VideoCapture returns empty data about mexopencv HOT 4 CLOSED

How reproducible is it? Does it happen to other videos/a camera? Please note that directly calling VideoCapture_() while keeping an instance of cv.VideoCapture in matlab would break its functionality.

from mexopencv.

The cv.VideoCapture class is just a wrapper around the MEX-function VidepCapture_, at the same time it uses the MATLAB OOP system to handle the lifetime of the underlying C++ object (delete function is called when object goes out of scope or explicitly cleared).

So if works when calling the MEX-function directly, it should also work for the class wrapper. Try to call cap.isOpened() after you open the video.

Side note: pause is sometimes required if you are opening an actual camera device, I doubt it's needed with a video file stored on disk.

from mexopencv.

I found the problem. I copied all the OpenCV DLL's into the private folder where the MEX files are. This works for most MEX files, only not for the one who dynamically loads the FFMPEG DLL, because this one try's to load the FFMPEG DLL at it's current location and that is of course not the private directory.

The fix was to add some extra lines to my startup script in Matlab:

pathval = getenv('PATH');
opencv_dllpath = fullfile(pwd, '+cv', 'private');
if( isempty(strfind(pathval, opencv_dllpath))
   setenv('PATH', [getenv('PATH') ';'  opencv_dllpath]);
end

from mexopencv.

Did you follow the steps in the README file, the bin folder containing the OpenCV DLLs must be put on the system PATH environment variable. That way dynamic loading of libraries works..

If you want to place local copies of the DLLs and skip the PATH, you must do so in both the +cv and the +cv/private folders

from mexopencv.