C++ windows 多线程 互斥锁

 #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( / 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 ;
     }
     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();
     }
 }

本代码为人脸识别视频处理代码，包含两个线程，其中Show线程为opencv读取rtsp流，主线程代码自填。其中GC::Collect()为程序垃圾回收。

代码本为单线程，书写中发现VideoCapture读取视频流时存在缓存，并有缓存上限，单纯进行主线程视频处理时会因为处理时间较长发生缓存溢出问题，所以增设多线程Show()读取消耗VideoCapture缓存。

增设Show()线程时发现存在两线程同时读取缓存现象，添加互斥锁hMutex ，代码中包含互斥锁的句柄初始化以及加锁解锁代码。