Ericsson AVP 4000, Справочное руководство, Страница: 350 / 422

Glossary
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Channel a narrow range of frequencies, part of a frequency band, for the
transmission of radio and television signals without interference from
other channels.
In the case of OFDM, a large number of carriers spaced apart at
precise frequencies are allocated to a channel.
Channel Coding
A way of encoding data in a communications channel that adds
patterns of redundancy into the transmission path in order to
improve the error rate. Such methods are widely used in wireless
communications.
Chrominance The color part of a TV picture signal, relating to the hue and
saturation but not to the luminance (brightness) of the signal. In a
composite-coded color system, the color information (chrominance,
often referred to as chroma) is modulated onto a high frequency
carrier and added to the monochrome-format video signal carrying
the luminance (Y). In a component-coded color system, the two
color-difference signals (R-Y)(B-Y) usually referred to as C
R
C
B
(digital) or P
R
P
B
(analogue), are used to convey color information.
When C
R
C
B
(P
R
P
B
) is added to the luminance (Y), the complete
picture information is conveyed as YC
R
C
B
(YP
R
P
B
).
Closed Captioning A TV picture subtitling system used with 525-line analogue
transmissions.
CODE Create Once Distribute Everywhere.
Codec The combination of an En co der and a complementary Dec oder
located respectively at the input and output of a transmission path.
COFDM Coded OFDM: COFDM adds forward error correction to the OFDM
transmission consisting of Reed-Solomon (RS) coding followed by
convolutional coding to add extra bits to the transmitted signal. This
allows a large number of errors at the receive end to be corrected by
convolutional (Viterbi) decoding followed by RS decoding.
Composite
CVBS Video Signal, 1 V
pk-pk
Compression Reduction in the number of bits used to represent the same
information. For the purposes of a broadcast system, it is the
process of reducing digital picture information by discarding
redundant portions of information that are not required when
reconstituting the picture to produce viewing clarity. Compression
allows a higher bite-rate to be transmitted through a given
bandwidth.
Compression
System
Responsible for compressing and multiplexing the video / audio /
data bitstreams, together with the authorization stream. The
multiplexed data stream is then ready for transmission.
C
R
C
B
Digital Color difference signals. These signals, in combination with
the luminance signal (Y), define the color and brightness of each
picture element (pixel) on a TV line. See: Chrominance
CRC Cyclic Redundancy Check: A mathematical algorithm that computes
a numerical value based on the bits in a block of data. This number
is transmitted with the data and the receiver uses this information
and the same algorithm to ensure the accurate delivery of data by
comparing the results of algorithm and the number received. If a
mismatch occurs, an error in transmission is presumed.