2/24/2008 9T6WP
Preliminary Hardware Data Module
BCM7405
06/29/07
Functional Description
Bro a d c o m Co rp o r a ti o n
Document
7405-1HDM00-R
Data Transport Processor Page 1-25
There are three counters in the transport field parser:
•
The packet counter: The packet counter counts all packets that are recorded. The packet count at the time an index
table entry is made is part of the entry.
•
The record timer: The record timer keeps a running count of time since the record session started. The value of the
record timer at the time an index table entry is made is part of the entry.
•
The idle timer: The idle timer counts the time between recorded packets. If the time exceeds a programmable timeout
value, an event is entered in the index table, if enabled. The idle timer repeats the timeout until a packet is received.
Audio/Video Interface
RAVE interfaces with the audio/video decoders via external DRAM buffers. Each AV channel is allocated two external DRAM
buffers; one for data, and the other for descriptors. Each channel's descriptor buffer contains entries which points to relevant
locations within the data buffer, such as start code locations, PTS information, etc.
These descriptors are used by the video and audio decoders to perform frame synchronization, error recovery, timestamp
management, and various other functions.
Each AV channel is fully independent of the other ones, and can be mapped to a separate audio or video decoder. The AV
channels can accept data in any of the following input formats:
1
MPEG transport (from live or playback source)
2
DIRECTV transport (from live or playback source)
3
PES (playback source)
4
ES (playback source)
5
Program Stream (playback source)
The AV channels also support the following output formats to the downstream decoders:
1
Transport output (from transport input)
2
PES output (from transport or PES input)
3
ES output
AV channels support removal of emulation prevention bytes for AVC and VC-1 formats. They can also assist the downstream
decoders in performing frame synchronization.
Playback
The data transport module supports five independent playback modules. The following description is for a single playback
module.
The playback function is used to provide either MPEG Transport Stream (TS), DIRECTV transport stream, PES, ES, or
Program Stream data to the audio decoder and video decoder and/or to the Remux modules. Additionally, the playback
function can route data from memory though the data transport block for PID parsing, descrambling and/or filtering to be
recorded, stored in the message buffers, or routed to RAVE and/or high-speed interface. The playback module supports
transport stream with or without local timestamps. The host CPU is responsible for putting the data into external DRAM from
wherever the data is really being sourced (i.e., hard drive, internet, transport memory buffer, etc.) Once the data has been
put into external DRAM, the playback module can be enabled to read the data from external DRAM and deliver it to RAVE
and/or to the high speed transport and Remux modules. The playback circuit also uses linked-list descriptors for buffer
management.
