My exe keeps flashing back!

[ZBF]

I have no idea about this.My code has no errors,and I try to install Xvid,but nothing is useful.It keeps flashing back

Here is my code

#include <iostream>
#include <opencv2/opencv.hpp>
#include<thread>
#include <conio.h>
#include <windows.h>
#include <time.h>
using namespace std;

std::mutex g_mutex;
int width = 640;
int heigth = 480;
int FPS_SET = 30;
int key = 0;
std::queue<cv::Mat> frames;

void getframe()
{
	cout << "正在打开摄像头" << endl;

	cv::VideoCapture cap;
	cap.open(0);
	cap.set(cv::CAP_PROP_FRAME_WIDTH, width);
	cap.set(cv::CAP_PROP_FRAME_HEIGHT, heigth);
	cap.set(cv::CAP_PROP_FOURCC, cv::VideoWriter::fourcc('M', 'J', 'P', 'G'));
	cap.set(cv::CAP_PROP_FPS, FPS_SET);
	if (!cap.isOpened())
	{
		cout << "打开失败" << endl;
		return;
	}

	cout << "打开成功" << endl;


	int delay = 1000 / FPS_SET;
	while (key != 27)
	{
		while (frames.size() > 3) Sleep(delay);
		Sleep(delay);
		cv::Mat frame2;
		cap >> frame2;
		g_mutex.lock();
		frames.push(frame2);
		g_mutex.unlock();

	}

	cout << "正在解除摄像头占用" << endl;
	cap.release();
	cout << "成功解除摄像头占用" << endl;
}

void showframe()
{
	int font_face = cv::FONT_HERSHEY_COMPLEX;
	double font_scale = 1;
	int thickness = 2;
	int baseline;
	cv::Point origin;
	origin.x = 10;
	origin.y = 30;

	int FPS = 0;
	double time = 0;
	LARGE_INTEGER nFreq;
	LARGE_INTEGER nBeginTime;
	LARGE_INTEGER nEndTime;
	QueryPerformanceFrequency(&nFreq);


	cv::Mat frame;
	cv::namedWindow("Tennis");
	do
	{
		QueryPerformanceCounter(&nBeginTime);

		if (!frames.empty())
		{
			g_mutex.lock();
			frame = frames.front();
			frames.pop();
			g_mutex.unlock();

			string s = "FPS:" + to_string(FPS);
			cv::putText(frame, s.c_str(), origin, font_face, font_scale, cv::Scalar(0, 255, 255), thickness, 8, 0);
		}
		if (!frame.empty())
			cv::imshow("Tennis", frame);
		cv::waitKey(1000 / FPS_SET);
		QueryPerformanceCounter(&nEndTime);
		time = (double)(nEndTime.QuadPart - nBeginTime.QuadPart) / (double)nFreq.QuadPart;
		FPS = 1 / time;

	} while (key != 27);
	cv::destroyWindow("Tennis");
}

int main()
{
	thread t1(getframe);
	t1.detach();
	thread t2(showframe);
	t2.detach();

	while (1)
	{
		Sleep(500);
		if (_kbhit())
			break;
	};
	key = 27;
	Sleep(1000);
	return 0;
}

There we go…