DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Contrast 1. Contrast ratio; see below.
the other two components. All standard video systems, including
NTSC, PAL, Y’C B C R , and HDTV, approximate constant luminance
operation. However, because luma is computed as a weighted
sum of gamma-corrected primary components, a certain amount
of true luminance “leaks” into the color difference components
and induces second-order artifacts.
2. The luminance of subjectively correct midscale image information,
compared to its reproduced luminance.
3. User-accessible means to adjust video gain. Preferably called
video gain; sometimes called picture.
Contrast ratio The ratio between specified light and dark luminances.
Corner frequency The frequency at which the output power of a lowpass or highpass
filter or subsystem has fallen to half its value at a reference
frequency, typically DC. (For a digital or constant-impedance
system, this is equivalent to the frequency at which the output
magnitude has been attenuated 3 dB.)
Cosited Chroma subsampling in which each subsampled chroma sample is
located at the same horizontal position as a luma sample.
Rec. 601, Rec. 709, and MPEG-2 standards specify cosited chroma
subsampling. (MPEG-2, 4:2:0 chroma subsampling places chroma
samples interstitially in the vertical domain.)
CRC Cyclic redundancy check (code). Information inserted prior to
recording or transmission that allows playback or receiver equipment
to determine whether errors were introduced. A CRC with
a small number of bits provides error-detection capability; a CRC
with a large number of bits provides error-correction capability.
CRC codes involve multiplying and dividing polynomials whose
coefficients are restricted to the set {0, 1}. Similar capability can
be achieved using codes based upon mathematical principles
other than CRC; see ECC.
Cross-color An artifact of composite video encoding and/or decoding that
involves the erroneous interpretation of luma information as color.
The cross-color artifact appears frequently when luma information
having a frequency near that of the color subcarrier appears
as a swirling color rainbow pattern.
Cross-luma An artifact of composite video encoding and/or decoding that
involves the erroneous interpretation of color information as
luma. Cross-luma frequently appears as dot crawl or hanging dots.
CTDM Chroma time-division multiplexed: A system of recording component
video, used in Betacam, whereby P B, and P R components are
each time-compressed then combined in one recording channel.
Cutoff frequency See Corner frequency, on page 622.
622 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES