opecv VideoCapture open avi file failed

 opecv2  VideoCapture open avi file failed:

 

        VideoCapture capture;
	bool fopen = capture.open("D:\\WebNaviData\\172.18.222.2\\H264\\20160614161728466_20160614161808008.avi");
	if (fopen)
	{
		cout << "open avi" << endl;
	}
	else
	{
		cout << "open failed" << endl;
	}

	return -1;

  老是打开失败。后面查了下，是因为我在debug目录下没有放opencv_ffmpeg300.dll文件

   放入之后就OK了。