Ericsson RX1290 Guia do Utilizador descarregar pdf (Página 81)

Glossary

Reference Guide: RX1290 H.264 Contribution Receiver Page A-3

ST.RE.E10228.1

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 not susceptible to fading.

CCIR See: ITU-R.

CCITT See: ITU-T.

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 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

(digital) or P

(analogue), are used to convey colour information. When

)

is added to the luminance

(Y), the complete picture information is conveyed as

(YP

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 System Responsible for compressing and multiplexing the video / audio / data bit-streams, together

with the authorisation 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

600 . 0 dBmV is 1 mV terminated in 75 .

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