Ultra high frequency
Ultra high frequency is the ITU designation for radio frequencies in the range between 300 megahertz and 3 gigahertz known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency or microwave frequency range. Lower frequency signals fall into lower bands. UHF radio waves propagate by line of sight, they are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, numerous other applications. The IEEE defines the UHF radar band as frequencies between 1 GHz. Two other IEEE radar bands overlap the ITU UHF band: the L band between 1 and 2 GHz and the S band between 2 and 4 GHz. Radio waves in the UHF band travel entirely by line-of-sight propagation and ground reflection. UHF radio waves are blocked by hills and cannot travel far beyond the horizon, but can penetrate foliage and buildings for indoor reception.
Since the wavelengths of UHF waves are comparable to the size of buildings, trees and other common objects and diffraction from these objects can cause fading due to multipath propagation in built-up urban areas. Atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, the attenuation increases with frequency. UHF TV signals are more degraded by moisture than lower bands, such as VHF TV signals. Since UHF transmission is limited by the visual horizon to 30–40 miles and to shorter distances by local terrain, it allows the same frequency channels to be reused by other users in neighboring geographic areas. Public safety, business communications and personal radio services such as GMRS, PMR446, UHF CB are found on UHF frequencies as well as IEEE 802.11 wireless LANs. The adopted GSM and UMTS cellular networks use UHF cellular frequencies. Radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required; when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day.
The length of an antenna is related to the length of the radio waves used. Due to the short wavelengths, UHF antennas are conveniently short. UHF wavelengths are short enough that efficient transmitting antennas are small enough to mount on handheld and mobile devices, so these frequencies are used for two way land mobile radio systems, such as walkie-talkies, two way radios in vehicles, for portable wireless devices. Omnidirectional UHF antennas used on mobile devices are short whips, sleeve dipoles, rubber ducky antennas or the planar inverted F antenna used in cellphones. Higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used for mobile base stations and cellular base station antennas; the short wavelengths allow high gain antennas to be conveniently small. High gain antennas for point-to-point communication links and UHF television reception are Yagi, log periodic, corner reflectors, or reflective array antennas. At the top end of the band slot antennas and parabolic dishes become practical.
For satellite communication and turnstile antennas are used since satellites employ circular polarization, not sensitive to the relative orientation of the transmitting and receiving antennas. For television broadcasting specialized vertical radiators that are modifications of the slot antenna or reflective array antenna are used: the slotted cylinder, zig-zag, panel antennas. UHF television broadcasting fulfilled the demand for additional over-the-air television channels in urban areas. Today, much of the bandwidth has been reallocated to land mobile, trunked radio and mobile telephone use. UHF channels are still used for digital television. UHF spectrum is used worldwide for land mobile radio systems for commercial, public safety, military purposes. Many personal radio services use frequencies allocated in the UHF band, although exact frequencies in use differ between countries. Major telecommunications providers have deployed voice and data cellular networks in UHF/VHF range; this allows mobile phones and mobile computing devices to be connected to the public switched telephone network and public Internet.
UHF radars are said to be effective at tracking stealth fighters, if not stealth bombers. UHF citizens band: 476–477 MHz Television broadcasting uses UHF channels between 503 and 694 MHz Fixed point-to-point Link 450.4875 - 451.5125 MHz Land mobile service 457.50625 - 459.9875 MHz Mobile satellite service: 406.0000 - 406.1000 MHz Segment and Service examples: Land mobile for private, Australian and Territory Government, Rail industry and Mobile-Satellite 430–450 MHz: Amateur radio 470–806 MHz: Terrestrial television 1452–1492 MHz: Digital Audio Broadcasting Many other frequency assignments for Canada and Mexico are similar to their US counterparts 380–399.9 MHz: Terrestrial Trunked Radio service for emergency use 430–440 MHz: Amateur ra
Texas is the second largest state in the United States by both area and population. Geographically located in the South Central region of the country, Texas shares borders with the U. S. states of Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the west, the Mexican states of Chihuahua, Nuevo León, Tamaulipas to the southwest, while the Gulf of Mexico is to the southeast. Houston is the most populous city in Texas and the fourth largest in the U. S. while San Antonio is the second-most populous in the state and seventh largest in the U. S. Dallas–Fort Worth and Greater Houston are the fourth and fifth largest metropolitan statistical areas in the country, respectively. Other major cities include Austin, the second-most populous state capital in the U. S. and El Paso. Texas is nicknamed "The Lone Star State" to signify its former status as an independent republic, as a reminder of the state's struggle for independence from Mexico; the "Lone Star" can be found on the Texan state seal.
