DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

CIE luminance, CIE Y See Luminance. The qualifier CIE is sometimes used to emphasize
that the associated quantity is representative of tristimulus (linearlight)
value proportional to intensity, as opposed to a nonlinear,
gamma-corrected quantity.
CIF, common image format 1. The elusive goal of a single (common) worldwide standard pixel
array for digital video, perhaps at different frame rates. Distinguished
from CDR. Confusingly, the acronym collides with CIF,
common intermediate format (see below).
CIF, common intermediate
format
2. In MPEG-2 or other video compression systems excepting
those for videoconferencing, an image format of either 720×480
or 720×576. The term is an oxymoron, since there is not a single
(“common”) format, but two different formats. (In the deliberations
that led to digital SDTV studio standards, agreement upon
a common image format was not reached!)
In ITU-T Rec. H.261, a progressive 352×288 image format with
4:2:0 chroma subsampling and a frame rate of 29.97 Hz. CIF
image data is ordinarily subsampled from SDTV. The format is
a compromise derived from the image structure of 576i25 and
the frame rate of 480i29.97. Distinguished from CIF, common
image format, above. See also QCIF, on page 642.
Clamp (v.) 1. Imposition of a DC offset onto a signal, so as to place a certain
waveform feature (such as back porch) at a specific level (such as
blanking level).
2. Loosely, Clip; see below.
Clean aperture The specified or standardized rectangular portion of the pixel
array that remains subjectively free from intrusion of artifacts
resulting from filtering of the picture edges.
Clip (v.) Forcing a signal to a certain maximum (or minimum) level, so as
to avoid excursion above (or below) that level.
Closed caption (CC) Digital data conveying textual information that can be decoded
and displayed for the benefit of hearing-impaired viewers. In 480i
NTSC analog video, closed caption data is inserted into line 21.
(Unlike other vertical interval signals, NTSC line 21 is classified as
active picture video.)
CLV Constant linear velocity: A method of recording on optical disc
where rotational speed is varied as a function of head actuator
position so as to keep media speed constant with respect to the
head. Contrasted with CAV (constant angular velocity).
CM In DV compression, a coded (compressed) macroblock.
CN/PAL “Combination” N/PAL, used in Argentina, Paraguay, and Uruguay.
ITU-R defines System N as having 10:4 picture:sync ratio and
7.5% setup. However, these countries broadcast 7:3 picture:sync
ratio and zero setup, so their system is described by ITU-R as a
618 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES