I don't have the proper gstreamer dll loaded for C++ opencv camera capture

Question

I have successfully capture the webcam using Python and opencv but now I am getting back into C++ and trying to do the same simple functionality.

Here's my (trimmed down) code:

#include <iostream>
#include <opencv2\opencv.hpp>
#include <opencv2\imgcodecs.hpp>
using namespace cv;
using std::cout;
using std::endl;
using std::string;
int main()
{
    Mat img;
    VideoCapture cam(0);
    if (cam.isOpened()) {
        cout << "Camera is opened." << endl;
    } else {
        cout << "Camera is NOT opened." << endl;
    }
    const string camWin{ "Rufus' Webcam" };
    namedWindow(camWin);
    while (1) {
        cam >> img;
        imshow(camWin, img);
        if (waitKey(1) == 27)
            break;
    }
    cam.release();
}

This is the error I get when I run:

attempting to open the camera using opencv. [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\videoio_registry.cpp (191) cv::`anonymous-namespace'::VideoBackendRegistry::VideoBackendRegistry VIDEOIO: Enabled backends(7, sorted by priority): FFMPEG(1000); GSTREAMER(990); INTEL_MFX(980); MSMF(970); DSHOW(960); CV_IMAGES(950); CV_MJPEG(940) [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\backend_plugin.cpp (370) cv::impl::getPluginCandidates Found 2 plugin(s) for GSTREAMER [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\backend_plugin.cpp (175) cv::impl::DynamicLib::libraryLoad load C:\\Users\\rufuss\\source\\repos\\OpenCVinCPP\\x64\\Debug\\opencv_videoio_gstreamer450_64d.dll => FAILED [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\backend_plugin.cpp (175) cv::impl::DynamicLib::libraryLoad load opencv_videoio_gstreamer450_64d.dll => FAILED [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\backend_plugin.cpp (370) cv::impl::getPluginCandidates Found 2 plugin(s) for MSMF [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\backend_plugin.cpp (175) cv::impl::DynamicLib::libraryLoad load C:\\Users\\rufuss\\source\\repos\\OpenCVinCPP\\x64\\Debug\\opencv _videoio_msmf450_64d.dll => OK [ INFO:0] global C:\\build\\master_winpack-build-win64-vc15\\opencv\\modules\\videoio\\src\\backend_plugin.cpp (236) cv::impl::PluginBackend::PluginBackend Video I/O: loaded plugin 'Microsoft Media Foundation OpenCV Video I/O plugin' Camera is opened.

(basically it doesn't find: opencv_videoio_gstreamer450_64d.dll, because it doesn't exist, so not a path problem)

I could use some help either:

1. Installing the missing dll: opencv_videoio_gstreamer450_64d.dll properly. or
2. Disabling gstreamer from the opencv search list.

Either would help me, but I'd actually like to know both techniques, for future reference.

Answer 1

You may try adding cam.open(0, CAP_DSHOW);

#include <iostream>
#include <opencv2\opencv.hpp>
#include <opencv2\imgcodecs.hpp>
using namespace cv;
using std::cout;
using std::endl;
using std::string;
int main()
{
    Mat img;
    VideoCapture cam;
    cam.open(0, CAP_DSHOW);
    if (cam.isOpened()) {
        cout << "Camera is opened." << endl;
    }
    else {
        cout << "Camera is NOT opened." << endl;
    }
    const string camWin{ "Rufus' Webcam" };
    namedWindow(camWin);
    while (1) {
        cam >> img;
        imshow(camWin, img);
        if (waitKey(1) == 27)
            break;
    }
    cam.release();
}

If you would like to learn more please see this .

Also you could do cmake -DWITH_GSTREAMER=OFF while building, to disable gstreamer. (see this )