The origin of Texas's name is from the word taysha. Due to its size and geologic features such as the Balcones Fault, Texas contains diverse landscapes common to both the U. S. Southern and Southwestern regions. Although Texas is popularly associated with the U. S. southwestern deserts, less than 10% of Texas's land area is desert. Most of the population centers are in areas of former prairies, grasslands and the coastline. Traveling from east to west, one can observe terrain that ranges from coastal swamps and piney woods, to rolling plains and rugged hills, the desert and mountains of the Big Bend; the term "six flags over Texas" refers to several nations. Spain was the first European country to claim the area of Texas. France held a short-lived colony. Mexico controlled the territory until 1836 when Texas won its independence, becoming an independent Republic. In 1845, Texas joined the union as the 28th state; the state's annexation set off a chain of events that led to the Mexican–American War in 1846.
A slave state before the American Civil War, Texas declared its secession from the U. S. in early 1861, joined the Confederate States of America on March 2nd of the same year. After the Civil War and the restoration of its representation in the federal government, Texas entered a long period of economic stagnation. Four major industries shaped the Texas economy prior to World War II: cattle and bison, cotton and oil. Before and after the U. S. Civil War the cattle industry, which Texas came to dominate, was a major economic driver for the state, thus creating the traditional image of the Texas cowboy. In the 19th century cotton and lumber grew to be major industries as the cattle industry became less lucrative, it was though, the discovery of major petroleum deposits that initiated an economic boom which became the driving force behind the economy for much of the 20th century. With strong investments in universities, Texas developed a diversified economy and high tech industry in the mid-20th century.
As of 2015, it is second on the list of the most Fortune 500 companies with 54. With a growing base of industry, the state leads in many industries, including agriculture, energy and electronics, biomedical sciences. Texas has led the U. S. in state export revenue since 2002, has the second-highest gross state product. If Texas were a sovereign state, it would be the 10th largest economy in the world; the name Texas, based on the Caddo word táyshaʼ "friend", was applied, in the spelling Tejas or Texas, by the Spanish to the Caddo themselves the Hasinai Confederacy, the final -s representing the Spanish plural. The Mission San Francisco de los Tejas was completed near the Hasinai village of Nabedaches in May 1690, in what is now Houston County, East Texas. During Spanish colonial rule, in the 18th century, the area was known as Nuevo Reino de Filipinas "New Kingdom of the Philippines", or as provincia de los Tejas "province of the Tejas" also provincia de Texas, "province of Texas", it was incorporated as provincia de Texas into the Mexican Empire in 1821, declared a republic in 1836.
The Royal Spanish Academy recognizes both spellings and Texas, as Spanish-language forms of the name of the U. S. State of Texas; the English pronunciation with /ks/ is unetymological, based in the value of the letter x in historical Spanish orthography. Alternative etymologies of the name advanced in the late 19th century connected the Spanish teja "rooftile", the plural tejas being used to designate indigenous Pueblo settlements. A 1760s map by Jacques-Nicolas Bellin shows a village named Teijas on Trinity River, close to the site of modern Crockett. Texas is the second-largest U. S. state, with an area of 268,820 square miles. Though 10% larger than France and twice as large as Germany or Japan, it ranks only 27th worldwide amongst country subdivisions by size. If it were an independent country, Texas would be the 40th largest behind Zambia. Texas is in the south central part of the United States of America. Three of its borders are defined by rivers; the Rio Grande forms a natural border with the Mexican states of Chihuahua, Nuevo León, Tamaulipas to the south.
