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caer timestamp progression

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2017-03-07
2017-03-07
  • Sim Bamford

    Sim Bamford - 2017-03-07

    I'm looking at an aedat file recorded by caer. Here is the progression of the main time stamp for the first few packets:

    packet: 1; timestamp: 0
    packet: 2; timestamp: 0
    packet: 3; timestamp: 5221
    packet: 4; timestamp: 8398
    packet: 5; timestamp: 10002
    packet: 6; timestamp: 10304
    packet: 7; timestamp: 13448
    packet: 8; timestamp: 20002
    packet: 9; timestamp: 2147483647
    packet: 10; timestamp: 104

    I guess there was a timestamp reset request at packet 10; however I don't understand why there is a very high timestamp at packet 9 - is this expected behaviour, or should I look at my code for decoding the timestamps?

     
  • Sim Bamford

    Sim Bamford - 2017-03-07

    Ah: The number 2,147,483,647 is the eighth Mersenne prime, equal to 2^31 − 1 ...

     
  • Sim Bamford

    Sim Bamford - 2017-03-07

    So packet 9 contains just one special event - a timestamp reset event, and its timestamp is 7FFFFFFF - is this expected behaviour?

     
  • Luca Longinotti

    Luca Longinotti - 2017-03-07

    Yes, this is correct. Timestamp reset is sent as a separate packet with only itself, to act as a separation point in the stream, and it gets the highest timestamp of the old stream, to ensure it's always at the end (or conversely, just before the new stream starts at 0).