Glossary
Instruction Manual: evolution 5000 E57xx DSNG and DENG Voyager Encoder Page A-7
ST.TM.E10076.3
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 s old 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 t he signals can be received
without adjacent channel interference.
OPPV Order ahead Pay Per View: An advanc e purchase of encrypted one-time events with an expiry date.
OSD On-screen display: Messages and graphics, typically ori ginating 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 contac t the SMS.
Packet A unit of data transmitted over a packet-switching network. A packet consists of a header foll owed 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 colou r 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 si gnal.
PCR Program Clock Reference: A time-stamp i n 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 i nformation in the VCR.
Pel Picture Elem ent: Also known as a pixel. The smallest resolvable rectangular area of an image eithe r on a screen
or stored in memory. On screen, pixels are made up of one or more dots of colour. Monochrom e 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 perc eived as the mixture of these
dots. If all three dots are dark, the result is black. If all three dots are bright, the result i s white.
PES Packetised Elementary Stream: A sequential stream of data bytes that has been converted fro m 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.
PIN Personal Identification Number: A password used to control access to pro gramming and to set purchase limits.
Each subscriber household can activate several PINs and may use them to set individual parental r ating or
spending limits for each family member.
Pixel PIX (picture) Element: The digital representation of the smallest area of a television picture c apable of being
delineated by the bit-stream. See Pel for more information.
pk-pk peak to peak: Measurement of a signal or waveform from its most negative p oint to its most positive point.
PLL Phase-Locked Loop. A phase-locked loop is a control system which controls the rotation of an object by
comparing its rotational position (phase) with another rotating object as in the case of a s ine wave or other
repeating signal. This type of control system can synchronise not only the speed, but also the angular position of
two waveforms that are not derived from the same source.
PMT Program Map Table: Part of the MPEG-2 Program Specific Information (PSI) data and is mandato ry for MPEG-2
compliance. Each service has a PMT, which lists the component parts (elementary streams o f video, audio, etc.)
for the various services being transmitted.
P-picture/P-frame A picture / frame produced using forward prediction. It contains predictions from either previous I frames or
previous P frames. The P frame is used as a reference for future P or B frames.
ppm Parts per million.
PPV Pay Per View: A system of payment for viewing services based on a usage / event basis rather than on on-going
subscription. Subscribers must purchase viewing rights for each PPV event that they wish to view. PPV events
may be purchased as IPPV or OPPV.
Program PC - A sequence of instructions for a computer.
TV - A concept having a precise definition within ISO 13818-1 (MPEG-2). For a transport str eam, the timebase is
defined by the PCR. The use of the PCR for timing information creates a virtual channel wi thin the stream.