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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 term used to describe the chaining of a video signal through several video devices (distribution amplifiers, VCRs, monitors, etc.). A VCR may be hooked up to a distribution amplifier which is supplied with a video input connector and a loop output connector. When a signal is fed to the distribution amplifier, it is also fed unprocessed to the loop output connector (parallel connection) on the distribution amplifier. In turn, the same signal is fed to another device which is attached to the first one and so on. Thus a very large number of VCRs or other video devices can be looped together for multiple processing.
Industry:Entertainment
A scheme that, after decompression, does not produce exactly the same data that was given to the compressor. Due to the nature of image data, the losses are often imperceptible to the human eye. Although image quality may suffer, many experts believe that up to 95 percent of the data in a typical image may be discarded without a noticeable loss in apparent resolution.
Industry:Entertainment
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: amma = (1.099 * pow(R,0.45)) - 0.099 Ggamma = (1.099 * pow(G,0.45)) - 0.099 Bgamma = (1.099 * pow(B,0.45)) - 0.099 Luma is then computed as a weighted sum of the gamma-corrected primaries: = 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 colours being perceived as having low brightness. The luma coefficients are also a function of the white point (or chromaticity of reference whitex). Computer users commonly have a white point with a colour 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.
Industry:Entertainment
The degree of brightness (black and white portion of the video signal) at any given point in the video image. A video signal is comprised of luminance, chrominance (color information) and sync. If luminance is high, the picture is bright and if low the picture is dark. Changing the chrominance does not affect the brightness of the picture. May be measured in lux or foot-candles.
Industry:Entertainment
Communicating a higher-level model of the image than pixels is an active area of research. The idea is to have the transmitter and receiver agree on the basic model for the image; the transmitter then sends parameters to manipulate this model in lieu of picture elements themselves. Model-based decoders are similar to computer graphics rendering programs. The model-based coder trades generality for extreme efficiency in its restricted domain. Better rendering and extending of the domain are research themes.
Industry:Entertainment
Motion Picture Expert Group. Similar to spatial compression of JPEG, but adds frame-to-frame temporal compression. Compaction is typically 3 times better than video JPEG. Like the JPEG standard, it includes options for trading off between storage space and image quality.
Industry:Entertainment
MPEG-1 defines a set of international standards for the compression and decompression of digital video signals. MPEG-1 specifies a video resolution of 352-by-240 pixels compressed at 30 frames per second (fps) at a bandwidth of 150 kilobytes per second.
Industry:Entertainment
MPEG-2 is targeted for use with high-bandwidth broadcast applications specifying 720-by-480 playback at 60 fields per second at data rates ranging from 500 kilobytes per second to more than two megabytes per second. Essentially, MPEG-2 is digital television.
Industry:Entertainment
Refers to the delivery of information that combines different content formats (motion video, audio, still images, graphics, animation, text, etc.). A somewhat ambiguous term that describes the ability to combine audio, video and other information with graphics, control, storage and other features of computer-based systems.
Industry:Entertainment
A general term used in electronics to indicate any unwanted electrical signal, unrelated to the original signal. Video noise is generally manifested as snow, graininess, ghost images or picture static induced by external sources such as the national power-line grid, electric motors, fluorescent lamps, etc. In audio, noise is generally manifested as hiss and static.
Industry:Entertainment
