I'm using playingvideofromfile line for line, but using the full path of the file.
still get the following error: OpenCV(3.4.1) C:\bld\opencv_1520732670222\work\opencv-3.4.1\modules\imgproc\src\color.cpp:11147: error: (-215) scn == 3 || scn == 4 in function cv::cvtColor