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Annex A
Chrominance The colour 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 colour system, the colour 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 colour system,
the two colour-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 colour
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 Enco
der and a complementary Decoder
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 Colour difference signals. These signals, in combination with
the luminance signal (Y), define the colour 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.
CVBS
Colour Video Black Sync Signal
dB Decibels: A ratio of one quantity to another using logarithmic scales
to give results related to human aural or visual perception. dB is a
ratio whereas dBm, for example, is an absolute value, quoted as a
ratio to a fixed point of 0 dBm. 0 dBm is 1 mW at 1 kHz terminated
in 600Ω. 0 dBmV is 1 mV terminated in 75Ω.
EN/LZT 790 0005 R1A
A-4