TANDBERG EN8000, Справочное руководство

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Glossary
Page A-10 Reference Guide: EN8000 MPEG-4 Part 10 (H.264/AVC) Encoders
ST.RE.E10233.1
nm Nanometre: a unit of length equal to one thousand millionth (10
-9
) of a metre.
NTSC National Television Systems Committee: The group, which developed analogue standards
used in television broadcast systems in the United States. Also adopted in other countries
(e.g. Mexico, Canada, Japan). This system uses 525 picture lines and a 59.97 Hz field
frequency.
NVOD Near Video On Demand: Method of offering multiple showings of movies or events. The
showings are timed to start at set intervals, determined by the broadcaster. Each showing of a
movie or event can be sold to subscribers separately.
NVRAM Non-volatile Random Access Memory: Memory devices (permitting random read / write
access) that do not lose their information when power is removed. Stores the default
configuration parameters set by the user.
OFDM Orthogonal FDM: A modulation technique used for digital TV transmission in Europe, Japan
and Australia; more spectrally efficient than FDM. In OFDM, data is distributed over a large
number of carriers spaced apart at precise frequencies. The carriers are arranged with
overlapping sidebands in such a way that the signals can be received without adjacent
channel interference.
OID Object Identifier is the part of the SNMP message that defines which module should receive
the command.
OPPV Order ahead Pay Per View: An advance purchase of encrypted one-time events with an
expiry date.
OSD On-screen display: Messages and graphics, typically originating from the SMS, and
displayed on the subscriber’s TV screen by the IRD, to inform the subscriber of problems or
instruct the subscriber to contact the SMS.
Packet A unit of data transmitted over a packet-switching network. A packet consists of a header
followed by a number of contiguous bytes from an elementary data stream.
PAL Phase Alternating Line: A colour TV broadcasting system where the phase of the R-Y
colour-difference signal is inverted on every alternate line to average out errors providing
consistent colour reproduction.
PAT Program Association Table: Part of the MPEG-2 Program Specific Information (PSI) data
and is mandatory for MPEG-2 compliance. The PAT points (maps) to the PMT.
PCM Pulse Code Modulation: A process in which a signal is sampled, each sample is quantised
independently of other samples, and the resulting succession of quantised values is encoded
into a digital signal.
PCR Program Clock Reference: A time-stamp in the transport stream from which the Decoder
timing is derived.
PDC Programme Delivery Control (VBI): A Teletext service allowing simple programming (i.e.
VideoPlus) of VCR recording times. If the desired program is rescheduled, PDC updates the
programming information in the VCR.
Pel Picture Element: Also known as a pixel. The smallest resolvable rectangular area of an
image either on a screen or stored in memory. On screen, pixels are made up of one or more
dots of colour. Monochrome and grey-scale systems use one dot per pixel. For grey-scale,
the pixel is energised with different intensities, creating a range from dark to light (a scale of
0-255 for an eight-bit pixel). Colour systems use a red, green and blue dot per pixel, each of
which is energised to different intensities, creating a range of colours perceived as the mixture
of these dots. If all three dots are dark, the result is black. If all three dots are bright, the result
is white.
PES Packetised Elementary Stream: A sequential stream of data bytes that has been converted
from original elementary streams of audio and video access units and transported as packets.
Each PES packet consists of a header and a payload of variable length and subject to a
maximum of 64 Kbytes. A time-stamp is provided by the MPEG-2 systems layer to ensure
correct synchronisation between related elementary streams at the Decoder.
PID Packet Identifier: The header on a packet in an elementary data stream, which identifies that
data stream. An MPEG-2 / DVB standard.