The Red River forms a natural border with Arkansas to the north. The Sabine River forms a natural border with Louisiana to the east; the Texas Panhandle has an eastern border with Oklahoma at 100° W, a northern border with Oklahoma at 36°30' N and a western
Abilene is a city in Taylor and Jones counties in Texas, United States. The population was 117,463 at the 2010 census, making it the 27th-most populous city in the state of Texas, it is the principal city of the Abilene Metropolitan Statistical Area, which had a 2017 estimated population of 170,219. It is the county seat of Taylor County. Dyess Air Force Base is located on the west side of the city. Abilene is located between exits 279 on its western edge and 292 on the east. Abilene is 150 miles west of Fort Worth; the city is looped by I-20 to the north, US 83/84 on the west, Loop 322 to the east. A railroad divides the city down the center into south; the historic downtown area is on the north side of the railroad. Established by cattlemen as a stock shipping point on the Texas and Pacific Railway in 1881, the city was named after Abilene, the original endpoint for the Chisholm Trail; the T&P had bypassed the town of the county seat at the time. A landowner north of Buffalo Gap, Clabe Merchant, known as the father of Abilene, chose the name for the new town.
According to a Dallas newspaper, about 800 people had begun camping at the townsite before the lots were sold. The town was laid out by Colonel J. Stoddard Johnson, the auction of lots began early on March 15, 1881. By the end of the first day, 139 lots were sold for a total of $23,810, another 178 lots were sold the next day for $27,550. Abilene was incorporated soon after being founded in 1881, Abilenians began to set their sights on bringing the county seat to Abilene, in a three-to-one vote, won the election. In 1888, the Progressive Committee was formed to attract businesses to the area, which became the Board of Trade in 1890. By 1900, 3,411 people lived in Abilene, in that decade, the Board of Trade changed its name to the 25,000 Club in the hope of reaching 25,000 people by the next census. However, this committee failed when the population only hit 9,204 in 1910. Replacing it was the Young Men's Booster Club, which became the Abilene Chamber of Commerce in 1914; the cornerstone was laid for the first of three future universities in Abilene, called Simmons College, in 1891, which became Hardin–Simmons University.
Childers Classical Institute followed in 1906 Abilene Christian University, the largest of the three. In 1923, McMurry College was founded and became McMurry University. Much more Abilene succeeded in bringing Cisco Junior College and Texas State Technical College branches to Abilene, with the Cisco Junior College headquarters being located in Abilene. In 1940, Abilene raised the money to purchase land for a U. S. Army base, southwest of town, named Camp Barkeley, at the time twice the size of Abilene with 60,000 men; when the base closed, many worried that Abilene could become a ghost town, but in the post-World War II boom, many servicemen returned to start businesses in Abilene. In the early-1950s, residents raised $893,261 to purchase 3,400 acres of land for an Air Force base. Today, Dyess Air Force Base is the city's largest employer, with 6,076 employees. Abilene's population nearly doubled in 10 years from 45,570 in 1950 to 90,638. In the same year, a second high school was added, Cooper High School.
In 1966, the Abilene Zoo was created near Abilene Regional Airport. The following year, one of the most important bond elections in the city's history passed for the funding of the construction of the Abilene Civic Center and the Taylor County Coliseum, as well as major improvements to Abilene Regional Airport. In 1969, the Woodson elementary and high school for black students closed as the school system was integrated. In 1982, Abilene became the first city in Texas to create a downtown reinvestment zone. Texas State Technical College opened an Abilene branch three years later; the 2,250-bed French Robertson Prison Unit was built in 1989. A half-cent sales tax earmarked for economic development was created after the decline in the petroleum business in the 1980s. A branch of Cisco Junior College was located in the city in 1990; the Grace Museum and Paramount Theatre revitalizations, along with Artwalk in 1992, sparked a decade of downtown restoration. In 2004, Frontier Texas!, a multimedia museum highlighting the history of the area from 1780 to 1880, was constructed, a new $8 million, 38-acre Cisco Junior College campus was built at Loop 322 and Industrial Boulevard.
