Low Fps on face tracking C++ - c++

Question

I have written this code to track a person's face but however, I'm getting very low fps. When I only do video my fps is a lot higher.
I have tried changing the resolution but that did not work.
#include "opencv2/core.hpp"
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
#include <opencv2/objdetect.hpp>
#include <opencv2/imgproc.hpp>
using namespace cv;
using namespace std;
int main(int argv, char** argc)
{
CascadeClassifier faceCascade;
faceCascade.load("C:\\Users\\farha\\OneDrive\\Desktop\\OpenCV4\\OpenCv\\install\\etc\\haarcascades\\haarcascade_frontalface_alt_tree.xml");
Mat frame;
Mat frameGray;
VideoCapture cap(0);
while (1)
{
cap >> frame;
cvtColor(frame, frameGray, COLOR_RGB2GRAY);
vector<Rect> faces;
faceCascade.detectMultiScale(frame, faces);
for (int i = 0; i < faces.size(); i++)
{
//int x1 = faces[i].x;
//int y1 = faces[i].y;
Point pt1(faces[i].x, faces[i].y);
Point pt2(faces[i].x + faces[i].width, faces[i].height + faces[i].y);//, (faces[i].y, faces[i].width)
rectangle(frame, pt1, pt2, Scalar(0, 0, 255), 2, 8, 0);
}
waitKey(1);
imshow("Window", frame);
}
return 0;
}