title: Create a video of layered videos
body: <p>I'm a python and OpenCV beginner!
  I would like to create a video made of 3 others videos. Each video is a moving car on a black background</p>
  
  <p>I created the video which is empty for the moment: </p>
  
  <pre><code>video_summary=cv2.VideoWriter(video_output_path ,fourcc,video_fps ,(480,270), True)
  </code></pre>
  
  <p>Now, I would like to add videos called 0, 2 and 4 from "video_a_ajouter" in video_summary.</p>
  
  <pre><code>video_a_ajouter=[0,2,4]
  video_working=[]
  </code></pre>
  
  <p>So, I did this:</p>
  
  <pre><code>for i in video_a_ajouter:    video_working.append(cv2.VideoCapture(output_directory_path+'output_TP_'+str(video_a_ajouter[0])+'.avi'))
          video_a_ajouter.remove(video_a_ajouter[0])
  </code></pre>
  
  <p>I would like to know how to put the 3 videos in video_summary, considering that 0 overlaps 2 and 2 overlaps 4</p>
  
  <p>Thank you in advance for your help !! :)</p>