time stamp not increasing, aux data interleave, binary output

jianbintangjianbintang Melbourne
edited February 2017 in OpenBCI_GUI
Hi, 

Here is the raw data I got with 8 channels. My questions are
1: if sample rate is 250Hz, I expect the time stamp will in 0.004 step, but it seems not, why?
2: for the last 2-4 collum, it is:  Accel Data (in G) interleaved with Aux Data? may I know what is the meaning of interleaved with AUX Data?
3: Is it possible to save it in binary to save file size and reduce wireless traffic?

Thank you very much!


%OpenBCI Raw EEG Data
%
%Sample Rate = 250.0 Hz
%First Column = SampleIndex
%Last Column = Timestamp 
%Other Columns = EEG data in microvolts followed by Accel Data (in G) interleaved with Aux Data
0, 75561.05, 64046.38, -187500.02, -187500.02, 46287.06, 46024.03, 46088.63, 64357.91, 0.016, 0.474, 0.114, 12:30:54.403
1, 75540.76, 64015.62, -187500.02, -187500.02, 46587.18, 46188.85, 46114.80, 64292.18, 0.000, 0.000, 0.000, 12:30:54.883
2, 75085.32, 63538.88, -187500.02, -187500.02, 46615.46, 46460.29, 45689.04, 64611.76, 0.000, 0.000, 0.000, 12:30:54.884
3, 74793.98, 63247.59, -187500.02, -187500.02, 46317.13, 46468.63, 45363.09, 64885.01, 0.000, 0.000, 0.000, 12:30:54.884
4, 75086.05, 63556.58, -187500.02, -187500.02, 46099.87, 46181.70, 45600.33, 64711.41, 0.000, 0.000, 0.000, 12:30:54.884
5, 75568.36, 64039.73, -187500.02, -187500.02, 46286.95, 46017.30, 46072.11, 64330.53, 0.000, 0.000, 0.000, 12:30:54.885
6, 75551.42, 64017.56, -187500.02, -187500.02, 46598.31, 46184.67, 46105.88, 64257.84, 0.000, 0.000, 0.000, 12:30:54.885
7, 75091.38, 63544.78, -187500.02, -187500.02, 46615.19, 46453.54, 45664.03, 64578.17, 0.028, 0.936, 0.228, 12:30:54.885
8, 74852.21, 63312.16, -187500.02, -187500.02, 46351.35, 46482.86, 45386.29, 64852.54, 0.000, 0.000, 0.000, 12:30:54.886
9, 75167.91, 63648.67, -187500.02, -187500.02, 46168.55, 46229.98, 45658.82, 64698.06, 0.000, 0.000, 0.000, 12:30:54.886
10, 75657.39, 64148.92, -187500.02, -187500.02, 46366.32, 46085.83, 46147.37, 64334.53, 0.000, 0.000, 0.000, 12:30:54.886

Comments

  • wjcroftwjcroft Mount Shasta, CA
    edited February 2017
    The first column is NOT a time stamp, but a sample counter index.

    Yes, AUX data is interleaved so as to make space for your own AUX info if you have some.

    I saw that eventually EDF / BDF output format for the GUI will be supported, not sure the timeframe. Wireless data IS binary already, this is just the GUI output in text format.
  • jianbintangjianbintang Melbourne
    HI， wjcroft: Thanks very much for your reply!

    1:The last column is timestamp. but it increases like 883,884,884,884,885. I expect it would be kind of 883,887,891(with 0.004 step because 250Hz sampling)
    2:Here is my understanding and my question of data:
    0(index), 75561.05(ch1), 64046.38(ch2), -187500.02(ch3), -187500.02(ch4), 46287.06(ch5), 46024.03(ch6), 46088.63((ch7)), 64357.91(ch8), 0.016(accel in x?), 0.474(accel in y?), 0.114(accel in z?), (where is aux data? how it is interleaved?) 12:30:54.403(timestamp)
    3: where is storage of binary data? I only found txt file. 

    Thanks again!
  • wjcroftwjcroft Mount Shasta, CA
    edited February 2017
    1. right, sorry I missread your initial comment. I'm going to mention AJ Keller @pushtheworld, the V2 firmware dev. You may not be configuring the Cyton to output the correct timestamp values. Or the GUI might be miss printing the correct binary stamps with the wrong text.

    2. correct. The Accel values are only inserted every 'n' EEG samples. The other slots (shown as zeros) could conceivably be filled with your own AUX data, if you wrote custom firmware.

    3. I said 'eventually' GUI will output EDF (16 bit format) or BDF (24 bit format). As I said, I don't know when this is expected. It could be one of the upcoming GUI Widgets that Gabe is working on. See the thread about LSL Widgets.
     
  • wjcroftwjcroft Mount Shasta, CA
    Go ahead and log an issue here on the GUI Github. Regarding the wonky time stamps. Not sure that is the best place, but a start. This may not be a bug, but a configuration error. AJ @pushtheworld needs an open issue to investigate.


  • jianbintangjianbintang Melbourne
    Thanks for the suggestion. I put to:
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