TANDBERG E5780, Справочное руководство

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Glossary
Reference Guide: evolution 5000 E5780 and E5782 Encoder Page A-3
ST.RE.E10135.4
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 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 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.
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 authorisation
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.
CVCT
Cable Virtual Channel Table (ATSC).
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 600
Ω . 0 dBmV is 1 mV terminated in 75 Ω .
DCE Data Communications Equipment: Typically a modem. It establishes, maintains and terminates a session on a
network but in itself is not the source (originator) or destination (end receiving unit) of signals (e.g. a computer, see
DTE). A DCE device may also convert signals to comply with the transmission path (network) format.
DCT
Discrete Cosine Transform: A technique for expressing a waveform as a weighted sum of cosines. Raw video
data is not readily compressible. DCT is not in itself a compression technique but is used to process the video data
so that it is compressible by an encoder. DCT processes the picture on an 8x8-pixel block basis, converting the
data from an uncompressible X Y form (as displayed by an oscilloscope) to a compressible frequency domain form
(as displayed by a spectrum analyser). Can be forward DCT or inverse DCT.
DDS Direct Digital Synthesiser.
De-blocking Filter An in-loop deblocking filter is designed to smooth out artefacts introduced by the compression process in the
reconstructed image in both the encoder and decoder. Then the motion estimation and compensation should
produce better quality for the same bitrate.
Decoder The unit containing the electronic circuitry necessary to decode encrypted signals. Some Decoders are separate
from the receiver but in satellite TV broadcasting, the term is often used interchangeably as a name for an
Integrated Receiver Decoder (IRD). The term IRD, or IRD / Decoder, is usually associated with satellite TV
broadcasting while Cable systems are based on Converters or on Set-Top Boxes / Converters.
Decoding Time stamp A field that may be present in a PES packet header that indicates the time that an access unit is to be decoded in
the system target Decoder.
DID Data Identifier for embedded audio within the HD-SDI signal .
Differential Coding Method of coding using the difference between the value of a sample and a predicted value.
DIL Dual In Line: The most common type of package for small and medium scale integrated circuits. The pins hang
vertically from the two long sides of the rectangular package, spaced at intervals of 0.1 inch.
DIN Deutsches Institut für Normung: German Standards Institute.
Dolby Digital Formerly AC-3 . An audio coding system based on transform coding techniques and psychoacoustic principles.
Downlink The part of the satellite communications circuit that extends from the satellite to an Earth station.