1.
Chrominance
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Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal. Chrominance is usually represented as two color-difference components, U = B′ − Y′ and V = R′ − Y′, each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard. In digital-video and still-image color spaces such as Y′CbCr, the luma, separating RGB color signals into luma and chrominance allows the bandwidth of each to be determined separately. Typically, the bandwidth is reduced in analog composite video by reducing the bandwidth of a modulated color subcarrier. The idea of transmitting a color signal with distinct luma and chrominance components originated with Georges Valensi. Previous schemes for color television systems, which were incompatible with existing monochrome receivers, in analog television, chrominance is encoded into a video signal using a subcarrier frequency. Depending on the standard, the chrominance subcarrier may be either quadrature-amplitude-modulated or frequency-modulated. In the PAL system, the subcarrier is 4.43 MHz above the video carrier. The NTSC and PAL standards are the most commonly used, although there are other standards that employ different subcarrier frequencies. For example, PAL-M uses a 3.58 MHz subcarrier, the presence of chrominance in a video signal is indicated by a color burst signal transmitted on the back porch, just after horizontal synchronization and before each line of video starts. If the color burst signal were visible on a television screen, in NTSC and PAL, hue is represented by a phase shift of the chrominance signal relative to the color burst, while saturation is determined by the amplitude of the subcarrier. In SECAM and signals are transmitted alternately and phase does not matter, chrominance is represented by the U-V color plane in PAL and SECAM video signals, and by the I-Q color plane in NTSC. Digital video and digital photography systems sometimes use a luma/chroma decomposition for improved compression. On decompression, the Y′CbCr space is rotated back to RGB
2.
Information
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In other words, it is the answer to a question of some kind. It is thus related to data and knowledge, as data represents values attributed to parameters, as it regards data, the informations existence is not necessarily coupled to an observer, while in the case of knowledge, the information requires a cognitive observer. At its most fundamental, information is any propagation of cause, Information can be encoded into various forms for transmission and interpretation. It can also be encrypted for safe storage and communication, the uncertainty of an event is measured by its probability of occurrence and is inversely proportional to that. The more uncertain an event, the information is required to resolve uncertainty of that event. The bit is a unit of information, but other units such as the nat may be used. Example, information in one fair coin flip, log2 =1 bit, the concept that information is the message has different meanings in different contexts. The English word was derived from the Latin stem of the nominative. Inform itself comes from the Latin verb informare, which means to give form, eidos can also be associated with thought, proposition, or even concept. The ancient Greek word for information is πληροφορία, which transliterates from πλήρης fully and it literally means fully bears or conveys fully. In modern Greek language the word Πληροφορία is still in use and has the same meaning as the word information in English. In addition to its meaning, the word Πληροφορία as a symbol has deep roots in Aristotles semiotic triangle. In this regard it can be interpreted to communicate information to the one decoding that specific type of sign, from the stance of information theory, information is taken as an ordered sequence of symbols from an alphabet, say an input alphabet χ, and an output alphabet ϒ. Information processing consists of a function that maps any input sequence from χ into an output sequence from ϒ. The mapping may be probabilistic or deterministic and it may have memory or be memoryless. Often information can be viewed as a type of input to an organism or system, inputs are of two kinds, some inputs are important to the function of the organism or system by themselves. In his book Sensory Ecology Dusenbery called these causal inputs, other inputs are important only because they are associated with causal inputs and can be used to predict the occurrence of a causal input at a later time. Some information is important because of association with information but eventually there must be a connection to a causal input
3.
JPEG
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JPEG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between size and image quality. JPEG typically achieves 10,1 compression with little loss in image quality. JPEG compression is used in a number of file formats. These format variations are not distinguished, and are simply called JPEG. The term JPEG is an initialism/acronym for the Joint Photographic Experts Group, the MIME media type for JPEG is image/jpeg, except in older Internet Explorer versions, which provides a MIME type of image/pjpeg when uploading JPEG images. JPEG files usually have an extension of. jpg or. jpeg. JPEG/JFIF supports a maximum size of 65, 535×65,535 pixels. JPEG stands for Joint Photographic Experts Group, the name of the committee created the JPEG standard. The Joint stood for ISO TC97 WG8 and CCITT SGVIII, in 1987 ISO TC97 became ISO/IEC JTC1 and in 1992 CCITT became ITU-T. Currently on the JTC1 side JPEG is one of two sub-groups of ISO/IEC Joint Technical Committee 1, Subcommittee 29, Working Group 1 – titled as Coding of still pictures, on the ITU-T side ITU-T SG16 is the respective body. The original JPEG group was organized in 1986, issuing the first JPEG standard in 1992, which was approved in September 1992 as ITU-T Recommendation T.81 and in 1994 as ISO/IEC 10918-1. The JPEG standard specifies the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, the Exif and JFIF standards define the commonly used file formats for interchange of JPEG-compressed images. JPEG standards are formally named as Information technology – Digital compression, ISO/IEC10918 consists of the following parts, Ecma International TR/98 specifies the JPEG File Interchange Format, the first edition was published in June 2009. The JPEG compression algorithm is at its best on photographs and paintings of scenes with smooth variations of tone. For web usage, where the amount of used for an image is important. JPEG/Exif is also the most common format saved by digital cameras, on the other hand, JPEG may not be as well suited for line drawings and other textual or iconic graphics, where the sharp contrasts between adjacent pixels can cause noticeable artifacts. Such images may be saved in a lossless graphics format such as TIFF, GIF, PNG
4.
YCbCr
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YCbCr, Y′CbCr, or Y Pb/Cb Pr/Cr, also written as YCBCR or Y′CBCR, is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the component and CB and CR are the blue-difference and red-difference chroma components. Y′ is distinguished from Y, which is luminance, meaning that light intensity is nonlinearly encoded based on gamma corrected RGB primaries, Y′CbCr color spaces are defined by a mathematical coordinate transformation from an associated RGB color space. If the underlying RGB color space is absolute, the Y′CbCr color space is a color space as well, conversely, if the RGB space is ill-defined. By doing this, subsequent image/video processing, transmission and storage can do operations, one practical example would be decreasing the bandwidth or resolution allocated to color compared to black and white, since humans are more sensitive to the black-and-white information. YCbCr is sometimes abbreviated to YCC, Y′CbCr is often called YPbPr when used for analog component video, although the term Y′CbCr is commonly used for both systems, with or without the prime. Here, the prime ′ symbols mean gamma correction is being used, thus R′, G′ and B′ nominally range from 0 to 1, with 0 representing the minimum intensity and 1 the maximum. The resulting luma value will then have a range from 0 to 1. The reverse conversion process can be derived by inverting the above equations. When representing the signals in digital form, the results are scaled and rounded, for example, the scaling and offset applied to the Y′ component per specification results in the value of 16 for black and the value of 235 for white when using an 8-bit representation. The standard has 8-bit digitized versions of CB and CR scaled to a different range of 16 to 240 and this head-room and toe-room can also be used for extension of the nominal color gamut, as specified by xvYCC. The value 235 accommodates a maximum black-to-white overshoot of 255 -235 =20, or 20 / =9. 1%, the toe-room is smaller, allowing only 16 /219 =7. 3% overshoot, which is less than the theoretical maximum overshoot of 8. 9%. This causes some difficulty in determining how to interpret and display some YCbCr signals. These out-of-range YCbCr values are used by xvYCC to encode colors outside the BT.709 gamut and this allows for the value 256 in the denominator, which can be calculated by a single bitshift. A different form of Y′CbCr is specified in the ITU-R BT.709 standard, the newer form is also used in some computer-display oriented applications. In this case, the values of Kb and Kr differ, but the formulas for using them are the same. The definitions of the R, G, and B signals also differ between BT.709 and BT.601, and differ within BT.601 depending on the type of TV system in use, and differ further in other specifications. So proper conversion of Y′CbCr from one form to the other is not just a matter of inverting one matrix, the ITU-R BT.2020 standard defines both gamma corrected Y′CbCr and a linear-encoded version of YCbCr called YcCbcCrc
5.
RGB color model
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The RGB color model is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three primary colors, red, green and blue. Before the electronic age, the RGB color model already had a theory behind it. Thus an RGB value does not define the same color across devices without some kind of color management, typical RGB input devices are color TV and video cameras, image scanners, video games, and digital cameras. Typical RGB output devices are TV sets of technologies, computer and mobile phone displays, video projectors, multicolor LED displays. Color printers, on the hand are not RGB devices. This article discusses concepts common to all the different color spaces that use the RGB color model, to form a color with RGB, three light beams must be superimposed. Each of the three beams is called a component of color, and each of them can have an arbitrary intensity, from fully off to fully on. The RGB color model is additive in the sense that the three beams are added together, and their light spectra add, wavelength for wavelength. This is essentially opposite to the color model that applies to paints, inks, dyes. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, a secondary color is formed by the sum of two primary colors of equal intensity, cyan is green+blue, magenta is red+blue, and yellow is red+green. The RGB color model itself does not define what is meant by red, green and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green and blue primaries are defined, the normal three kinds of light-sensitive photoreceptor cells in the human eye respond most to yellow, green, and violet light. As an example, suppose that light in the range of wavelengths enters the eye. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more, the difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously. The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, to reproduce the color photograph, three matching projections over a screen in a dark room were necessary
6.
