记录使用《MFC中如何利用ffmpeg和SDL2.0多线程多窗口播放摄像头的视频》这篇文章的代码，遇到的一些问题

最近在研究如如何播放多个摄像头数据，在查找资料的过程中发现了这篇文章《MFC中如何利用ffmpeg和SDL2.0多线程多窗口播放摄像头的视频》，使用这篇文章的代码。博主对每个部分介绍还是比较清楚的，中间省略了一些代码，还得需要自己调整。本文主要记录在调用过程中遇到的一些问题。

这个是我调用的地方

void CMultithreadedMultiWindowCamerasDlg::OnBnClickedButton1()
{
	//1、获取设备列表
	HRESULT hrrst;
	GUID guid = CLSID_VideoInputDeviceCategory;
	std::vector<TDeviceInfo> videoDeviceVec;
	hrrst = DsGetAudioVideoInputDevices(videoDeviceVec, guid);
	//2.打开设备（这里我有两个摄像头，所以打开了两个）
	CWnd* pWnd1 = this->GetDlgItem(IDC_STATIC1);//IDC_PIC_1就是图像控件的ID
	HWND handle1 = pWnd1->GetSafeHwnd();      //获取图像控件的句柄

	CWnd* pWnd2 = this->GetDlgItem(IDC_STATIC2);//IDC_PIC_1就是图像控件的ID
	HWND handle2 = pWnd2->GetSafeHwnd();      //获取图像控件的句柄

	Video video1;
	videoDeviceVec[0].Index = 0;
	video1.mainHandle = handle1;//screen;
	video1.mainWindow = new Window(0, 0);
	video1.Init(videoDeviceVec[0], videoDeviceVec[0].Params[1], 0);
	video1.mainWindow->Init(handle1, video1.width, video1.height);
	SDL_Thread *video_tid1 = SDL_CreateThread(SDL_Play_Thread, "sdl", (void *)&video1);

	Video video2;
	videoDeviceVec[1].Index = 0;
	video2.mainHandle = handle2;//screen;
	video2.mainWindow = new Window(0, 0);
	video2.Init(videoDeviceVec[1], videoDeviceVec[1].Params[3], 1);
	video2.mainWindow->Init(handle2, video2.width, video2.height);
	SDL_Thread *video_tid2 = SDL_CreateThread(SDL_Play_Thread, "sdl", (void *)&video2);
}

没有播放摄像视频数据，调试发现这个接口Play()的大的while循环没有被执行

int Video::Play() {
    //.....此处省略了一些代码
	while (！isStop) {
		if (isPause) {
			SDL_Delay(20);
			continue;
		}
		//av_init_packet(packet);
		bool getData = true;
		while (1) {
			if (av_read_frame(pFormatCtx, packet) < 0) {
				getData = false;
				break;
			}
			if (packet->stream_index == videoIndex) {
				getData = true;
				break;
			}
		}
		if (!getData) {
			break;
		}
     //....此处省略了一些代码
	}
	sws_freeContext(img_convert_ctx);
	SDL_Quit();
	av_free(out_buffer);
	av_free(pFrameYUV);
	return 0;
}

而Play()是在SDL线程中被调用 的

//线程函数
static int SDL_Play_Thread(void* param) {
	Video* video = (Video*)param;
	video->Play();
	video->AddList(video->listHandle);
	return 0;
}

isStop的莫名其妙的改变了

在SDL线程中赋值的时候，isStop的变量没有改变

进到Play()的时候，isStop的值变成了true(204)

查找资料这是未初始化的状态。

找了半天，猜想void CMultithreadedMultiWindowCamerasDlg::OnBnClickedButton1()这个接口已经执行结束，相应的video1这个对象也被释放掉，但是SDL_Play_Thread这个线程函数还在执行，它所访问的isStop变量是处于未初始化状态。

void CMultithreadedMultiWindowCamerasDlg::OnBnClickedButton1()
{
	//.........
	SDL_Thread *video_tid1 = SDL_CreateThread(SDL_Play_Thread, "sdl", (void *)&video1);
	
	//.........
}

于是在线程函数中修改如下，问题解决

//线程函数
 int SDL_Play_Thread(void* param) {
	 Video* video = new Video();
	 //video=(Video*)param;
	 //++++++++++++++++++++++++++++++++++++++++++++++++
	 video->width = ((Video*)param)->width;
	 video->height = ((Video*)param)->height;
	 video->listHandle = ((Video*)param)->listHandle;
	 video->mainHandle = ((Video*)param)->mainHandle;
	 video->mainWindow = ((Video*)param)->mainWindow;
	 video->listWindow = ((Video*)param)->listWindow;
	 video->pCodec = ((Video*)param)->pCodec;
	 video->pCodecCtx = ((Video*)param)->pCodecCtx;
	 video->pFormatCtx = ((Video*)param)->pFormatCtx;
	 video->thread = ((Video*)param)->thread;
	 video->videoIndex = ((Video*)param)->videoIndex;
	 video->isPause = ((Video*)param)->isPause;
	 video->isStopp = ((Video*)param)->isStopp;
	 //++++++++++++++++++++++++++++++++++++++++++++++++++
	 video->Play();
	 video->AddList(video->listHandle);
	 delete video;
	 return 0;
}

参考文章：
bool类型未初始化的产生的奇怪现象
https://blog.youkuaiyun.com/lanlongtu/article/details/102328025?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-2.control&dist_request_id=1328689.10311.16165855629799887&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-2.control