C++ windows 多線程 互斥鎖

#include <opencv2/core/version.hpp>
#include <opencv2/calib3d/calib3d.hpp>
#include <opencv2/opencv.hpp>

using namespace System::Runtime::InteropServices;
using namespace System::IO;
using namespace System::Data;
using namespace System::Drawing;
using namespace System::Drawing::Imaging;
using namespace System::Runtime::Serialization::Formatters::Binary;
using namespace System::Windows::Forms;
using namespace System::Threading;

using namespace FRS;
using namespace FRS::Util;
using namespace DataAngine;

HANDLE hMutex = CreateMutex(NULL,FALSE,NULL);


cv::VideoCapture *cap;
void Show(){
    while (true){
        cv::Mat frame;
        WaitForSingleObject(hMutex, INFINITE);
        cap>>frame;
        ReleaseMutex(hMutex);
        imshow("video", frame);
        cv::waitKey(1000 / cap->get(CV_CAP_PROP_FPS));
    }
}
int main()
{
    FeatureData ^fa = gcnew FeatureData();

    //cap.open(0);
    cap = new cv::VideoCapture();
    cap->open("rtsp://admin:admin12345@172.18.132.234:554");

    if (!cap->isOpened())
    {
        std::cout << "open rtsp error" << std::endl;
        return 0;
    }
    Thread ^showThread = gcnew Thread(gcnew ThreadStart(Show));
    showThread->Start();
    
    bool stop = true;
    while (stop)
    {
        cv::Mat frame;
        WaitForSingleObject(hMutex, INFINITE);
        cap>>frame;
        ReleaseMutex(hMutex);
        if (frame.empty()) continue;
        System::GC::Collect();
        
        Thread::Sleep(100);
    }
}

本代碼為人臉識別視頻處理代碼，包含兩個線程，其中Show線程為opencv讀取rtsp流，主線程代碼自填。其中GC::Collect()為程序垃圾回收。

代碼本為單線程，書寫中發現VideoCapture讀取視頻流時存在緩存，並有緩存上限，單純進行主線程視頻處理時會因為處理時間較長發生緩存溢出問題，所以增設多線程Show()讀取消耗VideoCapture緩存。

增設Show()線程時發現存在兩線程同時讀取緩存現象，添加互斥鎖hMutex ，代碼中包含互斥鎖的句柄初始化以及加鎖解鎖代碼。