若不更改分辨率，则只能显示一个摄像头
若更改分辨率，则读取不到图片，报错如下：
[ WARN:0] global C:projectsopencv-pythonopencvmodulesvideoiosrccap_msmf.cpp (1113) SourceReaderCB::OnReadSample videoio(MSMF): OnReadSample() is called with error status: -2147467263 [ WARN:0] global C:projectsopencv-pythonopencvmodulesvideoiosrccap_msmf.cpp (1125) SourceReaderCB::OnReadSample videoio(MSMF): async ReadSample() call is failed with error status: -2147467263 [ WARN:1] global C:projectsopencv-pythonopencvmodulesvideoiosrccap_msmf.cpp (1159) CvCapture_MSMF::grabFrame videoio(MSMF): can't grab frame. Error: -2147467263 [ WARN:1] global C:projectsopencv-pythonopencvmodulesvideoiosrccap_msmf.cpp (1159) CvCapture_MSMF::grabFrame videoio(MSMF): can't grab frame. Error: -2147483638
其他文章说是版本不兼容，修改代码如下：
cap = cv2.VideoCapture(1, cv2.CAP_DSHOW)
问题解决
