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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.
The horizontal axis of a graph. When a television signal is examined in one dimension, the x-axis is usually time. When it is examined in three dimensions, the x-axis is usually horizontal resolution.
Industry:Software
A) An abbreviation or symbol for luminance, the black and white information in a television signal. b) Signal which is made up of 0.59G + 0.3R + 0.11B. c) The y-axis of the chart of the spectral sensitivity of the human visual system.
Industry:Software
A generalised set of CAV signals: Y is the luminance signal, C1 is the 1st color-difference signal, and C2 is the 2nd color-difference signal.
Industry:Software
The international standard ITU-R BT.601-1 specifies eight-bit digital coding for component video, with black at luma code 16 and white at luma code 235, and chroma in 8-bit two’s complement form centred on 128 with a peak at code 224. This coding has a slightly smaller excursion for luma than for chroma: luma has 219 risers compared to 224 for Cb and Cr. The notation CbCr distinguishes this set from PbPr where the luma and chroma excursions are identical. For Rec. 601-1, coding is eight bits per component.
: Y_8b = 16 + 219 * 9
: Cb_8b = 128 + 112 * (0.5/0.866) * (Bgamma - Y)
: Cr_8b = 128 + 112 * (0.5/0.701) * (Rgamma - Y)
Some computer applications place black at luma code 0 and white at luma code 255. In this case, the scaling and offsets above can be changed accordingly, although broadcast-quality video requires the accommodation for headroom and footroom provided in the CCIR-601-1 equations. ITU-R BT.601-1 Rec. calls for two-to-one horizontal subsampling of Cb and Cr, to achieve 2/3 the data rate of RGB with virtually no perceptible penalty. This is denoted 4:2:2. A few digital video systems have used horizontal subsampling by a factor of four, denoted 4:1:1. JPEG and MPEG normally subsample Cb and Cr two-to-one horizontally and also two-to-one vertically, to get 1/2 the data rate of RGB. No standard nomenclature has been adopted to describe vertical subsampling. To get good results using subsampling you should not just drop and replicate pixels, but implement proper decimation and interpolation filters. YCbCr coding is employed by D1 component digital video equipment.
Industry:Software
The three nonlinear video signals in which the information has been transformed into a luminance signal and two chrominance signals, each of which has been subject to nonlinear processing, and the chrominance signals at least have also been bandlimited. By convention, C'R, and C'B represent color-difference signals in digital format with typical excursion of values for 16 to 240.
Industry:Software
The human visual system has less spatial acuity for magentagreen transitions than it does for red-cyan. Thus, if signals I and Q are formed from a 123 degree rotation of U and V respectively, the Q signal can be more severely filtered than I (to about 600 kHz, compared to about 1.3 MHz) without being perceptible to a viewer at typical TV viewing distance.
YIQ is equivalent to YUV with a 33 degree rotation and an axis flip in the UV plane. The first edition of W.K. Pratt “Digital Image Processing,” and presumably other authors that follow that bible, has a matrix that erroneously omits the axis flip; the second edition corrects the error. Since an analogue NTSC decoder has no way of knowing whether the encoder was encoding YUV or YIQ, it cannot detect whether the encoder was running at 0 degree or 33 degree phase. In analogue usage, the terms YUV and YIQ are often used somewhat interchangeably. YIQ was important in the early days of NTSC, but most broadcasting equipment now encodes equiband U and V.
The D2 composite digital DVTR (and the associated interface standard) conveys NTSC modulated on the YIQ axes in the 525-line version and PAL modulated on the YUV axes in the 625-line version. The set of CAV signals specified for the NTSC system: Y is the luminance signal, I is the 1st colordifference signal and Q is the 2nd color-difference signal.
Industry:Software
If three components are to be conveyed in three separate channels with identical unity excursions, then the Pb and Pr colour difference components are used. These scale factors limit the excursion of EACH colour difference component to –0.5 … +0.5 with respect to unity Y excursion: 0.886 is just unity less the luma coefficient of blue. In the analogue domain, Y is usually 0 mV (black) to 700 mV (white), and Pb and Pr are usually ±350 mV. YPbPr is part of the CCIR Rec. 709 HDTV standard, although different luma coefficients are used, and it is denoted E'Pb and E'Pr with subscript arrangement too complicated to be written here. YPbPr is employed by component analogue video equipment such as M-II and Betacam; Pb and Pr bandwidth is half that of luma. A version of the (Y, R-Y, B-Y) signals specified for the SMPTE analogue component standard.
Industry:Software
The general set of CAV signals used in the PAL system as well as for some encoder and most decoder applications in the NTSC systems.
Y is the luminance, R-Y is the 1st color-difference signal and B-Y is the 2nd color-difference signal.
Industry:Software
Luminance and colour difference components for PAL systems. Y, U, and V are simply new names for Y, R-Y, and B-Y. The derivation from RGB is identical. In composite NTSC, PAL or S-Video, it is necessary to scale (B-Y) and (R-Y) so that the composite NTSC or PAL signal (luma plus modulated chroma) is contained within the range –1/3 to +4/3. These limits reflect the capability of composite signal recording or transmission channel. The scale factors are obtained by two simultaneous equations involving both B-Y and R-Y, because the limits of the composite excursion are reached at combinations of B-Y and R-Y that are intermediate to primary colors. The scale factors are as follows: U = 0.493 * (B-Y); V = 0.877 * (R-Y). U and V components are typically modulated into a chroma component: C = U * cos(t) + V * sin(t) where t represents the ~3.58 MHz NTSC colour sub-carrier. PAL coding is similar, except that the V component switches Phase on Alternate Lines (±1), and the sub-carrier is at a different frequency, about 4.43 MHz. It is conventional for an NTSC luma signal in a composite environment (NTSC or S-Video) to have 7.5% setup: Y_setup = (3/40) + (37/40) * Y. A PAL signal has zero setup. The two signals Y (or Y_setup) and C can be conveyed separately across an S-Video interface, or Y and C can be combined (encoded) into composite NTSC or PAL: NTSC = Y_setup + C; PAL = Y + C. U and V are only appropriate for composite transmission as 1-wire NTSC or PAL, or 2-wire S-Video. The UV scaling (or the IQ set, described below) is incorrect when the signal is conveyed as three separate components. Certain component video equipment has connectors labelled YUV that in fact convey YPbPr signals.
Industry:Software