Subdivisions and businesses started locating along the freeway, on the same side as the CJC campus, showing a slow but progressive trend for Abilene growth on the Loop. Abilene has become the commercial, retail and transportation hub of a 19-county area more known as "The Big Country", but known as the "Texas Midwest", is part of the Central Great Plains ecoregion. By the end of 2005, commercial and residential development had reached record levels in and around the city. Abilene is located in northeastern Taylor County; the city limits extend north into Jones County. Interstate 20 leads west 148 miles to Midland. Three U. S. highways pass through the city. US 83 runs west of the city center, leading south 55 miles to Ballinger. US 84 runs with US 83 through the southwest part of the city but leads southeast 52 miles to Coleman and west with I-20 40 miles to Sweetwater. US 277 follows US 83 around the northwest side of the city and north to Anson but heads southwest from Abilene 89 miles so San Angelo.
According to the United States Census Bureau, Abilene has a total area of 112.2 square miles, of which 106.8 square miles are land and 5.4 square miles are covered by
Aspect ratio (image)
The aspect ratio of an image describes the proportional relationship between its width and its height. It is expressed as two numbers separated by a colon, as in 16:9. 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 same length unit, the height will be measured to be y units. For example, in a group of images that all have an aspect ratio of 16:9, one image might be 16 inches wide and 9 inches high, another 16 centimeters wide and 9 centimeters high, a third might be 8 yards wide and 4.5 yards high. Thus, aspect ratio concerns the relationship of the width to the height, not an image's actual size; the most common aspect ratios used today in the presentation of films in cinemas are 1.85:1 and 2.39:1. Two common videographic aspect ratios are 4:3, the universal video format of the 20th century, 16:9, universal for high-definition television and European digital television. Other cinema and video aspect ratios are used infrequently.
In still camera photography, the most common aspect ratios are 4:3, 3:2, more found in consumer cameras, 16:9. Other aspect ratios, such as 5:3, 5:4, 1:1, are used in photography as well in medium format and large format. With television, DVD and Blu-ray Disc, converting formats of unequal ratios is achieved by enlarging the original image to fill the receiving format's display area and cutting off any excess picture information, by adding horizontal mattes or vertical mattes to retain the original format's aspect ratio, by stretching the image to fill the receiving format's ratio, or by scaling by different factors in both directions scaling by a different factor in the center and at the edges. In motion picture formats, the physical size of the film area between the sprocket perforations determines the image's size; the universal standard is a frame, four perforations high. The film itself is 35 mm wide, but the area between the perforations is 24.89 mm × 18.67 mm, leaving the de facto ratio of 4:3, or 1.3:1.
With a space designated for the standard optical soundtrack, the frame size reduced to maintain an image, wider than tall, this resulted in the Academy aperture of 22 mm × 16 mm or 1.375:1 aspect ratio. The motion picture industry convention assigns a value of 1.0 to the image's height. After 1952, a number of aspect ratios were experimented with for anamorphic productions, including 2.66:1 and 2.55:1. A SMPTE specification for anamorphic projection from 1957 standardized the aperture to 2.35:1. An update in 1970 changed the aspect ratio to 2.39:1. This aspect ratio of 2.39:1 was confirmed by the most recent revision from August 1993. In American cinemas, the common projection ratios are 1.85:1 and 2.39:1. Some European countries have 1.6:1 as the wide screen standard. The "Academy ratio" of 1.375:1 was used for all cinema films in the sound era until 1953. During that time, which had a similar aspect ratio of 1.3:1, became a perceived threat to movie studios. Hollywood responded by creating a large number of wide-screen formats: CinemaScope, Todd-AO, VistaVision to name just a few.
The "flat" 1.85:1 aspect ratio was introduced in May 1953, became one of the most common cinema projection standards in the U. S. and elsewhere. The goal of these various lenses and aspect ratios was to capture as much of the frame as possible, onto as large an area of the film as possible, in order to utilize the film being used; some of the aspect ratios were chosen to utilize smaller film sizes in order to save film costs while other aspect ratios were chosen to use larger film sizes in order to produce a wider higher resolution image. In either case the image was squeezed horizontally to fit the film's frame size and avoid any unused film area. Development of various film camera systems must cater to the placement of the frame in relation to the lateral constraints of the perforations and the optical soundtrack area. One clever wide screen alternative, VistaVision, used standard 35 mm film running sideways through the camera gate, so that the sprocket holes were above and below frame, allowing a larger horizontal negative size per frame as only the vertical size was now restricted by the perforations.
