dirctshow编程实现视频采集

DirectShow是一种Microsoft Windows多媒体架构，它提供了一种基于组件的架构，用于创建、渲染和处理多媒体流。DirectShow提供了一种灵活的方式来实现视频采集，下面是一个简单的DirectShow程序，用于视频采集：

1. 引入头文件和库文件

#include <dshow.h>
#pragma comment(lib, "strmiids.lib")

2. 初始化COM库

CoInitialize(NULL);

3. 创建GraphBuilder对象

IGraphBuilder* pGraphBuilder = NULL;
CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,
    IID_IGraphBuilder, (void**)&pGraphBuilder);

4. 创建CaptureGraphBuilder2对象

ICaptureGraphBuilder2* pCaptureGraphBuilder2 = NULL;
CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, CLSCTX_INPROC_SERVER,
    IID_ICaptureGraphBuilder2, (void**)&pCaptureGraphBuilder2);

5. 设置设备过滤器

IBaseFilter* pDeviceFilter = NULL;
pCaptureGraphBuilder2->FindInterface(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,
    NULL, NULL, IID_IBaseFilter, (void**)&pDeviceFilter);

6. 创建Render过滤器

IBaseFilter* pRenderFilter = NULL;
CoCreateInstance(CLSID_VideoRenderer, NULL, CLSCTX_INPROC_SERVER,
    IID_IBaseFilter, (void**)&pRenderFilter);

7. 添加过滤器到GraphBuilder中

pGraphBuilder->AddFilter(pDeviceFilter, L"Device Filter");
pGraphBuilder->AddFilter(pRenderFilter, L"Render Filter");

8. 连接过滤器

pGraphBuilder->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,
    pDeviceFilter, NULL, pRenderFilter);

9. 显示预览

IMediaControl* pMediaControl = NULL;
pGraphBuilder->QueryInterface(IID_IMediaControl, (void**)&pMediaControl);
pMediaControl->Run();

10. 释放资源

pMediaControl->Stop();
pMediaControl->Release();
pRenderFilter->Release();
pDeviceFilter->Release();
pCaptureGraphBuilder2->Release();
pGraphBuilder->Release();
CoUninitialize();

上述程序中，我们使用了CaptureGraphBuilder2对象来查找并设置设备过滤器，并使用GraphBuilder对象管理整个流程。最后，我们通过MediaControl对象启动预览，并释放所有资源。