Luma (video)
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Luma (video)
In video, luma represents the brightness in an image (the "black-and-white" or achromatic portion of the image). Luma is typically paired with chrominance. Luma represents the grey, achromatic image, while the chroma components represent the color information. Converting R′G′B′ sources (such as the output of a three-CCD camera) into luma and chroma allows for chroma subsampling: because human vision has finer spatial sensitivity to luminance ("black and white") differences than chromatic differences, video systems can store and transmit chromatic information at lower resolution, optimizing perceived detail at a particular bandwidth. Luma versus relative luminance Luma is the weighted sum of gamma-compressed R′G′B′ components of a color video—the ''prime symbols'' ′ denote Gamma correction, gamma compression. The word was proposed to prevent confusion between luma as implemented in video engineering and relative luminance as used in color science (i.e. as define ...
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Video
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems which, in turn, were replaced by flat panel displays of several types. Video systems vary in display resolution, aspect ratio The aspect ratio of a geometry, geometric shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height, when the rectangl ..., refresh rate, color capabilities and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcast, magnetic tape, optical discs, computer files, and network streaming. History Analog video Video technology was first developed for mechanical television systems, which were quickly replace ...
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SMPTE
The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association A professional association (also called a professional body, professional organization, or professional society) usually seeks to advocacy, further a particular profession, the interests of individuals and organisations engaged in that professio ... of engineers, technologists, and executives working in the media and entertainment industry. As an internationally recognized standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary function is developing, coordinating, promulgating, revising, amending, reissuing, interpr ..., SMPTE has published more than 800 technical standard A technical standard is an established norm or requirement for a repeatable technical task which ...
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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 YCbCr, Y'CbCr scheme requires two-thirds the bandwidth of non-subsampled "4:4:4" RGB, R'G'B'. This reduction results in almost no visual difference as perceived by the viewer. How subsampling works At normal viewing dis ...
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SMPTE Color Bars
SMPTE color bars are a television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Transmission (telecommunications), television transmission. Television ... test pattern used where the NTSC video standard is utilized, including countries in North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car .... The Society of Motion Picture and Television Engineers (SMPTE) refers to the pattern as Engineering Guideline (EG) 1-1990. Its components are a known 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 In signal processing, a signal is ...
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Multiple Sub-Nyquist Sampling Encoding
MUSE (Multiple sub-Nyquist Sampling Encoding), commercially known as Hi-Vision (a contraction of HIgh-definition teleVISION) was a Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...ese analog HDTV system, with design efforts going back to 1979. It used dot-interlacing and digital video compression to deliver 1125 line, 60 field-per-second (1125i60) signals to the home. The system was standardized as ITU-R recommendation BO.786 and specified by SMPTE 260M, using a colorimetry matrix specified by SMPTE 240M. As with other analog systems, not all lines carry visible information. On MUSE there are 1035 active interlaced lines, therefore this system is sometimes also mentioned as ''1035i''. It employed 2-dimensional filtering, dot-interlacing, motion-vector compensation a ...
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High-definition Television
High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the generation following standard-definition television (SDTV), often abbreviated to HDTV or HD-TV. It is the current de facto standard video format used in most broadcasts: terrestrial broadcast television, cable television Cable television is a system of delivering television broadcast programming, programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This ..., satellite television and Blu-ray Discs. Formats HDTV may be transmitted in various formats: * 720p (1280 horizontal pixels × 720 lines): 921,600 pixels * 1080i (1920×1080) interlaced scan: 1,036,800 pixels (~1.04 MP). * 1080p (1920×1080) progressive scan: 2,0 ...
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ITU-R
The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communications. Its role is to manage the international radio-frequency spectrum and satellite orbit resources and to develop standards for radiocommunication systems with the objective of ensuring the effective use of the spectrum. ITU is required, according to its constitution, to allocate spectrum and register frequency allocation, orbital positions and other parameters of satellites, “in order to avoid harmful interference between radio stations of different countries”. The international spectrum management system is therefore based on regulatory procedures for frequency coordination, notification and registration. ITU-R has a permanent secretariat, the Radiocommunication Bureau, based at the ITU HQ in Geneva, Switzerland. The electeDirector of the Bureauis Mr. Mario Maniewicz; he was first elected by t ...
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CCIR 601
ITU-R The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communications. Its role is to manage the international radio-frequency sp ... Recommendation BT.601, more commonly known by the abbreviations Rec. 601 or BT.601 (or its former name CCIR 601) is a standard originally issued in 1982 by the CCIR (an organization, which has since been renamed as the International Telecommunication Union Radiocommunication sector) for encoding interlaced analog video Video is an electronic medium for the recording, copying Copying is the duplication of information Information is an Abstraction, abstract concept that refers to that which has the power to Communication, inform. At the most fundam ... signals in digital video Digital video is an electronic representation of moving visual images (video) in the form of encoded digital data. This ...
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NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplementary references cited in the Reports, and the Petition for adoption of transmission standards for color television before the Federal Communications Commission, n.p., 1953], 17 v. illus., diagrs., tables. 28 cm. LC Control No.:5402138Library of Congress Online Catalog/ref> in 1941. In 1961, it was assigned the designation CCIR System M, System M. In 1953, a second NTSC standard was adopted, which allowed for color television broadcast compatible with the existing stock of black-and-white receivers. It is one of three major color formats for analog television, the others being PAL and SECAM. NTSC color is usually associated with the System M. The only other Broadcast television systems, broadcast television system to use NTSC color was the NT ...
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International Commission On Illumination
The International Commission on Illumination (usually abbreviated CIE for its French name, Commission internationale de l'éclairage) is the international authority on light, illumination, colour, and colour spaces. It was established in 1913 as a successor to the Commission Internationale de Photométrie, which was founded in 1900, and is today based in Vienna, Austria. Organization The CIE has six active divisions, each of which establishes technical committees to carry out its program: * Division 1: Vision and Colour * Division 2: Physical Measurement of Light and Radiation * Division 3: Interior Environment and Lighting Design * Division 4: Transportation and Exterior Applications * Division 6: Photobiology and Photochemistry * Division 8: Image Technology Two divisions are no longer active: * Division 5: Exterior Lighting and Other Applications * Division 7: General Aspects of Lighting The President of the CIE from 2019 is Dr Peter Blattner from Switzerland. CIE pu ...
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Chrominance
Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying Luma (video), luma signal (or Y' for short). Chrominance is usually represented as two color-difference components: U = B-Y, B′ − Y′ (blue − luma) and V = R-Y, R′ − Y′ (red − luma). Each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard. In composite video signals, the U and V signals modulate a color subcarrier signal, and the result is referred to as the chrominance signal; the Phase (waves), phase and amplitude of this modulated chrominance signal correspond approximately to the hue and Saturation (color theory), saturation of the color. In digital-video and still-image color spaces such as Y′CbCr, the luma and chrominance components are digit ...
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Relative Luminance
Relative luminance Y follows the Luminance, photometric definition of luminance L including spectral weighting for human vision, but while luminance L is a measure of light in units such as cd/m^2, Relative luminance Y values are normalized as 0.0 to 1.0 (or 1 to 100), with 1.0 (or 100) being a theoretical perfect reflector of 100% White point, reference white. Like the photometric definition, it is related to the luminous flux density in a particular direction, which is radiant flux density weighted by the luminous efficiency function (''λ'') of the CIE Standard Observer. The use of relative values is useful in color or appearance models that describe perception relative to the eye's adaptation state and a reference white. For example, in prepress for print media, the absolute luminance of light reflecting off the print depends on the specific illumination, but a color appearance model using relative luminance can predict the appearance by referencing the given light source. ...
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