OpenViBE forum

These questions have been raised by a recent discussion we had with one of our users.
As it may benefit to others, here is the transcription :

Laurent-

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The best to start, is looking at the documentation of the box on the dedicated section (press "F1" on a box to open your web browser ). The keyboard stimulator sends stimulation codes on its output when the user presses a given key on the keyboard while focus is on the stimulator window.

In the p300-speller-1-aquisition scenario this box has been renamed into "press 'a' to start" (which is also mentionned in the scenario comments).
When playing the scenario, the stimulator should pop-up. As you will see, selecting this window and pressing 'a' will trigger the stimulation OVTK_StimulationId_Label_01 and releasing the key will trigger OVTK_StimulationId_Label_00. The box is connected to the P300 Speller Stimulator box, which "start stimulation" setting is set to OVTK_StimulationId_Label_00.
Thus, when the box will receive the stimulation OVTK_StimulationId_Label_00 from the keyboard stimulator, the flashing sequence will start.

Every stimulation in the stream received by the Generic Stream Writer will be written in the .ov file produced.


Hope this helps!

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If the acquisition session was OK (no error messages, the file is produced and its size is superior to few ko), you should be able to use a Generic Stream writer and a signal Display to show the EEG and stims. Maybe your file reader is not configured (as its name suggests, the file handles "generic" streams, which means you have to set the outputs so they match the actual structure of the streams stored in the file. For example, you can use the Generic Stream Writer box in the p300-speller-2-train-classifier scenario as it should match the file structure given by the acquisition scenario.

If the acquisition dropped during the session, the acquisition client box has been disconnected. There is no automatic recovery, so the signal stream was simply cut beyond repair.
I tested by disconnecting the Acquisition Server during a session. A correct file was indeed produced, and I could display the EEG afterward... Maybe someting else happened in your case.
What the console said ? no warning or error message ?

Example :

Means the acquisition client box has been disconnected from the server

If the .ov file produced is 100 ko sized, there is definitely a problem

Laurent

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Checkout my (old) blog for some OpenViBE tips & tricks : here !

The stimulation codes used in the first scenario are given by the P300 Speller stimulator (codes for the flashs on row and columns) and the Lua Stimulator (which letter is a target and which one is a non-target). These codes are the very same used by the training scenarios in the stimulation based epoching (to extract the exact time-windows for each event) or Classifier trainer.

Generally speaking, when designing your BCI with OpenViBE
- choose the stimulations codes you will need (instruction, events, etc.)
- make sure you record the stimulation codes in the training file
- use these stim codes in the training scenario

Laurent-

_________________
Follow us on twitter >> openvibebci

Checkout my (old) blog for some OpenViBE tips & tricks : here !