Cannot open camera with OpenCV in Linux

Question

I am using OpenCV 2.4.3 on linux now. And in my /dev/ there is a device called video0 that is working fine with cheese.

Currently I am using the following code to try to access the camera. This code is written in qtcreator and compiled with qmake to include the necessary library. As for the OpenCV library, I downloaded the source code and compiled it according to the instruction on the website on my machine.

++main.cpp:

#include <iostream>
#include <opencv2/opencv.hpp>
#include <cstdlib>

int main(int argc, char** argv) {
    int cameraNumber = 0;
    if (argc>1)
        cameraNumber = atoi(argv[1]);
    cv::VideoCapture camera;
    camera.open(cameraNumber);
    if(!camera.isOpened()) {
        std::cerr<<"Error opening camera"<<std::endl;
        exit(1);
    }
    camera.set(CV_CAP_PROP_FRAME_WIDTH,640);
    camera.set(CV_CAP_PROP_FRAME_HEIGHT,480);

    while(true) {
        cv::Mat cameraFrame;
        camera>>cameraFrame;
        if (cameraFrame.empty()){
            std::cerr<<"No frame read from camera"<<std::endl;
            exit(1);
        }
        imshow("Camera",cameraFrame);

        char keypress = cv::waitKey(20);
        if (keypress==27) {
            break;
        }
    }
    return 0;
}

---

++test.pro

TEMPLATE = app
CONFIG += console
CONFIG -= app_bundle
CONFIG -= qt

SOURCES += main.cpp

win32:CONFIG(release, debug|release): LIBS += -L$$PWD/../../../../opt/OpenCV-2.4.3/lib/release/ -lopencv_core
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/../../../../opt/OpenCV-2.4.3/lib/debug/ -lopencv_core
else:unix: LIBS += -L$$PWD/../../../../opt/OpenCV-2.4.3/lib/ -lopencv_core

win32:CONFIG(release, debug|release): LIBS += -L$$PWD/../../../../opt/OpenCV-2.4.3/lib/release/ -lopencv_highgui
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/../../../../opt/OpenCV-2.4.3/lib/debug/ -lopencv_highgui
else:unix: LIBS += -L$$PWD/../../../../opt/OpenCV-2.4.3/lib/ -lopencv_highgui

INCLUDEPATH += $$PWD/../../../../opt/OpenCV-2.4.3/include
DEPENDPATH += $$PWD/../../../../opt/OpenCV-2.4.3/include

However, when running the program it will output Error opening camera and exit, which means the camera is not opened successfully. I have been googled a while and didn't find any possible solutions to solve this issue. Could some one give me some advice on how to solve this problem? Thanks!

Answer 1

Perhaps you are missing some addition libraries that are required for linux.

According to OpenCV install guide, Extra Prerequisites , when using OpenCV on linux, you need to install these libraries: ffmpeg, libgstreamer, libv4l, libxine, unicap, libdc1394 2.x.

On Ubuntu 12.04 , installing the following packages worked for me (*sudo apt-get install __ *):

• python-opencv
• libhighgui2.3
• libhighgui-dev
• ffmpeg
• libgstreamer0.10-0
• libv4l-0
• libv4l-dev
• libxine2
• libunicap2
• libdc1394-22

Good Luck!