Packet loss with OpenViBE and Python

cookednoodle · February 2016

Hello,

I am trying to use my OpenBCI board with OpenViBE. However, I get errors about discontinuous data. I suspect this is from packet loss. I see packet loss warnings from the OpenViBE acquisition server when using the OpenBCI driver. I wrote a Python script with the Python API to check the sample IDs. I see a drop every ten seconds or so of either 1, 20, or 21 packets.

Anyone else having success with OpenBCI and OpenViBE? Anyone have any idea why the packets are only dropped in batches of 1, 20, or 21?

Versions:

Ubuntu 14.04
OpenViBE 1.1
OpenBCI_Python master branch at 35a37a8

Thank you!

wjcroft · March 2016

I'm going to mention Jeremy @jfrey, who wrote the drivers. With OpenViBE have you tried adjusting the settings in the Preferences button (Global Configuration / Drift tolerance, etc.) I believe some correction happens normally because the OpenBCI mainboard is not crystal controlled. Hence the samples are coming in at not exactly 250.00 sps. So that is a 'feature' and not a bug.

http://openvibe.inria.fr/acquisition-server/

With Python, there is another thread that discusses this, I don't know if any resolution or hints at solutions have been determined,

http://openbci.com/forum/index.php?p=/discussion/378/openbci-python-unreliable-linux-mac-acquisition

http://openbci.com/forum/index.php?p=/discussion/313/actual-sampling-rate-around-250-5-hz

So the Python with Linux is really a separate issue. OpenViBE is probably doing what you are telling it in that config panel.

William

jfrey · March 2016

Hi,

The packets drops should be mentioned in the console of the OpenViBE acquisition server if it happens -- and your python test seems to prove that you do have issues here. Packets drops are not related to the driver but to the hardware though, maybe the wireless link is weak?

wjcroft · March 2016

@cookednoodle, do you have access to a Windows machine where you could test the Python? I assume your use of OpenBCI_GUI is working ok on all these platforms.

William

Packet loss with OpenViBE and Python

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