Using capVideo.read(img) VS capvideo >> img

edit

I'm trying to display a live stream video of an IP camera in my raspberry Pi. What I want to know is the difference of using capVideo.read(img) instead capVideo >> img. My program is in C++.

using namespace cv;
using namespace std;

int main(){
    Mat frame;
    VideoCapture cap("rtsp://ipofmycamera/11");
    while(cap.isOpened()){

        cap >> frame; // cap.read(frame)
        if(frame.empty()) {
            cout << "no frame" << endl;
            break;
        }
        imshow("video", frame);
        if(waitKey(30) >= 0) break;

    }

}