There were a limited number of projectors constructed to run the print-film horizontally. However, the 1.50:1 ratio of the initial VistaVision image was optically converted to a vertical print to show with the standard projectors available at theaters, was masked in the projector to the US standard of 1.85:1. The format was revived by Lucasfilm in the late 1970s for special effects work that required larger negative size, it went into obsolescence due to better cameras and film stocks available to standard four-perforation formats, in addition to increased lab costs of making prints in comparison to more standard vertical processes. Super 16 mm film was used for televisi
In broadcasting and radio communications, a call sign is a unique designation for a transmitter station. In the United States of America, they are used for all FCC-licensed transmitters. A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or cryptographically encoded to disguise a station's identity; the use of call signs as unique identifiers dates to the landline railroad telegraph system. Because there was only one telegraph line linking all railroad stations, there needed to be a way to address each one when sending a telegram. In order to save time, two-letter identifiers were adopted for this purpose; this pattern continued in radiotelegraph operation. These were not globally unique, so a one-letter company identifier was added. By 1912, the need to identify stations operated by multiple companies in multiple nations required an international standard. Merchant and naval vessels are assigned call signs by their national licensing authorities.
In the case of states such as Liberia or Panama, which are flags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters. United States merchant vessels are given call signs beginning with the letters "W" or "K" while US naval ships are assigned call signs beginning with "N". Both ships and broadcast stations were assigned call signs in this series consisting of three or four letters. Ships equipped with Morse code radiotelegraphy, or life boat radio sets, Aviation ground stations, broadcast stations were given four letter call signs. Maritime coast stations on high frequency were assigned three letter call signs; as demand for both marine radio and broadcast call signs grew American-flagged vessels with radiotelephony only were given longer call signs with mixed letters and numbers. Leisure craft with VHF radios may not be assigned call signs, in which case the name of the vessel is used instead. Ships in the US still wishing to have a radio license are under FCC class SA: "Ship recreational or voluntarily equipped."
Those calls follow the land mobile format of the initial letter K or W followed by 1 or 2 letters followed by 3 or 4 numbers. U. S. Coast Guard small boats have a number, shown on both bows in which the first two digits indicate the nominal length of the boat in feet. For example, Coast Guard 47021 refers to the 21st in the series of 47-foot motor lifeboats; the call sign might be abbreviated to the final two or three numbers during operations, for example: Coast Guard zero two one. Aviation mobile stations equipped with radiotelegraphy were assigned five letter call signs.. Land Stations in Aviation were assigned four letter call signs; these call signs were phased out in the 1960s when flight radio officers were no longer required on international flights. USSR kept FRO's for the Moscow-Havana run until around 2000. All signs in aviation are derived from several different policies, depending upon the type of flight operation and whether or not the caller is in an aircraft or at a ground facility.
In most countries, unscheduled general aviation flights identify themselves using the call sign corresponding to the aircraft's registration number. In this case, the call sign is spoken using the International Civil Aviation Organization phonetic alphabet. Aircraft registration numbers internationally follow the pattern of a country prefix, followed by a unique identifier made up of letters and numbers. For example, an aircraft registered as N978CP conducting a general aviation flight would use the call sign November-niner-seven-eight-Charlie-Papa. However, in the United States a pilot of an aircraft would omit saying November, instead use the name of the aircraft manufacturer or the specific model. At times, general aviation pilots might omit additional preceding numbers and use only the last three numbers and letters; this is true at uncontrolled fields when reporting traffic pattern positions or at towered airports after establishing two-way communication with the tower controller. For example, Skyhawk eight-Charlie-Papa, left base.
