这是什么错误？答对者马上给分！

Question

IVideoWindow 的GUID 没有被初始化，maybe

Answer 1

DWORD_PTR 是那里定义的啊？

Answer 2

还是检查一下程序吧.
我给一个例子:
#include <windows.h>
#include <dshow.h>#define CLASSNAME "VideoWindow"IGraphBuilder   *pGraph = NULL;
IMediaControl   *pMediaControl = NULL;
IVideoWindow    *pVidWin;// = NULL;
HWND            g_hwnd;void PlayFile(void)
{
    // Create the filter graph manager.
    CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC, 
        IID_IGraphBuilder, (void **)&pGraph);
    pGraph->QueryInterface(IID_IMediaControl, (void **)&pMediaControl);
    pGraph->QueryInterface(IID_IVideoWindow, (void **)&pVidWin);    // Build the graph. 
    pGraph->RenderFile(L"G:\\share\\clock.mpg", NULL);    //Set the video window.
    pVidWin->put_Owner((OAHWND)g_hwnd);
    pVidWin->put_WindowStyle(WS_CHILD | WS_CLIPSIBLINGS);    RECT grc;
    GetClientRect(g_hwnd, &grc);
    pVidWin->SetWindowPosition(0, 0, grc.right, grc.bottom);    // Run the graph.
    pMediaControl->Run();
}void CleanUp(void)
{
    pVidWin->put_Visible(OAFALSE);
    pVidWin->put_Owner(NULL);   
    pMediaControl->Release();
    pVidWin->Release();
    pGraph->Release();
}// Message handler.
long FAR PASCAL WindowProc( HWND hwnd, UINT msg, UINT wParam, LONG lParam)
{
    switch (msg)
    {
        case WM_DESTROY:
            CleanUp();
            PostQuitMessage(0);
            break;
        default:
            return (DefWindowProc(hwnd, msg, wParam, lParam));
    }
    return(NULL);
}// Main.
int PASCAL WinMain( HINSTANCE hInst, HINSTANCE hPrevInst, LPSTR  lpCmdLine, 
    int nCmdShow )
{
    MSG         msg;
    WNDCLASS    wc;    CoInitialize(NULL);    ZeroMemory(&wc, sizeof wc);
    wc.lpfnWndProc  = WindowProc;
    wc.hInstance    = hInst;
    wc.hIcon        = LoadIcon( NULL, IDI_APPLICATION );
    wc.hCursor      = LoadCursor( NULL, IDC_ARROW );
    wc.hbrBackground = (HBRUSH)GetStockObject( BLACK_BRUSH );
    wc.lpszMenuName = NULL;
    wc.lpszClassName = CLASSNAME;
    RegisterClass( &wc );    g_hwnd = CreateWindow(
        CLASSNAME,
        "DirectShow Sample",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInst,
        NULL);    ShowWindow( g_hwnd, nCmdShow );
    UpdateWindow( g_hwnd );
    PlayFile();    while( GetMessage( &msg, NULL, 0, 0 ) )
    {
        TranslateMessage( &msg );
        DispatchMessage( &msg );
    }    CoUninitialize();
    return msg.wParam;
}