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

 

CRCB (digital) or PRPB (analogue), are used to convey colour

 

information. When CRCB (PRPB) is added to the luminance (Y), the

 

complete picture information is conveyed as YCRCB (YPRPB).

Closed Captioning

A TV picture subtitling system used with 525-line analogue

 

transmissions.

CODE

Create Once Distribute Everywhere.

Codec

The combination of an Encoder 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 SystemCRCB

Responsible for compressing and multiplexing the video / audio / data bitstreams, together with the authorization stream. The multiplexed data stream is then ready for transmission.

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.

A-4

EN/LZT 790 0005 R1A