Difference between revisions of "Bidirectional PAD communication protocol"

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The current [[ODR-PadEnc]] to [[ODR-AudioEnc]] communication is done through a nonblocking FIFO.
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The communication between [[ODR-PadEnc]] and [[ODR-AudioEnc]] was done using a nonblocking FIFO until ODR-PadEnc v3, and was subsequently replaced by a unix domain datagram socket.
  
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The proposal is to replace it by a UDP-based request/reply protocol.
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The implementations are in https://github.com/Opendigitalradio/ODR-PadEnc/blob/master/src/pad_interface.cpp and https://github.com/Opendigitalradio/ODR-AudioEnc/blob/master/src/PadInterface.cpp
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For every audio frame, the ODR-AudioEnc checks if a block of PAD data is available by doing a nonblocking recv() on the UDP socket. If yes, it inserts it into the audio frame; if not, the audio frame will not contain PAD. In any case, it sends a request to ODR-PadEnc for new data:
 
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    UDP PAD Request version 1 - message format
 
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    | version (1 byte) |
 
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    | 0x1              |
 
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ODR-PadEnc prepares the PAD block and answers with a UDP reply message:
 
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    UDP PAD Reply version 1 - message format
 
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    | version (1 byte) | PAD data (N bytes) |
 
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    | 0x1              |      <PAD>        |
 
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TODO:
 
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* Define the order of bytes for the PAD data
 
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* Endianness of multi-byte values (none yet)
 
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* Do we want to add a type field with a different value for request and reply?
 

Latest revision as of 09:21, 23 September 2020

The communication between ODR-PadEnc and ODR-AudioEnc was done using a nonblocking FIFO until ODR-PadEnc v3, and was subsequently replaced by a unix domain datagram socket.

The implementations are in https://github.com/Opendigitalradio/ODR-PadEnc/blob/master/src/pad_interface.cpp and https://github.com/Opendigitalradio/ODR-AudioEnc/blob/master/src/PadInterface.cpp

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