title: matplotlib.animation error - The system cannot find the file specified
body: <p>When trying to run a simple <a href="http://matplotlib.sourceforge.net/examples/animation/dynamic_image2.html" rel="nofollow noreferrer">animation example code</a> in python, I am getting an error which I am not able to resolve.</p>
  
  <pre><code>Traceback (most recent call last):
  File "D:/CG/dynamic_image2.py", line 29, in &lt;module&gt;
      ani.save('dynamic_images.mp4')
  File "C:\Python27\lib\site-packages\matplotlib\animation.py", line 127, in save
      self._make_movie(filename, fps, codec, frame_prefix)
  File "C:\Python27\lib\site-packages\matplotlib\animation.py", line 164, in _make_movie
      stdout=PIPE, stderr=PIPE)
  File "C:\Python27\lib\subprocess.py", line 679, in __init__
      errread, errwrite)
  File "C:\Python27\lib\subprocess.py", line 893, in _execute_child
      startupinfo)
  WindowsError: [Error 2] The system cannot find the file specified
  </code></pre>
  
  <p>I found similar situations (<a href="https://stackoverflow.com/questions/8928989/biopython-error-the-system-cannot-find-the-file-specified">link1</a> , <a href="https://github.com/pypa/virtualenv/issues/190" rel="nofollow noreferrer">link2</a> ) but still I don't know how to resolve mine...</p>
  
  <p>I am using:
  Python 2.7.2 |EPD 7.2-2 (32-bit)| (default, Sep 14 2011, 11:02:05) [MSC v.1500 32 bit (Intel)] on win32</p>
  
  <p>I hope somebody can help me!</p>