In most countries, the aircraft call sign or "tail number"/"tail letters" are linked to the international radio call sign allocation table and follow a convention that aircraft radio stations receive call signs consisting of five letters. For example, all British civil aircraft have a five-letter call sign beginning with the letter G. Canadian aircraft have a call sign beginning with C–F or C–G, such as C–FABC. Wing In Ground-effect vehicles in Canada are eligible to receive C–Hxxx call signs, ultralight aircraft receive C-Ixxx call signs. In days gone by American aircraft used five letter call signs, such as KH–ABC, but they were replaced prior to World War II by the current American system of civilian aircraft call signs. Radio call signs used for communication in manned spaceflight is not formalized or regulated to the same degree as for aircraft; the three nations curren
Local marketing agreement
In North American broadcasting, a local marketing agreement is a contract in which one company agrees to operate a radio or television station owned by another party. In essence, it is a sort of time-buy. Under Federal Communications Commission regulations, a local marketing agreement must give the company operating the station under the agreement control over the entire facilities of the station, including the finances and programming of the station, its original licensee still remains responsible for the station and its operations, such as compliance with relevant regulations regarding content. A "local marketing agreement" may refer to the sharing or contracting of only certain functions, in particular advertising sales; this may be referred to as a time brokerage agreement, local sales agreement, management services agreement, or most a joint sales agreement or shared services agreement. JSAs are counted toward ownership caps for radio stations. In Canada, local marketing agreements between domestic stations require the consent of the Canadian Radio-television and Telecommunications Commission, although Rogers Media has used a similar arrangement to control a U.
S.-based radio station in a border market. The increased use of sharing agreements by media companies to form consolidated, "virtual" duopolies became controversial between 2009 and 2014 arrangements where a company buys a television station's facilities and assets, but sells the license to an affiliated third-party "shell" corporation, who enters into agreements with the owner of the facilities to operate the station on their behalf. Activists have argued that broadcasters were using these agreements as a loophole for the FCC's ownership regulations, that they reduce the number of local media outlets in a market through the aggregation or outright consolidation of news programming, allow station owners to have increased leverage in the negotiation of retransmission consent with local subscription television providers. Station owners have contended that these sharing agreements allow streamlined, cost-effective operations that may be beneficial to the continued operation of lower-rated and/or financially weaker stations in smaller markets.
In 2014 under chairman Tom Wheeler, the FCC began to increase its scrutiny regarding the use of such agreements—particularly joint sales—to evade its policies. On March 31, 2014, the commission voted to make joint sales agreements count as ownership if the senior partner sells 15% or more of advertising time for its partner, to ban coordinated retransmission consent negotiations between two of the top four stations in a market. Wheeler indicated that he planned to address local marketing and shared services agreements in the future; the change in stance prompted changes to then-proposed acquisitions by Gray Television and Sinclair Broadcast Group, rather than use sharing agreements to control them, moved their existing programming and network affiliations to digital subchannels of existing company-owned stations in the market, or a low-power station, relinquished control over the original stations by selling their licenses to third-parties, such as minority-owned broadcasters Due to the FCC's limits on station ownership at the time, local marketing agreements in radio, in which a smaller station would sell its entire airtime to a third-party in time-buy, were widespread between the 1970s and early 1990s.
These alliances gave larger broadcasters a way to expand their reach, smaller broadcasters a means of obtaining a stable stream of revenue. In 1992, the FCC began allowing broadcasting companies to own multiple radio stations in a single market. Following these changes, local marketing agreements fell out of favor for radio, as it was now possible for broadcasters to buy another station outright rather than lease it – consequentially triggering a wave of mass consolidation in the radio industry. However, broadcasters still used local marketing agreements to help transition acquired stations to their new owners; the first local marketing agreement in North American television was formed in 1991, when the Sinclair Broadcast Group purchased Fox affiliate WPGH-TV in Pittsburgh, Pennsylvania. As Sinclair had owned independent station WPTT in that market, which would have violated FCC rules which at the time had prohibited television station duopolies, Sinclair decided to sell the lower-rated WPTT to the station's manager Eddie Edwards, but continued to operate the station through an LMA.
