cv2.videocapture()失败，无法读取视频

原因：缺少ffmpeg的支持

解决：

pip install opencv-python
pip install opencv-contrib-python

 如果实现安装的版本不一致会出现问题，如

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib64/python2.7/site-packages/cv2/__init__.py", line 9, in <module>
    from .cv2 import *
ImportError: libSM.so.6: cannot open shared object file: No such file or directory

解决办法，需要安装匹配的版本

pip install opencv-python==3.2.0
pip install opencv-contrib-python==3.2.0.8