I & Q (quadrature)

[ppppenguin]

For the co;our TV types around here I and Q are indelibly associated with the NTSC colour system. The I and Q axes were indeed at 90 degrees to each other but rotated by some odd amount (33 degrees?) to the reference U and V axes. The idea was to squeeze every last drop out of the spectrum and the properties of human vision by having one colour compon ent narrower bandwidth than the other. In practice few encoders or decoders ever did this. I think the Cox 203 NTSC coder did do it the right way but most others simply enscoded narrow bandwidth on the U and V axes. Or for swithcable PAL/NTSC coders often wideband on both axes.