写的DirectShow视频预览的程序不能预览

Question

RT，编译没有错，但是就是运行后没有图像，不知道为什么，好纠结啊，本来是用VFW做的，但是现在VFW刷新率什么的很多问题，还有不支持1394采集卡，不得已就换了DS，初学这个，头都大了，什么filter和filter graph都是一知半解，但是还是硬着头皮写了个预览的，结果打击死了，麻烦各位大大帮帮我，谢谢了。
class CPreviewDlg : public CDialog
{
// Construction
public:
CPreviewDlg(CWnd* pParent = NULL); // standard constructor IMediaControl     *pMediaControl ;         //媒体控制
IGraphBuilder     *pGraph;                 //过滤图表
IBaseFilter       *pSrc,*pPreview;         //过滤器
IMoniker          *pMoniker;               //监视器 IPin* FindPin(IBaseFilter *pFilter, PIN_DIRECTION dir);
[
BOOL CPreviewDlg::OnInitDialog()
{
CDialog::OnInitDialog(); // Add "About..." menu item to system menu. // IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000); CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
} // Set the icon for this dialog.  The framework does this automatically
//  when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon

// TODO: Add extra initialization here

ICaptureGraphBuilder2 * pBuilder = NULL;
pGraph = NULL;
pMediaControl = NULL;
//枚举视频设备
ICreateDevEnum *pDevEnum = NULL;
CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC, 
IID_ICreateDevEnum, (void **)&pDevEnum);
IEnumMoniker *pClassEnum = NULL; pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pClassEnum, 0);
ULONG cFetched;
if (pClassEnum->Next(1, &pMoniker, &cFetched) == S_OK)     
{
pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pSrc);
pMoniker->Release(); 
}
pClassEnum->Release(); CoCreateInstance(CLSID_CaptureGraphBuilder2,0,CLSCTX_INPROC_SERVER,IID_ICaptureGraphBuilder2,(void**)&pBuilder);
CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, 
IID_IGraphBuilder, (void **)&pGraph); pBuilder->SetFiltergraph(pGraph);
pGraph->QueryInterface(IID_IMediaControl,(void**)&pMediaControl);
pGraph->AddFilter(pSrc,L"avi"); pPreview = NULL; CoCreateInstance(CLSID_VideoRenderer,0,CLSCTX_ALL,IID_IBaseFilter,(void**)&pPreview);
if (pPreview != NULL)
{
pGraph->AddFilter(pPreview,L"preview");
//连接引脚
IPin * pSourceOut;
pSourceOut = FindPin(pSrc,PINDIR_OUTPUT);
IPin*  pPreIn = FindPin(pPreview,PINDIR_INPUT);
pGraph->ConnectDirect(pSourceOut,pPreIn,NULL); //获取预览窗口
IVideoWindow * pViewWnd= NULL;
pPreview->QueryInterface(IID_IVideoWindow,(void**)&pViewWnd);

if (pViewWnd)
{
//设置预览窗口的拥有者
pViewWnd->put_Owner((long)m_hWnd);
pViewWnd->put_Left(1);
pViewWnd->put_Top(1); //获取预览窗口风格
long style;
pViewWnd->get_WindowStyle(&style);
style = style & ~WS_CAPTION;
style = style & ~WS_DLGFRAME;
style = style & WS_CHILD;
pViewWnd->put_WindowStyle(style); //设置预览窗口宽度和高度
CWnd* pwnd = GetDlgItem(IDC_Video);
CRect rc;
pwnd->GetClientRect(&rc);
pViewWnd->put_Height(rc.Height()-60);
pViewWnd->put_Width(rc.Width()-2);
}
pMediaControl->Run();
}
return TRUE;  // return TRUE  unless you set the focus to a control
}
/code][code=C/C++]
//查找引脚
IPin* CPreviewDlg::FindPin(IBaseFilter *pFilter, PIN_DIRECTION dir)
{
IEnumPins* pEnumPins;
IPin* pOutpin;
PIN_DIRECTION pDir;
pFilter->EnumPins(&pEnumPins); while (pEnumPins->Next(1,&pOutpin,NULL)==S_OK)
{
pOutpin->QueryDirection(&pDir);
if (pDir==dir)
{
return pOutpin;
}
}
return 0;
}
所有代码都在上面了，实在不知道哪出错了导致不能运行，摆脱各位了

