Triple-Play Service Deployment

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MPEG Video
Syntax
MPEG-2
System
Syntax
Header
Image
Structure
Payload
(Variable Length)
Header Fixed Length Stuffing
Useful
Data
(188 bytes)
Chapter 6: Troubleshooting Video in the Headend
Video Elementary Stream
Packetized Elementary Stream
Transport Stream
Figure 6.4 The MPEG-2 System is comprised of three layers; the Elementary Stream, the
Packetized Elementary Stream consisting of large, variable length packets, and the MPEG-2
Transport Stream, composed of uniform 188 byte packets.
The transport stream can hold one or more programs, either as an
MPEG-2 Single Program Transport Stream (SPTS) or MPEG-2 Multi-
Program Transport Stream (MPTS). The main differences are the
number of PIDs in the stream, the transport stream bit rate, and
the volume of metadata needed to index the program(s) in the
transport stream. In all cases, the bulk of the MPEG-2 transport
stream are video PIDs, followed by audio PIDs, and possibly Null
PIDs used to fill unused space and achieve a specified transport
stream bit rate. But the most important data in the transport
stream is the index the decoder must use to identify the PIDs in
that stream. Without it the video and audio components will be
unrecognizable. This information is contained in the Program
Association Table (PAT) and Program Map Table (PMT). The PAT is
always located on PID 0x0000 and lists the programs being carried
in that MPEG-2 transport stream and the PID number of the PMT
for each program. The PMT, in turn, lists the PID numbers for the
audio and video components as well as any additional program
components in the stream, such as secondary audio, metadata, etc.
Assigning PIDs and the subsequent logging in the PAT and PMT