Reassembly of DVB PSI Tables
Components that take a stream of MPEG Transport stream packets
containing Programme Status Information (PSI) tables and reassembles the
table sections, ready for parsing of the data within them.
ReassemblePSITables can do this for a stream of packets containing a
single table.
ReassemblePSITablesService provides a full service capable of
reassembling multiple tables from a multiplexed stream of packets, and
distributing them to subscribers.
Example Usage
A simple pipeline to receive, parse and display the Event Information
Table in a multiplex:
FREQUENCY = 505.833330
feparams = {
"inversion" : dvb3.frontend.INVERSION_AUTO,
"constellation" : dvb3.frontend.QAM_16,
"code_rate_HP" : dvb3.frontend.FEC_3_4,
"code_rate_LP" : dvb3.frontend.FEC_3_4,
}
EIT_PID = 0x12
Pipeline( OneShot( msg=["ADD", [0x2000] ] ), # take all packets of all PIDs
Tuner(FREQUENCY, feparams),
DVB_SoftDemuxer( { EIT_PID : ["outbox"] } ),
ReassemblePSITables(),
ParseEventInformationTable(),
PrettifyEventInformationTable(),
ConsoleEchoer(),
).run()
Set up a dvb tuner and demultiplexer as a service; then set up a PSI
tables service (that subscribes to the demuxer); then finally subscribe
to the PSI tables service to get Event Information Tables and parse and
display them:
RegisterService( Receiver( FREQUENCY, FE_PARAMS, 0 ),
{"DEMUXER":"inbox"},
).activate()
RegisterService( Graphline( PSI = ReassemblePSITablesService(),
DEMUXER = ToService("DEMUXER"),
linkages = {
("PSI", "pid_request") : ("DEMUXER", "inbox"),
("", "request") : ("PSI", "request"),
}
),
{"PSI_Tables":"request"}
).activate()
Pipeline( Subscribe("PSI", [EIT_PID]),
ParseEventInformationTable(),
PrettifyEventInformationTable(),
ConsoleEchoer(),
).run()
In the above example, the final pipeline subscribes to the 'PSI'
service, requesting the PSI tables in MPEG Transport Stream packets with
packet id 0x12.
The ReassemblePSITablesService service uses a ToService component to
send its own requests to the 'DEMUXER' service to ask for MPEG Transport
Stream packets with the packet ids it needs.
ReassemblePSITables
ReassemblePSITables reassembles one PSI table at a time from a stream
of MPEG transport stream packets containing that table.
Behaviour
Send individual MPEG Transport Stream packets to the "inbox" inbox
containing fragments of a particular PSI table.
ReassemblePSITables will reconstruct the table sections. As soon as a
section is complete, it will be sent, as a raw binary string, out of the
"outbox" outbox. The process repeats indefinitely.
If a shutdownMicroprocess or producerFinished message is received on
the "control" inbox, then it will immediately be sent on out of the
"signal" outbox and the component will then immediately terminate.
ReassemblePSITablesService
ReassemblePSITablesService provides a full service capable of
reassembling multiple tables from a multiplexed stream of packets, and
distributing them to subscribers.
Behaviour
ReassemblePSITablesServices takes individual MPEG Transport Stream
packets sent to its "inbox" inbox and reconstructs table sections,
distributing them to clients/subscribers that have requested them.
To be a client you can wrap ReassemblePSITablesService into a named
service by using a Kamaelia.Experiment.Services.RegisterService
component, and then subscribe to it using a
Kamaelia.Experiment.Services.SubscribeTo component.
Alternatively, send a 'ADD' or 'REMOVE' message to its "request"
inbox, requesting to be sent (or no longer be sent) tables from packets
of particular PIDs, and specifying the inbox to which you want the
packets to be sent. The format of these requests is:
("ADD", [pid, pid, ...], (dest_component, dest_inboxname))
("REMOVE", [pid, pid, ...], (dest_component, dest_inboxname))
ReassemblePSITablesService will automatically do the wiring or
unwiring needed to ensure the packets you have requested get sent to the
inbox you specified.
Send an 'ADD' request, and you will immediately start receiving
tables in those PIDs. Send a 'REMOVE' request and you will shortly no
longer receive tables in the PIDs you specify. Note that you may still
receive some tables after your 'REMOVE' request.
ReassemblePSITablesService will also send its own requests (in the
same format) out of its "pid_request" outbox. You can wire this up to
the source of transport stream packets, so that
ReassemblePSITablesService can tell that source what PIDs it needs.
Alternatively, simply ensure that your source is already sending all the
PIDs your ReassemblePSITablesService component will need.
If a shutdownMicroprocess or producerFinished message is received on
the "control" inbox, then it will immediately be sent on out of the
"signal" outbox and the component will then immediately terminate.
How does it work?
ReassemblePSITablesService creates an outbox for each subscriber
destination, and wires from it to the destination.
For each PID that needs to be processed, a ReassemblePSITables
component is created to handle reconstruction of that particular
table.Transport Stream packets arriving at the "inbox" inbox are sent to
the relevant ReassemblePSITables component for table reconstruction.
Reconstructed tables coming back from each ReassemblePSITables component
are forwarded to all destinations that have subscribed to it.
When ReassemblePSITablesServices starts or stops using packets of a
given PID, an 'add' or 'remove' message is also sent out of the
"pid_request" outbox:
("ADD", [pid], (self, "inbox"))
("REMOVE", [pid], (self, "inbox"))
This can be wired up to the source of transport stream packets, so
that ReassemblePSITablesService can tell that source what PIDs it
needs.
Takes DVB Transport stream packets for a given PID and reconstructs
the PSI packets from within the stream.
Will only handle stream from a single PID.
Inboxes
Outboxes
Methods defined here
Warning!
You should be using the inbox/outbox interface, not these methods
(except construction). This documentation is designed as a roadmap as to
their functionalilty for maintainers and new component developers.
main(self)
shutdown(self)
ReassemblePSITablesService() -> new ReassemblePSITablesService
component.
Subscribe to PSI packets by sending ("ADD", (component,inbox), [PIDs]
) to "request" Unsubscribe by sending ("REMOVE", (component,inbox),
[PIDs] ) to "request"
Inboxes
- control : Shutdown signalling
- request : Place for subscribing/unsubscribing from
different PSI packet streams
- inbox : Incoming DVB TS packets
Outboxes
- outbox : NOT USED
- signal : Shutdown signalling
- pid_request : For issuing requests for PIDs
Methods defined here
Warning!
You should be using the inbox/outbox interface, not these methods
(except construction). This documentation is designed as a roadmap as to
their functionalilty for maintainers and new component developers.
__init__(self)
handleSubscribeUnsubscribe(self,
msg)
main(self)
shutdown(self)
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