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.
P
R
P
B
Analogue Color difference signals. Refer to C
R
C
B
for an explanation.
PS
Program Stream: A combination of one or more PESs with a
common timebase.
PSI
Program Specific Information: Consists of normative data, which is
necessary for the de-multiplexing of transport streams and the
successful regeneration of programs (see also: SI).
PSIP
Program System Information Protocol: The ATSC equivalent of SI
for DVB.
PSK
Phase Shift Keying: A method of modulating digital signals
particularly suited to satellite transmission.
PSR Professional Satellite Receiver: See also: IRD.
PSU
Power Supply Unit.
QAM
Quadrature Amplitude Modulation: A method of modulating digital
signals, which uses combined techniques of phase modulation and
amplitude modulation. It is particularly suited to cable networks.
QoS
Quality of Service. A common term for a set of parameters
describing the quality you get from an IP network: Throughput,
availability, delay, jitter and packet loss.
QPSK
Quadrature Phase Shift Keying: A form of phase shift keying
modulation using four states.
QSIF
Quarter Screen Image Format.
Quantise
A process of converting analogue waveforms to digital information.
8-bit quantization as set out in ITU-R Rec. 601. Uses 256 levels in
the range 0 – 255 to determine the analogue waveform value at any
given point. The value is then converted to a digital number for
processing in the digital domain.
To Next Page
Loading...
