|
Test Tone
A test card, also known as a test pattern or start-up/closedown test, is a television test signal, typically broadcast at times when the transmitter is active but no program is being broadcast (often at sign-on and sign-off). Used since the earliest TV broadcasts, test cards were originally physical cards at which a television camera was pointed, allowing for simple adjustments of picture quality. Such cards are still often used for calibration, alignment, and matching of cameras and camcorders. From the 1950s, test card images were built into monoscope tubes which freed up the use of TV cameras which would otherwise have to be rotated to continuously broadcast physical test cards during downtime hours. Electronically generated test patterns, used for calibrating or troubleshooting the downstream signal path, were introduced in the late-1960s, and became commonly used from the 1970s and 80s. These are generated by test signal generators, which do not depend on the correct confi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMPTE Color Bars
SMPTE color bars are a television test pattern used where the NTSC, NTSC video standard is utilized, including countries in North America. The Society of Motion Picture and Television Engineers (SMPTE) refers to the pattern as Engineering Guideline (EG) 1-1990. Its components are a known standardization, standard, and created by test pattern generators. Comparing it as received to the known standard gives video engineers an indication of how an NTSC video signal has been altered by recording or transmission and what adjustments must be made to bring it back to specification. It is also used for setting a television monitor or receiver to reproduce NTSC chrominance and Luminance (video), luminance information correctly. A precursor to the SMPTE test pattern was conceived by Norbert D. Larky (1927–2018) and David D. Holmes (1926–2006) of RCA Laboratories and first published in RCA Licensee Bulletin LB-819 on February 7, 1951. U.S. patent 2,742,525 Color Test Pattern Generator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jazz
Jazz is a music genre that originated in the African-American communities of New Orleans, Louisiana, in the late 19th and early 20th centuries. Its roots are in blues, ragtime, European harmony, African rhythmic rituals, spirituals, hymns, marches, vaudeville song, and dance music. Since the 1920s Jazz Age, it has been recognized as a major form of musical expression in traditional and popular music. Jazz is characterized by swing and blue notes, complex chords, call and response vocals, polyrhythms and improvisation. As jazz spread around the world, it drew on national, regional, and local musical cultures, which gave rise to different styles. New Orleans jazz began in the early 1910s, combining earlier brass band marches, French quadrilles, biguine, ragtime and blues with collective polyphonic improvisation. However, jazz did not begin as a single musical tradition in New Orleans or elsewhere. In the 1930s, arranged dance-oriented swing big bands, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enfield, London
Enfield is a large town in north London, England, north of Charing Cross. It had a population of 333,587 in 2021. It includes the areas of Botany Bay, London, Botany Bay, Brimsdown, Bulls Cross, Bullsmoor, Bush Hill Park, Clay Hill, London, Clay Hill, Crews Hill, Enfield Highway, Enfield Lock, Enfield Town, Enfield Wash, Forty Hill, Freezywater, Gordon Hill, London, Gordon Hill, Grange Park, Enfield, Grange Park, Hadley Wood, Ponders End, and World's End, Enfield, World's End. South of the Hertfordshire border and M25 motorway, it borders Waltham Cross to the north, Winchmore Hill and Edmonton, London, Edmonton to the south, Chingford and Waltham Abbey, across the River Lea, to the east and north-east, with Cockfosters, Monken Hadley and Oakwood, London, Oakwood to the west. Historically an Civil parish#Ancient parishes, ancient parish in the Edmonton Hundred of Middlesex, it was granted Urban district (Great Britain and Ireland), urban district status in 1894 and municipal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Independent Television Authority
The Independent Television Authority (ITA) was an agency created by the Television Act 1954 ( 2 & 3 Eliz. 2. c. 55) to supervise the creation of " Independent Television" (ITV), the first commercial television network in the United Kingdom. The ITA existed from 1954 until 1972. It was responsible for determining the location, constructing, building, and operating the transmission stations used by the ITV network, as well as determining the franchise areas and awarding the franchises for each regional commercial broadcaster. The authority began its operations on 4 August 1954, a mere four days after the Television Act 1954 received royal assent, under the chairmanship of Sir Kenneth Clark. The authority's first director general, Sir Robert Fraser was appointed by Clark a month later on 14 September. The physics of VHF broadcasting meant that a comparatively small number of transmitters could cover the majority of the population of Britain, if not the bulk of the area of the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ITV (TV Network)
ITV, legally known as Channel 3, is a British free-to-air public service broadcasting in the United Kingdom, public broadcast television network. It is branded as ITV1 in most of the UK except for central and northern Scotland, where it is branded as STV (TV channel), STV. It was launched in 1955 as Independent Television to provide competition to BBC Television (established in 1936). ITV is the oldest commercial network in the UK. Since the passing of the Broadcasting Act 1990, it has been Legal name, legally known as Channel 3 to distinguish it from the other analogue channels at the time: BBC1, BBC2 and Channel 4. ITV was, for decades, a network of separate companies that provided regional television services and also shared programmes among themselves to be shown on the entire network. Each franchise was originally owned by a different company. After several mergers, the fifteen regional franchises are now held by two companies: ITV plc, which runs ITV1, the ITV1 cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Service Contour
