Hi chantrip and welcome on board !
xDAWN filter has encountered 'Bad matrix size - Expected 3 input channels and received 14 input channels'
The xDAWN filter
box in these scenarios is a spatial filter box
. It reduces the number of input channel with linear combinations, for example from 14 input channels to 3 combinations (3 output channels).
The error you have means that the filter that you trained requires 3 input channels, and the box received 14.
so far the only change that I've made is in the setting value in line 8 of the file 'p300-speller-stimulator.cfg' from 10 to 1
So you changed the number of trials from 10 letters to 1.
Btw you just need to uncheck the tick box "override settings with configuration file" to change the settings directly in the box. Much more convenient than in the xml file
Indeed this change is not what causes the error you mentioned.
Did you follow all the steps required ?
0. turn on the acquisition server, verify the connection and signal quality with the monitoring scenario
1. acquisition : acquire some data (10 letters is default behaviour)
2. train xDAWN on the file you just acquired
(modify the box Generic Stream Reader to do so). This step should end with "Training finished. Eigen values are ..."
3. train the LDA classifier with the same file
. This step should end with classifier performances in %.
5. [optional] retrain xDAWN then Classifier with the last online file for better results
To make the P300 speller work with the Emotiv headset, some changes may be required.
The default scenario was tested with a 512Hz device, and a Signal Decimation box
is used to lower it by factor 4. Emotiv EPOC is sampled at 128Hz, so you need to either oversample the Emotiv driver in the Acquisition Server preferences by factor 4, or remove the decimation in the scenarios.
If the xDAWN spatial filter computation seems to freeze, or ends up with "decomposition failed", it means that the algorithm thinks that a channel is already a combination of others sensors. You may have to randomly remove some channels (1-2) with a Channel Selector box
just after the acquisition client. This happened to me one time.
Last advice, you should be aware that you may not reach very good performances at first try. Some tweaking in the stimulator settings may be required.
Come back to us if you experience that kind of problem, and of course if your primary problem remains (this one should definitely find a solution
Hope this helps.
Follow us on twitter >> openvibebci
Checkout my (old) blog for some OpenViBE tips & tricks : here !