Visual system
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The visual system is the part of the central nervous system which gives organisms the ability to process visual detail, as well as enabling the formation of several non-image photo response functions. It detects and interprets information from visible light to build a representation of the surrounding environment, the psychological process of visual information is known as visual perception, a lack of which is called blindness. Non-image forming visual functions, independent of perception, include the pupillary light reflex. This article mostly describes the system of mammals, humans in particular. Together the cornea and lens refract light into a small image, the retina transcribes this image into electrical pulses using rods and cones. The optic nerve then carries these pulses through the optic canal, upon reaching the optic chiasm the nerve fibers decussate. The fibers then branch and terminate in three places, most end in the lateral geniculate nucleus. Before the LGN forwards the pulses to V1 of the visual cortex it gauges the range of objects, the LGN also sends some fibers to V2 and V3. V1 performs edge-detection to understand spatial organization, V2 both forwards pulses to V1 and receives them. Pulvinar is responsible for saccade and visual attention, V2 serves much the same function as V1, however, it also handles illusory contours, determining depth by comparing left and right pulses, and foreground distinguishment. V3 helps process ‘global motion’ of objects, V3 connects to V1, V2, and the inferior temporal cortex. V4 recognizes simple shapes, gets input from V1, V2, V3, LGN, v5’s outputs include V4 and its surrounding area, and eye-movement motor cortices. V5’s functionality is similar to that of the other V’s, however, V6 works in conjunction with V5 on motion analysis. V5 analyzes self-motion, whereas V6 analyzes motion of objects relative to the background, v6’s primary input is V1, with V5 additions. V6 houses the topographical map for vision, V6 outputs to the region directly around it. V6A has direct connections to arm-moving cortices, including the premotor cortex, the inferior temporal gyrus recognizes complex shapes, objects, and faces or, in conjunction with the hippocampus, creates new memories. The pretectal area is seven unique nuclei, anterior, posterior and medial pretectal nuclei inhibit pain, aid in REM, and aid the accommodation reflex, respectively. The Edinger-Westphal nucleus moderates pupil dilation and aids in convergence of the eyes, nuclei of the optic tract are involved in smooth pursuit eye movement and the accommodation reflex, as well as REM
7.
Bandwidth (signal processing)
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Bandwidth is the difference between the upper and lower frequencies in a continuous set of frequencies. It is typically measured in hertz, and may refer to passband bandwidth, sometimes to baseband bandwidth. Passband bandwidth is the difference between the upper and lower frequencies of, for example, a band-pass filter, a communication channel. In the case of a filter or baseband signal, the bandwidth is equal to its upper cutoff frequency. A key characteristic of bandwidth is that any band of a given width can carry the amount of information. For example, a 3 kHz band can carry a telephone conversation whether that band is at baseband or modulated to some higher frequency, Bandwidth is a key concept in many telecommunications applications. In radio communications, for example, bandwidth is the range occupied by a modulated carrier signal. An FM radio receivers tuner spans a range of frequencies. A government agency may apportion the regionally available bandwidth to broadcast license holders so that their signals do not mutually interfere, each transmitter owns a slice of bandwidth. For different applications there are different precise definitions, which are different for signals than for systems. One definition of bandwidth, for a system, could be the range of frequencies over which the system produces a level of performance. A less strict and more practically useful definition will refer to the frequencies beyond which frequency response is small, small could mean less than 3 dB below the maximum value, or more rarely 10 dB below, or it could mean below a certain absolute value. As with any definition of the width of a function, many definitions are suitable for different purposes, in some contexts, the signal bandwidth in hertz refers to the frequency range in which the signals spectral density is nonzero or above a small threshold value. That definition is used in calculations of the lowest sampling rate that will satisfy the sampling theorem, the threshold value is often defined relative to the maximum value, and is most commonly the 3dB point, that is the point where the spectral density is half its maximum value. The word bandwidth applies to signals as described above, but it could apply to systems. To say that a system has a certain bandwidth means that the system can process signals of that bandwidth, or that the system reduces the bandwidth of a white noise input to that bandwidth. If the maximum gain is 0 dB, the 3 dB bandwidth is the range where the gain is more than −3 dB. This is also the range of frequencies where the gain is above 70. 7% of the maximum amplitude gain
8.
Sampling (signal processing)
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In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a wave to a sequence of samples. A sample is a value or set of values at a point in time and/or space, a sampler is a subsystem or operation that extracts samples from a continuous signal. A theoretical ideal sampler produces samples equivalent to the value of the continuous signal at the desired points. Sampling can be done for functions varying in space, time, or any other dimension, then the sampled function is given by the sequence, s, for integer values of n. The sampling frequency or sampling rate, fs, is the number of samples obtained in one second. Reconstructing a continuous function from samples is done by interpolation algorithms, the Whittaker–Shannon interpolation formula is mathematically equivalent to an ideal lowpass filter whose input is a sequence of Dirac delta functions that are modulated by the sample values. When the time interval between adjacent samples is a constant, the sequence of functions is called a Dirac comb. Mathematically, the modulated Dirac comb is equivalent to the product of the function with s. That purely mathematical abstraction is sometimes referred to as impulse sampling, most sampled signals are not simply stored and reconstructed. But the fidelity of a reconstruction is a customary measure of the effectiveness of sampling. That fidelity is reduced when s contains frequency components whose periodicity is smaller than 2 samples, the quantity ½ cycles/sample × fs samples/sec = fs/2 cycles/sec is known as the Nyquist frequency of the sampler. Therefore, s is usually the output of a lowpass filter, without an anti-aliasing filter, frequencies higher than the Nyquist frequency will influence the samples in a way that is misinterpreted by the interpolation process. In practice, the signal is sampled using an analog-to-digital converter. This results in deviations from the theoretically perfect reconstruction, collectively referred to as distortion, various types of distortion can occur, including, Aliasing. Some amount of aliasing is inevitable because only theoretical, infinitely long, Aliasing can be made arbitrarily small by using a sufficiently large order of the anti-aliasing filter. Aperture error results from the fact that the sample is obtained as a time average within a sampling region, in a capacitor-based sample and hold circuit, aperture error is introduced because the capacitor cannot instantly change voltage thus requiring the sample to have non-zero width. Jitter or deviation from the precise sample timing intervals, noise, including thermal sensor noise, analog circuit noise, etc
9.
Opponent process
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The color opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cones and rods in an antagonistic manner. The opponent color theory suggests that there are three opponent channels, red versus green, blue versus yellow, and black versus white, responses to one color of an opponent channel are antagonistic to those to the other color. That is, opposite opponent colors are never perceived together – there is no greenish red or yellowish blue, besides the cones, which detect light entering the eye, the biological basis of the opponent theory involves two other types of cells, bipolar cells, and ganglion cells. Information from the cones is passed to the cells in the retina. The information is passed to ganglion cells, of which there are two major classes, magnocellular, or large-cell layers, and parvocellular, or small-cell layers. The first subtype of cells are responsible for processing red–green differences, P cells also transmit information about intensity of light due to their receptive fields. Johann Wolfgang von Goethe first studied the effect of opposed colors in his Theory of Colours in 1810. Goethe arranged his color wheel symmetrically, for the diametrically opposed to each other in this diagram are those which reciprocally evoke each other in the eye. Thus, yellow purple, orange, blue, red, green. Ewald Hering proposed opponent color theory in 1892 and he thought that the colors red, yellow, green, and blue are special in that any other color can be described as a mix of them, and that they exist in opposite pairs. That is, either red or green is perceived and never greenish-red, although yellow is a mixture of red and green in the RGB color theory, in 1957, Leo Hurvich and Dorothea Jameson provided quantitative data for Herings color opponency theory. Their method was called hue cancellation, griggs expanded the concept to reflect a wide range of opponent processes for biological systems in this book Biological Relativity 1967. In 1970, Richard Solomon expanded Hurvichs general neurological opponent process model to explain emotion, drug addiction, the opponent color theory can be applied to computer vision and implemented as the Gaussian color model and the natural-vision-processing model. If someone stares at a red square for forty seconds, and then looks at a white sheet of paper. For ways of seeing combinations of opponent colors, see Claimed evidence for ability to see colors not in the color space. Impossible colors Lab color space Natural Color System Baccus SA,2007, timing and computation in inner retinal circuitry. The fundamental plan of the retina, sowden PT and Schyns PG,2006. Channel surfing in the visual brain, parallel processing in the mammalian retina
10.
Gamma correction
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Gamma correction, or often simply gamma, is the name of a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. In the common case of A =1, inputs and outputs are typically in the range 0–1, Gamma encoding of floating-point images is not required, because the floating-point format already provides a piecewise linear approximation of a logarithmic curve. Although gamma encoding was developed originally to compensate for the characteristic of cathode ray tube displays. In CRT displays, the intensity varies nonlinearly with the electron-gun voltage. Altering the input signal by gamma compression can cancel this nonlinearity, the similarity of CRT physics to the inverse of gamma encoding needed for video transmission was a combination of luck and engineering, which simplified the electronics in early television sets. The concept of gamma can be applied to any nonlinear relationship, for a power-law curve, this slope is constant, but the idea can be extended to any type of curve, in which case gamma is defined as the slope of the curve in any particular region. For a given film formulation and processing method, this curve is its characteristic or Hurter–Driffield curve, since both axes use logarithmic units, the slope of the linear section of the curve is called the gamma of the film. Negative film typically has a less than 1, positive film typically has a gamma greater than 1. Photographic film has a greater ability to record fine differences in shade than can be reproduced on photographic paper. Similarly, most video screens are not capable of displaying the range of brightnesses that can be captured by typical electronic cameras, for this reason, considerable artistic effort is invested in choosing the reduced form in which the original image should be presented. The gamma correction, or contrast selection, is part of the repertoire used to adjust the reproduced image. Analogously, digital cameras record light using electronic sensors that usually respond linearly, in the process of rendering linear raw data to conventional RGB data, color space transformations and rendering transformations will be performed. In most computer systems, images are encoded with a gamma of about 0.45. A notable exception, until the release of Mac OS X10.6 in September 2009, were Macintosh computers, in any case, binary data in still image files are explicitly encoded, as are motion picture files. The system can optionally further manage both cases, through management, if a better match to the output device gamma is required. Below a compressed value of 0.04045 or a linear intensity of 0.00313, the dashed black curve behind the red curve is a standard γ =2.2 power-law curve, for comparison. For television signals, the actual values are defined by the video standards. A gamma characteristic is a relationship that approximates the relationship between the encoded luma in a television system and the actual desired image luminance
11.
