|Subject:||File metadata rx_time scaled 4x|
|Date:||Fri, 16 Jul 2021 20:01:32 +0000|
I want to record UTC-timestamped USRP data, and Iâ€™ve created a flowgraph using the file meta sink. I set the USRP time via set_time_now (in the final version this will become set_time_next_pps) before the file sink is created, and reading back immediately using get_time_now returns the same time. The files contain all the inline header fieldsâ€¦ but the rx_time appears to be consistently 4 times the true value!
USRP time set to 1626425142 seconds after epoch -> 07/16/21 08:45:42
get_time_now returns 1626425142 seconds
In the file header â€˜rx_timeâ€™ is followed by: 0c 00 00 00 02 0b 00 00 00 01 83 c5 1c d9 04 â€¦
0x0000000183c51cd9 = 6505700569 full secs
USRP time set to 1626439661 seconds after epoch -> 07/16/21 12:47:41
get_time_now returns 1626439661 seconds
File header â€˜rx_timeâ€™ is followed by: 0c 00 00 00 02 0b 00 00 00 01 83 c5 ff b5 04 â€¦
0x0000000183c5ffb5 = 6505758645 full secs
USRP time set to 100 seconds exactly
get_time_now returns 100 seconds
File header â€˜rx_timeâ€™ is followed by: 0c 00 00 00 02 0b 00 00 00 00 00 00 01 91 04 â€¦
0x0000000000000191 = 401 full secs
It looks like the fractional seconds part is affected in the same way â€“ inserting, say, a 0.1 sec sleep after setting the USRP time results in approximately 0.4 sec additional delay in rx_time.
Can anyone explain this!? All other header values come out as expected. Iâ€™m using Gnuradio version 22.214.171.124 with UHD 3.15.0.
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