Glossary
Page A-2
Instruction Manual: Professional Decoder
ST.TM.TT1220.1
Baud Rate
This is typically used to denote the bit rate of the payload plus channel coding overhead. In a binary transmission (
low and hi only) the baud rate is equivivalent to the highest possible transition frequency (hi-low-hi-low) in the
transmission.. Measured in Baud.
BCC
Broadcast Control Computer.
BER
Bit Error Rate: A measure of transmission quality. It is generally shown as a negative exponent, (e.g., 10
-7
which
means 1 out of 10
7
bits are in error or 1 out of 10,000,000 bits are in error).
Also:
Bit Error Ratio: The ratio of error bits to total error bits in a transport stream.
Bit-Rate
In a binary transmission ( low and hi only) the bit rate is equivivalent to the highest possible transition frequency (hi-
low-hi-low) in the transmission. This does not necessarely specify the bit rate of the payload. See baud rate.
Block; Pixel Block
An 8 row by 8 column matrix of luminance sample values, or 64 DCT coefficients (source, quantised, or dequantised).
Bouquet
A collection of services (TV, radio, and data, or any combination of the three) grouped and sold together, and
identified in the SI as a group. A single service may be in several bouquets.
B-Picture; B-Frame
(Bidirectionally Predictive
Coded Picture/Frame)
A picture that is coded using motion-compensated prediction from previous I or P frames (forward prediction) and/or
future I or P frames (backwards prediction). B frames are not used in any prediction.
BPSK (Binary Phase Shift
Keying)
A data modulation technique.
Buffer
A memory store used to provide a consistent rate of data flow.
BW
Bandwidth.
CA (Conditional Access)
The technology used to control the access to viewing services to authorised subscribers through the transmission of
encrypted signals and the programmable regulation of their decryption by a system such as viewing cards.
CAT (Conditional Access
Table)
Part of the Service Information data. The CAT identifies the PID in which conditional access management data
(EMMs) is being carried, per CA provider.
C-Band
The portion of the electromagnetic spectrum which spans the frequency range of approximately 4 GHz to 6 GHz.
Used by communications satellites. Preferred in tropical climates because it is less susceptible to fading compared to
e.g. Ku band transmissions
CCIR
See: ITU-R.
CCITT
See: ITU-T.
Channel
A particular bandwidth on which an individual viewing service is broadcast.
Channel Coding
A form of coding for the conversion of a digital signal into a signal that is matched to the characteristics of the
transmission channel.
Closed Captioning
A TV picture subtitling system used with 525-line analogue transmissions.
Codec
The combination of a coder followed by a complementary decoder located respectively at the input and output of a
transmission path.
COFDM (Coded Orthogonal
Frequency Division
Multiplex)
A modulation system used particularly for terrestrial digital broadcasting.
Compression
Reduction in the number of bits used to represent an item of data. For the purposes of a broadcast system, it is the
process of reducing digital information by discarding redundant portions of information that are not required upon
reconstitution to produce viewing clarity.
Compression System
Responsible for compressing and multiplexing the video/audio/data bit-streams, together with the authorisation
stream. The multiplexed data stream is then transmitted to the satellite or cable head-end.
Cr/Cb
Chrominance difference signals. These signals, in combination with the luminance signal (Y), define the colour of a
particular point on a TV line.
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 insure 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 (Composite Video
Blanking and
Synchronisation)
Analogue TV signals, e.g. PAL, NTSC.
