Windows中的VideoCapture OpenCV 2.4.2错误

Question

I have a problem using VideoCapture class with OpenCV 2.4.2 under windows XP 32bits. It doesn't open any file or camera and fixing it's being a pain. Im using visual studio 2010 but i have also tried the code in QTcreator with the same result.

The testing code is the following:

#include "opencv/cv.h"
#include "opencv/highgui.h"
#include <iostream>
#include <string> 
#include <iomanip> 
#include <sstream> 

using namespace cv;
using namespace std;

int main()
{
    const char* videoPath = "C:/video/";
    string videoName = string(videoPath) + "avi.avi";
    VideoCapture cap(videoName);

    if(!cap.isOpened()) 
    {
        std::cout<<"Fail"<<std::endl;
        return -3;
    }
    return 0; 
}

The output is always '-3'. Qt Creator shows a warning: Error opening file (../../modules/highgui/src/cap_ffmpeg_impl.hpp:361)

I debugged it and the problem appears in the first line of:

CvCapture* cvCreateFileCapture_FFMPEG_proxy(const char * filename)
{
    CvCapture_FFMPEG_proxy* result = new CvCapture_FFMPEG_proxy;
    if( result->open( filename ))
        return result;
    delete result;
#if defined WIN32 || defined _WIN32
    return cvCreateFileCapture_VFW(filename);
#else
    return 0;
#endif
}

in the cap_ffmpeg.cpp internal file.

I have tested the same code in a mac under snow leopard and it works. No surprises here since it must be a library issue. I have opened the avi file with the same path route using the c-function cvCapture easy and fast. I got all the dlls of 'C:\\opencv\\opencv\\build\\x86\\vc10\\bin' included in mi debug file. I got the tbb.dll and all the 'C:\\opencv\\opencv\\3rdparty\\ffmpeg' content included too.

This is drving me crazy so any help would be appreciated.

Thanks in advance.

Answer 1

In my case, the same problem was resolved after deleting all opencv_***.dll files in C:\\Windows\\System32 . So, I use the dll files just through the path like "%PATH%;C: \\Program Files \\OpenCV2.4.2\\build\\x86\\vc10/bin" . Please try it.

Answer 2

I also faced with this problem and solved it by correct the path of the function:

VideoCapture cap(videoName);

If the AVI file of videoName does't exist, it will be an error:

(../../modules/highgui/src/cap_ffmpeg_impl.hpp:XXX)

where XXX represents the line number.

Answer 3

I had the same issue with the open method whilst running under Windows 8 (64bit), opencv 2.4.10. IDE is running in x86.

I found that running the application in release configuration solved the problem.

Stumbled across the answer because I had the same issue with imread. Issue is presented in the this thread. imread not working in Opencv

Answer 4

See the fix I found below, for mp4 files. I faced the same issue on Windows 7, using OpenCV 2.4.9. I am using the java wrapper for opencv.

Matthias Krings has done a lot of research for this. See this . Apparently this is an issue based on the video file type. With .avi files, it seems to work for a lot of people. Unfortunately his solution of setting OPENCV_DIR did not work for me. But his comments in the bug listing gave me a hint to fix the issue.

You have to do two things:

1. Set java.library.path to include the directory {opencv\\install\\dir}opencv-2.4.9\\build\\x86\\vc10\\bin . You can set the variable using the -D option on the java command line: java -Djava.library.path=PATH_TO_YOUR_DLL ... . Also fetch this variable from your environment, using System.getProperty(...) , and print it before calling loadLibrary() , to verify that the path setting is working.
2. And in your java class, load the ffmpeg dll using System.loadLibrary("opencv_ffmpeg249"); . The loadLibrary() function should be invoked from within a static block in java.
3. There is a file named opencv_ffmpeg249.dll in the java.library.path that we set.
4. This works on ubuntu also, for .so files.

Answer 5

在指向输入视频的正确位置后，我也遇到了同样的问题并解决了问题。