Question

I’m trying to open a mpg-File using emguCV. I use the following code:

    if (instance == null)
    {
        lock (m_lock)
        {
            try
            {
                instance = new Capture(0);  // capture from camera works fine if a camera is connected
            }
            catch (NullReferenceException)
            {
                String sFileName = @"C:\tmp\MarkerMovie.mpg";


                try
                {
                    if (File.Exists(sFileName))
                    {
                        instance = new Capture(sFileName);  // here the exception is thrown
                    }
                    else
                    {
                        MessageBox.Show("No Camera and no Video-File found");
                    }
                }
                catch (NullReferenceException)
                {
                    MessageBox.Show("Couldn't open Video: "+sFileName);
                }
            }
        }
    }

If a webcam is connected everything works fine, but when I unplug the webcam the line instance = new Capture(sFileName); throws a NullReferenceException:

Message = “Unable to create capture from C:\tmp\MarkerMovie.mpg”

I debugged and found the reason is in the constructor of capture. The following command always returns a Null-Pointer:

_ptr = CvInvoke.cvCreateFileCapture(fileName);

I could open the same video using C++ using this code:

cap = cvCaptureFromFile("C:\\tmp\\MarkerMovie.mpg");

I’m new to openCV, so I’m not sure which information you need to help me. I installed emguCV yesterday from http://sourceforge.net/projects/emgucv/ on a Windows XP computer. The installer-version is x86_2.3.0.1416. I included opencv_core231.dll, opencv_highgui231.dll and opencv_imgproc231.dll to my project.

Does somebody know how I can make this code working?
Let me know if you need more information.

Thanks.

Answer 1

I had the same problem and adding the opencv_ffmpeg.dll to the project seems to solve it. (Found in the bin directory in the Emgu CV directory) I have tried it on the project that you posted and it seems to be working too. Hope it helps.