
8-24
System Stream Decoding and Synchronization
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
previous entries, as it is impossible for any of these entries to apply to
future pictures.
Figure 8.12 shows the concept of extracting the expected
PTS value for the current decoded picture.
Figure 8.12
PTS Association
with Presentation
Unit
Once the PTS from the table has been identied and the AUX FIFO
Ready Interrupt occurs, the host processor must read the L64005 Auxil-
iary data FIFO to determine the type of picture that is currently in the
decode process. After fetching the proper PTS and determining the pic-
ture type, the host processor must execute the picture type procedure,
as follows. Each time the PTS is fetched from the PTS list, the picture
type procedure validates the current PTS if the frame is a B type, or
stores the current PTS in the Anchor PTS buffer for the future reference
(when the next Anchor frame is reconstructed) for P or I frames. At the
same time, the host processor should obtain the previous Anchor PTS
stored in the Anchor PTS buffer and validate it if it is available.
PTSn
Write Pointer n
PTSn+1
Write Pointer n+1
PTSn+2
Write Pointer n+2
PTSn+3
Write Pointer n+3
PTSn+m
Write Pointer n+m
The Video PTS List
READ (ReadPointer)
Compare
Write Pointer<= ReadPointer
Fetch PTS
from
Table
START
Picture Start Code Reg.
Group 7, Index 42, 43, 44
SUBTRACT
48 from
ReadPointer value
GOTO Picture Type Routine
Search For Expected
.
Video PTS Routine