system was proposed to combine the
advantages of all of the previously proposed terrestrial digital HDTV systems. At the time of its inception, the Grand Alliance HDTV system was specified to include:
Audio and transmission systems had not been decided at the time of the GA agreement. Five channel audio was specified, but a decision among the Dolby AC-3
, multi-channel MPEG-1 Audio Layer II
(MP2) audio, and MIT "AC" systems had not yet been made. Candidate transmission approaches included QAM
, Spectrally-Shaped QAM, 6 VSB (with trellis code
) and 4/2 VSB. COFDM had been proposed by third parties, but was rejected as not being mature, and not offering fringe-area coverage equivalent to analog transmission. A thorough analysis of service area, interference characteristics, transmission robustness and system attributes would be performed to determine the "best approach."
In the end, 1080, 720 and 480-line resolutions were implemented at various aspect ratios and frame rates, with progressive and interlaced scanning (the so-called "18 formats"), together with 8-VSB
modulation and Dolby AC-3 audio. However, the selection of transmission and audio systems was not without controversy. The choice of 8-VSB was later criticised by several groups as being inferior to COFDM under conditions of multipath interference
. Improvements in receiver designs would later render this apparently moot. With MP2 originally faltering during GA testing, the GA issued a statement finding the MP2 system to be "essentially equivalent" to Dolby, but only after the Dolby selection had been made. Later, a story emerged that MIT had entered into an agreement with Dolby whereupon the university would be awarded a large sum if the MP2 system was rejected. Following a five-year lawsuit for breach of contract, MIT and its GA representative received a total of $30 million from Dolby, after the litigants reached a last-minute out-of-court settlement. Dolby also offered an incentive for Zenith to switch their vote (which they did), however it is unknown whether they accepted the offer.
Consortium
A consortium is an association of two or more individuals, companies, organizations or governments with the objective of participating in a common activity or pooling their resources for achieving a common goal....
created in 1993 at the behest of the Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC) to develop the American digital television
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
(SDTV
Standard-definition television
Sorete-definition television is a television system that uses a resolution that is not considered to be either enhanced-definition television or high-definition television . The term is usually used in reference to digital television, in particular when broadcasting at the same resolution as...
, EDTV
Enhanced-definition television
Enhanced-definition television, or extended-definition television, is a United States Consumer Electronics Association marketing shorthand term for certain digital television formats and devices...
) and HDTV
High-definition television
High-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD...
specification, with the aim of pooling the best work from different companies. It consisted of AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
, General Instrument Corporation
General Instrument
General Instrument was an electronics manufacturer based in Horsham, PA specializing in semiconductors and cable television equipment. The company was active until 1997, when it split into which was later acquired by Vishay Intertechnology in 2001, CommScope and NextLevel Systems General...
, Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
, Philips Consumer Electronics
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
, David Sarnoff Research Center, Thomson Consumer Electronics
Thomson SA
Technicolor SA , formerly Thomson SA and Thomson Multimedia, is a French international provider of solutions for the creation, management, post-production, delivery and access of video, for the Communication, Media and Entertainment industries. Technicolor’s headquarters are located in Issy les...
, and Zenith Electronics Corporation
Zenith Electronics
Zenith Electronics Corporation is a brand of the South Korean company LG Electronics. The company was previously an American manufacturer of televisions and other consumer electronics, and was headquartered in Lincolnshire, Illinois. LG Electronics acquired a controlling share of Zenith in 1995...
. The Grand Alliance DTV
Digital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
system is the basis for the ATSC standard.
Recognizing that earlier proposed systems demonstrated particular strengths in the Advisory Committee on Advanced Television Service (ACATS) testing and evaluation process, the Grand Alliance system was proposed to combine the
advantages of all of the previously proposed terrestrial digital HDTV systems. At the time of its inception, the Grand Alliance HDTV system was specified to include:
- Flexible picture formats with a header/ approach, allowing the inclusion of both 1050 and 787.5 raster formats.