CIE 1931 color space
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The CIE1931 color spaces were the first defined quantitative links between physical pure colors in the electromagnetic visible spectrum, and physiological perceived colors in human color vision. The CIE1931 RGB color space and CIE1931 XYZ color space were created by the International Commission on Illumination in 1931 and they resulted from a series of experiments done in the late 1920s by William David Wright and John Guild. The experimental results were combined into the specification of the CIE RGB color space, the CIE1931 color spaces are still widely used, as is the 1976 CIELUV color space. The human eye with normal vision has three kinds of cells, which sense light, with spectral sensitivity peaks in short, middle. These cone cells underlie human color perception under medium- and high-brightness conditions, thus, three parameters, corresponding to levels of stimulus of the three types of cone cells, can in principle describe any color sensation. The tristimulus values associated with a space can be conceptualized as amounts of three primary colors in a tri-chromatic additive color model. In some color spaces, including LMS and XYZ spaces, the colors used are not real colors. The CIE XYZ color space encompasses all color sensations that a person can experience. That is why CIE XYZ is a device invariant color representation and it serves as a standard reference against which many other color spaces are defined. Consider two light sources made up of different mixtures of various wavelengths, such light sources may appear to be the same color, this effect is called metamerism. Such light sources have the apparent color to an observer when they produce the same tristimulus values. Most wavelengths stimulate two or all three types of cell, because the spectral sensitivity curves of the three types of cone cells overlap. Certain tristimulus values are thus physically impossible, to avoid these negative RGB values, and to have one component that describes the perceived brightness, imaginary primary colors and corresponding color-matching functions have been formulated. The resulting tristimulus values are defined by the CIE1931 color space, in which they are denoted X, Y, and Z. When judging the relative luminance of different colors in well-lit situations, humans tend to perceive light within the green parts of the spectrum as brighter than red or blue light of equal power. The luminosity function that describes the perceived brightnesses of different wavelengths is thus analogous to the spectral sensitivity of M cones. The CIE model capitalises on this fact by defining Y as luminance, Z is quasi-equal to blue stimulation, or the S cone response, and X is a mix of cone response curves chosen to be nonnegative. The XYZ tristimulus values are thus analogous to, but different from, defining Y as luminance has the useful result that for any given Y value, the XZ plane will contain all possible chromaticities at that luminance
12.
Alpha compositing
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In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency. It is often useful to render image elements in separate passes, for example, compositing is used extensively when combining computer-rendered image elements with live footage. In order to combine these image elements correctly, it is necessary to keep an associated matte for each element. To store matte information, the concept of a channel was introduced by Alvy Ray Smith in the late 1970s. In a 2D image element, which stores a color for each pixel, additional data is stored in the alpha channel with a value between 0 and 1. A value of 0 means that the pixel does not have any information and is transparent. A value of 1 means that the pixel is opaque because the geometry completely overlapped the pixel, if an alpha channel is used in an image, there are two common representations that are available, straight alpha, and premultiplied alpha. With straight alpha, the RGB components represent the color of the object or pixel, with premultiplied alpha, the RGB components represent the color of the object or pixel, adjusted for its opacity by multiplication. A more obvious advantage of this is that, in certain situations, however, the most significant advantages of using premultiplied alpha are for correctness and simplicity rather than performance, premultiplied alpha allows correct filtering and blending. In addition, premultiplied alpha allows regions of alpha blending. Assuming that the color is expressed using straight RGBA tuples. If the color were fully green, its RGBA would be, however, if this pixel uses premultiplied alpha, all of the RGB values are multiplied by 0.5 and then the alpha is appended to the end to yield. In this case, the 0.5 value for the G channel actually indicates 100% green intensity, for this reason, knowing whether a file uses straight or premultiplied alpha is essential to correctly process or composite it. Premultiplied alpha has some advantages over normal alpha blending because premultiplied alpha blending is associative. Moreover, premultiplied alpha has a representation for transparent pixels. Ordinary interpolation without premultiplied alpha leads to RGB information leaking out of fully transparent regions, when interpolating or filtering images with abrupt borders between transparent and opaque regions, this can result in borders of colors that were not visible in the original image. Errors also occur in areas of semitransparancy because the RGB components are not correctly weighted, with the existence of an alpha channel, it is possible to express compositing image operations using a compositing algebra. For example, given two image elements A and B, the most common compositing operation is to combine the images such that A appears in the foreground and this can be expressed as A over B
13.
Aliasing
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In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable when sampled. It also refers to the distortion or artifact that results when the signal reconstructed from samples is different from the continuous signal. Aliasing can occur in signals sampled in time, for digital audio. Aliasing can also occur in spatially sampled signals, for instance moiré patterns in digital images, aliasing in spatially sampled signals is called spatial aliasing. Aliasing is generally avoided by applying low pass filters- anti-aliasing filters to the signal before sampling. When a digital image is viewed, a reconstruction is performed by a display or printer device, and by the eyes and the brain. If the image data is processed in some ways during sampling or reconstruction, the image will differ from the original image. An example of aliasing is the moiré pattern observed in a poorly pixelized image of a brick wall. Spatial anti-aliasing techniques avoid such poor pixelizations, aliasing can be caused either by the sampling stage or the reconstruction stage, these may be distinguished by calling sampling aliasing prealiasing and reconstruction aliasing postaliasing. Temporal aliasing is a concern in the sampling of video. Music, for instance, may contain components that are inaudible to humans. If a piece of music is sampled at 32000 samples per second, to prevent this an anti-aliasing filter is used to remove components above the Nyquist frequency prior to sampling. In video or cinematography, temporal aliasing results from the frame rate. Aliasing has changed its apparent frequency of rotation, a reversal of direction can be described as a negative frequency. Like the video camera, most sampling schemes are periodic, that is, digital cameras provide a certain number of samples per degree or per radian, or samples per mm in the focal plane of the camera. Audio signals are sampled with a converter, which produces a constant number of samples per second. Some of the most dramatic and subtle examples of aliasing occur when the signal being sampled also has periodic content, actual signals have finite duration and their frequency content, as defined by the Fourier transform, has no upper bound. Some amount of aliasing always occurs when such functions are sampled, functions whose frequency content is bounded have infinite duration
14.
HDCAM
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The HDCAM codec uses rectangular pixels and as such the recorded 1440×1080 content is upsampled to 1920×1080 on playback. The recorded video bit rate is 144 Mbit/s, audio is also similar, with four channels of AES3 20-bit,48 kHz digital audio. Like Betacam, HDCAM tapes are produced in small and large cassette sizes, the main competitor to HDCAM is the DVCPRO HD format offered by Panasonic. It uses a compression scheme and bit rates ranging from 40 Mbit/s to 100 Mbit/s depending on frame rate. HDCAM is standardized as SMPTE 367M, also known as SMPTE D-11, SMPTE 367M, also known as SMPTE D-11, is the SMPTE standard for HDCAM. The standard specifies compression of digital video. Each D11 source frame is composed of a channel at 1920 x 1080 pixels. During compression, each frames luminance channel is subsampled at 1440 x 1080, HDCAM SR was introduced in 2003 and standardised in SMPTE 409M-2005. It uses a particle density tape and is capable of recording in 10 bits 4,2,2 or 4,4,4 RGB with a video bit rate of 440 Mbit/s. The increased bit rate allows HDCAM SR to capture more of the full bandwidth of the HDSDI signal. Some HDCAM SR VTRs can also use a 2× mode with a higher video bit rate of 880 Mbit/s. HDCAM SR uses MPEG-4 Part 2 Simple Studio Profile for compression, there are 12 channels of audio recorded uncompressed at 24 bit 48 kHz sampling. Each channel is capable of recording AES3 non-audio data, HDCAM SR is used commonly for HDTV television production. As of 2007, many network television shows use HDCAM SR as a master recording medium. Tape lengths are the same as for Digital Betacam, up to 40 minutes for S and 124 minutes for L tapes, in 24p mode the runtime increases to 50 and 155 minutes, respectively. HDCAM tapes are black with a lid, and HDCAM SR tapes black with a cyan lid. 440 Mbit/s mode is known as SQ, and 880 Mbit/s mode is known as HQ, in 2008 the SRW-5800 will give the HQ4,4,4 option. Sony has also announced a higher compression mode called SR Lite, as with the 440 and 880 mode, SR Lite utilizes the MPEG-4 Part 2 Simple Studio Profile but decreases the bit rate down to 220 Mbit/s for 60i and 183 Mbit/s for 50i
15.
