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PostPosted: Fri Jun 05, 2015 3:19 pm 

Joined: Sun Nov 23, 2014 5:32 am
Posts: 21
I have make the following editing on the averaging signal example in python tutorial, and I apply it on 3 channels with one input to the python scripting toolbox and one output , but it's always gives me that there is one input and one output, I conclude that we have to do channel localization and pass each channel to an input of the python toolbox, for example if i have 3 channels, then I should have 3 input signal to that toolbox and the same thing applies to the output of the toolbox, is that necessary?

the expected output of my code is to average each channel.

# we use numpy to compute the mean of an array of values
import numpy

 # let's define a new box class that inherits from OVBox
class MyOVBox(OVBox):
    def __init__(self):
    # we add a new member to save the signal header information we will receive
       self.signalHeader = None

    # The process method will be called by openvibe on every clock tick
    def process(self):
       # we iterate over all the input chunks in the input buffer
      x = len(self.input)
      print ("the size is ", x)
      for i in range(len(self.input)):
       for chunkIndex in range( len(self.input[i]) ):
          # if it's a header we save it and send the output header (same as input, except it has only one channel named 'Mean'
          if(type(self.input[i][chunkIndex]) == OVSignalHeader):
             self.signalHeader = self.input[i].pop()
             outputHeader = OVSignalHeader(
             [1, self.signalHeader.dimensionSizes[1]],

          # if it's a buffer we pop it and put it in a numpy array at the right dimensions
          # We compute the mean and add the buffer in the box output buffer
          elif(type(self.input[i][chunkIndex]) == OVSignalBuffer):
             chunk = self.input[i].pop()
             numpyBuffer = numpy.array(chunk).reshape(tuple(self.signalHeader.dimensionSizes))
             numpyBuffer = numpyBuffer.mean(axis=0)
             chunk = OVSignalBuffer(chunk.startTime, chunk.endTime, numpyBuffer.tolist())
          # if it's a end-of-stream we just forward that information to the output
          elif(type(self.input[i][chunkIndex]) == OVSignalEnd):

 # Finally, we notify openvibe that the box instance 'box' is now an instance of MyOVBox.
 # Don't forget that step !!
box = MyOVBox()

the output for the
print ("the size is ", x)
statement always gives me one , and the oscillator is generate 3 channels !,and I expect to have 3 element (or channels) in the
not one!

this my scenario and the configuration of sinus oscillator which is generate 3 channels
delete.png [ 18.86 KiB | Viewed 1796 times ]

My operating system is ubuntu 14.04 , using openViBE1.0.0

delete.png [ 31.47 KiB | Viewed 1796 times ]
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PostPosted: Tue Jun 09, 2015 9:43 am 

Joined: Tue Apr 01, 2014 8:22 am
Posts: 71
You are confusing stream and stream structure.

You box have only one input, so self.input is size 1. For example, if the signal display was a python box, self.input would be equal to 3.

The channel is not a characteristic of the box, but of the stream. As you are using the signal type stream, the stream will have a fix structure (see It will be composed of a 2-dimensional matrix of size [N x M] with N the amount of channel, and M the amount of samples by channel.


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