L64005 MPEG-2 Audio/Video Decoder Technical Manual
8-21
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
Figure 8.9
Buffer Organization
In L64005 Memory
For the external host processor to create the audio and video PTSs list,
it needs to assign start and end pointers to all the PES headers buffers,
start the channel, start the decoding process, and enable the interrupt
that indicates a PES header has arrived at the PES header buffer.
Once an interrupt for packet start code has been generated, the L64005
writes a complete PES header into the video or audio PES header buffer
(depending upon the stream ID eld) in the PES mode, or into the audio
PES header buffer in system mode. At the end of the header, the L64005
writes the current write pointer value of either the video or the audio
channel buffers. This information allows the external host processor to
associate the transmitted PTSs with the video start code or audio sync
code time of the access unit. The write pointer value is the start position
of the current coded data in the channel buffer. The presentation time is
determined when the access unit is decoded. The presentation time can
then be associated with the PTS.
Figure 8.10 shows the PES packet header structure. The structure of
PES packet header can be used to determine how the host processor
fetches the PTS data from the header and subsequently generates the
Pre-Parser
Video PES
Header Q
Audio PES
Header Q
Video
Channel Q
Audio
Channel Q
Start Address
End Address
Start Address
End Address
Channel
Interface
External Buffer
Interface
L64005