Opencv implements reading camera and video data

In fact, once the camera's video image is read at one speed, it is ready for all sorts of processing.

Then the main class used for obtaining is VideoCapture, and one demo is as follows:

// If there is an external camera, then ID for 0 Built-in for 1 , or use 0 You can represent the built-in camera  
  cv::VideoCapture cap(0);  
  // Determine if the camera is on  
  if(!cap.isOpened())  
  {  
    return -1;  
  }  
 
  cv::Mat myframe;  
  cv::Mat edges;  
 
  bool stop = false;  
  while(!stop)  
  {  
    // Get the current frame  
    cap>>myframe; 
    // Convert to grayscale   
    cv::cvtColor(myframe, edges, CV_BGR2GRAY); 
    // Gaussian filter   
    cv::GaussianBlur(edges, edges, cv::Size(7,7), 1.5, 1.5); 
    //Canny Operator detection edge   
    cv::Canny(edges, edges, 0, 30, 3); 
    // According to the edge   
    cv::imshow("current frame",edges);  
    if(cv::waitKey(30) >=0)  
      stop = true;  
  }  
  cv::waitKey(0); 

Similarly, if you want to read a video file, the video file can be regarded as a series of video frames, and when the display time is set to 1 set delay, it can be displayed at 1 set speed. One demo is as follows:

// 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; 
 
// Used to set the moving position of the frame.  
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();