the problem of loading mov file in opencv 4

edit

I am trying to load a video file, a.mov and get some statistics of this video file. a.mov can be viewed on the windows, in other words, it is not empty. But why the output is all 0.0 the code is

cap = cv.VideoCapture('C:\\Users\\dataset\\latest\\a.mov') 
print ("Video Properties:")
print("\t Framerate:",cap.get(cv.CAP_PROP_FPS))
print("\t Width: ", cap.get(cv.CAP_PROP_FRAME_WIDTH))

the output is

Framerate: 0.0
     Width:  0.0**