OpenCV external USB camera method

Recently, we need to use OpenCV computer vision library to read, display and save videos. Since I used the laptop directly before, this time I connected USB camera to the desktop, so there was a big problem. It always showed the memory problem. Google and baidu spent most of the day summarizing various Suggestions, and finally solved the problem.

Reasons for the problem:

1. It takes time to initialize the camera. Before entering the loop, waitKey(2000), or it will flash back;
2. There are decoding problems in the camera video.

//-------------------------------------- [Procedure Description] -------------------------------------------
//  Procedure Description: OpenCV Introduction to Computer vision library 
//  Program description: Desktop utilization OpenCV external USB The camera, read in the video and display it 
//  Operating system for development and test:  Windows 7 64bit
//  Development test use IDE Version: Visual Studio 2010
//  Development test use OpenCV Version:  2.4.9
// 2017 years 10 month  Created by @Fireman1994
//------------------------------------------------------------------------------------------------
 
#include"cv.h"
#include"highgui.h"
#include"iostream"
using namespace std;
 
int main(int argc,char* argv[])
{
 CvCapture* cap;
 cap=cvCaptureFromCAM(0);
 if(!cap)
 {
 cout<<"create camera capture error"<<endl;
 system("pause");
 exit(-1);
 }
 cvNamedWindow("img",1);
 IplImage* img;
 // Wait before entering the loop 1 A period of time to initialize the camera, otherwise the initialization is not complete, will directly flash out of the program 
 cvWaitKey(2000);
 while(1)
 {
 img=cvQueryFrame(cap);// Read in the video decode 
 if(!img)
 break;
 
 cvShowImage("img",img);
 cvWaitKey(3);
 }
 cvReleaseCapture(&cap);
 cvDestroyAllWindows();
 cvReleaseImage(&img);
 return 0;
}