title: Creating greyscale video using Python, OpenCV, and numpy arrays
body: <p>I am using 32-bit python with OpenCV 2.3.1.  I am trying to write 2-dimensional numpy arrays to a opencv video writer.  My code is similar to :</p>
  
  <pre><code>import cv2 as cv
  import numpy as np
  
  fourcc = cv.cv.CV_FOURCC('D', 'I', 'V', 'X')
  writer = cv.cv.CreateVideoWriter("test.mpg", courcc, 10, (256,256))
  if not writer:
       print "Error"
       sys.exit(1)
  
  for ii in range(numberOfFrames):    
      numpy_image = GetFrame(ii)    #Gets a random image
  
      cv_image = cv.cv.CreateImage((256,256), cv.IPL_DEPTH_8U, 1)
      cv.cv.SetData(cv_image, numpy_image.tostring(), numpy_array.dtype.itemsize*1*256)
  
      cv.cv.WriteFrame(writer, cv_image)
  
  del writer
  </code></pre>
  
  <p>I can see that I have the appropriate data in my numpy array.  And if I try reading the data back from the iplImage I see it is still there.  However, writing the frame does not appear to do anything.  No file is being made or throwing any error.  What could I be doing wrong?  Thanks in advance.</p>