一段源代码，运行出错，大虾们帮忙看看

[SuperBC]

WCHAR wFile[MAX_PATH];
MultiByteToWideChar( CP_ACP, 0, m_FilePath, -1, wFile, MAX_PATH );

// Create the graph builder
CComPtr<IGraphBuilder> pGraphBuilder;
HRESULT hr = ::CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,
IID_IGraphBuilder, (void**)&pGraphBuilder);
if (FAILED(hr))
return hr;
ASSERT(pGraphBuilder != NULL);

// Create the "Grabber filter"
CComPtr<IBaseFilter> pGrabberBaseFilter;
CComPtr<ISampleGrabber> pSampleGrabber;
AM_MEDIA_TYPE mt;
hr = ::CoCreateInstance(CLSID_SampleGrabber, NULL, CLSCTX_INPROC_SERVER,
IID_IBaseFilter, (LPVOID *)&pGrabberBaseFilter);
if (FAILED(hr))
return hr;
pGrabberBaseFilter->QueryInterface(IID_ISampleGrabber, (void**)&pSampleGrabber);
if (pSampleGrabber == NULL)
return E_NOINTERFACE;
hr = pGraphBuilder->AddFilter(pGrabberBaseFilter,L"Grabber");
if (FAILED(hr))
return hr;

ZeroMemory(&mt, sizeof(AM_MEDIA_TYPE));
mt.majortype = MEDIATYPE_Video;

HDC hdc = ::GetDC(NULL);
int iBitDepth = GetDeviceCaps(hdc, BITSPIXEL);
::ReleaseDC(NULL, hdc);
switch (iBitDepth)
{
case 8:
mt.subtype = MEDIASUBTYPE_RGB8;
break;
case 16:
mt.subtype = MEDIASUBTYPE_RGB555;
break;
case 24:
mt.subtype = MEDIASUBTYPE_RGB24;
break;
case 32:
mt.subtype = MEDIASUBTYPE_RGB32;
break;
default:
return E_FAIL;
}

mt.formattype = FORMAT_VideoInfo;
hr = pSampleGrabber->SetMediaType(&mt);
if (FAILED(hr))
return hr;
hr = pGraphBuilder->RenderFile(wFile,NULL);
if (FAILED(hr))
return hr;

CComPtr<IMediaControl> pMediaControl;
CComPtr<IMediaEvent> pMediaEventEx;
// QueryInterface for some basic interfaces
pGraphBuilder->QueryInterface(IID_IMediaControl, (void **)&pMediaControl);
pGraphBuilder->QueryInterface(IID_IMediaEvent, (void **)&pMediaEventEx);

if (pMediaControl == NULL || pMediaEventEx == NULL)
return E_NOINTERFACE;

// Set up one-shot mode.
hr = pSampleGrabber->SetBufferSamples(TRUE);
if (FAILED(hr))
return hr;

hr = pSampleGrabber->SetOneShot(TRUE);
if (FAILED(hr))
return hr;

CComQIPtr<IMediaSeeking> pSeek = pMediaControl;
if (pSeek == NULL)
return E_NOINTERFACE;
LONGLONG Duration;
hr = pSeek->GetDuration(&Duration);
if (FAILED(hr))
return hr;
int NumSecs = int(Duration/10000000);

REFERENCE_TIME rtStart = 1 * 10000000;
if (NumSecs < 1)
rtStart = 0;
REFERENCE_TIME rtStop = rtStart;

hr = pSeek->SetPositions(&rtStart, AM_SEEKING_AbsolutePositioning,
&rtStop, AM_SEEKING_AbsolutePositioning);
if (FAILED(hr))
return hr;

CComQIPtr<IVideoWindow> pVideoWindow = pGraphBuilder;

hr = pVideoWindow->put_AutoShow(OAFALSE);
if (FAILED(hr))
return hr;

// Run the graph and wait for completion.
hr = pMediaControl->Run();
if (FAILED(hr))
return hr;

long evCode;
hr = pMediaEventEx->WaitForCompletion(INFINITE, &evCode);
if (FAILED(hr))
return hr;

AM_MEDIA_TYPE MediaType;
//ZeroMemory(&MediaType,sizeof(MediaType));
//pSampleGrabber->FreeMediaType(MediaType);
memset(&MediaType, 0, sizeof(MediaType));

//*******每运行这就返回失败**********
hr = pSampleGrabber->GetConnectedMediaType(&MediaType);
if (FAILED(hr))
return hr;

// Get a pointer to the video header.
VIDEOINFOHEADER *pVideoHeader = (VIDEOINFOHEADER*)MediaType.pbFormat;
if (pVideoHeader == NULL)
return E_FAIL;

// The video header contains the bitmap information.
// Copy it into a BITMAPINFO structure.
BITMAPINFO BitmapInfo;
ZeroMemory(&BitmapInfo, sizeof(BitmapInfo));
CopyMemory(&BitmapInfo.bmiHeader, &(pVideoHeader->bmiHeader), sizeof(BITMAPINFOHEADER));

// Create a DIB from the bitmap header, and get a pointer to the buffer.
void *buffer = NULL;
HBITMAP hBitmap = ::CreateDIBSection(0, &BitmapInfo, DIB_RGB_COLORS, &buffer, NULL, 0);
GdiFlush();
// Copy the image into the buffer.
long size = 0;
hr = pSampleGrabber->GetCurrentBuffer(&size, (long *)buffer);
if (FAILED(hr))
return hr;
long Width = pVideoHeader->bmiHeader.biWidth;
long Height = pVideoHeader->bmiHeader.biHeight;

HBITMAP hOldBitmap = m_Image.SetBitmap(hBitmap);
if (hOldBitmap != NULL)
::DeleteObject(hOldBitmap);

return S_OK;

[SuperBC]

以上程序是用来通过grabber来从流媒体中捕获视频frame的，大虾帮看看为什么得不到视频类型。