Glossary: Mostlyabreviations and acronyms:
Ask the Deacon                                        
Top AB CD EF GH IJ KL MN OP QR ST UV WX YZ

Y

Y: luminance signal; the amount of black-and-whitein a signal.

Y, Cr, Cb: The digital luminance and colordifference signals in CCIR 601 coding. The Yluminance signal is sampled at l3.5 MHz and the two color difference signalsare sampled at 6.75 MHz co-sited with one of the luminance samples. Cris the digitized version of the analog component (R-Y),likewise Cb is the digitized version of (B-Y).

Yahoo!: Yet Another Hierarchical OfficiousOracle

YIQ: Convenient shorthand commonly - but incorrectly- used to describe the analog luminance and color difference signals incomponent video systems. Y is correct for luminance butI and Q are the two subcarriermodulation axes (I - In-phase and Q- Quadrature) used in the NTSC color coding system.Scaled and filtered versions of the R-Y and B-Ycolor difference signals are used to modulate the NTSCsubcarrier in the Iand Qaxes respectively. The confusion arises because Iand Q are associated with the color differencesignals but clearly they are not the same thing.  YIQ is "simply"a color-encoding system similar to YUV, in which theU and V signals must be carried with equal bandwidth, albeit less thanthat of luminance. However, the human visual system has less spatial acuityfor magenta-green transitions than for red-cyan. Thus, if signals Iand Q are formed from a 123 degree rotation ofU and V respectively, the Q signal can be moreseverely filtered than I (to about 600 KHz, comparedto about 1.3 MHz) without being perceptible to a viewer at typical TVviewing distance. YIQ is equivalent to YUV with a 33degree rotation and an axis flip in the UV plane.

Because an analog NTSC decoder has no way of knowingwhether an encoder was encoding YUV or YIQ, the decodercannot detect whether the encoder was running at 0 degree or 33 degreephase. Thus, in analog usage the terms YUV and YIQ areoften used somewhat interchangeably. YIQ was important in the early daysof NTSC, but most broadcasting equipment now encodesequiband U and V.

YP: Yellow Pages; Naming service (SUN),(see also NIS, BIND)

YUV: Convenient shorthand commonly - but incorrectly- used to describe the analog luminance and color difference signals incomponent video systems. Y is correct for luminance butU and V are, in fact, the two subcarrier modulation axes used in the PALcolor coding system. Scaled and filtered versions of the B-Yand R-Y color difference signals are used to modulatethe PAL subcarrier in the U and V axes respectively.The confusion arises because U and V are associated with the color differencesignals but clearly they are not the same thing.




Last Update:12/13/03
Prototype InfoBase Technology