- Progressive scanProgressive scanProgressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
ning and square pixelPixelIn digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
capabilities in both raster formats. - Interlaced scanning and rectangular pixel formats.
- Video compression based on MPEG-2MPEG-2MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods which permit storage and transmission of movies using currently available storage media and transmission...
, with additional syntax elements that represent contributions from each previously proposed system. - A packetized, prioritized data format, providing flexibility of services and extensibility.
Audio and transmission systems had not been decided at the time of the GA agreement. Five channel audio was specified, but a decision among the Dolby AC-3
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called 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...
, multi-channel MPEG-1 Audio Layer II
MPEG-1 Audio Layer II
MPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III...
(MP2) audio, and MIT "AC" systems had not yet been made. Candidate transmission approaches included QAM
Quadrature amplitude modulation
Quadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...
, Spectrally-Shaped QAM, 6 VSB (with trellis code
Trellis modulation
In telecommunication, trellis modulation is a modulation scheme which allows highly efficient transmission of information over band-limited channels such as telephone lines...
) and 4/2 VSB. COFDM had been proposed by third parties, but was rejected as not being mature, and not offering fringe-area coverage equivalent to analog transmission. A thorough analysis of service area, interference characteristics, transmission robustness and system attributes would be performed to determine the "best approach."
In the end, 1080, 720 and 480-line resolutions were implemented at various aspect ratios and frame rates, with progressive and interlaced scanning (the so-called "18 formats"), together with 8-VSB
8VSB
8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM....
modulation and Dolby AC-3 audio. However, the selection of transmission and audio systems was not without controversy. The choice of 8-VSB was later criticised by several groups as being inferior to COFDM under conditions of multipath interference
Multipath interference
Multipath interference is a phenomenon in the physics of waves whereby a wave from a source travels to a detector via two or more paths and, under the right condition, the two components of the wave interfere...
. Improvements in receiver designs would later render this apparently moot. With MP2 originally faltering during GA testing, the GA issued a statement finding the MP2 system to be "essentially equivalent" to Dolby, but only after the Dolby selection had been made. Later, a story emerged that MIT had entered into an agreement with Dolby whereupon the university would be awarded a large sum if the MP2 system was rejected. Following a five-year lawsuit for breach of contract, MIT and its GA representative received a total of $30 million from Dolby, after the litigants reached a last-minute out-of-court settlement. Dolby also offered an incentive for Zenith to switch their vote (which they did), however it is unknown whether they accepted the offer.
Grand Alliance Chronology
- 1987 - Advisory Committee on Advanced Television Service is formed
- 1990 - SimulcastSimulcastSimulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
principle advocated by the FCC - 1990 - Four competing digital HDTV systems announced
- 1992 - Systems tested at Advanced Television Test Center (ATTC)
- 1992 - All competitors announce planned improvements
- 1993 - ACATS Special Panel recommends retesting
- 1993 - Grand Alliance forms, "collaborative" phase begins
- 1994 - Grand Alliance system undergoes ATTC verification testing
- 1995 - ATSC Standard A/53 is published, incorporating Grand Alliance System
- 1996 - FCC Adopts ATSC A/53 as standard for the transmission of digital television, but excludes requirements with respect to scanning formats, aspect ratiosAspect ratio (image)The aspect ratio of an image is the ratio of the width of the image to its height, expressed as two numbers separated by a colon. That is, for an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this...
, and lines of resolutionImage resolutionImage resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail.... - 1997 - Academy of Television Arts & Sciences presents Primetime Engineering Emmy AwardEmmy AwardAn Emmy Award, often referred to simply as the Emmy, is a television production award, similar in nature to the Peabody Awards but more focused on entertainment, and is considered the television equivalent to the Academy Awards and the Grammy Awards .A majority of Emmys are presented in various...
to Grand Alliance companies for developing and standardizing the transmission and technology for digital TV.