failed to take a snapshot on the video.

Question

BOOL CCaptureClass::Picture(CString fileName)
{
 if ( m_pBV )
 {
  long bitmapSize = 0;
  if ( SUCCEEDED(m_pBV->GetCurrentImage(&bitmapSize,0)))
  {
   bool pass =false;
   unsigned char * buffer=new unsigned char[bitmapSize];
   HRESULT  hr = m_pBV->GetCurrentImage(&bitmapSize,(long*)buffer); // hr's value is E_UNEXPECTED
   if ( SUCCEEDED(hr))
   {
    BITMAPFILEHEADER hdr;
    LPBITMAPINFOHEADER lpbi;
    lpbi = (LPBITMAPINFOHEADER)buffer;
    int nColors = 0;
    if (lpbi->biBitCount < 8)
    {
     nColors = 1 << lpbi->biBitCount;
    }
    hdr.bfType=((WORD)('M'<<8) | 'B');
    hdr.bfSize=bitmapSize + sizeof(hdr);
    hdr.bfReserved1=0;
    hdr.bfReserved2=0;
    hdr.bfOffBits = (DWORD)(sizeof(BITMAPFILEHEADER)+lpbi->biSize+nColors*sizeof(RGBQUAD));
    CFile bitmapFile(fileName,CFile::modeWrite|CFile::modeCreate|CFile::typeBinary);
    bitmapFile.Write(&hdr,sizeof(BITMAPFILEHEADER));
    bitmapFile.Write(buffer,bitmapSize);
    bitmapFile.Close();
    pass = true;
   }
   delete [] buffer;
   return pass;
  } 
 }
 return false;

}

 
HRESULT CCaptureClass::InitCaptureGraphBuilder()
{
 HRESULT hr;
 hr = CoCreateInstance(CLSID_FilterGraph,NULL,CLSCTX_INPROC_SERVER,IID_IGraphBuilder,(void**)&m_pGB);
 
 if ( FAILED(hr) ) return hr;

 hr = CoCreateInstance(CLSID_CaptureGraphBuilder2,NULL,CLSCTX_INPROC,IID_ICaptureGraphBuilder2,(void**)&m_pCapture);
 if ( FAILED(hr) ) return hr;
 m_pCapture->SetFiltergraph(m_pGB);

 hr = m_pGB->QueryInterface(IID_IMediaControl,(void**)&m_pMC);
 if ( FAILED(hr) ) return hr;

 hr = m_pGB->QueryInterface(IID_IVideoWindow,(LPVOID*)&m_pVW);
 if ( FAILED(hr) ) return hr;

 hr = m_pGB->QueryInterface(IID_IBasicVideo, (void**)&m_pBV);

 return hr;
}

You can download the compressed file of the project: http://www.yanglihao.com/filesUploaded/videoCapture.rar
Thank you.

Answer 1

If you have a failure there, then perhaps you have an error code. What is it?

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http://alax.info/blog/tag/directshow

Answer 2

I don't find the error code yet.  I know that the firs code of "m_pBV->GetCurrentImage(&bitmapSize,0)" returns "S_OK".
 Is there a function like GetLastError() that can let me get the Error Code.

Answer 3

"hr" is already an error code, you don't need a function for that.

---

http://alax.info/blog/tag/directshow