Sinclair's use of local marketing agreements would lead to legal issues in 1999, when Glencairn, Ltd. announced that it would acquire Fox affiliate KOKH-TV in Oklahoma City, Oklahoma from Sullivan Broadcasting. As the family of Sinclair Broadcast Group founder Julian Smith controlled 97% of Glencairn's stock assets and the company was to be paid with Sinclair stock in turn for the purchases, KOKH and Sinclair-owned WB affiliate KOCB would constitute a duo
1080i is an abbreviation referring to a combination of frame resolution and scan type, used in high-definition television and high-definition video. The number "1080" refers to the number of horizontal lines on the screen; the "i" is an abbreviation for "interlaced". A related display resolution is 1080p, which has 1080 lines of resolution; the term assumes a widescreen aspect ratio of 16:9, so the 1080 lines of vertical resolution implies 1920 columns of horizontal resolution, or 1920 pixels × 1080 lines. A 1920 pixels × 1080 lines screen has a total of 2.1 megapixels and a temporal resolution of 50 or 60 interlaced fields per second. This format is used in the SMPTE 292M standard; the choice of 1080 lines originates with Charles Poynton, who in the early 1990s pushed for "square pixels" to be used in HD video formats. Within the designation "1080i", the i stands for interlaced scan. A frame of 1080i video consists of two sequential fields of 540 vertical pixels; the first field consists of all odd-numbered TV lines and the second all numbered lines.
The horizontal lines of pixels in each field are captured and displayed with a one-line vertical gap between them, so the lines of the next field can be interlaced between them, resulting in 1080 total lines. 1080i differs from 1080p, where the p stands for progressive scan, where all lines in a frame are captured at the same time. In native or pure 1080i, the two fields of a frame correspond to different instants, so motion portrayal is good; this is true for interlaced video in general and can be observed in still images taken of fast motion scenes. However, when 1080p material is captured at 25 or 30 frames/second, it is converted to 1080i at 50 or 60 fields/second for processing or broadcasting. In this situation both fields in a frame do correspond to the same instant; the field-to-instant relation is somewhat more complex for the case of 1080p at 24 frames/second converted to 1080i at 60 fields/second. The field rate of 1080i is 60 Hz for countries that use or used System M as analog television system with 60 fields/sec, or 50 Hz for regions that use or used 625-lines television system with 50 fields/sec.
Both field rates can be carried by major digital television broadcast formats such as ATSC, DVB, ISDB-T International. The frame rate can be implied by the context, while the field rate is specified after the letter i, such as "1080i60". In this case 1080i60 refers to 60 fields per second; the European Broadcasting Union prefers to use the resolution and frame rate separated by a slash, as in 1080i/30 and 1080i/25 480i/30 and 576i/25. Resolutions of 1080i60 or 1080i50 refers to 1080i/30 or 1080i/25 in EBU notation. 1080i is directly compatible with some CRT HDTVs on which it can be displayed natively in interlaced form, but for display on progressive-scan—e.g. Most new LCD and plasma TVs, it must be deinterlaced. Depending on the television's video processing capabilities, the resulting video quality may vary, but may not suffer. For example, film material at 25fps may be deinterlaced from 1080i50 to restore a full 1080p resolution at the original frame rate without any loss. Preferably video material with 50 or 60 motion phases/second is to be converted to 50p or 60p before display.
Worldwide, most HD channels on satellite and cable broadcast in 1080i. In the United States, 1080i is the preferred format for most broadcasters, with Inc.. Viacom, AT&T, Comcast owned networks broadcasting in the format. Only Fox-owned television networks and Disney-owned television networks, along with MLB Network and a few other cable networks use 720p as the preferred format for their networks. Many ABC affiliates owned by Hearst Television and former Belo Corporation stations owned by TEGNA, along with some individual affiliates of those three networks, air their signals in 1080i and upscale network programming for master control and transmission purposes, as most syndicated programming and advertising is produced and distributed in 1080i, removing a downscaling step to 720p; this allows local newscasts on these ABC affiliates to be produced in the higher resolution to match the picture quality of their 1080i competitors. Some cameras and broadcast systems that use 1080 vertical lines per frame do not use the full 1920 pixels of a nominal 1080i picture for image capture and encoding.
Common subsampling ratios include 3/4 and 1/2. Where used, the lower horizontal resolution is scaled to capture and/or display a full-sized picture. Using half horizontal resolution and only one field of each frame results in the format known as qHD, which has fram