Serial digital interface
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Serial digital interface is a family of digital video interfaces first standardized by SMPTE in 1989. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video, a related standard, known as high-definition serial digital interface, is standardized in SMPTE 292M, this provides a nominal data rate of 1.485 Gbit/s. Additional SDI standards have been introduced to support increasing video resolutions, frame rates, stereoscopic video, 3G-SDI consists of a single 2.970 Gbit/s serial link that allows replacing dual link HD-SDI. 6G-SDI and 12G-SDI standards were published on March 19,2015 and these standards are used for transmission of uncompressed, unencrypted digital video signals within television facilities, they can also be used for packetized data. Coaxial variants of the range in length but are typically less than 300 meters. Fiber optic variants of the such as 297M allow for long-distance transmission limited only by maximum fiber length or repeaters. Several professional video and HD-video capable DSLR cameras and all uncompressed video capable consumer cameras use the HDMI interface, there are various mod kits for existing DVD players and other devices, which allow a user to add a serial digital interface to these devices. The various serial digital interface standards all use coaxial cables with BNC connectors and this is the same type of cable used in analog video setups, which potentially makes for easier upgrades. The specified signal amplitude at the source is 800 mV peak-to-peak, using equalization at the receiver, it is possible to send 270 Mbit/s SDI over 300 meters without use of repeaters, but shorter lengths are preferred. The HD bitrates have a maximum run length, typically 100 meters. Uncompressed digital component signals are transmitted, data is encoded in NRZI format, and a linear feedback shift register is used to scramble the data to reduce the likelihood that long strings of zeroes or ones will be present on the interface. The interface is self-synchronizing and self-clocking, * Working group 32NF-70 is in the process of developing standard ST-2083 for 24Gbit/s SDI. 270 Mbit/s is by far the most commonly used, though the 360 Mbit/s interface is sometimes encountered, the 143 and 177 Mbit/s interfaces were intended for transmission of composite-encoded video digitally, and are now considered obsolete. For enhanced definition applications, there are several 540 Mbit/s interfaces defined, for HDTV applications, the serial digital interface is defined by SMPTE 292M. Two bit rates are defined,1.485 Gbit/s, and 1. 485/1.001 Gbit/s. The factor of 1/1.001 is provided to allow SMPTE 292M to support video formats with rates of 59.94 Hz,29.97 Hz. The 1.485 Gbit/s version of the standard supports other frame rates in widespread use, including 60 Hz,50 Hz,30 Hz,25 Hz and it is common to collectively refer to both standards as using a nominal bit rate of 1.5 Gbit/s. For very high-definition applications, requiring resolution, frame rate, or color fidelity than the HD-SDI interface can provide
16.
Betacam
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Betacam is a family of half-inch professional videocassette products developed by Sony in 1982. In colloquial use, Betacam singly is often used to refer to a Betacam camcorder, a Betacam tape, the cassettes are available in two sizes, S and L. The Betacam camcorder can only load S magnetic tapes, while television studio sized video tape recorders designed for video editing can play both S and L tapes, the cassette shell and case for each Betacam cassette is colored differently depending on the format, allowing for easy visual identification. There is also a key, that allows a video tape recorder to identify which format has been inserted. The smaller S cassettes use the form factor as Betamax. The format supplanted the three-quarter-inch U-Matic format, which Sony had introduced in 1971, in addition to improvements in video quality, the Betacam configuration of an integrated professional video camera/recorder led to its rapid adoption by electronic news gathering organizations. DigiBeta, the name for Digital Betacam, went on to become the single most successful professional broadcast digital recording video tape format in history. The original Betacam format was launched on August 7,1982, a blank Betamax-branded tape will work on a Betacam deck, and a Betacam-branded tape can be used to record in a Betamax deck. However, in later years Sony discouraged this practice, suggesting, in particular, the guide rollers tend to be noisy. Another common point between Betamax and Betacam is the placement of the linear audio tracks. Also, some Betacam and Betamax portables share the same batteries, Betacam was initially introduced as a camera line along with a video cassette player. The first cameras were the BVP-3, which utilized three saticon tubes, and the BVP1, which used a single tri-stripe Trinicon tube, both these cameras could be operated standalone, or with their docking companion VTR, the BVV-1, to form the BVW-1 integrated camcorder. The only transport controls on the deck were Eject and Rewind, the docked cameras VTR button started and paused the tape recorder. Later the Betacam SP docking decks had full transport controls but tapes could not be played back except in the viewfinder in black-and-white only. Sony then came out with the Play Adapter, a portable unit that connected via a multi-pin cable and had a composite video out jack for color playback. At first color playback required the studio source deck, the BVW-10 and it was primarily designed as a feeder deck for A/B roll edit systems, usually for editing to a one-inch Type C or three-quarter-inch U-matic cassette edit master tape. There was also the BVW-20 field playback deck, which was a unit with DC power and a handle. Unlike the BVW-10, it did not have a built in Time Base Corrector, or TBC, with the popular success of the Betacam system as a news acquisition format, the line was soon extended to include the BVW-15 studio player, and the BVW-40 Studio Edit Recorder
17.
DV
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DV is a format for storing digital video. It was launched in 1995 with joint efforts of leading producers of video camera recorders, the original DV specification, known as Blue Book, was standardized within the IEC61834 family of standards. These standards define common features such as physical videocassettes, recording modulation method, magnetization, part 2 describes the specifics of 525-60 and 625-50 systems. The IEC standards are available as publications sold by IEC and ANSI, in 2003, DV was joined by a successor format HDV, which used the same tape format with a different video codec. Some cameras at the time had the ability to switch between DV and HDV recording modes, DV uses lossy compression of video while audio is stored uncompressed. An intraframe video compression scheme is used to video on a frame-by-frame basis with the discrete cosine transform. Closely following ITU-R Rec.601 standard, DV video employs interlaced scanning with the sampling frequency of 13.5 MHz. This results in 480 scanlines per complete frame for the 60 Hz system, in both systems the active area contains 720 pixels per scanline, with 704 pixels used for content and 16 pixels on the sides left for digital blanking. The same frame size is used for 4,3 and 16,9 frame aspect ratios, prior to the DCT compression stage, chroma subsampling is applied to the source video in order to reduce the amount of data to be compressed. Baseline DV uses 4,1,1 subsampling in its 60 Hz variant and 4,2,0 subsampling in the 50 Hz variant. Audio can be stored in either of two forms, 16-bit Linear PCM stereo at 48 kHz sampling rate, or four nonlinear 12-bit PCM channels at 32 kHz sampling rate. In addition, the DV specification also supports 16-bit audio at 44.1 kHz, in practice, the 48 kHz stereo mode is used almost exclusively. The audio, video, and metadata are packaged into 80-byte Digital Interface Format blocks which are multiplexed into a 150-block sequence. DIF blocks are the units of DV streams and can be stored as computer files in raw form or wrapped in such file formats as Audio Video Interleave, QuickTime. One video frame is formed from either 10 or 12 such sequences, depending on scanning rate, which results in a rate of about 25 Mbit/s for video. When written to tape, each corresponds to one complete track. This means that the sound may be +/- ⅓ frame out of sync with the video, however, this is the maximum drift of the audio/video synchronization, it is not compounded throughout the recording. Sony and Panasonic created their versions of DV, which use the same compression scheme
18.
Digital-S
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D-9 or Digital-S as it was originally known, is a professional digital video videocassette format created by JVC in 1995. It is a competitor to Sonys Digital Betacam. Its name was changed to D-9 in 1999 by the SMPTE and it was used to a small extent in Europe and Asia and saw some use in the US, notably by the Fox news channel, but was a commercial failure compared with Digital Betacam. It was superseded by high definition tapeless formats, D-9 uses a tape shell of the VHS form factor, but the tape itself uses a much higher quality metal particle formulation. The recording system is digital and for video uses DV compression at a 50 Mbit/s bitrate, video is recorded in 4,2,2 component format at a variety of standard definition resolutions, in either 4,3 or 16,9 aspect ratios. Audio is recorded as 16-bit/48 kHz pcm with up to four separate channels, video quality is generally very high, at standard definition, D-9s quality is comparable with Digital Betacam. This variant can also record 8 channels of PCM audio at 16 bits and 48 kHz, the higher data rate and increased tape speed mean that the recording time of any given cassette would be halved. D-9 HD, based on specifications, would have higher quality than Sony HDCAM but lower than Sony HDCAM SR. It is not clear whether this proposed format was ever manufactured or sold, although D-9 uses the same video codec as MiniDV, the video bitrate of D-9 is significantly higher than that of the prosumer format. DVCPRO achieves bitrate parity with D-9 and D-9 HD, but has a tape speed. Some of the D-9 television studio gear is capable of recording with Sel-Sync or pre-read and is provided with four-channel audio like Digital Betacam, serial digital interfaces are also provided. A dockable recorder, the JVC BR-D40, attached to a variety of cameras, and there was a one-piece camcorder, jVCs Japanese D-9 product page Betacam Digital Betacam HDCAM D-VHS
19.
Rec. 601
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It includes methods of encoding 525-line 60 Hz and 625-line 50 Hz signals, both with an active region covering 720 luminance samples and 360 chrominance samples per line. The color encoding system is known as YCbCr 4,2,2, the standard has been revised several times in its history. Its edition 7, referred to as BT. 601-7, was approved in March 2011 and was published in October 2011. The Rec.601 signal can be regarded as if it is a digitally encoded analog component video signal, regardless of the frame rate, the luminance sampling frequency is 13.5 MHz. The samples are uniformly quantized using 8 or 10 bit PCM codes in the YCbCr domain, for each 8 bit luminance sample, the nominal value to represent black is 16 and the value for white is 235. Eight-bit code values from 1 through 15 provide footroom, and can be used to accommodate transient signal content such as filter undershoots, similarly, code values 236 through 254 provide headroom and can be used to accommodate transient signal content such as filter overshoots. The values 0 and 255 are used to encode the sync pulses and are forbidden within the picture area. The Cb and Cr samples are unsigned and use the value 128 to encode the neutral color difference value, as used when encoding a white, slightly different primaries are specified for the 625 line and 525 line systems. Rec.601 defines a nonlinear transfer function which is linear near 0 and then transfers to a gamma curve for the rest of the light intensity range. E = {4.500 L L <0.0181.099 L0.45 −0.099 L ≥0.018 The CCIR received a 1982–83 Technology,709, the corresponding standard for high-definition television Rec. 2020, ITU-R Recommendation for ultra-high-definition television ITU-R BT.656, ITU-R Recommendation for parallel and serial transmission formats for BT.601 video Pixel aspect ratio
20.
