title: MoviePy: Concatenating video clips causes weird glitches in final video
body: <p>Is there a way to successfully always patch up any clips together in such a way that prevents weird glitches? I put together a <code>.mp4</code> from smaller <code>.mp4</code> files and I got a final video with weird glitches. I am running Python 3.6.1 on Windows 10 through Sublime Text 3. I used MoviePy to do the concatenation.</p>
  
  <p><strong>The code:</strong></p>
  
  <pre><code>from moviepy.editor import VideoFileClip, concatenate_videoclips
  import os.path
  
  path = "C:/Users/blah/videos/out/"
  
  cliparray = []
  
  for filename in os.listdir(path):
      cliparray.append(VideoFileClip(path + filename))
  
  final_clip = concatenate_videoclips(cliparray)
  
  final_clip.write_videofile(path + "concatenatedvideo.mp4", codec = "libx264")
  </code></pre>
  
  <p><strong>The weird glitches:</strong></p>
  
  <ol>
  <li>One of the clips turns into a 3x3 grid of smaller clips.</li>
  <li>Another has the audio not lined up with the video</li>
  <li>Another is sped up faster than what was normal.</li>
  </ol>