OpenCV Optical Flow Lucas Kanade Pyramid

[Kirielson]

Hello, I'm having trouble running the CalcOpticalFlowPyrLK in Python. When I try doing the calculations for the Lucas Kanade code it will not compute the error I get is the following:

File "****", line 63, in callback
    (currFeatures, status, track_error) = cv.CalcOpticalFlowPyrLK(old_image, new_image, old_pyramid, new_pyramid, old_features, (3,3), 1, (cv.CV_TERMCRIT_ITER, 10, 0) , 0)
error: pyramid A has insufficient size

Here's the following code:

new_pyramid = self.pyrdownsize(new_image) 
    old_pyramid = self.pyrdownsize(old_image)
    (currFeatures, status, track_error) = cv.CalcOpticalFlowPyrLK(old_image, new_image, old_pyramid, new_pyramid, old_features, (3,3), 1, (cv.CV_TERMCRIT_ITER, 10, 0) , 0)

def pyrdownsize(self, cv_image):
    (rows,cols) = cv.GetSize(cv_image)
    pyr = cv.CreateMat(int(cols/2), int(rows/2), cv.GetElemType(cv_image)) 
    cv.PyrDown(cv_image, pyr)
    return pyr

Is there something I'm not seeing?

Thanks for the help once again.