
1-10
Introduction
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
tion purposes, and a system clock value. The system header packet con-
tains a variety of housekeeping data and in particular contains a system
stream ID used to differentiate multiple system streams. A sequence of
one or more packets contains either encoded audio or encoded video
stream data. The ISO 11172 end code is the nal element in an MPEG
pack. For detailed denition of pack headers, refer to the ISO CD
11172-1 system stream descriptions.
Any one MPEG packet carries either audio or video data, but not both
simultaneously. An MPEG Audio Packet contains an audio packet header
and one or more Audio Frames.
Figure 1.6 shows the packet structure.
Figure 1.6
MPEG Audio
Packet Structure
1.2.1.1 Audio Packet Header
An audio packet header contains the following:
Packet Start Code
Identies this as an audio packet. The Packet Start Code also con-
tains a ve-bit audio stream identier that may be read by the user
to identify the audio channel.
Packet Length
Indicates the number of bytes remaining in the audio packet.
Presentation Time Stamps (PTS)
The PTS indicates when audio data should be presented.
1.2.1.2 Audio Frame
An Audio Frame contains a slice of the audio data stream together with
some supplementary data. Audio frames have the following elements:
Packet
Audio
Header
Audio Packet
Contains:
Packet Start Code
. . .
Packet Length
Presentation Time Stamps
Audio
Frame
Audio
Frame
Audio Packet
Contains:
Audio Frame Header
Audio Frame CRC
Audio Data
Ancillary/User Data
(rst)
(last)
Audio Frames
(quantity varies)
. . .