cv::VideoCapture works for webcams but not IP cameras?

Question

It had to happen, I'm stuck in the last phase of my project, when I want to use my code which works like a charm on my webcam, on an IP camera. The URL works perfectly in my browser, but nothing comes out with OpenCV... Here is my code:

#include <opencv/highgui.h>

using namespace cv;

int main(int argc, char *argv[])
{
    Mat frame;
    namedWindow("video", 1);
    VideoCapture cap("http://192.168.1.99:99/videostream.cgi?resolution=32&rate=0&user=admin&pwd=password&.mjpg");
    while ( cap.isOpened() )
    {
        cap >> frame;
        if(frame.empty()) break;

        imshow("video", frame);
        if(waitKey(30) >= 0) break;
    }

    return 0;
}

And the compiler settings :

//Added to the .pro file of QtCreator
INCLUDEPATH += C:\\OpenCV243\\release\\include
LIBS += -LC:\\OpenCV243\\release\\lib \
    -lopencv_core243.dll \
    -lopencv_highgui243.dll

I've tested opening a .avi file with the same code and it works... But a public IP camera URL like http://66.184.211.231/mjpg/video.mjpg doesn't ! What's the matter then ?

Removed by edit: I had considered FFMPEG to be an issue, but v2.4.3. has built-in FFMPEG support and .avi files work although I don't have any FFMPEG library installed (care to explain?)

Thanks in advance,

Regards, Mister Mystère

Answer 1

Solved it by copying opencv_ffmpeg.dll from the build\x86\mingw\bin folder of the sources and pasting it next to built DLLs (bin folder accessible through PATH): I have no idea why, but the opencv_ffmpeg_64.dll had been produced instead.

Answer 2

Since you can connect and grab frames from a web camera I think that your library is set up correctly and you should be able to connect to IP cameras. I believe that the issue is with the supplied URL address of the camera.

Try logging into the camera and disable its password protection. Remove login and password fields from the URL, so it'll be something like "http://192.168.1.99:99/videostream.cgi?resolution=32&.mjpg". Also, you can log into the camera and check it's resolution. I noticed you have resolution=32 but I think it should be something like resolution=704x480.

Hope this helps.