L64005 MPEG-2 Audio/Video Decoder Technical Manual
4-5
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
symbols is performed byte-wise parallel. Therefore, the L64005 requires
that parallel bitstream data be byte-aligned with respect to system start-
codes. The L64005 does not write packet stufng data to the channel
buffer.
4.2.1.2 Mis-Synchronization
The L64005 may initially synchronize incorrectly to a bitstream when
emulation of resync codes in the audio data eld occurs. The probability
of this incorrect synchronization occurring is very low, and is a function
of the MPEG syntax, not a fault in the design of the L64005. However,
the L64005 can detect this condition and will try to resync to the next
start code.
4.2.1.3 Synchronization in the Video Elementary Stream
The L64005 parses the elementary video data stream to decode the
MPEG video. In serial mode, the L64005 synchronizes to the bitstream
independently of the alignment or error condition of the data from the
system synchronizer. In parallel mode, the data is assumed to be byte
aligned with respect to start codes. The only constraint is that the data
should be either MPEG-1 or MPEG-2 video data.
4.2.1.4 Synchronization in the Audio Elementary Stream
The L64005 parses the audio elementary stream to decode the MPEG
audio. The audio decoder synchronizes to the audio bitstream indepen-
dently of the alignment of the data or error condition in the channel.
4.2.1.5 Transport Mode Operation
If the L64005 is programmed to operate in transport mode, the L64005
is expected to receive a series of Audio and Video Packets. The Audio
Packet data is strobed into the L64005 using the AVALID signal, and the
Video Packet data is strobed into the L64005 using the VVALID signal.
The Pre-Parser separates the Audio PES Header information and the
Video PES Header information and then stores the header information it
in the corresponding Audio and Video PES Header Buffers. The elemen-
tary Audio and Video data is stored in the data channel. The system con-
troller can read the PES header buffers to extract the header information.
The preparser checks syntax when it expects start codes and resyncs to
the bitstream if necessary.