# Revision history [back]

### better ways to re-initialize webcam via VideoCapture?

I'm considering a condition: if my computer is running but the USB of a webcam is accidentally unplugged. I want to write something to make the webcam can re-initialize.

int main()
{
VideoCapture video(0);
Mat frame;
while (true) {
if(video.isOpened()&&video.grab())
{
video>>frame;
if(frame.cols>0)
imshow("show video",frame);
waitKey(2);
}
else {
video.release();
cout<<"wait key input"<<endl;
char temp[1]; //get a key input
cin>>temp;
if(temp[0]!=NULL)
{
VideoCapture video_temp(0);
video=video_temp;
}
}
}
}

1. not sure but it seems video.isOpened() is not always return false even if the USB webcam is not available any more after the webcam first be launched so I may need a video.grab() to do some double check.

2. in Linux the system can immediately detect the disconnect of webcam. However, in windows system, it takes a while ( about 30 seconds ) to find out that the webcam is disconnected.

is there any better way to make the webcam re-initialize in the program?