DirectShow的有关问题

void CVideoView::OnPlay()
{
    // TODO: 在此添加命令处理程序代码


    IGraphBuilder *pGraph = NULL;  
    IMediaControl *pControl = NULL;  
    IMediaEvent   *pEvent = NULL;  

    // Initialize the COM library.  
    HRESULT hr = CoInitialize(NULL);  
    if (FAILED(hr))  
    {  
        printf("ERROR - Could not initialize COM library");  
        return;  
    }  

    // Create the filter graph manager and query for interfaces.  
    hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,   
        IID_IGraphBuilder, (void **)&pGraph);  
    if (FAILED(hr))  
    {  
        printf("ERROR - Could not create the Filter Graph Manager.");  
        return;  
    }  

    hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl);  
    hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);  

    IVideoWindow* pWnd = NULL;  
    hr = pGraph->QueryInterface(IID_IVideoWindow,(void**)&pWnd);  
    hr = pWnd->put_Owner((OAHWND)m_hWnd);  
    pWnd->put_WindowStyle(WS_CHILD | WS_CLIPSIBLINGS);  

    CRect rc;  
    GetClientRect(&rc);  
    pWnd->SetWindowPosition(rc.left,rc.top,rc.Width(),rc.Height());  

    // Build the graph. IMPORTANT: Change this string to a file on your system.  
    hr = pGraph->RenderFile(L"E://111.avi", NULL);  
    if (SUCCEEDED(hr))  
    {  
        // Run the graph.  
        hr = pControl->Run();  
        if (SUCCEEDED(hr))  
        {  
            // Wait for completion.  
            long evCode;  
        //    pEvent->WaitForCompletion(INFINITE, &evCode);  

                    }  
    }  
    pControl->Release();  
    pEvent->Release();  
    pGraph->Release();  
    CoUninitialize();  

}