TANDBERG SM6610, Справочное руководство

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Glossary
Reference Guide: SM6610, SM6615, SM6620 and SM6625 Satellite Modulators Page A-5
ST.RE.E10152.2
IF
Intermediate Frequency: Usually refers to the 70 MHz or 140 MHz output of the Modulator in cable, satellite and
terrestrial transmission applications.
Interframe Coding Compression coding involving consecutive frames. When consecutive frames are compared, temporal redundancy
is used to remove common elements (information) and arrive at difference information. MPEG-2 uses B and P
frames, but since they are individually incomplete and relate to other adjacent frames, they cannot be edited
independently.
Intraframe Coding Compression coding involving a single frame. Redundant information is removed on a per frame basis. All other
frames are ignored. Coding of a macroblock or picture that uses information only from that macroblock or picture.
Exploits spatial redundancy by using DCT to produce I frames; these are independent frames and can be edited.
IP Internet Protocol: The IP part of TCP/IP. IP implements the network layer (layer 3) of the protocol, which contains
a network address and is used to route a message to a different network or sub-network. IP accepts packets from
the layer 4 transport protocol (TCP or UDP), adds its own header to it and delivers a datagram to the layer 2 data
link protocol. It may also break the packet into fragments to support the Maximum Transmission / Transfer Unit
(MTU) of the network.
I-picture; I-frame Intracoded Picture/Frame: A picture / frame, which is coded using purely intracoding with reference to no other
field or frame information. The I frame is used as a reference for other compression methods.
IPPV Impulse Pay Per View: One-time events, purchased at home (on impulse) using a prearranged SMS credit line.
IRD Integrated Receiver Decoder: The Receiver with an internal MPEG Decoder, which is connected to the
subscriber’s TV. The IRD is responsible for receiving and de-multiplexing all signals. The unit receives the
incoming signal and if CA is active, decodes the signal when provided with a control word by the viewing card.
Domestic IRDs are also known as Set-Top Units or Set-Top Boxes.
IRE Institute of Radio Engineers: No longer in existence but the name lives on as a unit of video amplitude
measurement. This unit is 1% of the range between blanking a peak white for a standard amplitude signal.
ISDN Integrated Services Digital Network: The basic ISDN service is BRI (Basic Rate Interface), which is made up of
two 64 kbit/s B channels and one 16 kbit/s D channel (2B+D). If both channels are combined into one, called
bonding , the total data rate becomes 128 kbit/s and is four and a half times the bandwidth of a V.34 modem
(28.8 kbit/s).
The ISDN high-speed service is PRI (Primary Rate Interface). It provides 23 B channels and one 64 kbit/s D
channel (23B+D), which is equivalent to the 24 channels of a T1 line. When several channels are bonded together,
high data rates can be achieved. For example, it is common to bond six channels for quality videoconferencing at
384 kbit/s. In Europe, PRI includes 30 B channels and one D channel, equivalent to an E1 line.
ISO International Standards Organisation.
ISOG Inter-union Satellite Operations Group.
ITS Insertion Test Signal: A suite of analogue test signals placed on lines in the VBI. Also known as VITS.
ITT Invitation To Tender.
ITU-R International Telecommunications Union - Radiocommunications Study Groups (was CCIR).
ITU-T International Telecommunications Union - Telecommunications Standardisation Sector (was CCITT).
JPEG Joint Photographic Experts Group: ISO/ITU standard for compressing still images. It has a high compression
capability. Using discrete cosine transform, it provides user specified compression ratios up to around 100:1 (there
is a trade-off between image quality and file size).
kbit/s 1000 bits per second.
Kbit 1024 bits, usually refers to memory capacity or allocation.
Ku-band
The portion of the electromagnetic spectrum, which spans the frequency range of approximately 12 GHz to
14 GHz. Used by communications satellites. Preferred for DTH applications because this range of frequency is
less susceptible to interference.
LAN Local Area Network: A network, which provides facilities for communications within a defined building or group of
buildings in close proximity.
L-band The frequency band from 950 MHz to 2150 MHz, which is the normal input-frequency-range of a domestic IRD.
The incoming signal from the satellite is down-converted to L-band by the LNB.
LED Light Emitting Diode.
LNB Low Noise Block Down-Converter: The component of a subscriber satellite transmission receiving dish which
amplifies the incoming signal and down-converts it to a suitable frequency to input to the IRD (typically 950 MHz -
1600 MHz).
LO Local Oscillator.
LSB Least significant bit.
Luminance The television signal representing brightness, or the amount of light at any point in a picture. The Y in YC
R
C
B.