Table of Contents
Advertisement
Glossary
Pel
PES
PID
PIN
Pixel
pk-pk
PLL
PMT
P-picture/P-frame
ppm
PPV
A-14
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
color. Monochrome and grey-scale systems use one dot per pixel.
For grey-scale, the pixel is energized with different intensities,
creating a range from dark to light (a scale of 0-255 for an eight-bit
pixel). Color systems use a red, green and blue dot per pixel, each
of which is energized to different intensities, creating a range of
colors 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.
Packetized 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.
Packet Identifier: the header on a packet in an elementary data
stream, which identifies that data stream. An MPEG-2 / DVB
standard.
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.
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.
peak to peak: Measurement of a signal or waveform from its most
negative point to its most positive point.
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.
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.
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.
Parts per million.
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.
EN/LZT 790 0005 R7A
Advertisement
Table of Contents
