//You should include correct hpp file

include "opencv2/core/core.hpp"

include "opencv2/highgui/highgui.hpp"

include "opencv2/video/background_segm.hpp"

include "opencv2/imgproc/imgproc.hpp"

include "vector"

file

#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/video/background_segm.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "vector"

using namespace cv;
 
cv;
using namespace std;
 
std;

int main(int argc, char *argv[])
 
{
 
*argv[])

{

Mat frame;

Mat copyframe; 

Mat back;

Mat fore;

VideoCapture cap;
//open video
cap.open("test.avi");

//Background Model
BackgroundSubtractorMOG2 bg;
vector<vector<Point> > contours;
namedWindow("Input");
namedWindow("Frame");
namedWindow("Foreground");
namedWindow("Background");
for(;;)
{
    //read frame
    if(!cap.read(frame))
    {
        return 0;
    }
    imshow("Input",frame);
    //get foreground
    bg(frame,fore,0.01);
    imshow("Foreground",fore);
    //get background
    bg.getBackgroundImage(back);
    //erode image
    erode(fore,fore,Mat());
    //dilate image
    dilate(fore,fore,Mat());
    //find contours
    findContours(fore,contours,CV_RETR_EXTERNAL,CV_CHAIN_APPROX_NONE);
    //draw contours to frame
    drawContours(frame,contours,-1,Scalar(0,0,255),2);
    imshow("Frame",frame);
    imshow("Background",back);

    if(waitKey(33) >= 0)
    {
        break;
    }

}
cap.release();
return 0;
}
 
} 
Hope can help you.