Q:

how to give different file name every time i capture video and write it to file?

I am newbee in opencv. I am working on part of the project.
In the below code, I have used VideoWriter class to store video with name MyVideo.avi as I specified in below code.
But every time i capture video it stores with same name i.e it get overridden.
So I want to name it with computer date and time.
please help me to modify this 
#include "opencv2/highgui/highgui.hpp"
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char* argv[])
{
VideoCapture cap(0); // open the video camera no. 0

if (!cap.isOpened())  // if not success, exit program
{
    cout << "ERROR: Cannot open the video file" << endl;
    return -1;
}

namedWindow("MyVideo",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"

 double dWidth = cap.get(CV_CAP_PROP_FRAME_WIDTH); //get the width of frames of the video
double dHeight = cap.get(CV_CAP_PROP_FRAME_HEIGHT); //get the height of frames of the video

cout << "Frame Size = " << dWidth << "x" << dHeight << endl;

Size frameSize(static_cast<int>(dWidth), static_cast<int>(dHeight));

 VideoWriter oVideoWriter ("D:/MyVideo.avi", CV_FOURCC('P','I','M','1'), 20, frameSize, true); //initialize the VideoWriter object 

 if ( !oVideoWriter.isOpened() ) //if not initialize the VideoWriter successfully, exit the program
{
    cout << "ERROR: Failed to write the video" << endl;
    return -1;
}

while (1)
{

    Mat frame;

    bool bSuccess = cap.read(frame); // read a new frame from video

    if (!bSuccess) //if not success, break loop
   {
         cout << "ERROR: Cannot read a frame from video file" << endl;
         break;
    }

     oVideoWriter.write(frame); //writer the frame into the file

    imshow("MyVideo", frame); //show the frame in "MyVideo" window

    if (waitKey(10) == 27) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
   {
        cout << "esc key is pressed by user" << endl;
        break; 
   }
}

return 0;

}

A:

The filename is hardcoded in your source code.
When initializing oVideoWriter object, use this code instead:
const QString filename = QDateTime::currentDateTime().toString("yyyy-MM-dd_HH.mm.ss") + ".avi";
VideoWriter oVideoWriter(filename, CV_FOURCC('P','I','M','1'), 20, frameSize, true);

This will set filename to the current date and time. Read the docs on date/time formatting.