D-1 (Sony)
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D-1 or 4,2,2 Component Digital is a SMPTE digital recording video standard, introduced in 1986 through efforts by SMPTE engineering committees. It started as a Sony and Bosch - BTS product and was the first major professional digital video format, SMPTE standardized the format within ITU-R601, also known as Rec. 601, which was derived from SMPTE 125M and EBU 3246-E standards, D-1 or 4,2,2 D-1 was a major feat in real time, broadcast quality digital video recording. The uncompressed component video used enormous bandwidth,173 Mbit/sec, for its time, the maximum record time on a D-1 tape is 94 minutes. Hard drives in the 1980s that stored broadcast-quality video would only hold 30 seconds to a few minutes of space. By contrast, the D-1 machine allowed 94 minutes of recording on a $200 cassette, D-1 resolution is 720 ×486 for NTSC systems and 720 ×576 for PAL systems, these resolutions come from Rec. The D1 units are switchable between NTSC and PAL, luma is sampled at 13.5 MHz and Chroma at 6.75 MHz with an overall data rate of 27 MHz. Sampling at 13.5 MHz was used as it is a multiple of NTSC/PAL line rate. The first input/output interface was a 25 pin parallel cable and later updated to serial digital interface on coaxial cable, ancillary data can be put in H/V blanking intervals. Color space for Y’ B’-Y’ R’-Y’ is also defined in ITU Rec.601 or Rec.709 color space, panasonics D-5 format has similar specifications, but sampled at 10-bits as opposed to D-1s 8-bits. It had the advantage of development time as it was introduced later than Sonys D-1. The D-2 format system from Sony and Ampex soon followed two years later, using video in order to lower the bandwidth needed. This reduced D-2s price tag to half that of D-1, since D-2 was composite digital as opposed to component, it could easily be dropped into the space and infrastructure of composite analog machines presently used at the time. Since less information was recorded on D-2 than on D-1, tape speed could be reduced, however, D-2 was still a compromise, being composite video. As broadcasters would later convert from analog to digital wiring, component digital infrastructure became feasible, Sonys popular component Digital Betacam would usher the transition of keeping the colors separated in component digital space rather than combined together in composite space. Digital Betacam could play previous analog Betacam/Betacam SP tapes – which by now – had built an archive for broadcasters using its 1/2-inch tape format. 1/2-inch Digital Betacam thus became the de facto standard-definition broadcast editing, delivery, even as HD broadcasting and delivery became more commonplace in the U. S. after 2008-2010, networks would often require standard definition copies on Digital Betacam. Television shows such as CBS The Rachael Ray Show was still recorded and archived on Digital Betacam as late as 2012, early D-1 operations were plagued with difficulties, though the format quickly stabilized and is still renowned for its superb standard definition image quality
21.
XDCAM
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XDCAM is a series of products for digital recording using random access solid-state memory media, introduced by Sony in 2003. Four different product lines – the XDCAM SD, XDCAM HD, XDCAM EX and XDCAM HD422 – differ in types of encoder used, frame size, container type, none of the later products have made earlier product lines obsolete. Sony maintains that different formats within XDCAM family have been designed to different applications. The XDCAM range includes cameras and decks which act as replacements for traditional VTRs allowing XDCAM discs to be used within a traditional videotape-based workflow. These decks can also serve as random access computer hard drives for easy import of the data files into non-linear editing systems via FireWire. In September 2008, JVC announced its alliance with Sony to support the XDCAM EX format, in August 2009, Convergent Design began shipping the nanoFlash Portable Recorder, which uses the Sony XDCAM HD422 codec. In November 2012, VITEC began shipping the FS-T2001 Portable Recorder, the XDCAM format uses multiple video compression methods and media container formats. Video is recorded with DV, MPEG-2 Part 2 or MPEG-4 compression schemes, DV is used for standard definition video, MPEG-2 is used both for standard and high definition video, while MPEG-4 is used for proxy video. Audio is recorded in uncompressed PCM form for all formats except proxy video, equipment that uses Professional Disc as well as XDCAM4,2,2 on SxS cards as recording media employs MXF container to store digital audio/digital video streams. Tapeless camcorders that record onto solid-state memory cards, use MP4 container for high definition audio/video, JVC camcorders that use XDCAM EX recording format, are also capable of recording into QuickTime container besides using MP4 container. DVCAM uses standard DV encoding, which runs at 25 Mbit/s, some camcorders that allow DVCAM recording can record progressive-scan video. MPEG IMX allows recording in standard definition, using MPEG-2 encoding at data rate of 30,40 or 50 megabits per second, unlike most other MPEG-2 implementations, IMX uses intraframe compression with each frame having the same exact size in bytes to simplify recording onto video tape. Sony claims that at 50 Mbit/s it offers visual quality that is comparable to Digital Betacam MPEG IMX is not supported in the XDCAM EX product line, MPEG HD is used in all product lines except for XDCAM SD. This format supports multiple frame sizes, frame rates, scanning types, depending on product line or a particular model, not all modes of this format may be available. MPEG HD422 doubles the chroma horizontal resolution compared to the generations of high-definition video XDCAM formats. To accommodate the improved chroma detail, video bitrate has been increased to 50 Mbit/s and this format is used only in XDCAM HD422 products. Proxy AV is used to record low resolution proxy videos and this format employs MPEG-4 video encoding at 1.5 Mbit/s with 64 kbit/s for each audio channel. This disc is similar to Blu-ray Disc and holds either 23 GB of data,50 GB,100 GB or 128 GB, essentially, the Professional Disc format was deemed to be a suitable, cost effective and easy step forward
22.
Digital cinematography
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Digital cinematography is the process of capturing film using digital image sensors rather than through film stock. As digital technology has improved in recent years, this practice has become dominant, since the mid 2010s most of the movies across the world are captured as well as distributed digitally. Some filmmakers still prefer to use analogue picture formats to achieve the desired results, beginning in the late 1980s, Sony began marketing the concept of electronic cinematography, utilizing its analog Sony HDVS professional video cameras. The effort met with little success. However, this led to one of the earliest digitally shot feature movies, rainbow was the worlds first all digital film. The Digital High Definition image was transferred to 35mm negative via electron beam recorder for theatrical release, shot and released in 1998, The Last Broadcast is believed by some to be the first feature-length video shot and edited entirely on consumer-level digital equipment. The digital footage blended seamlessly with the shot on film. Also in 1999, digital projectors were installed in four theaters for the showing of The Phantom Menace, in June 2000, Star Wars, Episode II – Attack of the Clones began principal photography shot entirely using a Sony HDW-F900 camera as Lucas had previously stated. The film was released in May 2002, two lesser-known movies, Vidocq and Russian Ark, had also been shot with the same camera, the latter notably consisting of a single long take. Today, cameras from companies like Sony, Panasonic, JVC, at the high-end of the market, there has been an emergence of cameras aimed specifically at the digital cinema market. In late 2013, Paramount became the first major studio to distribute movies to theaters in digital format eliminating 35mm film entirely, anchorman 2 was the last Paramount production to include a 35mm film version, while The Wolf of Wall Street was the first major movie distributed entirely digitally. Digital cinematography captures motion pictures digitally in an analogous to digital photography. The term is applied when digital acquisition is substituted for video acquisition. Independent filmmakers have also pressed low-cost consumer and prosumer cameras into service for digital filmmaking, Digital cinematography cameras capture images using CMOS or CCD sensors, usually in one of two arrangements. Single chip cameras designed specifically for the digital cinematography market often use a single sensor and their large sensors also let these cameras achieve the same shallow depth of field as 35 or 65 mm motion picture film cameras, which many cinematographers consider an essential visual tool. Unlike other video formats, which are specified in terms of vertical resolution, here the K has a customary meaning corresponding to the binary prefix kibi. For instance, a 2K image is 2048 pixels wide, and this led to a plethora of motion-picture related video resolutions, which is quite confusing and often redundant with respect to nowadays few projection standards. All formats designed for digital cinematography are progressive scan, and capture usually occurs at the same 24 frame per second rate established as the standard for 35mm film
23.
NTSC
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The first NTSC standard was developed in 1941 and had no provision for color. In 1953 a second NTSC standard was adopted, which allowed for television broadcasting which was compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system and remained dominant until 1997, North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries are adopting or have adopted other standards instead of ATSC. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on January 1,2010, the majority of NTSC transmissions ended in Japan on July 24,2011, with the Japanese prefectures of Iwate, Miyagi, and Fukushima ending the next year. In March 1941, the committee issued a standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association. Technical advancements of the side band technique allowed for the opportunity to increase the image resolution. The NTSC selected 525 scan lines as a compromise between RCAs 441-scan line standard and Philcos and DuMonts desire to increase the number of lines to between 605 and 800. The standard recommended a frame rate of 30 frames per second, other standards in the final recommendation were an aspect ratio of 4,3, and frequency modulation for the sound signal. In January 1950, the committee was reconstituted to standardize color television, in December 1953, it unanimously approved what is now called the NTSC color television standard. The compatible color standard retained full backward compatibility with existing black-and-white television sets, Color information was added to the black-and-white image by introducing a color subcarrier of precisely 315/88 MHz. These changes amounted to 0.1 percent and were tolerated by existing television receivers. The FCC had briefly approved a different color standard, starting in October 1950. However, this standard was incompatible with black-and-white broadcasts and it used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second. CBS rescinded its system in March 1953, and the FCC replaced it on December 17,1953, with the NTSC color standard, later that year, the improved TK-41 became the standard camera used throughout much of the 1960s. The NTSC standard has been adopted by countries, including most of the Americas. With the advent of television, analog broadcasts are being phased out. Most US NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009, low-power stations, Class A stations and translators were required to shut down by 2015. NTSC color encoding is used with the System M television signal, each frame is composed of two fields, each consisting of 262.5 scan lines, for a total of 525 scan lines
24.
