title: OpenCV can't find ffmpeg (?)
body: <p>I can't get OpenCV to use FFMpeg for capturing webcam or video playback. (Windows, C++)</p>
  
  <p>I downloaded <a href="https://sourceforge.net/projects/opencvlibrary/files/4.1.0/opencv-4.1.0-vc14_vc15.exe" rel="nofollow noreferrer">latest OpenCV 4.1</a> and set it up in Visual Studio. It basically compiles and runs. </p>
  
  <p>As far as I can see, the OpenCV I downloaded is build with FFMpeg (?).</p>
  
  <p>I just want to capture my webcam:</p>
  
  <pre><code>VideoCapture capture;
  
  capture.open(0);
  if (!capture.isOpened()) return;
  
  Mat frame;
  while (capture.read(frame))
  {
      if (frame.empty()) {
          cout &lt;&lt; "frame empty" &lt;&lt; endl;
      }
      imshow("capture", frame);
  }
  capture.release();
  destroyAllWindows();
  return 0;
  </code></pre>
  
  <p>the result I get is:</p>
  
  <pre><code>[ INFO:0] VIDEOIO: Enabled backends(6, sorted by priority): FFMPEG(1000); GSTREAMER(990); MSMF(980); DSHOW(970); CV_IMAGES(960); CV_MJPEG(950)
  [ INFO:0] VideoIO pluigin (GSTREAMER): glob is 'opencv_videoio_gstreamer*.dll', 1 location(s)
  [ INFO:0]     - C:\opencv4.1\build\x64\vc15\bin: 0
  [ INFO:0] Found 0 plugin(s) for GSTREAMER
  </code></pre>
  
  <p>(I don't want to use GStreamer, I want ffmpeg)</p>
  
  <p>I tried to force OpenCV to use ffmpeg with</p>
  
  <pre><code>capture.open(0 + cv::CAP_FFMPEG);
  </code></pre>
  
  <p>but then it can't open the camera device. </p>
  
  <p>What do I have to do that OpenCV finds ffmpeg?</p>