Answer 1

class CPreviewDlg : public CDialog
{
// Construction
public:
    CPreviewDlg(CWnd* pParent = NULL);    // standard constructor    IMediaControl     *pMediaControl ;         //媒体控制
    IGraphBuilder     *pGraph;                 //过滤图表
    IBaseFilter       *pSrc,*pPreview;         //过滤器
    IMoniker          *pMoniker;               //监视器    IPin* FindPin(IBaseFilter *pFilter, PIN_DIRECTION dir);[
BOOL CPreviewDlg::OnInitDialog()
{
    CDialog::OnInitDialog();    // Add "About..." menu item to system menu.    // IDM_ABOUTBOX must be in the system command range.
    ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
    ASSERT(IDM_ABOUTBOX < 0xF000);    CMenu* pSysMenu = GetSystemMenu(FALSE);
    if (pSysMenu != NULL)
    {
        CString strAboutMenu;
        strAboutMenu.LoadString(IDS_ABOUTBOX);
        if (!strAboutMenu.IsEmpty())
        {
            pSysMenu->AppendMenu(MF_SEPARATOR);
            pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
        }
    }    // Set the icon for this dialog.  The framework does this automatically
    //  when the application's main window is not a dialog
    SetIcon(m_hIcon, TRUE);            // Set big icon
    SetIcon(m_hIcon, FALSE);        // Set small icon
    
    // TODO: Add extra initialization here
    
    ICaptureGraphBuilder2 * pBuilder = NULL;
    pGraph = NULL;
    pMediaControl = NULL;
    //枚举视频设备
    ICreateDevEnum *pDevEnum = NULL;
    CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC, 
        IID_ICreateDevEnum, (void **)&pDevEnum);
    IEnumMoniker *pClassEnum = NULL;    pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pClassEnum, 0);
    ULONG cFetched;
    if (pClassEnum->Next(1, &pMoniker, &cFetched) == S_OK)     
    {
        pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pSrc);
        pMoniker->Release(); 
    }
    pClassEnum->Release();    CoCreateInstance(CLSID_CaptureGraphBuilder2,0,CLSCTX_INPROC_SERVER,IID_ICaptureGraphBuilder2,(void**)&pBuilder);
    CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, 
                        IID_IGraphBuilder, (void **)&pGraph);    pBuilder->SetFiltergraph(pGraph);
    pGraph->QueryInterface(IID_IMediaControl,(void**)&pMediaControl);
    pGraph->AddFilter(pSrc,L"avi");    pPreview = NULL;    CoCreateInstance(CLSID_VideoRenderer,0,CLSCTX_ALL,IID_IBaseFilter,(void**)&pPreview);
    if (pPreview != NULL)
    {
        pGraph->AddFilter(pPreview,L"preview");
        //连接引脚
        IPin * pSourceOut;
        pSourceOut = FindPin(pSrc,PINDIR_OUTPUT);
        IPin*  pPreIn = FindPin(pPreview,PINDIR_INPUT);
        pGraph->ConnectDirect(pSourceOut,pPreIn,NULL);        //获取预览窗口
        IVideoWindow * pViewWnd= NULL;
        pPreview->QueryInterface(IID_IVideoWindow,(void**)&pViewWnd);
        
        if (pViewWnd)
        {
            //设置预览窗口的拥有者
            pViewWnd->put_Owner((long)m_hWnd);
            pViewWnd->put_Left(1);
            pViewWnd->put_Top(1);            //获取预览窗口风格
            long style;
            pViewWnd->get_WindowStyle(&style);
            style = style & ~WS_CAPTION;
            style = style & ~WS_DLGFRAME;
            style = style & WS_CHILD;
            pViewWnd->put_WindowStyle(style);            //设置预览窗口宽度和高度
            CWnd* pwnd = GetDlgItem(IDC_Video);
            CRect rc;
            pwnd->GetClientRect(&rc);
            pViewWnd->put_Height(rc.Height()-60);
            pViewWnd->put_Width(rc.Width()-2);
        }
        pMediaControl->Run();
    }
    return TRUE;  // return TRUE  unless you set the focus to a control
}
/code][code=C/C++]
//查找引脚
IPin* CPreviewDlg::FindPin(IBaseFilter *pFilter, PIN_DIRECTION dir)
{
    IEnumPins* pEnumPins;
    IPin* pOutpin;
    PIN_DIRECTION pDir;
    pFilter->EnumPins(&pEnumPins);    while (pEnumPins->Next(1,&pOutpin,NULL)==S_OK)
    {
        pOutpin->QueryDirection(&pDir);
        if (pDir==dir)
        {
            return pOutpin;
        }
    }
    return 0;
}
你看下，我改的