DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

4. User-accessible means to adjust Hue (3).
I-field In MPEG, a field-coded I-picture. I-fields come in pairs, either top
then bottom, or bottom then top. See I-picture, below.
I-frame In MPEG, either (i) a frame-coded I-picture, or (ii) a field-coded
I-picture [either top or bottom], followed by a field-coded
I-picture or P-picture [of opposite parity]. In the second case, the
two fields form what is sometimes called an IP-frame; the P-field
may involve prediction from the I-field. See I-picture, below.
I/PAL See PAL-I, on page 640.
I-picture In MPEG, an intraframe picture (field, or frame): A picture, or
coded picture information, that makes no reference to preceding
or following pictures. An I-picture is coded independently; it
makes no use of temporal coherence.
I, Q In-phase and Quadrature color difference components of NTSC: U
and V components rotated +33° and then axis-exchanged. NTSCmodulated
chroma was originally based on I and Q color differences,
where I had considerably more bandwidth than Q. Nowadays,
NTSC color modulation is usually performed on equiband U
and V components. Except perhaps for bandwidth difference, it is
impossible to tell from a composite analog NTSC signal whether it
was encoded along [U, V], [I, Q], or any other pair of axes.
Intensity Intensity is a measure over some interval of the electromagnetic
spectrum of power (usually radiated from, or incident on,
a surface), in a specified direction. Intensity is a linear-light
measure, expressed in physical units such as watts per steradian
(W·sr -1 ). The intensity produced by a CRT monitor is not proportional
to the applied voltage, but proportional to approximately
the 5 ⁄2-power of applied voltage. Image scientists and video engineers
are usually interested in intensity per unit area, weighted by
the visual response – that is, they are usually interested not in
intensity per se but in luminance or tristimulus values.
Interlace A scanning standard in which alternate raster lines of a frame are
displaced vertically by half the scan-line pitch and displaced
temporally by half the frame time to form a first field and a second
field. Examples are 480i29.97 (525/59.94), 576i25 (625/50), and
1080i30 (1125/60). Systems with high-order interlace have been
proposed but none has been deployed, so modern usage of the
term interlace implies 2:1 interlace. See also Field, on page 628.
Interlace factor The ratio between the number of picture lines in a reference
progressive system and the number of picture lines necessary to
defeat twitter in an interlaced system having equivalent spatial
resolution. Distinguished from, but often mistakenly described as,
Kell factor, k.
Interpolation Resampling that produces more output samples than original
samples (synonymous with upsampling), or that produces the
same number of output samples as input samples (phase shifting).
632 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES