TANDBERG E5780, Справочное руководство

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Glossary
Page A-8 Reference Guide: evolution 5000 E5780 and E5782 Encoder
ST.RE.E10135.4
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.
PIN
Personal Identification Number: A password used to control access to programming and to set purchase limits.
Each subscriber household can activate several PINs and may use them to set individual parental rating or
spending limits for each family member.
Pixel PIX (picture) El ement: The digital representation of the smallest area of a television picture capable of being
delineated by the bitstream. See Pel for more information.
pk-pk peak to peak: Measurement of a signal or waveform from its most negative point 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 sine 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 mandatory for MPEG-2
compliance. Each service has a PMT, which lists the component parts (elementary streams of 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 and is the number of times the event occurs for every 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 stream, the timebase is
defined by the PCR. The use of the PCR for timing information creates a virtual channel within the stream.
Programme A linking of one or more events under the control of a broadcaster. For example, football match, news, film show.
In the MPEG-2 concept, the collection of elementary streams comprising the programme, have a common start
and end time. A series of programmes are referred to as events.
P
R
P
B
Analogue Colour difference signals. Refer to C
R
C
B
for an explanation.
PROM
Programmable Read-Only Memory: A device, which may be written once with data for permanent storage, and
then read whenever required. Special types of PROM permit the erasure of all data by Ultraviolet light (EPROM) or
by application of an electronic signal (EEPROM).
PS Program Stream: A combination of one or more PESs with a common timebase.