Re: [Discuss-gnuradio] Higher Accuracy Metadata Header?

[Marcus D. Leech]

On 04/21/2016 11:41 AM, Michael Skaggs wrote:
> I'm trying to time/sample synchronize RF recordings with two 
> B200minis. I am using the detached Metadata File Sink in GRC. Both 
> recordings are at 30MSps and both B200mini boards are synchronized to 
> the same 1PPS signal.
>
> My issue is this, when I extract the data from the Metadata header 
> file, the "rx_time" value is only accurate to 10e-4 seconds (0.0001s). 
> Which, with a recording at 30MSps, this will only give me a sample 
> alignment accuracy to 10e-4(s)*30(MS/s) = 30,000 samples.
>
> If I'm attempting to align the two recordings by samples or time, this 
> is not nearly accurate enough. Is there a way that I can get more 
> accuracy out of my metadata header or a way that I can synchronize the 
> recordings of these B200minis?
>
> Thanks,
> Michael
The precision of the timestamps from UHD should have a precision of 
whatever the master-clock is on the device--how are you interpreting
  the rx_time tag?  It's two parts--a uint64 with the full-seconds 
portion, and a double-precision float for the fractional part.