Status of VideoCapture object in OpenCV

Question

I have encapsulated the OpenCV VideoCapture class into a class of my own and am trying to initialize it from a video file on disk. The .isOpened() function returns true , but the frames I read later on are empty.

• If the VideoCapture can't read frames, why is it reporting being open ?
• How can I further inspect the status of the VideoCapture object to find out why it's not reading frames?

Here is a tiny excerpt. Init() later throws an error because the frames read by camera_.read() are empty. Better scroll through to the code at the bottom, it exemplifies the problem better.

Camera::Camera(int target_width, int target_height, std::string filename)
    : target_width_(target_width),
      target_height_(target_height),
      camera_(filename)
{
    if (!camera_.isOpened()){
        cerr << "Failed to open video file" << endl;
        exit(EXIT_FAILURE);
    }
    camera_.read(frame_full_);
    if (frame_full_.empty()){
       cerr << "Failed to read from video file" << endl;
       exit(EXIT_FAILURE);
    }
    Init();
}

EDIT:

So, reading from an actual webcam works fine, it is the code above (reading from a file by filename) that returns empty frames.

EDIT2:

So—as suggested by Mhd.Tahawi—my whole problem can be summarized by the code below:

cv::VideoCapture cap("/Users/Me/Projects/whatev/some_video__640x360.avi");
cv::Mat test;

if (cap.isOpened()){
    cap.read(test);
    if (test.empty()) {
        std::cout << "BRO DO YOU EVEN CAPTURE?" << std::endl;
    }
}

Answer 1

I suspect codec problems - your code looks fine.

On a Mac, use brew install opencv --with-ffmpeg .

(But double check if you really have a the correct filepath, even though it shouldn't say that it is open). If you are on windows you need "\\" in your path.