Example Usage

Read MPEG Transport Stream packets (188 bytes each) from a file in groups of 7 at a time (to fill an RTP packet) and send them in RTP packets over multicast to 224.168.2.9 on port 1600:

class PrePackage(Axon.Component.component):
    def main(self):
        SSRCID = random.randint(0,(2**32) - 1)      # random unique ID for this source
        while 1:
            while self.dataReady("inbox"):
                recvData = self.recv("inbox")
                self.send(
                  { 'payloadtype' : 33,             # type 33 for MPEG 2 TS
                    'payload'     : recvData,
                    'timestamp'   : time.time() * 90000,
                    'ssrc'        : SSRCID,
                  },
                  "outbox")
            yield 1


Pipeline( RateControlledFileReader("transportstream",chunksize=7*188),
          PrePackage(),
          RTPFramer(),
          Multicast_Transceiver(("0.0.0.0", 0, "224.168.2.9", 1600)

Timestamps for MPEG TS in RTP are integers at 90KHz resolution (hence the x90000 scaling factor). A random value is chosen for the unique source identifier (ssrc).

Save the payload from a stream of RTP packets being received from multicast address 224.168.2.9 on port 1600 down to a file:

Pipeline( Multicast_transceiver("0.0.0.0", 1600, "224.168.2.9", 0),
          SimpleDetupler(1),                      # discard the source address
          RTPDeframer(),
          RecoverOrder(bufsize=64, modulo=65536), # reorder packets
          SimpleDetupler(1),                      # discard the sequence number
          SimpleDetupler("payload"),
          SimpleFileWriter("received_stream"),
        )

RTPFramer behaviour

Send to RTPFramer's "inbox" inbox a dictionary. It must contain these fields:

{
    'payloadtype' : integer payload type
    'payload'     : binary string containing the payload
    'timestamp'   : integer timestamp (32 bit, unsigned)
    'ssrc'        : sync source identifier (32 bit, unsigned)

...and these fields are optional:

    'csrcs'        : list of contributing source identifiers (default = [])
    'bytespadding' : number of bytes of padding to be added to the payload (default=0)
    'extension'    : binary string of any extension data (default = "")
    'marker'       : True to set the marker bit, otherwise False (default=False)
}

RTPFramer automatically adds a randomised offset to the timestamp, and generates the RTP packet sequence numbers, as required in the specification (RFC 3550).

RTPFramer constructs an RTP packet matching the fields specified and sends it as a binary string out of the "outbox" outbox.

If a producerFinished or shutdownMicroprocess message is received on the "control" inbox. It is immediately sent on out of the "signal" outbox and the component then immediately terminates.

RTPDeframer Behaviour

Send to RTPDeframer's "inbox" inbox a binary string of an RTP packet, and the packet will be parsed, resulting in a (seqnum, packet_contents) tuple being sent to the "outbox" outbox. It will have this structure:

( sequence_number,
  {
    'payloadtype'  : integer payload type
    'payload'      : binary string containing the payload
    'timestamp'    : integer timestamp (32 bit, unsigned)
    'ssrc'         : sync source identifier (32 bit, unsigned)
    'csrcs'        : list of contributing source identifiers, [] if empty
    'extension'    : binary string of any extension data, "" if none
    'marker'       : True if marker bit was set, otherwise False
  }
)

See RFC 3550 for an explanation of the precise purposes of these fields.

If a producerFinished or shutdownMicroprocess message is received on the "control" inbox. It is immediately sent on out of the "signal" outbox and the component then immediately terminates.

class RTPDeframer(Axon.Component.component)

RTPDeframer() -> new RTPDeframer component.

Deconstructs an RTP packet, outputting (seqnum, dict) tuple where seqnum is for recovering the order of packets, and dict contains the fields from the RTP packet.

class RTPFramer(Axon.Component.component)

RTPFramer() -> new RTPFramer component.

Creates a complete RTP packet based on a dict structure describing the packet.