PAL
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Phase Alternating Line is a colour encoding system for analogue television used in broadcast television systems in most countries broadcasting at 625-line /50 field per second. Other common colour encoding systems are NTSC and SECAM, all the countries using PAL are currently in process of conversion or have already converted standards to DVB, ISDB or DTMB. This page primarily discusses the PAL colour encoding system, the articles on broadcast television systems and analogue television further describe frame rates, image resolution and audio modulation. To overcome NTSCs shortcomings, alternative standards were devised, resulting in the development of the PAL, the goal was to provide a colour TV standard for the European picture frequency of 50 fields per second, and finding a way to eliminate the problems with NTSC. PAL was developed by Walter Bruch at Telefunken in Hannover, Germany, with important input from Dr. Kruse, the format was patented by Telefunken in 1962, citing Bruch as inventor, and unveiled to members of the European Broadcasting Union on 3 January 1963. When asked, why the system was named PAL and not Bruch the inventor answered that a Bruch system would not have sold very well. The first broadcasts began in the United Kingdom in June 1967, the one BBC channel initially using the broadcast standard was BBC2, which had been the first UK TV service to introduce 625-lines in 1964. Telefunken PALcolor 708T was the first PAL commercial TV set and it was followed by Loewe-Farbfernseher S920 & F900. Telefunken was later bought by the French electronics manufacturer Thomson, Thomson also bought the Compagnie Générale de Télévision where Henri de France developed SECAM, the first European Standard for colour television. The term PAL was often used informally and somewhat imprecisely to refer to the 625-line/50 Hz television system in general, accordingly, DVDs were labelled as PAL or NTSC even though technically the discs do not carry either PAL or NTSC composite signal. CCIR 625/50 and EIA 525/60 are the names for these standards, PAL. Both the PAL and the NTSC system use a quadrature amplitude modulated subcarrier carrying the chrominance information added to the video signal to form a composite video baseband signal. The frequency of this subcarrier is 4.43361875 MHz for PAL and NTSC4.43, the SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarriers 4.25000 and 4.40625 MHz. Early PAL receivers relied on the eye to do that cancelling, however. The effect is that phase errors result in changes, which are less objectionable than the equivalent hue changes of NTSC. In any case, NTSC, PAL, and SECAM all have chrominance bandwidth reduced greatly compared to the luminance signal. The 4.43361875 MHz frequency of the carrier is a result of 283.75 colour clock cycles per line plus a 25 Hz offset to avoid interferences. Since the line frequency is 15625 Hz, the carrier frequency calculates as follows,4.43361875 MHz =283.75 ×15625 Hz +25 Hz
25.
SECAM
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SECAM, also written SÉCAM, is an analogue colour television system first used in France. It was one of three major television standards, the others being the European PAL and North American NTSC. Development of SECAM began in 1956 by a led by Henri de France working at Compagnie Française de Télévision. The first SECAM broadcast was made in France in 1967, making it the first such standard to go live in Europe, the system was also selected as the standard for colour in the Soviet Union, who began broadcasts shortly after the French. The standard spread from these two countries to many client states and former colonies, SECAM remained a major standard into the 2000s. It is in the process of being phased out and replaced by DVB, work on SECAM began in 1956. The technology was ready by the end of the 1950s, a version of SECAM for the French 819-line television standard was devised and tested, but not introduced. The first proposed system was called SECAM I in 1961, followed by studies to improve compatibility. These improvements were called SECAM II and SECAM III, with the latter being presented at the 1965 CCIR General Assembly in Vienna, further improvements were SECAM III A followed by SECAM III B, the adopted system for general use in 1967. Soviet technicians were involved in the development of the standard, and created their own incompatible variant called NIR or SECAM IV, the team was working in Moscows Telecentrum under the direction of Professor Shmakov. The NIR designation comes from the name of the Nautchno-Issledovatelskiy Institut Radio, two standards were developed, Non-linear NIR, in which a process analogous to gamma correction is used, and Linear NIR or SECAM IV that omits this process. SECAM was inaugurated in France on 1 October 1967, on la deuxième chaîne, a group of four suited men—a presenter and three contributors to the systems development—were shown standing in a studio. Following a count from 10, at 2,15 pm the black-and-white image switched to color, in 1967, CLT of Lebanon became the third television station in the world, after the Soviet Union and France, to broadcast in color utilizing the French SECAM technology. The first color television sets cost 5000 Francs, color TV was not very popular initially, only about 1500 people watched the inaugural program in color. A year later, only 200,000 sets had been sold of an expected million and this pattern was similar to the earlier slow build-up of color television popularity in the US. SECAM was later adopted by former French and Belgian colonies, Greece, the Soviet Union and Eastern bloc countries, and Middle Eastern countries. However, with the fall of communism, and following a period when multi-standard TV sets became a commodity, other countries, notably the United Kingdom and Italy, briefly experimented with SECAM before opting for PAL. Since late 2000s, SECAM is in the process of being phased out, some have argued that the primary motivation for the development of SECAM in France was to protect French television equipment manufacturers
26.
International Organization for Standardization
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The International Organization for Standardization is an international standard-setting body composed of representatives from various national standards organizations. Founded on 23 February 1947, the organization promotes worldwide proprietary and it is headquartered in Geneva, Switzerland, and as of March 2017 works in 162 countries. It was one of the first organizations granted general consultative status with the United Nations Economic, ISO, the International Organization for Standardization, is an independent, non-governmental organization, the members of which are the standards organizations of the 162 member countries. It is the worlds largest developer of international standards and facilitates world trade by providing common standards between nations. Nearly twenty thousand standards have been set covering everything from manufactured products and technology to food safety, use of the standards aids in the creation of products and services that are safe, reliable and of good quality. The standards help businesses increase productivity while minimizing errors and waste, by enabling products from different markets to be directly compared, they facilitate companies in entering new markets and assist in the development of global trade on a fair basis. The standards also serve to safeguard consumers and the end-users of products and services, the three official languages of the ISO are English, French, and Russian. The name of the organization in French is Organisation internationale de normalisation, according to the ISO, as its name in different languages would have different abbreviations, the organization adopted ISO as its abbreviated name in reference to the Greek word isos. However, during the meetings of the new organization, this Greek word was not invoked. Both the name ISO and the logo are registered trademarks, the organization today known as ISO began in 1926 as the International Federation of the National Standardizing Associations. ISO is an organization whose members are recognized authorities on standards. Members meet annually at a General Assembly to discuss ISOs strategic objectives, the organization is coordinated by a Central Secretariat based in Geneva. A Council with a membership of 20 member bodies provides guidance and governance. The Technical Management Board is responsible for over 250 technical committees, ISO has formed joint committees with the International Electrotechnical Commission to develop standards and terminology in the areas of electrical and electronic related technologies. Information technology ISO/IEC Joint Technical Committee 1 was created in 1987 to evelop, maintain, ISO has three membership categories, Member bodies are national bodies considered the most representative standards body in each country. These are the members of ISO that have voting rights. Correspondent members are countries that do not have their own standards organization and these members are informed about ISOs work, but do not participate in standards promulgation. Subscriber members are countries with small economies and they pay reduced membership fees, but can follow the development of standards
27.
International Electrotechnical Commission
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The IEC also manages three global conformity assessment systems that certify whether equipment, system or components conform to its International Standards. The first International Electrical Congress took place in 1881 at the International Exposition of Electricity, at that time the International System of Electrical and Magnetic Units was agreed to. The IEC was instrumental in developing and distributing standards for units of measurement, particularly Gauss, Hertz and it also first proposed a system of standards, the Giorgi System, which ultimately became the SI, or Système International d’unités. In 1938, it published a multilingual international vocabulary to unify terminology relating to electrical, electronic and this effort continues, and the International Electrotechnical Vocabulary remains an important work in the electrical and electronic industries. The CISPR – in English, the International Special Committee on Radio Interference – is one of the groups founded by the IEC, originally located in London, the commission moved to its current headquarters in Geneva in 1948. It has regional centres in Asia-Pacific, Latin America and North America, today, the IEC is the worlds leading international organization in its field, and its standards are adopted as national standards by its members. The work is done by some 10,000 electrical and electronics experts from industry, government, academia, test labs, IEC standards have numbers in the range 60000–79999 and their titles take a form such as IEC60417, Graphical symbols for use on equipment. Following the Dresden Agreement with CENELEC the numbers of older IEC standards were converted in 1997 by adding 60000, for example IEC27 became IEC60027. Standards of the 60000 series are also preceded by EN to indicate that the IEC standard is also adopted by CENELEC as a European standard. The IEC cooperates closely with the International Organization for Standardization and the International Telecommunication Union, Standards developed jointly with ISO such as ISO/IEC26300, ISO/IEC27001, and CASCO ISO/IEC17000 series, carry the acronym of both organizations. The use of the ISO/IEC prefix covers publications from ISO/IEC Joint Technical Committee 1 - Information Technology, as well as conformity assessment standards developed by ISO CASCO, other standards developed in cooperation between IEC and ISO are assigned numbers in the 80000 series, such as IEC 82045-1. IEC standards are also being adopted by other certifying bodies such as BSI, CSA, UL & ANSI/INCITS, SABS, SAI, SPC/GB, IEC standards adopted by other certifying bodies may have some noted differences from the original IEC standard. The IEC is made up of members, called national committees, national committees are constituted in different ways. Some NCs are public sector only, some are a combination of public and private sector, about 90% of those who prepare IEC standards work in industry
28.
