how to get a clips from a video file?

[xliu2019]

这是我写的一段code，想实现从视频文件中提取一段出来的功能，
我建立的graph 是
source--->grabber--->writer

可是程序运行的时候，在连接videoout和writein两个pin的时候出错
HRESULT hr;
REFERENCE_TIME rtNow=10000000, rtStop=1000000000;
CoInitialize(NULL);

USES_CONVERSION;
CString m_szInputFile = "E:\\Video\\video\\19.mpg";
TCHAR * tFilename = m_szInputFile.GetBuffer(MAX_PATH);
WCHAR * wFilename = T2W(tFilename);

CComPtr< IGraphBuilder > pGraph;
pGraph.CoCreateInstance(CLSID_FilterGraph);
if(!pGraph)
{
AfxMessageBox(TEXT("Could not create a graph"));
return;
}
// create a CaptureGraphBuilder to help connect filters
CComPtr< ICaptureGraphBuilder > pBuilder;
pBuilder.CoCreateInstance(CLSID_CaptureGraphBuilder);
// tell the capture graph builder what graph we're using
hr = pBuilder->SetFiltergraph(pGraph);
if(FAILED(hr))
{
AfxMessageBox(TEXT("Could not setup capture graph"));
return;
}
// ask directshow to add the appropriate source filter for the given file
CComPtr< IBaseFilter > pSourceBase;
hr = pGraph->AddSourceFilter(wFilename, L"Source", &pSourceBase);
if(!pSourceBase)
{
AfxMessageBox(TEXT("Could not load source filter for file"));
return;
}
CComPtr< IBaseFilter > pVideoFilter;
pVideoFilter.CoCreateInstance(CLSID_SampleGrabber);
hr = pGraph->AddFilter(pVideoFilter, L"VideoGrabber");

CComPtr<IBaseFilter> pFileWriter;
hr = pFileWriter.CoCreateInstance(CLSID_FileWriter);
hr = pGraph->AddFilter(pFileWriter,L"File Writer");
//// Set File name in File Writer filter
CComPtr <IFileSinkFilter> pfsink;
hr = pFileWriter->QueryInterface(IID_IFileSinkFilter,(void**)&pfsink);
hr = pfsink->SetFileName(L"C:\\test.mpg"/*A2COLE(m_avi)*/,NULL);

CComPtr<IPin> pSourcePin = GetOutPin(pSourceBase, 0);
CComPtr<IPin> pVideoIn = GetInPin (pVideoFilter, 0);
CComPtr<IPin> pVideoOut = GetOutPin(pVideoFilter, 0);
CComPtr<IPin> pWriteIn = GetInPin(pFileWriter, 0);

hr = pGraph->Connect(pSourcePin,pVideoIn);
if(FAILED(hr))
{
AfxMessageBox(TEXT("Cannot connect up video chain:1"));
return;
}
hr = pGraph->Connect(pVideoOut,pWriteIn);
if(FAILED(hr))
{
AfxMessageBox(TEXT("Cannot connect up video chain:2"));
return;
}
CComQIPtr< IMediaControl, &IID_IMediaControl > pControl(pGraph);
CComQIPtr< IMediaSeeking, &IID_IMediaSeeking > pSeeking(pGraph);
CComQIPtr< IMediaEvent, &IID_IMediaEvent > pEvent(pGraph);

hr = pSeeking->SetPositions( &rtNow,
AM_SEEKING_AbsolutePositioning,
&rtStop,
AM_SEEKING_AbsolutePositioning );
// Run the graph.
hr = pControl->Run();

// Wait for completion.
long evCode;
hr = pEvent->WaitForCompletion(INFINITE, &evCode);
pControl->Stop();
// Clean up.
CoUninitialize();

请各位指点一下，另外，我的这段代码，能实现提取一段视频的功能吗？

[systemthink]

视频是什么格式的呀?
去codeproject上找一哈,有例子的,很不错