在OpenCV中显示来自网络摄像头的视频

Question

I have installed VS2008 and am able to run the demo codes "camshiftdemo and lkdemo " which comes in the opencv library. With this done, now I am trying to run some simple codes from the internet to get acquainted with the OpenCV. I am just trying to display video from webcam and I am getting the following error..

Error I am getting is :

Unhandled exception at 0x5e7e3d10 (highgui200.dll) in opencv.exe: 0xC0000005: Access violation reading location 0x719b3856.

The code I am trying to run is :

#include <cv.h>
#include <highgui.h>
void main(int argc,char *argv[])
{
    int c;
    IplImage* color_img;
    CvCapture* cv_cap = cvCaptureFromCAM(-1); // -1 = only one cam or doesn't matter
    cvNamedWindow("Video",1); // create window
    for(;;) {
        color_img = cvQueryFrame(cv_cap); // get frame
        if(color_img != 0)
            cvShowImage("Video", color_img); // show frame
        c = cvWaitKey(10); // wait 10 ms or for key stroke
        if(c == 27)
            break; // if ESC, break and quit
    }
    /* clean up */
    cvReleaseCapture( &cv_cap );
    cvDestroyWindow("Video");
}

Any help in this will be greatly appreciated.

Answer 1

The following code compiles and works for me in VS2008 using OpenCV 2.1

#include <cv.h>
#include <highgui.h>
void main(int argc,char *argv[])
{
    int c;
    IplImage* color_img;
    CvCapture* cv_cap = cvCaptureFromCAM(0);
    cvNamedWindow("Video",0); // create window
    for(;;) {
        color_img = cvQueryFrame(cv_cap); // get frame
        if(color_img != 0)
            cvShowImage("Video", color_img); // show frame
        c = cvWaitKey(10); // wait 10 ms or for key stroke
        if(c == 27)
            break; // if ESC, break and quit
    }
    /* clean up */
    cvReleaseCapture( &cv_cap );
    cvDestroyWindow("Video");
}

Answer 2

I think you must delete the "cvReleaseCapture( &cv_cap );" sentence. I tried it. It can be work. Somehow, when you hit the ESC button, the capture is being released. It's worth to try.