Glossary
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.
ODU
Outdoor Unit
OFDM
Orthogonal Frequency Division Multiplex: 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.
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 color TV broadcasting system where the
phase of the R-Y color-difference signal is inverted on every
alternate line to average out errors providing consistent color
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 quantized independently of other samples, and the
resulting succession of quantized 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
Program Delivery Control: 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.
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