对于小摄像头的驱动有几种方法,通过使用DirectShow来驱动摄像头灵活性比较好,有简单的方法也有比较复杂但更有效的方法,本文只介绍简单方法,希望与大家交流!
用DirectShow来使用摄像头,一般要求摄像头的驱动是WDM格式的,当然,一些比较老的驱动格式DirectShow也可支持。 DirectShow通过图形过滤管理器(Filter Graph Manager)来与上层应用程序和下层的驱动进行联系。DirectShow通过一种叫作捕获过滤器(Capture Filter)的东东来支持对摄像头的捕获,一个捕获过滤器有多个插口(pin),其中的预览(preview)插口可用来进行显示祯图象。
DirectShow通过几个COM接口来对视频捕获的全过程进行控制,其中IGraphBuilder 用于建立过滤器,ICaptureGraphBuilder2用于与下层的驱动程序建立联 系,IVideoWindow,IMediaControl,IMediaEventEx分别对整个过程的视频窗口,播放过程和事件响应进行控制,
下面是例程:
- CComQIPtr m_pVW;
- CComQIPtr m_pMC;
- CComQIPtr m_pME;
- CComPtr m_pGraph;
- CComPtr m_pCapture;
- DWORD m_dwGraphRegister;
- bool bInit(HWND hWnd)
- {
- HRESULT hr;
-
- hr=CoCreateInstance (CLSID_FilterGraph, NULL, CLSCTX_INPROC
- ,IID_IGraphBuilder, (void **) &m_pGraph);
- if (FAILED(hr))
- return false;
- hr=CoCreateInstance (CLSID_CaptureGraphBuilder2 , NULL, CLSCTX_INPROC,
- IID_ICaptureGraphBuilder2, (void **) &m_pCapture);
- if (FAILED(hr))
- return false;
- m_pMC=m_pGraph;
- m_pVW=m_pGraph;
- m_pME=m_pGraph;
-
- m_pME->SetNotifyWindow((OAHWND)(m_hWnd=hWnd), WM_GRAPHNOTIFY, 0);
-
-
- m_pCapture->SetFiltergraph(m_pGraph);
-
-
- CComPtr pCde=NULL;
- CComPtr pEm=NULL;
- hr=CoCreateInstance (CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC,
- IID_ICreateDevEnum, (void **) &pCde);
- if (FAILED(hr))
- return false;
- pCde->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEm, 0);
- if(pEm==NULL)
- return false;
- CComPtr pM=NULL;
- ULONG cFetched;
- CComPtr pBf=NULL;
- if(pEm->Next(1,&pM,&cFetched)==S_OK)
- {
- pM->BindToObject(0,0,IID_IBaseFilter, (void**)&pBf);
- pM.Release();
- }
- else
- {
- return false;
- }
-
-
- hr = m_pGraph->AddFilter(pBf, L"Video Capture");
- if (FAILED(hr))
- return false;
-
- hr=m_pCapture->RenderStream(&PIN_CATEGORY_PREVIEW,&MEDIATYPE_Video,pBf,NULL,NULL);
- if (FAILED(hr))
- return false;
- pBf.Release();
-
-
- hr=m_pVW->put_Owner((OAHWND)hWnd);
- if (FAILED(hr))
- return false;
-
-
- m_pVW->put_WindowStyle(WS_CHILD | WS_CLIPCHILDREN);
- if (FAILED(hr))
- return false;
-
-
- CRect rectClient;
- GetClientRect(hWnd,rectClient);
- m_pVW->SetWindowPosition(0, 0, 320, 240);
-
-
- hr=m_pVW->put_Visible(OATRUE);
- if (FAILED(hr))
- return false;
-
- CComPtr pROT;
-
- GetRunningObjectTable(0,&pROT);
-
- WCHAR c[128];
- wsprintfW(c, L"FilterGraph %08x pid %08x/0", (DWORD_PTR)m_pGraph.p
- , GetCurrentProcessId());
- hr = CreateItemMoniker(L"!",c,&pM);
- if (FAILED(hr))
- return false;
- hr = pROT->Register(ROTFLAGS_REGISTRATIONKEEPSALIVE,m_pGraph,pM,&m_dwGraphRegister);
- pM.Release();
-
- return false;
- }
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