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PostPosted: Thu Mar 05, 2015 9:35 am 

Joined: Sun May 04, 2014 12:25 pm
Posts: 1
Hello everybody,

I have written a script in python but for some reason OpenViBE lags when I run the script and I get an output like
[WARNING] <Player::can not reach realtime> 1 second(s) late...

I thought the problem was an infinite loop or so in my code, so I added debug info but it turns out OV seems to stuck between two OVBox.process() calls.
Here are the relevant parts (I hope!) of my code
   def process(self):
      print "new process"
      while len(self.input[0]):
         print 'start loop'
         buff = self.input[0].pop()
         if(type(buff) == OVSignalHeader):
            self.signalHeader = buff
            print 'init'
         elif(type(buff) == OVSignalBuffer):
            numpyBuffer = np.array(buff).reshape(tuple(self.signalHeader.dimensionSizes))
            prediction = best_cca() # returns either of [7,9,11,13,15,-1]
            self.send_stimulation(prediction, buff)
            print "sent stimulation", prediction
         elif(type(buff) == OVSignalEnd):
            outputEnd = OVStimulationEnd(buff.startTime, buff.endTime)
            print 'end'
      print 'end process'
   def init(self):
      outputHeader = OVStimulationHeader(

   def send_stimulation(self, prediction, buff):
      if prediction > 0: stim = OpenViBE_stimulation['OVTK_StimulationId_LabelStart'] + prediction
      else: stim = OpenViBE_stimulation['OVTK_StimulationId_NonTarget']
      stimSet = OVStimulationSet(buff.startTime, buff.endTime)
      stimSet.append(OVStimulation(stim, buff.endTime, 0.))

with an output like
new process
end process
new process
start loop
sent stimulation 7
end process
[WARNING] <Player::can not reach realtime> 1 second(s) late...

This doesn't happen systematicly, but every five predictions or so... Does anybody know what mistake I have made?

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PostPosted: Mon Mar 09, 2015 8:29 am 

Joined: Tue Dec 04, 2012 3:53 pm
Posts: 720
Location: INRIA Rennes, FRANCE
Hi Oettam,

one suspicious thing I see is that you're calling init from process(). This likely shouldn't be done.

To debug this, what I'd do is that I'd take the hello world example script

class MyOVBox(OVBox):
        def __init__(self):

        def initialize(self):
                # nop

        def process(self):
                # print something

        def uninitialize(self):
                # nop

box = MyOVBox()

and check that it runs properly. Then, line by line, start modifying it towards your script and see where the problem appears for the first time.

Happy hacking,

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