Annex A

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 synchronization 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) Element: The digital representation of the smallest

 

area of a television picture capable 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 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 synchronize

 

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.

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.

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