无法用Python和OpenCV显示来自Youtube的视频

Question

我尝试使用python3.5、opencv3.4.3和pafy0.5.4从Youtube上获取视频。问题是cv2.VideoCapture(video_from_url)看不到来自url的视频。我以前也看过this主题。下面的代码可以很好地工作，如果video_from_url变量被替换为本地PC上的视频路径

import pafy
import cv2

url = 'https://www.youtube.com/watch?v=iCSd0slqzcQ&start_radio=1&list=RDiCSd0slqzcQ'

video_pafy = pafy.new(url)

video_from_url = video_pafy.getbest().url

cap = cv2.VideoCapture(video_from_url)

while True:

  ret, frame = cap.read()
  print(ret) # False

  """
  Further video processing
  """