H.262/MPEG-2 Part 2
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H.262 or MPEG-2 Part 2 is a video coding format developed and maintained jointly by ITU-T Video Coding Experts Group and ISO/IEC Moving Picture Experts Group. It is the part of the ISO/IEC MPEG-2 standard. The ITU-T Recommendation H.262 and ISO/IEC 13818-2 documents are identical, the standard is available for a fee from the ITU-T and ISO. MPEG-2 Video is similar to MPEG-1, but also support for interlaced video. MPEG-2 video is not optimized for low bit-rates, but outperforms MPEG-1 at 3 Mbit/s, all standards-conforming MPEG-2 Video decoders are fully capable of playing back MPEG-1 Video streams. The ISO/IEC approval process was completed in November 1994, the first edition was approved in July 1995 and published by ITU-T and ISO/IEC in 1996. In 1996 it was extended by two amendments to include the Registration of Copyright Identifiers and the 4,2,2 Profile, ITU-T published these amendments in 1996 and ISO in 1997. There are also other amendments published later by ITU-T and ISO, the most recent edition of the standard was published in 2013 and incorporates all prior amendments. An HDTV camera generates a raw video stream of 149,299,200 bytes per second for 24fps video and this stream must be compressed if digital TV is to fit in the bandwidth of available TV channels and if movies are to fit on DVDs. Fortunately, video compression is practical because the data in pictures is often redundant in space, for example, the sky can be blue across the top of a picture and that blue sky can persist for frame after frame. Also, because of the way the eye works, it is possible to some data from video pictures with almost no noticeable degradation in image quality. TV cameras used in broadcasting usually generate 50 pictures a second or 59.94 pictures a second, digital television requires that these pictures be digitized so that they can be processed by computer hardware. Each picture element is represented by one luma number and two chrominance numbers. These describe the brightness and the color of the pixel, thus, each digitized picture is initially represented by three rectangular arrays of numbers. Upon reception/decoding, the two fields are displayed alternately with the lines of one field interleaving between the lines of the field, this format is called interlaced video. The typical field rate is 50 or 59.94 fields per second, if the video is not interlaced, then it is called progressive video and each picture is a frame. Another common practice to reduce the rate is to thin out or subsample the two chrominance planes. In effect, the chrominance values represent the nearby values that are deleted
29.
DVD-Video
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DVD-Video is a consumer video format used to store digital video on DVD discs, and as of 2003 is the dominant consumer video format in Asia, North America, Europe, and Australia. Discs using the DVD-Video specification require a DVD drive and an MPEG-2 decoder, commercial DVD movies are encoded using a combination MPEG-2 compressed video and audio of varying formats. Typically, the rate for DVD movies ranges from 3 Mbit/s to 9.5 Mbit/s. It was first available in November 1996 in Japan, the DVD-Video specification was created by DVD Forum and can be obtained from DVD Format/Logo Licensing Corporation for a fee of $5,000. The specification is not publicly available and every subscriber must sign a non-disclosure agreement, certain information in the DVD Book is proprietary and confidential. To record moving pictures, DVD-Video uses either H. 262/MPEG-2 Part 2 compression at up to 9.8 Mbit/s or MPEG-1 Part 2 compression at up to 1.856 Mbit/s. DVD-Video supports video with a bit depth of 8-bits per color YCbCr with 4,2,0 chroma subsampling,704 ×480 pixels 352 ×480 pixels. Widescreen video is supported only in D-1 resolutions, the MPEG-1 Part 2 format does not support interlaced video. The H. 262/MPEG-2 Part 2 format supports both interlaced and progressive-scan content, Content with a frame rate different from one of the rates shown above can be encoded to H. 262/MPEG-2 Part 2 by using pulldown. This is most commonly used to encode 23.976 frame/s content for playback at 29.97 frame/s. Alternately, the content can be encoded on the disc itself at one of several alternate frame rates, such flags can be added in video stream by the H. 262/MPEG-2 Part 2 encoder. A DVD player uses these flags to convert progressive content into interlaced video in real-time during playback and these flags also allow reproducing progressive content at their original, non-interlaced format when used with compatible DVD players and progressive-scan television sets. The audio data on a DVD movie can be PCM, DTS, MPEG-1 Audio Layer II, a similar standard exists in countries using the NTSC system, though with no requirement mandating the use of or support for the MP2 format. DTS audio is optional for all players, as DTS was not part of the draft standard and was added later, thus. Only PCM and DTS support 96 kHz sampling rate, because PCM, being uncompressed, requires a lot of bandwidth and DTS is not universally supported by players,96 kHz sampling rate is rare for DVDs. The vast majority of commercial DVD-Video releases today employ AC-3 audio. The official allowed formats for the tracks on a DVD Video are, PCM,48 kHz or 96 kHz sampling rate,16 bit or 24 bit Linear PCM,2 to 6 channels, up to 6,144 kbit/s. DVDs can contain more than one channel of audio to go together with the video content and this is most commonly used for different audio formats – DTS5.1, AC-32.0 etc. – as well as for commentary and audio tracks in different languages
30.
Blu-ray
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Blu-ray or Blu-ray Disc is a digital optical disc data storage format. It was designed to supersede the DVD format, in that it is capable of storing high-definition, the plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Conventional Blu-ray Disc discs contain 25 GB per layer, with dual layer discs being the standard for feature-length video discs. Triple-layer discs and quadruple layers are available for BD-XL re-writer drives, the name Blu-ray refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs. The main application of Blu-ray is as a medium for video material such as films and physical distribution of video games for the PlayStation 3, PlayStation 4. Besides the hardware specifications, Blu-ray is associated with a set of multimedia formats, high-definition video may be stored on Blu-ray discs with up to 2160p resolution, at up to 60 frames per second. DVD discs had been limited to a resolution of 480p or 576p. The BD format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, Sony unveiled the first Blu-ray disc prototypes in October 2000, and the first prototype player was released in April 2003 in Japan. Afterwards, it continued to be developed until its release in June 2006. During the high definition disc format war, Blu-ray Disc competed with the HD DVD format. Toshiba, the company that supported HD DVD, conceded in February 2008. According to Media Research, high-definition software sales in the US were slower in the first two years than DVD software sales, Blu-ray faces competition from video on demand and the continued sale of DVDs. As of January 2016, 44% of U. S. broadband households had a Blu-ray player, the information density of the DVD format was limited by the wavelength of the laser diodes used. Following protracted development, blue laser diodes operating at 405 nanometers became available on a production basis, Sony started two projects in collaboration with Philips applying the new diodes, UDO, and DVR Blue, a format of rewritable discs that would eventually become Blu-ray Disc. The core technologies of the formats are similar, the first DVR Blue prototypes were unveiled at the CEATEC exhibition in October 2000 by Sony. A trademark for the Blue Disc logo was filed February 9,2001, on February 19,2002, the project was officially announced as Blu-ray Disc, and Blu-ray Disc Founders was founded by the nine initial members. The first consumer device arrived in stores on April 10,2003, the Sony BDZ-S77, but there was no standard for prerecorded video, and no movies were released for this player. On October 4,2004, the name Blu-ray Disc Founders was officially changed to the Blu-ray Disc Association, the Blu-ray Disc physical specifications were completed in 2004
31.
HDV
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HDV is a format for recording of high-definition video on DV cassette tape. The format was developed by JVC and supported by Sony, Canon. The four companies formed the HDV consortium in September 2003, HDV and HDV logo are trademarks of JVC and Sony. HDV video and audio are encoded in digital form, using lossy interframe compression, video is encoded with the H. 262/MPEG-2 Part 2 compression scheme, using 8-bit chroma and luma samples with 4,2,0 chroma subsampling. Stereo audio is encoded with the MPEG-1 Layer 2 compression scheme, the compressed audio and video are multiplexed into an MPEG-2 transport stream, which is typically recorded onto magnetic tape, but can also be stored in a computer file. The data rate for both the audio and video is constant and is roughly the same as DV data rate, in contrast to the video, HDV audio bitrate is relatively generous. At the coded bitrate of 384 kbit/s, MPEG-1 Layer 2 audio is regarded as perceptually lossless, two major versions of HDV are HDV 720p and HDV 1080i. The former is used by JVC and is known as HDV1. The latter is preferred by Sony and Canon and is referred to as HDV2. The HDV 1080i defines optional progressive recording modes, and in recent publications is sometimes called HDV1080 or 1080-line HDV as progressive 1080-line recording becomes commonplace, HDV 720p format allows recording high definition video as well as progressive-scan standard definition video. HDV-HD closely matches broadcast 720p progressive scan video standard in terms of scanning type, frame size, aspect ratio, earlier HDV 720p camcorders could shoot only at 24,25 and 30 frames per second. Later models offer both film-like and reality-like frame rates, HDV-SD is a mode for recording progressive-scan standard definition video. Such a video is called enhanced definition video, but is considered high definition video in Australia. Depending on region, HDV-SD video is recorded either as 576p50 or as 480p60, like DVCPRO Progressive, HDV-SD was meant as an intermediate format during the transition time from standard definition to high definition video. Later models of HDV 720p camcorders do not record in this mode, JVC was the only manufacturer of HDV 720p camcorders. JVC was the first to release an HDV camcorder, the handheld GR-HD1, later JVC shifted its HDV development to shoulder-mounted cameras. A common misconception is that JVC developed an extension to HDV called ProHD, featuring film-like 24-frame/s progressive recording mode and LPCM audio. JVC has clarified that ProHD is not a video recording format, but an approach for delivering affordable HD products, Sony adapted HDV, originally conceived as progressive-scan format by JVC, to interlaced video
32.