In US broadcasting, service contour (or protected contour) refers to the area in which the Federal Communications Commission (FCC) predicts coverage. The FCC calculates FM and TV contours based on effective radiated power (ERP) in a given direction, the radial height above average terrain (HAAT) in a given direction, the FCC's propagation curv and the station's List of broadcast station classes, class. AM contours are based on the standard ground wave field strength pattern, the frequency, and the ground conductivity Ground conductivity refers to the electrical conductivity of the subsurface of the earth. In the International System of Units (SI) it is measured in millisiemens per meter (mS/m). Radio propagation Ground conductivity is an extremely important ... in the area. While the FCC makes FM and TV service contour data readily available, the AM, while unavailable as a separate data file, can be obtained through aAM Queryin the resulting 'maps' section of each recor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colorburst
Colorburst is an analog and composite video signal generated by a video-signal generator used to keep the chrominance subcarrier synchronized in a color television signal. By synchronizing an oscillator with the colorburst at the back porch (beginning) of each scan line, a television receiver is able to restore the suppressed carrier of the chrominance (color) signals, and in turn decode the color information. The most common use of colorburst is to genlock equipment together as a common reference with a vision mixer in a television studio using a multi-camera setup. Explanation In NTSC, its frequency is exactly 315/88 = 3.579 MHz with a phase of 180°. PAL uses a frequency of exactly 4.43361875 MHz, with its phase alternating between 135° and 225° from line to line. Since the colorburst signal has a known amplitude, it is sometimes used as a reference level when compensating for amplitude variations in the overall signal. SECAM is unique in not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IRE (unit)
The IRE unit is used in the measurement of composite video signals. Its name is derived from the initials of the Institute of Radio Engineers. A value of 100 IRE is defined to be +714 mV in an analog NTSC video signal. A value of 0 IRE corresponds to the voltage value of 0 mV, the signal value during the blanking period. The sync pulse is normally 40 IRE below this 0 IRE value, so the total range covered from peak to trough of an all white signal would be 140 IRE. Video signals use the "IRE" unit instead of DC voltages to describe levels and amplitudes. Based on a standard 1 Vpp NTSC composite-video signal that swings from -286 mV (sync tip) to +714 mV (peak video), a 140 IRE peak-to-peak convention is established. Thus, one NTSC IRE unit is 7.143 mV ( V or mV), where -40 IRE is equivalent to -285.7 mV, and +100 IRE is equivalent to +714.3 mV. 0 IRE is equivalent to 0 V. The black level is equivalent to 53.57 mV (7.5 IRE). The PAL video signal is slightly different in that it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Video Projector
A video projector is an image projector that receives a video signal and projects the corresponding image onto a projection screen using a lens system. Video projectors use a very bright ultra-high-performance lamp (a special mercury arc lamp), Xenon arc lamp, metal halide lamp, LED or solid state blue, RB, RGB or fiber-optic lasers to provide the illumination required to project the image. Most modern projectors can correct any curves, blurriness and other inconsistencies through manual settings. Video projectors are used for many applications such as conference room presentations, classroom training, home cinema, movie theaters, and concerts, having mostly replaced overhead, slide and conventional film projectors. In schools and other educational settings, they are sometimes connected to an interactive whiteboard. In the late 20th century, they became commonplace in home cinema. Although large LCD television screens became quite popular, video projectors are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LED Display
A LED display is a flat panel display that uses an array of light-emitting diodes (LEDs) as pixels for a video display. Their brightness allows them to be used outdoors where they are visible in the sun for store signs and billboards. In recent years, they have also become commonly used in destination signs on public transport vehicles, as well as variable-message signs on highways. LED displays are capable of providing general illumination in addition to visual display, as when used for stage lighting or other decorative (as opposed to informational) purposes. LED displays can offer higher contrast ratios than a projector and are thus an alternative to traditional projection screens, and they can be used for large, uninterrupted (without a visible grid arising from the bezels of individual displays) video walls. microLED displays are LED displays with smaller LEDs, which poses significant development challenges. Their use in cinemas to replace projectors and projecti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Format Description
In television technology, Active Format Description (AFD) is a standard set of codes that can be sent in the MPEG video stream or in the baseband Serial digital interface, SDI video signal that carries information about their aspect ratio and other active picture characteristics. It has been used by television broadcasters to enable both 4:3 and 16:9 television sets to optimally present pictures transmitted in either format. It has also been used by broadcasters to dynamically control how down-conversion equipment formats widescreen 16:9 pictures for 4:3 displays. Standard AFD codes provide information to video devices about where in the coded picture the active video is and also the "Shoot and protect, protected area" which is the area that needs to be shown. Outside the protected area, edges at the sides or the top can be removed without the viewer missing anything significant. Video decoders and display devices can then use this information, together with knowledge of the displ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chroma Subsampling
Chroma subsampling is the practice of encoding images by implementing less resolution for Chrominance, chroma information than for luma (video), luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance. It is used in many video and still image encoding schemesboth analog and digitalincluding in JPEG encoding. Rationale Digital signals are often compressed to reduce file size and save transmission time. Since the human visual system is much more sensitive to variations in brightness than color, a video system can be optimized by devoting more bandwidth to the luma (video), luma component (usually denoted Y'), than to the color difference components Cb and Cr. In compressed images, for example, the 4:2:2 Y'CbCr scheme requires two-thirds the bandwidth of non-subsampled "4:4:4" R'G'B'. This reduction results in almost no visual difference as perceived by the viewer. How subsampling works The Visual perception, human vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
