cant play the saved video [closed]

edit

I have tried many codecs , all but the last one produce 0 bytes video, the last codec does produce a video file with some but then its not playable . This problem is driving me crazy , The code I am using is tested by other users n working. I have copied the opencv_ffmpeg310_64.dll file into the c:\python2.7 folder. I am on windows 10 and opencv 3.1.0 I tried all types of CODEC none are working.

 import numpy as np
    import cv2

    cap = cv2.VideoCapture(0)

    # Define the codec and create VideoWriter object
# Define the codec and create VideoWriter object
#fourcc = cv2.VideoWriter_fourcc(*'FFV1')
#fourcc = cv2.VideoWriter_fourcc(*'XVID')
#fourcc = cv2.VideoWriter_fourcc(*'DIVX')
#fourcc = cv2.VideoWriter_fourcc(*'DIV3')
#fourcc = cv2.VideoWriter_fourcc('F','M','P','4')
#fourcc = cv2.VideoWriter_fourcc('D','I','V','X')
#fourcc = cv2.VideoWriter_fourcc('D','I','V','3')
#fourcc = cv2.VideoWriter_fourcc('F','F','V','1')


fourcc = cv2.VideoWriter_fourcc('M','J','P','G')
    out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))

    while(cap.isOpened()):
        ret, frame = cap.read()
        if ret==True:
            frame = cv2.flip(frame,0)

            # write the flipped frame
            out.write(frame)

            cv2.imshow('frame',frame)
            if cv2.waitKey(1) & 0xFF == ord('q'):
                break
        else:
            break

    # Release everything if job is finished
    cap.release()
    out.release()
    cv2.destroyAllWindows()