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- Number of terms: 20560
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Tektronix provides test and measurement instruments, solutions and services for the computer, semiconductor, military/aerospace, consumer electronics and education industries worldwide.
a) The descriptive and supporting data that is connected to the program or the program elements. It is intended to both aid the direct use of program content and support the retrieval of content as needed during the post-production process. b) Generally referred to as “data about data” or “data describing other data.” More specifically, information that is considered ancillary to or otherwise directly complementary to the essence.
Any information that a content provider considers useful or of value when associated with the essence being provided.
Industry:Software
Circuit that connects signals from external devices as inputs to the microprocessor system.
Industry:Software
Video originates with linear-light (tristimulus) RGB primary components, conventionally contained in the range 0 (black) to +1 (white). From the RGB triple, three gamma-corrected primary signals are computed; each is essentially the 0.45-power of the corresponding tristimulus value, similar to a square-root function. In a practical system such as a television camera, however, in order to minimize noise in the dark regions of the picture it is necessary to limit the slope (gain) of the curve near black. It is now standard to limit gain to 4.5 below a tristimulus value of +0.018, and to stretch the remainder of the curve to place the Y-intercept at –0.099 in order to maintain function and tangent continuity at the breakpoint:
#Rgamma = 1.099 * pow (R,0.45) - 0.099
#0.099 Ggamma = 1.099 * pow (G,0.45) - 0.099
#0.099 Bgamma = 1.099 * pow (B,0.45) - 0.099
Luma is then computed as a weighted sum of the gamma-corrected primaries:
#Y = 0.299 * Rgamma + 0.587 * Ggamma + 0.114 * Bgamma
The three coefficients in this equation correspond to the sensitivity of human vision to each of the RGB primaries standardized for video. For example, the low value of the blue coefficient is a consequence of saturated blue colors being perceived as having low brightness. The luma coefficients are also a function of the white point (or chromaticity of reference white). Computer users commonly have a white point with a color temperature in the range of 9300 K, which contains twice as much blue as the daylight reference CIE D65 used in television. This is reflected in pictures and monitors that look too blue. Although television primaries have changed over the years since the adoption of the NTSC standard in 1953, the coefficients of the luma equation for 525- and 625-line video have remained unchanged. For HDTV, the primaries are different and the luma coefficients have been standardized with somewhat different values. The signal which represents brightness, or the amount of light in the picture.
This is the only signal required for black and white pictures; for color systems it is obtained as the weighted sum (Y = 0.3R + 0.59G + 0.11B) of the R, G, and B signals.
Luminance Factor – At a surface element of a nonself-radiating medium, in a given direction, under specified conditions of illumination, ratio of the luminance of the surface element in the given direction to that of a perfect reflecting or transmitting diffuser identically illuminated. No “perfect reflectors” exist, but properly prepared magnesium oxide has a luminance factor equal to 98% and this is usually employed to define the scale.
Industry:Software
Unwanted electrical signals produced by electronic equipment or by magnetic tape. Mostly confined to the extremes of the audible frequency spectrum where it occurs as hum and/or hiss. A-weighted noise is noise measured within the audio frequency band using a measuring instrument that has a frequency selective characteristic. The frequency sensitivity of the measuring instrument is adjusted to correspond to that of the average human hearing response.
Industry:Software
Vertical resolution of a scanned image subjectively evaluated is consistently shown to be less than the geometrically-predicted resolution.
Observations are usually stated in terms of the ratio of perceived television lines to active lines present in the display. From the time that R. Kelt published his studies (conducted on a progressive scanned image), there have been numerous numerical values and substantiating theories proposed for this effect. The range of results suggests that many details of the experiments influence the result and make defining a single “Kell Factor” impossible. Reported experimental results range at least between 0.5 and 0.9. In an otherwise comparable display, the “ratio” is lower for interlaced scanning than for progressive scanning.
Industry:Software
The standard database of approved, registered data element tags, their definitions and their allowed formats.
Industry:Software
a) Typically refers to sending information or data signals to and from devices. b) Lines or devices used to transfer information outside the system.
Industry:Software
A key wherein the keying signal is derived from the instantaneous luminance of a video signal after chroma has been filtered out. That is, for a particular clip level, all parts of a scene that are brighter than that level will appear keyed in, leaving background video everywhere else.
Industry:Software
A description of a picture with abnormal or spurious pixel values.
The picture’s noise is a random variation in signal interfering with the information content.
Industry:Software
A number describing the loss of vertical resolution from that expected for the number of active scanning lines. Named for Ray Kell, a researcher at RCA Laboratories. Many researchers have come up with different Kell factors for progressively scanned television systems. These differences are based on such factors as aperture shape, image content, and measurement technique. A generally accepted figure for the Kell factor is around 0.68, which, multiplied by the 484 active NTSC scanning lines, yields a vertical resolution of 330 lines, matched by NTSC’s 330 lines of horizontal resolution per picture height (see Square Pixels). It is important to note that most studies of the Kell factor measure resolution reduction in a progressive scanning system. Interlaces scanning systems suffer from both a Kell factor and an interlace coefficient.
Industry:Software
