//如果有外接摄像头，则ID为0，内置为1，否则用0就可以表示内置摄像头 
  cv::VideoCapture cap(0);  
  //判断摄像头是否打开 
  if(!cap.isOpened())  
  {  
    return -1;  
  }  
 
  cv::Mat myframe;  
  cv::Mat edges;  
 
  bool stop = false;  
  while(!stop)  
  {  
    //获取当前帧 
    cap>>myframe; 
    //转化为灰度图  
    cv::cvtColor(myframe, edges, CV_BGR2GRAY); 
    //高斯滤波器  
    cv::GaussianBlur(edges, edges, cv::Size(7,7), 1.5, 1.5); 
    //Canny算子检测边缘  
    cv::Canny(edges, edges, 0, 30, 3); 
    //显示边缘  
    cv::imshow("current frame",edges);  
    if(cv::waitKey(30) >=0)  
      stop = true;  
  }  
  cv::waitKey(0); 

// Open the video file 
  cv::VideoCapture capture("../images/bike.avi"); 
// check if video successfully opened 
if (!capture.isOpened()) 
return 1; 
 
// Get the frame rate 
double rate= capture.get(CV_CAP_PROP_FPS); 
 
bool stop(false); 
cv::Mat frame; // current video frame 
cv::namedWindow("Extracted Frame"); 
 
// Delay between each frame 
// corresponds to video frame rate 
int delay= 1000/rate; 
 
//用于设置帧的移动位置。 
input_video.set(CV_CAP_PROP_POS_FRAMES,100); 
// for all frames in video 
while (!stop) { 
 
// read next frame if any 
if (!capture.read(frame)) 
break; 
 
 cv::imshow("Extracted Frame",frame); 
 
// introduce a delay 
// or press key to stop 
if (cv::waitKey(delay)>=0) 
 
stop= true; 
} 
 
// Close the video file 
capture.release(); 
 
cv::waitKey();