TM
Virtual Components for the Converging World
Amphion continues to expand its family of application-specific cores
1
See http://www.amphion.com for a current list of products
Transport Stream
Demux
CS6804 Technical Brief
The CS6804 multi-source MPEG-2 transport stream demux is designed for a broad range of system applications
requiring the demultiplexing of data carried over the MPEG-2 transport stream multiplex. This application
specific silicon core is capable of demultiplexing four transport streams simultaneously and is ideally suited for
integration into next generation, versatile set-top box applications. The CS6804 demux can be customized for
specific applications and made available in ASIC or FPGA netlists that have been hand crafted by Amphion for
optimal performance while minimizing power consumption and silicon area.
Figure 1: Amphion Multi Source Transport Stream Demux - Block Diagram
Input
FIFOs
Video
PES Data
Source0
Source1
Source2
Source3
PID
Match
Units
Video
FIFO
Audio
FIFO
Audio
PES Data
Clock
Recover
PCR
PSI
FIFO
Adaption
FIFO
Packet
header
Transport
Stream
Parser
Host Interface
To system
memory
and host
TS DEMUX KEY FEATURES
Supports four transport stream inputs from
independent sources
PID filtering:
-
PID lookup for up to 64 PIDs
-
Fully host configurable
Calculation of Program Clock Reference for
clock recovery hardware
Supports up to four video and four audio ele-
mentary streams per input source
CRC carried out on PSI sections in hardware
Host interface to system RAM for storage and
interpretation of:
-
PSI sections
-
Adaptation data
-
Packet Header data
Input Data Rate:
-
Total Input Maximum: 800Mbps
-
Maximum on one input channel: 300Mbps
BENEFITS
Can support combined MPEG2/4/7 streams
Flexibility to achieve system performance/
power/cost goals
Can be customized to suit individual applica-
tions
APPLICATIONS
Next generation digital cable and satellite set-
top box.
Multi-source personal digital video recorders
DVD
Broadband communications
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CS6804
Transport Stream Demux
CS6804 FUNCTIONAL DESCRIPTION
The CS6804 accepts transport stream packets in byte-aligned
bytes from system front end (FEC decoders) or similar
sources. The core interfaces with a host processor via an
AMBA host interface to allow the setting of up to 64 PID
filters. The core parses out the video and audio Packetized
Elementary Stream (PES) packets for selected PIDs for further
decoding. This enables quick integration into simple decoders
which require easy access to the video and audio PES packets.
Where more control is required, the core stores PSI sections,
adaptation data and header data in queues in system memory
for interpretation by the host processor. This allows the
system to quickly get access to the PES data while enabling
straightforward customization to the individual application.
A Cyclic Redundancy Check (CRC) is carried out on the PSI
sections within the core as they are parsed out and stored in
system memory. If an error is found then a flag is set to notify
the host of this. The Program Check Reference (PCR) carried
in the adaptation field is calculated within the core and output
for direct use by clock recovery hardware.
FUNCTIONAL BLOCK OVERVIEW
Input FIFOs
There are four Asynchronous Input FIFOs. They provide a
bridge between the clock domain of the input and of the core
itself. This allows a direct interface to the output of the FEC
decoders in a system front end (e.g. in a set top box).
PID Match Units
Each of the 64 PID Match units stores a PID value and
descriptor value as defined by the host processor. The PID
source number is also written in by the host processor. The
PID Match units are used to filter for useful PIDs within the
transport stream. Once a valid packet is processed within the
TS Parser, the PID number is parsed out and compared to the
contents of each of the match units. A match will occur when
the source number and PID number equal the respective
values stored in the PID Match unit. If a match is found, a
Match signal is set high and the index to the matching PID
Match unit is determined. The rest of the packet is parsed and
any payload is sent to the appropriate FIFO. The output FIFO
is selected depending on the Descriptor register in the
corresponding PID Match unit.
Transport Stream Parser
The payload is separated from the packet header and
adaptation field if present. The parser extracts data from
packets of a PID that it has been programmed to recognize.
The PID Match unit indicates when this match condition
occurs and what sort of stream the packet belongs to so that it
can be parsed according to its type. The data is then either
parsed into system memory for further interpretation (in the
case of PSI or adaptation data) or parsed out for buffering and
consumption by PES parsers.
Up to four video streams and four audio streams can be
handled by the parser per input source. Context switching
occurs between the four input sources and is carried out at
byte level so as to preserve the timing and recovery of the PCR
for each program in each source.
Host Interface and Memory Structure
The host interface allows control of which PIDs are required
and hence which packets will be parsed. Setting up the 64
entry PID match unit allows this filtering at the PID level.
PSI sections, the adaptation field and packet header info can
be written to system memory at set locations determined by
the core. Each stored PID has a queue associated with it and
the position and organization of these queues is managed by
the core. The memory required is 32Mbytes in size and is
aligned on a 32Mbyte boundary. This memory can be located
anywhere within the overall system memory as the host
processor generates the offset for the addresses. In this way,
the host can interrogate the control registers for the queues to
identify the location of the required data and hence enable
host parsing of the tables and adaptation fields if required.
3
TM
SYSTEM DIAGRAM
Figure 2 shows an example system with four transport streams from four separate sources. The PES output can be parsed using
PES parsers and input into a multi-stream video decoder such as Amphion's CS6652 to decode two MPEG-2 video streams (or the
CS6654 for decoding four MPEG-2 video streams). The outputs from the decoder are then encoded for PAL/NTSC display. A
similar flow is shown for the audio components in the transport streams.
Figure 2: Example System Featuring the CS6804 Transport Demux
Terrestrial
CS6804
Multi-source
Transport
Stream
Demux
Front End
Source0
Front End
Source1
Front End
Source2
Front End
Source3
Storage
Media
Cable
Satellite
Video PES
Parser
Video PES
Parser
CS6652
Multi
Stream
Video
Decoder
Display
(main)
Display
(PiP)
PAL/NTSC
Encoder
PAL/NTSC
Encoder
Audio PES
Parser
Speaker
Audio
DAC
Audio
Decoder
CS6804
Transport Stream Demux
TM
Virtual Components for the Converging World
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Amphion, the Amphion logo,"Virtual Components for the Converging World", are trademarks of Amphion Semiconductor Ltd. All others are the property of their
respective owners.
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02/02 Publication #: TB6804 v1.0A
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