
8-2
System Stream Decoding and Synchronization
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
Table 8.1
Levels of Hierarchy
in MPEG-1 and
MPEG-2 System
Syntax
MPEG-2 introduces the Packetized Elementary Stream (PES) to allow
multiple programs to be sent over the same transport. An MPEG-2 sys-
tem may transmit either a Program Stream that contains PES for a single
program, or a Transport Stream that contains PES for multiple, possibly
unrelated, programs. An MPEG-2 system decoder therefore must be able
to accept PES data from the Transport Stream or from the Program
Stream. The crucial difference between these two scenarios is that the
data in the Transport Stream may split PES packets at non-packet
boundaries, whereas the data in the Program Stream only switches from
one PES packet to another at packet boundaries.
The L64005 parses MPEG-1 system data the same way that it parses
MPEG-2 system data, using a system parser between the incoming sys-
tem data and the elementary stream buffers.
Refer to the
ISO/IEC 13818 specication for a complete description of
MPEG-2 syntax.
8.1.1
Parsing a
Program Stream
Parsing a program stream is the simple case because the L64005 parses
only one PES packet at a time. It is also very similar for both the MPEG-
1 and the MPEG-2 cases.
8.1.1.1 Parsing an MPEG-1 System Stream
System data is presented to the decoder over the serial or parallel chan-
nel interface. When the decoder encounters any System Start Code, it
causes the decoder to synchronize to it, if it is not already in sync. The
decoder then moves the data into the system channel buffer including the
system and packet headers.
In the case of Packet Start Codes, the parser checks whether the packet
contains audio or video data, and whether the Stream Select eld
MPEG-1 System Streams
MPEG-2 System Streams
Program Stream
Transport Stream or Program Stream
Elementary Stream
Packetized Elementary Stream (PES)
Elementary Stream