Transport Streams are the combining (multiplexing) of multiple
program channels (typically digital video channels) onto a
signal communication channel (such as a satellite transponder
channel). A MPEG transport stream (MPEG-TS) is also called a
multi-program transport stream (MPTS). MPEG transport streams
(MPEG-TS) use a fixed length packet size and a packet identifier
identifies each transport packet within the transport stream. A
packet identifier in an MPEG system identifies the packetized
elementary streams (PES) of a program channel. A program (such
as a television show) is usually composed of multiple PES
channels (e.g. video and audio). Because MPEG-TS carry multiple
programs, to identify the programs carried on a MPEG-TS, a
program allocation table and program mapping table is
periodically transmitted which provides a list of the programs
contained within the MPEG-TS. These program tables provide a
list of programs and their associated PIDs for specific programs
which allows the MPEG receiver/decoder