Grand Alliance (HDTV)

Last updated

The Grand Alliance (GA) 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 Corporation, General Instrument Corporation, Massachusetts Institute of Technology, Philips Consumer Electronics, David Sarnoff Research Center, Thomson Consumer Electronics, and Zenith Electronics Corporation. The Grand Alliance's DTV system is the basis for the ATSC standard.

Recognizing that earlier proposed systems demonstrated particular strengths in the FCC's 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 MUSICAM 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 MUSICAM originally faltering during GA testing, the GA issued a statement finding the MPEG-2 audio system to be "essentially equivalent" to Dolby, but only after the Dolby selection had been made. [1] Later, a story emerged that MIT had entered into an agreement with Dolby whereupon the university would be awarded a large sum if the MUSICAM system was rejected. [2] 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. [2] Dolby also offered an incentive for Zenith to switch their vote (which they did), however it is unknown whether they accepted the offer. [2]

Grand Alliance Chronology

Related Research Articles

<span class="mw-page-title-main">MPEG-2</span> Video encoding standard

MPEG-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 bandwidth. While MPEG-2 is not as efficient as newer standards such as H.264/AVC and H.265/HEVC, backwards compatibility with existing hardware and software means it is still widely used, for example in over-the-air digital television broadcasting and in the DVD-Video standard.

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.

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 (MP3). While MP3 is much more popular for PC and Internet applications, MP2 remains a dominant standard for audio broadcasting.

DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in February, 1998. This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing modulation. It is also the format widely used worldwide for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point. It is also used in the US by Amateur television operators.

<span class="mw-page-title-main">ATSC standards</span> Standards for digital television in the US

Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States, Mexico, Canada, South Korea and Trinidad & Tobago. Several former NTSC users, such as Japan, have not used ATSC during their digital television transition, because they adopted other systems such as ISDB developed by Japan, and DVB developed in Europe, for example.

Digital cable is the distribution of cable television using digital data and video compression. The technology was first developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previous analog-based cable by the mid 2010s. During the late 2000s, broadcast television converted to the digital HDTV standard, which was incompatible with existing analog cable systems.

Broadcasttelevision systems are the encoding or formatting systems for the transmission and reception of terrestrial television signals.

High-definition television (HDTV) in the United States was introduced in 1998 and has since become increasingly popular and dominant in the television market. Hundreds of HD channels are available in millions of homes and businesses both terrestrially and via subscription services such as satellite, cable and IPTV. HDTV has quickly become the standard, with about 85% of all TVs used being HD as of 2018. In the US, the 720p and 1080i formats are used for linear channels, while 1080p is available on a limited basis, mainly for pay-per-view and video on demand content. Some networks have also began transmitting content at 1080p via ATSC 3.0 multiplex channels, with CBS and NBC affiliates being the main stations that transmit at 1080p.

QAM is a digital television standard using quadrature amplitude modulation. It is the format by which digital cable channels are encoded and transmitted via cable television providers. QAM is used in a variety of communications systems such as Dial-up modems and WiFi. In cable systems, a QAM tuner is linked to the cable in a manner that is equivalent to an ATSC tuner which is required to receive over-the-air (OTA) digital channels broadcast by local television stations when attached to an antenna. Most new HDTV digital televisions support both of these standards. QAM uses the same 6 MHz bandwidth as ATSC, using a standard known as ITU-T Recommendation J.83 Annex B ("J.83b").

<span class="mw-page-title-main">ATSC tuner</span> Tuner for digital television channels

An ATSCtuner, often called an ATSC receiver or HDTV tuner, is a type of television tuner that allows reception of digital television (DTV) television channels that use ATSC standards, as transmitted by television stations in North America, parts of Central America, and South Korea. Such tuners are usually integrated into a television set, VCR, digital video recorder (DVR), or set-top box which provides audio/video output connectors of various types.

HD Lite is the re-transmission of a particular HDTV channel at reduced picture quality compared to the original source stream.

MPEG Multichannel, also known as MPEG-2 Backwards Compatible, or MPEG-2 BC, is an extension to the MPEG-1 Layer II audio compression specification, as defined in the MPEG-2 Audio standard which allows it provide up to 5.1-channels 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 contains signals to process extra channels from the matrix.

E-VSB or Enhanced VSB is an optional enhancement to the original ATSC Standards that use the 8VSB modulation system used for transmission of digital television. It is intended for improving reception where signals are weaker, including fringe reception areas, and on portable devices such as handheld televisions or mobile phones. It does not cause problems to older receivers, but they cannot take advantage of its features. E-VSB was approved by the ATSC committee in 2004. However, it has been implemented by few stations or manufacturers.

ATSC-M/H is a U.S. standard for mobile digital TV that allows TV broadcasts to be received by mobile devices.

Digital television in the United States is available via digital terrestrial television (DTT), digital cable, satellite television, and IPTV providers.

High-definition television (HDTV) describes a television or video system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since at least 1933; in more recent times, it refers to the generation following standard-definition television (SDTV). It is the current de facto standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television.

ATSC 3.0 is a major version of the ATSC standards for television broadcasting created by the Advanced Television Systems Committee (ATSC).

MPEG-H 3D Audio, specified as ISO/IEC 23008-3, is an audio coding standard developed by the ISO/IEC Moving Picture Experts Group (MPEG) to support coding audio as audio channels, audio objects, or higher order ambisonics (HOA). MPEG-H 3D Audio can support up to 64 loudspeaker channels and 128 codec core channels.

Dolby AC-4 is an audio compression technology developed by Dolby Laboratories. Dolby AC-4 bitstreams can contain audio channels and/or audio objects. Dolby AC-4 has been adopted by the DVB project and standardized by the ETSI.

References

  1. ↑ Cianci, Philip (2012), High Definition Television: The Creation, Development and Implementation of HDTV Technology, McFarland & Company, ISBN   978-0786449750
  2. 1 2 3 MIT Getting Millions For Digital TV Deal
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.