AVCHD
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AVCHD is a file-based format for the digital recording and playback of high-definition video. Developed jointly by Sony and Panasonic, the format was introduced in 2006 primarily for use in high definition consumer camcorders, favorable comparisons of AVCHD against HDV and XDCAM EX solidified perception of AVCHD as a format acceptable for professional use. Both Panasonic and Sony released the first consumer AVCHD camcorders in spring of 2007, Panasonic released the first AVCHD camcorder aimed at the professional market in 2008, though it was nothing more than the FLASH card consumer model rebadged with a different model number. In 2011 the AVCHD specification was amended to include 1080-line 50-frame/s and 60-frame/s modes, the new video modes require double the data rate of previous modes. AVCHD and its logo are trademarks of Sony and Panasonic, for video compression, AVCHD uses the MPEG-4 AVC/H.264 standard, supporting a variety of standard, high definition, and stereoscopic video resolutions. For audio compression, it supports both Dolby AC-3 and uncompressed linear PCM audio, stereo and multichannel surround are both supported. Aside from recorded audio and video, AVCHD includes many features to improve media presentation, menu navigation, simple slide shows. The menu navigation system is similar to DVD-video, allowing access to individual videos from a common intro screen, slide shows are prepared from a sequence of AVC still frames, and can be accompanied by a background audio track. Subtitles are used in some camcorders to timestamp the recordings, audio, video, subtitle, and ancillary streams are multiplexed into an MPEG transport stream and stored on media as binary files. Usually, memory cards and HDDs use the FAT file system, at the file system level, the structure of AVCHD is derived from the Blu-ray Disc specification, but is not identical to it. In particular, it uses legacy 8.3 file naming convention, another difference is location of the BDMV directory, which contains media files. On a DVD-based camcorder the BDMV directory is placed at the root level, on the HDD-based Canon HG10 camcorder the BDMV directory is located in the AVCHD directory, which is placed at the root level. Solid-state Panasonic and Canon camcorders nest the AVCHD directory inside the PRIVATE directory, following a standard agreed upon by many still camera manufacturers, solid-state camcorders have a root-level DCIM directory for still images. AVCHD recordings can be transferred to a computer by connecting the camcorder via the USB connection, removable media like SDHC and Memory Stick cards or DVDs can be read on a computer directly. Copying files from an AVCHD camcorder or from removable media can be performed faster than from a tape-based camcorder, just as editing DVCPRO HD and HDV video once demanded an expensive high-end computer, AVCHD editing software requires powerful machines. Compared to HDV, AVCHD requires 2-4x the processing power for realtime playback, placing a burden on the computers CPU. Improvements in multi-core computing and graphics processor acceleration bring AVCHD playback to mainstream desktops and laptops, AVCHD supports a variety of video resolutions and scanning methods, which was further extended with the 2011 amendment of the specification. The licensing body of the specification defines a variety of labels for products compliant with specific features, most AVCHD camcorders support only a handful of the video and audio formats allowed in the AVCHD standard
33.
Interlaced video
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Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured at two different times and this enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon. This effectively doubles the resolution as compared to non-interlaced footage. Interlaced signals require a display that is capable of showing the individual fields in a sequential order. CRT displays and ALiS plasma displays are made for displaying interlaced signals, Interlaced scan refers to one of two common methods for painting a video image on an electronic display screen by scanning or displaying each line or row of pixels. This technique uses two fields to create a frame, one field contains all odd-numbered lines in the image, the other contains all even-numbered lines. A Phase Alternating Line -based television set display, for example, the two sets of 25 fields work together to create a full frame every 1/25 of a second, but with interlacing create a new half frame every 1/50 of a second. To display interlaced video on progressive displays, playback applies deinterlacing to the video signal. The European Broadcasting Union has argued against interlaced video in production and they recommend 720p 50 fps for the current production format—and are working with the industry to introduce 1080p 50 as a future-proof production standard. 1080p 50 offers higher vertical resolution, better quality at lower bitrates, despite arguments against it, television standards organizations continue to support interlacing. It is still included in digital video formats such as DV, DVB. Progressive scan captures, transmits, and displays an image in a similar to text on a page—line by line. The interlaced scan pattern in a CRT display also completes such a scan, the first pass displays the first and all odd numbered lines, from the top left corner to the bottom right corner. The second pass displays the second and all even numbered lines and this scan of alternate lines is called interlacing. A field is an image that contains only half of the lines needed to make a complete picture, persistence of vision makes the eye perceive the two fields as a continuous image. In the days of CRT displays, the afterglow of the displays phosphor aided this effect, interlacing provides full vertical detail with the same bandwidth that would be required for a full progressive scan of twice the perceived frame rate and refresh rate. To prevent flicker, all analog broadcast television systems used interlacing, format identifiers like 576i 50 and 720p 50 specify the frame rate for progressive scan formats, but for interlaced formats they typically specify the field rate. This can lead to confusion, because industry-standard SMPTE timecode formats always deal with frame rate, not field rate
34.
Gamut
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In color reproduction, including computer graphics and photography, the gamut, or color gamut /ˈɡæmət/, is a certain complete subset of colors. The most common refers to the subset of colors which can be accurately represented in a given circumstance. Another sense, less used but not less correct, refers to the complete set of colors found within an image at a given time. In the 1850s, the term was applied to a range of colors or hue, for example by Thomas De Quincey, in color theory, the gamut of a device or process is that portion of the color space that can be represented, or reproduced. When certain colors cannot be expressed within a color model. For example, while pure red can be expressed in the RGB color space, it cannot be expressed in the CMYK color space, a device that is able to reproduce the entire visible color space is an unrealized goal within the engineering of color displays and printing processes. While modern techniques allow increasingly good approximations, the complexity of systems often makes them impractical. While processing an image, the most convenient color model used is the RGB model. Printing the image requires transforming the image from the original RGB color space to the printers CMYK color space, during this process, the colors from the RGB which are out of gamut must be somehow converted to approximate values within the CMYK space gamut. Simply trimming only the colors which are out of gamut to the closest colors in the space would burn the image. There are several algorithms approximating this transformation, but none of them can be truly perfect and this is why identifying the colors in an image which are out of gamut in the target color space as soon as possible during processing is critical for the quality of the final product. Gamuts are commonly represented as areas in the CIE1931 chromaticity diagram as shown at right, the cone drawn in grey corresponds roughly to the CIE diagram at right, with the added dimension of brightness. The axes in these diagrams are the responses of the short-wavelength, middle-wavelength, the other letters indicate black, red, green, blue, cyan, magenta, yellow, and white colors. The exact positions of the apexes depends on the spectra of the phosphors in the computer monitor. The gamut of the CMYK color space is, ideally, approximately the same as that for RGB, with slightly different apexes, depending on both the exact properties of the dyes and the light source. In practice, due to the way raster-printed colors interact with other and the paper and due to their non-ideal absorption spectra. The gamut of colors in nature has a similar, though more rounded. An object that only a narrow band of wavelengths will have a color close to the edge of the CIE diagram
35.
YUV
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YUV is a color space typically used as part of a color image pipeline. The scope of the terms Y′UV, YUV, YCbCr, YPbPr, etc. is sometimes ambiguous, today, the term YUV is commonly used in the computer industry to describe file-formats that are encoded using YCbCr. The Y′UV model defines a space in terms of one luma. The Y′UV color model is used in the PAL and SECAM composite color video standards, previous black-and-white systems used only luma information. The YPbPr color model used in analog component video and its digital version YCbCr used in video are more or less derived from it. The Y′IQ color space used in the analog NTSC television broadcasting system is related to it, as for etymology, Y, Y′, U, and V are not abbreviations. The use of the letter Y for luminance can be traced back to the choice of X Y Z primaries and this lends itself naturally to the usage of the same letter in luma, which approximates a perceptually uniform correlate of luminance. Likewise, U and V were chosen to differentiate the U and V axes from those in other spaces, see the equations below or compare the historical development of the math. Y′UV was invented when engineers wanted color television in a black-and-white infrastructure and they needed a signal transmission method that was compatible with black-and-white TV while being able to add color. The luma component already existed as the black and white signal, the UV representation of chrominance was chosen over straight R and B signals because U and V are color difference signals. This meant that in a black and white scene the U and V signals would be zero, if R and B were to have been used, these would have non-zero values even in a B&W scene, requiring all three data-carrying signals. In addition, black and white receivers could take the Y′ signal and ignore the signals, making Y′UV backward-compatible with all existing black-and-white equipment. It was necessary to assign a narrower bandwidth to the channel because there was no additional bandwidth available. If some of the information arrived via the chrominance channel. Y′UV signals are created from RGB source. Weighted values of R, G, and B are summed to produce Y′, U and V are computed as scaled differences between Y′ and the B and R values. BT.601 defines the following constants, W R =0.299, W G =1 − W R − W B =0.587, W B =0.114, U max =0.436, V max =0.615. The resulting ranges of Y′, U, and V respectively are, equivalently, substituting values for the constants and expressing them as matrices gives these formulas for BT.601, =, =
36.
International Commission on Illumination
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The International Commission on Illumination 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 and is based in Vienna. The President from 2015 is Yoshihiro Ohno from the US, in 1976, the commission developed the CIELAB and CIELUV colour spaces, which are widely used today. Based on CIELAB, colour difference formulas CIEDE94 and CIEDE2000 were recommended in the corresponding years
37.
Society of Motion Picture and Television Engineers
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SMPTE Membership is open to any individual or organization with interest in the subject matter. SMPTE standards documents are copyrighted and may be purchased from the SMPTE website, standard documents may be purchased by the general public. Significant standards promulgated by SMPTE include, All film and television formats and media. The society sponsors many awards, the oldest of which are the SMPTE Progress Medal, the Samuel Warner Memorial Medal, SMPTE also has a number of student Chapters and sponsors scholarships for college students in the motion imaging disciplines. A group within the standards committees has begun to work on the definition of the SMPTE 3D Home Master. SMPTE, instituted in 1999, a committee for the foundations of Digital Cinema. The SMPTE presents awards to individuals for outstanding contributions in fields of the society, James Cameron Edwin Catmull Birney Dayton Clyde D. Smith Roderick Snell Dr. Kees Immink Stanley N. Baron William C. Miller Bernard J. Lechner Ray Dolby Harold E. Edgerton Vladimir K. Zworykin John G. Frayne Walt Disney Chuck Pagano James M. DeFilippis Bernard J. Lechner Stanley N. Baron William F. Schreiber Adrian Ettlinger Joseph A. Flaherty, goldmark W. R. G. Baker Albert Rose Charles Ginsburg Robert E. Shelby Arthur V. Loughren Otto H. Recent recipients are Andrew Laszlo James MacKay Dr. Roderick T. Swartz
