Refers to one method of encoding of the color content of a video signal such that all colors could be depicted using a two dimensional diagram, more specifically a color wheel. There are two color signals one (I or In Phase) of which represents oranges and blues and the other (Q or Quadrature) represents greens and purples. (Both together are used to represent other colors.) This choice of colors permits giving the oranges and blues, which the human eye is more sensitive to, more frequency bandwidth (1.3 MHz standard) and thus greater color resolution in NTSC video. The remaining colors had to be limited to about 40 lines of resolution (0.5 MHz sideband width) since one of the sidebands of the modulated color signal is so limited and both the I and Q color components cannot be recovered from just the other sideband. Many TV sets today and all consumer VCR's limit color resolution to a theoretical maximum of 40 lines for all colors due to inexpensive circuitry. When it is not necessary to construct a composite video signal, the color signals U and V representing (approximately) blue-yellow and red-cyan respectively, are usually used instead of I and Q. We believe that all of the descriptions on this page can be understood quite well by persons without tremendously high intelligence quotients. Click here for more on video signal formats.

This definition is in context to Television. See more contextual defintions for I-Q.