Problem with Camera Capturing

edit

I've got two ways to capture a camera. 1.using the functions in the opencv

 #include < opencv\cv.h
 #include < opencv\highgui.h 
 #include < iostream 
 using namespace std;
 using namespace cv;
 int main()
 {
     char c;
     CvCapture* capture = cvCreateCameraCapture(0);   //0 is the external camera ID，1 is the internal camera ID of my laptop.
     IplImage* src;
     for (;;)
    {
        src = cvQueryFrame(capture);         
        cvShowImage("Input", src);
        c = waitKey(10);
        if (c == 27) break;
    } 
   cvReleaseCapture(&capture);
   return 0;
 }
2.using the functions in the ***opencv2***
 #include < opencv2\core\core.hpp
 #include < opencv2\highgui\highgui.hpp 
 #include < iostream 
 using namespace cv;
 using namespace std;
 int main()
 {
     char c;
     VideoCapture inputVideo(0);    //0为外部摄像头的ID，1为笔记本内置摄像头的ID
     Mat src;
     for(;;)
     {
        inputVideo >> src;
        imshow("input",src);
        c = waitKey(10);
        if (c == 27) break;
     }
   return 0;
 }

By using the method 1, the program can read both the external and the internal camera's data;but the program can only read the internal camera's data with method 2. I don't know why method 1 and method 2 so different.
What should I do if I want to get the data of the external camera with method 2?
// my operation system is Window8.1, the version of my OPENCV is 2.4.8, the version of my Visual Studio is 2013. I need your help.